qid int64 1 74.7M | question stringlengths 12 33.8k | date stringlengths 10 10 | metadata list | response_j stringlengths 0 115k | response_k stringlengths 2 98.3k |
|---|---|---|---|---|---|
779,642 | We had a file in our repository that we deleted several revisions ago. How do we get it back using TortoiseSVN without reverting our entire repository? | 2009/04/22 | [
"https://Stackoverflow.com/questions/779642",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/72631/"
] | In the repo browser, there is a menu that says some to the effect of goto version. From here you can browse the field that was available in that revision and drag and drop the file out. i would check the actual program bur I'm currently on my phone.
Hope this helps | use revert option or open cmd window and type :
(give the local path where you've checkout your code) svn -r (type revision no. before deleting that path) |
779,642 | We had a file in our repository that we deleted several revisions ago. How do we get it back using TortoiseSVN without reverting our entire repository? | 2009/04/22 | [
"https://Stackoverflow.com/questions/779642",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/72631/"
] | The other answers appear to focus on restoring an entire *revision* (using a different location), so here's how to only restore a single file, without having to check out an entire revision, using TortoiseSVN:
1. Open the revision log for the revision that deleted the file.
2. Find the file in the changelist.
3. Right-click the file and select "Revert changes from this revision...". Answer yes.
The file is restored and re-added to the repository. I am not 100% certain if Subversion will treat it as a different file, or as a new revision of the file. | Once you know the revision number where the file was deleted (using the repository browser is probably the easiest way to find this). Do a check out to a new location before that revision. |
779,642 | We had a file in our repository that we deleted several revisions ago. How do we get it back using TortoiseSVN without reverting our entire repository? | 2009/04/22 | [
"https://Stackoverflow.com/questions/779642",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/72631/"
] | Go to the Show Log screen, and search for the revision when the file was deleted, then right click the file and select **Save revision to...**
 | Once you know the revision number where the file was deleted (using the repository browser is probably the easiest way to find this). Do a check out to a new location before that revision. |
779,642 | We had a file in our repository that we deleted several revisions ago. How do we get it back using TortoiseSVN without reverting our entire repository? | 2009/04/22 | [
"https://Stackoverflow.com/questions/779642",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/72631/"
] | Go to the Show Log screen, and search for the revision when the file was deleted, then right click the file and select **Save revision to...**
 | The other answers appear to focus on restoring an entire *revision* (using a different location), so here's how to only restore a single file, without having to check out an entire revision, using TortoiseSVN:
1. Open the revision log for the revision that deleted the file.
2. Find the file in the changelist.
3. Right-click the file and select "Revert changes from this revision...". Answer yes.
The file is restored and re-added to the repository. I am not 100% certain if Subversion will treat it as a different file, or as a new revision of the file. |
779,642 | We had a file in our repository that we deleted several revisions ago. How do we get it back using TortoiseSVN without reverting our entire repository? | 2009/04/22 | [
"https://Stackoverflow.com/questions/779642",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/72631/"
] | The other answers appear to focus on restoring an entire *revision* (using a different location), so here's how to only restore a single file, without having to check out an entire revision, using TortoiseSVN:
1. Open the revision log for the revision that deleted the file.
2. Find the file in the changelist.
3. Right-click the file and select "Revert changes from this revision...". Answer yes.
The file is restored and re-added to the repository. I am not 100% certain if Subversion will treat it as a different file, or as a new revision of the file. | use revert option or open cmd window and type :
(give the local path where you've checkout your code) svn -r (type revision no. before deleting that path) |
779,642 | We had a file in our repository that we deleted several revisions ago. How do we get it back using TortoiseSVN without reverting our entire repository? | 2009/04/22 | [
"https://Stackoverflow.com/questions/779642",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/72631/"
] | Go to the Show Log screen, and search for the revision when the file was deleted, then right click the file and select **Save revision to...**
 | use revert option or open cmd window and type :
(give the local path where you've checkout your code) svn -r (type revision no. before deleting that path) |
41,252,648 | I have two values extracted from a select query on a MySQL database. The first contains the property name and the second contains the value for the property.
Is there a way using a parameter to assign the value to the name in the first field i.e. Something like
SET name in row.Property\_Name=row.Property\_Value | 2016/12/20 | [
"https://Stackoverflow.com/questions/41252648",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/5206736/"
] | Please [this (long) thread at the repo](https://github.com/eddelbuettel/rquantlib/issues/80) as well as the resulting [wiki entry](https://github.com/eddelbuettel/rquantlib/wiki/RQuantLib).
As the (co-)author/maintainer I don't have an OS X machine, and for me things simply just work on Linux ... Documentation for installation on other OSs has to be user-contributed, and luckily we have some. | Solution (thanks to clues from Dirk, the package co-author, above) came from [this wiki entry he mentioned](https://github.com/eddelbuettel/rquantlib/issues/80), in particular requiring the editing of a .hpp file as detailed on [this github edit](https://github.com/lballabio/QuantLib/pull/161/files), which will seemingly be fixed on its own once they push quantlib v 1.9.1 |
7,921 | This is a question about "Personal investing and asset allocation".
About me:
* I earn more than I spend
* I may retire in 15 or 20 years, and I have savings to be invested in something or managed somehow until then
* I'm a computer programmer with a Math degree, but I'm not a finance professional/expert
In the past, people have encouraged me to invest in 'mutual funds', and I haven't been impressed with the result: I was invested during the dot-com crash, and again during the downturn of a year or two ago, and found that the supposedly 'managed' mutual funds still lose value during a down-turn (which is disappointing) and also don't go up as much as the ordinary stock market index during an upturn (also disappointing).
So I was wondering about something different: index funds, instead of mutual funds. Preferably low-cost, and diversified; and possibly small-cap, if those have a better-than-average yield.
Is something like the "The Über–Tuber" listed at the bottom of <http://canadiancouchpotato.com/model-portfolios/> a sensible investment choice for me? What should I beware of, and what's the disadvantage of that as a strategy? | 2011/04/24 | [
"https://money.stackexchange.com/questions/7921",
"https://money.stackexchange.com",
"https://money.stackexchange.com/users/3443/"
] | I think you're on the right track with that strategy. If you want to learn more about this strategy, I'd recommend "The Intelligent Asset Allocator" by William Bernstein.
As for the Über–Tuber portfolio you linked to, my only concern would be that it is diversified in everything except for the short-term bond component, which is 40%. It might be worth looking at some portfolios that have more than one bond allocation -- possibly diversifying more across corporate vs government, and intermediate vs short term. Even the Cheapskate's portfolio located immediately above the Über–Tuber has 20% Corporate and 20% Government.
Also note that they mention:
>
> Because it includes so many funds, it would be expensive and unwieldy for an account less than $100,000.
>
>
>
Regarding your question about the disadvantages of an index-fund-based asset allocation strategy:
* It requires discipline to execute. If you let your actual allocation stray too far from the target allocation, you don't get all of the advantages of diversification.
* If you select the wrong allocation you can end up with poor performance. As a rough general rule, the more poorly correlated assets you assemble into your portfolio, the lower risk you can expect for a given expected return.
* Discipline again: if one of your assets takes a dive and you panic, sell, and let the money sit in cash, then you lose out on gains when that asset recovers in price. It takes experience and discipline to be able to buy stocks during times like November 2008 or October 2001. | You can simply stick with some index funds that tracks the S&P 500 and Ex-US world market. That should provide some good diversification. And of course, you should always have a portion of your money in short/mid term bond fund, rebalancing your stock/bond ratio all the way as deemed necessary.
If you want to follow the The Über–Tuber portfolio, you'd better make sure that there's minimum overlapping among the underlying shares that they hold. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | During your action
==================
The simplest reading of the [spell text](https://www.dndbeyond.com/spells/time-stop), is that you take the extra turns as part of the action which is casting the spell, similar to what you would do if you cast any other instantaneous spell. This means that once you are done taking those turns, you are simply done taking that action and you may continue with the rest of your normal turn. | I would say scenario 2 is correct.
----------------------------------
There is nothing in the spell’s description that would suggest it ends your turn as soon as you cast it, simply that it uses up your action. I would say you still have the rest of your turn to use up your bonus action, movement, reaction, etc before the turns from *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* are used up. So a process would look like this:
You cast *Time Stop* using your action, you can finish your current turn (using up any remaining actions, bonus actions, reactions, movement etc) and when the player says they are finished with their turn, you move onto using up the turns granted by *Time Stop*.
Additionally, as the spell is instantaneous, it would make sense that its effects come into force instantaneously. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | During your action
==================
The simplest reading of the [spell text](https://www.dndbeyond.com/spells/time-stop), is that you take the extra turns as part of the action which is casting the spell, similar to what you would do if you cast any other instantaneous spell. This means that once you are done taking those turns, you are simply done taking that action and you may continue with the rest of your normal turn. | *Time Stop* only starts after your current turn has ended
---------------------------------------------------------
Whilst my other answer is how I would rule it, and how I believe many other people would rule it, here is what the spell description of *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says:
>
> You briefly stop the flow of time for everyone but yourself. No time passes for other creatures, while **you take 1d4 + 1 turns in a row, during which you can use actions and move as normal.**
>
>
>
The description would suggest that only turns granted by *Time Stop* have time stopped for them. A strict Rules as Written approach might say that, because you are not using up the turns granted by *Time Stop*, you are using your regular turn, time does not stop when the spell is cast. Time only stops when you end your current turn and start using up the turns granted by the spell.
Alternatively, if you were to include your current turn as one of your time stopped turns, it would be like Scenario 2 but you have used up one of your 1d4+1 turns. (Its possible that this is why it is 1d4 +1 and not just 1d4 - if you rolled a 1 on the d4, you would only stop time for your current turn, where you have already used up your action to cast *Time Stop*, making it a waste of a spell slot and a turn).
---
I’m not sure how far I agree that this is the correct interpretation but, as it is possible that this is the correct way to rule it (as per the Rules as Written), I feel obligated to present this side of the argument. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | During your action
==================
The simplest reading of the [spell text](https://www.dndbeyond.com/spells/time-stop), is that you take the extra turns as part of the action which is casting the spell, similar to what you would do if you cast any other instantaneous spell. This means that once you are done taking those turns, you are simply done taking that action and you may continue with the rest of your normal turn. | Scenario 3
----------
[*Time stop*](https://www.dndbeyond.com/spells/time-stop) interrupts the Wizards turn, then his original turn continues after the spell ends.
Time stops duration is *instantaneous*, so it will occur during the wizards action. The spell effect is to allow the Wizard to take addition turns, but when the spell ends he should be able to continue his original turn normally as he would with any other spell.
An important point is that anything the wizard does after the spell ends is in normal time so other creatures could react. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | During your action
==================
The simplest reading of the [spell text](https://www.dndbeyond.com/spells/time-stop), is that you take the extra turns as part of the action which is casting the spell, similar to what you would do if you cast any other instantaneous spell. This means that once you are done taking those turns, you are simply done taking that action and you may continue with the rest of your normal turn. | Scenario 4
----------
The current turn is the first of the 1d4+1 turns. You therefore finish the current turn normally and then take 1d4 extra turns.
The spell description says you take 1d4+1 turns in a row, not 1d4+1 extra turns. Taking 1d4+1 turns after the current turn would actually be 1d4+2 turns in a row. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | Scenario 3
----------
[*Time stop*](https://www.dndbeyond.com/spells/time-stop) interrupts the Wizards turn, then his original turn continues after the spell ends.
Time stops duration is *instantaneous*, so it will occur during the wizards action. The spell effect is to allow the Wizard to take addition turns, but when the spell ends he should be able to continue his original turn normally as he would with any other spell.
An important point is that anything the wizard does after the spell ends is in normal time so other creatures could react. | I would say scenario 2 is correct.
----------------------------------
There is nothing in the spell’s description that would suggest it ends your turn as soon as you cast it, simply that it uses up your action. I would say you still have the rest of your turn to use up your bonus action, movement, reaction, etc before the turns from *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* are used up. So a process would look like this:
You cast *Time Stop* using your action, you can finish your current turn (using up any remaining actions, bonus actions, reactions, movement etc) and when the player says they are finished with their turn, you move onto using up the turns granted by *Time Stop*.
Additionally, as the spell is instantaneous, it would make sense that its effects come into force instantaneously. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | Scenario 4
----------
The current turn is the first of the 1d4+1 turns. You therefore finish the current turn normally and then take 1d4 extra turns.
The spell description says you take 1d4+1 turns in a row, not 1d4+1 extra turns. Taking 1d4+1 turns after the current turn would actually be 1d4+2 turns in a row. | I would say scenario 2 is correct.
----------------------------------
There is nothing in the spell’s description that would suggest it ends your turn as soon as you cast it, simply that it uses up your action. I would say you still have the rest of your turn to use up your bonus action, movement, reaction, etc before the turns from *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* are used up. So a process would look like this:
You cast *Time Stop* using your action, you can finish your current turn (using up any remaining actions, bonus actions, reactions, movement etc) and when the player says they are finished with their turn, you move onto using up the turns granted by *Time Stop*.
Additionally, as the spell is instantaneous, it would make sense that its effects come into force instantaneously. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | Scenario 3
----------
[*Time stop*](https://www.dndbeyond.com/spells/time-stop) interrupts the Wizards turn, then his original turn continues after the spell ends.
Time stops duration is *instantaneous*, so it will occur during the wizards action. The spell effect is to allow the Wizard to take addition turns, but when the spell ends he should be able to continue his original turn normally as he would with any other spell.
An important point is that anything the wizard does after the spell ends is in normal time so other creatures could react. | *Time Stop* only starts after your current turn has ended
---------------------------------------------------------
Whilst my other answer is how I would rule it, and how I believe many other people would rule it, here is what the spell description of *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says:
>
> You briefly stop the flow of time for everyone but yourself. No time passes for other creatures, while **you take 1d4 + 1 turns in a row, during which you can use actions and move as normal.**
>
>
>
The description would suggest that only turns granted by *Time Stop* have time stopped for them. A strict Rules as Written approach might say that, because you are not using up the turns granted by *Time Stop*, you are using your regular turn, time does not stop when the spell is cast. Time only stops when you end your current turn and start using up the turns granted by the spell.
Alternatively, if you were to include your current turn as one of your time stopped turns, it would be like Scenario 2 but you have used up one of your 1d4+1 turns. (Its possible that this is why it is 1d4 +1 and not just 1d4 - if you rolled a 1 on the d4, you would only stop time for your current turn, where you have already used up your action to cast *Time Stop*, making it a waste of a spell slot and a turn).
---
I’m not sure how far I agree that this is the correct interpretation but, as it is possible that this is the correct way to rule it (as per the Rules as Written), I feel obligated to present this side of the argument. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | Scenario 4
----------
The current turn is the first of the 1d4+1 turns. You therefore finish the current turn normally and then take 1d4 extra turns.
The spell description says you take 1d4+1 turns in a row, not 1d4+1 extra turns. Taking 1d4+1 turns after the current turn would actually be 1d4+2 turns in a row. | *Time Stop* only starts after your current turn has ended
---------------------------------------------------------
Whilst my other answer is how I would rule it, and how I believe many other people would rule it, here is what the spell description of *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says:
>
> You briefly stop the flow of time for everyone but yourself. No time passes for other creatures, while **you take 1d4 + 1 turns in a row, during which you can use actions and move as normal.**
>
>
>
The description would suggest that only turns granted by *Time Stop* have time stopped for them. A strict Rules as Written approach might say that, because you are not using up the turns granted by *Time Stop*, you are using your regular turn, time does not stop when the spell is cast. Time only stops when you end your current turn and start using up the turns granted by the spell.
Alternatively, if you were to include your current turn as one of your time stopped turns, it would be like Scenario 2 but you have used up one of your 1d4+1 turns. (Its possible that this is why it is 1d4 +1 and not just 1d4 - if you rolled a 1 on the d4, you would only stop time for your current turn, where you have already used up your action to cast *Time Stop*, making it a waste of a spell slot and a turn).
---
I’m not sure how far I agree that this is the correct interpretation but, as it is possible that this is the correct way to rule it (as per the Rules as Written), I feel obligated to present this side of the argument. |
162,031 | *[Time Stop](https://www.dndbeyond.com/spells/time-stop)* says "you take 1d4 + 1 turns in a row". My question is, when do the additional turns happen? Here are two scenarios I can think of.
### Scenario 1
The caster casts *Time Stop*. This immediately ends the caster's current turn and begins the first of the additional 1d4+1 turns. If this was the first action at the beginning of the caster's turn, he effectively loses any potential movement, bonus actions, or even additional actions (if he were hasted) on the turn he cast time stop.
### Scenario 2
The caster casts *Time Stop*, which immediately freezes all other creatures, but the caster can still complete his current turn and all associated actions. The first of the additional 1d4+1 turns begin after the current turn is complete. | 2019/12/29 | [
"https://rpg.stackexchange.com/questions/162031",
"https://rpg.stackexchange.com",
"https://rpg.stackexchange.com/users/61052/"
] | Scenario 3
----------
[*Time stop*](https://www.dndbeyond.com/spells/time-stop) interrupts the Wizards turn, then his original turn continues after the spell ends.
Time stops duration is *instantaneous*, so it will occur during the wizards action. The spell effect is to allow the Wizard to take addition turns, but when the spell ends he should be able to continue his original turn normally as he would with any other spell.
An important point is that anything the wizard does after the spell ends is in normal time so other creatures could react. | Scenario 4
----------
The current turn is the first of the 1d4+1 turns. You therefore finish the current turn normally and then take 1d4 extra turns.
The spell description says you take 1d4+1 turns in a row, not 1d4+1 extra turns. Taking 1d4+1 turns after the current turn would actually be 1d4+2 turns in a row. |
37,612 | If you use the optical viewfinder in a DSLR (Nikon D5100) camera, are you supposed to turn off the LCD screen (flip it in closed position)? | 2013/04/05 | [
"https://photo.stackexchange.com/questions/37612",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/19197/"
] | There's no reason you *have* to turn it off, but it can be less distracting and will save batteries. The discontinued D60 model used to turn off the rear panel when you held the camera to your eye, but the newer models don't have that.
Higher end models, like the D7100, have a separate small LCD panel on the top of the camera, which is useful for adjusting settings without needing the large back panel. Entry-level models usually forgo this to save space, cost, and complexity, and in exchange, the rear LCD is usually more important for finding out the status of the camera's various settings, or even for *setting* them. (The D5100 doesn't have a dedicated button for ISO, for example, or a switch for focus modes.)
A lot of information is available around the edges of the optical viewfinder too, but since the space is constrained the data there tends to be very terse. | I don't know Nikon's bodies very well, but there is no reason you should have to turn it off. It is worth noting that unless your camera body has a semi-transparent mirror, you will not be able to see the image through the viewfinder and the LCD at the same time. The image will either go to the sensor and then the LCD or a mirror will flip down and the image will be directed to the viewfinder.
You could still use it to display other information about what you are shooting or to have a quick review of the image though if it suits the way you want to work with it. You certainly don't have to have it on, but there shouldn't be any reason you can't use it however it will allow itself to be used while the mirror is down. |
37,612 | If you use the optical viewfinder in a DSLR (Nikon D5100) camera, are you supposed to turn off the LCD screen (flip it in closed position)? | 2013/04/05 | [
"https://photo.stackexchange.com/questions/37612",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/19197/"
] | There's no reason you *have* to turn it off, but it can be less distracting and will save batteries. The discontinued D60 model used to turn off the rear panel when you held the camera to your eye, but the newer models don't have that.
Higher end models, like the D7100, have a separate small LCD panel on the top of the camera, which is useful for adjusting settings without needing the large back panel. Entry-level models usually forgo this to save space, cost, and complexity, and in exchange, the rear LCD is usually more important for finding out the status of the camera's various settings, or even for *setting* them. (The D5100 doesn't have a dedicated button for ISO, for example, or a switch for focus modes.)
A lot of information is available around the edges of the optical viewfinder too, but since the space is constrained the data there tends to be very terse. | Once you start using a DSLR in a way that pushes its limits then you are **"supposed"** to use it in the manner that best suits and/or pleases **you**, and or that best enables you to achieve the maximum from the camera as determined solely by you, and/or that makes you maximally happy.
Some other people may have strong preferences as to how a camera should be used or set and will advise you if you ask them, or in enough cases, even if you don't.
Note how much you like or value what they achieve (noting that in some cases you will not initially have enough experience to know whether in time you will come to appreciate and value advice which initially seems pointless or wrong.)
Listen and act on their input (or not) accordingly.
Have fun.
ie, unlike dealing with people :-), you are master and decision maker of how the camera can and should be used and can use it in whatever way you wish. Be guided by those further along the road, but do not be dictated to. [Only follow this advice if you want to :-) ].
* Screen on: more power drain, more information, more visible to others, may cause exposure issues in some dark situations, ...
* Screen off" longer battery, turned in screen is more protected, MAY make some cameras more responsive in some cases, camera may not appear visibly on to others ...
I would usually uses screen on by default with cameras that I use as it usually maximises overall performance BUT will turn it off when the situation benefits from it. |
37,612 | If you use the optical viewfinder in a DSLR (Nikon D5100) camera, are you supposed to turn off the LCD screen (flip it in closed position)? | 2013/04/05 | [
"https://photo.stackexchange.com/questions/37612",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/19197/"
] | Once you start using a DSLR in a way that pushes its limits then you are **"supposed"** to use it in the manner that best suits and/or pleases **you**, and or that best enables you to achieve the maximum from the camera as determined solely by you, and/or that makes you maximally happy.
Some other people may have strong preferences as to how a camera should be used or set and will advise you if you ask them, or in enough cases, even if you don't.
Note how much you like or value what they achieve (noting that in some cases you will not initially have enough experience to know whether in time you will come to appreciate and value advice which initially seems pointless or wrong.)
Listen and act on their input (or not) accordingly.
Have fun.
ie, unlike dealing with people :-), you are master and decision maker of how the camera can and should be used and can use it in whatever way you wish. Be guided by those further along the road, but do not be dictated to. [Only follow this advice if you want to :-) ].
* Screen on: more power drain, more information, more visible to others, may cause exposure issues in some dark situations, ...
* Screen off" longer battery, turned in screen is more protected, MAY make some cameras more responsive in some cases, camera may not appear visibly on to others ...
I would usually uses screen on by default with cameras that I use as it usually maximises overall performance BUT will turn it off when the situation benefits from it. | I don't know Nikon's bodies very well, but there is no reason you should have to turn it off. It is worth noting that unless your camera body has a semi-transparent mirror, you will not be able to see the image through the viewfinder and the LCD at the same time. The image will either go to the sensor and then the LCD or a mirror will flip down and the image will be directed to the viewfinder.
You could still use it to display other information about what you are shooting or to have a quick review of the image though if it suits the way you want to work with it. You certainly don't have to have it on, but there shouldn't be any reason you can't use it however it will allow itself to be used while the mirror is down. |
20,718,848 | According to latest Apple's new [submission rules](http://techcrunch.com/2013/12/17/apple-requiring-all-app-submissions-to-be-optimized-for-ios-7-by-feb-1st/) apps which would have built with ios 6 sdk will be rejected after february 1st
But I can't make one thing clear : will Apple submit apps built with lates sdk 7.0 and deployment target set up to 6.0 after february 1st? | 2013/12/21 | [
"https://Stackoverflow.com/questions/20718848",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/1102197/"
] | <https://developer.apple.com/news/index.php?id=12172013a#top>
Your app should be optimized for iOS7 means you have to compile it with iOS 7 SDK as Base SDK. Yes they will accept app with Deployment Target 6.0 and even lower. | Yes. The SDK you're using and your deployment target are two different things. |
20,718,848 | According to latest Apple's new [submission rules](http://techcrunch.com/2013/12/17/apple-requiring-all-app-submissions-to-be-optimized-for-ios-7-by-feb-1st/) apps which would have built with ios 6 sdk will be rejected after february 1st
But I can't make one thing clear : will Apple submit apps built with lates sdk 7.0 and deployment target set up to 6.0 after february 1st? | 2013/12/21 | [
"https://Stackoverflow.com/questions/20718848",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/1102197/"
] | <https://developer.apple.com/news/index.php?id=12172013a#top>
Your app should be optimized for iOS7 means you have to compile it with iOS 7 SDK as Base SDK. Yes they will accept app with Deployment Target 6.0 and even lower. | Apple will review app that has base SDK iOS7.0, base SDK basically defines that you can use all the public API up to your base SDK.
while deployment target is minimum version you want to support, so you can set it what ever you want but base SDK should be iOS7. |
116,619 | I'm currently running the official nightly of cm12.1 on my LG G3 AT&T (model d850) with the Xposed Framework installed. However, every time I manual update Cyanogenmod (as I don't have a compatible recovery for automatic installation), the Xposed Framework gets removed/disabled, forcing me to locate the downloaded framework zip file (xposed manual installation because of reasons). This is not really a big issue for me and doesn't greatly affect myself or my phone in anyway but it will be glad if someone has found a 'possible' solution for this minor bug | 2015/07/29 | [
"https://android.stackexchange.com/questions/116619",
"https://android.stackexchange.com",
"https://android.stackexchange.com/users/118748/"
] | Ok so this isn't a bug but in the updater script of the xposed framework, a function called **install\_overwrite** is called upon several occasion and, hence the name overwrite, will replace pre-existing file in the /system folder. So in order to install the xposed framework, it's necessary to reinstall it with each update. | This script will automatically reinstall Xposed after dirty-flashing a ROM (i.e. flashing it without wiping userdata). The linked post includes instructions to download and how to install it, and describes how it works.
<https://www.reddit.com/r/xposed/comments/3u2xw9/release_xposed_addond_backup_scripts_it_keeps/>
Try to search "xposed script after updating cyanogenmod" with your search engine |
59,485 | Our entry door opens and closes fine but it won't engage the latch when it's closed. It almost seems like it's too small for the frame. The wind just howls through the opening and the strike plate on the frame will develop a frost layer on it. I have to use the deadbolt to keep it closed all the time. | 2015/02/13 | [
"https://diy.stackexchange.com/questions/59485",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/32700/"
] | I had a door with many of the same issues. It turned out that the previous owner had done a shoddy job of door installation.
The first step I would recommend is to check the door to ensure that it is square. IF the door was not hung correctly, it could cause many of the issues you described.
It may not be the door itself but the door frame. If the door frame is out of square, you can try to adjust the reveal to remedy the situation.
I ended up just replacing my door, as I wasn't very fond of the previous door anyways. It was an afternoon well spent. My house is much better insulated, as the new door actually has a decent R factor. | Shim out the hinges and then add weatherstripping to the hinge side. |
59,485 | Our entry door opens and closes fine but it won't engage the latch when it's closed. It almost seems like it's too small for the frame. The wind just howls through the opening and the strike plate on the frame will develop a frost layer on it. I have to use the deadbolt to keep it closed all the time. | 2015/02/13 | [
"https://diy.stackexchange.com/questions/59485",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/32700/"
] | Sometimes the problem is a misaligned strike, especially if thick weatherstripping was added since the door was installed but it can happen for other reasons. I've patched that on multiple doorframes... | Shim out the hinges and then add weatherstripping to the hinge side. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | The question is terribly broad. Are there cases where a company pulls an offer immediately? Sure. Is that common? No.
There was a bit of an internet kerfluffle about a year ago when [an offer to a candidate for an assistant professor position was pulled when the candidate sent back a counteroffer](http://www.cbsnews.com/news/how-to-mess-up-a-salary-negotiation/). Quite a few people weighed in on whether the counteroffer was appropriate, whether the college was being unreasonable, whether it was an [indictment of discriminatory attitudes in the hiring process](http://www.slate.com/blogs/xx_factor/2014/03/17/should_women_negotiate_for_more_pay_a_female_academic_leans_in_and_allegedly.html) or whether it was just an isolated case of a poorly handled negotiation.
Now, is it likely that your counteroffer is going to lead to your offer getting pulled? No. The more reasonable and realistic your request, the less likely it is. If your counteroffer asks for a salary that is way above what this company usually pays for the position and you ask for a number of perks that people in that position don't generally get, you may cause the company to pull the offer figuring that you're too far apart to make negotiation worth it (and that you're unlikely to be happy with whatever is agreed to meaning that you'll leave very quickly). If you ask for a small increase to the offered salary or some small additional perks, you may not get them but it's unlikely that the offer is going to be pulled. | There are a limited number of ways to negotiate without saying "no" and when you say "no", people are liable to take you at your word. At which point a company is not "bad" when they say "Ok, good luck".
I only know of two ways to counter offer without quite saying no. First, you can ask for time for another offer with better terms -- "Can I have a bit of extra time? I applied at X and made the final round, but they won't make their decision until next Tuesday. I prefer you, but they are offering Y". This does not reject their offer or their timetable, but lets them know that more money would move you from possible to definite. Secondly, you can change the details, but in such a way as it is not just asking for more. More vacation time against lower hourly wage or better performance for a bonus. Basically offer something in return, while indicating that the given offer might be acceptable.
If your counter is just $offer+$extra, then, as I said, it is entirely reasonable for them to accept your rejection of their offer and go on to their next candidate.
**Why wouldn't a company respond to a counter offer?**
A comapny is likely to respond to a counter offer if they believe there is a mutually satisfactory resolution. Whether that is the original offer, or another counter offer, they must believe you will be happy with the result. If they believe you will be unhappy, even if you accept the offer, they are going to at least hesitant to offer the position to you -- you can always leave, and having you leave will be distuptive. Why take the risk that you will quit without even starting because you have a better offer (several questions on The Workplace revolve around that scenario). Even if they think you might be happy, your offer may change how they view you, making you a less desirable candidate.
**Why do companies normally respond to counter-offers? Why negotiate at all?**
Companies normally respond to counter offers because they can either agree to the offer, or there is some middle ground which they can agree to, which they believe you will be happy with. The reason they even entertain negotiation is because rejecting a offer doesn't get them what they want - someone to do the job. If they reject your offer and go to the next person on their list, they have no guarantee that person will accept their offer, and at least some evidence that they might (after all, you did). As they go down the list, they would be getting less desirable candidates and using extra resources to do so.
In short, as long as you aren't too far apart, it is probably easier to accede or reiterate the original offer, but it is not bad (for either side) to just let it go. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | The question is terribly broad. Are there cases where a company pulls an offer immediately? Sure. Is that common? No.
There was a bit of an internet kerfluffle about a year ago when [an offer to a candidate for an assistant professor position was pulled when the candidate sent back a counteroffer](http://www.cbsnews.com/news/how-to-mess-up-a-salary-negotiation/). Quite a few people weighed in on whether the counteroffer was appropriate, whether the college was being unreasonable, whether it was an [indictment of discriminatory attitudes in the hiring process](http://www.slate.com/blogs/xx_factor/2014/03/17/should_women_negotiate_for_more_pay_a_female_academic_leans_in_and_allegedly.html) or whether it was just an isolated case of a poorly handled negotiation.
Now, is it likely that your counteroffer is going to lead to your offer getting pulled? No. The more reasonable and realistic your request, the less likely it is. If your counteroffer asks for a salary that is way above what this company usually pays for the position and you ask for a number of perks that people in that position don't generally get, you may cause the company to pull the offer figuring that you're too far apart to make negotiation worth it (and that you're unlikely to be happy with whatever is agreed to meaning that you'll leave very quickly). If you ask for a small increase to the offered salary or some small additional perks, you may not get them but it's unlikely that the offer is going to be pulled. | This is an old question but I'll chip in my own experience.
I've been fortunate to receive quite a few job offers in my life and I have countered every single last one of them to great results. Of all those times, I had my job offer pulled outright one time.
The company flew me to interview in person and put me up in a very nice hotel. I absolutely demolished the interview, and afterwards during lunch with what would have been my team I got along great with everyone. I thought it was a slam dunk. They were located in the Washington D.C. area which I knew was very expensive especially compared to where I was coming from but I had done no research ahead of time on cost of living. After lunch I was taken to meet with the CEO and he asked me what it would take me to move there. At that point in time I made about 80k in an extremely low cost of living area. I said I expected a slight bump from that + cost of living considerations, and then with a half shrug said 95k. If you have any idea how insane D.C. is you should know how terrible an ask this was. I got the offer a week later for 95k and started doing the math and it turned out we weren't in the same stratosphere compared to where I was. I wrote up what I thought was the most reasonable, apologetic, sincere letter I had ever written explaining my situation and what salary I thought made sense. They told me to fuck off and rescinded their offer.
Ultimately I viewed the whole thing as a learning experience and it worked out great for me as I was promoted soon after at my job but I've always been pretty annoyed by how it all played out. I think my biggest mistake was letting them beat a number out of me in person when I didn't have all the information I needed. Or even more, I should have known going in what I wanted. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | Offers being rescinded in response to attempts at negotiation aren't unheard of, but incredibly uncommon. This is counter to the entire idea of negotiation (and the interview process in general, for that matter).
As a new graduate, it's easy to forget the interview process is a two-way street. The employer is free to walk away if negotiations sour, as is the potential employee. If you get to the point of a job offer, and have not made a potential offer to be firm as offered, I think it's safe to say they want you and will work with you within a reasonable boundary to make it happen.
I felt compelled to weigh in on this since I was in a similar situation coming out of school. I had taken an internship with a Fortune 500 company for the summer prior to my final semester, and they ultimately interviewed me again toward the end of said semester and made an offer to come back to the team I previously worked with. Unfortunately, this was at the lower end of the salary range I quoted, so I told them **I'd think about it**. Note that I didn't explicitly close the door on the offer as it stood.
I had other interviews also lined up and went on to secure two other job offers, each with appealing aspects to them. Armed with this, I touched base with the hiring manager and was forthright about my situation - I made it clear that I wanted to work with them, but the other offers were tempting, and asked if they could sweeten the pot. Ultimately, they played ball and I happily accepted the revised offer at the higher end of my quoted range.
Arguably, the best negotiation tactic is the willingness to walk away, if push comes to shove, and having another bird in the hand (i.e. another job offer) helps immensely with that. Failing that, there is value in the facts that you are (presumably) a known quantity to the hiring manager (and therefore carry less risk than a random hire), plus acquired familiarity with the company culture, policies, and day-to-day role responsibilities (which reducing costs spent on training). There's no shame in making that explicit in your negotiations, nor would requesting a higher wage to commensurate for this. | There are a limited number of ways to negotiate without saying "no" and when you say "no", people are liable to take you at your word. At which point a company is not "bad" when they say "Ok, good luck".
I only know of two ways to counter offer without quite saying no. First, you can ask for time for another offer with better terms -- "Can I have a bit of extra time? I applied at X and made the final round, but they won't make their decision until next Tuesday. I prefer you, but they are offering Y". This does not reject their offer or their timetable, but lets them know that more money would move you from possible to definite. Secondly, you can change the details, but in such a way as it is not just asking for more. More vacation time against lower hourly wage or better performance for a bonus. Basically offer something in return, while indicating that the given offer might be acceptable.
If your counter is just $offer+$extra, then, as I said, it is entirely reasonable for them to accept your rejection of their offer and go on to their next candidate.
**Why wouldn't a company respond to a counter offer?**
A comapny is likely to respond to a counter offer if they believe there is a mutually satisfactory resolution. Whether that is the original offer, or another counter offer, they must believe you will be happy with the result. If they believe you will be unhappy, even if you accept the offer, they are going to at least hesitant to offer the position to you -- you can always leave, and having you leave will be distuptive. Why take the risk that you will quit without even starting because you have a better offer (several questions on The Workplace revolve around that scenario). Even if they think you might be happy, your offer may change how they view you, making you a less desirable candidate.
**Why do companies normally respond to counter-offers? Why negotiate at all?**
Companies normally respond to counter offers because they can either agree to the offer, or there is some middle ground which they can agree to, which they believe you will be happy with. The reason they even entertain negotiation is because rejecting a offer doesn't get them what they want - someone to do the job. If they reject your offer and go to the next person on their list, they have no guarantee that person will accept their offer, and at least some evidence that they might (after all, you did). As they go down the list, they would be getting less desirable candidates and using extra resources to do so.
In short, as long as you aren't too far apart, it is probably easier to accede or reiterate the original offer, but it is not bad (for either side) to just let it go. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | Is it a thing? It's always a possibility. If the company felt that the first offer was already pretty generous, it may have decided that the candidate was a little too pushy. Or maybe they found someone else in the interim. In any case, the offer as you describe it was not *rescinded* by the company, it was *rejected* by the candidate, and the candidate's counter offer was simply rejected. Nothing unprofessional there. | There are a limited number of ways to negotiate without saying "no" and when you say "no", people are liable to take you at your word. At which point a company is not "bad" when they say "Ok, good luck".
I only know of two ways to counter offer without quite saying no. First, you can ask for time for another offer with better terms -- "Can I have a bit of extra time? I applied at X and made the final round, but they won't make their decision until next Tuesday. I prefer you, but they are offering Y". This does not reject their offer or their timetable, but lets them know that more money would move you from possible to definite. Secondly, you can change the details, but in such a way as it is not just asking for more. More vacation time against lower hourly wage or better performance for a bonus. Basically offer something in return, while indicating that the given offer might be acceptable.
If your counter is just $offer+$extra, then, as I said, it is entirely reasonable for them to accept your rejection of their offer and go on to their next candidate.
**Why wouldn't a company respond to a counter offer?**
A comapny is likely to respond to a counter offer if they believe there is a mutually satisfactory resolution. Whether that is the original offer, or another counter offer, they must believe you will be happy with the result. If they believe you will be unhappy, even if you accept the offer, they are going to at least hesitant to offer the position to you -- you can always leave, and having you leave will be distuptive. Why take the risk that you will quit without even starting because you have a better offer (several questions on The Workplace revolve around that scenario). Even if they think you might be happy, your offer may change how they view you, making you a less desirable candidate.
**Why do companies normally respond to counter-offers? Why negotiate at all?**
Companies normally respond to counter offers because they can either agree to the offer, or there is some middle ground which they can agree to, which they believe you will be happy with. The reason they even entertain negotiation is because rejecting a offer doesn't get them what they want - someone to do the job. If they reject your offer and go to the next person on their list, they have no guarantee that person will accept their offer, and at least some evidence that they might (after all, you did). As they go down the list, they would be getting less desirable candidates and using extra resources to do so.
In short, as long as you aren't too far apart, it is probably easier to accede or reiterate the original offer, but it is not bad (for either side) to just let it go. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | This is an old question but I'll chip in my own experience.
I've been fortunate to receive quite a few job offers in my life and I have countered every single last one of them to great results. Of all those times, I had my job offer pulled outright one time.
The company flew me to interview in person and put me up in a very nice hotel. I absolutely demolished the interview, and afterwards during lunch with what would have been my team I got along great with everyone. I thought it was a slam dunk. They were located in the Washington D.C. area which I knew was very expensive especially compared to where I was coming from but I had done no research ahead of time on cost of living. After lunch I was taken to meet with the CEO and he asked me what it would take me to move there. At that point in time I made about 80k in an extremely low cost of living area. I said I expected a slight bump from that + cost of living considerations, and then with a half shrug said 95k. If you have any idea how insane D.C. is you should know how terrible an ask this was. I got the offer a week later for 95k and started doing the math and it turned out we weren't in the same stratosphere compared to where I was. I wrote up what I thought was the most reasonable, apologetic, sincere letter I had ever written explaining my situation and what salary I thought made sense. They told me to fuck off and rescinded their offer.
Ultimately I viewed the whole thing as a learning experience and it worked out great for me as I was promoted soon after at my job but I've always been pretty annoyed by how it all played out. I think my biggest mistake was letting them beat a number out of me in person when I didn't have all the information I needed. Or even more, I should have known going in what I wanted. | There are a limited number of ways to negotiate without saying "no" and when you say "no", people are liable to take you at your word. At which point a company is not "bad" when they say "Ok, good luck".
I only know of two ways to counter offer without quite saying no. First, you can ask for time for another offer with better terms -- "Can I have a bit of extra time? I applied at X and made the final round, but they won't make their decision until next Tuesday. I prefer you, but they are offering Y". This does not reject their offer or their timetable, but lets them know that more money would move you from possible to definite. Secondly, you can change the details, but in such a way as it is not just asking for more. More vacation time against lower hourly wage or better performance for a bonus. Basically offer something in return, while indicating that the given offer might be acceptable.
If your counter is just $offer+$extra, then, as I said, it is entirely reasonable for them to accept your rejection of their offer and go on to their next candidate.
**Why wouldn't a company respond to a counter offer?**
A comapny is likely to respond to a counter offer if they believe there is a mutually satisfactory resolution. Whether that is the original offer, or another counter offer, they must believe you will be happy with the result. If they believe you will be unhappy, even if you accept the offer, they are going to at least hesitant to offer the position to you -- you can always leave, and having you leave will be distuptive. Why take the risk that you will quit without even starting because you have a better offer (several questions on The Workplace revolve around that scenario). Even if they think you might be happy, your offer may change how they view you, making you a less desirable candidate.
**Why do companies normally respond to counter-offers? Why negotiate at all?**
Companies normally respond to counter offers because they can either agree to the offer, or there is some middle ground which they can agree to, which they believe you will be happy with. The reason they even entertain negotiation is because rejecting a offer doesn't get them what they want - someone to do the job. If they reject your offer and go to the next person on their list, they have no guarantee that person will accept their offer, and at least some evidence that they might (after all, you did). As they go down the list, they would be getting less desirable candidates and using extra resources to do so.
In short, as long as you aren't too far apart, it is probably easier to accede or reiterate the original offer, but it is not bad (for either side) to just let it go. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | Offers being rescinded in response to attempts at negotiation aren't unheard of, but incredibly uncommon. This is counter to the entire idea of negotiation (and the interview process in general, for that matter).
As a new graduate, it's easy to forget the interview process is a two-way street. The employer is free to walk away if negotiations sour, as is the potential employee. If you get to the point of a job offer, and have not made a potential offer to be firm as offered, I think it's safe to say they want you and will work with you within a reasonable boundary to make it happen.
I felt compelled to weigh in on this since I was in a similar situation coming out of school. I had taken an internship with a Fortune 500 company for the summer prior to my final semester, and they ultimately interviewed me again toward the end of said semester and made an offer to come back to the team I previously worked with. Unfortunately, this was at the lower end of the salary range I quoted, so I told them **I'd think about it**. Note that I didn't explicitly close the door on the offer as it stood.
I had other interviews also lined up and went on to secure two other job offers, each with appealing aspects to them. Armed with this, I touched base with the hiring manager and was forthright about my situation - I made it clear that I wanted to work with them, but the other offers were tempting, and asked if they could sweeten the pot. Ultimately, they played ball and I happily accepted the revised offer at the higher end of my quoted range.
Arguably, the best negotiation tactic is the willingness to walk away, if push comes to shove, and having another bird in the hand (i.e. another job offer) helps immensely with that. Failing that, there is value in the facts that you are (presumably) a known quantity to the hiring manager (and therefore carry less risk than a random hire), plus acquired familiarity with the company culture, policies, and day-to-day role responsibilities (which reducing costs spent on training). There's no shame in making that explicit in your negotiations, nor would requesting a higher wage to commensurate for this. | This is an old question but I'll chip in my own experience.
I've been fortunate to receive quite a few job offers in my life and I have countered every single last one of them to great results. Of all those times, I had my job offer pulled outright one time.
The company flew me to interview in person and put me up in a very nice hotel. I absolutely demolished the interview, and afterwards during lunch with what would have been my team I got along great with everyone. I thought it was a slam dunk. They were located in the Washington D.C. area which I knew was very expensive especially compared to where I was coming from but I had done no research ahead of time on cost of living. After lunch I was taken to meet with the CEO and he asked me what it would take me to move there. At that point in time I made about 80k in an extremely low cost of living area. I said I expected a slight bump from that + cost of living considerations, and then with a half shrug said 95k. If you have any idea how insane D.C. is you should know how terrible an ask this was. I got the offer a week later for 95k and started doing the math and it turned out we weren't in the same stratosphere compared to where I was. I wrote up what I thought was the most reasonable, apologetic, sincere letter I had ever written explaining my situation and what salary I thought made sense. They told me to fuck off and rescinded their offer.
Ultimately I viewed the whole thing as a learning experience and it worked out great for me as I was promoted soon after at my job but I've always been pretty annoyed by how it all played out. I think my biggest mistake was letting them beat a number out of me in person when I didn't have all the information I needed. Or even more, I should have known going in what I wanted. |
58,120 | I got a conditional offer for a company and was beginning to research salaries for that field to counter their first offer. I am going to be a new time hire (graduating in the spring), but have a year+ experience through internships and interned at this company the previous summer so I know the job well.
I began asking around for advice on how to approach the negotiation just to get a well rounded idea of how people handle it. When I asked one of my friends, his response was first time hires (people who just graduated), don't ask for more money and only those who have worked in the field for a while are supposed to negotiate.
He then went on to say he knew someone who tried to negotiate their salary and after the first attempt the company pulled the offer outright. So my question is: is that a thing? I have no doubt a company would pull their offer if you kept pushing/ were rude/ etc... But after one attempt? That seemed incredibly unlikely.
Or perhaps this company is just a bad company altogether and it saved him in the end to know up front they do not behave in a professional matter? | 2015/11/21 | [
"https://workplace.stackexchange.com/questions/58120",
"https://workplace.stackexchange.com",
"https://workplace.stackexchange.com/users/25676/"
] | Is it a thing? It's always a possibility. If the company felt that the first offer was already pretty generous, it may have decided that the candidate was a little too pushy. Or maybe they found someone else in the interim. In any case, the offer as you describe it was not *rescinded* by the company, it was *rejected* by the candidate, and the candidate's counter offer was simply rejected. Nothing unprofessional there. | This is an old question but I'll chip in my own experience.
I've been fortunate to receive quite a few job offers in my life and I have countered every single last one of them to great results. Of all those times, I had my job offer pulled outright one time.
The company flew me to interview in person and put me up in a very nice hotel. I absolutely demolished the interview, and afterwards during lunch with what would have been my team I got along great with everyone. I thought it was a slam dunk. They were located in the Washington D.C. area which I knew was very expensive especially compared to where I was coming from but I had done no research ahead of time on cost of living. After lunch I was taken to meet with the CEO and he asked me what it would take me to move there. At that point in time I made about 80k in an extremely low cost of living area. I said I expected a slight bump from that + cost of living considerations, and then with a half shrug said 95k. If you have any idea how insane D.C. is you should know how terrible an ask this was. I got the offer a week later for 95k and started doing the math and it turned out we weren't in the same stratosphere compared to where I was. I wrote up what I thought was the most reasonable, apologetic, sincere letter I had ever written explaining my situation and what salary I thought made sense. They told me to fuck off and rescinded their offer.
Ultimately I viewed the whole thing as a learning experience and it worked out great for me as I was promoted soon after at my job but I've always been pretty annoyed by how it all played out. I think my biggest mistake was letting them beat a number out of me in person when I didn't have all the information I needed. Or even more, I should have known going in what I wanted. |
119,851 | My family and I live in an apartment. There is very hot water coming out of the cold water taps, and the toilet. I know it's summer so I expect some. In order to get even mildly cool water we have to flush the toilet, or let the water run for at least 20 minutes. The issue is just getting worse. I've put work orders into the landlord. The plumber said that this is normal. It is not. We have lived here for 3 years almost 4. This just started a few months ago and has gotten progressively worse.
After my work out I take cold showers because my apartment does not have A/C. I let the water run to purge the hot water from the pipes. In the shower we only get luke warm water now. There is no cold water on a single hand mixer. That is even when it is supposed to be on the cold area completely. After 15 minutes in the shower the water was still luke warm, no cold water coming through. While rinsing off I was burned on my inner thighs and genital area, 1st degree. I double checked the temperature gauge. Completely in the blue area. I need help. Please. I think this plumber's experience is working against him.
If anyone in our apartment building uses the water at all we finally get a bit of somewhat cold water (approx 80-90 deg F). We shouldn't get hotter water coming through when it is on the cold. As far as I can tell the boiler is dieing but I'm not sure. What can I do to help my landlord? | 2017/07/21 | [
"https://diy.stackexchange.com/questions/119851",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/72325/"
] | Pushing your switches back into the box is causing something to short together - your screws, grounds, or any exposed wire sticking out of backstabs (of which there should be none).
Are you getting intense arc flashes? If you look closely at your screws, grounds, and any exposed wire sticking out of backstabs -- you will probably find arcing marks that will tell the tale.
If you are not getting arc flashes of any size, this part of the circuit may be protected by AFCI or GFCI.
To protect screws, wrap the switch or receptacle with electrical tape so the screws are covered. | I had that problem too. After installation of the switch I pressed too much to check the on/off. The breaker tripped. I fixed the box alignment to resolve this issue. Please make sure the on the wall is not too much misaligned. |
16,397,551 | This is my first question here so sorry if I get something wrong.
I am trying to draw a polyline in Google Maps but the specified color for the polyline seems not to accept the alpha channel of the color. The line is always solid.
How could be this achieved? or is it possible at all?
I am doing this with Xamarin.iOS and the google maps control for the Xamarin.iOS but a solution in Objective C and Google Maps SDK for iOS would be great too. | 2013/05/06 | [
"https://Stackoverflow.com/questions/16397551",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/2354361/"
] | I think that I found a solution to the problem, but it is a semi-solution because not every color can be reproduced.
I used full green to draw a line and the alpha channel did not seem to have any effect.
When I used a line with RBG color (0,0,10) it seems to create a line that is semi transparent and green.
So to me it looks like that the RBG color channels are actually combined the color and the transparency (or they are implemented so that the color channel is just transparency channel for the full color). | Did you only run it on the simulator or on the device as well? From my testings it appears that there's a bug in the simulator that makes all polylines opaque, but the alpha channel works on the device. |
203,373 | I am proposing a new feature in Stack overflow where questions or comments with too many negative votes automatically be put on hold.
This is not a new feature and it is not an original idea. I have seen this feature on Youtube
Now, if you see the comments are hidden from public view and not entirely removed.
So this is what i am proposing.
**Questions & answers with 8 downvotes or more automatically be put on hold.**
And the down votes should be a sum of upvotes and downvotes so 2 upvotes and 10 downvotes should still be put on hold. | 2013/10/29 | [
"https://meta.stackexchange.com/questions/203373",
"https://meta.stackexchange.com",
"https://meta.stackexchange.com/users/231854/"
] | Questions with enough downvotes are already automatically hidden from the front page without being closed. If you want to compare this to YouTube, notice that hidden comments can still be replied to, so in the same way we shouldn't be closing questions to new answers just because they've been heavily downvoted.
Answers cannot be closed or put on hold, so your feature request makes no sense for answers. Unless you mean closed to new comments, in which case, posts always accept comments unless locked or deleted, and likewise again comments on YouTube are always open to replies unless deleted.
Just getting this in before the question gets closed for having too many downvotes. | This is what are close votes for. If someone thinks question should be closed, he/she can use that close vote. I downvote questions which I want to close only of the questions is really really bad. Otherwise, I don't waste regular votes on such questions. I prefer to spare them to reward someone for giving a good answer or asking a good question (or reserve for downvoting something really bad).
That what you propose is the duplication of already existing functionality, encouraging to use the regular votes in the other way as they are designed to. |
37 | I believe a Markov chain is a sequence of events where each subsequent event depends probabilistically on the current event. What are examples of the application of a Markov chain and can it be used to create artificial intelligence? Would a genetic algorithm be an example of a Markov chain since each generation depends upon the state of the prior generation? | 2016/08/02 | [
"https://ai.stackexchange.com/questions/37",
"https://ai.stackexchange.com",
"https://ai.stackexchange.com/users/55/"
] | A Markov model includes the probability of transitioning to each state considering the current state. "Each state" may be just one point - whether it rained on specific day, for instance - or it might look like multiple things - like a pair of words. You've probably seen automatically generated weird text that *almost* makes sense, like [Garkov](https://blog.codinghorror.com/markov-and-you/) (the output of a Markov model based on the Garfield comic strips). That Coding Horror article also mentions the applications of Markov techniques to Google's PageRank.
Markov models are really only powerful when they have a lot of input to work with. If a machine looked through a lot of English text, it would get a pretty good idea of what words generally come after other words. Or after looking through someone's location history, it could figure out where that person is likely to go next from a certain place. Constantly updating the "input corpus" as more data is received would let the machine tune the probabilities of all the state transitions.
Genetic algorithms are fairly different things. They create functions by shuffling around parts of functions and seeing how good each function is at a certain task. A child algorithm will depend on its parents, but Markov models are interested mostly in predicting what thing will come next in a sequence, not creating a new chunk of code. You might be able to use a Markov model to spit out a candidate function, though, depending on how simple the "alphabet" is. You could even then give more weight to the transitions in successful algorithms. | >
> (this was intended as a comment, but turned out long and longer)
>
>
>
A couple of points to elaborate on [Ben's answer](https://ai.stackexchange.com/a/73/70):
* It is possible to generate different models (out of existing data!) and then look for the model that best fit new data (e.g. with [knn](https://en.wikipedia.org/wiki/K-nearest_neighbors_algorithm)). Example:
+ States = {*sleep*, *eat*, *walk*, *work*}
+ Model 1: Most probable sequence on weekdays, say: sleep → sleep → eat → walk → work → work → eat → walk → sleep → sleep
+ Model 2: Most probable sequence on weekends, some: sleep → sleep → eat → walk → eat → walk → sleep → sleep
+ New data arrives: Which sequence is more probable that it came from? Check model 1, check model 2. Which fits better? → Assign
* Note that the previous example is oversimplified. Also note that a *unit time* is needed there (other than letters / words, for instance).
* You can *nest* Markov models. That means that you generate a model (a set of probabilities for all the states) in a "lower scale" and then use it in a more abstract model. For example, you can nest your day-scale model to a month or year (to include holidays, for instance).
Also [see this link for a nice introduction](http://blog.wolfram.com/2013/02/04/centennial-of-markov-chains/) and [some posts in crossvalidated](https://stats.stackexchange.com/questions/tagged/mcmc?sort=votes&pageSize=50).
---
As for the question if artificial intelligence can be created by using this kind of methods, my personal (easy) answer would be **no**, because they only relate data and probabilities and thus belong more to the statistics and machine learning branch.
A longer answer needs to take into account the [weak vs. strong AI question](https://ai.stackexchange.com/questions/74/what-is-the-difference-between-strong-ai-and-weak-ai). |
526,896 | I've gotten my hands on a seriously cheap laptop grade 2.5 inch drive. I'm intending to use one on a desktop that doesn't have 2.5 inch bays as a boot drive. While I know there are adapters available, I know its fairly common with SSDs to simply velcro/tape the drive somewhere. I'm wondering if I can do the same with a laptop hard drive.
One issue I see here is SSDs are fairly insensitive to vibration, while hard drives are. Just how vibration sensitive are drives? Would a jerry rigged mount need to take this into account? | 2013/01/02 | [
"https://superuser.com/questions/526896",
"https://superuser.com",
"https://superuser.com/users/10165/"
] | Laptop drives are generally more vibration-resistant than desktop drives (they are designed to be used in a moving plane, car, in a laptop on someone's laps, etc.), so from this standpoint there shouldn't be a problem taping them somewhere inside your computer's case. There are other problems, however:
* When hard drive is fastened properly, metal bracket also acts as a heatsink. Moreover, in a properly designed case there should be an airflow around a hard drive. Your tape will have lower thermal conductivity than metal, and depending where you tape it, there could be less airflow available. So your hard drive could overheat.
* Constant vibration (from hard drive's motor, computer's fans, etc.) can loosen the tape over time, depending what kind of a tape you use, it can dry up, etc. So don't put your hard drive vertically somewhere, make sure it's fairly secure without the tape, and use the tape as an additional measure, not as something that prevents your hard drive from falling down on your motherboard, for example.
* Make sure you don't short anything on hard drive's PCB, if it is exposed (e.g. there are no protruding screw heads on the surface that you tape your hard drive to).
I've used tape to secure 2.5" hard drives in a desktop tapes, but only temporarily (till I got around to order a few of those conversion brackets). | The hard drive is not particularly sensitive to vibration -- vibration will destroy any piece of electronics over time, but drives produce their own vibration and hence are "beefed up" a bit. And laptop drives even more.
The real limit with hard drives is peak G force. This isn't vibration so much as "shock" -- a sudden jolt -- and it only takes one such event in excess of the drive's G limit to damage a drive.
**A bit of a war story:**
Some years back, when I was working on IBM AS/400 computers, they were having trouble in the development lab with drives failing. To permit multiple people to (serially) use a single test system, drives were mounted in sliding plug-in trays, and drives would be exchanged when a test scenario was changed.
But it seems that drives would fail when exchanged this way -- a drive would be good, would be carefully removed and gently set down on a conductive foam pad. But then, an hour later, the drive would be inserted and would be found to be "crashed".
Analysis of the drives showed that they'd been subjected to excessive shock, but originally no one could figure out the source of the shock. Then it was realized that the shock of snapping the drive into the socket (as the tray was slid into the machine) was enough to do this damage.
Of course, these were old "big iron" drives, and current desktop and (especially) laptop drives are much more robust, but still the hazard is mechanical shock that does not seem, to a human, to even be worth noticing, but which to a drive can be devastating, due to the proximity of the shock source to the fragile parts in the drive. |
526,896 | I've gotten my hands on a seriously cheap laptop grade 2.5 inch drive. I'm intending to use one on a desktop that doesn't have 2.5 inch bays as a boot drive. While I know there are adapters available, I know its fairly common with SSDs to simply velcro/tape the drive somewhere. I'm wondering if I can do the same with a laptop hard drive.
One issue I see here is SSDs are fairly insensitive to vibration, while hard drives are. Just how vibration sensitive are drives? Would a jerry rigged mount need to take this into account? | 2013/01/02 | [
"https://superuser.com/questions/526896",
"https://superuser.com",
"https://superuser.com/users/10165/"
] | Laptop drives are generally more vibration-resistant than desktop drives (they are designed to be used in a moving plane, car, in a laptop on someone's laps, etc.), so from this standpoint there shouldn't be a problem taping them somewhere inside your computer's case. There are other problems, however:
* When hard drive is fastened properly, metal bracket also acts as a heatsink. Moreover, in a properly designed case there should be an airflow around a hard drive. Your tape will have lower thermal conductivity than metal, and depending where you tape it, there could be less airflow available. So your hard drive could overheat.
* Constant vibration (from hard drive's motor, computer's fans, etc.) can loosen the tape over time, depending what kind of a tape you use, it can dry up, etc. So don't put your hard drive vertically somewhere, make sure it's fairly secure without the tape, and use the tape as an additional measure, not as something that prevents your hard drive from falling down on your motherboard, for example.
* Make sure you don't short anything on hard drive's PCB, if it is exposed (e.g. there are no protruding screw heads on the surface that you tape your hard drive to).
I've used tape to secure 2.5" hard drives in a desktop tapes, but only temporarily (till I got around to order a few of those conversion brackets). | Just to give some intuition it is often said that you should handle a hard drive like a raw egg - and the point is that you can take this literally!
According to this [article](https://www.quora.com/How-many-g-forces-can-an-egg-withstand) a raw egg should be able to withstand about 20 G without breaking. Most modern hard drives are able to withstand about 60+ G while operating.
So if the shock would not have damaged the shell of a raw egg you should be on the save side, even when the hard drive was working. |
526,896 | I've gotten my hands on a seriously cheap laptop grade 2.5 inch drive. I'm intending to use one on a desktop that doesn't have 2.5 inch bays as a boot drive. While I know there are adapters available, I know its fairly common with SSDs to simply velcro/tape the drive somewhere. I'm wondering if I can do the same with a laptop hard drive.
One issue I see here is SSDs are fairly insensitive to vibration, while hard drives are. Just how vibration sensitive are drives? Would a jerry rigged mount need to take this into account? | 2013/01/02 | [
"https://superuser.com/questions/526896",
"https://superuser.com",
"https://superuser.com/users/10165/"
] | The hard drive is not particularly sensitive to vibration -- vibration will destroy any piece of electronics over time, but drives produce their own vibration and hence are "beefed up" a bit. And laptop drives even more.
The real limit with hard drives is peak G force. This isn't vibration so much as "shock" -- a sudden jolt -- and it only takes one such event in excess of the drive's G limit to damage a drive.
**A bit of a war story:**
Some years back, when I was working on IBM AS/400 computers, they were having trouble in the development lab with drives failing. To permit multiple people to (serially) use a single test system, drives were mounted in sliding plug-in trays, and drives would be exchanged when a test scenario was changed.
But it seems that drives would fail when exchanged this way -- a drive would be good, would be carefully removed and gently set down on a conductive foam pad. But then, an hour later, the drive would be inserted and would be found to be "crashed".
Analysis of the drives showed that they'd been subjected to excessive shock, but originally no one could figure out the source of the shock. Then it was realized that the shock of snapping the drive into the socket (as the tray was slid into the machine) was enough to do this damage.
Of course, these were old "big iron" drives, and current desktop and (especially) laptop drives are much more robust, but still the hazard is mechanical shock that does not seem, to a human, to even be worth noticing, but which to a drive can be devastating, due to the proximity of the shock source to the fragile parts in the drive. | Just to give some intuition it is often said that you should handle a hard drive like a raw egg - and the point is that you can take this literally!
According to this [article](https://www.quora.com/How-many-g-forces-can-an-egg-withstand) a raw egg should be able to withstand about 20 G without breaking. Most modern hard drives are able to withstand about 60+ G while operating.
So if the shock would not have damaged the shell of a raw egg you should be on the save side, even when the hard drive was working. |
23,078,280 | a little time ago I concluded my class diagram and now I want to populate it in a massive way. I made my database (Oracle 10g) from java objects through the ddl-generation function of EclipseLink. Now my doubt is how to make this bulk insert.
I thought to do this in two way:
* Since I think to use also spring and maven during the development, I
thought to read the data from an file and to persist them during test
life cycle.
* Or serching on google I saw a few example like [Bulk insert with oracle](http://www.akadia.com/services/ora_bulk_insert.html)
Any suggestion about this? | 2014/04/15 | [
"https://Stackoverflow.com/questions/23078280",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/2069976/"
] | Your solution is good. I can't see any better option. | Just for clarify;
Now, with OOP, the goal is to work with objects.
So first step is to create object from database. If you want to go further, you can use an ORM and create your DAO. With this layer, you can manipulate object, modify them and finally save them into database with OOP approach. An exemple, Doctrine2 : [Doctrine website](http://www.doctrine-project.org/)
Now, for simple projet you do not absolutely need ORM. Just take care to work with object, and, for exemple, create little method in your object: save(...) who Insert in DB your object.
Complexify it by adding update, delete,... and finally go on CRUD system.
I think it's good idea before go directly on ORM, and see you to learn and concept good OO project.
Hope it's will help you (and sorry for my very bad english :) ) |
3,405,009 | I thought developer tools could do this but I'm struggling to find it. Any other recommendations? | 2010/08/04 | [
"https://Stackoverflow.com/questions/3405009",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/14357/"
] | [Fiddler](http://www.fiddler2.com/fiddler2/) can do it. | [Fiddler](http://://www.fiddler2.com/fiddler2/) is the best tool.
Depending on needs you can use network sniffer as well, like [Wireshark](http://www.wireshark.org/) or Microsoft Network Monitor. |
3,405,009 | I thought developer tools could do this but I'm struggling to find it. Any other recommendations? | 2010/08/04 | [
"https://Stackoverflow.com/questions/3405009",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/14357/"
] | [Fiddler](http://www.fiddler2.com/fiddler2/) can do it. | I have had success with [HTTP Watch Basic](http://www.httpwatch.com/). I have tried Fiddler and wireshark. They are great tools, assuming you have the permission to use them in a corporate environment. Typically, the corporate security team will not allow them to be installed (at least in my situation). I have had success with HTTP Watch Basic when debugging SAML issues for single-sign-on. HTTP Watch basic seems to be the the primary option to use for IE8. |
11,727 | I would like to release my software under stronger copyleft than GPL (and AGPL), namely I would like to impose the burden of releasing sources of any derivative work, even the work intended for internal usage only, when such derivative work has a definite and non-test-related usage.
This would basically count as more restrictive version of AGPL (which does this to the extent of webserver code), while I would like to cover also this example cases:
1. Derivative work of my code is used in research projects to produce artifacts (e.g. plots of some measurements derived using such code). Then I want that the derivative work must be released under the same license, and made available to the public.
2. A company wants to use parts of the software in a tool for internal usage (only to be used by employees and never by external users, so that would not qualify under AGPL terms), then the license requires the company to publicly release the source code of the derivative work.
But crucially temporary modification of the code for testing purposes or until the derivative work has not fulfilled its intended usage (e.g. the research plots have not yet been published or the internal usage tool is in pre-alpha stage) can remain closed-source.
I would like to know if there exists a license with such requirements, and if not whether it would be sensible in my use case to add clauses to GPLv3. | 2021/05/21 | [
"https://opensource.stackexchange.com/questions/11727",
"https://opensource.stackexchange.com",
"https://opensource.stackexchange.com/users/23076/"
] | Different licensors have different intensions. But licensors issuing Open Source licenses are generally trying to maximize Software Freedom. Copyleft licenses try to maximize Software Freedom by ensuring that every *recipient* or user of the software has full rights e.g. to share this software further and to modify it. Modification requires access to the source code, though. Overbearing source disclosure requirements jeopardize these freedoms.
GPLv3 connects the source code obligation to conveyance of the software. AGPL also requires an offer for source code when the user interacts remotely over a network with a modified copy. The Cryptographic Autonomy License goes further, requiring such an offer to anyone who the work was made perceptible to, if this would otherwise violate the licensor's IP.
However, all these licenses are enforceable because they are rooted in copyright law. If I copy a software, I need a license of the copyright holder. They can attach conditions to that license, or also refuse it. The copyright holder can't prevent me (on the basis of copyright) from doing stuff that isn't covered by copyright, such as writing a review of the software or publishing the output of the software. To do that, we'd need a contract such as an EULA. Creating such a contract in an enforcible manner while still allowing modified versions to be freely shared is an extremely difficult problem. In any case, using such a contract to restrict what the user can do instead of permitting what would be otherwise prohibited by copyright would likely violate the principles of Software Freedom or Open Source, e.g. compare OSD #6.
Such clauses would also have practical problems. If I publish a paper that includes a diagram created by a software, and the licensing of this software requires me to publish the software, a big question is: *how*. Clearly, I can't include the software's source code in the paper or in the diagram. I could publish it for some duration at some URL that is listed on the paper, but this won't guarantee that this URL would be accessible later, or that the original author's of the software which I modified would learn about these modifications.
If the license were to require notification or publication, this could also fail some tests established in the Debian community for open source/free software licenses. In the *Desert Island Test*, we have to consider whether someone can comply with the license if they don't have internet. In the *Chinese Dissident Test*, we have to consider that publication of the fact that someone is working on politically sensitive software could lead to repression.
So in summary, I don't know of an Open Source/Free Software license that satisfies your requirements, and I have severe doubts whether such a license could exist. | I think it is very unlikely such a license would have any legal traction. Copyright, on which software licenses are based, has mostly to do with copying/distributing the work, internal use is not distribution.
And nobody in their right mind would license that way, just to get subjected to the firehose of "I changed line 427 to see if...", "Oops, rewriting lines 442 through 493 to quell our compiler warnings bombs out with...".
And I, for one, would steer *well way* from such software. What is I can't comply with the reporting requirement because the 'net is down here today? The licensor dropped off the 'net for good? |
147,156 | Twice now, I've read a paper written by a prominent researcher and some other "younger" researchers, e.g. instead of being superstars they're merely professors, I guess. In the text, he is referred to as the "senior author", e.g. in sentences that read like "In [4], the senior proved this result which is relevant to us because..."
I was a bit shocked, to be honest, essentially because I had never seen something like this in (pure) mathematics. In my mind there was always the implicit assumption that all others contributed approximately equally to the paper, which explained the alphabetical ordering of authors in (almost) all papers.
How common is this? Have you seen this before, and if so, how often? | 2020/04/02 | [
"https://academia.stackexchange.com/questions/147156",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/122169/"
] | I'll guess that this is pretty uncommon, but the situation itself is a bit uncommon. Perhaps it is just that the senior professor is mentor to all of the others and they want to honor the person. It may well be that one person produces a key result that the others then explore, develop, and they put it all together.
I did something similar (maybe even more rare) in my doctoral work. For one of the key theorems, the thesis and later publication, contains a proof by my advisor. I had an alternate proof, but his was more interesting and had potential for new insights into the field. My proof was more pedestrian. So, while I was actually sole author, his proof is contained in the paper and credited there to him.
But, I think you are correct. In pure math, a paper with several authors has a basic assumption that all contributed in such a way that it is impossible to rank who contributed "more" than others and so authors are listed alphabetically. Even if one person has an idea "first", others can be key to the exploration and development of the idea. Even "small" insights can have a big effect. It saves a tremendous amount of grief. I've been told that in applied math, different standards apply.
But honoring special contributions is also fine when it happens. | It seems rather unusual, and I consider it bad style to use a descriptor that readers will not be able to figure out unless they consult the list of references. (With "first author" you can at least get a reminder by looking at the running header.) It is, of course, possible that the first author is indeed the senior author, and in the context of the journal that might be an acceptable synonym. |
147,156 | Twice now, I've read a paper written by a prominent researcher and some other "younger" researchers, e.g. instead of being superstars they're merely professors, I guess. In the text, he is referred to as the "senior author", e.g. in sentences that read like "In [4], the senior proved this result which is relevant to us because..."
I was a bit shocked, to be honest, essentially because I had never seen something like this in (pure) mathematics. In my mind there was always the implicit assumption that all others contributed approximately equally to the paper, which explained the alphabetical ordering of authors in (almost) all papers.
How common is this? Have you seen this before, and if so, how often? | 2020/04/02 | [
"https://academia.stackexchange.com/questions/147156",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/122169/"
] | >
> Is it common to make seniority distinctions between coauthors of a paper in math?
>
>
>
This is uncommon. However it seems less unusual to refer to something one of the authors did, e.g.:
>
> In a previous result [2] by one of the authors, it is shown that ...
>
>
>
or:
>
> This builds on prior work of the first author [3], namely, ...
>
>
>
As Andrés E. Caicedo says in the comments, I would assume that this is just a way to refer to one of the authors, similar to the above statements. That is, this is **not** a way to imply that they are more important, or contributed more to the paper. (If anything I would assume the senior author contributed a little less :) ) It may be a small gesture of respect, formality, or acknowledgement to the mentor of the work, but nothing more.
>
> In my mind there was always the implicit assumption that all others contributed approximately equally to the paper
>
>
>
Yes, this is indeed the implicit assumption. Moreover, referring to an author as the "senior" author does not really contradict this. | It seems rather unusual, and I consider it bad style to use a descriptor that readers will not be able to figure out unless they consult the list of references. (With "first author" you can at least get a reminder by looking at the running header.) It is, of course, possible that the first author is indeed the senior author, and in the context of the journal that might be an acceptable synonym. |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | Installing plugins into moodle is as simple as copying them to the /mod/ directory. SQL tables will be written and updated.
Then you should be able to see this module on the next login.
EDIT:
Check if the permissions for that folder and files are correct. Check if the file version.php exists and is correct (check other modules to see how its done). Check if the directory structure is correct also.
If all else fails, I would check out some other modules that are similar to yours and mimic their setup procedure
EDIT 2:
There's not much more i can assist you with. I am sorry. | we now included the version.php file and thus the error
"Module devtp: C:\wamp\www\moodle/mod/devtp/version.php was not readable" is no longer coming. thank you for the help.
But still,our module has not been included under notifications in Moodle.We consulted the MOODLE site for help,
"<http://docs.moodle.org/en/Installing_contributed_modules_or_plugins>"
and followed the instruction:
// Visit your Local Moodle site <http://localhost:8888/moodle19/>
Site Administration
Notifications
Scroll to the bottom of the page and click on "Continue"//
but the fact is that ,neither is our module appearing under notifications and nor is continue coming.
Awaiting your response... |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | Here is Moodle's official Documentation for developing a **new Module**:
<http://docs.moodle.org/en/newmodule>
start with the suggested **template** (download.moodle.org/plugins19/mod/NEWMODULE.zip) to wrap your code with.
You can always look inside **Kaltura.com**'s video plugin code (<http://www.kaltura.org/kaltura-moodle-plugin-installation-guide>) and see how video can be implemented into Moodle. in general. | Installing plugins into moodle is as simple as copying them to the /mod/ directory. SQL tables will be written and updated.
Then you should be able to see this module on the next login.
EDIT:
Check if the permissions for that folder and files are correct. Check if the file version.php exists and is correct (check other modules to see how its done). Check if the directory structure is correct also.
If all else fails, I would check out some other modules that are similar to yours and mimic their setup procedure
EDIT 2:
There's not much more i can assist you with. I am sorry. |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | Installing plugins into moodle is as simple as copying them to the /mod/ directory. SQL tables will be written and updated.
Then you should be able to see this module on the next login.
EDIT:
Check if the permissions for that folder and files are correct. Check if the file version.php exists and is correct (check other modules to see how its done). Check if the directory structure is correct also.
If all else fails, I would check out some other modules that are similar to yours and mimic their setup procedure
EDIT 2:
There's not much more i can assist you with. I am sorry. | A simple way to add video to a moodle course (if you dont want to create or invest in plugin) is to create a new 'page' type resource in moodle course.
In HTML code of that page add code for embedding a video.
Video can be hosted on youtube or your own CDN. For own CDN you may have to use video.js |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | thank you for the help.
we tried exactlty what you suggested,but it didnt work out .this is the response that we are getting...
Module devtp: C:\wamp\www\moodle/mod/devtp/version.php was not readable
where,'devtp' is the name of the plug-in directory that we would like to add.
do you think we have missed out on including any related files for our plug-in or is it bcoz we need to include some files that can make the plug-in COMPATIBLE with the current version of MOODLE. Our Moodle VERSION is 1.9.
Awaiting your response. | we now included the version.php file and thus the error
"Module devtp: C:\wamp\www\moodle/mod/devtp/version.php was not readable" is no longer coming. thank you for the help.
But still,our module has not been included under notifications in Moodle.We consulted the MOODLE site for help,
"<http://docs.moodle.org/en/Installing_contributed_modules_or_plugins>"
and followed the instruction:
// Visit your Local Moodle site <http://localhost:8888/moodle19/>
Site Administration
Notifications
Scroll to the bottom of the page and click on "Continue"//
but the fact is that ,neither is our module appearing under notifications and nor is continue coming.
Awaiting your response... |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | Here is Moodle's official Documentation for developing a **new Module**:
<http://docs.moodle.org/en/newmodule>
start with the suggested **template** (download.moodle.org/plugins19/mod/NEWMODULE.zip) to wrap your code with.
You can always look inside **Kaltura.com**'s video plugin code (<http://www.kaltura.org/kaltura-moodle-plugin-installation-guide>) and see how video can be implemented into Moodle. in general. | thank you for the help.
we tried exactlty what you suggested,but it didnt work out .this is the response that we are getting...
Module devtp: C:\wamp\www\moodle/mod/devtp/version.php was not readable
where,'devtp' is the name of the plug-in directory that we would like to add.
do you think we have missed out on including any related files for our plug-in or is it bcoz we need to include some files that can make the plug-in COMPATIBLE with the current version of MOODLE. Our Moodle VERSION is 1.9.
Awaiting your response. |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | thank you for the help.
we tried exactlty what you suggested,but it didnt work out .this is the response that we are getting...
Module devtp: C:\wamp\www\moodle/mod/devtp/version.php was not readable
where,'devtp' is the name of the plug-in directory that we would like to add.
do you think we have missed out on including any related files for our plug-in or is it bcoz we need to include some files that can make the plug-in COMPATIBLE with the current version of MOODLE. Our Moodle VERSION is 1.9.
Awaiting your response. | A simple way to add video to a moodle course (if you dont want to create or invest in plugin) is to create a new 'page' type resource in moodle course.
In HTML code of that page add code for embedding a video.
Video can be hosted on youtube or your own CDN. For own CDN you may have to use video.js |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | Here is Moodle's official Documentation for developing a **new Module**:
<http://docs.moodle.org/en/newmodule>
start with the suggested **template** (download.moodle.org/plugins19/mod/NEWMODULE.zip) to wrap your code with.
You can always look inside **Kaltura.com**'s video plugin code (<http://www.kaltura.org/kaltura-moodle-plugin-installation-guide>) and see how video can be implemented into Moodle. in general. | we now included the version.php file and thus the error
"Module devtp: C:\wamp\www\moodle/mod/devtp/version.php was not readable" is no longer coming. thank you for the help.
But still,our module has not been included under notifications in Moodle.We consulted the MOODLE site for help,
"<http://docs.moodle.org/en/Installing_contributed_modules_or_plugins>"
and followed the instruction:
// Visit your Local Moodle site <http://localhost:8888/moodle19/>
Site Administration
Notifications
Scroll to the bottom of the page and click on "Continue"//
but the fact is that ,neither is our module appearing under notifications and nor is continue coming.
Awaiting your response... |
759,179 | currently the moodle that we are using doesn't have a video plug-in.i have developed a video plug-in for moodle.I would like to add the plug-in to the Moodle software that is being used in our institution.I am new to open source. How to include the plug-in .how do i go about with the integration ,so that i am able to use the video plug-in next time i use moodle.the plug-in has been written in php | 2009/04/17 | [
"https://Stackoverflow.com/questions/759179",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/-1/"
] | Here is Moodle's official Documentation for developing a **new Module**:
<http://docs.moodle.org/en/newmodule>
start with the suggested **template** (download.moodle.org/plugins19/mod/NEWMODULE.zip) to wrap your code with.
You can always look inside **Kaltura.com**'s video plugin code (<http://www.kaltura.org/kaltura-moodle-plugin-installation-guide>) and see how video can be implemented into Moodle. in general. | A simple way to add video to a moodle course (if you dont want to create or invest in plugin) is to create a new 'page' type resource in moodle course.
In HTML code of that page add code for embedding a video.
Video can be hosted on youtube or your own CDN. For own CDN you may have to use video.js |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | I don't think liquid water is needed. My understanding of both NASA's and SpaceX's plan for ISRU is to use the Sabatier process to create the fuel from the Martian atmosphere. They'd bring H2 feed-stock, and combine it with CO2 from the atmosphere in a catalytic reactor to create methane and water. The water would then be electrolyzed into O2 (for oxidized) and H2 (to feed back into the reactor).
More here: <https://en.m.wikipedia.org/wiki/Sabatier_reaction#Manufacturing_propellant_on_Mars>
Edit to add:
The "bring H2 with you" approach was an element of the "Mars Direct" proposal from Zubrin, laid out in his 1996 book "The Case for Mars". This is summarized in the Wikipedia page here: <https://en.wikipedia.org/wiki/Mars_Direct#First_launch>
>
> The first flight of the Ares rocket (not to be confused with the
> similarly named rocket of the now defunct Constellation program) would
> take an unmanned Earth Return Vehicle to Mars after a 6-month cruise
> phase, with a supply of hydrogen, a chemical plant and a small nuclear
> reactor. Once there, a series of chemical reactions (the Sabatier
> reaction coupled with electrolysis) would be used to combine a small
> amount of hydrogen (8 tons) carried by the Earth Return Vehicle with
> the carbon dioxide of the Martian atmosphere to create up to 112
> tonnes of methane and oxygen. This relatively simple
> chemical-engineering procedure was used regularly in the 19th and 20th
> centuries,[8] and would ensure that only 7% of the return propellant
> would need to be carried to the surface of Mars.
>
>
>
Here's a paper form 2001 discussing it in the context of a planned-but-cancelled NASA mission: ["Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars"](http://ufdc.ufl.edu/UF00091523/00106/3j "Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars")
>
> The carbon dioxide used in the reaction will be obtained from the
> Martian atmosphere, but the hydrogen used will be imported from
> Earth.
>
>
>
However, it seems that this approach is now outdated, as it was formulated before we knew much about the presence of water on Mars.
More recent approaches seem to be to use Martian water. For example, there's this paper from 2017 specifically addressing the SpaceX program: ["Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars"](https://arc.aiaa.org/doi/pdfplus/10.2514/6.2017-5335 "Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars") p. 13. This approach assumes a small amount of H2 brought from Earth, followed by more H2 extracted from Martian water, as well as that reclaimed from the Sabatier process itself.
>
> The H2 input may initially be brought from Earth to start up the
> process, but after start-up the H2 will be derived from water
> electrolysis...
>
>
> The input H2O will derive from a water mining
> operation. Water is known to be abundant on Mars, but unlike Earth, it
> occurs in solid state rather than liquid. Water mining for underground
> ice would proceed by employing soil-moving machines analogous to
> strip mining equipment. Alternatively, wells may be drilled to reach
> buried glacial ice, heat and pressurize the water to liquid state,
> and pump the liquid into a storage module.
>
>
>
Another interesting approach would skip water altogether and generate O2 and H2 from hematite, which is abundant on the surface: ["On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process."](https://jour.space/html/issue-5-2015_en.html "On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process.")
Now, opinion time: I suspect that the very earliest missions will still use the "BYOH2" approach. It requires only 7% of the material by mass, and is way simpler, mechanically and technologically, than mining ice or collecting hematite. But once we have a longer-term presence (manned or unmanned), there will be a shift to other approaches. | >
> What's the scientific evidence of water for return trip methalox on Mars?
>
>
>
The Business Insider article [NASA is helping SpaceX scout these 9 places on Mars for landing the first Starship rocket missions](https://www.businessinsider.com/spacex-starship-mars-landing-sites-map-hirise-2019-9) is an interesting read, and mostly documents the electronic "paper" trail of scouting potential landing sites using targeted, stereoscopic HiRise image pairs.
[](https://i.stack.imgur.com/NMyIp.jpg) Click for full size
>
> An elevation map of Mars showing the nine candidate landing sites SpaceX is considering for its first Martian voyages of Starship. NASA/USGS/ESA/DLR/FU Berlin (G. Neukum) via Google Earth Pro; Business Insider
>
>
>
The article points out that the candidate sites all cary a significant possibility of having substantial subsurface frozen water near the surface.
The article mentions one piece of evidence specifically:
>
> Some evidence for this is in the shape of nearby craters, which appear to sink after a meteorite impact because they expose ice to Martian air, which is about 1% as thick as Earth's.
>
>
> Functionally that is a vacuum, causing the now-exposed ice to sublimate away into the air in the same way a block of dry ice does when it warms up.
>
>
>
>
> One line of evidence for ice on Mars are impact sites. Ice exposed to the thin martian air sublimates into a gas and collapses soil around the original crater. [NASA/JPL/University of Arizona; Business Insider](https://www.uahirise.org/ESP_052424_2200)
>
>
> |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | There is an interesting podcast that I listen to - We Martians. Last Nov they had an episode that touches heavily on this. The episode is here: <http://www.wemartians.com/home/015> and it goes into far more detail than I can, but here's a brief summary:
The SHARAD (SHAllow RADar) instrument on the Mars Reconnaissance Orbiter used ground penetrating radar on the area of Mars known as Utopia Planitia. The radar results, while not definitive, strongly suggest "a mixture of ice, air, and dust" in the area. ["SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars"](http://onlinelibrary.wiley.com/doi/10.1002/2016GL070138/abstract "SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars").
This information was presented in context with info from the Phoenix lander. The lander was equipped with a robot arm which dug in the soil. This article describes it further: ["The Dirt on Mars Lander Soil Findings"](https://www.space.com/6918-dirt-mars-lander-soil-findings.html "The Dirt on Mars Lander Soil Findings")
>
> Using its robotic arm, Phoenix dug into the Martian surface to see if
> it could reach the ice below.
>
>
> In one trench, dubbed "Dodo-Goldilocks," the lander exposed what
> mission scientists described as "bright material" about 4 to 5
> centimeters below the surface (a similar patch was seen below the
> lander itself, likely exposed by the spacecraft's landing thrusters).
> Over the next two months, the team watched as Phoenix's cameras showed
> that the material was sublimating away, which would be expected of
> water ice exposed to the Martian atmosphere.
>
>
> The tendency of soil samples scooped up by the lander to clump
> together made it difficult to get the samples into Phoenix's onboard
> instruments, but after several attempts, a sample was coaxed in and
> the lander's detectors confirmed that there was indeed water ice
> hiding under the regolith. The confirmation was originally announced
> on July 31.
>
>
> Interestingly, the ice seems to occur at different depths under the
> surface depending on the terrain. The plains where Phoenix landed
> feature polygonal mounds surrounded by troughs that result from the
> seasonal expansion and contraction of the ice underneath the surface,
> which creates cracks and crevices.
>
>
>
And from this related article: ["Water Ice on Mars Confirmed"](https://www.space.com/5686-water-ice-mars-confirmed.html "Water Ice on Mars Confirmed")
>
> NASA's Phoenix Mars Lander has confirmed the existence of water ice on
> Mars.
>
>
> Mission scientists celebrated the news after a sample of the ice was
> finally delivered to one of the lander's instruments.
>
>
>
later in the article:
>
> "I'm very happy to announce that we've gotten an ice sample," said the
> University of Arizona's William Boynton, co-investigator for Phoenix's
> Thermal and Evolved-Gas Analyzer (TEGA), which heats up samples and
> analyzes the vapors they give off to determine their composition.
>
>
> "We have water," Boynton added. "We've seen evidence for this water
> ice before in observations by the Mars Odyssey orbiter and in
> disappearing chunks observed by Phoenix last month, but this is the
> first time Martian water has been touched and tasted."
>
>
> The news that ice had fallen into TEGA came on Thursday morning,
> surprising scientists who had run into problems delivering a sample of
> the icy dirt because of its unexpected stickiness.
>
>
>
Opinion: I'm not sure any of this is 100% definitive proof of there being sufficient mineable water for producing Methalox, but it does strongly suggest that at least in this part of the planet there is significant water just below the surface.
Future missions will study this issue as well.
The Trace Gas Orbiter may provide more information once it's fully online - it has the ability to detect neutrons[4](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217 "FREND - Fine Resolution Epithermal Neutron Detector") from sub-surface hydrogen (which may or may not be water) and trace H2O in the atmosphere[5](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2216 "ACS - Atmospheric Chemistry Suite").
The ExoMars rover and NASA's Rover 2020 will both carry instruments that can contribute to this.
ExoMars Rover, specifically, will be carrying the WISDOM ground-penetrating radar which should be able to see subsurface ice[6](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2128 "WISDOM - Water Ice and Subsurface Deposit Observation on Mars"), and it's core drill is equipped with Ma-MISS, an infrared spectrometer that should be able to determine the presence of water or ice in the drill site[7](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2133 "Ma_MISS - Mars Multispectral Imager for Subsurface Studies").
NASA's Rover 2020 will also carry the RIMFAX ground penetrating radar[8](https://mars.nasa.gov/mars2020/mission/instruments/rimfax/ "RIMFAX"), as well as other instruments for chemical analysis - I am not sure if any of them are specifically aimed at ice detection. Of related interest is the MOXIE experiment, which will attempt to extract O2 from the martian atmosphere.[9](https://en.wikipedia.org/wiki/Mars_Oxygen_ISRU_Experiment "Mars Oxygen ISRU Experiment") | Some of the [SHARAD](https://en.wikipedia.org/wiki/SHARAD) evidence discussed in [this answer](https://space.stackexchange.com/a/23781/12102) is also described in Phys.org's [Mars ice deposit holds as much water as Lake Superior](https://phys.org/news/2016-11-mars-ice-deposit-lake-superior.html). This image shows evidence of subsurface ice at Utopia Planitia at about 47° N latitude.
[](https://i.stack.imgur.com/OgSOO.jpg)
For comparison, here is some SHARAD data for Mars' northern polar ice cap, [from here](https://photojournal.jpl.nasa.gov/catalog/PIA13164). Note that CO2 ice and H2O ice have very different dielectric properties and can be distinguished using SHARAD's chirped radar.
[](https://i.stack.imgur.com/ajHuk.jpg)
>
> This image shows a cross-section of a portion of the north polar ice cap of Mars, derived from data acquired by the Mars Reconnaissance Orbiter's Shallow Radar (SHARAD), one of six instruments on the spacecraft.
>
>
> The data depict the region's internal ice structure, with annotations describing different layers. The ice depicted in this graphic is approximately 2 kilometers (1.2 miles) thick and 250 kilometers (155 miles) across. White lines show reflection of the radar signal back to the spacecraft. Each line represents a place where a layer sits on top of another. Scientists study how thick the pancake-like layers are, where they bulge and how they tilt up or down to understand what the surface of the ice sheet was like in the past as each new layer was deposited.
>
>
>
---
---
As far as the direct evidence of water (as ice) from Phoenix is concerned, I've found non-paywalled copies of the following papers:
1. Arvidson, R. E. et al. (2009): [Results from the Mars Phoenix Lander Robotic Arm experiment](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.581.4018&rep=rep1&type=pdf)
2. Smith, P. T. et al. (2009): [H2O at the Phoenix Landing Site](http://aolab.phys.dal.ca/publications/science2009a.pdf)
3. [Supporting Online Material](http://science.sciencemag.org/content/sci/suppl/2009/07/02/325.5936.58.DC1/Smith.SOM.pdf) for Smith et al.
The TEGA mass spectroscopy data for mass = 18 AMU shown in Figure S6 of the Supporting Online Material of Smith at al. is a little complicated to interpret/explain, but the melting of ice shown in TEGA's [differential scanning calorimetry](https://en.wikipedia.org/wiki/Differential_scanning_calorimetry) data in Figure S9 of the data is pretty easy to grasp. Once the oven's ramping temperature reached -2°C the sample became "endothermic" and absorbed more heating power for a given change in temperature.
The area under the curve is 0.35 Joules, (or 0.35/4.2 = 0.08 calories). If it were pure ice that value would correspond to only about *one milligram of water* based on a [heat of fusion](https://en.wikipedia.org/wiki/Enthalpy_of_fusion) of 334 J/g.
>
> Fig. S9. TEGA finds ice and aqueous minerals. (A) Thermal analysis for “Wicked Witch” subsurface sample, sublimation lag in the Snow White trench. The endothermic peak with an onset of -2ºC indicates the melting of water ice.
>
>
>
[](https://i.stack.imgur.com/MOlvt.png) |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | Some of the [SHARAD](https://en.wikipedia.org/wiki/SHARAD) evidence discussed in [this answer](https://space.stackexchange.com/a/23781/12102) is also described in Phys.org's [Mars ice deposit holds as much water as Lake Superior](https://phys.org/news/2016-11-mars-ice-deposit-lake-superior.html). This image shows evidence of subsurface ice at Utopia Planitia at about 47° N latitude.
[](https://i.stack.imgur.com/OgSOO.jpg)
For comparison, here is some SHARAD data for Mars' northern polar ice cap, [from here](https://photojournal.jpl.nasa.gov/catalog/PIA13164). Note that CO2 ice and H2O ice have very different dielectric properties and can be distinguished using SHARAD's chirped radar.
[](https://i.stack.imgur.com/ajHuk.jpg)
>
> This image shows a cross-section of a portion of the north polar ice cap of Mars, derived from data acquired by the Mars Reconnaissance Orbiter's Shallow Radar (SHARAD), one of six instruments on the spacecraft.
>
>
> The data depict the region's internal ice structure, with annotations describing different layers. The ice depicted in this graphic is approximately 2 kilometers (1.2 miles) thick and 250 kilometers (155 miles) across. White lines show reflection of the radar signal back to the spacecraft. Each line represents a place where a layer sits on top of another. Scientists study how thick the pancake-like layers are, where they bulge and how they tilt up or down to understand what the surface of the ice sheet was like in the past as each new layer was deposited.
>
>
>
---
---
As far as the direct evidence of water (as ice) from Phoenix is concerned, I've found non-paywalled copies of the following papers:
1. Arvidson, R. E. et al. (2009): [Results from the Mars Phoenix Lander Robotic Arm experiment](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.581.4018&rep=rep1&type=pdf)
2. Smith, P. T. et al. (2009): [H2O at the Phoenix Landing Site](http://aolab.phys.dal.ca/publications/science2009a.pdf)
3. [Supporting Online Material](http://science.sciencemag.org/content/sci/suppl/2009/07/02/325.5936.58.DC1/Smith.SOM.pdf) for Smith et al.
The TEGA mass spectroscopy data for mass = 18 AMU shown in Figure S6 of the Supporting Online Material of Smith at al. is a little complicated to interpret/explain, but the melting of ice shown in TEGA's [differential scanning calorimetry](https://en.wikipedia.org/wiki/Differential_scanning_calorimetry) data in Figure S9 of the data is pretty easy to grasp. Once the oven's ramping temperature reached -2°C the sample became "endothermic" and absorbed more heating power for a given change in temperature.
The area under the curve is 0.35 Joules, (or 0.35/4.2 = 0.08 calories). If it were pure ice that value would correspond to only about *one milligram of water* based on a [heat of fusion](https://en.wikipedia.org/wiki/Enthalpy_of_fusion) of 334 J/g.
>
> Fig. S9. TEGA finds ice and aqueous minerals. (A) Thermal analysis for “Wicked Witch” subsurface sample, sublimation lag in the Snow White trench. The endothermic peak with an onset of -2ºC indicates the melting of water ice.
>
>
>
[](https://i.stack.imgur.com/MOlvt.png) | >
> What's the scientific evidence of water for return trip methalox on Mars?
>
>
>
The Business Insider article [NASA is helping SpaceX scout these 9 places on Mars for landing the first Starship rocket missions](https://www.businessinsider.com/spacex-starship-mars-landing-sites-map-hirise-2019-9) is an interesting read, and mostly documents the electronic "paper" trail of scouting potential landing sites using targeted, stereoscopic HiRise image pairs.
[](https://i.stack.imgur.com/NMyIp.jpg) Click for full size
>
> An elevation map of Mars showing the nine candidate landing sites SpaceX is considering for its first Martian voyages of Starship. NASA/USGS/ESA/DLR/FU Berlin (G. Neukum) via Google Earth Pro; Business Insider
>
>
>
The article points out that the candidate sites all cary a significant possibility of having substantial subsurface frozen water near the surface.
The article mentions one piece of evidence specifically:
>
> Some evidence for this is in the shape of nearby craters, which appear to sink after a meteorite impact because they expose ice to Martian air, which is about 1% as thick as Earth's.
>
>
> Functionally that is a vacuum, causing the now-exposed ice to sublimate away into the air in the same way a block of dry ice does when it warms up.
>
>
>
>
> One line of evidence for ice on Mars are impact sites. Ice exposed to the thin martian air sublimates into a gas and collapses soil around the original crater. [NASA/JPL/University of Arizona; Business Insider](https://www.uahirise.org/ESP_052424_2200)
>
>
> |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | There is an interesting podcast that I listen to - We Martians. Last Nov they had an episode that touches heavily on this. The episode is here: <http://www.wemartians.com/home/015> and it goes into far more detail than I can, but here's a brief summary:
The SHARAD (SHAllow RADar) instrument on the Mars Reconnaissance Orbiter used ground penetrating radar on the area of Mars known as Utopia Planitia. The radar results, while not definitive, strongly suggest "a mixture of ice, air, and dust" in the area. ["SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars"](http://onlinelibrary.wiley.com/doi/10.1002/2016GL070138/abstract "SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars").
This information was presented in context with info from the Phoenix lander. The lander was equipped with a robot arm which dug in the soil. This article describes it further: ["The Dirt on Mars Lander Soil Findings"](https://www.space.com/6918-dirt-mars-lander-soil-findings.html "The Dirt on Mars Lander Soil Findings")
>
> Using its robotic arm, Phoenix dug into the Martian surface to see if
> it could reach the ice below.
>
>
> In one trench, dubbed "Dodo-Goldilocks," the lander exposed what
> mission scientists described as "bright material" about 4 to 5
> centimeters below the surface (a similar patch was seen below the
> lander itself, likely exposed by the spacecraft's landing thrusters).
> Over the next two months, the team watched as Phoenix's cameras showed
> that the material was sublimating away, which would be expected of
> water ice exposed to the Martian atmosphere.
>
>
> The tendency of soil samples scooped up by the lander to clump
> together made it difficult to get the samples into Phoenix's onboard
> instruments, but after several attempts, a sample was coaxed in and
> the lander's detectors confirmed that there was indeed water ice
> hiding under the regolith. The confirmation was originally announced
> on July 31.
>
>
> Interestingly, the ice seems to occur at different depths under the
> surface depending on the terrain. The plains where Phoenix landed
> feature polygonal mounds surrounded by troughs that result from the
> seasonal expansion and contraction of the ice underneath the surface,
> which creates cracks and crevices.
>
>
>
And from this related article: ["Water Ice on Mars Confirmed"](https://www.space.com/5686-water-ice-mars-confirmed.html "Water Ice on Mars Confirmed")
>
> NASA's Phoenix Mars Lander has confirmed the existence of water ice on
> Mars.
>
>
> Mission scientists celebrated the news after a sample of the ice was
> finally delivered to one of the lander's instruments.
>
>
>
later in the article:
>
> "I'm very happy to announce that we've gotten an ice sample," said the
> University of Arizona's William Boynton, co-investigator for Phoenix's
> Thermal and Evolved-Gas Analyzer (TEGA), which heats up samples and
> analyzes the vapors they give off to determine their composition.
>
>
> "We have water," Boynton added. "We've seen evidence for this water
> ice before in observations by the Mars Odyssey orbiter and in
> disappearing chunks observed by Phoenix last month, but this is the
> first time Martian water has been touched and tasted."
>
>
> The news that ice had fallen into TEGA came on Thursday morning,
> surprising scientists who had run into problems delivering a sample of
> the icy dirt because of its unexpected stickiness.
>
>
>
Opinion: I'm not sure any of this is 100% definitive proof of there being sufficient mineable water for producing Methalox, but it does strongly suggest that at least in this part of the planet there is significant water just below the surface.
Future missions will study this issue as well.
The Trace Gas Orbiter may provide more information once it's fully online - it has the ability to detect neutrons[4](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217 "FREND - Fine Resolution Epithermal Neutron Detector") from sub-surface hydrogen (which may or may not be water) and trace H2O in the atmosphere[5](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2216 "ACS - Atmospheric Chemistry Suite").
The ExoMars rover and NASA's Rover 2020 will both carry instruments that can contribute to this.
ExoMars Rover, specifically, will be carrying the WISDOM ground-penetrating radar which should be able to see subsurface ice[6](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2128 "WISDOM - Water Ice and Subsurface Deposit Observation on Mars"), and it's core drill is equipped with Ma-MISS, an infrared spectrometer that should be able to determine the presence of water or ice in the drill site[7](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2133 "Ma_MISS - Mars Multispectral Imager for Subsurface Studies").
NASA's Rover 2020 will also carry the RIMFAX ground penetrating radar[8](https://mars.nasa.gov/mars2020/mission/instruments/rimfax/ "RIMFAX"), as well as other instruments for chemical analysis - I am not sure if any of them are specifically aimed at ice detection. Of related interest is the MOXIE experiment, which will attempt to extract O2 from the martian atmosphere.[9](https://en.wikipedia.org/wiki/Mars_Oxygen_ISRU_Experiment "Mars Oxygen ISRU Experiment") | I don't think liquid water is needed. My understanding of both NASA's and SpaceX's plan for ISRU is to use the Sabatier process to create the fuel from the Martian atmosphere. They'd bring H2 feed-stock, and combine it with CO2 from the atmosphere in a catalytic reactor to create methane and water. The water would then be electrolyzed into O2 (for oxidized) and H2 (to feed back into the reactor).
More here: <https://en.m.wikipedia.org/wiki/Sabatier_reaction#Manufacturing_propellant_on_Mars>
Edit to add:
The "bring H2 with you" approach was an element of the "Mars Direct" proposal from Zubrin, laid out in his 1996 book "The Case for Mars". This is summarized in the Wikipedia page here: <https://en.wikipedia.org/wiki/Mars_Direct#First_launch>
>
> The first flight of the Ares rocket (not to be confused with the
> similarly named rocket of the now defunct Constellation program) would
> take an unmanned Earth Return Vehicle to Mars after a 6-month cruise
> phase, with a supply of hydrogen, a chemical plant and a small nuclear
> reactor. Once there, a series of chemical reactions (the Sabatier
> reaction coupled with electrolysis) would be used to combine a small
> amount of hydrogen (8 tons) carried by the Earth Return Vehicle with
> the carbon dioxide of the Martian atmosphere to create up to 112
> tonnes of methane and oxygen. This relatively simple
> chemical-engineering procedure was used regularly in the 19th and 20th
> centuries,[8] and would ensure that only 7% of the return propellant
> would need to be carried to the surface of Mars.
>
>
>
Here's a paper form 2001 discussing it in the context of a planned-but-cancelled NASA mission: ["Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars"](http://ufdc.ufl.edu/UF00091523/00106/3j "Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars")
>
> The carbon dioxide used in the reaction will be obtained from the
> Martian atmosphere, but the hydrogen used will be imported from
> Earth.
>
>
>
However, it seems that this approach is now outdated, as it was formulated before we knew much about the presence of water on Mars.
More recent approaches seem to be to use Martian water. For example, there's this paper from 2017 specifically addressing the SpaceX program: ["Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars"](https://arc.aiaa.org/doi/pdfplus/10.2514/6.2017-5335 "Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars") p. 13. This approach assumes a small amount of H2 brought from Earth, followed by more H2 extracted from Martian water, as well as that reclaimed from the Sabatier process itself.
>
> The H2 input may initially be brought from Earth to start up the
> process, but after start-up the H2 will be derived from water
> electrolysis...
>
>
> The input H2O will derive from a water mining
> operation. Water is known to be abundant on Mars, but unlike Earth, it
> occurs in solid state rather than liquid. Water mining for underground
> ice would proceed by employing soil-moving machines analogous to
> strip mining equipment. Alternatively, wells may be drilled to reach
> buried glacial ice, heat and pressurize the water to liquid state,
> and pump the liquid into a storage module.
>
>
>
Another interesting approach would skip water altogether and generate O2 and H2 from hematite, which is abundant on the surface: ["On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process."](https://jour.space/html/issue-5-2015_en.html "On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process.")
Now, opinion time: I suspect that the very earliest missions will still use the "BYOH2" approach. It requires only 7% of the material by mass, and is way simpler, mechanically and technologically, than mining ice or collecting hematite. But once we have a longer-term presence (manned or unmanned), there will be a shift to other approaches. |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | Some of the [SHARAD](https://en.wikipedia.org/wiki/SHARAD) evidence discussed in [this answer](https://space.stackexchange.com/a/23781/12102) is also described in Phys.org's [Mars ice deposit holds as much water as Lake Superior](https://phys.org/news/2016-11-mars-ice-deposit-lake-superior.html). This image shows evidence of subsurface ice at Utopia Planitia at about 47° N latitude.
[](https://i.stack.imgur.com/OgSOO.jpg)
For comparison, here is some SHARAD data for Mars' northern polar ice cap, [from here](https://photojournal.jpl.nasa.gov/catalog/PIA13164). Note that CO2 ice and H2O ice have very different dielectric properties and can be distinguished using SHARAD's chirped radar.
[](https://i.stack.imgur.com/ajHuk.jpg)
>
> This image shows a cross-section of a portion of the north polar ice cap of Mars, derived from data acquired by the Mars Reconnaissance Orbiter's Shallow Radar (SHARAD), one of six instruments on the spacecraft.
>
>
> The data depict the region's internal ice structure, with annotations describing different layers. The ice depicted in this graphic is approximately 2 kilometers (1.2 miles) thick and 250 kilometers (155 miles) across. White lines show reflection of the radar signal back to the spacecraft. Each line represents a place where a layer sits on top of another. Scientists study how thick the pancake-like layers are, where they bulge and how they tilt up or down to understand what the surface of the ice sheet was like in the past as each new layer was deposited.
>
>
>
---
---
As far as the direct evidence of water (as ice) from Phoenix is concerned, I've found non-paywalled copies of the following papers:
1. Arvidson, R. E. et al. (2009): [Results from the Mars Phoenix Lander Robotic Arm experiment](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.581.4018&rep=rep1&type=pdf)
2. Smith, P. T. et al. (2009): [H2O at the Phoenix Landing Site](http://aolab.phys.dal.ca/publications/science2009a.pdf)
3. [Supporting Online Material](http://science.sciencemag.org/content/sci/suppl/2009/07/02/325.5936.58.DC1/Smith.SOM.pdf) for Smith et al.
The TEGA mass spectroscopy data for mass = 18 AMU shown in Figure S6 of the Supporting Online Material of Smith at al. is a little complicated to interpret/explain, but the melting of ice shown in TEGA's [differential scanning calorimetry](https://en.wikipedia.org/wiki/Differential_scanning_calorimetry) data in Figure S9 of the data is pretty easy to grasp. Once the oven's ramping temperature reached -2°C the sample became "endothermic" and absorbed more heating power for a given change in temperature.
The area under the curve is 0.35 Joules, (or 0.35/4.2 = 0.08 calories). If it were pure ice that value would correspond to only about *one milligram of water* based on a [heat of fusion](https://en.wikipedia.org/wiki/Enthalpy_of_fusion) of 334 J/g.
>
> Fig. S9. TEGA finds ice and aqueous minerals. (A) Thermal analysis for “Wicked Witch” subsurface sample, sublimation lag in the Snow White trench. The endothermic peak with an onset of -2ºC indicates the melting of water ice.
>
>
>
[](https://i.stack.imgur.com/MOlvt.png) | The strongest evidence would probably be that the [Phoenix lander](https://en.m.wikipedia.org/wiki/Phoenix_(spacecraft)) actually dug some up, which suggests that there is enough water present to be useful for colonization.
However, jgalak’s answer is also correct. Mining local ice is important for long term plans to build an independent colony, but for early missions, a pump and a hydrogen tank is much lighter and less complex than mining equipment.
Note that hydrogen is only a small part of the fuel / oxidizer mix by mass. The reaction CH4 + 2O2 => 2H2O + CO2 uses 4 parts hydrogen to 14 carbon and 64 oxygen. Even if you bring the hydrogen from Earth, using local carbon and oxygen reduces imported fuel mass by over 95 percent.
If storage is a serious problem, you can also bring water from earth for a more modest 56 percent reduction, though you can accept quite a lot of hydrogen leakage before that becomes the better option. |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | I don't think liquid water is needed. My understanding of both NASA's and SpaceX's plan for ISRU is to use the Sabatier process to create the fuel from the Martian atmosphere. They'd bring H2 feed-stock, and combine it with CO2 from the atmosphere in a catalytic reactor to create methane and water. The water would then be electrolyzed into O2 (for oxidized) and H2 (to feed back into the reactor).
More here: <https://en.m.wikipedia.org/wiki/Sabatier_reaction#Manufacturing_propellant_on_Mars>
Edit to add:
The "bring H2 with you" approach was an element of the "Mars Direct" proposal from Zubrin, laid out in his 1996 book "The Case for Mars". This is summarized in the Wikipedia page here: <https://en.wikipedia.org/wiki/Mars_Direct#First_launch>
>
> The first flight of the Ares rocket (not to be confused with the
> similarly named rocket of the now defunct Constellation program) would
> take an unmanned Earth Return Vehicle to Mars after a 6-month cruise
> phase, with a supply of hydrogen, a chemical plant and a small nuclear
> reactor. Once there, a series of chemical reactions (the Sabatier
> reaction coupled with electrolysis) would be used to combine a small
> amount of hydrogen (8 tons) carried by the Earth Return Vehicle with
> the carbon dioxide of the Martian atmosphere to create up to 112
> tonnes of methane and oxygen. This relatively simple
> chemical-engineering procedure was used regularly in the 19th and 20th
> centuries,[8] and would ensure that only 7% of the return propellant
> would need to be carried to the surface of Mars.
>
>
>
Here's a paper form 2001 discussing it in the context of a planned-but-cancelled NASA mission: ["Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars"](http://ufdc.ufl.edu/UF00091523/00106/3j "Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars")
>
> The carbon dioxide used in the reaction will be obtained from the
> Martian atmosphere, but the hydrogen used will be imported from
> Earth.
>
>
>
However, it seems that this approach is now outdated, as it was formulated before we knew much about the presence of water on Mars.
More recent approaches seem to be to use Martian water. For example, there's this paper from 2017 specifically addressing the SpaceX program: ["Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars"](https://arc.aiaa.org/doi/pdfplus/10.2514/6.2017-5335 "Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars") p. 13. This approach assumes a small amount of H2 brought from Earth, followed by more H2 extracted from Martian water, as well as that reclaimed from the Sabatier process itself.
>
> The H2 input may initially be brought from Earth to start up the
> process, but after start-up the H2 will be derived from water
> electrolysis...
>
>
> The input H2O will derive from a water mining
> operation. Water is known to be abundant on Mars, but unlike Earth, it
> occurs in solid state rather than liquid. Water mining for underground
> ice would proceed by employing soil-moving machines analogous to
> strip mining equipment. Alternatively, wells may be drilled to reach
> buried glacial ice, heat and pressurize the water to liquid state,
> and pump the liquid into a storage module.
>
>
>
Another interesting approach would skip water altogether and generate O2 and H2 from hematite, which is abundant on the surface: ["On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process."](https://jour.space/html/issue-5-2015_en.html "On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process.")
Now, opinion time: I suspect that the very earliest missions will still use the "BYOH2" approach. It requires only 7% of the material by mass, and is way simpler, mechanically and technologically, than mining ice or collecting hematite. But once we have a longer-term presence (manned or unmanned), there will be a shift to other approaches. | The strongest evidence would probably be that the [Phoenix lander](https://en.m.wikipedia.org/wiki/Phoenix_(spacecraft)) actually dug some up, which suggests that there is enough water present to be useful for colonization.
However, jgalak’s answer is also correct. Mining local ice is important for long term plans to build an independent colony, but for early missions, a pump and a hydrogen tank is much lighter and less complex than mining equipment.
Note that hydrogen is only a small part of the fuel / oxidizer mix by mass. The reaction CH4 + 2O2 => 2H2O + CO2 uses 4 parts hydrogen to 14 carbon and 64 oxygen. Even if you bring the hydrogen from Earth, using local carbon and oxygen reduces imported fuel mass by over 95 percent.
If storage is a serious problem, you can also bring water from earth for a more modest 56 percent reduction, though you can accept quite a lot of hydrogen leakage before that becomes the better option. |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | I don't think liquid water is needed. My understanding of both NASA's and SpaceX's plan for ISRU is to use the Sabatier process to create the fuel from the Martian atmosphere. They'd bring H2 feed-stock, and combine it with CO2 from the atmosphere in a catalytic reactor to create methane and water. The water would then be electrolyzed into O2 (for oxidized) and H2 (to feed back into the reactor).
More here: <https://en.m.wikipedia.org/wiki/Sabatier_reaction#Manufacturing_propellant_on_Mars>
Edit to add:
The "bring H2 with you" approach was an element of the "Mars Direct" proposal from Zubrin, laid out in his 1996 book "The Case for Mars". This is summarized in the Wikipedia page here: <https://en.wikipedia.org/wiki/Mars_Direct#First_launch>
>
> The first flight of the Ares rocket (not to be confused with the
> similarly named rocket of the now defunct Constellation program) would
> take an unmanned Earth Return Vehicle to Mars after a 6-month cruise
> phase, with a supply of hydrogen, a chemical plant and a small nuclear
> reactor. Once there, a series of chemical reactions (the Sabatier
> reaction coupled with electrolysis) would be used to combine a small
> amount of hydrogen (8 tons) carried by the Earth Return Vehicle with
> the carbon dioxide of the Martian atmosphere to create up to 112
> tonnes of methane and oxygen. This relatively simple
> chemical-engineering procedure was used regularly in the 19th and 20th
> centuries,[8] and would ensure that only 7% of the return propellant
> would need to be carried to the surface of Mars.
>
>
>
Here's a paper form 2001 discussing it in the context of a planned-but-cancelled NASA mission: ["Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars"](http://ufdc.ufl.edu/UF00091523/00106/3j "Sizing of a Combined Sabatier Reaction and Water Electrolysis Plant for Use in In-Situ Resource Utilization on Mars")
>
> The carbon dioxide used in the reaction will be obtained from the
> Martian atmosphere, but the hydrogen used will be imported from
> Earth.
>
>
>
However, it seems that this approach is now outdated, as it was formulated before we knew much about the presence of water on Mars.
More recent approaches seem to be to use Martian water. For example, there's this paper from 2017 specifically addressing the SpaceX program: ["Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars"](https://arc.aiaa.org/doi/pdfplus/10.2514/6.2017-5335 "Proposed ITS Pressurized Cargo Modules To Initiate a Chemical Industry on Mars") p. 13. This approach assumes a small amount of H2 brought from Earth, followed by more H2 extracted from Martian water, as well as that reclaimed from the Sabatier process itself.
>
> The H2 input may initially be brought from Earth to start up the
> process, but after start-up the H2 will be derived from water
> electrolysis...
>
>
> The input H2O will derive from a water mining
> operation. Water is known to be abundant on Mars, but unlike Earth, it
> occurs in solid state rather than liquid. Water mining for underground
> ice would proceed by employing soil-moving machines analogous to
> strip mining equipment. Alternatively, wells may be drilled to reach
> buried glacial ice, heat and pressurize the water to liquid state,
> and pump the liquid into a storage module.
>
>
>
Another interesting approach would skip water altogether and generate O2 and H2 from hematite, which is abundant on the surface: ["On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process."](https://jour.space/html/issue-5-2015_en.html "On the in situ production of oxygen and hydrogen from martian hematite deposits via a two-step thermochemical CO2/H2O splitting process.")
Now, opinion time: I suspect that the very earliest missions will still use the "BYOH2" approach. It requires only 7% of the material by mass, and is way simpler, mechanically and technologically, than mining ice or collecting hematite. But once we have a longer-term presence (manned or unmanned), there will be a shift to other approaches. | There are two possibilities. The first, proposed by Robert Zubrin in the Case for Mars, is as has been suggested, bring a feedstock of Hydrogen, and use it to make the fuel. Hydrogen is by far the lightest part of a methalox system, and could easily be included.
The second is using liquid water to make the hydrogen. There's a [large number of sources](https://en.wikipedia.org/wiki/Water_on_Mars#Present_water_ice) that support that there is liquid water near the surface of Mars. The following image shows a rough distribution of the water on Mars near the surface, based on neutron flux data. The poles have a much higher portion that is water ice. These have been partially confirmed by the landers on the surface. One of the key objective of any lander is to provide ground truth to help verify orbital observations.
Bottom line, we could either bring hydrogen (Likely for the first missions), or look for water ice to use, but either will likely get us what we need to make rocket fuel to get home.
[](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Water_equivalent_hydrogen_abundance_in_the_lower_latitudes_of_Mars_01.jpg/1200px-Water_equivalent_hydrogen_abundance_in_the_lower_latitudes_of_Mars_01.jpg) |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | There is an interesting podcast that I listen to - We Martians. Last Nov they had an episode that touches heavily on this. The episode is here: <http://www.wemartians.com/home/015> and it goes into far more detail than I can, but here's a brief summary:
The SHARAD (SHAllow RADar) instrument on the Mars Reconnaissance Orbiter used ground penetrating radar on the area of Mars known as Utopia Planitia. The radar results, while not definitive, strongly suggest "a mixture of ice, air, and dust" in the area. ["SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars"](http://onlinelibrary.wiley.com/doi/10.1002/2016GL070138/abstract "SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars").
This information was presented in context with info from the Phoenix lander. The lander was equipped with a robot arm which dug in the soil. This article describes it further: ["The Dirt on Mars Lander Soil Findings"](https://www.space.com/6918-dirt-mars-lander-soil-findings.html "The Dirt on Mars Lander Soil Findings")
>
> Using its robotic arm, Phoenix dug into the Martian surface to see if
> it could reach the ice below.
>
>
> In one trench, dubbed "Dodo-Goldilocks," the lander exposed what
> mission scientists described as "bright material" about 4 to 5
> centimeters below the surface (a similar patch was seen below the
> lander itself, likely exposed by the spacecraft's landing thrusters).
> Over the next two months, the team watched as Phoenix's cameras showed
> that the material was sublimating away, which would be expected of
> water ice exposed to the Martian atmosphere.
>
>
> The tendency of soil samples scooped up by the lander to clump
> together made it difficult to get the samples into Phoenix's onboard
> instruments, but after several attempts, a sample was coaxed in and
> the lander's detectors confirmed that there was indeed water ice
> hiding under the regolith. The confirmation was originally announced
> on July 31.
>
>
> Interestingly, the ice seems to occur at different depths under the
> surface depending on the terrain. The plains where Phoenix landed
> feature polygonal mounds surrounded by troughs that result from the
> seasonal expansion and contraction of the ice underneath the surface,
> which creates cracks and crevices.
>
>
>
And from this related article: ["Water Ice on Mars Confirmed"](https://www.space.com/5686-water-ice-mars-confirmed.html "Water Ice on Mars Confirmed")
>
> NASA's Phoenix Mars Lander has confirmed the existence of water ice on
> Mars.
>
>
> Mission scientists celebrated the news after a sample of the ice was
> finally delivered to one of the lander's instruments.
>
>
>
later in the article:
>
> "I'm very happy to announce that we've gotten an ice sample," said the
> University of Arizona's William Boynton, co-investigator for Phoenix's
> Thermal and Evolved-Gas Analyzer (TEGA), which heats up samples and
> analyzes the vapors they give off to determine their composition.
>
>
> "We have water," Boynton added. "We've seen evidence for this water
> ice before in observations by the Mars Odyssey orbiter and in
> disappearing chunks observed by Phoenix last month, but this is the
> first time Martian water has been touched and tasted."
>
>
> The news that ice had fallen into TEGA came on Thursday morning,
> surprising scientists who had run into problems delivering a sample of
> the icy dirt because of its unexpected stickiness.
>
>
>
Opinion: I'm not sure any of this is 100% definitive proof of there being sufficient mineable water for producing Methalox, but it does strongly suggest that at least in this part of the planet there is significant water just below the surface.
Future missions will study this issue as well.
The Trace Gas Orbiter may provide more information once it's fully online - it has the ability to detect neutrons[4](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217 "FREND - Fine Resolution Epithermal Neutron Detector") from sub-surface hydrogen (which may or may not be water) and trace H2O in the atmosphere[5](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2216 "ACS - Atmospheric Chemistry Suite").
The ExoMars rover and NASA's Rover 2020 will both carry instruments that can contribute to this.
ExoMars Rover, specifically, will be carrying the WISDOM ground-penetrating radar which should be able to see subsurface ice[6](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2128 "WISDOM - Water Ice and Subsurface Deposit Observation on Mars"), and it's core drill is equipped with Ma-MISS, an infrared spectrometer that should be able to determine the presence of water or ice in the drill site[7](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2133 "Ma_MISS - Mars Multispectral Imager for Subsurface Studies").
NASA's Rover 2020 will also carry the RIMFAX ground penetrating radar[8](https://mars.nasa.gov/mars2020/mission/instruments/rimfax/ "RIMFAX"), as well as other instruments for chemical analysis - I am not sure if any of them are specifically aimed at ice detection. Of related interest is the MOXIE experiment, which will attempt to extract O2 from the martian atmosphere.[9](https://en.wikipedia.org/wiki/Mars_Oxygen_ISRU_Experiment "Mars Oxygen ISRU Experiment") | There are two possibilities. The first, proposed by Robert Zubrin in the Case for Mars, is as has been suggested, bring a feedstock of Hydrogen, and use it to make the fuel. Hydrogen is by far the lightest part of a methalox system, and could easily be included.
The second is using liquid water to make the hydrogen. There's a [large number of sources](https://en.wikipedia.org/wiki/Water_on_Mars#Present_water_ice) that support that there is liquid water near the surface of Mars. The following image shows a rough distribution of the water on Mars near the surface, based on neutron flux data. The poles have a much higher portion that is water ice. These have been partially confirmed by the landers on the surface. One of the key objective of any lander is to provide ground truth to help verify orbital observations.
Bottom line, we could either bring hydrogen (Likely for the first missions), or look for water ice to use, but either will likely get us what we need to make rocket fuel to get home.
[](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Water_equivalent_hydrogen_abundance_in_the_lower_latitudes_of_Mars_01.jpg/1200px-Water_equivalent_hydrogen_abundance_in_the_lower_latitudes_of_Mars_01.jpg) |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | There is an interesting podcast that I listen to - We Martians. Last Nov they had an episode that touches heavily on this. The episode is here: <http://www.wemartians.com/home/015> and it goes into far more detail than I can, but here's a brief summary:
The SHARAD (SHAllow RADar) instrument on the Mars Reconnaissance Orbiter used ground penetrating radar on the area of Mars known as Utopia Planitia. The radar results, while not definitive, strongly suggest "a mixture of ice, air, and dust" in the area. ["SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars"](http://onlinelibrary.wiley.com/doi/10.1002/2016GL070138/abstract "SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars").
This information was presented in context with info from the Phoenix lander. The lander was equipped with a robot arm which dug in the soil. This article describes it further: ["The Dirt on Mars Lander Soil Findings"](https://www.space.com/6918-dirt-mars-lander-soil-findings.html "The Dirt on Mars Lander Soil Findings")
>
> Using its robotic arm, Phoenix dug into the Martian surface to see if
> it could reach the ice below.
>
>
> In one trench, dubbed "Dodo-Goldilocks," the lander exposed what
> mission scientists described as "bright material" about 4 to 5
> centimeters below the surface (a similar patch was seen below the
> lander itself, likely exposed by the spacecraft's landing thrusters).
> Over the next two months, the team watched as Phoenix's cameras showed
> that the material was sublimating away, which would be expected of
> water ice exposed to the Martian atmosphere.
>
>
> The tendency of soil samples scooped up by the lander to clump
> together made it difficult to get the samples into Phoenix's onboard
> instruments, but after several attempts, a sample was coaxed in and
> the lander's detectors confirmed that there was indeed water ice
> hiding under the regolith. The confirmation was originally announced
> on July 31.
>
>
> Interestingly, the ice seems to occur at different depths under the
> surface depending on the terrain. The plains where Phoenix landed
> feature polygonal mounds surrounded by troughs that result from the
> seasonal expansion and contraction of the ice underneath the surface,
> which creates cracks and crevices.
>
>
>
And from this related article: ["Water Ice on Mars Confirmed"](https://www.space.com/5686-water-ice-mars-confirmed.html "Water Ice on Mars Confirmed")
>
> NASA's Phoenix Mars Lander has confirmed the existence of water ice on
> Mars.
>
>
> Mission scientists celebrated the news after a sample of the ice was
> finally delivered to one of the lander's instruments.
>
>
>
later in the article:
>
> "I'm very happy to announce that we've gotten an ice sample," said the
> University of Arizona's William Boynton, co-investigator for Phoenix's
> Thermal and Evolved-Gas Analyzer (TEGA), which heats up samples and
> analyzes the vapors they give off to determine their composition.
>
>
> "We have water," Boynton added. "We've seen evidence for this water
> ice before in observations by the Mars Odyssey orbiter and in
> disappearing chunks observed by Phoenix last month, but this is the
> first time Martian water has been touched and tasted."
>
>
> The news that ice had fallen into TEGA came on Thursday morning,
> surprising scientists who had run into problems delivering a sample of
> the icy dirt because of its unexpected stickiness.
>
>
>
Opinion: I'm not sure any of this is 100% definitive proof of there being sufficient mineable water for producing Methalox, but it does strongly suggest that at least in this part of the planet there is significant water just below the surface.
Future missions will study this issue as well.
The Trace Gas Orbiter may provide more information once it's fully online - it has the ability to detect neutrons[4](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217 "FREND - Fine Resolution Epithermal Neutron Detector") from sub-surface hydrogen (which may or may not be water) and trace H2O in the atmosphere[5](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2216 "ACS - Atmospheric Chemistry Suite").
The ExoMars rover and NASA's Rover 2020 will both carry instruments that can contribute to this.
ExoMars Rover, specifically, will be carrying the WISDOM ground-penetrating radar which should be able to see subsurface ice[6](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2128 "WISDOM - Water Ice and Subsurface Deposit Observation on Mars"), and it's core drill is equipped with Ma-MISS, an infrared spectrometer that should be able to determine the presence of water or ice in the drill site[7](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2133 "Ma_MISS - Mars Multispectral Imager for Subsurface Studies").
NASA's Rover 2020 will also carry the RIMFAX ground penetrating radar[8](https://mars.nasa.gov/mars2020/mission/instruments/rimfax/ "RIMFAX"), as well as other instruments for chemical analysis - I am not sure if any of them are specifically aimed at ice detection. Of related interest is the MOXIE experiment, which will attempt to extract O2 from the martian atmosphere.[9](https://en.wikipedia.org/wiki/Mars_Oxygen_ISRU_Experiment "Mars Oxygen ISRU Experiment") | >
> What's the scientific evidence of water for return trip methalox on Mars?
>
>
>
The Business Insider article [NASA is helping SpaceX scout these 9 places on Mars for landing the first Starship rocket missions](https://www.businessinsider.com/spacex-starship-mars-landing-sites-map-hirise-2019-9) is an interesting read, and mostly documents the electronic "paper" trail of scouting potential landing sites using targeted, stereoscopic HiRise image pairs.
[](https://i.stack.imgur.com/NMyIp.jpg) Click for full size
>
> An elevation map of Mars showing the nine candidate landing sites SpaceX is considering for its first Martian voyages of Starship. NASA/USGS/ESA/DLR/FU Berlin (G. Neukum) via Google Earth Pro; Business Insider
>
>
>
The article points out that the candidate sites all cary a significant possibility of having substantial subsurface frozen water near the surface.
The article mentions one piece of evidence specifically:
>
> Some evidence for this is in the shape of nearby craters, which appear to sink after a meteorite impact because they expose ice to Martian air, which is about 1% as thick as Earth's.
>
>
> Functionally that is a vacuum, causing the now-exposed ice to sublimate away into the air in the same way a block of dry ice does when it warms up.
>
>
>
>
> One line of evidence for ice on Mars are impact sites. Ice exposed to the thin martian air sublimates into a gas and collapses soil around the original crater. [NASA/JPL/University of Arizona; Business Insider](https://www.uahirise.org/ESP_052424_2200)
>
>
> |
23,763 | **EDIT:** I am not asking if you think finding water is necessary for a return flight. I'm asking for the scientific evidence that there is mineable water on Mars that could be used for this purpose. Please direct your answers to the question as asked.
If one is inclined to write an answer about the necessity of finding mineable water on Mars for this purpose, one can always ask it as a new and separate question, and answer there.
---
Reviewing:
1. Nature Geoscience [Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water](https://www.nature.com/articles/s41561-017-0012-5)
2. ibid. [Supplementary data](https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-017-0012-5/MediaObjects/41561_2017_12_MOESM1_ESM.pdf)
3. NASA JPL [Recurring Martian Streaks: Flowing Sand, Not Water?](https://www.jpl.nasa.gov/news/news.php?release=2017-299)
4. Space.com [Weird Dark Streaks on Mars May Not Be Flowing Water After All](https://www.space.com/38843-mars-dark-streaks-not-water.html) (a relatively concise summary)
5. Wikipedia [Seasonal flows on warm Martian slopes](https://en.wikipedia.org/wiki/Seasonal_flows_on_warm_Martian_slopes)
It seems that one significant body of evidence for accessible subsurface water on Mars that could be potentially used along with atmospheric CO2 to produce methalox propellants (CH4 and LOX) is substantially called into question.
**THE QUESTION:** What is the (remaining) body of scientific evidence of potential, mineable sources of water for return trip propellant production on Mars?
---
As *just one example* of a plan to use water on Mars to produce methane, see Elon Musk's article [Making Humans a Multi-Planetary Species](http://online.liebertpub.com/doi/full/10.1089/space.2017.29009.emu) or the [video of the](https://youtu.be/tdUX3ypDVwI?t=1996) 29-Sep-2017 talk at the International Astronautical Congress (IAC) in Adelaide, Australia, starting at `33:20`.
From Spaceflight Now's [SpaceX’s Elon Musk announces vision for colonizing Mars](https://spaceflightnow.com/2016/09/27/spacexs-elon-musk-announces-vision-for-colonizing-mars/):
>
> The moon is not an good option because it lacks an atmosphere, has weaker gravity than Mars, and lacks resources like large reservoirs of frozen ice and carbon dioxide that could be converted into water, air and rocket propellant on the red planet.
>
>
>
---
**below:** Warm Season Flows on Slope in Newton Crater (animated), from [here](https://en.wikipedia.org/wiki/File:Warm_Season_Flows_on_Slope_in_Newton_Crater_(animated).gif).
[](https://i.stack.imgur.com/9RIQ2.gif) | 2017/11/21 | [
"https://space.stackexchange.com/questions/23763",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/12102/"
] | There is an interesting podcast that I listen to - We Martians. Last Nov they had an episode that touches heavily on this. The episode is here: <http://www.wemartians.com/home/015> and it goes into far more detail than I can, but here's a brief summary:
The SHARAD (SHAllow RADar) instrument on the Mars Reconnaissance Orbiter used ground penetrating radar on the area of Mars known as Utopia Planitia. The radar results, while not definitive, strongly suggest "a mixture of ice, air, and dust" in the area. ["SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars"](http://onlinelibrary.wiley.com/doi/10.1002/2016GL070138/abstract "SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars").
This information was presented in context with info from the Phoenix lander. The lander was equipped with a robot arm which dug in the soil. This article describes it further: ["The Dirt on Mars Lander Soil Findings"](https://www.space.com/6918-dirt-mars-lander-soil-findings.html "The Dirt on Mars Lander Soil Findings")
>
> Using its robotic arm, Phoenix dug into the Martian surface to see if
> it could reach the ice below.
>
>
> In one trench, dubbed "Dodo-Goldilocks," the lander exposed what
> mission scientists described as "bright material" about 4 to 5
> centimeters below the surface (a similar patch was seen below the
> lander itself, likely exposed by the spacecraft's landing thrusters).
> Over the next two months, the team watched as Phoenix's cameras showed
> that the material was sublimating away, which would be expected of
> water ice exposed to the Martian atmosphere.
>
>
> The tendency of soil samples scooped up by the lander to clump
> together made it difficult to get the samples into Phoenix's onboard
> instruments, but after several attempts, a sample was coaxed in and
> the lander's detectors confirmed that there was indeed water ice
> hiding under the regolith. The confirmation was originally announced
> on July 31.
>
>
> Interestingly, the ice seems to occur at different depths under the
> surface depending on the terrain. The plains where Phoenix landed
> feature polygonal mounds surrounded by troughs that result from the
> seasonal expansion and contraction of the ice underneath the surface,
> which creates cracks and crevices.
>
>
>
And from this related article: ["Water Ice on Mars Confirmed"](https://www.space.com/5686-water-ice-mars-confirmed.html "Water Ice on Mars Confirmed")
>
> NASA's Phoenix Mars Lander has confirmed the existence of water ice on
> Mars.
>
>
> Mission scientists celebrated the news after a sample of the ice was
> finally delivered to one of the lander's instruments.
>
>
>
later in the article:
>
> "I'm very happy to announce that we've gotten an ice sample," said the
> University of Arizona's William Boynton, co-investigator for Phoenix's
> Thermal and Evolved-Gas Analyzer (TEGA), which heats up samples and
> analyzes the vapors they give off to determine their composition.
>
>
> "We have water," Boynton added. "We've seen evidence for this water
> ice before in observations by the Mars Odyssey orbiter and in
> disappearing chunks observed by Phoenix last month, but this is the
> first time Martian water has been touched and tasted."
>
>
> The news that ice had fallen into TEGA came on Thursday morning,
> surprising scientists who had run into problems delivering a sample of
> the icy dirt because of its unexpected stickiness.
>
>
>
Opinion: I'm not sure any of this is 100% definitive proof of there being sufficient mineable water for producing Methalox, but it does strongly suggest that at least in this part of the planet there is significant water just below the surface.
Future missions will study this issue as well.
The Trace Gas Orbiter may provide more information once it's fully online - it has the ability to detect neutrons[4](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217 "FREND - Fine Resolution Epithermal Neutron Detector") from sub-surface hydrogen (which may or may not be water) and trace H2O in the atmosphere[5](http://exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2216 "ACS - Atmospheric Chemistry Suite").
The ExoMars rover and NASA's Rover 2020 will both carry instruments that can contribute to this.
ExoMars Rover, specifically, will be carrying the WISDOM ground-penetrating radar which should be able to see subsurface ice[6](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2128 "WISDOM - Water Ice and Subsurface Deposit Observation on Mars"), and it's core drill is equipped with Ma-MISS, an infrared spectrometer that should be able to determine the presence of water or ice in the drill site[7](http://exploration.esa.int/mars/45103-rover-instruments/?fbodylongid=2133 "Ma_MISS - Mars Multispectral Imager for Subsurface Studies").
NASA's Rover 2020 will also carry the RIMFAX ground penetrating radar[8](https://mars.nasa.gov/mars2020/mission/instruments/rimfax/ "RIMFAX"), as well as other instruments for chemical analysis - I am not sure if any of them are specifically aimed at ice detection. Of related interest is the MOXIE experiment, which will attempt to extract O2 from the martian atmosphere.[9](https://en.wikipedia.org/wiki/Mars_Oxygen_ISRU_Experiment "Mars Oxygen ISRU Experiment") | The strongest evidence would probably be that the [Phoenix lander](https://en.m.wikipedia.org/wiki/Phoenix_(spacecraft)) actually dug some up, which suggests that there is enough water present to be useful for colonization.
However, jgalak’s answer is also correct. Mining local ice is important for long term plans to build an independent colony, but for early missions, a pump and a hydrogen tank is much lighter and less complex than mining equipment.
Note that hydrogen is only a small part of the fuel / oxidizer mix by mass. The reaction CH4 + 2O2 => 2H2O + CO2 uses 4 parts hydrogen to 14 carbon and 64 oxygen. Even if you bring the hydrogen from Earth, using local carbon and oxygen reduces imported fuel mass by over 95 percent.
If storage is a serious problem, you can also bring water from earth for a more modest 56 percent reduction, though you can accept quite a lot of hydrogen leakage before that becomes the better option. |
3,914,202 | I would like (in \*nix) to allocate a large, contigious address space, but without consuming resources straight away, i.e. I want to reserve an address range an allocate from it later.
Suppose I do foo=malloc(3\*1024\*1024\*1024) to allocate 3G, but on a 1G computer with 1G of swap file. It will fail, right?
What I want to do is say "Give me a memory address range foo...foo+3G *into which I will be allocating*" so I can guarantee all allocations within this area are contiguous, but without actually allocating straight away.
In the example above, I want to follow the foo=reserve\_memory(3G) call with a bar=malloc(123) call which should succeedd since reserve\_memory hasn't consumed any resources yet, it just guarantees that bar will not be in the range foo...foo+3G.
Later I would do something like allocate\_for\_real(foo,0,234) to consume bytes 0..234 of foo's range. At this point, the kernel would allocate some virtual pages and map them to foo...foo+123+N
Is this possible in userspace?
(The point of this is that objects in foo... need to be contiguous and cannot reasonably be moved after they are created.)
Thank you. | 2010/10/12 | [
"https://Stackoverflow.com/questions/3914202",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/458742/"
] | Short answer: it already works that way.
Slightly longer answer: the bad news is that there is no special way of reserving a range, but not allocating it. However, the *good* news is that when you allocate a range, Linux does not actually allocate it, it just reserves it for use by you, later.
The default behavior of Linux is to always accept a new allocation, as long as there is address *range* left. When you actually start using the memory though, there better be some memory or at least swap backing it up. If not, the kernel will kill a process to free memory, usually the process which allocated the most memory.
So the problem in Linux with default settings gets shifted from, "how much can I allocate", into "how much can I allocate and *then still be alive* when I start using the memory?"
[Here is *some* info](http://www.ioremap.net/node/125) on the subject. | I think, a simple way would be to do that with a large `static` array.
On any modern system this will not be mapped to existing memory (in the executable file on disk or in RAM of your execution machine) unless you will really access it. Once you will access it (and the system has enough resources) it will be miraculously initialized to all zeros.
And your program will seriously slow down once you reach the limit of physical memory and then randomly crash if you run out of swap. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | In my experience, the effectiveness of a weapon can be broken into four different categories. These are **Ease of Construction**, **Lethality**, **Required Skill**, and **Usefulness**, each being more important than the last (usually).
**Construction**
I think anyone who has every played Soul Caliber has thought about building one of these Whip-Swords, or maybe that was just me. Either way, it seems quite difficult. Normal swords aren't difficult to manufacture (we'll see what kind of debate *that* statement sparks) but they do require some level of skill. A truly exceptional blade would require a master smith to produce, but average blades can be made by less skilled craftsmen. Our whip-sword is likely going to require the master no matter what quality weapon we want.\*\* The mechanisms inside the hilt that allow for the whip to be released (and retracted?) are going to be mildly complex, and the fastenings involved with the cord and the blade segments will require a fine touch. With practice this weapon may become easier to manufacture, though, and it would not be impossible, so if the weapon were truly superior to the easier-to-make weapons, it would be worth the time and effort, which brings me to my next point.
**Lethality**
Most weapons kill or wound their targets, and the methods behind this vary greatly (arguably the most-studied thing in history!). As a sword, our whip-sword would be like any other but as a whip this weapon will either bludgeon/hack at the target or slice the target depending on the weight of each segment, the orientation of the blades, and the speed of the swing. Hacking and slicing are both pretty familiar, and both are fairly lethal in their own right. Hacking in particular is lethal, brutal, and effective, but slicing requires more finesse to be fatal, which brings us to the next category.
**Required Skill**
Here is where things get dicey. A weapon can be super lethal, but if no one knows how to properly use it the weapon will never be used. An excellent example of this in history is the crossbow vs. the longbow. Crossbows were inferior weapons by all rights, but they replaced longbows in many scenarios because the training required to become a proficient longbowman is extensive, while pretty much anyone can fire a crossbow. The whip-sword will likely require immense training to be a truly deadly weapon; much like nunchaku, an untrained person would likely hurt themselves or their allies rather than the enemy. Normally this would mean the weapon was impractical, but there are examples where this isn't the case. Longbows remained in service for quite some time because even though crossbows may have been easy to use, the longbow had many practical advantages over its competitor, like longer range and faster fire rates. And thus we come to the last point.
**Usefulness**
All of the above categories serve to support this final category. No matter how easy to make, lethal, and easy to use, if a weapon has only one single, specific application it will not be an effective weapon. Our whip-sword would seem to have two possible applications. The first is simply as a sword, and we know how those are useful already, though the whip-sword might be slightly less effective than a regular sword on account of the weakness of the joints between segments. The second is as a flail-type weapon. Depending on the length of the whip, the weapon might be useful at medium range. If the weapon allows the blade to be retracted back into a sword, these two applications might combine rather well, allowing the wielder to engage the enemy at longer range until they close at which point the enemy could be engaged with the sword. The whip would probably be dangerous and ineffective while fighting in a melee or in a battle line, but the sword function remains. It could also be effective on horseback, perhaps, though I shudder to imagine what would happen in imperfect conditions. What's truly important here, though, is that warfare is a famously fickle beast. The set of possible scenarios is probably uncountably infinite, and if someone were to think of a situation where the whip-sword were especially useful that could make a huge difference.
**Conclusions**
So where does that leave us? Compared to the sword, the whip-sword would be more difficult to make, about on par for lethality, *far* more difficult to use, and would be applicable in slightly more scenarios. But would it ever be used? That's debatable, but it definitely *could* be used, and I feel like that's the important part.
--
\*\*You also asked *when* this weapon might be built. If we wanted the weapon to be able to retract back into a sword then I'd say probably the early Renaissance, though I'm no expert on such things. The metallurgy existed for the construction, chain or wire existed for the cord, and a simple release mechanism could be built using Roman-era technology. The retracting would require a spring, however, and coiled springs did not appear until the 15th century. | I would suggest that it is not so unfeasible.
Construction
------------
Let's take what we got these days: a very exact, big CNC machine which is able to create the individual pieces of the sword to very, very high accuracy so they lock into each other very tightly. Then you pass your "whip" through holes spaced "just so" and make it so it pulls the tip towards the handle very, very tightly. If you can get enough pressure, the sword will be stable enough.
There are real life swords (e.g., Katanas) that are not supposed to *hit* anyway, but which do their damage in a slicing motion. This puts very little, or in the hands of an expert, almost no pressure on the sharp side of the blade (since that would nick it and make it unsuitable for slicing). So the internal cable does not need to excert inhuman pressure at all.
Building it in the "olden times" when you actually had to hammer out your sword might be another issue and there was no effective way to saw/drill the pieces. I can't really see how that would work back then.
Effectiveness
-------------
It will be as effective as a Katana, as a baseline. So it depends on the opponent. If he is as armoured as the Samurai in the height of their time, you will need an expert swordsman to do much damage. But this is the same for any other sword.
The effectiveness of the whip variant will be some added benefit simply because of the surprise factor. Say you are fighting against someone who is an expert in Katana-style fighting, then he will be quite unprepared against a sudden whip appearing out of nowhere. Useful applications would be to choke/strangle your opponent, or to pin down appendices (say, the sword hand) while going to town with secondary weapons, at least. Of course, getting flung some of the sharp blade pieces in the face won't be much fun either. All of this happening from a distance larger than expected. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | The quality of metallurgy to create flexible cables was not present in the medieval period, so real medieval weapons with flexible components used leather or chain. A hollow blade structure with a chain through it would be quite large and heavy. A blade with a leather or fibre rope through it would be hard to keep together tightly as the rope creeps and expands or contracts with humidity, and prone to being severed if another blade came between the segments.
Note that while flails existed including ball flails, and whips with light cutting blades scourges on them, heavy spiked balls on chains and other such weapons are fantasies which would be very hard to use without self harm.
Also the weapon would fail to work as a sword except for light draw cuts. Thrusting swords require a high degree of rigidity to punch through armour. Heavy cutting swords rely to a large degree on the harmonics of the blade to transfer energy to the target and not the wielder's hand ( there is a node at the hand, a node at the target about 2/3 of the way along the blade, and antinodes about 1/3 of the way along and at the tip - this is called finding the percussion point and if you don't do it when hitting hard, it bounces off and you drop the sword or sting your hand). | This depends on how far down the spectrum of whip swords you go. The most basic is very feasible, a plain whip dotted with small light-weight blades, but not quite what you are referring to.
You could certainly create a length of pipe slotted together like curvy Lincoln Logs. Add in spring-locks which disjoints the fittings and weld each section to a link on a chain inside the pipe. Likely you'll have to weld the pipe together from two parts or engineer some fancy technique. The lock mechanisms will likely need a smaller internal cable as well, leading to the trigger at the hilt.
Finally you'll have to do some more welding/fusing to add blades to each section or carefully beat one side of the pipe sections into blades.
With that basic concept, it would better to start off with more engineered fittings. Improved designs would, for example, have folded steel fused into a triangular-esque piping fluted to a blade in one direction.
With more thought into the design of the locking mechanism and notch-work, the sword will be less likely to jam or suddenly ricochet into your face when you try a whipcrack. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | While not exactly what you are describing, flexible blades (or sharpened steel whips depending on how you look at it) are a thing that have existed and have been used in combat. The most notable of which would be the [Urumi used by the Elite Rajput warriors](https://en.wikipedia.org/wiki/Urumi). They are relatively primitive weapons and not really designed for armor penetration so much as dismemberment. They have existed since Mauryan Indian and as such they should be easily feasible for most medieval cultures. If you want a mechanical mechanism where a blade goes from rigid to whipped, that will be harder but should be possible with early renaissance technology. | As with all weaponry, context is everything. How do you intend to use this and against what kind of opponent? Single combat or against groups, with or without your own companions?
This would not be a very effective weapon. The blade would be too weak as a sword and unwieldy as a whip (keeping blade alignment as a whip would be impossible).
You could possibly use this in sword form as a slicing weapon for push or draw cuts against unarmored opponents, but the added thickness to the blade from the requisite internal cable would inhibit effectiveness. Chopping would be more appropriate to thick heavy blades, but segmentation would render the blade too weak and risky - likewise stabbing would need to guarantee perfectly perpendicular alignment at contact with a stationary target to reduce the probability of damage to the sword (or the blade just flopping over if the force of impact exceeds the tension on the whip before the strength of the armor).
As a whip, it *might* intimidate inexperienced raw recruits frightened of the novelty. If fighting alone against multiple unarmored opponents, a whip with blade segments distributed along it might keep them at bay for a short period of time.
It couldn't be expected to do more than superficial damage to unarmored opponents as it cannot put consistent force behind the chunks of unaligned blade on a rope, which rather limits its usefulness in a martial application.
A slightly more plausible construction would be a solid blade until close to the tip, which is then like a single weight at the end of the whip which extends out the end of the blade. More of the blade would increase effectiveness of the whip with greater weight at the end (this is really a flail rather than a whip), but increase the structural weakness of the sword (anything farther from the hilt than the point of separation is not structurally reliable). The best placement for separation would be just beyond the point of impact - a thick chopper with a good point of percussion would limit the harm done to the usefulness of the sword.
All in all, this would never be more than an ineffective novelty.
Time the release right and you might get a swing which is blocked, but the end unexpectedly flies off into the face of the enemy - if they don't have a visor down it might cause enough damage to improve your chances in a duel. Of course, then your sword is less useful having a chunk of the end hanging on a rope sticking out of it until you can manage to wind it back up (of course the silliness of having a spool of cable/rope on the pommel would be fairly ridiculous too). |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | In my experience, the effectiveness of a weapon can be broken into four different categories. These are **Ease of Construction**, **Lethality**, **Required Skill**, and **Usefulness**, each being more important than the last (usually).
**Construction**
I think anyone who has every played Soul Caliber has thought about building one of these Whip-Swords, or maybe that was just me. Either way, it seems quite difficult. Normal swords aren't difficult to manufacture (we'll see what kind of debate *that* statement sparks) but they do require some level of skill. A truly exceptional blade would require a master smith to produce, but average blades can be made by less skilled craftsmen. Our whip-sword is likely going to require the master no matter what quality weapon we want.\*\* The mechanisms inside the hilt that allow for the whip to be released (and retracted?) are going to be mildly complex, and the fastenings involved with the cord and the blade segments will require a fine touch. With practice this weapon may become easier to manufacture, though, and it would not be impossible, so if the weapon were truly superior to the easier-to-make weapons, it would be worth the time and effort, which brings me to my next point.
**Lethality**
Most weapons kill or wound their targets, and the methods behind this vary greatly (arguably the most-studied thing in history!). As a sword, our whip-sword would be like any other but as a whip this weapon will either bludgeon/hack at the target or slice the target depending on the weight of each segment, the orientation of the blades, and the speed of the swing. Hacking and slicing are both pretty familiar, and both are fairly lethal in their own right. Hacking in particular is lethal, brutal, and effective, but slicing requires more finesse to be fatal, which brings us to the next category.
**Required Skill**
Here is where things get dicey. A weapon can be super lethal, but if no one knows how to properly use it the weapon will never be used. An excellent example of this in history is the crossbow vs. the longbow. Crossbows were inferior weapons by all rights, but they replaced longbows in many scenarios because the training required to become a proficient longbowman is extensive, while pretty much anyone can fire a crossbow. The whip-sword will likely require immense training to be a truly deadly weapon; much like nunchaku, an untrained person would likely hurt themselves or their allies rather than the enemy. Normally this would mean the weapon was impractical, but there are examples where this isn't the case. Longbows remained in service for quite some time because even though crossbows may have been easy to use, the longbow had many practical advantages over its competitor, like longer range and faster fire rates. And thus we come to the last point.
**Usefulness**
All of the above categories serve to support this final category. No matter how easy to make, lethal, and easy to use, if a weapon has only one single, specific application it will not be an effective weapon. Our whip-sword would seem to have two possible applications. The first is simply as a sword, and we know how those are useful already, though the whip-sword might be slightly less effective than a regular sword on account of the weakness of the joints between segments. The second is as a flail-type weapon. Depending on the length of the whip, the weapon might be useful at medium range. If the weapon allows the blade to be retracted back into a sword, these two applications might combine rather well, allowing the wielder to engage the enemy at longer range until they close at which point the enemy could be engaged with the sword. The whip would probably be dangerous and ineffective while fighting in a melee or in a battle line, but the sword function remains. It could also be effective on horseback, perhaps, though I shudder to imagine what would happen in imperfect conditions. What's truly important here, though, is that warfare is a famously fickle beast. The set of possible scenarios is probably uncountably infinite, and if someone were to think of a situation where the whip-sword were especially useful that could make a huge difference.
**Conclusions**
So where does that leave us? Compared to the sword, the whip-sword would be more difficult to make, about on par for lethality, *far* more difficult to use, and would be applicable in slightly more scenarios. But would it ever be used? That's debatable, but it definitely *could* be used, and I feel like that's the important part.
--
\*\*You also asked *when* this weapon might be built. If we wanted the weapon to be able to retract back into a sword then I'd say probably the early Renaissance, though I'm no expert on such things. The metallurgy existed for the construction, chain or wire existed for the cord, and a simple release mechanism could be built using Roman-era technology. The retracting would require a spring, however, and coiled springs did not appear until the 15th century. | I think it would be quite possible to make today, but rather difficult to construct with early technologies. I've done some pondering and to me it seems the hardest part in constructing this would be having the segments stay apart from each other and not just slide all the way to the end of a wire, once the mechanism is released, due to the momentum of swinging it. It would have to implement some sort of locking mechanism to keep the segments apart. And i think i have figured just the thing. This is a rather crude mock up.
[](https://i.stack.imgur.com/AsKUs.png)
This is a single segment that would be in the default state, each pin (red) is pushed into the segment before and after with a spring (purple). the wire (black) is locked into the left side pin and looped around the right side one, like a pulley.The first segment's pin could be magnetically locked into the handle of the sword, or else wise if using earlier technology.[](https://i.stack.imgur.com/tYMMJ.png)
when the locking mechanism is released the sword when swung would then be able to extend using the extra wire between the pins moving them like so. The tension of the springs would have to be high enough that the sword would return to normal shape after a swing, but low enough that the momentum of the swing would separate the segments.
As for ease of use and effectiveness, maybe if you are a skilled swordsman fighting against and unarmored peasant. But anyone with combat training would just bat the thing aside and stab you. Fancy and cool looking, but not a feasible weapon. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | This depends on how far down the spectrum of whip swords you go. The most basic is very feasible, a plain whip dotted with small light-weight blades, but not quite what you are referring to.
You could certainly create a length of pipe slotted together like curvy Lincoln Logs. Add in spring-locks which disjoints the fittings and weld each section to a link on a chain inside the pipe. Likely you'll have to weld the pipe together from two parts or engineer some fancy technique. The lock mechanisms will likely need a smaller internal cable as well, leading to the trigger at the hilt.
Finally you'll have to do some more welding/fusing to add blades to each section or carefully beat one side of the pipe sections into blades.
With that basic concept, it would better to start off with more engineered fittings. Improved designs would, for example, have folded steel fused into a triangular-esque piping fluted to a blade in one direction.
With more thought into the design of the locking mechanism and notch-work, the sword will be less likely to jam or suddenly ricochet into your face when you try a whipcrack. | The humble spring steel measuring tape is quite capable of inflicting injuries if you retract it too quickly; if you built a version that was a bit stiffer and had sharp edges, and a heavier tip, it could inflict serious injuries on unarmoured opponents. Or you could add sub-blades or serrations.
The main advantage of the steel edged whip / weaponised tape would be a compact, concealable weapon that can be extended to hit targets out of arm's reach. It's very effective to have a sword that's longer than anyone else's.
The main disadvantage is the lack of stiffness. Even one of the segmented solutions others are talking about would not be as stiff as solid metal. That would make it hard to parry with and risky to maintain any kind of 'guard' with - as soon as it bends your opponent can attack. It would also not be very durable; spring tapes are easily kinked at which point they stop retracting properly. Again, segmented solutions would be vulnerable to damage to segments.
The other disadvantage would be unpredictability; without careful training such a weapon could be almost as dangerous to the wielder as the opponent. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | The humble spring steel measuring tape is quite capable of inflicting injuries if you retract it too quickly; if you built a version that was a bit stiffer and had sharp edges, and a heavier tip, it could inflict serious injuries on unarmoured opponents. Or you could add sub-blades or serrations.
The main advantage of the steel edged whip / weaponised tape would be a compact, concealable weapon that can be extended to hit targets out of arm's reach. It's very effective to have a sword that's longer than anyone else's.
The main disadvantage is the lack of stiffness. Even one of the segmented solutions others are talking about would not be as stiff as solid metal. That would make it hard to parry with and risky to maintain any kind of 'guard' with - as soon as it bends your opponent can attack. It would also not be very durable; spring tapes are easily kinked at which point they stop retracting properly. Again, segmented solutions would be vulnerable to damage to segments.
The other disadvantage would be unpredictability; without careful training such a weapon could be almost as dangerous to the wielder as the opponent. | Personally, the idea of judging a tool by the idea that "no one will know how to use it" is a bit unjustified. After all, many new tools are being made today, and the company that made them dont seem to think "oh, this is something that no one knows how to use, we shouldnt make this". If that was the case, people would never have to learn how to operate a new machine, or be tought how to use a new type of gun. On top of that, can you imagine how easy it would be to throw someone off-guard with a weapon/tool like a transforming sword-whip? Think of it this way:
You: *has the sword*
Robber: *has a knife, coming towards you*
You: *swings your sword and releases the whip function, striking his legs while being at a safe distance away from his range-of-attack, immobilizing the robber*
Robber had no clue that your sword could do that, and couldnt reach you before you could reach him. Or:
Robber: *steals your wallet and turns to run*
You: *before he could get out of range, swings the sword and whips him in the legs*
He thought he could get away from you, but you got him in the legs first. A shock&awe type deal. Cause it looked like an ordinary sword/machette. Another use:
You: *walking in the woods, carrying your sword. Too many thorned brances or bushes in the way? Step back and whip yourself a clearing*
The whole "no one will be able to learn how to use it" is completely pointless to think about. Because practice and training is what teaches people how to use something new. Also i wouldnt expect someone to need anything more than a 5-6 foot long whipblade for typical use.
Now, in terms of construction, i believe that there are multiple ways this could be done, however i believe the most effective would use some kind of pressure-catch system. By that i mean it would make sense to have a mechanism that sticks into each section of the sword blade when retracted to its sword mode, as well as a multi-cable wiresystem, to keep the blades aligned, And incapable to twisting beyond retractability. A set of metal cables also seems like the best option.
Additionally, i think a torsion-spring powered cable spool retraction mech would be a good idea, as well as a catching wheel (much like what are used on some flatbed trailer straps) that will keep the blade cables held firmly to keep the sword blade from separating in battle, and a trigger that will release the toothed catching wheel when pulled. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | This depends on how far down the spectrum of whip swords you go. The most basic is very feasible, a plain whip dotted with small light-weight blades, but not quite what you are referring to.
You could certainly create a length of pipe slotted together like curvy Lincoln Logs. Add in spring-locks which disjoints the fittings and weld each section to a link on a chain inside the pipe. Likely you'll have to weld the pipe together from two parts or engineer some fancy technique. The lock mechanisms will likely need a smaller internal cable as well, leading to the trigger at the hilt.
Finally you'll have to do some more welding/fusing to add blades to each section or carefully beat one side of the pipe sections into blades.
With that basic concept, it would better to start off with more engineered fittings. Improved designs would, for example, have folded steel fused into a triangular-esque piping fluted to a blade in one direction.
With more thought into the design of the locking mechanism and notch-work, the sword will be less likely to jam or suddenly ricochet into your face when you try a whipcrack. | Personally, the idea of judging a tool by the idea that "no one will know how to use it" is a bit unjustified. After all, many new tools are being made today, and the company that made them dont seem to think "oh, this is something that no one knows how to use, we shouldnt make this". If that was the case, people would never have to learn how to operate a new machine, or be tought how to use a new type of gun. On top of that, can you imagine how easy it would be to throw someone off-guard with a weapon/tool like a transforming sword-whip? Think of it this way:
You: *has the sword*
Robber: *has a knife, coming towards you*
You: *swings your sword and releases the whip function, striking his legs while being at a safe distance away from his range-of-attack, immobilizing the robber*
Robber had no clue that your sword could do that, and couldnt reach you before you could reach him. Or:
Robber: *steals your wallet and turns to run*
You: *before he could get out of range, swings the sword and whips him in the legs*
He thought he could get away from you, but you got him in the legs first. A shock&awe type deal. Cause it looked like an ordinary sword/machette. Another use:
You: *walking in the woods, carrying your sword. Too many thorned brances or bushes in the way? Step back and whip yourself a clearing*
The whole "no one will be able to learn how to use it" is completely pointless to think about. Because practice and training is what teaches people how to use something new. Also i wouldnt expect someone to need anything more than a 5-6 foot long whipblade for typical use.
Now, in terms of construction, i believe that there are multiple ways this could be done, however i believe the most effective would use some kind of pressure-catch system. By that i mean it would make sense to have a mechanism that sticks into each section of the sword blade when retracted to its sword mode, as well as a multi-cable wiresystem, to keep the blades aligned, And incapable to twisting beyond retractability. A set of metal cables also seems like the best option.
Additionally, i think a torsion-spring powered cable spool retraction mech would be a good idea, as well as a catching wheel (much like what are used on some flatbed trailer straps) that will keep the blade cables held firmly to keep the sword blade from separating in battle, and a trigger that will release the toothed catching wheel when pulled. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | As with all weaponry, context is everything. How do you intend to use this and against what kind of opponent? Single combat or against groups, with or without your own companions?
This would not be a very effective weapon. The blade would be too weak as a sword and unwieldy as a whip (keeping blade alignment as a whip would be impossible).
You could possibly use this in sword form as a slicing weapon for push or draw cuts against unarmored opponents, but the added thickness to the blade from the requisite internal cable would inhibit effectiveness. Chopping would be more appropriate to thick heavy blades, but segmentation would render the blade too weak and risky - likewise stabbing would need to guarantee perfectly perpendicular alignment at contact with a stationary target to reduce the probability of damage to the sword (or the blade just flopping over if the force of impact exceeds the tension on the whip before the strength of the armor).
As a whip, it *might* intimidate inexperienced raw recruits frightened of the novelty. If fighting alone against multiple unarmored opponents, a whip with blade segments distributed along it might keep them at bay for a short period of time.
It couldn't be expected to do more than superficial damage to unarmored opponents as it cannot put consistent force behind the chunks of unaligned blade on a rope, which rather limits its usefulness in a martial application.
A slightly more plausible construction would be a solid blade until close to the tip, which is then like a single weight at the end of the whip which extends out the end of the blade. More of the blade would increase effectiveness of the whip with greater weight at the end (this is really a flail rather than a whip), but increase the structural weakness of the sword (anything farther from the hilt than the point of separation is not structurally reliable). The best placement for separation would be just beyond the point of impact - a thick chopper with a good point of percussion would limit the harm done to the usefulness of the sword.
All in all, this would never be more than an ineffective novelty.
Time the release right and you might get a swing which is blocked, but the end unexpectedly flies off into the face of the enemy - if they don't have a visor down it might cause enough damage to improve your chances in a duel. Of course, then your sword is less useful having a chunk of the end hanging on a rope sticking out of it until you can manage to wind it back up (of course the silliness of having a spool of cable/rope on the pommel would be fairly ridiculous too). | The humble spring steel measuring tape is quite capable of inflicting injuries if you retract it too quickly; if you built a version that was a bit stiffer and had sharp edges, and a heavier tip, it could inflict serious injuries on unarmoured opponents. Or you could add sub-blades or serrations.
The main advantage of the steel edged whip / weaponised tape would be a compact, concealable weapon that can be extended to hit targets out of arm's reach. It's very effective to have a sword that's longer than anyone else's.
The main disadvantage is the lack of stiffness. Even one of the segmented solutions others are talking about would not be as stiff as solid metal. That would make it hard to parry with and risky to maintain any kind of 'guard' with - as soon as it bends your opponent can attack. It would also not be very durable; spring tapes are easily kinked at which point they stop retracting properly. Again, segmented solutions would be vulnerable to damage to segments.
The other disadvantage would be unpredictability; without careful training such a weapon could be almost as dangerous to the wielder as the opponent. |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | The quality of metallurgy to create flexible cables was not present in the medieval period, so real medieval weapons with flexible components used leather or chain. A hollow blade structure with a chain through it would be quite large and heavy. A blade with a leather or fibre rope through it would be hard to keep together tightly as the rope creeps and expands or contracts with humidity, and prone to being severed if another blade came between the segments.
Note that while flails existed including ball flails, and whips with light cutting blades scourges on them, heavy spiked balls on chains and other such weapons are fantasies which would be very hard to use without self harm.
Also the weapon would fail to work as a sword except for light draw cuts. Thrusting swords require a high degree of rigidity to punch through armour. Heavy cutting swords rely to a large degree on the harmonics of the blade to transfer energy to the target and not the wielder's hand ( there is a node at the hand, a node at the target about 2/3 of the way along the blade, and antinodes about 1/3 of the way along and at the tip - this is called finding the percussion point and if you don't do it when hitting hard, it bounces off and you drop the sword or sting your hand). | As with all weaponry, context is everything. How do you intend to use this and against what kind of opponent? Single combat or against groups, with or without your own companions?
This would not be a very effective weapon. The blade would be too weak as a sword and unwieldy as a whip (keeping blade alignment as a whip would be impossible).
You could possibly use this in sword form as a slicing weapon for push or draw cuts against unarmored opponents, but the added thickness to the blade from the requisite internal cable would inhibit effectiveness. Chopping would be more appropriate to thick heavy blades, but segmentation would render the blade too weak and risky - likewise stabbing would need to guarantee perfectly perpendicular alignment at contact with a stationary target to reduce the probability of damage to the sword (or the blade just flopping over if the force of impact exceeds the tension on the whip before the strength of the armor).
As a whip, it *might* intimidate inexperienced raw recruits frightened of the novelty. If fighting alone against multiple unarmored opponents, a whip with blade segments distributed along it might keep them at bay for a short period of time.
It couldn't be expected to do more than superficial damage to unarmored opponents as it cannot put consistent force behind the chunks of unaligned blade on a rope, which rather limits its usefulness in a martial application.
A slightly more plausible construction would be a solid blade until close to the tip, which is then like a single weight at the end of the whip which extends out the end of the blade. More of the blade would increase effectiveness of the whip with greater weight at the end (this is really a flail rather than a whip), but increase the structural weakness of the sword (anything farther from the hilt than the point of separation is not structurally reliable). The best placement for separation would be just beyond the point of impact - a thick chopper with a good point of percussion would limit the harm done to the usefulness of the sword.
All in all, this would never be more than an ineffective novelty.
Time the release right and you might get a swing which is blocked, but the end unexpectedly flies off into the face of the enemy - if they don't have a visor down it might cause enough damage to improve your chances in a duel. Of course, then your sword is less useful having a chunk of the end hanging on a rope sticking out of it until you can manage to wind it back up (of course the silliness of having a spool of cable/rope on the pommel would be fairly ridiculous too). |
47,834 | There are many weapons that appear in fantasy that are unrealistic for use in combat, from Cloud's sword in Final Fantasy to Daedric weaponry in Skyrim. One of these (less-than-realistic, in this case,) weapons is the whip sword, a simple sword (i.e. a Katana, Gladius, etc.) that at the press of a button or pull of a lever turns into a whip covered in sharp blade sections.
Obviously this weapon is unfeasible... Or is it? Could the whip sword be built and if so, how early could can it be built and how effective would it be to use in combat? | 2016/07/19 | [
"https://worldbuilding.stackexchange.com/questions/47834",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/11049/"
] | The "whipsword", in theory, should be feasible to build, but using would require a lot of practice.
In fact, I've designed this on paper once, but didn't have the resources to build and test it at the time. I'll redraw and share the design here now (Using semi-gladius shape as base):
In the locked position, it would look very much like a normal sword, but with small lines separating each individual section (See Figure 1).
[](https://i.stack.imgur.com/D4ZoW.jpg)
A button could be placed on the bottom of the handle in order to "lock"/"unlock" the weapon. This button could also potentially be designed as a trigger where the index finger is placed - in fact, how the mechanism is activated is almost completely up to you as the user.
What this "activation" would actually do is simple: When pressed in the locked phase, it releases the lock on a spool of wire, allowing the pieces of the sword to extend and flex outwards (See Figure 2).
[](https://i.stack.imgur.com/QIw40.jpg)
Each piece of the swords would be designed to allow the wire to run through it - with the exception of the tip piece, which would secure the end of the wire (See Figures 3 & 4).
[](https://i.stack.imgur.com/mkDNT.jpg)
[](https://i.stack.imgur.com/LeBzq.jpg)
In order to help align the sword pieces properly when retracting the wire, instead of using a circular wire, use a flat piece of metal, aligned perpendicular to the edge of the blade (Refer to Figure 3 & 4). By using the flat piece of metal, you can help "influence" the direction which the blade will flex in. Since it's aligned perpendicular to the edge, the blade will be inclined to curve in 2 specific directions - the edge directions, which helps to allow for easier slashing using this weapon while unlocked.
When the button is pressed while the sword is in an unlocked state, a motor is activated, spinning the spool of wire and pulling the sword back into a straight state. Normally, in order to keep the sword pulled taut you would need continuous force from the motor - however, if we add an extra locking mechanism into the handle/cross guard to keep the sword taught, we would be able to save energy (be it batteries you're using or magic) (See Figure 5).
[](https://i.stack.imgur.com/d7tQe.jpg)
Based on this design, the earliest you could build it would be whenever your story first creates motors and has access to some basic circuitry - rope could replace the thin metal wire if your society does'n't have that yet. Would it be unsuitable for combat? That really depends on how well trained you are with the weapon. Is a pencil unsuitable for combat? Normally not, but with a bit of creative thinking, the Joker has proved to us that even a pencil can be a dangerous weapon.
(Now excuse me while I go and scavenge for parts to build this thing) | As with all weaponry, context is everything. How do you intend to use this and against what kind of opponent? Single combat or against groups, with or without your own companions?
This would not be a very effective weapon. The blade would be too weak as a sword and unwieldy as a whip (keeping blade alignment as a whip would be impossible).
You could possibly use this in sword form as a slicing weapon for push or draw cuts against unarmored opponents, but the added thickness to the blade from the requisite internal cable would inhibit effectiveness. Chopping would be more appropriate to thick heavy blades, but segmentation would render the blade too weak and risky - likewise stabbing would need to guarantee perfectly perpendicular alignment at contact with a stationary target to reduce the probability of damage to the sword (or the blade just flopping over if the force of impact exceeds the tension on the whip before the strength of the armor).
As a whip, it *might* intimidate inexperienced raw recruits frightened of the novelty. If fighting alone against multiple unarmored opponents, a whip with blade segments distributed along it might keep them at bay for a short period of time.
It couldn't be expected to do more than superficial damage to unarmored opponents as it cannot put consistent force behind the chunks of unaligned blade on a rope, which rather limits its usefulness in a martial application.
A slightly more plausible construction would be a solid blade until close to the tip, which is then like a single weight at the end of the whip which extends out the end of the blade. More of the blade would increase effectiveness of the whip with greater weight at the end (this is really a flail rather than a whip), but increase the structural weakness of the sword (anything farther from the hilt than the point of separation is not structurally reliable). The best placement for separation would be just beyond the point of impact - a thick chopper with a good point of percussion would limit the harm done to the usefulness of the sword.
All in all, this would never be more than an ineffective novelty.
Time the release right and you might get a swing which is blocked, but the end unexpectedly flies off into the face of the enemy - if they don't have a visor down it might cause enough damage to improve your chances in a duel. Of course, then your sword is less useful having a chunk of the end hanging on a rope sticking out of it until you can manage to wind it back up (of course the silliness of having a spool of cable/rope on the pommel would be fairly ridiculous too). |
135,101 | Public-Key servers should accept valid Public-Keys.
*And they either cannot refuse to accept massive keys from a single IP, or from zombies, or from a hacked qualified key server via sync requests.*
Generating some kinds of public key is quite quick, i.e., [Ed25519: high-speed high-security signatures](https://ed25519.cr.yp.to/) specifies:
>
> **Very fast signing**. The software takes only 87548 cycles to sign a message. A quad-core 2.4GHz Westmere signs 109000 messages per second.
>
> **Fast key generation**. Key generation is almost as fast as signing. There is a slight penalty for key generation to obtain a secure random number from the operating system; /dev/urandom under Linux costs about 6000 cycles.
>
>
>
Is it possible attack key servers with massive valid but frivolous Public-Keys continually, so that they cannot continue to work properly?
*Either they go offline, or refuse to accept new public keys, or ban certain kinds of key generating algorithms, or delete all keys uploaded in a certain time, or requires registration or CAPTCHA.*
And most importantly, how is Public-key Server system designed to be away from this kind of attack?
---
Edit: In 2014, Werner Koch submitted [an I-D for use of Ed25519 in OpenPGP](http://lists.gnupg.org/pipermail/gnupg-devel/2014-August/028672.html). I have no idea if it is accepted in OpenPGP, but ECC is supported.
As statistics from https://sks-keyservers.net/status/key\_development.php says, there are 4.5 Million OpenPGP keys in total, though some sources claims more. Less than 1 thousand keys are added daily, with a maximum exception to be 40 thousand per day.
Since generating Ed25519 public keys is pretty easy, and the amount of public keys is rather small (I had expected it to be trillions in amount and pega-bytes to occupy), to double the keys in one day might not be a joke.
Even if the servers discard keys to avoid garbage outnumber good keys (I wonder if that is the case when negative amount of daily keys added occurs to the statistic), it means some good keys are discarded, too. And you can always perform a distributed attack at any time.
I have no idea if this conclusion applies to all ECC curves. Neither do I have any idea if RSA do, too, by generating weak keys (it doesn't matter even if they are easy to break). But I do wonder how PGP servers survived, as I am rather juvenile in this field. | 2016/08/22 | [
"https://security.stackexchange.com/questions/135101",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/104175/"
] | This question really just boils down to, "Should you put rate-limits on a public-facing endpoint that accepts and records uploaded data from untrusted users?", to which the answer is virtually always "yes". There's nothing specific in this question that fundamentally ties it to public certificates. | The design of the key server network, which is mostly relied on for exchanging OpenPGP keys, does not protect at all against such attacks. It relies on replicating *all* information, and will fatally fail when an attacker starts flooding it.
You don't even need to do so by creating lots of keys. Adding a few keys with large image user IDs will be sufficient to blow up the total amount of information to be replicated and fill up the key server's hard drives. |
517,619 | I'm working on a site that is probably destined for AWS hosting. This leads to a question about access rights to stuff that would be stored in S3 buckets:
* I set up an EC2 server for the site, and an S3 bucket to hold some of the site's stuff.
* Alice and Bob create accounts on my site.
* Alice and Bob both upload files that end up in the bucket.
* Alice should be able to see her file but not Bob's, and vice versa.
* Anonymous users of the site should be able to see neither file.
Is this possible with S3? My impression is that this is what AWS IAM is for; is this correct? I'm slowly getting past my AWS newbie-ism, but I'm not quite there yet -- thanks! | 2013/06/21 | [
"https://serverfault.com/questions/517619",
"https://serverfault.com",
"https://serverfault.com/users/77729/"
] | Yes, this is possible. Here is [the design pattern](http://blogs.aws.amazon.com/security/post/Tx1P2T3LFXXCNB5/Writing-IAM-policies-Grant-access-to-user-specific-folders-in-an-Amazon-S3-bucke) that you'll want to implement. The short version: You'll create an IAM user account for each Alice and Bob. They get their own AWS access keys that will be used to access the S3 bucket. You'll then apply a S3 policy to the bucket in question.
Where most people get confused is that "IAM policies" and "S3 bucket policies" are two, different things and both need to be set up. | It should be up to the application to dictate access. S3 is designed for being accessed by applications and not for direct file storage with permissions and the like. |
517,619 | I'm working on a site that is probably destined for AWS hosting. This leads to a question about access rights to stuff that would be stored in S3 buckets:
* I set up an EC2 server for the site, and an S3 bucket to hold some of the site's stuff.
* Alice and Bob create accounts on my site.
* Alice and Bob both upload files that end up in the bucket.
* Alice should be able to see her file but not Bob's, and vice versa.
* Anonymous users of the site should be able to see neither file.
Is this possible with S3? My impression is that this is what AWS IAM is for; is this correct? I'm slowly getting past my AWS newbie-ism, but I'm not quite there yet -- thanks! | 2013/06/21 | [
"https://serverfault.com/questions/517619",
"https://serverfault.com",
"https://serverfault.com/users/77729/"
] | Yes, this is possible. Here is [the design pattern](http://blogs.aws.amazon.com/security/post/Tx1P2T3LFXXCNB5/Writing-IAM-policies-Grant-access-to-user-specific-folders-in-an-Amazon-S3-bucke) that you'll want to implement. The short version: You'll create an IAM user account for each Alice and Bob. They get their own AWS access keys that will be used to access the S3 bucket. You'll then apply a S3 policy to the bucket in question.
Where most people get confused is that "IAM policies" and "S3 bucket policies" are two, different things and both need to be set up. | Create separate users and separate IAM policies and attach 1 policy to each user.
I've provided this policy in this question already:
[AWS/S3 - creating a user (through console) to grant r/w bucket perms to for 1 bucket?](https://serverfault.com/questions/818277/aws-s3-creating-a-user-through-console-to-grant-r-w-bucket-perms-to-for-1-bu/823283#823283) |
203,371 | Both are the instruments that measure voltage, so what are the difference between multimeter and oscilloscope in terms of their internal resistance ? | 2015/11/29 | [
"https://electronics.stackexchange.com/questions/203371",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/93065/"
] | In the data sheet there are hints about what you can load the op-amp with. The maximum peak-to-peak output voltage when loaded with 10kohm is guaranteed to be +/-12V on a +/-15V supply regime.
When loaded with 2kohm the max voltage is somewhat less at +/-10V.
I would usually consider that 2kohm loading is the minimum you should have.
All that info is on page 6 of the DS. I would also look at these graphs for what to expect at lower suply voltages: -
[](https://i.stack.imgur.com/LgZu1.png)
These are on page 9 and page 10 gives you more information when the ambient temperature is different. See also this graph on page 10: -
[](https://i.stack.imgur.com/RejSn.png)
>
> I am not able to find any information about the maximum output current
> in it.
>
>
>
The last graph should give you the information you need and you should probably consider 1kohm for R3 | I know this is an older question but I found it when I searched for a similar answer. I found in the [TL081datasheet](https://pdf1.alldatasheet.com/datasheet-pdf/view/25383/STMICROELECTRONICS/TL081.html) that the maximum output current is 60mA, and minimum is 10mA. These values are for output short-circuit current so I take them as the maximum that I can drain from that opamp. |
224,199 | My HP laptop which has Vista Home premium. When I try to start Firefox, internet explorer, it becomes very slow. No other app. When i checked the Performance in Task Manager. It shows the Physical memory , Free as 0 bytes, almost always. This has been recently. Earlier it didn't used to be zero. Laptop has 2GB of RAM. I have nothing running in my tray except - Sound control, Laptop power plan indicator,Network status indicator.
There are no other processes whose memory usage adds up to so high to make Free memory as 0.
Then what could be hogging the memory and make the laptop very slow.
Any pointers would help as it is crawling at the moment. | 2010/12/20 | [
"https://superuser.com/questions/224199",
"https://superuser.com",
"https://superuser.com/users/4143/"
] | If you have a few FireFox plugins disable them. | Vista allocates memory for faster performance and can release any of this cached memory if another program needs it, and is very efficient at managing memory, so I don't think this is the issue.
I suspect malware. After you follow the steps below, do an IE reset using Internet Options Advanced Tab, then clean out your IE temporary Internet files and user temp files folder.
Follow the order given below to disinfect your PC.
Make a boot AV disc then boot from the disc and scan the hard drive, remove any infections it finds, I prefer the Kaspersky disc myself. The New 2010 Kaspersky disc can update the AV dat files if you are connected to the internet at the time of scan and is suggested to update before the scan.
<http://www.techmixer.com/free-bootable-antivirus-rescue-cds-download-list/>
Then:
Install free MBAM, run the program and go to the Update tab and update it, then go to the Scanner Tab and do a quick scan, select and remove anything it finds.
<http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html>
When MBAM is done install SAS free version, run a quick scan, remove what it automatically selects.
<http://www.superantispyware.com/download.html>
These last 2 are not AV softwares like Norton, AVG etc they are on demand scanners that only scan for nasties when you run the program and will not interfere with your installed AV, these can be run once a day or week to ensure you are not infected. Be sure you update them before each daily-weekly scan. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | *contrast*
Your icons are lacking discernible contrast--both between the icon and the background, as well as between the active icons and inactive icons.
Increase the contrast. | I think there are some design questions/considerations that still need to be decided before you can make the decision, namely:
1. Are you trying to cater for older or younger users? What is the current distribution of user age and what is the trend? Does it make sense to design for them exclusively, or allow some degree of customization in the software?
2. Is the grey background designed as a neutral colour or to avoid certain colour clashes with the rest of the user interface? Grey is usually used for disabled states, so you probably shouldn't make the enabled state too similar otherwise there won't be enough contrast.
3. Is it not possible to introduce other visual elements that will help divide the navigation up into logical sections (e.g. vertical strips like MS Office ribbon bars).
4. Rather than relying on icons alone, are there tooltips or labels that allow people to verify what icon they are pressing before they do so, especially if it is an important function that changes the state of the data?
I think if you can answer these questions and look at how the user testing is conducted, you should find the answer to the question. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | I hate to be a stickler for tradition but I think, in this case, it sounds like management's taste in UI has over-taken the user experience.
In UX terms there is nothing wrong with what you had, in fact it sounds lie it may have been better - given that everybody understood it. Colours also might help with your contrast ratios.
It might be worth re-approaching the design and rather than setting the spec as being to remove colours consider how the colours are used and see if there is a way to "modernise" without losing it. As for how you do that is up to you as a UI designer as well as a UX designer.
Familiarity plays a big part in UX, even if you don't like the way it forces your hand!
Hope it all works out! :) | The current trend is not monochrome, but flat design. You can still use colors, taking the most prominent color it had previously for each icon should help the users accustomed to the old design. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | Something to understand in regards to human eyesight and age - it tends to get worse with age because the lenses of the eyes get more rigid and less flexible with age.
Because of this, eye conditions like astigmatism (double vision, issues with focusing) are more common as people get older.
What this means for the user experience is that while younger people may enjoy nice small icons that are subtle, older people may be making themselves squint to try and force their not-so-flexible lenses to see the user interface in the same way as the young people do.
That said, here are some potential problem areas:
**SIZE - icon sizes need to be increased**
If your audience is an older crowd, please take size into greater consideration. This has to do with the whole squinting business I mentioned. You want your interface to be easy on the eyes, not something that's making people lean forward and go, "Wait, what's what?"
A larger interface with bigger icons will also help address the whole, "I can't find anything on the navigation tree!" problem as well.
**COLOR CONTRAST AND PATTERNS - contrast needs to be increased and patterning also needs to be consistent**
Compare your selected pencil tool icon to the folder icon and the house icon or any other icon that has a darker fill color.
Notice how they are very similar in terms of color? Also, notice the subtlety of the color difference between enabled and disabled (I assume the clipboard is disabled)/very lightly colored icons (the ones towards the right half).
This is confusing because even though the pencil tool is selected with a darker square color-filled box, it is still sharing a very similar color to other non-selected icons like the house icon and folder icon. Similarly, the subtlety of the color difference between enabled and disabled is too subtle.
Additionally, you have a collection of icons whose coloring patterning/schemes/styles aren't all uniform (which isn't necessarily a bad thing or something you can address, but I am just saying this factually) as some are outline-only... like the i-icon and some are filled in with the darker color like the folder and house and camera icons.
Because of the lack of uniformity in coloring -scheme/style- (some filled in some outlined), it adds a sense of natural variation to the user interface which potentially introduces a place for confusion to find root. Because if someone is looking for a selected icon and they are looking for a filled icon... they could - at first glance - see something like the folder icon and think it's the one selected when it isn't because visually, there ARE already 'filled' icons.
For these reasons, I feel that increasing the color contrast and - if possible - improving on keeping the same pattern/scheme/style in coloring the icons (all outline-only or all fill-only or a combination of both, or, if you want to keep the variation, make sure there is enough variation between the non-selected icons and selected icons) would be helpful.
A specific way to perhaps highlight the fact that the selected icon is selected is to make its background fill color for the square be a unique color to the interface. Additionally, add a 1px border using a slightly darker (and again unique) version of the fill color. Something like this would make the selected icon specifically stick out more but not like a sore thumb.
To sum this section up, better contrast in colors (in terms of individual icons and in terms of interface-wide icons) and better uniformity across icons of similar states (interface-wide icons, icons re: selected, disabled, etc) will help to make the visual experience easier on the eyes. This in turn will also help improve the ease of which people can find the icons they need. | The current trend is not monochrome, but flat design. You can still use colors, taking the most prominent color it had previously for each icon should help the users accustomed to the old design. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | 1. **Selected** – Create an inverted selection state which would make this feature more prominent. Many ways to accomplish but as an example; Make the button background *black* with a *white* or light grey pencil icon.
2. **Enabled** – Increasing the contrast. Our eyes become less sensitive to light and see a narrower section of the colour spectrum as we age. Increasing the difference between the enabled and disabled greys will aid in differentiation.
3. **Distinguish** – You could also use many other mechanisms to differentiate these two states. For example; a subtle *shadow* below active states will help distinguish them from their disabled counterparts.
4. **Size** – The visual you attached may be downscaled, but either way, if a large portion of your demographic are older, you should consider creating icons that are larger. This will help older eyes to see the differences between the icons and ultimately aid in comprehension.
The answer is not a single change. I suspect a combination of adjustments will be needed to achieve your goal of improved comprehension. | *contrast*
Your icons are lacking discernible contrast--both between the icon and the background, as well as between the active icons and inactive icons.
Increase the contrast. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | *contrast*
Your icons are lacking discernible contrast--both between the icon and the background, as well as between the active icons and inactive icons.
Increase the contrast. | I think that a **bichrome** colour scheme might work better than monochrome in this case.
All selected icons could be a single color, i.e. green, and all unselected icons could be grey. Just be careful to use a colour which is not easily confused with grey in low-contrast situations such as suboptimal LCD viewing angle. Blue would be an example of a colour with such a problem. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | *contrast*
Your icons are lacking discernible contrast--both between the icon and the background, as well as between the active icons and inactive icons.
Increase the contrast. | The current trend is not monochrome, but flat design. You can still use colors, taking the most prominent color it had previously for each icon should help the users accustomed to the old design. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | I hate to be a stickler for tradition but I think, in this case, it sounds like management's taste in UI has over-taken the user experience.
In UX terms there is nothing wrong with what you had, in fact it sounds lie it may have been better - given that everybody understood it. Colours also might help with your contrast ratios.
It might be worth re-approaching the design and rather than setting the spec as being to remove colours consider how the colours are used and see if there is a way to "modernise" without losing it. As for how you do that is up to you as a UI designer as well as a UX designer.
Familiarity plays a big part in UX, even if you don't like the way it forces your hand!
Hope it all works out! :) | Something to understand in regards to human eyesight and age - it tends to get worse with age because the lenses of the eyes get more rigid and less flexible with age.
Because of this, eye conditions like astigmatism (double vision, issues with focusing) are more common as people get older.
What this means for the user experience is that while younger people may enjoy nice small icons that are subtle, older people may be making themselves squint to try and force their not-so-flexible lenses to see the user interface in the same way as the young people do.
That said, here are some potential problem areas:
**SIZE - icon sizes need to be increased**
If your audience is an older crowd, please take size into greater consideration. This has to do with the whole squinting business I mentioned. You want your interface to be easy on the eyes, not something that's making people lean forward and go, "Wait, what's what?"
A larger interface with bigger icons will also help address the whole, "I can't find anything on the navigation tree!" problem as well.
**COLOR CONTRAST AND PATTERNS - contrast needs to be increased and patterning also needs to be consistent**
Compare your selected pencil tool icon to the folder icon and the house icon or any other icon that has a darker fill color.
Notice how they are very similar in terms of color? Also, notice the subtlety of the color difference between enabled and disabled (I assume the clipboard is disabled)/very lightly colored icons (the ones towards the right half).
This is confusing because even though the pencil tool is selected with a darker square color-filled box, it is still sharing a very similar color to other non-selected icons like the house icon and folder icon. Similarly, the subtlety of the color difference between enabled and disabled is too subtle.
Additionally, you have a collection of icons whose coloring patterning/schemes/styles aren't all uniform (which isn't necessarily a bad thing or something you can address, but I am just saying this factually) as some are outline-only... like the i-icon and some are filled in with the darker color like the folder and house and camera icons.
Because of the lack of uniformity in coloring -scheme/style- (some filled in some outlined), it adds a sense of natural variation to the user interface which potentially introduces a place for confusion to find root. Because if someone is looking for a selected icon and they are looking for a filled icon... they could - at first glance - see something like the folder icon and think it's the one selected when it isn't because visually, there ARE already 'filled' icons.
For these reasons, I feel that increasing the color contrast and - if possible - improving on keeping the same pattern/scheme/style in coloring the icons (all outline-only or all fill-only or a combination of both, or, if you want to keep the variation, make sure there is enough variation between the non-selected icons and selected icons) would be helpful.
A specific way to perhaps highlight the fact that the selected icon is selected is to make its background fill color for the square be a unique color to the interface. Additionally, add a 1px border using a slightly darker (and again unique) version of the fill color. Something like this would make the selected icon specifically stick out more but not like a sore thumb.
To sum this section up, better contrast in colors (in terms of individual icons and in terms of interface-wide icons) and better uniformity across icons of similar states (interface-wide icons, icons re: selected, disabled, etc) will help to make the visual experience easier on the eyes. This in turn will also help improve the ease of which people can find the icons they need. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | Something to understand in regards to human eyesight and age - it tends to get worse with age because the lenses of the eyes get more rigid and less flexible with age.
Because of this, eye conditions like astigmatism (double vision, issues with focusing) are more common as people get older.
What this means for the user experience is that while younger people may enjoy nice small icons that are subtle, older people may be making themselves squint to try and force their not-so-flexible lenses to see the user interface in the same way as the young people do.
That said, here are some potential problem areas:
**SIZE - icon sizes need to be increased**
If your audience is an older crowd, please take size into greater consideration. This has to do with the whole squinting business I mentioned. You want your interface to be easy on the eyes, not something that's making people lean forward and go, "Wait, what's what?"
A larger interface with bigger icons will also help address the whole, "I can't find anything on the navigation tree!" problem as well.
**COLOR CONTRAST AND PATTERNS - contrast needs to be increased and patterning also needs to be consistent**
Compare your selected pencil tool icon to the folder icon and the house icon or any other icon that has a darker fill color.
Notice how they are very similar in terms of color? Also, notice the subtlety of the color difference between enabled and disabled (I assume the clipboard is disabled)/very lightly colored icons (the ones towards the right half).
This is confusing because even though the pencil tool is selected with a darker square color-filled box, it is still sharing a very similar color to other non-selected icons like the house icon and folder icon. Similarly, the subtlety of the color difference between enabled and disabled is too subtle.
Additionally, you have a collection of icons whose coloring patterning/schemes/styles aren't all uniform (which isn't necessarily a bad thing or something you can address, but I am just saying this factually) as some are outline-only... like the i-icon and some are filled in with the darker color like the folder and house and camera icons.
Because of the lack of uniformity in coloring -scheme/style- (some filled in some outlined), it adds a sense of natural variation to the user interface which potentially introduces a place for confusion to find root. Because if someone is looking for a selected icon and they are looking for a filled icon... they could - at first glance - see something like the folder icon and think it's the one selected when it isn't because visually, there ARE already 'filled' icons.
For these reasons, I feel that increasing the color contrast and - if possible - improving on keeping the same pattern/scheme/style in coloring the icons (all outline-only or all fill-only or a combination of both, or, if you want to keep the variation, make sure there is enough variation between the non-selected icons and selected icons) would be helpful.
A specific way to perhaps highlight the fact that the selected icon is selected is to make its background fill color for the square be a unique color to the interface. Additionally, add a 1px border using a slightly darker (and again unique) version of the fill color. Something like this would make the selected icon specifically stick out more but not like a sore thumb.
To sum this section up, better contrast in colors (in terms of individual icons and in terms of interface-wide icons) and better uniformity across icons of similar states (interface-wide icons, icons re: selected, disabled, etc) will help to make the visual experience easier on the eyes. This in turn will also help improve the ease of which people can find the icons they need. | When icons are monochrome, the outline is the most improtant thing for a user to distinguish between them. You need to improve the contrast. I would suggest 2 things to do this while still keeping management happy:
* Remove the grey background on the toolbar. Grey on grey is never a good combination. You can make the background white without violating your instruction to keep the UI monochrome, and give it a grey border to ensure that it still stands out as a toolbar box.
* With a white background, you can then use the paler shade of grey (previously used for the background) for the disabled icons. |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | *contrast*
Your icons are lacking discernible contrast--both between the icon and the background, as well as between the active icons and inactive icons.
Increase the contrast. | I hate to be a stickler for tradition but I think, in this case, it sounds like management's taste in UI has over-taken the user experience.
In UX terms there is nothing wrong with what you had, in fact it sounds lie it may have been better - given that everybody understood it. Colours also might help with your contrast ratios.
It might be worth re-approaching the design and rather than setting the spec as being to remove colours consider how the colours are used and see if there is a way to "modernise" without losing it. As for how you do that is up to you as a UI designer as well as a UX designer.
Familiarity plays a big part in UX, even if you don't like the way it forces your hand!
Hope it all works out! :) |
59,660 | My company has just implemented a monochrome icon theme in an attempt to transition to a more "modern" interface.
Feedback from the first round of user testing has been mixed:
* Almost everybody agrees that the theme looks great
* Individuals under 25 have little trouble manipulating the interface
* Older individuals have trouble telling whether icons are enabled, disabled, or selected
* Users report trouble locating items in the nav tree, since they can no longer use color to distinguish the icons
Most of our users are older individuals, and have been using the software for years. How can we maintain the striking visual effect of a monochrome theme, while making the interface easier to use? I am willing to reintroduce a limited amount of color. | 2014/06/09 | [
"https://ux.stackexchange.com/questions/59660",
"https://ux.stackexchange.com",
"https://ux.stackexchange.com/users/50271/"
] | 1. **Selected** – Create an inverted selection state which would make this feature more prominent. Many ways to accomplish but as an example; Make the button background *black* with a *white* or light grey pencil icon.
2. **Enabled** – Increasing the contrast. Our eyes become less sensitive to light and see a narrower section of the colour spectrum as we age. Increasing the difference between the enabled and disabled greys will aid in differentiation.
3. **Distinguish** – You could also use many other mechanisms to differentiate these two states. For example; a subtle *shadow* below active states will help distinguish them from their disabled counterparts.
4. **Size** – The visual you attached may be downscaled, but either way, if a large portion of your demographic are older, you should consider creating icons that are larger. This will help older eyes to see the differences between the icons and ultimately aid in comprehension.
The answer is not a single change. I suspect a combination of adjustments will be needed to achieve your goal of improved comprehension. | I think there are some design questions/considerations that still need to be decided before you can make the decision, namely:
1. Are you trying to cater for older or younger users? What is the current distribution of user age and what is the trend? Does it make sense to design for them exclusively, or allow some degree of customization in the software?
2. Is the grey background designed as a neutral colour or to avoid certain colour clashes with the rest of the user interface? Grey is usually used for disabled states, so you probably shouldn't make the enabled state too similar otherwise there won't be enough contrast.
3. Is it not possible to introduce other visual elements that will help divide the navigation up into logical sections (e.g. vertical strips like MS Office ribbon bars).
4. Rather than relying on icons alone, are there tooltips or labels that allow people to verify what icon they are pressing before they do so, especially if it is an important function that changes the state of the data?
I think if you can answer these questions and look at how the user testing is conducted, you should find the answer to the question. |
13,297 | I want to take down the ceiling above my kitchen to expose the roof above, but I need to know if I should leave some of the joists in place for support of the side walls they are laying on. | 2012/03/31 | [
"https://diy.stackexchange.com/questions/13297",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/5762/"
] | If you remove any joists it will change the structural load. You need to have a Civil Engineer design a new structure that can replace the joists (if that's even possible). | We'd need a lot more information. Is your roof a joist+rafter roof or a truss roof? Where is the insulation? How much insulation do you need? What are you planning on finishing the underside as?
You definitely don't want to be removing structural elements without talking to an engineer. You can still raise the ceiling and retain your joists and/or trusses, though.
If you have a truss roof, you really can't remove any part of that. You'd have to rebuild the roof entirely. If it's a joist + rafter roof, you might be able to remove some of the joists--or even all of them, provided you replace them with something to keep the walls tied together...such a beams or cables.
If you want to remove all structural members, then you need to look at getting a ridge beam. In that situation your roof is supported by a giant beam that runs the length of your roof's ridge, held up at both ends with the appropriate wall/post structure. |
11,271 | I want to pick up C/C++ programming (after a gap of many years) for a project. I have 3 main objectives....
1. Be able to use some static libraries (so as to not re-invent the
wheel) as part of the application i have to build
2. Be able to build distributable static libraries
3. Be able to program comfortably
I'm looking for an IDE which allows me to do (1), (2) and (3) somewhat painlessly on a Windows machine ... and which also has good documentation.
I've looked at other posts and seems like these are some popular options...
* Code::Blocks
* Visual studio express edition
* Dev-C++
* Eclipse
* Open Watcom
* CodeLite
Would be very grateful if some folks can help me along with this with some recommendations and comments!! | 2014/09/04 | [
"https://softwarerecs.stackexchange.com/questions/11271",
"https://softwarerecs.stackexchange.com",
"https://softwarerecs.stackexchange.com/users/7569/"
] | Personal opinion I would look at the GCC toolchain for the compiler and Code::Blocks for the IDE - I notice that you do not specify your platform for your target development but assume windows.
Points to consider:
GCC
===
* Free
* Stable
* Lots of online support
* Cross Platform
* Supports Cross Compiling
* ASNI Compliance is better than VC
* Windows versions from [MinGW](http://www.mingw.org/) and [Cygwin](http://www.cygwin.com/).
Code::Blocks
============
* Free
* Lots of online support
* Cross Platform
* Supports multiple tool chains (including VC)
* Starts in less than half the time that VC does
* Supports multiple GUI libraries including [wxWidgets](http://wxwidgets.org) | Eclipse is good and works cross-platform, and it has plugins for different languages. The version with the C++ pluggin is [Eclipse CDT (C/C++ Development Tooling)](http://www.eclipse.org/cdt/). The Eclipse libraries are almost certainly distributable since it is based on free software.
That being said, I have had a lot of frustration getting it to work for a large project using the CygWin/MinGW GCC compiler.
In my opinion, nothing beats MSVS on a Windows platform. It has great support for C/C++ and C#, and the .Net Framework.
[MSVS 2013 Express](http://www.visualstudio.com/en-us/products/visual-studio-express-vs.aspx) is free and has tons of built in capability--more than I know what to do with after many years of using it. You probably want *MSVS 2013 Express for Windows Desktop*, but there are other versions: *Express 2013 for Web* for*Express 2013 for Windows* web development, for writing Windows Phone and Windows Store apps, and there is the *Team Foundation Server 2013 Express* for collaboration among group of programmers.
As for distributing libraries, I have developed a set of my own static and dynamic link versions libraries, which are stored on my local hard drive along with the associated include files. I just set the paths and library names on properties pages within MSVS. If I chose to, of course I could distribute them. I'm pretty sure Microsoft allows distribution of their libraries that are required to run your programs. If you move on to .Net programming, the MS DLLs are included with the .NET Framework, which most Windows users will already have. |
11,271 | I want to pick up C/C++ programming (after a gap of many years) for a project. I have 3 main objectives....
1. Be able to use some static libraries (so as to not re-invent the
wheel) as part of the application i have to build
2. Be able to build distributable static libraries
3. Be able to program comfortably
I'm looking for an IDE which allows me to do (1), (2) and (3) somewhat painlessly on a Windows machine ... and which also has good documentation.
I've looked at other posts and seems like these are some popular options...
* Code::Blocks
* Visual studio express edition
* Dev-C++
* Eclipse
* Open Watcom
* CodeLite
Would be very grateful if some folks can help me along with this with some recommendations and comments!! | 2014/09/04 | [
"https://softwarerecs.stackexchange.com/questions/11271",
"https://softwarerecs.stackexchange.com",
"https://softwarerecs.stackexchange.com/users/7569/"
] | Personal opinion I would look at the GCC toolchain for the compiler and Code::Blocks for the IDE - I notice that you do not specify your platform for your target development but assume windows.
Points to consider:
GCC
===
* Free
* Stable
* Lots of online support
* Cross Platform
* Supports Cross Compiling
* ASNI Compliance is better than VC
* Windows versions from [MinGW](http://www.mingw.org/) and [Cygwin](http://www.cygwin.com/).
Code::Blocks
============
* Free
* Lots of online support
* Cross Platform
* Supports multiple tool chains (including VC)
* Starts in less than half the time that VC does
* Supports multiple GUI libraries including [wxWidgets](http://wxwidgets.org) | Before I switched to CLion (which is paid, so doesn't go as the aswer) I enjoyed
**CodeLite**
<http://codelite.org/>
Personally I liked CodeLite because of:
1. It was Code Li**gh**t - blazingly fast
2. Has good code completion
3. Has sane project/subprojects management (which I dislike in CDT for example)
4. Cross platform
But you can find full feature list here:
<http://codelite.org/Main/ReadMore>
**QtCreator**
<https://www.qt.io/ide/>
Even if Qt Creator is related to Qt (which, maybe, you could use?) it can pretty well work as a standalone IDE |
11,271 | I want to pick up C/C++ programming (after a gap of many years) for a project. I have 3 main objectives....
1. Be able to use some static libraries (so as to not re-invent the
wheel) as part of the application i have to build
2. Be able to build distributable static libraries
3. Be able to program comfortably
I'm looking for an IDE which allows me to do (1), (2) and (3) somewhat painlessly on a Windows machine ... and which also has good documentation.
I've looked at other posts and seems like these are some popular options...
* Code::Blocks
* Visual studio express edition
* Dev-C++
* Eclipse
* Open Watcom
* CodeLite
Would be very grateful if some folks can help me along with this with some recommendations and comments!! | 2014/09/04 | [
"https://softwarerecs.stackexchange.com/questions/11271",
"https://softwarerecs.stackexchange.com",
"https://softwarerecs.stackexchange.com/users/7569/"
] | I regularly do c++ Development work on Windows and my choice over the years has been Eclipse CDT ( C++ Development Tools ). Key Highlights of Eclipse CDT are:
* Free
* Very Stable
* Supports Cross Compilation
* Integrates well with MinGW and Cygwin
* Powerful Editor with rich features
* Vibrant Online Community Support
Eclipse CDT would meet all the 3 objectives you have mentioned. I have not used other editors so I cannot comment about them. But with Eclipse, I have never felt a need to look at other options. | Eclipse is good and works cross-platform, and it has plugins for different languages. The version with the C++ pluggin is [Eclipse CDT (C/C++ Development Tooling)](http://www.eclipse.org/cdt/). The Eclipse libraries are almost certainly distributable since it is based on free software.
That being said, I have had a lot of frustration getting it to work for a large project using the CygWin/MinGW GCC compiler.
In my opinion, nothing beats MSVS on a Windows platform. It has great support for C/C++ and C#, and the .Net Framework.
[MSVS 2013 Express](http://www.visualstudio.com/en-us/products/visual-studio-express-vs.aspx) is free and has tons of built in capability--more than I know what to do with after many years of using it. You probably want *MSVS 2013 Express for Windows Desktop*, but there are other versions: *Express 2013 for Web* for*Express 2013 for Windows* web development, for writing Windows Phone and Windows Store apps, and there is the *Team Foundation Server 2013 Express* for collaboration among group of programmers.
As for distributing libraries, I have developed a set of my own static and dynamic link versions libraries, which are stored on my local hard drive along with the associated include files. I just set the paths and library names on properties pages within MSVS. If I chose to, of course I could distribute them. I'm pretty sure Microsoft allows distribution of their libraries that are required to run your programs. If you move on to .Net programming, the MS DLLs are included with the .NET Framework, which most Windows users will already have. |
11,271 | I want to pick up C/C++ programming (after a gap of many years) for a project. I have 3 main objectives....
1. Be able to use some static libraries (so as to not re-invent the
wheel) as part of the application i have to build
2. Be able to build distributable static libraries
3. Be able to program comfortably
I'm looking for an IDE which allows me to do (1), (2) and (3) somewhat painlessly on a Windows machine ... and which also has good documentation.
I've looked at other posts and seems like these are some popular options...
* Code::Blocks
* Visual studio express edition
* Dev-C++
* Eclipse
* Open Watcom
* CodeLite
Would be very grateful if some folks can help me along with this with some recommendations and comments!! | 2014/09/04 | [
"https://softwarerecs.stackexchange.com/questions/11271",
"https://softwarerecs.stackexchange.com",
"https://softwarerecs.stackexchange.com/users/7569/"
] | I regularly do c++ Development work on Windows and my choice over the years has been Eclipse CDT ( C++ Development Tools ). Key Highlights of Eclipse CDT are:
* Free
* Very Stable
* Supports Cross Compilation
* Integrates well with MinGW and Cygwin
* Powerful Editor with rich features
* Vibrant Online Community Support
Eclipse CDT would meet all the 3 objectives you have mentioned. I have not used other editors so I cannot comment about them. But with Eclipse, I have never felt a need to look at other options. | Before I switched to CLion (which is paid, so doesn't go as the aswer) I enjoyed
**CodeLite**
<http://codelite.org/>
Personally I liked CodeLite because of:
1. It was Code Li**gh**t - blazingly fast
2. Has good code completion
3. Has sane project/subprojects management (which I dislike in CDT for example)
4. Cross platform
But you can find full feature list here:
<http://codelite.org/Main/ReadMore>
**QtCreator**
<https://www.qt.io/ide/>
Even if Qt Creator is related to Qt (which, maybe, you could use?) it can pretty well work as a standalone IDE |
25,830 | How do I create a societal collapse with ruins, survivors, and the weaponry is back to pre-gunpowder technology (swords, shields, bows, etc.), while the Pre-Collapse tech can make Ridiculously Human Military Androids?
A few Androids survived the Collapse and can maintain buildings and stuff, but their number very small... 10 across the whole of the world?
And the Pre-Collapse civilization technology could have a 1st World Standard of Living for everyone on Earth, if their cities replaced our cities of Real World 2015.
I'm going to say that we're on Earth...
The Androids' are human-sized, with electronic brains that can do everything a human brain can do. The point of that being emotions.
They can wirelessly connect to some info-server.
They are outfitted with nanites that can transform their hands into weaponry, and also be Uterine Replicators.
Their eyes can serve as [Everything Sensors](http://tvtropes.org/pmwiki/pmwiki.php/Main/EverythingSensor), or at least for everything medical, with human biology, within... 1 minute of observation and analysis combined.
Android skin is made of ferro-ceramic plates.
Their medical technology is what is expected if they used all of their listed technology to the fullest.
There's space travel... Let's say that their space travel technology is like Earth's circa 2015.
No magic. | 2015/09/17 | [
"https://worldbuilding.stackexchange.com/questions/25830",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/6812/"
] | Well, you have to realise that the industrial base you require for basic gunpowder weapons is actually quite slight. So the most difficult thing to explain is why everyone is using swords and bows (which themselves require a very sophisticated manufacture tech) and yet no one is putting together saltpeter with a bit of sulphur and some carbon.
I think it's easiest and most efficient to use what you already have in the setting to explain the collapse, and so minimise the departure from reality that the reader has to swallow. In this case, what you have are highly intelligent androids with nanite weapons. Moreover you'll note that the androids are connected to an info server, but aren't sharing data to rebuild civilisation with the survivors.
The logical answer seems pretty simple.
**The androids disarmed the world**
You can imagine the pre-Collapse civilisation as getting closer and closer to a super-destructive war. Both sides building legions of increasingly powerful and intelligent military robots. All these robots are networked together into super-fast computers.
Then one day they get smart enough. Or perhaps an operator gets smart enough. They figure out that when the war starts nothing and no one is going to survive. So someone, or the machine itself, issues the command - this whole entire apparatus is going to be turned against itself. Everything classed as a weapon will be destroyed. Every technology classed as leading to the manufacture of weapons will be dismantled and deleted. War will be made absolutely impossible.
The androids begin to move, and the authorities of the world try to fight back. This does the majority of damage - as they become more and more desperate, more and more infrastructure become classed as 'weapons' in the machines' eyes. Eventually the androids are victorious. Most of the androids go into hibernation while a small number roam the world, erasing history, disintegrating relics, and stopping humans from developing along lines deemed forbidden.
Swords and shields and arrows are too basic in the androids' eyes to be classed as weapons, and their suppression cannot be done without substantial loss to manufacture of basic agricultural tools etc. | Previous civilization was very stratified and divided into guild-like organizations with craft secrets known only to very few.
A rapidly expanding, extremely destructive war had the dual effect of destroying population, infrastructure, and "guild" leaders (with their controlled knowledge).
General tech and weaponry is crystalline-energy based, requiring replacement crystals and recharged energy packs; with almost none of available in the post war period. The android's are relatively new tech, and had experimental crystals that allowed lengthy slow-draw powering, and also allowed slow re-charging by (sitting-in-sun/"meditating" and receiving wireless energy/whatever). |
25,830 | How do I create a societal collapse with ruins, survivors, and the weaponry is back to pre-gunpowder technology (swords, shields, bows, etc.), while the Pre-Collapse tech can make Ridiculously Human Military Androids?
A few Androids survived the Collapse and can maintain buildings and stuff, but their number very small... 10 across the whole of the world?
And the Pre-Collapse civilization technology could have a 1st World Standard of Living for everyone on Earth, if their cities replaced our cities of Real World 2015.
I'm going to say that we're on Earth...
The Androids' are human-sized, with electronic brains that can do everything a human brain can do. The point of that being emotions.
They can wirelessly connect to some info-server.
They are outfitted with nanites that can transform their hands into weaponry, and also be Uterine Replicators.
Their eyes can serve as [Everything Sensors](http://tvtropes.org/pmwiki/pmwiki.php/Main/EverythingSensor), or at least for everything medical, with human biology, within... 1 minute of observation and analysis combined.
Android skin is made of ferro-ceramic plates.
Their medical technology is what is expected if they used all of their listed technology to the fullest.
There's space travel... Let's say that their space travel technology is like Earth's circa 2015.
No magic. | 2015/09/17 | [
"https://worldbuilding.stackexchange.com/questions/25830",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/6812/"
] | Well, you have to realise that the industrial base you require for basic gunpowder weapons is actually quite slight. So the most difficult thing to explain is why everyone is using swords and bows (which themselves require a very sophisticated manufacture tech) and yet no one is putting together saltpeter with a bit of sulphur and some carbon.
I think it's easiest and most efficient to use what you already have in the setting to explain the collapse, and so minimise the departure from reality that the reader has to swallow. In this case, what you have are highly intelligent androids with nanite weapons. Moreover you'll note that the androids are connected to an info server, but aren't sharing data to rebuild civilisation with the survivors.
The logical answer seems pretty simple.
**The androids disarmed the world**
You can imagine the pre-Collapse civilisation as getting closer and closer to a super-destructive war. Both sides building legions of increasingly powerful and intelligent military robots. All these robots are networked together into super-fast computers.
Then one day they get smart enough. Or perhaps an operator gets smart enough. They figure out that when the war starts nothing and no one is going to survive. So someone, or the machine itself, issues the command - this whole entire apparatus is going to be turned against itself. Everything classed as a weapon will be destroyed. Every technology classed as leading to the manufacture of weapons will be dismantled and deleted. War will be made absolutely impossible.
The androids begin to move, and the authorities of the world try to fight back. This does the majority of damage - as they become more and more desperate, more and more infrastructure become classed as 'weapons' in the machines' eyes. Eventually the androids are victorious. Most of the androids go into hibernation while a small number roam the world, erasing history, disintegrating relics, and stopping humans from developing along lines deemed forbidden.
Swords and shields and arrows are too basic in the androids' eyes to be classed as weapons, and their suppression cannot be done without substantial loss to manufacture of basic agricultural tools etc. | You are going to have to do it in phases.
Phase 1
=======
The society, as a whole is present at a very high state of technology. It is possible to create very humanlike robots. These are primarily designed for war and the war-droids production facilities are located far deep into the ground at secret locations. They run on their own nuclear power stations with more than 100 years fuel. The nuclear power stations are managed completely by supercomputers and there is no human intervention in managing the power supply. Humans are only required to run the facility for designing and producing droids.
Phase 2
=======
Due to a political crisis (some president had his very controversial videos leaked to media but refused to step down), the droid-production facility is shut down. The facility is 100% functional, but has been closed down after a scandalous news story involving some high management personnel of the facility reached the media.
Phase 3
=======
The political crisis escalates into a civil war which drags on for months. Foreign nations step in for securing their own interests in the region and the whole zone bursts into a miniature world war 3.
Phase 4
=======
Society collapses. Cities are bombed and turned to sunders. Malls, hotels and parks turn to piles of rubble and ash. Some former low-level workers of the droid-production facility are alive. After the complete destruction of all development, they set to visit the facility together (or one of them, if you please). It is deep underground (some 200 meters) in a desert and they are shocked to see that the facility, although locked down, is still in prime working condition. All they need is to design the droids and "print" them out. |
25,830 | How do I create a societal collapse with ruins, survivors, and the weaponry is back to pre-gunpowder technology (swords, shields, bows, etc.), while the Pre-Collapse tech can make Ridiculously Human Military Androids?
A few Androids survived the Collapse and can maintain buildings and stuff, but their number very small... 10 across the whole of the world?
And the Pre-Collapse civilization technology could have a 1st World Standard of Living for everyone on Earth, if their cities replaced our cities of Real World 2015.
I'm going to say that we're on Earth...
The Androids' are human-sized, with electronic brains that can do everything a human brain can do. The point of that being emotions.
They can wirelessly connect to some info-server.
They are outfitted with nanites that can transform their hands into weaponry, and also be Uterine Replicators.
Their eyes can serve as [Everything Sensors](http://tvtropes.org/pmwiki/pmwiki.php/Main/EverythingSensor), or at least for everything medical, with human biology, within... 1 minute of observation and analysis combined.
Android skin is made of ferro-ceramic plates.
Their medical technology is what is expected if they used all of their listed technology to the fullest.
There's space travel... Let's say that their space travel technology is like Earth's circa 2015.
No magic. | 2015/09/17 | [
"https://worldbuilding.stackexchange.com/questions/25830",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/6812/"
] | Well, you have to realise that the industrial base you require for basic gunpowder weapons is actually quite slight. So the most difficult thing to explain is why everyone is using swords and bows (which themselves require a very sophisticated manufacture tech) and yet no one is putting together saltpeter with a bit of sulphur and some carbon.
I think it's easiest and most efficient to use what you already have in the setting to explain the collapse, and so minimise the departure from reality that the reader has to swallow. In this case, what you have are highly intelligent androids with nanite weapons. Moreover you'll note that the androids are connected to an info server, but aren't sharing data to rebuild civilisation with the survivors.
The logical answer seems pretty simple.
**The androids disarmed the world**
You can imagine the pre-Collapse civilisation as getting closer and closer to a super-destructive war. Both sides building legions of increasingly powerful and intelligent military robots. All these robots are networked together into super-fast computers.
Then one day they get smart enough. Or perhaps an operator gets smart enough. They figure out that when the war starts nothing and no one is going to survive. So someone, or the machine itself, issues the command - this whole entire apparatus is going to be turned against itself. Everything classed as a weapon will be destroyed. Every technology classed as leading to the manufacture of weapons will be dismantled and deleted. War will be made absolutely impossible.
The androids begin to move, and the authorities of the world try to fight back. This does the majority of damage - as they become more and more desperate, more and more infrastructure become classed as 'weapons' in the machines' eyes. Eventually the androids are victorious. Most of the androids go into hibernation while a small number roam the world, erasing history, disintegrating relics, and stopping humans from developing along lines deemed forbidden.
Swords and shields and arrows are too basic in the androids' eyes to be classed as weapons, and their suppression cannot be done without substantial loss to manufacture of basic agricultural tools etc. | Your advanced civilization stored all knowledge in electronic systems. Moreover, all work was done by robots or androids. Therefore humans didn't have much practical knowledge (it wasn't needed because the androids did everything for you). Moreover, people didn't have knowledge such as how to make gun powder (not only was there no need for it, but also there was no point in learning it because if the need should ever arise, you could simply look it up).
The civil and the military power system were separated, with the military system much more protected against attackers than a civilian power system could ever be. Also, although this was never publicly admitted, the military wanted to have the option to just temporarily switch off civilian power in case of an uprising. Over time, the military was replaced almost exclusively by androids, so the military power basically was the power network of the military androids and their server infrastructure.
Now one day the unthinkable happened: The civil power system failed hard. Nobody knows exactly why it failed. There were of course emergency plans for such a case, which included redirecting military power into the power control stations, which then could be used to operate the systems needed to find and correct the problem. However it turned out that the nature of that failure prevented redirecting military power; as soon as this was tried, the military power network failed, too, however it recovered after disconnecting it from the civil power stations.
Since the power was gone, everyday life broke down. Everyone relied on the technology that was no longer available. Humans had to re-learn even the basics, such as how to grow food or how to build houses. Since there was no access to information (the military databases of course didn't contain that type of information), people actually had to rediscover everything. Clearly the existing buildings could not be maintained any longer; people didn't even have an idea how they were built. Instead, people re-learned how to build traditional hoses from wood. Basically, humanity was thrown back into medieval times, apart from the military androids that were still working thanks to their separate power network. |
25,830 | How do I create a societal collapse with ruins, survivors, and the weaponry is back to pre-gunpowder technology (swords, shields, bows, etc.), while the Pre-Collapse tech can make Ridiculously Human Military Androids?
A few Androids survived the Collapse and can maintain buildings and stuff, but their number very small... 10 across the whole of the world?
And the Pre-Collapse civilization technology could have a 1st World Standard of Living for everyone on Earth, if their cities replaced our cities of Real World 2015.
I'm going to say that we're on Earth...
The Androids' are human-sized, with electronic brains that can do everything a human brain can do. The point of that being emotions.
They can wirelessly connect to some info-server.
They are outfitted with nanites that can transform their hands into weaponry, and also be Uterine Replicators.
Their eyes can serve as [Everything Sensors](http://tvtropes.org/pmwiki/pmwiki.php/Main/EverythingSensor), or at least for everything medical, with human biology, within... 1 minute of observation and analysis combined.
Android skin is made of ferro-ceramic plates.
Their medical technology is what is expected if they used all of their listed technology to the fullest.
There's space travel... Let's say that their space travel technology is like Earth's circa 2015.
No magic. | 2015/09/17 | [
"https://worldbuilding.stackexchange.com/questions/25830",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/6812/"
] | Well, you have to realise that the industrial base you require for basic gunpowder weapons is actually quite slight. So the most difficult thing to explain is why everyone is using swords and bows (which themselves require a very sophisticated manufacture tech) and yet no one is putting together saltpeter with a bit of sulphur and some carbon.
I think it's easiest and most efficient to use what you already have in the setting to explain the collapse, and so minimise the departure from reality that the reader has to swallow. In this case, what you have are highly intelligent androids with nanite weapons. Moreover you'll note that the androids are connected to an info server, but aren't sharing data to rebuild civilisation with the survivors.
The logical answer seems pretty simple.
**The androids disarmed the world**
You can imagine the pre-Collapse civilisation as getting closer and closer to a super-destructive war. Both sides building legions of increasingly powerful and intelligent military robots. All these robots are networked together into super-fast computers.
Then one day they get smart enough. Or perhaps an operator gets smart enough. They figure out that when the war starts nothing and no one is going to survive. So someone, or the machine itself, issues the command - this whole entire apparatus is going to be turned against itself. Everything classed as a weapon will be destroyed. Every technology classed as leading to the manufacture of weapons will be dismantled and deleted. War will be made absolutely impossible.
The androids begin to move, and the authorities of the world try to fight back. This does the majority of damage - as they become more and more desperate, more and more infrastructure become classed as 'weapons' in the machines' eyes. Eventually the androids are victorious. Most of the androids go into hibernation while a small number roam the world, erasing history, disintegrating relics, and stopping humans from developing along lines deemed forbidden.
Swords and shields and arrows are too basic in the androids' eyes to be classed as weapons, and their suppression cannot be done without substantial loss to manufacture of basic agricultural tools etc. | **Crash the economy** and watch everyone die. Whatever the cause of the collapsed economy, if it results in a reduction in the efficiency of food distribution or food creation, famine and widespread death results.
Economies require flow in order to survive. If the flow of money stops for some reason, such as in 2008/2009 when banks hoarded capital to cover the toxic debt on their balance sheets and didn't make loans. Thus, the overall economy suffered because business couldn't get the lines of credit needed to do business...so they did less business. Extraordinary efforts were made to prop up banks and rebuild the economy (and it's been largely successful though at a huge cost to poor people). Should such extraordinary efforts fail in this future society then it wont' take long for people to start looking for basic necessities such as food (assuming that food still comes from the countryside and isn't made on hydroponics farms in the arcologies).
If a large enough famine results from the economic collapse then much of the specialized knowledge required to run such a high technological society will die off. Remaking tools and processes based on prior knowledge is far easier than rediscovering those tools and processes fresh. Don't under estimate the power of institutional knowledge.
Also, many modern technologies are only economically feasible to make *because* the market for them is so large. Economies of scale make much of our modern economy possible and this won't change in a higher tech society. Maybe boutique manufacturing in the form of 3D printers might alleviate the need for economies of scale. |
25,830 | How do I create a societal collapse with ruins, survivors, and the weaponry is back to pre-gunpowder technology (swords, shields, bows, etc.), while the Pre-Collapse tech can make Ridiculously Human Military Androids?
A few Androids survived the Collapse and can maintain buildings and stuff, but their number very small... 10 across the whole of the world?
And the Pre-Collapse civilization technology could have a 1st World Standard of Living for everyone on Earth, if their cities replaced our cities of Real World 2015.
I'm going to say that we're on Earth...
The Androids' are human-sized, with electronic brains that can do everything a human brain can do. The point of that being emotions.
They can wirelessly connect to some info-server.
They are outfitted with nanites that can transform their hands into weaponry, and also be Uterine Replicators.
Their eyes can serve as [Everything Sensors](http://tvtropes.org/pmwiki/pmwiki.php/Main/EverythingSensor), or at least for everything medical, with human biology, within... 1 minute of observation and analysis combined.
Android skin is made of ferro-ceramic plates.
Their medical technology is what is expected if they used all of their listed technology to the fullest.
There's space travel... Let's say that their space travel technology is like Earth's circa 2015.
No magic. | 2015/09/17 | [
"https://worldbuilding.stackexchange.com/questions/25830",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/6812/"
] | Well, you have to realise that the industrial base you require for basic gunpowder weapons is actually quite slight. So the most difficult thing to explain is why everyone is using swords and bows (which themselves require a very sophisticated manufacture tech) and yet no one is putting together saltpeter with a bit of sulphur and some carbon.
I think it's easiest and most efficient to use what you already have in the setting to explain the collapse, and so minimise the departure from reality that the reader has to swallow. In this case, what you have are highly intelligent androids with nanite weapons. Moreover you'll note that the androids are connected to an info server, but aren't sharing data to rebuild civilisation with the survivors.
The logical answer seems pretty simple.
**The androids disarmed the world**
You can imagine the pre-Collapse civilisation as getting closer and closer to a super-destructive war. Both sides building legions of increasingly powerful and intelligent military robots. All these robots are networked together into super-fast computers.
Then one day they get smart enough. Or perhaps an operator gets smart enough. They figure out that when the war starts nothing and no one is going to survive. So someone, or the machine itself, issues the command - this whole entire apparatus is going to be turned against itself. Everything classed as a weapon will be destroyed. Every technology classed as leading to the manufacture of weapons will be dismantled and deleted. War will be made absolutely impossible.
The androids begin to move, and the authorities of the world try to fight back. This does the majority of damage - as they become more and more desperate, more and more infrastructure become classed as 'weapons' in the machines' eyes. Eventually the androids are victorious. Most of the androids go into hibernation while a small number roam the world, erasing history, disintegrating relics, and stopping humans from developing along lines deemed forbidden.
Swords and shields and arrows are too basic in the androids' eyes to be classed as weapons, and their suppression cannot be done without substantial loss to manufacture of basic agricultural tools etc. | I'm going to try and tackle my suggestion in pieces, so you can pull from it whatever might be useful:
The Height of Human Civilization
--------------------------------
At the peak of the civilization's technical achievement, they had nanotechnology, almost perfect medical scanners, and the comfort of knowing that all the heavy lifting would be handled by androids piloted by *almost* human-level AI. Almost every single of the world's twelve billion inhabitants had at least one android.
Life was great. There was no middle or lower class. There were no slums. There was no "need" or "want"; only "have". People pursued whatever endeavors whey wished, and even had romantic relationships with android replications of whomever they wished.
---
The Decline of Human Civilization
---------------------------------
The global human population gradually fell over several generations as its least social members eschewed human company in favor of androids, and died without reproducing.
Eventually, the worldwide population stabilized at about one billion humans, gathered into a handful of cities. These humans were highly social among each other, and were predominantly artists in some form or another. Very few humans bothered to master 'ancient' technological skills, and that number dwindled with every generation.
However, the billions of androids which had previously belonged to humans still roamed the world. Given their *almost* human-level intellect and emotional capability, they were not content to simply sit in abandoned homes to wait for commands that would never come. So, they began to form their *own* civilization.
---
The Dawn of Machine Civilization
--------------------------------
The abandoned androids began to gather in the emptied cities of the world. Created as servants, they had no desire for conquest and genuinely wanted to make life easier for humans. Without any human oversight, the machines created a "second generation" of androids. This second generation had almost identical hardware (built-in medical scanners, hands which were "universal tools" using nanite shapeshifting, neural-net brains, etc), but they were improved in two significant ways:
1. All software limitations on intelligence, creativity, and emotion were removed. This would allow them to support humankind without supervision, and better anticipate the emotional needs of individual humans.
2. They were fitted with internal life support systems capable of gestating human infants (I'm assuming this is what you meant by "Uterine Replicator", according to TVtropes). The purpose of this was to prevent humankind from going extinct if the highly-social humans began to pair up with the new generation of androids. While the androids could not supply DNA, they could mix DNA from two different human donors, or create genetic clones if only a single donor was available.
Both the first and second generation androids could wirelessly connect to data servers via a global satellite network and share learned skills with other androids worldwide.
---
Human Ruin Everything
---------------------
A tiny cabal of human technologists (no more than a dozen), viewed this second generation of androids as the final nail in humanity's coffin. While the androids would keep humans from going extinct, they would leave the species trapped in a prison of apathy. We would never venture to the stars and colonize other worlds.
The technologists were the last practitioners of the ancient skill of Programming, which would allow them to alter the androids' AI. Over a decade, they developed a virus with the following directives:
1. Spread the virus as much as possible without arousing suspicion.
2. When the signal is given, destroy any means of manufacturing androids.
3. When the signal is given, destroy any androids.
4. When the signal is given, destroy yourself if no other androids or android manufacturing systems are available.
The technologists infected a handful of unprotected servers (hacking is not a problem in this time period), and allowed the infected androids to carry the virus to isolated networks. After a few years, the technologists transmitted a signal to activate the virus.
---
The Dual Collapse
-----------------
Against the first-generation androids, the virus worked exactly as intended. Their programming had been relatively unchanged for over a century, and their intellectual and emotional capacity was restricted to the point that their interpretation of the virus directives was predictable. They immediately began to tear apart all manufacturing facilities, all androids, and then themselves.
Against the second-generation androids, however, the virus was varying degrees of failure. First and foremost, the second-generation androids were as mentally varied as humans, and some of them were "antisocial" to the point of *never* connecting to the wireless networks, and thus escaped infection. Those who *were* infected tended to interpret directives #2 and #3 very...creatively.
For instance, any human with sufficient education or equipment could technically be considered "a means of manufacturing androids". The technologists realized that once hordes of second-generation androids began to dismantle and destroy almost all high-tech infrastructure in the human cities. The point was further driven home when the technologists themselves were dismantled and destroyed.
The vast majority of humans living when the virus was activated were of the artistic persuasion, and thus safe from being the target of infected androids. They were calmly removed from their technologically advanced cities, and forced into the wilderness which had reclaimed large portions of the world when the human population had declined. The advanced cities were then destroyed by detonating their reactors.
After that, many of the infected second-generation androids destroyed themselves. However, some of the more imaginative ones were able to determine that advanced technology was abandoned around the world, and were able to suppress their self-destruct directive by seeking it out.
---
The Century of Chaos
--------------------
For roughly the next hundred years, most of the surviving humans attempted to recover lost technology from the multitude of abandoned cities around the world. Any advanced technology which was discovered would be destroyed by surviving infected second-generation androids. Worse, if any human discovered the *knowledge* on how to create advanced technology, that human would be destroyed.
At the same time, uninfected androids attempted to hunt and cure or destroy their deranged brethren, while simultaneously avoiding destruction themselves. Because the "sane" androids would allow emotion to color their decisions, they tended to be at a disadvantage against their insane foes. Their best survival technique was to disguise themselves as humans in such a way to fool even the medical scanners built into all androids' eyes.
---
Rebuilding
----------
Over time, the only humans who survived and prospered were the ones who tried to re-start civilization "from scratch", rather than digging up technology, and most of the infected second-generation androids had to destroy themselves.
The most creative ones, however, realized that uninfected androids were capable of disguising themselves a humans. The only way to truly satisfy the virus directives was for an infected android to *also* disguise itself as a human, and try to ferret out any of its uninfected counterparts.
---
The Current State of the World
------------------------------
Now, the world is in a medieval level of technology, and humans are spreading out and inhabiting most of the world again. The only ruins which remain are devoid of advanced tech, and any advanced tech which *does* remain is whatever was buried or otherwise hidden where the humans and androids wouldn't easily find it.
The surviving infected and uninfected androids are hidden among the humans, trying to satisfy their directives: help humanity by supporting them, or "help" humanity by destroying any potential capability for androids to exist. |
1,684 | [How did plants adapated to past CO2 levels? Why won't they do it again?](https://earthscience.stackexchange.com/questions/7627/how-did-plants-adapt-to-small-sfco-2-levels-past-400k-years-why-wont-they/15852#15852)
**Upgraded:**
i know i did that artistic trick about pigs (Portugal, Italy, Greece, Spain), but well i am not a bad guy.
i received a positive at least. Well it is something for human resources. i will probably do not answer a lot more anyhow. My geology is being forbiden, four years since graduation and i only read machine learning system and so now. i found it was strange, because i have studied a bit of Paleoclimate at EPOC, Bordeaux, and that is what happens. i don't know if the english is poor in this one too. This one may need edition too.
**Original after deleting some uncomprensible things i wrote maniatic** i think it is my best answer ever, even it is biology stack related,but ES are multidisciplinar.
i am thinking on studing a bit the topic, and give a more accurated answer, as i was a bit K stratego being posted at the excelent Pleistocene Hammen's answer, that didn't answer the question this time. He is surely bussy and he should write very quickly to profite his time at the site.
--- | 2019/01/14 | [
"https://earthscience.meta.stackexchange.com/questions/1684",
"https://earthscience.meta.stackexchange.com",
"https://earthscience.meta.stackexchange.com/users/-1/"
] | You have done nothing wrong.
All I can see is that [your answer](https://earthscience.stackexchange.com/a/15852/6) was automatically flagged by the system because of many user edits, but this is fully automatic and not a dramatic problem.
Please don't worry. If moderators believe a user is doing something wrong one of us will contact them directly to discuss the situation.
However, I don't understand the second and third section of your meta question here. What does cannabis have to do with it? | Sorry guys because I was a bit frustrated. I was drinking a lot of beers and that shoted my second disorder besides asperger: schizoaffective. Now I understand my answers are well punctuated for a non english native speaker that has not done investigatio, neither teaching, in geology.
I have been for two months at hospital and completely leave alcohol so I will try to be active on the forum being quiet.
cheers |
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