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ALGOL | External links | External links
Revised Report on the Algorithmic Language Algol 60 by Peter Naur, et al.
The European Side of the Last Phase of the Development of ALGOL 60, by Peter Naur
A History of ALGOL from the Computer History Museum
Category:ALGOL 60 dialect
Category:Articles with example ALGOL 60 code
Category:Computer-related introductions in 1958
Category:Procedural programming languages
Category:Programming languages created in 1958
Category:Structured programming languages
Category:Systems programming languages |
ALGOL | Table of Content | Short description, History, Legacy, Properties, Examples and portability, Code sample comparisons, ALGOL 60, ALGOL 68, Timeline: Hello world, ALGOL 58 (IAL), ALGOL 60 family, ALGOL 68, Timeline of ALGOL special characters, ALGOL implementations, See also, References, Further reading, External links |
AWK | Short description | AWK () is a domain-specific language designed for text processing and typically used as a data extraction and reporting tool. Like sed and grep, it is a filter, and it is a standard feature of most Unix-like operating systems.
The AWK language is a data-driven scripting language consisting of a set of actions to be taken against streams of textual data – either run directly on files or used as part of a pipeline – for purposes of extracting or transforming text, such as producing formatted reports. The language extensively uses the string datatype, associative arrays (that is, arrays indexed by key strings), and regular expressions. While AWK has a limited intended application domain and was especially designed to support one-liner programs, the language is Turing-complete, and even the early Bell Labs users of AWK often wrote well-structured large AWK programs.
AWK was created at Bell Labs in the 1970s, and its name is derived from the surnames of its authors: Alfred Aho (author of egrep), Peter Weinberger (who worked on tiny relational databases), and Brian Kernighan. The acronym is pronounced the same as the name of the bird species auk, which is illustrated on the cover of The AWK Programming Language. When written in all lowercase letters, as awk, it refers to the Unix or Plan 9 program that runs scripts written in the AWK programming language. |
AWK | History | History
According to Brian Kernighan, one of the goals of AWK was to have a tool that would easily manipulate both numbers and strings. AWK was also inspired by Marc Rochkind's programming language that was used to search for patterns in input data, and was implemented using yacc.
As one of the early tools to appear in Version 7 Unix, AWK added computational features to a Unix pipeline besides the Bourne shell, the only scripting language available in a standard Unix environment. It is one of the mandatory utilities of the Single UNIX Specification, and is required by the Linux Standard Base specification.
In 1983, AWK was one of several UNIX tools available for Charles River Data Systems' UNOS operating system under Bell Laboratories license.
AWK was significantly revised and expanded in 1985–88, resulting in the GNU AWK implementation written by Paul Rubin, Jay Fenlason, and Richard Stallman, released in 1988. GNU AWK may be the most widely deployed version because it is included with GNU-based Linux packages. GNU AWK has been maintained solely by Arnold Robbins since 1994. Brian Kernighan's nawk (New AWK) source was first released in 1993 unpublicized, and publicly since the late 1990s; many BSD systems use it to avoid the GPL license.
AWK was preceded by sed (1974). Both were designed for text processing. They share the line-oriented, data-driven paradigm, and are particularly suited to writing one-liner programs, due to the implicit main loop and current line variables. The power and terseness of early AWK programs – notably the powerful regular expression handling and conciseness due to implicit variables, which facilitate one-liners – together with the limitations of AWK at the time, were important inspirations for the Perl language (1987). In the 1990s, Perl became very popular, competing with AWK in the niche of Unix text-processing languages. |
AWK | Structure of AWK programs | Structure of AWK programs
thumb
An AWK program is a series of pattern action pairs, written as:
condition { action }
condition { action }
...
where condition is typically an expression and action is a series of commands. The input is split into records, where by default records are separated by newline characters so that the input is split into lines. The program tests each record against each of the conditions in turn, and executes the action for each expression that is true. Either the condition or the action may be omitted. The condition defaults to matching every record. The default action is to print the record. This is the same pattern-action structure as sed.
In addition to a simple AWK expression, such as foo == 1 or /^foo/, the condition can be BEGIN or END causing the action to be executed before or after all records have been read, or pattern1, pattern2 which matches the range of records starting with a record that matches pattern1 up to and including the record that matches pattern2 before again trying to match against pattern1 on subsequent lines.
In addition to normal arithmetic and logical operators, AWK expressions include the tilde operator, ~, which matches a regular expression against a string. As handy syntactic sugar, /regexp/ without using the tilde operator matches against the current record; this syntax derives from sed, which in turn inherited it from the ed editor, where / is used for searching. This syntax of using slashes as delimiters for regular expressions was subsequently adopted by Perl and ECMAScript, and is now common. The tilde operator was also adopted by Perl. |
AWK | Commands | Commands
AWK commands are the statements that are substituted for action in the examples above. AWK commands can include function calls, variable assignments, calculations, or any combination thereof. AWK contains built-in support for many functions; many more are provided by the various flavors of AWK. Also, some flavors support the inclusion of dynamically linked libraries, which can also provide more functions. |
AWK | The ''print'' command | The print command
The print command is used to output text. The output text is always terminated with a predefined string called the output record separator (ORS) whose default value is a newline. The simplest form of this command is:
print
This displays the contents of the current record. In AWK, records are broken down into fields, and these can be displayed separately:
print $1
Displays the first field of the current record
print $1, $3
Displays the first and third fields of the current record, separated by a predefined string called the output field separator (OFS) whose default value is a single space character
Although these fields ($X) may bear resemblance to variables (the $ symbol indicates variables in the usual Unix shells and in Perl), they actually refer to the fields of the current record. A special case, $0, refers to the entire record. In fact, the commands "print" and "print $0" are identical in functionality.
The print command can also display the results of calculations and/or function calls:
/regex_pattern/ {
# Actions to perform in the event the record (line) matches the above regex_pattern
print 3+2
print foobar(3)
print foobar(variable)
print sin(3-2)
}
Output may be sent to a file:
/regex_pattern/ {
# Actions to perform in the event the record (line) matches the above regex_pattern
print "expression" > "file name"
}
or through a pipe:
/regex_pattern/ {
# Actions to perform in the event the record (line) matches the above regex_pattern
print "expression" | "command"
} |
AWK | Built-in variables | Built-in variables
AWK's built-in variables include the field variables: $1, $2, $3, and so on ($0 represents the entire record). They hold the text or values in the individual text-fields in a record.
Other variables include:
NR: Number of Records. Keeps a current count of the number of input records read so far from all data files. It starts at zero, but is never automatically reset to zero.
FNR: File Number of Records. Keeps a current count of the number of input records read so far in the current file. This variable is automatically reset to zero each time a new file is started.
NF: Number of Fields. Contains the number of fields in the current input record. The last field in the input record can be designated by $NF, the 2nd-to-last field by $(NF-1), the 3rd-to-last field by $(NF-2), etc.
FILENAME: Contains the name of the current input-file.
FS: Field Separator. Contains the "field separator" used to divide fields in the input record. The default, "white space", allows any sequence of space and tab characters. FS can be reassigned with another character or character sequence to change the field separator.
RS: Record Separator. Stores the current "record separator" character. Since, by default, an input line is the input record, the default record separator character is a "newline".
OFS: Output Field Separator. Stores the "output field separator", which separates the fields when awk prints them. The default is a "space" character.
ORS: Output Record Separator. Stores the "output record separator", which separates the output records when awk prints them. The default is a "newline" character.
OFMT: Output Format. Stores the format for numeric output. The default format is "%.6g". |
AWK | Variables and syntax | Variables and syntax
Variable names can use any of the characters [A-Za-z0-9_], with the exception of language keywords, and cannot begin with a numeric digit. The operators + - * / represent addition, subtraction, multiplication, and division, respectively. For string concatenation, simply place two variables (or string constants) next to each other. It is optional to use a space in between if string constants are involved, but two variable names placed adjacent to each other require a space in between. Double quotes delimit string constants. Statements need not end with semicolons. Finally, comments can be added to programs by using # as the first character on a line, or behind a command or sequence of commands. |
AWK | User-defined functions | User-defined functions
In a format similar to C, function definitions consist of the keyword function, the function name, argument names and the function body. Here is an example of a function.
function add_three(number) {
return number + 3
}
This statement can be invoked as follows:
(pattern) {
print add_three(36) # Outputs '''39'''
}
Functions can have variables that are in the local scope. The names of these are added to the end of the argument list, though values for these should be omitted when calling the function. It is convention to add some whitespace in the argument list before the local variables, to indicate where the parameters end and the local variables begin. |
AWK | Examples | Examples |
AWK | Hello, World! | Hello, World!
Here is the customary "Hello, World!" program written in AWK:
BEGIN {
print "Hello, world!"
exit
} |
AWK | Print lines longer than 80 characters | Print lines longer than 80 characters
Print all lines longer than 80 characters. The default action is to print the current line.
length($0) > 80 |
AWK | Count words | Count words
Count words in the input and print the number of lines, words, and characters (like wc):
{
words += NF
chars += length + 1 # add one to account for the newline character at the end of each record (line)
}
END { print NR, words, chars }
As there is no pattern for the first line of the program, every line of input matches by default, so the increment actions are executed for every line. words += NF is shorthand for words = words + NF. |
AWK | Sum last word | Sum last word
{ s += $NF }
END { print s + 0 }
s is incremented by the numeric value of $NF, which is the last word on the line as defined by AWK's field separator (by default, white-space). NF is the number of fields in the current line, e.g. 4. Since $4 is the value of the fourth field, $NF is the value of the last field in the line regardless of how many fields this line has, or whether it has more or fewer fields than surrounding lines. $ is actually a unary operator with the highest operator precedence. (If the line has no fields, then NF is 0, $0 is the whole line, which in this case is empty apart from possible white-space, and so has the numeric value 0.)
At the end of the input the END pattern matches, so s is printed. However, since there may have been no lines of input at all, in which case no value has ever been assigned to s, it will by default be an empty string. Adding zero to a variable is an AWK idiom for coercing it from a string to a numeric value. (Concatenating an empty string is to coerce from a number to a string, e.g. s "". Note, there's no operator to concatenate strings, they're just placed adjacently.) With the coercion the program prints "0" on an empty input, without it, an empty line is printed. |
AWK | Match a range of input lines | Match a range of input lines
NR % 4 == 1, NR % 4 == 3 { printf "%6d %s\n", NR, $0 }
The action statement prints each line numbered. The printf function emulates the standard C printf and works similarly to the print command described above. The pattern to match, however, works as follows: NR is the number of records, typically lines of input, AWK has so far read, i.e. the current line number, starting at 1 for the first line of input. % is the modulo operator. NR % 4 == 1 is true for the 1st, 5th, 9th, etc., lines of input. Likewise, NR % 4 == 3 is true for the 3rd, 7th, 11th, etc., lines of input. The range pattern is false until the first part matches, on line 1, and then remains true up to and including when the second part matches, on line 3. It then stays false until the first part matches again on line 5.
Thus, the program prints lines 1,2,3, skips line 4, and then 5,6,7, and so on. For each line, it prints the line number (on a 6 character-wide field) and then the line contents. For example, when executed on this input:
Rome
Florence
Milan
Naples
Turin
Venice
The previous program prints:
1 Rome
2 Florence
3 Milan
5 Turin
6 Venice |
AWK | Printing the initial or the final part of a file | Printing the initial or the final part of a file
As a special case, when the first part of a range pattern is constantly true, e.g. 1, the range will start at the beginning of the input. Similarly, if the second part is constantly false, e.g. 0, the range will continue until the end of input. For example,
/^--cut here--$/, 0
prints lines of input from the first line matching the regular expression ^--cut here--$, that is, a line containing only the phrase "--cut here--", to the end. |
AWK | Calculate word frequencies | Calculate word frequencies
Word frequency using associative arrays:
BEGIN {
FS="[^a-zA-Z]+"
}
{
for (i=1; i<=NF; i++)
words[tolower($i)]++
}
END {
for (i in words)
print i, words[i]
}
The BEGIN block sets the field separator to any sequence of non-alphabetic characters. Separators can be regular expressions. After that, we get to a bare action, which performs the action on every input line. In this case, for every field on the line, we add one to the number of times that word, first converted to lowercase, appears. Finally, in the END block, we print the words with their frequencies. The line
for (i in words)
creates a loop that goes through the array words, setting i to each subscript of the array. This is different from most languages, where such a loop goes through each value in the array. The loop thus prints out each word followed by its frequency count. tolower was an addition to the One True awk (see below) made after the book was published. |
AWK | Match pattern from command line | Match pattern from command line
This program can be represented in several ways. The first one uses the Bourne shell to make a shell script that does everything. It is the shortest of these methods:
#!/bin/sh
pattern="$1"
shift
awk '/'"$pattern"'/ { print FILENAME ":" $0 }' "$@"
The $pattern in the awk command is not protected by single quotes so that the shell does expand the variable but it needs to be put in double quotes to properly handle patterns containing spaces. A pattern by itself in the usual way checks to see if the whole line ($0) matches. FILENAME contains the current filename. awk has no explicit concatenation operator; two adjacent strings concatenate them. $0 expands to the original unchanged input line.
There are alternate ways of writing this. This shell script accesses the environment directly from within awk:
#!/bin/sh
export pattern="$1"
shift
awk '$0 ~ ENVIRON["pattern"] { print FILENAME ":" $0 }' "$@"
This is a shell script that uses ENVIRON, an array introduced in a newer version of the One True awk after the book was published. The subscript of ENVIRON is the name of an environment variable; its result is the variable's value. This is like the getenv function in various standard libraries and POSIX. The shell script makes an environment variable pattern containing the first argument, then drops that argument and has awk look for the pattern in each file.
~ checks to see if its left operand matches its right operand; !~ is its inverse. A regular expression is just a string and can be stored in variables.
The next way uses command-line variable assignment, in which an argument to awk can be seen as an assignment to a variable:
#!/bin/sh
pattern="$1"
shift
awk '$0 ~ pattern { print FILENAME ":" $0 }' pattern="$pattern" "$@"
Or You can use the -v var=value command line option (e.g. awk -v pattern="$pattern" ...).
Finally, this is written in pure awk, without help from a shell or without the need to know too much about the implementation of the awk script (as the variable assignment on command line one does), but is a bit lengthy:
BEGIN {
pattern = ARGV[1]
for (i = 1; i < ARGC; i++) # remove first argument
ARGV[i] = ARGV[i + 1]
ARGC--
if (ARGC == 1) { # the pattern was the only thing, so force read from standard input (used by book)
ARGC = 2
ARGV[1] = "-"
}
}
$0 ~ pattern { print FILENAME ":" $0 }
The BEGIN is necessary not only to extract the first argument, but also to prevent it from being interpreted as a filename after the BEGIN block ends. ARGC, the number of arguments, is always guaranteed to be ≥1, as ARGV[0] is the name of the command that executed the script, most often the string "awk". ARGV[ARGC] is the empty string, "". # initiates a comment that expands to the end of the line.
Note the if block. awk only checks to see if it should read from standard input before it runs the command. This means that
awk 'prog'
only works because the fact that there are no filenames is only checked before prog is run! If you explicitly set ARGC to 1 so that there are no arguments, awk will simply quit because it feels there are no more input files. Therefore, you need to explicitly say to read from standard input with the special filename -. |
AWK | Self-contained AWK scripts | Self-contained AWK scripts
On Unix-like operating systems self-contained AWK scripts can be constructed using the shebang syntax.
For example, a script that sends the content of a given file to standard output may be built by creating a file named print.awk with the following content:
#!/usr/bin/awk -f
{ print $0 }
It can be invoked with: ./print.awk <filename>
The -f tells awk that the argument that follows is the file to read the AWK program from, which is the same flag that is used in sed. Since they are often used for one-liners, both these programs default to executing a program given as a command-line argument, rather than a separate file. |
AWK | Versions and implementations | Versions and implementations
AWK was originally written in 1977 and distributed with Version 7 Unix.
In 1985 its authors started expanding the language, most significantly by adding user-defined functions. The language is described in the book The AWK Programming Language, published 1988, and its implementation was made available in releases of UNIX System V. To avoid confusion with the incompatible older version, this version was sometimes called "new awk" or nawk. This implementation was released under a free software license in 1996 and is still maintained by Brian Kernighan (see external links below).
Old versions of Unix, such as UNIX/32V, included awkcc, which converted AWK to C. Kernighan wrote a program to turn awk into ; its state is not known.
BWK awk, also known as nawk, refers to the version by Brian Kernighan. It has been dubbed the "One True AWK" because of the use of the term in association with the book that originally described the language and the fact that Kernighan was one of the original authors of AWK. FreeBSD refers to this version as one-true-awk. This version also has features not in the book, such as tolower and ENVIRON that are explained above; see the FIXES file in the source archive for details. This version is used by, for example, Android, FreeBSD, NetBSD, OpenBSD, macOS, and illumos. Brian Kernighan and Arnold Robbins are the main contributors to a source repository for nawk: .
gawk (GNU awk) is another free-software implementation and the only implementation that makes serious progress implementing internationalization and localization and TCP/IP networking. It was written before the original implementation became freely available. It includes its own debugger, and its profiler enables the user to make measured performance enhancements to a script. It also enables the user to extend functionality with shared libraries. Some Linux distributions include gawk as their default AWK implementation. As of version 5.2 (September 2022) gawk includes a persistent memory feature that can remember script-defined variables and functions from one invocation of a script to the next and pass data between unrelated scripts, as described in the Persistent-Memory gawk User Manual: .
gawk-csv. The CSV extension of gawk provides facilities for inputting and outputting CSV formatted data.
mawk is a very fast AWK implementation by Mike Brennan based on a bytecode interpreter.
libmawk is a fork of mawk, allowing applications to embed multiple parallel instances of awk interpreters.
awka (whose front end is written atop the mawk program) is another translator of AWK scripts into C code. When compiled, statically including the author's libawka.a, the resulting executables are considerably sped up and, according to the author's tests, compare very well with other versions of AWK, Perl, or Tcl. Small scripts will turn into programs of 160–170 kB.
tawk (Thompson AWK) is an AWK compiler for Solaris, DOS, OS/2, and Windows, previously sold by Thompson Automation Software (which has ceased its activities).
Jawk is a project to implement AWK in Java, hosted on SourceForge. Extensions to the language are added to provide access to Java features within AWK scripts (i.e., Java threads, sockets, collections, etc.).
xgawk is a fork of gawk that extends gawk with dynamically loadable libraries. The XMLgawk extension was integrated into the official GNU Awk release 4.1.0.
QSEAWK is an embedded AWK interpreter implementation included in the QSE library that provides embedding application programming interface (API) for C and C++.
libfawk is a very small, function-only, reentrant, embeddable interpreter written in C
BusyBox includes an AWK implementation written by Dmitry Zakharov. This is a very small implementation suitable for embedded systems.
CLAWK by Michael Parker provides an AWK implementation in Common Lisp, based upon the regular expression library of the same author.
goawk is an AWK implementation in Go with a few convenience extensions by Ben Hoyt, hosted on Github.
The gawk manual has a list of more AWK implementations. |
AWK | Books | Books
|
AWK | See also | See also
Data transformation
Event-driven programming
List of Unix commands
sed |
AWK | References | References |
AWK | Further reading | Further reading
– Interview with Alfred V. Aho on AWK
AWK – Become an expert in 60 minutes
|
AWK | External links | External links
The Amazing Awk Assembler by Henry Spencer.
awklang.org The site for things related to the awk language
Category:1977 software
Category:Cross-platform software
Category:Domain-specific programming languages
Category:Free and open source interpreters
Category:Pattern matching programming languages
Category:Plan 9 commands
Category:Programming languages created in 1977
Category:Scripting languages
Category:Standard Unix programs
Category:Text-oriented programming languages
Category:Unix SUS2008 utilities
Category:Unix text processing utilities |
AWK | Table of Content | Short description, History, Structure of AWK programs, Commands, The ''print'' command, Built-in variables, Variables and syntax, User-defined functions, Examples, Hello, World!, Print lines longer than 80 characters, Count words, Sum last word, Match a range of input lines, Printing the initial or the final part of a file, Calculate word frequencies, Match pattern from command line, Self-contained AWK scripts, Versions and implementations, Books, See also, References, Further reading, External links |
Asgard | about | In Nordic mythology, Asgard (Old Norse: Ásgarðr; "Garden of the Æsir") is a location associated with the gods. It appears in several Old Norse sagas and mythological texts, including the Eddas, however it has also been suggested to be referred to indirectly in some of these sources. It is described as the fortified home of the Æsir gods and is often associated with gold imagery and contains many other locations known in Nordic mythology such as Valhöll, Iðavöllr and Hlidskjálf.
In some euhemeristic accounts, Asgard is portrayed as being a city in Asia or Troy, however in other accounts that likely more accurately reflect its conception in Old Norse religion, it is depicted as not conforming to a naturalistic geographical position. In these latter accounts, it is found in a range of locations such as over the rainbow bridge Bifröst, in the middle of the world and over the sea. |
Asgard | Etymology | Etymology
The compound word Ásgarðr combines Old Norse ("god") and ("enclosure"). Possible anglicisations include: Ásgarthr, Ásgard, Ásegard, Ásgardr, Asgardr, Ásgarth, Asgarth, Esageard, and Ásgardhr. |
Asgard | Attestations | Attestations |
Asgard | The Poetic Edda | The Poetic Edda
Asgard is named twice in Eddic poetry. The first case is in Hymiskviða, when Thor and Týr journey from Asgard to Hymir's hall to obtain a cauldron large enough to brew beer for a feast for Ægir and the gods. The second instance is in Þrymskviða when Loki is attempting to convince Thor to dress up as Freyja in order to get back Mjölnir by claiming that without his hammer to protect them, jötnar would soon be living in Asgard.
Grímnismál contains among its cosmological descriptions, a number of abodes of the gods, such as Álfheim, Nóatún and Valhalla, which some scholars have identified as being in Asgard. Asgard is not mentioned at any point in the poem. Furthermore, Völuspá references Iðavöllr, one of the most common meeting places of Æsir gods, which in Gylfaginning, Snorri locates in the centre of Asgard. |
Asgard | The Prose Edda | The Prose Edda |
Asgard | Prologue | Prologue
The Prose Edda's euhemeristic prologue portrays the Æsir gods as people who travelled from the East to northern territories. According to Snorri, Asgard represented the town of Troy before Greek warriors overtook it. After the defeat, Trojans moved to northern Europe, where they became a dominant group due to their "advanced technologies and culture". Eventually, other tribes began to perceive the Trojans and their leader Trór (Thor in Old Norse) as gods. |
Asgard | Gylfaginning | Gylfaginning
In Gylfaginning, Snorri Sturluson describes how during the creation of the world, the gods made the earth and surrounded it with the sea. They made the sky from the skull of Ymir and settled the on the shores of the earth. They set down the brows of Ymir, forming Midgard, and in the centre of the world they built Asgard, which he identifies as Troy:
Old Norse text Brodeur translationNext they made for themselves in the middle of the world a city which is called Ásgard; men call it Troy. There dwelt the gods and their kindred; and many tidings and tales of it have come to pass both on earth and aloft. There is one abode called Hlidskjálf, and when Allfather sat in the high-seat there, he looked out over the whole world and saw every man's acts, and knew all things which he saw.
After Asgard is made, the gods then built a hof named Glaðsheimr at Iðavöllr, in the centre of the burg, or walled city, with a high seat for Odin and twelve seats for other gods. It is described as like gold both on the inside and the outside, and as the best of all buildings in the world. They also built Vingólf for the female gods, which is described as both a hall and a hörgr, and a forge with which they crafted objects from gold. After Ragnarök, some gods such as Váli and Baldr will meet at Iðavöllr where Asgard once stood and discuss matters together. There they will also find in the grass the golden chess pieces that the Æsir had once owned.
Later, the section describes how an unnamed jötunn came to the gods with his stallion, Svaðilfari and offered help in building a burg for the gods in three winters, asking in return for the sun, moon, and marriage with Freyja. Despite Freyja's opposition, together the gods agree to fulfill his request if he completes his work in just one winter. As time goes on, the gods grow desperate as it becomes apparent that the jötunn will construct the burg on time. To their surprise, his stallion contributes much of the progress, swiftly moving boulders and rocks. To deal with the problem, Loki comes up with a plan whereupon he changes his appearance to that of a mare, and distracts Svaðilfari to slow down construction. Without the help of his stallion, the builder realises he cannot complete his task in time and goes into a rage, revealing his identity as a jötunn. Thor then kills the builder with Mjöllnir, before any harm to the gods is done. The chapter does not explicitly name Asgard as the fortress but they are commonly identified by scholars.
In Gylfaginning, the central cosmic tree Yggdrasil is described as having three roots that hold it up; one of these goes to the Æsir, which has been interpreted as meaning Asgard. In Grímnismál, this root instead reaches over the realm of men. The bridge Bifröst is told to span from the heavens to the earth and over it the Æsir cross each day to hold council beneath Yggdrasil at the Urðarbrunnr. Based on this, Bifröst is commonly interpreted as the bridge to Asgard. |
Asgard | Skáldskaparmál | Skáldskaparmál
Asgard is mentioned briefly throughout Skáldskaparmál as the name for the home of the Æsir, as in Gylfaginning. In this section, a number of locations are described as lying within Asgard including Valhalla, and in front of its doors, the golden grove Glasir. It also records a name for Thor as 'Defender of Ásgard' (). |
Asgard | Ynglinga Saga | Ynglinga Saga
In the Ynglinga saga, found in Heimskringla, Snorri describes Asgard as a city in Asia, based on a perceived, but erroneous, connection between the words for Asia and Æsir. In the opening stanzas of the Saga of the Ynglings, Asgard is the capital of Asaland, a section of Asia east of the river Tana-kvísl or Vana-Kvísl (kvísl is "arm"), which Snorri explains is the river Tanais (now Don), flowing into the Black Sea. Odin then leaves to settle in the northern part of the world and leaves his brothers Vili and Vé to rule over the city. When the euhemerised Odin dies, the account states that the Swedes believed he had returned to Asgard and would live there forever. |
Asgard | Interpretation and discussion | Interpretation and discussion
Cosmology in Old Norse religion is presented in a vague and often contradictory manner when viewed from a naturalistic standpoint. Snorri places Asgard in the centre of the world, surrounded by Midgard and then the lands inhabited by , all of which are finally encircled by the sea. He also locates the homes of the gods in the heavens. This had led to the proposition of a system of concentric circles, centred on Asgard or Yggdrasil, and sometimes with a vertical axis, leading upwards towards the heavens. There is debate between scholars over whether the gods were conceived of as living in the heavens, with some aligning their views with Snorri, and others proposing that he at times presents the system in a Christian framework and that this organisation is not seen in either Eddic or skaldic poetry. The concept of attempting to create a spatial cosmological model has itself been criticised by scholars who argue that the oral traditions did not form a naturalistic, structured system that aimed to be internally geographically consistent. An alternative proposal is that the world should be conceived of as a number of realms connected by passages that cannot be typically traversed. This would explain how Asgard can be located both to the east and west of the realm of men, over the sea and over Bifröst.
It has been noted that the tendency to link Asgard to Troy is part of a wider European cultural practice of claiming Trojan origins for one's culture, first seen in the Aeneid and also featuring in Geoffrey of Monmouth's Historia regum Britanniae for the founding of Britain. |
Asgard | Depictions in popular culture | Depictions in popular culture
Both Asgard and Valhalla have been portrayed many times in popular culture |
Asgard | In film | In film
Asgard is depicted in the 1989 film comedy film Erik the Viking as a frozen wasteland dominated by the Halls of Valhalla on a high plateau. In the film the Æsir are depicted as spoilt children |
Asgard | In comics | In comics
Thor first appeared in the Marvel Universe within comic series Journey into Mystery in the issues #83 during August 1962. Following this release, he becomes one of the central figures in the comics along with Loki and Odin. In the Marvel Cinematic Universe, Thor and Loki make their first appearance together in the 2011 film Thor. After that, Thor becomes a regular character in the Marvel Cinematic Universe and reappears in several films, including the Avengers series. Asgard becomes the central element of the film Thor: Ragnarok, where it is destroyed following the Old Norse mythos. These and other Norse mythology elements also appear in video games, TV series, and books based in and on the Marvel Universe, although these depictions do not closely follow historical sources. |
Asgard | In video games | In video games
Asgard is an explorable realm in the video game God of War: Ragnarök, a sequel to 2018's Norse-themed God of War.
In the Assassin's Creed Valhalla video game, Asgard is featured as part of a "vision quest". |
Asgard | See also | See also
Mount Olympus – home of the Olympian gods |
Asgard | Citations | Citations |
Asgard | Bibliography | Bibliography |
Asgard | Primary | Primary
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Asgard | Secondary | Secondary
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Asgard | External links | External links
MyNDIR (My Norse Digital Image Repository) Illustrations of Asgard from manuscripts and early print books.
Category:Locations in Norse mythology |
Asgard | Table of Content | about, Etymology, Attestations, The Poetic Edda, The Prose Edda, Prologue, Gylfaginning, Skáldskaparmál, Ynglinga Saga, Interpretation and discussion, Depictions in popular culture, In film, In comics, In video games, See also, Citations, Bibliography, Primary, Secondary, External links |
Apollo program | Short description | The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which successfully landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in space. It was conceived in 1960 as a three-person spacecraft during President Dwight D. Eisenhower's administration. Apollo was later dedicated to President John F. Kennedy's national goal for the 1960s of "landing a man on the Moon and returning him safely to the Earth" in an address to Congress on May 25, 1961. It was the third US human spaceflight program to fly, preceded by Project Gemini conceived in 1961 to extend spaceflight capability in support of Apollo.
Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module (LM) on July 20, 1969, and walked on the lunar surface, while Michael Collins remained in lunar orbit in the command and service module (CSM), and all three landed safely on Earth in the Pacific Ocean on July 24. Five subsequent Apollo missions also landed astronauts on the Moon, the last, Apollo 17, in December 1972. In these six spaceflights, twelve people walked on the Moon.
thumb|Buzz Aldrin (pictured) walked on the Moon with Neil Armstrong, on Apollo 11, July 20–21, 1969.|alt=Astronaut Buzz Aldrin, standing on the Moon
thumb|NASA Apollo 17 Lunar Roving Vehicle
alt=|thumb|Earthrise, the iconic 1968 image from Apollo 8 taken by astronaut William Anders
Apollo ran from 1961 to 1972, with the first crewed flight in 1968. It encountered a major setback in 1967 when an Apollo 1 cabin fire killed the entire crew during a prelaunch test. After the first successful landing, sufficient flight hardware remained for nine follow-on landings with a plan for extended lunar geological and astrophysical exploration. Budget cuts forced the cancellation of three of these. Five of the remaining six missions achieved successful landings, but the Apollo 13 landing had to be aborted after an oxygen tank exploded en route to the Moon, crippling the CSM. The crew barely managed a safe return to Earth by using the lunar module as a "lifeboat" on the return journey. Apollo used the Saturn family of rockets as launch vehicles, which were also used for an Apollo Applications Program, which consisted of Skylab, a space station that supported three crewed missions in 1973–1974, and the Apollo–Soyuz Test Project, a joint United States-Soviet Union low Earth orbit mission in 1975.
Apollo set several major human spaceflight milestones. It stands alone in sending crewed missions beyond low Earth orbit. Apollo 8 was the first crewed spacecraft to orbit another celestial body, and Apollo 11 was the first crewed spacecraft to land humans on one.
Overall, the Apollo program returned of lunar rocks and soil to Earth, greatly contributing to the understanding of the Moon's composition and geological history. The program laid the foundation for NASA's subsequent human spaceflight capability and funded construction of its Johnson Space Center and Kennedy Space Center. Apollo also spurred advances in many areas of technology incidental to rocketry and human spaceflight, including avionics, telecommunications, and computers. |
Apollo program | Name | Name
The program was named after Apollo, the Greek god of light, music, and the Sun, by NASA manager Abe Silverstein, who later said, "I was naming the spacecraft like I'd name my baby."Murray & Cox 1989, p. 55 Silverstein chose the name at home one evening, early in 1960, because he felt "Apollo riding his chariot across the Sun was appropriate to the grand scale of the proposed program".
The context of this was that the program focused at its beginning mainly on developing an advanced crewed spacecraft, the Apollo command and service module, succeeding the Mercury program. A lunar landing became the focus of the program only in 1961. Thereafter Project Gemini instead followed the Mercury program to test and study advanced crewed spaceflight technology. |
Apollo program | Background | Background |
Apollo program | Origin and spacecraft feasibility studies | Origin and spacecraft feasibility studies
The Apollo program was conceived during the Eisenhower administration in early 1960, as a follow-up to Project Mercury. While the Mercury capsule could support only one astronaut on a limited Earth orbital mission, Apollo would carry three. Possible missions included ferrying crews to a space station, circumlunar flights, and eventual crewed lunar landings.
In July 1960, NASA Deputy Administrator Hugh L. Dryden announced the Apollo program to industry representatives at a series of Space Task Group conferences. Preliminary specifications were laid out for a spacecraft with a mission module cabin separate from the command module (piloting and reentry cabin), and a propulsion and equipment module. On August 30, a feasibility study competition was announced, and on October 25, three study contracts were awarded to General Dynamics/Convair, General Electric, and the Glenn L. Martin Company. Meanwhile, NASA performed its own in-house spacecraft design studies led by Maxime Faget, to serve as a gauge to judge and monitor the three industry designs. |
Apollo program | Political pressure builds | Political pressure builds
In November 1960, John F. Kennedy was elected president after a campaign that promised American superiority over the Soviet Union in the fields of space exploration and missile defense. Up to the election of 1960, Kennedy had been speaking out against the "missile gap" that he and many other senators said had developed between the Soviet Union and the United States due to the inaction of President Eisenhower. Beyond military power, Kennedy used aerospace technology as a symbol of national prestige, pledging to make the US not "first but, first and, first if, but first period".Beschloss 1997 Despite Kennedy's rhetoric, he did not immediately come to a decision on the status of the Apollo program once he became president. He knew little about the technical details of the space program, and was put off by the massive financial commitment required by a crewed Moon landing.Sidey 1963, pp. 117–118 When Kennedy's newly appointed NASA Administrator James E. Webb requested a 30 percent budget increase for his agency, Kennedy supported an acceleration of NASA's large booster program but deferred a decision on the broader issue.Beschloss 1997, p. 55
On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person to fly in space, reinforcing American fears about being left behind in a technological competition with the Soviet Union. At a meeting of the US House Committee on Science and Astronautics one day after Gagarin's flight, many congressmen pledged their support for a crash program aimed at ensuring that America would catch up.87th Congress 1961 Kennedy was circumspect in his response to the news, refusing to make a commitment on America's response to the Soviets.Sidey 1963, p. 114
thumb|right|President Kennedy delivers his proposal to put a man on the Moon before a joint session of Congress, May 25, 1961.|alt=President John F. Kennedy addresses a joint session of Congress, with Vice President Lyndon B. Johnson and House Speaker Sam Rayburn seated behind him
On April 20, Kennedy sent a memo to Vice President Lyndon B. Johnson, asking Johnson to look into the status of America's space program, and into programs that could offer NASA the opportunity to catch up. Key Apollo Source Documents . Johnson responded approximately one week later, concluding that "we are neither making maximum effort nor achieving results necessary if this country is to reach a position of leadership." Key Apollo Source Documents . His memo concluded that a crewed Moon landing was far enough in the future that it was likely the United States would achieve it first.
On May 25, 1961, twenty days after the first US crewed spaceflight Freedom 7, Kennedy proposed the crewed Moon landing in a Special Message to the Congress on Urgent National Needs: |
Apollo program | NASA expansion | NASA expansion
At the time of Kennedy's proposal, only one American had flown in space—less than a month earlier—and NASA had not yet sent an astronaut into orbit. Even some NASA employees doubted whether Kennedy's ambitious goal could be met.Murray & Cox 1989, pp. 16–17 By 1963, Kennedy even came close to agreeing to a joint US-USSR Moon mission, to eliminate duplication of effort.
With the clear goal of a crewed landing replacing the more nebulous goals of space stations and circumlunar flights, NASA decided that, in order to make progress quickly, it would discard the feasibility study designs of Convair, GE, and Martin, and proceed with Faget's command and service module design. The mission module was determined to be useful only as an extra room, and therefore unnecessary. They used Faget's design as the specification for another competition for spacecraft procurement bids in October 1961. On November 28, 1961, it was announced that North American Aviation had won the contract, although its bid was not rated as good as the Martin proposal. Webb, Dryden and Robert Seamans chose it in preference due to North American's longer association with NASA and its predecessor.
Landing humans on the Moon by the end of 1969 required the most sudden burst of technological creativity, and the largest commitment of resources ($25 billion; $ in US dollars) ever made by any nation in peacetime. At its peak, the Apollo program employed 400,000 people and required the support of over 20,000 industrial firms and universities.
On July 1, 1960, NASA established the Marshall Space Flight Center (MSFC) in Huntsville, Alabama. MSFC designed the heavy lift-class Saturn launch vehicles, which would be required for Apollo. |
Apollo program | Manned Spacecraft Center | Manned Spacecraft Center
It became clear that managing the Apollo program would exceed the capabilities of Robert R. Gilruth's Space Task Group, which had been directing the nation's crewed space program from NASA's Langley Research Center. So Gilruth was given authority to grow his organization into a new NASA center, the Manned Spacecraft Center (MSC). A site was chosen in Houston, Texas, on land donated by Rice University, and Administrator Webb announced the conversion on September 19, 1961. It was also clear NASA would soon outgrow its practice of controlling missions from its Cape Canaveral Air Force Station launch facilities in Florida, so a new Mission Control Center would be included in the MSC.
thumb|right|thumbtime=17:32|President Kennedy speaks at Rice University, September 12, 1962 (17 min, 47 s).
In September 1962, by which time two Project Mercury astronauts had orbited the Earth, Gilruth had moved his organization to rented space in Houston, and construction of the MSC facility was under way, Kennedy visited Rice to reiterate his challenge in a famous speech:
The MSC was completed in September 1963. It was renamed by the United States Congress in honor of Lyndon B. Johnson soon after his death in 1973. |
Apollo program | Launch Operations Center | Launch Operations Center
It also became clear that Apollo would outgrow the Canaveral launch facilities in Florida. The two newest launch complexes were already being built for the Saturn I and IB rockets at the northernmost end: LC-34 and LC-37. But an even bigger facility would be needed for the mammoth rocket required for the crewed lunar mission, so land acquisition was started in July 1961 for a Launch Operations Center (LOC) immediately north of Canaveral at Merritt Island. The design, development and construction of the center was conducted by Kurt H. Debus, a member of Wernher von Braun's original V-2 rocket engineering team. Debus was named the LOC's first Director. Construction began in November 1962. Following Kennedy's death, President Johnson issued an executive order on November 29, 1963, to rename the LOC and Cape Canaveral in honor of Kennedy.
thumb|George Mueller, Wernher von Braun, and Eberhard Rees watch the AS-101 launch from the firing room.
The LOC included Launch Complex 39, a Launch Control Center, and a Vertical Assembly Building (VAB).The building was renamed "Vehicle Assembly Building" on February 3, 1965. in which the space vehicle (launch vehicle and spacecraft) would be assembled on a mobile launcher platform and then moved by a crawler-transporter to one of several launch pads. Although at least three pads were planned, only two, designated AandB, were completed in October 1965. The LOC also included an Operations and Checkout Building (OCB) to which Gemini and Apollo spacecraft were initially received prior to being mated to their launch vehicles. The Apollo spacecraft could be tested in two vacuum chambers capable of simulating atmospheric pressure at altitudes up to , which is nearly a vacuum. |
Apollo program | Organization | Organization
Administrator Webb realized that in order to keep Apollo costs under control, he had to develop greater project management skills in his organization, so he recruited George E. Mueller for a high management job. Mueller accepted, on the condition that he have a say in NASA reorganization necessary to effectively administer Apollo. Webb then worked with Associate Administrator (later Deputy Administrator) Seamans to reorganize the Office of Manned Space Flight (OMSF).Johnson 2002 On July 23, 1963, Webb announced Mueller's appointment as Deputy Associate Administrator for Manned Space Flight, to replace then Associate Administrator D. Brainerd Holmes on his retirement effective September 1. Under Webb's reorganization, the directors of the Manned Spacecraft Center (Gilruth), Marshall Space Flight Center (von Braun), and the Launch Operations Center (Debus) reported to Mueller.
Based on his industry experience on Air Force missile projects, Mueller realized some skilled managers could be found among high-ranking officers in the U.S. Air Force, so he got Webb's permission to recruit General Samuel C. Phillips, who gained a reputation for his effective management of the Minuteman program, as OMSF program controller. Phillips's superior officer Bernard A. Schriever agreed to loan Phillips to NASA, along with a staff of officers under him, on the condition that Phillips be made Apollo Program Director. Mueller agreed, and Phillips managed Apollo from January 1964, until it achieved the first human landing in July 1969, after which he returned to Air Force duty.
Charles Fishman, in One Giant Leap, estimated the number of people and organizations involved into the Apollo program as "410,000 men and women at some 20,000 different companies contributed to the effort". |
Apollo program | Choosing a mission mode | Choosing a mission mode
right|thumb|John Houbolt explaining the LOR concept
thumb|right|Early Apollo configuration for Direct Ascent and Earth Orbit Rendezvous, 1961
Once Kennedy had defined a goal, the Apollo mission planners were faced with the challenge of designing a spacecraft that could meet it while minimizing risk to human life, limiting cost, and not exceeding limits in possible technology and astronaut skill. Four possible mission modes were considered:
Direct Ascent: The spacecraft would be launched as a unit and travel directly to the lunar surface, without first going into lunar orbit. A Earth return ship would land all three astronauts atop a descent propulsion stage,Using the Apollo 11 lunar lander's mass ratio of descent stage to ascent stage, scaled up to Nova's payload. which would be left on the Moon. This design would have required development of the extremely powerful Saturn C-8 or Nova launch vehicle to carry a payload to the Moon.
Earth Orbit Rendezvous (EOR): Multiple rocket launches (up to 15 in some plans) would carry parts of the Direct Ascent spacecraft and propulsion units for translunar injection (TLI). These would be assembled into a single spacecraft in Earth orbit.
Lunar Surface Rendezvous: Two spacecraft would be launched in succession. The first, an automated vehicle carrying propellant for the return to Earth, would land on the Moon, to be followed some time later by the crewed vehicle. Propellant would have to be transferred from the automated vehicle to the crewed vehicle.
Lunar Orbit Rendezvous (LOR): This turned out to be the winning configuration, which achieved the goal with Apollo 11 on July 20, 1969: a single Saturn V launched a spacecraft that was composed of a Apollo command and service module which remained in orbit around the Moon and a two-stage Apollo Lunar Module spacecraft which was flown by two astronauts to the surface, flown back to dock with the command module and was then discarded. Landing the smaller spacecraft on the Moon, and returning an even smaller part () to lunar orbit, minimized the total mass to be launched from Earth, but this was the last method initially considered because of the perceived risk of rendezvous and docking.
In early 1961, direct ascent was generally the mission mode in favor at NASA. Many engineers feared that rendezvous and docking, maneuvers that had not been attempted in Earth orbit, would be nearly impossible in lunar orbit. LOR advocates including John Houbolt at Langley Research Center emphasized the important weight reductions that were offered by the LOR approach. Throughout 1960 and 1961, Houbolt campaigned for the recognition of LOR as a viable and practical option. Bypassing the NASA hierarchy, he sent a series of memos and reports on the issue to Associate Administrator Robert Seamans; while acknowledging that he spoke "somewhat as a voice in the wilderness", Houbolt pleaded that LOR should not be discounted in studies of the question.
Seamans's establishment of an ad hoc committee headed by his special technical assistant Nicholas E. Golovin in July 1961, to recommend a launch vehicle to be used in the Apollo program, represented a turning point in NASA's mission mode decision.Hansen 1999, p. 32 This committee recognized that the chosen mode was an important part of the launch vehicle choice, and recommended in favor of a hybrid EOR-LOR mode. Its consideration of LOR—as well as Houbolt's ceaseless work—played an important role in publicizing the workability of the approach. In late 1961 and early 1962, members of the Manned Spacecraft Center began to come around to support LOR, including the newly hired deputy director of the Office of Manned Space Flight, Joseph Shea, who became a champion of LOR.Hansen 1999, pp. 35–39 The engineers at Marshall Space Flight Center (MSFC), who were heavily invested in direct ascent, took longer to become convinced of its merits, but their conversion was announced by Wernher von Braun at a briefing on June 7, 1962.
But even after NASA reached internal agreement, it was far from smooth sailing. Kennedy's science advisor Jerome Wiesner, who had expressed his opposition to human spaceflight to Kennedy before the President took office, and had opposed the decision to land people on the Moon, hired Golovin, who had left NASA, to chair his own "Space Vehicle Panel", ostensibly to monitor, but actually to second-guess NASA's decisions on the Saturn V launch vehicle and LOR by forcing Shea, Seamans, and even Webb to defend themselves, delaying its formal announcement to the press on July 11, 1962, and forcing Webb to still hedge the decision as "tentative".
Wiesner kept up the pressure, even making the disagreement public during a two-day September visit by the President to Marshall Space Flight Center. Wiesner blurted out "No, that's no good" in front of the press, during a presentation by von Braun. Webb jumped in and defended von Braun, until Kennedy ended the squabble by stating that the matter was "still subject to final review". Webb held firm and issued a request for proposal to candidate Lunar Excursion Module (LEM) contractors. Wiesner finally relented, unwilling to settle the dispute once and for all in Kennedy's office, because of the President's involvement with the October Cuban Missile Crisis, and fear of Kennedy's support for Webb. NASA announced the selection of Grumman as the LEM contractor in November 1962.
Space historian James Hansen concludes that:
The LOR method had the advantage of allowing the lander spacecraft to be used as a "lifeboat" in the event of a failure of the command ship. Some documents prove this theory was discussed before and after the method was chosen. In 1964 an MSC study concluded, "The LM [as lifeboat]... was finally dropped, because no single reasonable CSM failure could be identified that would prohibit use of the SPS." Ironically, just such a failure happened on Apollo 13 when an oxygen tank explosion left the CSM without electrical power. The lunar module provided propulsion, electrical power and life support to get the crew home safely. |
Apollo program | Spacecraft | Spacecraft
thumb|An Apollo boilerplate command module is on exhibit in the Meteor Crater Visitor Center in Winslow, Arizona.
Faget's preliminary Apollo design employed a cone-shaped command module, supported by one of several service modules providing propulsion and electrical power, sized appropriately for the space station, cislunar, and lunar landing missions. Once Kennedy's Moon landing goal became official, detailed design began of a command and service module (CSM) in which the crew would spend the entire direct-ascent mission and lift off from the lunar surface for the return trip, after being soft-landed by a larger landing propulsion module. The final choice of lunar orbit rendezvous changed the CSM's role to the translunar ferry used to transport the crew, along with a new spacecraft, the Lunar Excursion Module (LEM, later shortened to LM (Lunar Module) but still pronounced ) which would take two individuals to the lunar surface and return them to the CSM. |
Apollo program | Command and service module | Command and service module
thumb|upright=1.2|left|Apollo 15 CSM Endeavour in lunar orbit|alt=The cone-shaped command module, attached to the cylindrical service module, orbits the Moon with a panel removed, exposing the scientific instrument module
The command module (CM) was the conical crew cabin, designed to carry three astronauts from launch to lunar orbit and back to an Earth ocean landing. It was the only component of the Apollo spacecraft to survive without major configuration changes as the program evolved from the early Apollo study designs. Its exterior was covered with an ablative heat shield, and had its own reaction control system (RCS) engines to control its attitude and steer its atmospheric entry path. Parachutes were carried to slow its descent to splashdown. The module was tall, in diameter, and weighed approximately .
thumb|Original cockpit of the command module of Apollo 11 with three seats, photographed from above. It is located in the National Air and Space Museum; the very high resolution image was produced in 2007 by the Smithsonian Institution.
A cylindrical service module (SM) supported the command module, with a service propulsion engine and an RCS with propellants, and a fuel cell power generation system with liquid hydrogen and liquid oxygen reactants. A high-gain S-band antenna was used for long-distance communications on the lunar flights. On the extended lunar missions, an orbital scientific instrument package was carried. The service module was discarded just before reentry. The module was long and in diameter. The initial lunar flight version weighed approximately fully fueled, while a later version designed to carry a lunar orbit scientific instrument package weighed just over .
North American Aviation won the contract to build the CSM, and also the second stage of the Saturn V launch vehicle for NASA. Because the CSM design was started early before the selection of lunar orbit rendezvous, the service propulsion engine was sized to lift the CSM off the Moon, and thus was oversized to about twice the thrust required for translunar flight.Wilford 1969, p. 167 Also, there was no provision for docking with the lunar module. A 1964 program definition study concluded that the initial design should be continued as Block I which would be used for early testing, while Block II, the actual lunar spacecraft, would incorporate the docking equipment and take advantage of the lessons learned in Block I development. |
Apollo program | Apollo Lunar Module | Apollo Lunar Module
thumb|upright=1.2|Apollo 11 Lunar Module Eagle (and Buzz Aldrin) on the Moon, photographed by Neil Armstrong
The Apollo Lunar Module (LM) was designed to descend from lunar orbit to land two astronauts on the Moon and take them back to orbit to rendezvous with the command module. Not designed to fly through the Earth's atmosphere or return to Earth, its fuselage was designed totally without aerodynamic considerations and was of an extremely lightweight construction. It consisted of separate descent and ascent stages, each with its own engine. The descent stage contained storage for the descent propellant, surface stay consumables, and surface exploration equipment. The ascent stage contained the crew cabin, ascent propellant, and a reaction control system. The initial LM model weighed approximately , and allowed surface stays up to around 34 hours. An extended lunar module (ELM) weighed over , and allowed surface stays of more than three days. The contract for design and construction of the lunar module was awarded to Grumman Aircraft Engineering Corporation, and the project was overseen by Thomas J. Kelly. |
Apollo program | Launch vehicles | Launch vehicles
thumb|right|upright=1.35|Four Apollo rocket assemblies, drawn to scale: Little Joe II, Saturn I, Saturn IB, and Saturn V
Before the Apollo program began, Wernher von Braun and his team of rocket engineers had started work on plans for very large launch vehicles, the Saturn series, and the even larger Nova series. In the midst of these plans, von Braun was transferred from the Army to NASA and was made Director of the Marshall Space Flight Center. The initial direct ascent plan to send the three-person Apollo command and service module directly to the lunar surface, on top of a large descent rocket stage, would require a Nova-class launcher, with a lunar payload capability of over . The June 11, 1962, decision to use lunar orbit rendezvous enabled the Saturn V to replace the Nova, and the MSFC proceeded to develop the Saturn rocket family for Apollo.
Since Apollo, like Mercury, used more than one launch vehicle for space missions, NASA used spacecraft-launch vehicle combination series numbers: AS-10x for Saturn I, AS-20x for Saturn IB, and AS-50x for Saturn V (compare Mercury-Redstone 3, Mercury-Atlas 6) to designate and plan all missions, rather than numbering them sequentially as in Project Gemini. This was changed by the time human flights began. |
Apollo program | Little Joe II | Little Joe II
Since Apollo, like Mercury, would require a launch escape system (LES) in case of a launch failure, a relatively small rocket was required for qualification flight testing of this system. A rocket bigger than the Little Joe used by Mercury would be required, so the Little Joe II was built by General Dynamics/Convair. After an August 1963 qualification test flight,Townsend 1973, p. 14 four LES test flights (A-001 through 004) were made at the White Sands Missile Range between May 1964 and January 1966.Townsend 1973, p. 22 |
Apollo program | Saturn I | Saturn I
thumb|right|upright=0.7|A Saturn IB rocket launches Apollo 7, 1968
Saturn I, the first US heavy lift launch vehicle, was initially planned to launch partially equipped CSMs in low Earth orbit tests. The S-I first stage burned RP-1 with liquid oxygen (LOX) oxidizer in eight clustered Rocketdyne H-1 engines, to produce of thrust. The S-IV second stage used six liquid hydrogen-fueled Pratt & Whitney RL-10 engines with of thrust. The S-V third stage flew inactively on Saturn I four times.Dawson & Bowles 2004, p. 85. See footnote 61.
The first four Saturn I test flights were launched from LC-34, with only the first stage live, carrying dummy upper stages filled with water. The first flight with a live S-IV was launched from LC-37. This was followed by five launches of boilerplate CSMs (designated AS-101 through AS-105) into orbit in 1964 and 1965. The last three of these further supported the Apollo program by also carrying Pegasus satellites, which verified the safety of the translunar environment by measuring the frequency and severity of micrometeorite impacts.
In September 1962, NASA planned to launch four crewed CSM flights on the Saturn I from late 1965 through 1966, concurrent with Project Gemini. The payload capacity would have severely limited the systems which could be included, so the decision was made in October 1963 to use the uprated Saturn IB for all crewed Earth orbital flights. |
Apollo program | Saturn IB | Saturn IB
The Saturn IB was an upgraded version of the Saturn I. The S-IB first stage increased the thrust to by uprating the H-1 engine. The second stage replaced the S-IV with the S-IVB-200, powered by a single J-2 engine burning liquid hydrogen fuel with LOX, to produce of thrust. A restartable version of the S-IVB was used as the third stage of the Saturn V. The Saturn IB could send over into low Earth orbit, sufficient for a partially fueled CSM or the LM. Saturn IB launch vehicles and flights were designated with an AS-200 series number, "AS" indicating "Apollo Saturn" and the "2" indicating the second member of the Saturn rocket family. |
Apollo program | Saturn V | Saturn V
thumb|upright=0.7|A Saturn V rocket launches Apollo 11, 1969
Saturn V launch vehicles and flights were designated with an AS-500 series number, "AS" indicating "Apollo Saturn" and the "5" indicating Saturn V. The three-stage Saturn V was designed to send a fully fueled CSM and LM to the Moon. It was in diameter and stood tall with its lunar payload. Its capability grew to for the later advanced lunar landings. The S-IC first stage burned RP-1/LOX for a rated thrust of , which was upgraded to . The second and third stages burned liquid hydrogen; the third stage was a modified version of the S-IVB, with thrust increased to and capability to restart the engine for translunar injection after reaching a parking orbit. |
Apollo program | Astronauts | Astronauts
thumb|left|Apollo 1 crew: Ed White, command pilot Gus Grissom, and Roger Chaffee
NASA's director of flight crew operations during the Apollo program was Donald K. "Deke" Slayton, one of the original Mercury Seven astronauts who was medically grounded in September 1962 due to a heart murmur. Slayton was responsible for making all Gemini and Apollo crew assignments.
Thirty-two astronauts were assigned to fly missions in the Apollo program. Twenty-four of these left Earth's orbit and flew around the Moon between December 1968 and December 1972 (three of them twice). Half of the 24 walked on the Moon's surface, though none of them returned to it after landing once. One of the moonwalkers was a trained geologist. Of the 32, Gus Grissom, Ed White, and Roger Chaffee were killed during a ground test in preparation for the Apollo 1 mission.
thumb|right|Apollo 11 crew, from left: Commander Neil Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Buzz Aldrin
The Apollo astronauts were chosen from the Project Mercury and Gemini veterans, plus from two later astronaut groups. All missions were commanded by Gemini or Mercury veterans. Crews on all development flights (except the Earth orbit CSM development flights) through the first two landings on Apollo 11 and Apollo 12, included at least two (sometimes three) Gemini veterans. Harrison Schmitt, a geologist, was the first NASA scientist astronaut to fly in space, and landed on the Moon on the last mission, Apollo 17. Schmitt participated in the lunar geology training of all of the Apollo landing crews.
NASA awarded all 32 of these astronauts its highest honor, the Distinguished Service Medal, given for "distinguished service, ability, or courage", and personal "contribution representing substantial progress to the NASA mission". The medals were awarded posthumously to Grissom, White, and Chaffee in 1969, then to the crews of all missions from Apollo 8 onward. The crew that flew the first Earth orbital test mission Apollo 7, Walter M. Schirra, Donn Eisele, and Walter Cunningham, were awarded the lesser NASA Exceptional Service Medal, because of discipline problems with the flight director's orders during their flight. In October 2008, the NASA Administrator decided to award them the Distinguished Service Medals. For Schirra and Eisele, this was posthumously. |
Apollo program | Lunar mission profile | Lunar mission profile
The first lunar landing mission was planned to proceed: |
Apollo program | Profile variations | Profile variations
thumb|Neil Armstrong pilots the Apollo Lunar Module Eagle and lands himself and navigator Buzz Aldrin on the Moon, July 20, 1969.
The first three lunar missions (Apollo 8, Apollo 10, and Apollo 11) used a free return trajectory, keeping a flight path coplanar with the lunar orbit, which would allow a return to Earth in case the SM engine failed to make lunar orbit insertion. Landing site lighting conditions on later missions dictated a lunar orbital plane change, which required a course change maneuver soon after TLI, and eliminated the free-return option.
After Apollo 12 placed the second of several seismometers on the Moon, the jettisoned LM ascent stages on Apollo 12 and later missions were deliberately crashed on the Moon at known locations to induce vibrations in the Moon's structure. The only exceptions to this were the Apollo 13 LM which burned up in the Earth's atmosphere, and Apollo 16, where a loss of attitude control after jettison prevented making a targeted impact.
As another active seismic experiment, the S-IVBs on Apollo 13 and subsequent missions were deliberately crashed on the Moon instead of being sent to solar orbit.
Starting with Apollo 13, descent orbit insertion was to be performed using the service module engine instead of the LM engine, in order to allow a greater fuel reserve for landing. This was actually done for the first time on Apollo 14, since the Apollo 13 mission was aborted before landing. |
Apollo program | Development history | Development history |
Apollo program | Uncrewed flight tests | Uncrewed flight tests
thumb|The Journeys of Apollo, a NASA documentary about the Apollo program
Two Block I CSMs were launched from LC-34 on suborbital flights in 1966 with the Saturn IB. The first, AS-201 launched on February 26, reached an altitude of and splashed down downrange in the Atlantic Ocean. The second, AS-202 on August 25, reached altitude and was recovered downrange in the Pacific Ocean. These flights validated the service module engine and the command module heat shield.
A third Saturn IB test, AS-203 launched from pad 37, went into orbit to support design of the S-IVB upper stage restart capability needed for the Saturn V. It carried a nose cone instead of the Apollo spacecraft, and its payload was the unburned liquid hydrogen fuel, the behavior of which engineers measured with temperature and pressure sensors, and a TV camera. This flight occurred on July 5, before AS-202, which was delayed because of problems getting the Apollo spacecraft ready for flight. |
Apollo program | Preparation for crewed flight | Preparation for crewed flight
Two crewed orbital Block I CSM missions were planned: AS-204 and AS-205. The Block I crew positions were titled Command Pilot, Senior Pilot, and Pilot. The Senior Pilot would assume navigation duties, while the Pilot would function as a systems engineer. The astronauts would wear a modified version of the Gemini spacesuit.
After an uncrewed LM test flight AS-206, a crew would fly the first Block II CSM and LM in a dual mission known as AS-207/208, or AS-278 (each spacecraft would be launched on a separate Saturn IB). The Block II crew positions were titled Commander, Command Module Pilot, and Lunar Module Pilot. The astronauts would begin wearing a new Apollo A6L spacesuit, designed to accommodate lunar extravehicular activity (EVA). The traditional visor helmet was replaced with a clear "fishbowl" type for greater visibility, and the lunar surface EVA suit would include a water-cooled undergarment.
Deke Slayton, the grounded Mercury astronaut who became director of flight crew operations for the Gemini and Apollo programs, selected the first Apollo crew in January 1966, with Grissom as Command Pilot, White as Senior Pilot, and rookie Donn F. Eisele as Pilot. But Eisele dislocated his shoulder twice aboard the KC135 weightlessness training aircraft, and had to undergo surgery on January 27. Slayton replaced him with Chaffee. NASA announced the final crew selection for AS-204 on March 21, 1966, with the backup crew consisting of Gemini veterans James McDivitt and David Scott, with rookie Russell L. "Rusty" Schweickart. Mercury/Gemini veteran Wally Schirra, Eisele, and rookie Walter Cunningham were announced on September 29 as the prime crew for AS-205.
In December 1966, the AS-205 mission was canceled, since the validation of the CSM would be accomplished on the 14-day first flight, and AS-205 would have been devoted to space experiments and contribute no new engineering knowledge about the spacecraft. Its Saturn IB was allocated to the dual mission, now redesignated AS-205/208 or AS-258, planned for August 1967. McDivitt, Scott and Schweickart were promoted to the prime AS-258 crew, and Schirra, Eisele and Cunningham were reassigned as the Apollo1 backup crew. |
Apollo program | Program delays | Program delays
The spacecraft for the AS-202 and AS-204 missions were delivered by North American Aviation to the Kennedy Space Center with long lists of equipment problems which had to be corrected before flight; these delays caused the launch of AS-202 to slip behind AS-203, and eliminated hopes the first crewed mission might be ready to launch as soon as November 1966, concurrently with the last Gemini mission. Eventually, the planned AS-204 flight date was pushed to February 21, 1967.
North American Aviation was prime contractor not only for the Apollo CSM, but for the SaturnV S-II second stage as well, and delays in this stage pushed the first uncrewed SaturnV flight AS-501 from late 1966 to November 1967. (The initial assembly of AS-501 had to use a dummy spacer spool in place of the stage.)
The problems with North American were severe enough in late 1965 to cause Manned Space Flight Administrator George Mueller to appoint program director Samuel Phillips to head a "tiger team" to investigate North American's problems and identify corrections. Phillips documented his findings in a December 19 letter to NAA president Lee Atwood, with a strongly worded letter by Mueller, and also gave a presentation of the results to Mueller and Deputy Administrator Robert Seamans.NASA never volunteered the tiger team findings to the US Congress in the course of its regular oversight, but its existence was publicly disclosed as "the Phillips report" in the course of the Senate investigation into the Apollo 204 fire. Meanwhile, Grumman was also encountering problems with the Lunar Module, eliminating hopes it would be ready for crewed flight in 1967, not long after the first crewed CSM flights. |
Apollo program | Apollo 1 fire | Apollo 1 fire
thumb|right|Charred Apollo 1 cabin interior
Grissom, White, and Chaffee decided to name their flight Apollo1 as a motivational focus on the first crewed flight. They trained and conducted tests of their spacecraft at North American, and in the altitude chamber at the Kennedy Space Center. A "plugs-out" test was planned for January, which would simulate a launch countdown on LC-34 with the spacecraft transferring from pad-supplied to internal power. If successful, this would be followed by a more rigorous countdown simulation test closer to the February 21 launch, with both spacecraft and launch vehicle fueled.
The plugs-out test began on the morning of January 27, 1967, and immediately was plagued with problems. First, the crew noticed a strange odor in their spacesuits which delayed the sealing of the hatch. Then, communications problems frustrated the astronauts and forced a hold in the simulated countdown. During this hold, an electrical fire began in the cabin and spread quickly in the high pressure, 100% oxygen atmosphere. Pressure rose high enough from the fire that the cabin inner wall burst, allowing the fire to erupt onto the pad area and frustrating attempts to rescue the crew. The astronauts were asphyxiated before the hatch could be opened.
thumb|Block II spacesuit in January 1968, before (left) and after changes recommended after the Apollo1 fire
NASA immediately convened an accident review board, overseen by both houses of Congress. While the determination of responsibility for the accident was complex, the review board concluded that "deficiencies existed in command module design, workmanship and quality control". At the insistence of NASA Administrator Webb, North American removed Harrison Storms as command module program manager.Gray 1994 Webb also reassigned Apollo Spacecraft Program Office (ASPO) Manager Joseph Francis Shea, replacing him with George Low.Ertel et al. 1978, p. 119
To remedy the causes of the fire, changes were made in the Block II spacecraft and operational procedures, the most important of which were use of a nitrogen/oxygen mixture instead of pure oxygen before and during launch, and removal of flammable cabin and space suit materials. The Block II design already called for replacement of the Block I plug-type hatch cover with a quick-release, outward opening door. NASA discontinued the crewed Block I program, using the BlockI spacecraft only for uncrewed SaturnV flights. Crew members would also exclusively wear modified, fire-resistant A7L Block II space suits, and would be designated by the Block II titles, regardless of whether a LM was present on the flight or not. |
Apollo program | Uncrewed Saturn V and LM tests | Uncrewed Saturn V and LM tests
On April 24, 1967, Mueller published an official Apollo mission numbering scheme, using sequential numbers for all flights, crewed or uncrewed. The sequence would start with Apollo 4 to cover the first three uncrewed flights while retiring the Apollo1 designation to honor the crew, per their widows' wishes.Ertel & al. 1978, Part 1(H)
In September 1967, Mueller approved a sequence of mission types which had to be successfully accomplished in order to achieve the crewed lunar landing. Each step had to be successfully accomplished before the next ones could be performed, and it was unknown how many tries of each mission would be necessary; therefore letters were used instead of numbers. The A missions were uncrewed Saturn V validation; B was uncrewed LM validation using the Saturn IB; C was crewed CSM Earth orbit validation using the Saturn IB; D was the first crewed CSM/LM flight (this replaced AS-258, using a single Saturn V launch); E would be a higher Earth orbit CSM/LM flight; F would be the first lunar mission, testing the LM in lunar orbit but without landing (a "dress rehearsal"); and G would be the first crewed landing. The list of types covered follow-on lunar exploration to include H lunar landings, I for lunar orbital survey missions, and J for extended-stay lunar landings.Ertel et al. 1978, p. 157
The delay in the CSM caused by the fire enabled NASA to catch up on human-rating the LM and SaturnV. Apollo4 (AS-501) was the first uncrewed flight of the SaturnV, carrying a BlockI CSM on November 9, 1967. The capability of the command module's heat shield to survive a trans-lunar reentry was demonstrated by using the service module engine to ram it into the atmosphere at higher than the usual Earth-orbital reentry speed.
Apollo 5 (AS-204) was the first uncrewed test flight of the LM in Earth orbit, launched from pad 37 on January 22, 1968, by the Saturn IB that would have been used for Apollo 1. The LM engines were successfully test-fired and restarted, despite a computer programming error which cut short the first descent stage firing. The ascent engine was fired in abort mode, known as a "fire-in-the-hole" test, where it was lit simultaneously with jettison of the descent stage. Although Grumman wanted a second uncrewed test, George Low decided the next LM flight would be crewed.
This was followed on April 4, 1968, by Apollo 6 (AS-502) which carried a CSM and a LM Test Article as ballast. The intent of this mission was to achieve trans-lunar injection, followed closely by a simulated direct-return abort, using the service module engine to achieve another high-speed reentry. The Saturn V experienced pogo oscillation, a problem caused by non-steady engine combustion, which damaged fuel lines in the second and third stages. Two S-II engines shut down prematurely, but the remaining engines were able to compensate. The damage to the third stage engine was more severe, preventing it from restarting for trans-lunar injection. Mission controllers were able to use the service module engine to essentially repeat the flight profile of Apollo 4. Based on the good performance of Apollo6 and identification of satisfactory fixes to the Apollo6 problems, NASA declared the SaturnV ready to fly crew, canceling a third uncrewed test. |
Apollo program | Crewed development missions | Crewed development missions
Apollo 7, launched from LC-34 on October 11, 1968, was the Cmission, crewed by Schirra, Eisele, and Cunningham. It was an 11-day Earth-orbital flight which tested the CSM systems.
Apollo 8 was planned to be the D mission in December 1968, crewed by McDivitt, Scott and Schweickart, launched on a SaturnV instead of two Saturn IBs. In the summer it had become clear that the LM would not be ready in time. Rather than waste the Saturn V on another simple Earth-orbiting mission, ASPO Manager George Low suggested the bold step of sending Apollo8 to orbit the Moon instead, deferring the Dmission to the next mission in March 1969, and eliminating the E mission. This would keep the program on track. The Soviet Union had sent two tortoises, mealworms, wine flies, and other lifeforms around the Moon on September 15, 1968, aboard Zond 5, and it was believed they might soon repeat the feat with human cosmonauts. The decision was not announced publicly until successful completion of Apollo 7. Gemini veterans Frank Borman and Jim Lovell, and rookie William Anders captured the world's attention by making ten lunar orbits in 20 hours, transmitting television pictures of the lunar surface on Christmas Eve, and returning safely to Earth.
thumb|left|Neil Armstrong descends the LM's ladder in preparation for the first steps on the lunar surface, as televised live on July 20, 1969.
The following March, LM flight, rendezvous and docking were successfully demonstrated in Earth orbit on Apollo 9, and Schweickart tested the full lunar EVA suit with its portable life support system (PLSS) outside the LM. The F mission was successfully carried out on Apollo 10 in May 1969 by Gemini veterans Thomas P. Stafford, John Young and Eugene Cernan. Stafford and Cernan took the LM to within of the lunar surface.
The G mission was achieved on Apollo 11 in July 1969 by an all-Gemini veteran crew consisting of Neil Armstrong, Michael Collins and Buzz Aldrin. Armstrong and Aldrin performed the first landing at the Sea of Tranquility at 20:17:40 UTC on July 20, 1969. They spent a total of 21 hours, 36 minutes on the surface, and spent 2hours, 31 minutes outside the spacecraft, walking on the surface, taking photographs, collecting material samples, and deploying automated scientific instruments, while continuously sending black-and-white television back to Earth. The astronauts returned safely on July 24. |
Apollo program | Production lunar landings | Production lunar landings
In November 1969, Charles "Pete" Conrad became the third person to step onto the Moon, which he did while speaking more informally than had Armstrong:
Conrad and rookie Alan L. Bean made a precision landing of Apollo 12 within walking distance of the Surveyor 3 uncrewed lunar probe, which had landed in April 1967 on the Ocean of Storms. The command module pilot was Gemini veteran Richard F. Gordon Jr. Conrad and Bean carried the first lunar surface color television camera, but it was damaged when accidentally pointed into the Sun. They made two EVAs totaling 7hours and 45 minutes. On one, they walked to the Surveyor, photographed it, and removed some parts which they returned to Earth.
The contracted batch of 15 Saturn Vs was enough for lunar landing missions through Apollo 20. Shortly after Apollo 11, NASA publicized a preliminary list of eight more planned landing sites after Apollo 12, with plans to increase the mass of the CSM and LM for the last five missions, along with the payload capacity of the Saturn V. These final missions would combine the I and J types in the 1967 list, allowing the CMP to operate a package of lunar orbital sensors and cameras while his companions were on the surface, and allowing them to stay on the Moon for over three days. These missions would also carry the Lunar Roving Vehicle (LRV) increasing the exploration area and allowing televised liftoff of the LM. Also, the Block II spacesuit was revised for the extended missions to allow greater flexibility and visibility for driving the LRV.
thumb|left|Apollo landings on the Moon, 1969–1972
The success of the first two landings allowed the remaining missions to be crewed with a single veteran as commander, with two rookies. Apollo 13 launched Lovell, Jack Swigert, and Fred Haise in April 1970, headed for the Fra Mauro formation. But two days out, a liquid oxygen tank exploded, disabling the service module and forcing the crew to use the LM as a "lifeboat" to return to Earth. Another NASA review board was convened to determine the cause, which turned out to be a combination of damage of the tank in the factory, and a subcontractor not making a tank component according to updated design specifications. Apollo was grounded again, for the remainder of 1970 while the oxygen tank was redesigned and an extra one was added. |
Apollo program | Mission cutbacks | Mission cutbacks
About the time of the first landing in 1969, it was decided to use an existing Saturn V to launch the Skylab orbital laboratory pre-built on the ground, replacing the original plan to construct it in orbit from several Saturn IB launches; this eliminated Apollo 20. NASA's yearly budget also began to shrink in light of the successful landing, and NASA also had to make funds available for the development of the upcoming Space Shuttle. By 1971, the decision was made to also cancel missions 18 and 19. The two unused Saturn Vs became museum exhibits at the John F. Kennedy Space Center on Merritt Island, Florida, George C. Marshall Space Center in Huntsville, Alabama, Michoud Assembly Facility in New Orleans, Louisiana, and Lyndon B. Johnson Space Center in Houston, Texas.
The cutbacks forced mission planners to reassess the original planned landing sites in order to achieve the most effective geological sample and data collection from the remaining four missions. Apollo 15 had been planned to be the last of the H series missions, but since there would be only two subsequent missions left, it was changed to the first of three J missions.
Apollo 13's Fra Mauro mission was reassigned to Apollo 14, commanded in February 1971 by Mercury veteran Alan Shepard, with Stuart Roosa and Edgar Mitchell. This time the mission was successful. Shepard and Mitchell spent 33 hours and 31 minutes on the surface, and completed two EVAs totalling 9hours 24 minutes, which was a record for the longest EVA by a lunar crew at the time.
In August 1971, just after conclusion of the Apollo 15 mission, President Richard Nixon proposed canceling the two remaining lunar landing missions, Apollo 16 and 17. Office of Management and Budget Deputy Director Caspar Weinberger was opposed to this, and persuaded Nixon to keep the remaining missions."MEMORANDUM FOR THE PRESIDENT" by Caspar Weinberger (via George Shultz), Aug 12, 1971, Page32(of 39) |
Apollo program | Extended missions | Extended missions
thumb|Lunar Roving Vehicle used on Apollos 15–17
Apollo 15 was launched on July 26, 1971, with David Scott, Alfred Worden and James Irwin. Scott and Irwin landed on July 30 near Hadley Rille, and spent just under two days, 19 hours on the surface. In over 18 hours of EVA, they collected about of lunar material.
Apollo 16 landed in the Descartes Highlands on April 20, 1972. The crew was commanded by John Young, with Ken Mattingly and Charles Duke. Young and Duke spent just under three days on the surface, with a total of over 20 hours EVA.
Apollo 17 was the last of the Apollo program, landing in the Taurus–Littrow region in December 1972. Eugene Cernan commanded Ronald E. Evans and NASA's first scientist-astronaut, geologist Harrison H. Schmitt. Schmitt was originally scheduled for Apollo 18, but the lunar geological community lobbied for his inclusion on the final lunar landing. Cernan and Schmitt stayed on the surface for just over three days and spent just over 23 hours of total EVA. |
Apollo program | Canceled missions | Canceled missions
Several missions were planned for but were canceled before details were finalized. |
Apollo program | Mission summary | Mission summary
Designation Date Crew Summary AS-201 Feb 26, 1966 AS-201 CSM-009 First flight of Saturn IB and Block I CSM; suborbital to Atlantic Ocean; qualified heat shield to orbital reentry speed. AS-203 Jul 5, 1966 AS-203 No spacecraft; observations of liquid hydrogen fuel behavior in orbit to support design of S-IVB restart capability. AS-202 Aug 25, 1966 AS-202 CSM-011 Suborbital flight of CSM to Pacific Ocean. Apollo 1 Feb 21, 1967 SA-204 CSM-012 Gus GrissomEd WhiteRoger B. Chaffee Not flown. All crew members died in a fire during a launch pad test on January 27, 1967. Apollo 4 Nov 9, 1967 SA-501 CSM-017 LTA-10R First test flight of Saturn V, placed a CSM in a high Earth orbit; demonstrated S-IVB restart; qualified CM heat shield to lunar reentry speed. Apollo 5 Jan 22–23, 1968 SA-204 LM-1 Earth orbital flight test of LM, launched on Saturn IB; demonstrated ascent and descent propulsion; human-rated the LM. No crew. Apollo 6 Apr 4, 1968 SA-502 CM-020SM-014 LTA-2R Uncrewed, second flight of Saturn V, attempted demonstration of trans-lunar injection, and direct-return abort using SM engine; three engine failures, including failure of S-IVB restart. Flight controllers used SM engine to repeat Apollo 4's flight profile. Human-rated the Saturn V. Apollo 7 Oct 11–22, 1968 SA-205 CSM-101 Wally SchirraWalt CunninghamDonn Eisele First crewed Earth orbital demonstration of Block II CSM, launched on Saturn IB. First live television broadcast from a crewed mission. Apollo 8 Dec 21–27, 1968 SA-503 CSM-103 LTA-B Frank BormanJames LovellWilliam Anders First crewed flight of Saturn V; First crewed flight to Moon; CSM made 10 lunar orbits in 20 hours. Apollo 9 Mar 3–13, 1969 SA-504 CSM-104Gumdrop LM-3Spider James McDivitt David ScottRussell Schweickart Second crewed flight of Saturn V; First crewed flight of CSM and LM in Earth orbit; demonstrated portable life support system to be used on the lunar surface. Apollo 10 May 18–26, 1969 SA-505 CSM-106Charlie Brown LM-4Snoopy Thomas StaffordJohn YoungEugene Cernan Dress rehearsal for first lunar landing; flew LM down to from lunar surface. Apollo 11 Jul 16–24, 1969 SA-506 CSM-107Columbia LM-5 Eagle Neil ArmstrongMichael CollinsBuzz Aldrin First landing, in Tranquility Base, Sea of Tranquility. Surface EVA time: 2h 31m. Samples returned: . Apollo 12 Nov 14–24, 1969 SA-507 CSM-108Yankee Clipper LM-6Intrepid Pete ConradRichard GordonAlan Bean Second landing, in Ocean of Storms near Surveyor 3. Surface EVA time: 7h 45m. Samples returned: . Apollo 13 Apr 11–17, 1970 SA-508 CSM-109Odyssey LM-7Aquarius James LovellJack SwigertFred Haise Third landing attempt aborted in transit to the Moon, due to SM failure. Crew used LM as "lifeboat" to return to Earth. Mission called a "successful failure". Apollo 14 Jan 31 – Feb 9, 1971 SA-509 CSM-110Kitty Hawk LM-8Antares Alan ShepardStuart RoosaEdgar Mitchell Third landing, in Fra Mauro formation. Surface EVA time: 9h 21m. Samples returned: . Apollo 15 Jul 26 – Aug 7, 1971 SA-510 CSM-112Endeavour LM-10Falcon David ScottAlfred WordenJames Irwin Fourth landing, in Hadley-Apennine. First extended mission, used Rover on Moon. Surface EVA time: 18h 33m. Samples returned: . Apollo 16 Apr 16–27, 1972 SA-511 CSM-113Casper LM-11Orion John YoungKen MattinglyCharles Duke Fifth landing, in Plain of Descartes. Second extended mission, used Rover on Moon. Surface EVA time: 20h 14m. Samples returned: . Apollo 17 Dec 7–19, 1972 SA-512 CSM-114America LM-12Challenger Eugene CernanRonald EvansHarrison Schmitt Only Saturn V night launch. Sixth landing, in Taurus–Littrow. Third extended mission, used Rover on Moon. First geologist on the Moon. Apollo's last crewed Moon landing. Surface EVA time: 22h 2m. Samples returned: .
Source: Apollo by the Numbers: A Statistical Reference (Orloff 2004). |
Apollo program | Samples returned | Samples returned
The Apollo program returned over of lunar rocks and soil to the Lunar Receiving Laboratory in Houston. Today, 75% of the samples are stored at the Lunar Sample Laboratory Facility built in 1979.
The rocks collected from the Moon are extremely old compared to rocks found on Earth, as measured by radiometric dating techniques. They range in age from about 3.2 billion years for the basaltic samples derived from the lunar maria, to about 4.6 billion years for samples derived from the highlands crust.Papike et al. 1998, pp. 5-001–5-234 As such, they represent samples from a very early period in the development of the Solar System, that are largely absent on Earth. One important rock found during the Apollo Program is dubbed the Genesis Rock, retrieved by astronauts David Scott and James Irwin during the Apollo 15 mission. This anorthosite rock is composed almost exclusively of the calcium-rich feldspar mineral anorthite, and is believed to be representative of the highland crust. A geochemical component called KREEP was discovered by Apollo 12, which has no known terrestrial counterpart. KREEP and the anorthositic samples have been used to infer that the outer portion of the Moon was once completely molten (see lunar magma ocean).
Almost all the rocks show evidence of impact process effects. Many samples appear to be pitted with micrometeoroid impact craters, which is never seen on Earth rocks, due to the thick atmosphere. Many show signs of being subjected to high-pressure shock waves that are generated during impact events. Some of the returned samples are of impact melt (materials melted near an impact crater.) All samples returned from the Moon are highly brecciated as a result of being subjected to multiple impact events.
From analyses of the composition of the returned lunar samples, it is now believed that the Moon was created through the impact of a large astronomical body with Earth.Burrows 1999, p. 431 |
Apollo program | Costs | Costs
Apollo cost $25.4 billion or approximately $257 billion (2023) using improved cost analysis.
Of this amount, $20.2 billion ($ adjusted) was spent on the design, development, and production of the Saturn family of launch vehicles, the Apollo spacecraft, spacesuits, scientific experiments, and mission operations. The cost of constructing and operating Apollo-related ground facilities, such as the NASA human spaceflight centers and the global tracking and data acquisition network, added an additional $5.2 billion ($ adjusted).
The amount grows to $28 billion ($280 billion adjusted) if the costs for related projects such as Project Gemini and the robotic Ranger, Surveyor, and Lunar Orbiter programs are included.
NASA's official cost breakdown, as reported to Congress in the Spring of 1973, is as follows:
Project Apollo Cost (original, billion $) Apollo spacecraft 8.5 Saturn launch vehicles 9.1 Launch vehicle engine development 0.9 Operations 1.7 Total R&D 20.2 Tracking and data acquisition 0.9 Ground facilities 1.8 Operation of installations 2.5 Total 25.4
Accurate estimates of human spaceflight costs were difficult in the early 1960s, as the capability was new and management experience was lacking. Preliminary cost analysis by NASA estimated $7 billion – $12 billion for a crewed lunar landing effort. NASA Administrator James Webb increased this estimate to $20 billion before reporting it to Vice President Johnson in April 1961.
Project Apollo was a massive undertaking, representing the largest research and development project in peacetime. At its peak, it employed over 400,000 employees and contractors around the country and accounted for more than half of NASA's total spending in the 1960s. After the first Moon landing, public and political interest waned, including that of President Nixon, who wanted to rein in federal spending. NASA's budget could not sustain Apollo missions which cost, on average, $445 million ($ adjusted) each while simultaneously developing the Space Shuttle. The final fiscal year of Apollo funding was 1973. |
Apollo program | Apollo Applications Program | Apollo Applications Program
Looking beyond the crewed lunar landings, NASA investigated several post-lunar applications for Apollo hardware. The Apollo Extension Series (Apollo X) proposed up to 30 flights to Earth orbit, using the space in the Spacecraft Lunar Module Adapter (SLA) to house a small orbital laboratory (workshop). Astronauts would continue to use the CSM as a ferry to the station. This study was followed by design of a larger orbital workshop to be built in orbit from an empty S-IVB Saturn upper stage and grew into the Apollo Applications Program (AAP). The workshop was to be supplemented by the Apollo Telescope Mount, which could be attached to the ascent stage of the lunar module via a rack. The most ambitious plan called for using an empty S-IVB as an interplanetary spacecraft for a Venus fly-by mission.
The S-IVB orbital workshop was the only one of these plans to make it off the drawing board. Dubbed Skylab, it was assembled on the ground rather than in space, and launched in 1973 using the two lower stages of a Saturn V. It was equipped with an Apollo Telescope Mount. Skylab's last crew departed the station on February 8, 1974, and the station itself re-entered the atmosphere in 1979 after development of the Space Shuttle was delayed too long to save it.
The Apollo–Soyuz program also used Apollo hardware for the first joint nation spaceflight, paving the way for future cooperation with other nations in the Space Shuttle and International Space Station programs. |
Apollo program | Recent observations | Recent observations
thumb|right|Tranquility Base, imaged in March 2012 by the Lunar Reconnaissance Orbiter
In 2008, Japan Aerospace Exploration Agency's SELENE probe observed evidence of the halo surrounding the Apollo 15 Lunar Module blast crater while orbiting above the lunar surface.
Beginning in 2009, NASA's robotic Lunar Reconnaissance Orbiter, while orbiting above the Moon, photographed the remnants of the Apollo program left on the lunar surface, and each site where crewed Apollo flights landed. All of the U.S. flags left on the Moon during the Apollo missions were found to still be standing, with the exception of the one left during the Apollo 11 mission, which was blown over during that mission's lift-off from the lunar surface; the degree to which these flags retain their original colors remains unknown. The flags cannot be seen through a telescope from Earth.
In a November 16, 2009, editorial, The New York Times opined: |
Apollo program | Legacy | Legacy |
Apollo program | Science and engineering | Science and engineering
thumb|Margaret Hamilton standing next to the navigation software that she and her MIT team produced for the Apollo project
The Apollo program has been described as the greatest technological achievement in human history. Apollo stimulated many areas of technology, leading to over 1,800 spinoff products as of 2015, including advances in the development of cordless power tools, fireproof materials, heart monitors, solar panels, digital imaging, and the use of liquid methane as fuel. The flight computer design used in both the lunar and command modules was, along with the Polaris and Minuteman missile systems, the driving force behind early research into integrated circuits (ICs). By 1963, Apollo was using 60 percent of the United States' production of ICs. The crucial difference between the requirements of Apollo and the missile programs was Apollo's much greater need for reliability. While the Navy and Air Force could work around reliability problems by deploying more missiles, the political and financial cost of failure of an Apollo mission was unacceptably high.
Technologies and techniques required for Apollo were developed by Project Gemini. The Apollo project was enabled by NASA's adoption of new advances in semiconductor electronic technology, including metal–oxide–semiconductor field-effect transistors (MOSFETs) in the Interplanetary Monitoring Platform (IMP) and silicon integrated circuit chips in the Apollo Guidance Computer (AGC). |
Apollo program | Cultural impact | Cultural impact
thumb|right|The Blue Marble photograph taken on December7, 1972, during Apollo 17. "We went to explore the Moon, and in fact discovered the Earth." —Eugene Cernan
The crew of Apollo 8 sent the first live televised pictures of the Earth and the Moon back to Earth, and read from the creation story in the Book of Genesis, on Christmas Eve 1968. An estimated one-quarter of the population of the world saw—either live or delayed—the Christmas Eve transmission during the ninth orbit of the Moon,Chaikin 1994, p. 120 and an estimated one-fifth of the population of the world watched the live transmission of the Apollo 11 moonwalk.Burrows 1999, p. 429
The Apollo program also affected environmental activism in the 1970s due to photos taken by the astronauts. The most well known include Earthrise, taken by William Anders on Apollo 8, and The Blue Marble, taken by the Apollo 17 astronauts. The Blue Marble was released during a surge in environmentalism, and became a symbol of the environmental movement as a depiction of Earth's frailty, vulnerability, and isolation amid the vast expanse of space.
According to The Economist, Apollo succeeded in accomplishing President Kennedy's goal of taking on the Soviet Union in the Space Race by accomplishing a singular and significant achievement, to demonstrate the superiority of the free-market system. The publication noted the irony that in order to achieve the goal, the program required the organization of tremendous public resources within a vast, centralized government bureaucracy. |
Apollo program | Apollo 11 broadcast data restoration project | Apollo 11 broadcast data restoration project
Prior to Apollo 11's 40th anniversary in 2009, NASA searched for the original videotapes of the mission's live televised moonwalk. After an exhaustive three-year search, it was concluded that the tapes had probably been erased and reused. A new digitally remastered version of the best available broadcast television footage was released instead. |
Apollo program | Depictions on film | Depictions on film |
Apollo program | Documentaries | Documentaries
Numerous documentary films cover the Apollo program and the Space Race, including:
Footprints on the Moon (1969)
Moonwalk One (1970)
The Greatest Adventure (1978)
For All Mankind (1989)
Moon Shot (1994 miniseries)
"Moon" from the BBC miniseries The Planets (1999)
Magnificent Desolation: Walking on the Moon 3D (2005)
The Wonder of It All (2007)
In the Shadow of the Moon (2007)
When We Left Earth: The NASA Missions (2008 miniseries)
Moon Machines (2008 miniseries)
James May on the Moon (2009)
NASA's Story (2009 miniseries)
Apollo 11 (2019)
Chasing the Moon (2019 miniseries) |
Apollo program | Docudramas | Docudramas
Some missions have been dramatized:
Apollo 13 (1995)
Apollo 11 (1996)
From the Earth to the Moon (1998)
The Dish (2000)
Space Race (2005)
Moonshot (2009)
First Man (2018) |
Apollo program | Fictional | Fictional
The Apollo program has been the focus of several works of fiction, including:
Apollo 18 (2011), horror movie which was released to negative reviews.
Men in Black 3 (2012), Science Fiction/Comedy movie. Agent J played by Will Smith goes back to the Apollo 11 launch in 1969 to ensure that a global protection system is launched in to space.
For All Mankind (2019), TV series depicting an alternate history in which the Soviet Union was the first country to successfully land a man on the Moon.
Indiana Jones and the Dial of Destiny (2023), fifth Indiana Jones film, in which Jürgen Voller, a NASA member and ex-Nazi involved with the Apollo program, wants to time travel. The New York City parade for the Apollo 11 crew is portrayed as a plot point. |
Apollo program | See also | See also
Apollo 11 in popular culture
Apollo Lunar Surface Experiments Package
Exploration of the Moon
Leslie Cantwell collection
List of artificial objects on the Moon
List of crewed spacecraft
List of missions to the Moon
Soviet crewed lunar programs
Stolen and missing Moon rocks
Artemis Program |
Apollo program | Notes | Notes |
Apollo program | References | References |
Apollo program | Citations | Citations |
Apollo program | Sources | Sources
Chaikin interviewed all the surviving astronauts and others who worked with the program.
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Apollo program | Further reading | Further reading
NASA Report JSC-09423, April 1975
The autobiography of Michael Collins' experiences as an astronaut, including his flight aboard Apollo 11.
Although this book focuses on Apollo 13, it provides a wealth of background information on Apollo technology and procedures.
History of the Apollo program from Apollos 1–11, including many interviews with the Apollo astronauts.
Gleick, James, "Moon Fever" [review of Oliver Morton, The Moon: A History of the Future; Apollo's Muse: The Moon in the Age of Photography, an exhibition at the Metropolitan Museum of Art, New York City, July 3 – September 22, 2019; Douglas Brinkley, American Moonshot: John F. Kennedy and the Great Space Race; Brandon R. Brown, The Apollo Chronicles: Engineering America's First Moon Missions; Roger D. Launius, Reaching for the Moon: A Short History of the Space Race; Apollo 11, a documentary film directed by Todd Douglas Miller; and Michael Collins, Carrying the Fire: An Astronaut's Journeys (50th Anniversary Edition)], The New York Review of Books, vol. LXVI, no. 13 (15 August 2019), pp. 54–58.
Factual, from the standpoint of a flight controller during the Mercury, Gemini, and Apollo space programs.
Details the flight of Apollo 13.
Tells Grumman's story of building the lunar modules.
History of the crewed space program from 1September 1960, to 5January 1968.
Account of Deke Slayton's life as an astronaut and of his work as chief of the astronaut office, including selection of Apollo crews.
From origin to November 7, 1962
November 8, 1962 – September 30, 1964
October 1, 1964 – January 20, 1966
January 21, 1966 – July 13, 1974
The history of lunar exploration from a geologist's point of view. |
Apollo program | External links | External links
Apollo program history at NASA's Human Space Flight (HSF) website
The Apollo Program at the NASA History Program Office
The Apollo Program at the National Air and Space Museum
Apollo 35th Anniversary Interactive Feature at NASA (in Flash)
Lunar Mission Timeline at the Lunar and Planetary Institute
Apollo Collection, The University of Alabama in Huntsville Archives and Special Collections |