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Although Scott had eventually been successful at drilling the holes, he and Irwin had been unable to retrieve a core sample, and this was an early order of business during EVA 3, their third and final moonwalk. Time that could have been devoted to geology ticked away as Scott and Irwin attempted to pull it out. Once it had been retrieved, more time passed as they attempted to break the core into pieces for transport to Earth. Hampered by an incorrectly mounted vise on the rover, they eventually gave up on this—the core would be transported home with one segment longer than planned. Scott wondered if the core was worth the amount of time and effort invested, and the CAPCOM, Joe Allen, assured him it was. The core proved one of the most important items brought back from the Moon, revealing much about its history, but the expended time meant the planned visit to a group of hills known as the North Complex had to be scrubbed. Instead, the crew again ventured to the edge of Hadley Rille, this time to the northwest of the immediate landing site.
Once the astronauts were beside the LM, Scott used a kit provided by the Postal Service to cancel a first day cover of two stamps being issued on August 2, the current date. Scott then performed an experiment in view of the television camera, using a falcon feather and hammer to demonstrate Galileo's theory that all objects in a given gravity field fall at the same rate, regardless of mass, in the absence of aerodynamic drag. He dropped the hammer and feather at the same time; because of the negligible lunar atmosphere, there was no drag on the feather, which hit the ground at the same time as the hammer. This was Joe Allen's idea (he also served as CAPCOM during it) and was part of an effort to find a memorable popular science experiment to do on the Moon along the lines of Shepard's hitting of golf balls. The feather was most likely from a female gyrfalcon (a type of falcon), a mascot at the United States Air Force Academy. Scott then drove the rover to a position away from the LM, where the television camera could be used to observe the lunar liftoff. Near the rover, he left a small aluminum statuette called "Fallen Astronaut", along with a plaque bearing the names of 14 known American astronauts and Soviet cosmonauts who had died in the furtherance of space exploration. The memorial was left while the television camera was turned away; he told Mission Control he was doing some cleanup activities around the rover. Scott disclosed the memorial in a post-flight news conference. He also placed a Bible on the control panel of the rover before leaving it for the last time to enter the LM.
The EVA lasted 4 hours, 49 minutes and 50 seconds. In total, the two astronauts spent 18 hours outside the LM and collected approximately of lunar samples. Command module activities. After the departure of "Falcon", Worden in "Endeavour" executed a burn to take the CSM to a higher orbit. While "Falcon" was on the Moon, the mission effectively split, Worden and the CSM being assigned their own CAPCOM and flight support team. Worden got busy with the tasks that were to occupy him for much of the time he spent in space alone: photography and operating the instruments in the SIM bay. The door to the SIM bay had been explosively jettisoned during the translunar coast. Filling previously unused space in the service module, the SIM bay contained a gamma-ray spectrometer, mounted on the end of a boom, an X-ray spectrometer and a laser altimeter, which failed part way through the mission. Two cameras, a stellar camera and a metric camera, together comprised the mapping camera, which was complemented by a panoramic camera, derived from spy technology. The altimeter and cameras permitted the exact time and location from which pictures were taken to be determined. Also present were an alpha particle spectrometer, which could be used to detect evidence of lunar volcanism, and a mass spectrometer, also on a boom in the hope it would be unaffected by contamination from the ship. The boom would prove troublesome, as Worden would not always be able to get it to retract.
"Endeavour" was slated to pass over the landing site at the moment of planned landing, but Worden could not see "Falcon" and did not spot it until a subsequent orbit. He also exercised to avoid muscle atrophy, and Houston kept him up to date on Scott and Irwin's activities on the lunar surface. The panoramic camera did not operate perfectly, but provided enough images that no special adjustment was made. Worden took many photographs through the command module's windows, often with shots taken at regular intervals. His task was complicated by the lack of a working mission timer in the Lower Equipment Bay of the command module, as its circuit breaker had popped en route to the Moon. Worden's observations and photographs would inform the decision to send Apollo 17 to Taurus-Littrow to search for evidence of volcanic activity. There was a communications blackout when the CSM passed over the far side of the Moon from Earth; Worden greeted each resumption of contact with the words, "Hello, Earth. Greetings from "Endeavour"", expressed in different languages. Worden and El-Baz had come up with the idea, and the geology instructor had aided the astronaut in accumulating translations.
Results from the SIM bay experiments would include the conclusion, from data gathered by the X-ray spectrometer, that there was greater fluorescent X-ray flux than anticipated, and that the lunar highlands were richer in aluminum than were the mares. "Endeavour" was in a more inclined orbit than previous crewed missions, and Worden saw features that were not known previously, supplementing photographs with thorough descriptions. By the time Scott and Irwin were ready to take off from the lunar surface and return to "Endeavour", the CSM's orbit had drifted due to the rotation of the Moon, and a plane change burn was required to ensure that the CSM's orbit would be in the same plane as that of the LM once it took off from the Moon. Worden accomplished the 18-second burn with the SPS. Return to Earth. "Falcon" lifted off the Moon at 17:11:22 GMT on August2 after 66 hours and 55 minutes on the lunar surface. Docking with the CSM took place just under two hours later. After the astronauts transferred samples and other items from the LM to the CSM, the LM was sealed off, jettisoned, and intentionally crashed into the lunar surface, an impact registered by the seismometers left by Apollo 12, 14 and 15. The jettison proved difficult because of problems getting airtight seals, requiring a delay in discarding the LM. After the jettison, Slayton came on the loop to recommend the astronauts take sleeping pills, or at least that Scott and Irwin do so. Scott as mission commander refused to allow it, feeling there was no need. During the EVAs, the doctors had noticed irregularities in both Scott's and Irwin's heartbeats, but the crew were not informed during the flight. Irwin had heart problems after retiring as an astronaut and died in 1991 of a heart attack; Scott felt that he as commander should have been informed of the biomedical readings. NASA doctors at the time theorized the heart readings were due to potassium deficiency, due to their hard work on the surface and inadequate resupply through liquids.
The crew spent the next two days working on orbital science experiments, including more observations of the Moon from orbit and releasing the subsatellite. "Endeavour" departed lunar orbit with another burn of the SPS engine of 2minutes 21 seconds at 21:22:45 GMT on August4. The next day, during the return to Earth, Worden performed a 39-minute EVA to retrieve film cassettes from the service module's scientific instrument module (SIM) bay, with assistance from Irwin who remained at the command module's hatch. At approximately 171,000 nautical miles (197,000 mi; 317,000 km) from Earth, it was the first "deep space" EVA in history, performed at great distance from any planetary body. As of , it remains one of only three such EVAs, all performed during Apollo's J missions under similar circumstances. Later that day, the crew set a record for the longest Apollo flight to that point. On approach to Earth on August7, the service module was jettisoned, and the command module reentered the Earth's atmosphere. Although one of the three parachutes on the CM failed after deploying, likely due to damage as the spacecraft vented fuel, only two were required for a safe landing (one extra for redundancy). Upon landing in the North Pacific Ocean, the CM and crew were recovered and taken aboard the recovery ship, , after a mission lasting 12 days, 7hours, 11 minutes and 53 seconds.
Assessment. The mission objectives for Apollo 15 were to "perform selenological inspection, survey, and sampling of materials and surface features in a pre-selected area of the Hadley–Apennine region. Emplace and activate surface experiments. Evaluate the capability of the Apollo equipment to provide extended lunar surface stay time, increased extravehicular operations, and surface mobility. [and] Conduct inflight experiments and photographic tasks from lunar orbit." It achieved all those objectives. The mission also completed a long list of other tasks, including experiments. One of the photographic objectives, to obtain images of the gegenschein from lunar orbit, was not completed, as the camera was not pointed at the proper spot in the sky. According to the conclusions in the "Apollo 15 Mission Report", the journey "was the fourth lunar landing and resulted in the collection of a wealth of scientific information. The Apollo system, in addition to providing a means of transportation, excelled as an operational scientific facility."
Apollo 15 saw an increase in public interest in the Apollo program, in part due to fascination with the LRV, as well as the attractiveness of the Hadley Rille site and the increased television coverage. According to David Woods in the "Apollo Lunar Flight Journal", Controversies. Despite the successful mission, the careers of the crew were tarnished by a deal they had made before the flight to carry postal covers to the Moon in exchange for about $7,000 each, which they planned to set aside for their children. Walter Eiermann, who had many professional and social contacts with NASA employees and the astronaut corps, served as intermediary between the astronauts and a West German stamp dealer, Hermann Sieger, and Scott carried about 400 covers onto the spacecraft; they were subsequently transferred into "Falcon" and remained inside the lander during the astronauts' activities on the surface of the Moon. After the return to Earth, 100 of the covers were given to Eiermann, who passed them on to Sieger, receiving a commission. No permission had been received from Slayton to carry the covers, as required.
The 100 covers were put on sale to Sieger's customers in late 1971 at a price of about $1,500 each. After receiving the agreed payments, the astronauts returned them, and accepted no compensation. In April 1972, Slayton learned that unauthorized covers had been carried, and removed the three as the backup crew for Apollo 17. The matter became public in June 1972 and the three astronauts were reprimanded for poor judgment; none ever flew in space again. During the investigation, the astronauts had surrendered those covers still in their possession; after Worden filed suit, they were returned in 1983, something "Slate" magazine deemed an exoneration. Another controversy arose later, this time surrounding the "Fallen Astronaut" statuette that Scott had left on the Moon. Before the mission, Scott had made a verbal agreement with Belgian artist Paul Van Hoeydonck to sculpt the statuette. Scott's intent, in keeping with NASA's strict policy against commercial exploitation of the US government's space program, was for a simple memorial with a minimum of publicity, keeping the artist anonymous, no commercial replicas being made except for a single copy for public exhibit at the National Air and Space Museum commissioned after the sculpture's public disclosure during the post-flight press conference. Van Hoeydonck claims to have had a different understanding of the agreement, by which he would have received recognition as the creator of a tribute to human space exploration, with rights to sell replicas to the public. Under pressure from NASA, Van Hoeydonck canceled a plan to publicly sell 950 signed copies.
In 2021, Scott published a document entitled "Memorandum for the Record", in which he stated that the figurine left on the Moon was designed and fabricated by NASA personnel. While testifying before a Senate committee in 1972, he had stated that the figurine had been made and provided by Van Hoeydonck at Scott's request. During those congressional hearings into the postal covers and Fallen Astronaut matters, two Bulova timepieces taken on the mission by Scott were also matters of controversy. Before the mission, Scott had been introduced to Bulova's representative, General James McCormack by Apollo 8 commander Frank Borman. Bulova had been seeking to have its timepieces taken on Apollo missions, but after evaluation, NASA had selected Omega watches instead. Scott brought the Bulova timepieces on the mission, without disclosing them to Slayton. During Scott's second EVA, the crystal on his NASA standard issue Omega Speedmaster watch popped off, and, during the third EVA, he used a Bulova watch. The Bulova Chronograph Model #88510/01 that Scott wore on the lunar surface was a prototype, given to him by the Bulova Company, and it is the only privately owned watch to have been worn while walking on the lunar surface. There are images of him wearing this watch, when he saluted the American flag on the Moon, with the Hadley Delta expanse in the background. In 2015, the watch sold for $1.625 million, which makes it one of the most expensive astronaut-owned artifact ever sold at auction and one of the most expensive watches sold at auction.
Mission insignia. The Apollo 15 mission patch carries Air Force motifs, a nod to the crew's service there, just as the Apollo 12 all-Navy crew's patch had featured a sailing ship. The circular patch features stylized red, white and blue birds flying over Hadley Rille. Immediately behind the birds, a line of craters forms the Roman numeral XV. The Roman numerals were hidden in emphasized outlines of some craters after NASA insisted that the mission number be displayed in Arabic numerals. The artwork is circled in red, with a white band giving the mission and crew names and a blue border. Scott contacted fashion designer Emilio Pucci to design the patch, who came up with the basic idea of the three-bird motif on a square patch. The crew changed the shape to round and the colors from blues and greens to a patriotic red, white and blue. Worden stated that each bird also represented an astronaut, white being his own color (and as Command Module Pilot, uppermost), Scott being the blue bird and Irwin the red. The colors matched Chevrolet Corvettes leased by the astronauts at KSC; a Florida car dealer had, since the time of Project Mercury, been leasing Chevrolets to astronauts for $1 and later selling them to the public. The astronauts were photographed with the cars and the training LRV for the June 11, 1971, edition of "Life" magazine.
Visibility from space. The halo area of the Apollo 15 landing site, created by the LM's exhaust plume, was observed by a camera aboard the Japanese lunar orbiter SELENE and confirmed by comparative analysis of photographs in May 2008. This corresponds well to photographs taken from the Apollo 15 command module showing a change in surface reflectivity due to the plume, and was the first visible trace of crewed landings on the Moon seen from space since the close of the Apollo program.
Apollo 16 Apollo 16 (April 1627, 1972) was the tenth crewed mission in the United States Apollo space program, administered by NASA, and the fifth and penultimate to land on the Moon. It was the second of Apollo's "J missions", with an extended stay on the lunar surface, a focus on science, and the use of the Lunar Roving Vehicle (LRV). The landing and exploration were in the Descartes Highlands, a site chosen because some scientists expected it to be an area formed by volcanic action, though this proved not to be the case. The mission was crewed by Commander John Young, Lunar Module Pilot Charles Duke and Command Module Pilot Ken Mattingly. Launched from the Kennedy Space Center in Florida on April 16, 1972, Apollo 16 experienced a number of minor glitches en route to the Moon. These culminated with a problem with the spacecraft's main engine that resulted in a six-hour delay in the Moon landing as NASA managers contemplated having the astronauts abort the mission and return to Earth, before deciding the problem could be overcome. Although they permitted the lunar landing, NASA had the astronauts return from the mission one day earlier than planned.
After flying the Lunar Module to the Moon's surface on April 21, Young and Duke spent 71 hours—just under three days—on the lunar surface, during which they conducted three extravehicular activities or moonwalks, totaling 20 hours and 14 minutes. The pair drove the lunar rover, the second used on the Moon, for . On the surface, Young and Duke collected of lunar samples for return to Earth, including Big Muley, the largest Moon rock collected during the Apollo missions. During this time Mattingly orbited the Moon in the command and service module (CSM), taking photos and operating scientific instruments. Mattingly, in the command module, spent 126 hours and 64 revolutions in lunar orbit. After Young and Duke rejoined Mattingly in lunar orbit, the crew released a subsatellite from the service module (SM). During the return trip to Earth, Mattingly performed a one-hour spacewalk to retrieve several film cassettes from the exterior of the service module. Apollo 16 returned safely to Earth on April 27, 1972. Crew and key Mission Control personnel.
John Young, the mission commander, was 41 years old and a captain in the Navy at the time of Apollo 16. Becoming an astronaut in 1962 as part of the second group to be selected by NASA, he flew in Gemini 3 with Gus Grissom in 1965, becoming the first American not of the Mercury Seven to fly in space. He thereafter flew in Gemini 10 (1966) with Michael Collins and as command module pilot of Apollo 10 (1969). With Apollo 16, he became the second American, after Jim Lovell, to fly in space four times. Thomas Kenneth "Ken" Mattingly, the command module pilot, was 36 years old and a lieutenant commander in the Navy at the time of Apollo 16. Mattingly had been selected in NASA's fifth group of astronauts in 1966. He was a member of the support crew for Apollo 8 and Apollo 9. Mattingly then undertook parallel training with Apollo 11's backup CMP, William Anders, who had announced his resignation from NASA effective at the end of July 1969 and would thus be unavailable if the first lunar landing mission was postponed. Had Anders left NASA before Apollo 11 flew, Mattingly would have taken his place on the backup crew.
Mattingly had originally been assigned to the prime crew of Apollo 13, but was exposed to rubella through Charles Duke, at that time with Young on Apollo 13's backup crew; Duke had caught it from one of his children. Mattingly never contracted the illness, but three days before launch was removed from the crew and replaced by his backup, Jack Swigert. Duke, also a Group 5 astronaut and a space rookie, had served on the support crew of Apollo 10 and was a capsule communicator (CAPCOM) for Apollo 11. A lieutenant colonel in the Air Force, Duke was 36 years old at the time of Apollo 16, which made him the youngest of the twelve astronauts who walked on the Moon during Apollo as of the time of the mission. All three men were announced as the prime crew of Apollo 16 on March 3, 1971. Apollo 16's backup crew consisted of Fred W. Haise Jr. (commander, who had flown on Apollo 13), Stuart A. Roosa (CMP, who had flown on Apollo 14) and Edgar D. Mitchell (LMP, also Apollo 14). Although not officially announced, Director of Flight Crew Operations Deke Slayton, the astronauts' supervisor, had originally planned to have a backup crew of Haise as commander, William R. Pogue (CMP) and Gerald P. Carr (LMP), who were targeted for the prime crew assignment on Apollo 19. However, after the cancellations of Apollos 18 and 19 were announced in September 1970, it made more sense to use astronauts who had already flown lunar missions as backups, rather than training others on what would likely be a dead-end assignment. Subsequently, Roosa and Mitchell were assigned to the backup crew, while Pogue and Carr were reassigned to the Skylab program where they flew on Skylab 4.
For projects Mercury and Gemini, a prime and a backup crew had been designated, but for Apollo, a third group of astronauts, known as the support crew, was also designated. Slayton created the support crews early in the Apollo Program on the advice of Apollo crew commander James McDivitt, who would lead Apollo 9. McDivitt believed that, with preparation going on in facilities across the U.S., meetings that needed a member of the flight crew would be missed. Support crew members were to assist as directed by the mission commander. Usually low in seniority, they assembled the mission's rules, flight plan, and checklists, and kept them updated. For Apollo 16, they were: Anthony W. England, Karl G. Henize, Henry W. Hartsfield Jr., Robert F. Overmyer and Donald H. Peterson. Flight directors were Pete Frank and Philip Shaffer, first shift, Gene Kranz and Donald R. Puddy, second shift, and Gerry Griffin, Neil B. Hutchinson and Charles R. Lewis, third shift. Flight directors during Apollo had a one-sentence job description: "The flight director may take any actions necessary for crew safety and mission success." CAPCOMs were Haise, Roosa, Mitchell, James B. Irwin, England, Peterson, Hartsfield, and C. Gordon Fullerton.
Mission insignia and call signs. The insignia of Apollo 16 is dominated by a rendering of an American eagle and a red, white and blue shield, representing the people of the United States, over a gray background representing the lunar surface. Overlaying the shield is a gold NASA vector, orbiting the Moon. On its gold-outlined blue border, there are 16 stars, representing the mission number, and the names of the crew members: Young, Mattingly, Duke. The insignia was designed from ideas originally submitted by the crew of the mission, by Barbara Matelski of the graphics shop at the Manned Spacecraft Center in Houston. Young and Duke chose "Orion" for the Lunar Module's call sign, while Mattingly chose "Casper" for the command and service module. According to Duke, he and Young chose "Orion" for the LM because they wanted something connected with the stars. Orion is one of the brightest constellations as seen from Earth, and one visible to the astronauts throughout their journey. Duke also stated, "it is a prominent constellation and easy to pronounce and transmit to Mission Control". Mattingly said he chose "Casper", evoking Casper the Friendly Ghost, because "there are enough serious things in this flight, so I picked a non-serious name."
Planning and training. Landing site selection. Apollo 16 was the second of Apollo's J missions, featuring the use of the Lunar Roving Vehicle, increased scientific capability, and three-day lunar surface stays. As Apollo 16 was the penultimate mission in the Apollo program and there was no major new hardware or procedures to test on the lunar surface, the last two missions (the other being Apollo 17) presented opportunities for astronauts to clear up some of the uncertainties in understanding the Moon's characteristics. Scientists sought information on the Moon's early history, which might be obtained from its ancient surface features, the lunar highlands. Previous Apollo expeditions, including Apollo 14 and Apollo 15, had obtained samples of pre-mare lunar material, likely thrown from the highlands by meteorite impacts. These were dated from before lava began to upwell from the Moon's interior and flood the low areas and basins. Nevertheless, no Apollo mission had actually visited the lunar highlands.
The Ad Hoc Apollo Site Evaluation Committee met in April and May 1971 to decide the Apollo 16 and 17 landing sites; it was chaired by Noel Hinners of Bellcomm. There was consensus the final landing sites should be in the lunar highlands, and among the sites considered for Apollo 16 were the Descartes Highlands region west of Mare Nectaris and the crater Alphonsus. The considerable distance between the Descartes site and previous Apollo landing sites would also be beneficial for the network of seismometers, deployed on each landing mission beginning with Apollo 12. At Alphonsus, three scientific objectives were determined to be of primary interest and paramount importance: the possibility of old, pre-Imbrium impact material from within the crater's wall, the composition of the crater's interior and the possibility of past volcanic activity on the floor of the crater at several smaller "dark halo" craters. Geologists feared, however, that samples obtained from the crater might have been contaminated by the Imbrium impact, thus preventing Apollo 16 from obtaining samples of pre-Imbrium material. There also remained the distinct possibility that this objective would have already been satisfied by the Apollo 14 and Apollo 15 missions, as the Apollo 14 samples had not yet been completely analyzed and samples from Apollo 15 had not yet been obtained.
On June 3, 1971, the site selection committee decided to target the Apollo 16 mission for the Descartes site. Following the decision, the Alphonsus site was considered the most likely candidate for Apollo 17, but was eventually rejected. With the assistance of orbital photography obtained on the Apollo 14 mission, the Descartes site was determined to be safe enough for a crewed landing. The specific landing site was between two young impact craters, North Ray and South Ray craters – in diameter, respectively – which provided "natural drill holes" which penetrated through the lunar regolith at the site, thus leaving exposed bedrock that could be sampled by the crew. After the selection, mission planners made the Descartes and Cayley formations, two geologic units of the lunar highlands, the primary sampling interest of the mission. It was these formations that the scientific community widely suspected were formed by lunar volcanism, but this hypothesis was proven incorrect by the composition of lunar samples from the mission.
Training. In addition to the usual Apollo spacecraft training, Young and Duke, along with backup commander Fred Haise, underwent an extensive geological training program that included several field trips to introduce them to concepts and techniques they would use in analyzing features and collecting samples on the lunar surface. During these trips, they visited and provided scientific descriptions of geologic features they were likely to encounter. The backup LMP, Mitchell, was unavailable during the early part of the training, occupied with tasks relating to Apollo 14, but by September 1971 had joined the geology field trips. Before that, Tony England (a member of the support crew and the lunar EVA CAPCOM) or one of the geologist trainers would train alongside Haise on geology field trips.
In addition to the field geology training, Young and Duke also trained to use their EVA space suits, adapt to the reduced lunar gravity, collect samples, and drive the Lunar Roving Vehicle. The fact that they had been backups for Apollo 13, planned to be a landing mission, meant that they could spend about 40 percent of their time training for their surface operations. They also received survival training and prepared for technical aspects of the mission. The astronauts spent much time studying the lunar samples brought back by earlier missions, learning about the instruments to be carried on the mission, and hearing what the principal investigators in charge of those instruments expected to learn from Apollo 16. This training helped Young and Duke, while on the Moon, quickly realize that the expected volcanic rocks were not there, even though the geologists in Mission Control initially did not believe them. Much of the training—according to Young, 350 hours—was conducted with the crew wearing space suits, something that Young deemed vital, allowing the astronauts to know the limitations of the equipment in doing their assigned tasks. Mattingly also received training in recognizing geological features from orbit by flying over the field areas in an airplane, and trained to operate the Scientific Instrument Module from lunar orbit.
Equipment. Launch vehicle. The launch vehicle which took Apollo 16 to the Moon was a Saturn V, designated as AS-511. This was the eleventh Saturn V to be flown and the ninth used on crewed missions. Apollo 16's Saturn V was almost identical to Apollo 15's. One change that was made was the restoration of four retrorockets to the S-IC first stage, meaning there would be a total of eight, as on Apollo 14 and earlier. The retrorockets were used to minimize the risk of collision between the jettisoned first stage and the Saturn V. These four retrorockets had been omitted from Apollo 15's Saturn V to save weight, but analysis of Apollo 15's flight showed that the S-IC came closer than expected after jettison, and it was feared that if there were only four rockets and one failed, there might be a collision. ALSEP and other surface equipment. As on all lunar landing missions after Apollo 11, an Apollo Lunar Surface Experiments Package (ALSEP) was flown on Apollo 16. This was a suite of nuclear-powered experiments designed to keep functioning after the astronauts who set them up returned to Earth. Apollo 16's ALSEP consisted of a Passive Seismic Experiment (PSE, a seismometer), an Active Seismic Experiment (ASE), a Lunar Heat Flow Experiment (HFE), and a Lunar Surface Magnetometer (LSM). The ALSEP was powered by a SNAP-27 radioisotope thermoelectric generator, developed by the Atomic Energy Commission.
The PSE added to the network of seismometers left by Apollo 12, 14 and 15. NASA intended to calibrate the Apollo 16 PSE by crashing the LM's ascent stage near it after the astronauts were done with it, an object of known mass and velocity impacting at a known location. However, NASA lost control of the ascent stage after jettison, and this did not occur. The ASE, designed to return data about the Moon's geologic structure, consisted of two groups of explosives: one, a line of "thumpers" were to be deployed attached to three geophones. The thumpers would be exploded during the ALSEP deployment. A second group was four mortars of different sizes, to be set off remotely once the astronauts had returned to Earth. Apollo 14 had also carried an ASE, though its mortars were never set off for fear of affecting other experiments. The HFE involved the drilling of two holes into the lunar surface and emplacement of thermometers which would measure how much heat was flowing from the lunar interior. This was the third attempt to emplace a HFE: the first flew on Apollo 13 and never reached the lunar surface, while on Apollo 15, problems with the drill meant the probes did not go as deep as planned. The Apollo 16 attempt would fail after Duke had successfully emplaced the first probe; Young, unable to see his feet in the bulky spacesuit, pulled out and severed the cable after it wrapped around his leg. NASA managers vetoed a repair attempt due to the amount of time it would take. A HFE flew, and was deployed, on Apollo 17.
The LSM was designed to measure the strength of the Moon's magnetic field, which is only a small fraction of Earth's. Additional data would be returned by the use of the Lunar Portable Magnetometer (LPM), to be carried on the lunar rover and activated at several geology stops. Scientists also hoped to learn from an Apollo 12 sample, to be briefly returned to the Moon on Apollo 16, from which "soft" magnetism had been removed, to see if it had been restored on its journey. Measurements after the mission found that "soft" magnetism had returned to the sample, although at a lower intensity than before. A Far Ultraviolet Camera/Spectrograph (UVC) was flown, the first astronomical observations taken from the Moon, seeking data on hydrogen sources in space without the masking effect of the Earth's corona. The instrument was placed in the LM's shadow and pointed at nebulae, other astronomical objects, the Earth itself, and any suspected volcanic vents seen on the lunar surface. The film was returned to Earth. When asked to summarize the results for a general audience, Dr. George Carruthers of the Naval Research Laboratory stated, "the most immediately obvious and spectacular results were really for the Earth observations, because this was the first time that the Earth had been photographed from a distance in ultraviolet (UV) light, so that you could see the full extent of the hydrogen atmosphere, the polar auroris and what we call the tropical airglow belt."
Four panels mounted on the LM's descent stage comprised the Cosmic Ray Detector, designed to record cosmic ray and solar wind particles. Three of the panels were left uncovered during the voyage to the Moon, with the fourth uncovered by the crew early in the EVA. The panels would be bagged for return to Earth. The free-standing Solar Wind Composition Experiment flew on Apollo 16, as it had on each of the lunar landings, for deployment on the lunar surface and return to Earth. Platinum foil was added to the aluminum of the previous experiments, to minimize contamination. Particles and Fields Subsatellite PFS-2. The Apollo 16 Particles and Fields Subsatellite (PFS-2) was a small satellite released into lunar orbit from the service module. Its principal objective was to measure charged particles and magnetic fields all around the Moon as the Moon orbited Earth, similar to its sister spacecraft, PFS-1, released eight months earlier by Apollo 15. The two probes were intended to have similar orbits, ranging from above the lunar surface.
Like the Apollo 15 subsatellite, PFS-2 was expected to have a lifetime of at least a year before its orbit decayed and it crashed onto the lunar surface. The decision to bring Apollo 16 home early after there were difficulties with the main engine meant that the spacecraft did not go to the orbit which had been planned for PFS-2. Instead, it was ejected into a lower-than-planned orbit and crashed into the Moon a month later on May 29, 1972, after circling the Moon 424 times. This brief lifetime was because lunar mascons were near to its orbital ground track and helped pull PFS-2 into the Moon. Mission events. Elements of the spacecraft and launch vehicle began arriving at Kennedy Space Center in July 1970, and all had arrived by September 1971. Apollo 16 was originally scheduled to launch on March 17, 1972. One of the bladders for the CM's reaction control system burst during testing. This issue, in combination with concerns that one of the explosive cords that would jettison the LM from the CSM after the astronauts returned from the lunar surface would not work properly, and a problem with Duke's spacesuit, made it desirable to slip the launch to the next launch window. Thus, Apollo 16 was postponed to April 16. The launch vehicle stack, which had been rolled out from the Vehicle Assembly Building on December 13, 1971, was returned thereto on January 27, 1972. It was rolled out again to Launch Complex 39A on February 9.
The official mission countdown began on Monday, April 10, 1972, at 8:30 am, six days before the launch. At this point the SaturnV rocket's three stages were powered up, and drinking water was pumped into the spacecraft. As the countdown began, the crew of Apollo 16 was participating in final training exercises in anticipation of a launch on April 16. The astronauts underwent their final preflight physical examination on April 11. The only holds in the countdown were the ones pre-planned in the schedule, and the weather was fair as the time for launch approached. Launch and outward journey. The Apollo 16 mission launched from the Kennedy Space Center in Florida at 12:54 pm EST on April 16, 1972. The launch was nominal; the crew experienced vibration similar to that on previous missions. The first and second stages of the SaturnV (the S-IC and S-II) performed nominally; the spacecraft entered orbit around Earth just under 12 minutes after lift-off. After reaching orbit, the crew spent time adapting to the zero-gravity environment and preparing the spacecraft for trans-lunar injection (TLI), the burn of the third-stage rocket that would propel them to the Moon. In Earth orbit, the crew faced minor technical issues, including a potential problem with the environmental control system and the S-IVB third stage's attitude control system, but eventually resolved or compensated for them as they prepared to depart towards the Moon.
After two orbits, the rocket's third stage reignited for just over five minutes, propelling the craft towards the Moon at about . Six minutes after the burn of the S-IVB, the command and service modules (CSM), containing the crew, separated from the rocket and traveled away from it before turning around and retrieving the lunar module from inside the expended rocket stage. The maneuver, performed by Mattingly and known as transposition, docking, and extraction, went smoothly. Following transposition and docking, the crew noticed the exterior surface of the Lunar Module was giving off particles from a spot where the LM's skin appeared torn or shredded; at one point, Duke estimated they were seeing about five to ten particles per second. Young and Duke entered the Lunar Module through the docking tunnel connecting it with the command module to inspect its systems, at which time they did not spot any major issues. Once on course towards the Moon, the crew put the spacecraft into a rotisserie "barbecue" mode in which the craft rotated along its long axis three times per hour to ensure even heat distribution about the spacecraft from the Sun. After further preparing the craft for the voyage, the crew began the first sleep period of the mission just under 15 hours after launch.
By the time Mission Control issued the wake-up call to the crew for flight day two, the spacecraft was about away from the Earth, traveling at about . As it was not due to arrive in lunar orbit until flight day four, flight days two and three were largely preparatory, consisting of spacecraft maintenance and scientific research. On day two, the crew performed an electrophoresis experiment, also performed on Apollo 14, in which they attempted to demonstrate that electrophoretic separation in their near-weightless environment could be used to produce substances of greater purity than would be possible on Earth. Using two different sizes of polystyrene particles, one size colored red and one blue, separation of the two types via electrophoresis was achieved, though electro-osmosis in the experiment equipment prevented the clear separation of two particle bands. The remainder of day two included a two-second mid-course correction burn performed by the CSM's service propulsion system (SPS) engine to tweak the spacecraft's trajectory. Later in the day, the astronauts entered the Lunar Module for the second time to further inspect the landing craft's systems. The crew reported they had observed additional paint peeling from a portion of the LM's outer aluminum skin. Despite this, the crew discovered that the spacecraft's systems were performing nominally. Following the LM inspection, the crew reviewed checklists and procedures for the following days in anticipation of their arrival and the Lunar Orbit Insertion (LOI) burn. Command Module Pilot Mattingly reported "gimbal lock", meaning that the system to keep track of the craft's attitude was no longer accurate. Mattingly had to realign the guidance system using the Sun and Moon. At the end of day two, Apollo 16 was about away from Earth.
When the astronauts were awakened for flight day three, the spacecraft was about away from the Earth. The velocity of the craft steadily decreased, as it had not yet reached the lunar sphere of gravitational influence. The early part of day three was largely housekeeping, spacecraft maintenance and exchanging status reports with Mission Control in Houston. The crew performed the Apollo light flash experiment, or ALFMED, to investigate "light flashes" that were seen by Apollo lunar astronauts when the spacecraft was dark, regardless of whether their eyes were open. This was thought to be caused by the penetration of the eye by cosmic ray particles. During the second half of the day, Young and Duke again entered the Lunar Module to power it up and check its systems, and perform housekeeping tasks in preparation for the lunar landing. The systems were found to be functioning as expected. Following this, the crew donned their space suits and rehearsed procedures that would be used on landing day. Just before the end of flight day three at 59 hours, 19 minutes, 45 seconds after liftoff, while from the Earth and from the Moon, the spacecraft's velocity began increasing as it accelerated towards the Moon after entering the lunar sphere of influence.
After waking up on flight day four, the crew began preparations for the LOI maneuver that would brake them into orbit. At an altitude of the scientific instrument module (SIM) bay cover was jettisoned. At just over 74 hours into the mission, the spacecraft passed behind the Moon, temporarily losing contact with Mission Control. While over the far side, the SPS burned for 6minutes and 15 seconds, braking the spacecraft into an orbit with a low point (pericynthion) of 58.3 and a high point (apocynthion) of 170.4 nautical miles (108.0 and 315.6 km, respectively). After entering lunar orbit, the crew began preparations for the Descent Orbit Insertion (DOI) maneuver to further modify the spacecraft's orbital trajectory. The maneuver decreased the craft's pericynthion to . The remainder of flight day four was spent making observations and preparing for activation of the Lunar Module, undocking, and landing the following day. Lunar surface. The crew continued preparing for Lunar Module activation and undocking shortly after waking up to begin flight day five. The boom that extended the mass spectrometer in the SIM bay was stuck, semi-deployed. It was decided that Young and Duke would visually inspect the boom after undocking the LM from the CSM. They entered the LM for activation and checkout of the spacecraft's systems. Despite entering the LM 40 minutes ahead of schedule, they completed preparations only 10 minutes early due to numerous delays in the process. With the preparations finished, they undocked 96 hours, 13 minutes, 31 seconds into the mission.
For the rest of the two crafts' passes over the near side of the Moon, Mattingly prepared to shift "Casper" to a higher, near-circular orbit, while Young and Duke prepared "Orion" for the descent to the lunar surface. At this point, during tests of the CSM's steerable rocket engine in preparation for the burn to modify the craft's orbit, Mattingly detected oscillations in the SPS engine's backup gimbal system. According to mission rules, under such circumstances, "Orion" was to re-dock with "Casper", in case Mission Control decided to abort the landing and use the Lunar Module's engines for the return trip to Earth. Instead, the two craft kept station, maintaining positions close to each other. After several hours of analysis, mission controllers determined that the malfunction could be worked around, and Young and Duke could proceed with the landing. Powered descent to the lunar surface began about six hours behind schedule. Because of the delay, Young and Duke began their descent to the surface at an altitude higher than that of any previous mission, at . After descending to an altitude of about , Young was able to view the landing site in its entirety. Throttle-down of the LM's landing engine occurred on time, and the spacecraft tilted forward to its landing orientation at an altitude of . The LM landed north and west of the planned landing site at 104 hours, 29 minutes, and 35 seconds into the mission, at 2:23:35 UTC on April 21 (8:23:35 pm on April 20 in Houston). The availability of the Lunar Roving Vehicle rendered their distance from the targeted point trivial.
After landing, Young and Duke began powering down some of the LM's systems to conserve battery power. Upon completing their initial procedures, the pair configured "Orion" for their three-day stay on the lunar surface, removed their space suits and took initial geological observations of the immediate landing site. They then settled down for their first meal on the surface. After eating, they configured the cabin for sleep. The landing delay caused by the malfunction in the CSM's main engine necessitated significant modifications to the mission schedule. Apollo 16 would spend one less day in lunar orbit after surface exploration had been completed to afford the crew ample margins in the event of further problems. In order to improve Young's and Duke's sleep schedule, the third and final moonwalk of the mission was trimmed from seven hours to five. First moonwalk.
The day's next task was to deploy the ALSEP; while they were parking the lunar rover, on which the TV camera was mounted, to observe the deployment, the rear steering began functioning. After ALSEP deployment, they collected samples in the vicinity. About four hours after the beginning of EVA-1, they mounted the lunar rover and drove to the first geologic stop, Plum Crater, a crater on the rim of Flag Crater, about across. There, at a distance of from the LM, they sampled material in the vicinity, which scientists believed had penetrated through the upper regolith layer to the underlying Cayley Formation. It was there that Duke retrieved, at the request of Mission Control, the largest rock returned by an Apollo mission, a breccia nicknamed Big Muley after mission geology principal investigator William R. Muehlberger. The next stop of the day was Buster Crater, a small crater located north of the larger Spook Crater, about from the LM. There, Duke took pictures of Stone Mountain and South Ray Crater, while Young deployed the LPM. By this point, scientists were beginning to reconsider their pre-mission hypothesis that Descartes had been the setting of ancient volcanic activity, as the two astronauts had yet to find any volcanic material. Following their stop at Buster, Young did a "Grand Prix" demonstration drive of the lunar rover, which Duke filmed with a 16 mm movie camera. This had been attempted on Apollo 15, but the camera had malfunctioned. After completing more tasks at the ALSEP, they returned to the LM to close out the moonwalk. They reentered the LM 7hours, 6minutes, and 56 seconds after the start of the EVA. Once inside, they pressurized the LM cabin, went through a half-hour debriefing with scientists in Mission Control, and configured the cabin for the sleep period.
Second moonwalk. Waking up three and a half minutes earlier than planned, they discussed the day's timeline of events with Houston. The second lunar excursion's primary objective was to visit Stone Mountain to climb up the slope of about 20 degrees to reach a cluster of five craters known as "Cinco craters". They drove there in the LRV, traveling from the LM. At above the valley floor, the pair were at the highest elevation above the LM of any Apollo mission. They marveled at the view (including South Ray) from the side of Stone Mountain, which Duke described as "spectacular", then gathered samples in the vicinity. After spending 54 minutes on the slope, they climbed aboard the lunar rover en route to the day's second stop, dubbed Station 5, a crater across. There, they hoped to find Descartes material that had not been contaminated by ejecta from South Ray Crater, a large crater south of the landing site. The samples they collected there, despite still uncertain origin, are according to geologist Wilhelms, "a reasonable bet to be Descartes".
The next stop, Station 6, was a blocky crater, where the astronauts believed they could sample the Cayley Formation as evidenced by the firmer soil found there. Bypassing station seven to save time, they arrived at Station 8 on the lower flank of Stone Mountain, where they sampled material on a ray from South Ray crater for about an hour. There, they collected black and white breccias and smaller, crystalline rocks rich in plagioclase. At Station 9, an area known as the "Vacant Lot", which was believed to be free of ejecta from South Ray, they spent about 40 minutes gathering samples. Twenty-five minutes after departing the Vacant Lot, they arrived at the final stop of the day, halfway between the ALSEP site and the LM. There, they dug a double core and conducted several penetrometer tests along a line stretching east of the ALSEP. At the request of Young and Duke, the moonwalk was extended by ten minutes. After returning to the LM to wrap up the second lunar excursion, they climbed back inside the landing craft's cabin, sealing and pressurizing the interior after 7hours, 23 minutes, and 26 seconds of EVA time, breaking a record that had been set on Apollo 15. After eating a meal and proceeding with a debriefing on the day's activities with Mission Control, they reconfigured the LM cabin and prepared for the sleep period.
Third moonwalk. Flight day seven was their third and final day on the lunar surface, returning to orbit to rejoin Mattingly in the CSM following the day's moonwalk. During the third and final lunar excursion, they were to explore North Ray crater, the largest of any of the craters any Apollo expedition had visited. After exiting "Orion", the pair drove to North Ray crater. The drive was smoother than that of the previous day, as the craters were shallower and boulders were less abundant north of the immediate landing site. After passing Palmetto crater, boulders gradually became larger and more abundant as they approached North Ray in the lunar rover. Upon arriving at the rim of North Ray crater, they were away from the LM. After their arrival, the duo took photographs of the wide and deep crater. They visited a large boulder, taller than a four-story building, which became known as 'House Rock'. Samples obtained from this boulder delivered the final blow to the pre-mission volcanic hypothesis, proving it incorrect. House Rock had numerous bullet hole-like marks where micrometeoroids from space had impacted the rock.
About 1hour and 22 minutes after arriving at the North Ray crater, they departed for Station 13, a large boulder field about from North Ray. On the way, they set a lunar speed record, traveling at an estimated downhill. They arrived at a high boulder, which they called "Shadow Rock". Here, they sampled permanently shadowed soil. During this time, Mattingly was preparing the CSM in anticipation of their return approximately six hours later. After three hours and six minutes, they returned to the LM, where they completed several experiments and unloaded the rover. A short distance from the LM, Duke placed a photograph of his family and an Air Force commemorative medallion on the surface. Young drove the rover to a point about east of the LM, known as the 'VIP site,' so its television camera, controlled remotely by Mission Control, could observe Apollo 16's liftoff from the Moon. They then reentered the LM after a 5-hour and 40-minute final excursion. After pressurizing the LM cabin, the crew began preparing to return to lunar orbit.
Solo activities. After "Orion" was cleared for the landing attempt, "Casper" maneuvered away, and Mattingly performed a burn that took his spacecraft to an orbit of in preparation for his scientific work. The SM carried a suite of scientific instruments in its SIM bay, similar to those carried on Apollo 15. Mattingly had compiled a busy schedule operating the various SIM bay instruments, one that became even busier once Houston decided to bring Apollo 16 home a day early, as the flight directors sought to make up for lost time. His work was hampered by various malfunctions: when the Panoramic Camera was turned on, it appeared to take so much power from one of the CSM's electrical systems, that it initiated the spacecraft Master Alarm. It was immediately shut off, though later analysis indicated that the drain might have been from the spacecraft's heaters, which came on at the same time. Its work was also hampered by the delay in the beginning of "Casper"s orbital scientific work and the early return to Earth, and by a malfunction resulting in the overexposure of many of the photographs.
Its work was also hampered by the delay in the beginning of "Casper"s orbital scientific work and the early return to Earth, and by a malfunction resulting in the overexposure of many of the photographs. Nevertheless, it was able to take a photograph of the Descartes area in which "Orion" is visible. The Mass Spectrometer boom did not fully retract following its initial extension, as had happened on Apollo 15, though it retracted far enough to allow the SPS engine to be fired safely when "Casper" maneuvered away from "Orion" before the LM began its Moon landing attempt. Although the Mass Spectrometer was able to operate effectively, it stuck near its fully deployed position prior to the burn that preceded rendezvous, and had to be jettisoned. Scientists had hoped to supplement the lunar data gained with more on the trans-Earth coast, but Apollo 15 data could be used instead. The Mapping Camera also did not function perfectly; later analysis found it to have problems with its glare shield. The changes to the flight plan meant that some areas of the lunar surface that were supposed to be photographed could not be; also, a number of images were overexposed. The changes to the flight plan meant that some areas of the lunar surface that were supposed to be photographed could not be; also, a number of images were overexposed. The Laser Altimeter, designed to accurately measure the spacecraft altitude, slowly lost accuracy due to reduced power, and finally failed just before it was due to be used for the last time.
Return to Earth. Eight minutes before the planned departure from the lunar surface, CAPCOM James Irwin notified Young and Duke from Mission Control that they were go for liftoff. Two minutes before launch, they activated the "Master Arm" switch and then the "Abort Stage" button, causing small explosive charges to sever the ascent stage from the descent stage, with cables connecting the two severed by a guillotine-like mechanism. At the pre-programmed moment, there was liftoff and the ascent stage blasted away from the Moon, as the camera aboard the LRV followed the first moments of the flight. Six minutes after liftoff, at a speed of about , Young and Duke reached lunar orbit. Young and Duke rendezvoused and re-docked with Mattingly in the CSM. To minimize the transfer of lunar dust from the LM cabin into the CSM, Young and Duke cleaned the cabin before opening the hatch separating the two spacecraft. After opening the hatch and reuniting with Mattingly, the crew transferred the samples Young and Duke had collected on the surface into the CSM for transfer to Earth. After transfers were completed, the crew would sleep before jettisoning the empty Lunar Module ascent stage the next day, when it was to be crashed intentionally into the lunar surface in order to calibrate the seismometer Young and Duke had left on the surface.
The next day, after final checks were completed, the expended LM ascent stage was jettisoned. Likely because of a failure by the crew to activate a certain switch in the LM before sealing it off, it tumbled after separation. NASA could not control it, and it did not execute the rocket burn necessary for the craft's intentional de-orbit. The ascent stage eventually crashed into the lunar surface nearly a year after the mission. The crew's next task, after jettisoning the Lunar Module ascent stage, was to release a subsatellite into lunar orbit from the CSM's scientific instrument bay. The burn to alter the CSM's orbit to that desired for the subsatellite had been cancelled; as a result, the subsatellite lasted just over a month in orbit, far less than its anticipated one year. Just under five hours after the subsatellite release, on the CSM's 65th orbit around the Moon, its service propulsion system main engine was reignited to propel the craft on a trajectory that would return it to Earth. The SPS engine performed the burn flawlessly despite the malfunction that had delayed their landing several days previously.
During the return to Earth, Mattingly performed an 83-minute EVA to retrieve film cassettes from the cameras in the SIM bay, with assistance from Duke who remained at the command module's hatch. At approximately from Earth, it was the second "deep space" EVA in history, performed at great distance from any planetary body. , it remains one of only three such EVAs, all performed during Apollo's J-missions under similar circumstances. During the EVA, Mattingly set up a biological experiment, the Microbial Ecology Evaluation Device (MEED), an experiment unique to Apollo 16, to evaluate the response of microbes to the space environment. The crew carried out various housekeeping and maintenance tasks aboard the spacecraft and ate a meal before concluding the day. The penultimate day of the flight was largely spent performing experiments, aside from a twenty-minute press conference during the second half of the day. During the press conference, the astronauts answered questions pertaining to several technical and non-technical aspects of the mission prepared and listed by priority at the Manned Spacecraft Center in Houston by journalists covering the flight. In addition to numerous housekeeping tasks, the astronauts prepared the spacecraft for its atmospheric reentry the next day. At the end of the crew's final full day in space, the spacecraft was approximately from Earth and closing at a rate of about .
When the wake-up call was issued to the crew for their final day in space by CAPCOM England, the CSM was about from Earth, traveling just over . Just over three hours before splashdown in the Pacific Ocean, the crew performed a final course correction burn, using the spacecraft's thrusters to change their velocity by . Approximately ten minutes before reentry into Earth's atmosphere, the cone-shaped command module containing the three crewmembers separated from the service module, which would burn up during reentry. At 265 hours and 37 minutes into the mission, at a velocity of about , Apollo 16 began atmospheric reentry. At its maximum, the temperature of the heat shield was between . After parachute deployment and less than 14 minutes after reentry began, the command module splashed down in the Pacific Ocean southeast of the island of Kiritimati 265 hours, 51 minutes, 5seconds after liftoff. The spacecraft and its crew was retrieved by the aircraft carrier . The astronauts were safely aboard the "Ticonderoga" 37 minutes after splashdown.
Scientific results and aftermath. Scientific analysis of the rocks brought back to Earth confirmed that the Cayley Formation was not volcanic in nature. There was less certainty regarding the Descartes Formation, as it was not clear which if any of the rocks came from there. There was no evidence that showed that Stone Mountain was volcanic. One reason why Descartes had been selected was that it was visually different from previous Apollo landing sites, but rocks from there proved to be closely related to those from the Fra Mauro Formation, Apollo 14's landing site. Geologists realized that they had been so certain that Cayley was volcanic, they had not been open to dissenting views, and that they had been over-reliant on analogues from Earth, a flawed model because the Moon does not share much of the Earth's geologic history. They concluded that there are few if any volcanic mountains on the Moon. These conclusions were informed by observations from Mattingly, the first CMP to use binoculars in his observations, who had seen that from the perspective of lunar orbit, there was nothing distinctive about the Descartes Formation—it fit right in with the Mare Imbrium structure. Other results gained from Apollo 16 included the discovery of two new auroral belts around Earth.
After the mission, Young and Duke served as backups for Apollo 17, and Duke retired from NASA in December 1975. Young and Mattingly both flew the Space Shuttle: Young, who served as Chief Astronaut from 1974 to 1987, commanded the first Space Shuttle mission, STS-1 in 1981, as well as STS-9 in 1983, on the latter mission becoming the first person to journey into space six times. He retired from NASA in 2004. Mattingly also twice commanded Shuttle missions, STS-4 (1982) and STS-51-C (1985), before retiring from NASA in 1985. Locations of spacecraft and other equipment. The "Ticonderoga" delivered the Apollo 16 command module to the North Island Naval Air Station, near San Diego, California, on Friday, May 5, 1972. On Monday, May 8, ground service equipment being used to empty the residual toxic reaction control system fuel in the command module tanks exploded in a Naval Air Station hangar. Forty-six people were sent to the hospital for 24 to 48 hours' observation, most suffering from inhalation of toxic fumes. Most seriously injured was a technician who suffered a fractured kneecap when a cart overturned on him. A hole was blown in the hangar roof 250 feet above; about 40 windows in the hangar were shattered. The command module suffered a three-inch gash in one panel.
The Apollo 16 command module "Casper" is on display at the U.S. Space & Rocket Center in Huntsville, Alabama, following a transfer of ownership from NASA to the Smithsonian in November 1973. The Lunar Module ascent stage separated from the CSM on April 24, 1972, but NASA lost control of it. It orbited the Moon for about a year. Its impact site remains unknown, though research published in 2023 suggests an impact date of May 29, 1972 (the same as for the subsattelite) and an impact location of 9.99° N, 104.26° E. The S-IVB was deliberately crashed into the Moon. However, due to a communication failure before impact the exact location was unknown until January 2016, when it was discovered within Mare Insularum by the Lunar Reconnaissance Orbiter, approximately southwest of Copernicus Crater. Duke left two items on the Moon, both of which he photographed while there. One is a plastic-encased photo portrait of his family. The reverse of the photo is signed by Duke's family and bears this message: "This is the family of Astronaut Duke from Planet Earth. Landed on the Moon, April 1972." The other item was a commemorative medal issued by the United States Air Force, which was celebrating its 25th anniversary in 1972. He took two medals, leaving one on the Moon and donating the other to the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Ohio.
In 2006, shortly after Hurricane Ernesto affected Bath, North Carolina, eleven-year-old Kevin Schanze discovered a piece of metal debris on the ground near his beach home. Schanze and a friend discovered a "stamp" on the flat metal sheet, which upon further inspection turned out to be a faded copy of the Apollo 16 mission insignia. NASA later confirmed the object to be a piece of the first stage of the SaturnV that had launched Apollo 16 into space. In July 2011, after returning the piece of debris at NASA's request, 16-year-old Schanze was given an all-access tour of the Kennedy Space Center and VIP seating for the launch of STS-135, the final mission of the Space Shuttle program.
Apollo 17 Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, while Command Module Pilot Ronald Evans orbited above. Schmitt was the only professional geologist to land on the Moon; he was selected in place of Joe Engle, as NASA had been under pressure to send a scientist to the Moon. The mission's heavy emphasis on science meant the inclusion of a number of new experiments, including a biological experiment containing five mice that was carried in the command module. Mission planners had two primary goals in deciding on the landing site: to sample lunar highland material older than that at Mare Imbrium and to investigate the possibility of relatively recent volcanic activity. They therefore selected Taurus–Littrow, where formations that had been viewed and pictured from orbit were thought to be volcanic in nature. Since all three crew members had backed up previous Apollo lunar missions, they were familiar with the Apollo spacecraft and had more time for geology training.
Launched at 12:33 a.m. Eastern Standard Time (EST) on December 7, 1972, following the only launch-pad delay in the Apollo program, which was caused by a hardware problem, Apollo 17 was a "J-type" mission that included three days on the lunar surface, expanded scientific capability, and the use of the third Lunar Roving Vehicle (LRV). Cernan and Schmitt landed in the Taurus–Littrow valley, completed three moonwalks, took lunar samples and deployed scientific instruments. Orange soil was discovered at Shorty crater; it proved to be volcanic in origin, although from early in the Moon's history. Evans remained in lunar orbit in the command and service module (CSM), taking scientific measurements and photographs. The spacecraft returned to Earth on December 19. The mission broke several records for crewed spaceflight, including the longest crewed lunar landing mission (12 days, 14 hours), greatest distance from a spacecraft during an extravehicular activity of any type (7.6 kilometers or 4.7 miles), longest time on the lunar surface (75 hours), longest total duration of lunar-surface extravehicular activities (22 hours, 4 minutes), largest lunar-sample return (approximately 115 kg or 254 lb), longest time in lunar orbit (6 days, 4 hours), and greatest number of lunar orbits (75).
Crew and key Mission Control personnel. In 1969, NASA announced that the backup crew of Apollo 14 would be Gene Cernan, Ronald Evans, and former X-15 pilot Joe Engle. This put them in line to be the prime crew of Apollo 17, because the Apollo program's crew rotation generally meant that a backup crew would fly as prime crew three missions later. Harrison Schmitt, who was a professional geologist as well as an astronaut, had served on the backup crew of Apollo 15, and thus, because of the rotation, would have been due to fly as lunar module pilot on Apollo 18. In September 1970, the plan to launch Apollo 18 was cancelled. The scientific community pressed NASA to assign a geologist, rather than a pilot with non-professional geological training, to an Apollo landing. NASA subsequently assigned Schmitt to Apollo 17 as the lunar module pilot. After that, NASA's director of flight crew operations, Deke Slayton, was left with the question of who would fill the two other Apollo 17 slots: the rest of the Apollo 15 backup crew (Dick Gordon and Vance Brand), or Cernan and Evans from the Apollo 14 backup crew. Slayton ultimately chose Cernan and Evans. Support at NASA for assigning Cernan was not unanimous. Cernan had crashed a Bell 47G helicopter into the Indian River near Cape Kennedy during a training exercise in January 1971; the accident was later attributed to pilot error, as Cernan had misjudged his altitude before crashing into the water. Jim McDivitt, who was manager of the Apollo Spacecraft Program Office at the time, objected to Cernan's selection because of this accident, but Slayton dismissed the concern. After Cernan was offered command of the mission, he advocated for Engle to fly with him on the mission, but it was made clear to him that Schmitt would be assigned instead, with or without Cernan, so he acquiesced. The prime crew of Apollo 17 was publicly announced on August 13, 1971.
When assigned to Apollo 17, Cernan was a 38-year-old captain in the United States Navy; he had been selected in the third group of astronauts in 1963, and flown as pilot of Gemini 9A in 1966 and as lunar module pilot of Apollo 10 in 1969 before he served on Apollo 14's backup crew. Evans, 39 years old when assigned to Apollo 17, had been selected as part of the fifth group of astronauts in 1966, and had been a lieutenant commander in the United States Navy. Schmitt, a civilian, was 37 years old when assigned Apollo 17, had a doctorate in geology from Harvard University, and had been selected in the fourth group of astronauts in 1965. Both Evans and Schmitt were making their first spaceflights. For the backup crews of Apollo 16 and 17, the final Apollo lunar missions, NASA selected astronauts who had already flown Apollo lunar missions, to take advantage of their experience, and avoid investing time and money in training rookies who would be unlikely to ever fly an Apollo mission. The original backup crew for Apollo 17, announced at the same time as the prime crew, was the crew of Apollo 15: David Scott as commander, Alfred Worden as CMP and James Irwin as LMP, but in May 1972 they were removed from the backup crew because of their roles in the Apollo 15 postal covers incident. They were replaced with the landing crew of Apollo 16: John W. Young as backup crew commander, Charles Duke as LMP, and Apollo 14's CMP, Stuart Roosa. Originally, Apollo 16's CMP, Ken Mattingly, was to be assigned along with his crewmates, but he declined so he could spend more time with his family, his son having just been born, and instead took an assignment to the Space Shuttle program. Roosa had also served as backup CMP for Apollo 16.
For the Apollo program, in addition to the prime and backup crews that had been used in the Mercury and Gemini programs, NASA assigned a third crew of astronauts, known as the support crew. Their role was to provide any assistance in preparing for the missions that the missions director assigned then. Preparations took place in meetings at facilities across the US and sometimes needed a member of the flight crew to attend them. Because McDivitt was concerned that problems could be created if a prime or backup crew member was unable to attend a meeting, Slayton created the support crews to ensure that someone would be able to attend in their stead. Usually low in seniority, they also assembled the mission's rules, flight plan and checklists, and kept them updated; for Apollo 17, they were Robert F. Overmyer, Robert A. Parker and C. Gordon Fullerton. Flight directors were Gerry Griffin, first shift, Gene Kranz and Neil B. Hutchinson, second shift, and Pete Frank and Charles R. Lewis, third shift. According to Kranz, flight directors during the program Apollo had a one-sentence job description, "The flight director may take any actions necessary for crew safety and mission success." Capsule communicators (CAPCOMs) were Fullerton, Parker, Young, Duke, Mattingly, Roosa, Alan Shepard and Joseph P. Allen.
Mission insignia and call signs. The insignia's most prominent feature is an image of the Greek sun god Apollo backdropped by a rendering of an American eagle, the red bars on the eagle mirroring those on the U.S. flag. Three white stars above the red bars represent the three crewmembers of the mission. The background includes the Moon, the planet Saturn, and a galaxy or nebula. The wing of the eagle partially overlays the Moon, suggesting humanity's established presence there. The insignia includes, along with the colors of the U.S. flag (red, white, and blue), the color gold, representative of a "golden age" of spaceflight that was to begin with Apollo 17. The image of Apollo in the mission insignia is a rendering of the "Apollo Belvedere" sculpture in the Vatican Museums. It looks forward into the future, towards the celestial objects shown in the insignia beyond the Moon. These represent humanity's goals, and the image symbolizes human intelligence, wisdom and ambition. The insignia was designed by artist Robert McCall, based on ideas from the crew.
In deciding the call signs for the command module (CM) and lunar module (LM), the crew wished to pay tribute to the American public for their support of the Apollo program, and to the mission, and wanted names with a tradition within American history. The CM was given the call sign "America". According to Cernan, this evoked the 19th century sailing ships which were given that name, and was a thank-you to the people of the United States. The crew selected the name "Challenger" for the LM in lieu of an alternative, "Heritage". Cernan stated that the selected name "just seemed to describe more of what the future for America really held, and that was a challenge". After Schmitt stepped onto the Moon from "Challenger", he stated, "I think the next generation ought to accept this as a challenge. Let's see them leave footprints like these." Planning and training. Scheduling and landing site selection. Prior to the cancellation of Apollo 18 through 20, Apollo 17 was slated to launch in September 1971 as part of NASA's tentative launch schedule set forth in 1969. The in-flight abort of Apollo 13 and the resulting modifications to the Apollo spacecraft delayed subsequent missions. Following the cancellation of Apollo 20 in early 1970, NASA decided there would be no more than two Apollo missions per year. Part of the reason Apollo 17 was scheduled for December 1972 was to make it fall after the presidential election in November, ensuring that if there was a disaster, it would have no effect on President Richard Nixon's re-election campaign. Nixon had been deeply concerned about the Apollo 13 astronauts, and, fearing another mission in crisis as he ran for re-election, initially decided to omit the funds for Apollo 17 from the budget; he was persuaded to accept a December 1972 date for the mission.
Like Apollo 15 and 16, Apollo 17 was slated to be a "J-mission", an Apollo mission type that featured lunar surface stays of three days, higher scientific capability, and the usage of the Lunar Roving Vehicle. Since Apollo 17 was to be the final lunar landing of the Apollo program, high-priority landing sites that had not been visited previously were given consideration for potential exploration. Some sites were rejected at earlier stages. For instance, a landing in the crater Copernicus was rejected because Apollo 12 had already obtained samples from that impact, and three other Apollo expeditions had already visited the vicinity of Mare Imbrium, near the rim of which Copernicus is located. The lunar highlands near the crater Tycho were rejected because of the rough terrain that the astronauts would encounter there. A site on the lunar far side in the crater Tsiolkovskiy was rejected due to technical considerations and the operational costs of maintaining communication with Earth during surface operations. Lastly, a landing in a region southwest of Mare Crisium was rejected on the grounds that a Soviet spacecraft could easily access the site and retrieve samples; Luna 20 ultimately did so shortly after the Apollo 17 site selection was made. Schmitt advocated for a landing on the far side of the Moon until told by Director of Flight Operations Christopher C. Kraft that it would not happen as NASA lacked the funds for the necessary communications satellites.
The three sites that made the final consideration for Apollo 17 were Alphonsus crater, Gassendi crater, and the Taurus–Littrow valley. In making the final landing site decision, mission planners considered the primary objectives for Apollo 17: obtaining old highlands material a substantial distance from Mare Imbrium, sampling material from young volcanic activity (i.e., less than three billion years), and having minimal ground overlap with the orbital ground tracks of Apollo 15 and Apollo 16 to maximize the amount of new data obtained. A significant reason for the selection of Taurus–Littrow was that Apollo 15's CMP, Al Worden, had overflown the site and observed features he described as likely volcanic in nature. Gassendi was eliminated because NASA felt that its central peak would be difficult to reach due to the roughness of the local terrain, and, though Alphonsus might be easier operationally than Taurus–Littrow, it was of lesser scientific interest. At Taurus–Littrow, it was believed that the crew would be able to obtain samples of old highland material from the remnants of a landslide event that occurred on the south wall of the valley and the possibility of relatively young, explosive volcanic activity in the area. Although the valley is similar to the landing site of Apollo 15 in that it is on the border of a lunar mare, the advantages of Taurus–Littrow were believed to outweigh the drawbacks. The Apollo Site Selection Board, a committee of NASA personnel and scientists charged with setting out scientific objectives of the Apollo landing missions and selecting landing sites for them, unanimously recommended Taurus–Littrow at its final meeting in February 1972. Upon that recommendation, NASA selected Taurus–Littrow as the landing site for Apollo 17.
Training. As with previous lunar landings, the Apollo 17 astronauts undertook an extensive training program that included learning to collect samples on the surface, usage of the spacesuits, navigation in the Lunar Roving Vehicle, field geology training, survival training, splashdown and recovery training, and equipment training. The geology field trips were conducted as much as possible as if the astronauts were on the Moon: they would be provided with aerial images and maps, and briefed on features of the site and a suggested routing. The following day, they would follow the route, and have tasks and observations to be done at each of the stops. The geology field trips began with one to Big Bend National Park in Texas in October 1971. The early ones were not specifically tailored to prepare the astronauts for Taurus–Littrow, which was not selected until February 1972, but by June, the astronauts were going on field trips to sites specifically selected to prepare for Apollo 17's landing site. Both Cernan and Schmitt had served on backup crews for Apollo landing missions, and were familiar with many of the procedures. Their trainers, such as Gordon Swann, feared that Cernan would defer to Schmitt as a professional geologist on matters within his field. Cernan also had to adjust for the loss of Engle, with whom he had trained for Apollo 14. In spite of these issues, Cernan and Schmitt worked well together as a team, and Cernan became adept at describing what he was seeing on geology field trips, and working independently of Schmitt when necessary.
The landing crew aimed for a division of labor so that, when they arrived in a new area, Cernan would perform tasks such as adjusting the antenna on the Lunar Roving Vehicle so as to transmit to Earth while Schmitt gave a report on the geological aspects of the site. The scientists in the geology "backroom" relied on Schmitt's reports to adjust the tasks planned for that site, which would be transmitted to the CapCom and then to Cernan and Schmitt. According to William R. Muehlberger, one of the scientists who trained the astronauts, "In effect [Schmitt] was running the mission from the Moon. But we set it up this way. All of those within the geological world certainly knew it, and I had a sneaking hunch that the top brass knew it too, but this is a practical way out, and they didn't object." Also participating in some of the geology field trips were the commander and lunar module pilot of the backup crew. The initial field trips took place before the Apollo 15 astronauts were assigned as the backup crew for Apollo 17 in February 1972. Either one or both of Scott and Irwin of Apollo 15 took part in four field trips, though both were present together for only two of them. After they were removed from the backup crew, the new backup commander and LMP, Young and Duke, took part in the final four field trips. On field trips, the backup crew would follow half an hour after the prime crew, performing identical tasks, and have their own simulated CapCom and Mission Control guiding them. The Apollo 17 astronauts had fourteen field trips—the Apollo 11 crew had only one.
Evans did not go on the geology field trips, having his own set of trainers—by this time, geology training for the CMP was well-established. He would fly with a NASA geologist/pilot, Dick Laidley, over geologic features, with part of the exercise conducted at , and part at to . The higher altitude was equivalent to what could be seen from the planned lunar orbit of about 60 nmi with binoculars. Evans would be briefed for several hours before each exercise, and given study guides; afterwards, there would be debriefing and evaluation. Evans was trained in lunar geology by Farouk El-Baz late in the training cycle; this continued until close to launch. The CMP was given information regarding the lunar features he would overfly in the CSM and which he was expected to photograph. Mission hardware and experiments. Spacecraft and launch vehicle. The Apollo 17 spacecraft comprised CSM-114 (consisting of Command Module 114 (CM-114) and Service Module 114 (SM-114)); Lunar Module 12 (LM-12); a Spacecraft-Lunar Module Adapter (SLA) numbered SLA-21; and a Launch Escape System (LES). The LES contained a rocket motor that would propel the CM to safety in the event of an aborted mission in the moments after launch, while the SLA housed the LM during the launch and early part of the flight. The LES was jettisoned after the launch vehicle ascended to the point that it was not needed, while the SLA was left atop the S-IVB third stage of the rocket after the CSM and LM separated from it.
The launch vehicle, SA-512, was one of fifteen Saturn V rockets built, and was the twelfth to fly. With a weight at launch of ( of which was attributable to the spacecraft), Apollo 17's vehicle was slightly lighter than Apollo 16, but heavier than every other crewed Apollo mission. Preparation and assembly. The first piece of the launch vehicle to arrive at Kennedy Space Center was the S-II second stage, on October 27, 1970; it was followed by the S-IVB on December 21; the S-IC first stage did not arrive until May 11, 1972, followed by the Instrument Unit on June 7. By then, LM-12 had arrived, the ascent stage on June 16, 1971, and the descent stage the following day; they were not mated until May 18, 1972. CM-114, SM-114 and SLA-21 all arrived on March 24, 1972. The rover reached Kennedy Space Center on June 2, 1972. The CM and the service module (SM) were mated on March 28, 1972, and the testing of the spacecraft began that month. The CSM was placed in a vacuum chamber at Kennedy Space Center, and the testing was conducted under those conditions. The LM was also placed in a vacuum chamber; both the prime and the backup crews participated in testing the CSM and LM. During the testing, it was discovered that the LM's rendezvous radar assembly had received too much voltage during earlier tests; it was replaced by the manufacturer, Grumman. The LM's landing radar also malfunctioned intermittently and was also replaced. The front and rear steering motors of the Lunar Roving Vehicle (LRV) also had to be replaced, and it required several modifications. Following the July 1972 removal from the vacuum chamber, the LM's landing gear was installed, and it, the CSM and the SLA were mated to each other. The combined craft was moved into the Vehicle Assembly Building in August for further testing, after which it was mounted on the launch vehicle. After completing testing, including a simulated mission, the LRV was placed in the LM on August 13.
Erection of the stages of the launch vehicle began on May 15, 1972, in High Bay 3 of the Vehicle Assembly Building, and was completed on June 27. Since the launch vehicles for Skylab 1 and Skylab 2 were being processed in that building at the same time, this marked the first time NASA had three launch vehicles there since the height of the Apollo program in 1969. After the spacecraft was mounted on the launch vehicle on August 24, it was rolled out to Pad 39-A on August 28. Although this was not the final time a Saturn V would fly (another would lift Skylab to orbit), area residents reacted as though it was, and 5,000 of them watched the rollout, during which the prime crew joined the operating crew from Bendix atop the crawler. At Pad 39-A, testing continued, and the CSM was electrically mated to the launch vehicle on October 11, 1972. Testing concluded with the countdown demonstration tests, accomplished on November 20 and 21. The countdown to launch began at 7:53 a.m. (12:53 UTC) on December 5, 1972. Lunar surface science.
ALSEP. The Apollo Lunar Surface Experiments Package was a suite of nuclear-powered experiments, flown on each landing mission after Apollo 11. This equipment was to be emplaced by the astronauts to continue functioning after the astronauts returned to Earth. For Apollo 17, the ALSEP experiments were a Heat Flow Experiment (HFE), to measure the rate of heat flow from the interior of the Moon, a Lunar Surface Gravimeter (LSG), to measure alterations in the lunar gravity field at the site, a Lunar Atmospheric Composition Experiment (LACE), to investigate what the lunar atmosphere is made up of, a Lunar Seismic Profiling Experiment (LSPE), to detect nearby seismic activity, and a Lunar Ejecta and Meteorites Experiment (LEME), to measure the velocity and energy of dust particles. Of these, only the HFE had been flown before; the others were new.
All powered ALSEP experiments that remained active were deactivated on September 30, 1977, principally because of budgetary constraints. Other lunar-surface science. Like Apollo 15 and 16, Apollo 17 carried a Lunar Roving Vehicle. In addition to being used by the astronauts for transport from station to station on the mission's three moonwalks, the LRV was used to transport the astronauts' tools, communications equipment, and the lunar samples they gathered. The Apollo 17 LRV was also used to carry some of the scientific instruments, such as the Traverse Gravimeter Experiment (TGE) and Surface Electrical Properties (SEP) experiment. The Apollo 17 LRV traveled a cumulative distance of approximately in a total drive time of about four hours and twenty-six minutes; the greatest distance Cernan and Schmitt traveled from the lunar module was about . This was the only mission to carry the TGE, which was built by Draper Laboratory at the Massachusetts Institute of Technology. As gravimeters had been useful in studying the Earth's internal structure, the objective of this experiment was to do the same on the Moon. The gravimeter was used to obtain relative gravity measurements at the landing site in the immediate vicinity of the lunar module, as well as various locations on the mission's traverse routes. Scientists would then use this data to help determine the geological substructure of the landing site and the surrounding vicinity. Measurements were taken while the TGE was mounted on the LRV, and also while the device was placed on the lunar surface. A total of 26 measurements were taken with the TGE during the mission's three moonwalks, with productive results.
The SEP was also unique to Apollo 17, and included two major components: a transmitting antenna deployed near the lunar module and a receiver mounted on the LRV. At different stops during the mission's traverses, electrical signals traveled from the transmitting device, through the ground, and were received at the LRV. The electrical properties of the lunar regolith could be determined by comparison of the transmitted and received electrical signals. The results of this experiment, which are consistent with lunar rock composition, show that there is almost no water in the area of the Moon in which Apollo 17 landed, to a depth of . A long, diameter device, the Lunar Neutron Probe was inserted into one of the holes drilled into the surface to collect core samples. It was designed to measure the quantity of neutrons which penetrated to the detectors it bore along its length. This was intended to measure the rate of the "gardening" process on the lunar surface, whereby the regolith on the surface is slowly mixed or buried due to micrometeorites and other events. Placed during the first EVA, it was retrieved during the third and final EVA. The astronauts brought it with them back to Earth, and the measurements from it were compared with the evidence of neutron flux in the core that had been removed from the hole it had been placed in. Results from the probe and from the cores were instrumental in current theories that the top centimeter of lunar regolith turns over every million years, whereas "gardening" to a depth of one meter takes about a billion years.
Orbital science. Biological experiments. Apollo 17's CM carried a biological cosmic ray experiment (BIOCORE), containing five mice that had been implanted with radiation monitors under their scalps to see whether they suffered damage from cosmic rays. These animals were placed in individual metal tubes inside a sealed container that had its own oxygen supply, and flown on the mission. All five were pocket mice ("Perognathus longimembris"); this species was chosen because it was well-documented, small, easy to maintain in an isolated state (not requiring drinking water during the mission and with highly concentrated waste), and for its ability to withstand environmental stress. Officially, the mice—four male and one female—were assigned the identification numbers A3326, A3400, A3305, A3356 and A3352. Unofficially, according to Cernan, the Apollo 17 crew dubbed them Fe, Fi, Fo, Fum, and Phooey. Four of the five mice survived the flight, though only two of them appeared healthy and active; the cause of death of the fifth mouse was not determined. Of those that survived, the study found lesions in the scalp itself and, in one case, the liver. The scalp lesions and liver lesions appeared to be unrelated to one another; nothing was found that could be attributed to cosmic rays.
The Biostack experiment was similar to one carried on Apollo 16, and was designed to test the effects of the cosmic rays encountered in space travel on microorganisms that were included, on seeds, and on the eggs of simple animals (brine shrimp and beetles), which were carried in a sealed container. After the mission, the microorganisms and seeds showed little effect, but many of the eggs of all species failed to hatch, or to mature normally; many died or displayed abnormalities. Scientific Instrument Module. The Apollo 17 SM contained the scientific instrument module (SIM) bay. The SIM bay housed three new experiments for use in lunar orbit: a lunar sounder, an infrared scanning radiometer, and a far-ultraviolet spectrometer. A mapping camera, panoramic camera, and a laser altimeter, which had been carried previously, were also included in the SIM bay. The lunar sounder was to beam electromagnetic impulses toward the lunar surface, which were designed with the objective of obtaining data to assist in developing a geological model of the interior of the Moon to an approximate depth of . The infrared scanning radiometer was designed with the objective of generating a temperature map of the lunar surface to aid in locating surface features such as rock fields, structural differences in the lunar crust, and volcanic activity. The far-ultraviolet spectrometer was to be used to obtain information on the composition, density, and constituency of the lunar atmosphere. The spectrometer was also designed to detect far-UV radiation emitted by the Sun that had been reflected off the lunar surface. The laser altimeter was designed to measure the altitude of the spacecraft above the lunar surface within approximately , providing altitude information to the panoramic and mapping cameras, which were also in the SIM bay.
Light-flash phenomenon and other experiments. Beginning with Apollo 11, crew members observed light flashes that penetrated their closed eyelids. These flashes, described by the astronauts as "streaks" or "specks" of light, were usually observed while the spacecraft was darkened during a sleep period. These flashes, while not observed on the lunar surface, would average about two per minute and were observed by the crew members during the trip out to the Moon, back to Earth, and in lunar orbit. The Apollo 17 crew repeated an experiment, also conducted on Apollo 16, with the objective of linking these light flashes with cosmic rays. Evans wore a device over his eyes that recorded the time, strength, and path of high-energy atomic particles that penetrated the device, while the other two wore blindfolds to keep out light. Investigators concluded that the available evidence supports the hypothesis that these flashes occur when charged particles travel through the retina in the eye. Apollo 17 carried a sodium-iodide crystal identical to the ones in the gamma-ray spectrometer flown on Apollo 15 and 16. Data from this, once it was examined on Earth, was to be used to help form a baseline, allowing for subtraction of rays from the CM or from cosmic radiation to gain better data from the earlier results. In addition, the S-band transponders in the CSM and LM were pointed at the Moon to gain data on its gravitational field. Results from the Lunar Orbiter probes had revealed that lunar gravity varies slightly due to the presence of mass concentrations, or "mascons". Data from the missions, and from the lunar subsatellites left by Apollo 15 and 16, were used to map such variations in lunar gravity.
Mission events. Launch and outbound trip. Originally planned to launch on December 6, 1972, at 9:53 p.m. EST (2:53 a.m. on December 7 UTC), Apollo 17 was the final crewed SaturnV launch, and the only one to occur at night. The launch was delayed by two hours and forty minutes due to an automatic cutoff in the launch sequencer at the T−30 second mark in the countdown. The cause of the problem was quickly determined to be the launch sequencer's failure to automatically pressurize the liquid oxygen tank in the third stage of the rocket; although launch control noticed this and manually caused the tank to pressurize, the sequencer did not recognize the fix and therefore paused the countdown. The clock was reset and held at the T−22 minute mark while technicians worked around the malfunction in order to continue with the launch. This pause was the only launch delay in the Apollo program caused by a hardware problem. The countdown then resumed, and the liftoff occurred at 12:33 a.m. EST on December 7, 1972. The launch window, which had begun at the originally planned launch time of 9:53 p.m. on December 6, remained open until 1:31 a.m., the latest time at which a launch could have occurred during the December 6–7 window.
Approximately 500,000 people observed the launch in the immediate vicinity of Kennedy Space Center, despite the early-morning hour. The launch was visible as far away as , and observers in Miami, Florida, reported a "red streak" crossing the northern sky. Among those in attendance at the program's final launch were astronauts Neil Armstrong and Dick Gordon, as well as centenarian Charlie Smith, who alleged he was 130 years old at the time of Apollo 17. The ascent resulted in an orbit with an altitude and velocity almost exactly that which had been planned. In the hours following the launch, Apollo 17 orbited the Earth while the crew spent time monitoring and checking the spacecraft to ensure its readiness to depart Earth orbit. At 3:46 a.m. EST, the S-IVB third stage was reignited for the 351-second trans-lunar injection burn to propel the spacecraft towards the Moon. Ground controllers chose a faster trajectory for Apollo 17 than originally planned to allow the vehicle to reach lunar orbit at the planned time, despite the launch delay. The Command and Service Module separated from the S-IVB approximately half an hour following the S-IVB trans-lunar injection burn, after which Evans turned the spacecraft to face the LM, still attached to the S-IVB. The CSM then docked with the LM and extracted it from the S-IVB. Following the LM extraction, Mission Control programmed the S-IVB, no longer needed to propel the spacecraft, to impact the Moon and trip the seismometers left by prior Apollo crews. It struck the Moon just under 87 hours into the mission, triggering the seismometers from Apollo 12, 14, 15 and 16. Approximately nine hours after launch, the crew concluded the mission's first day with a sleep period, until waking up to begin the second day.
Mission Control and the crew decided to shorten the mission's second day, the first full day in space, in order to adjust the crew's wake-up times for the subsequent days in preparation for an early morning (EST) wake-up time on the day of the lunar landing, then scheduled for early afternoon (EST). This was done since the first day of the mission had been extended because of the launch delay. Following the second rest period, and on the third day of the mission, the crew executed the first mid-course correction, a two-second burn of the CSM's service propulsion engine to adjust the spacecraft's Moon-bound trajectory. Following the burn, the crew opened the hatch separating the CSM and LM in order to check the LM's systems and concluded that they were nominal. So that events would take place at the time indicated in the flight plan, the mission clocks were moved ahead by 2 hours and 40 minutes, the amount of the launch delay, with one hour of it at 45:00:00 into the mission and the remainder at 65:00:00. Among their other activities during the outbound trip, the crew photographed the Earth from the spacecraft as it travelled towards the Moon. One of these photographs is now known as "The Blue Marble". The crew found that one of the latches holding the CSM and LM together was unlatched. While Schmitt and Cernan were engaged in a second period of LM housekeeping beginning just before sixty hours into the Mission, Evans worked on the balky latch. He was successful, and left it in the position it would need to be in for the CSM-LM docking that would occur upon return from the lunar surface.
Also during the outward journey, the crew performed a heat flow and convection demonstration, as well as the Apollo light-flash experiment. A few hours before entry into lunar orbit, the SIM door on the SM was jettisoned. At approximately 2:47 p.m. EST on December 10, the service propulsion system engine on the CSM ignited to slow down the CSM/LM stack into lunar orbit. Following orbit insertion and orbital stabilization, the crew began preparations for the landing at Taurus–Littrow. Lunar landing. The day of the landing began with a checkout of the Lunar Module's systems, which revealed no problems preventing continuation of the mission. Cernan, Evans, and Schmitt each donned their spacesuits, and Cernan and Schmitt entered the LM in preparation for separating from the CSM and landing. The LM undocked from the CSM, and the two spacecraft orbited close together for about an hour and a half while the astronauts made visual inspections and conducted their final pre-landing checks. After finally separating from the CSM, the LM "Challenger" and its crew of two adjusted their orbit, such that its lowest point would pass about above the landing site, and began preparations for the descent to Taurus–Littrow. While Cernan and Schmitt prepared for landing, Evans remained in orbit to take observations, perform experiments and await the return of his crewmates a few days later.
Soon after completing their preparations for landing and just over two hours following the LM's undocking from the CSM, Cernan and Schmitt began their descent to the Taurus–Littrow valley on the lunar surface with the ignition of the Lunar Module's descent propulsion system (DPS) engine. Approximately ten minutes later, as planned, the LM pitched over, giving Cernan and Schmitt their first look at the landing site during the descent phase and allowing Cernan to guide the spacecraft to a desirable landing target while Schmitt provided data from the flight computer essential for landing. The LM touched down on the lunar surface at 2:55 p.m. EST on December 11, just over twelve minutes after DPS ignition. "Challenger" landed about east of the planned landing point. Shortly thereafter, the two astronauts began re-configuring the LM for their stay on the surface and began preparations for the first moonwalk of the mission, or EVA-1. Lunar surface. First EVA. During their approximately 75-hour stay on the lunar surface, Cernan and Schmitt performed three moonwalks (EVAs). The astronauts deployed the LRV, then emplaced the ALSEP and the seismic explosive charges. They drove the rover to nine planned geological-survey stations to collect samples and make observations. Additionally, twelve short sampling stops were made at Schmitt's discretion while riding the rover, during which the astronauts used a handled scoop to get a sample, without dismounting. During lunar-surface operations, Commander Cernan always drove the rover, while Lunar Module Pilot Schmitt was a passenger who assisted with navigation. This division of responsibilities between the two crew positions was used consistently throughout Apollo's J-missions.
The first lunar excursion began four hours after landing, at 6:54 p.m. EST on December 11. After exiting through the hatch of the LM and descending the ladder to the footpad, Cernan took the first step on the lunar surface of the mission. Just before doing so, Cernan remarked, "I'm on the footpad. And, Houston, as I step off at the surface at Taurus–Littrow, we'd like to dedicate the first step of Apollo 17 to all those who made it possible." After Cernan surveyed the exterior of the LM and commented on the immediate landing site, Schmitt joined Cernan on the surface. The first task was to offload the rover and other equipment from the LM. While working near the rover, Cernan caught his hammer under the right-rear fender extension, accidentally breaking it off. A similar incident occurred on Apollo 16 as John Young maneuvered around the rover. Although this was not a mission-critical issue, the loss of the part caused Cernan and Schmitt to be covered with dust stirred up when the rover was in motion. The crew made a short-lived fix using duct tape at the beginning of the second EVA, attaching a paper map to the damaged fender.
The crew made a short-lived fix using duct tape at the beginning of the second EVA, attaching a paper map to the damaged fender. Lunar dust stuck to the tape's surface, however, preventing it from adhering properly. Following deployment and testing the maneuverability of the rover, the crew deployed the ALSEP just west of the landing site. The ALSEP deployment took longer than had been planned, with the drilling of core holes presenting some difficulty, meaning the geological portion of the first EVA would need to be shortened, cancelling a planned visit to Emory crater. Instead, following the deployment of the ALSEP, Cernan and Schmitt drove to Steno crater, to the south of the landing site. The objective at Steno was to sample the subsurface material excavated by the impact that formed the crater. The astronauts gathered of samples, took seven gravimeter measurements, and deployed two explosive packages. The explosive packages were later detonated remotely; the resulting explosions detected by geophones placed by the astronauts and also by seismometers left during previous missions. The explosive packages were later detonated remotely; the resulting explosions detected by geophones placed by the astronauts and also by seismometers left during previous missions. The first EVA ended after seven hours and twelve minutes. and the astronauts remained in the pressurized LM for the next 17 hours.
Second EVA. On December 12, awakened by a recording of "Ride of the Valkyries" played from Mission Control, Cernan and Schmitt began their second lunar excursion. The first order of business was to provide the rover's fender a better fix. Overnight, the flight controllers devised a procedure communicated by John Young: taping together four stiff paper maps to form a "replacement fender extension" and then clamping it onto the fender. The astronauts carried out the new fix which did its job without failing until near the end of the third excursion. Cernan and Schmitt then departed for station 2—Nansen Crater, at the foot of the South Massif. When they arrived, their range from the "Challenger" was 7.6 kilometers (4.7 miles, 25,029 feet). This remains the furthest distance any spacefarers have ever traveled away from the safety of a pressurizable spacecraft while on a planetary body, and also during an EVA of any type. The astronauts were at the extremity of their "walkback limit", a safety constraint meant to ensure that they could walk back to the LM if the rover failed. They began a return trip, traveling northeast in the rover.
At station 3, Schmitt fell to the ground while working, looking so awkward that Parker jokingly told him that NASA's switchboard had lit up seeking Schmitt's services for Houston's ballet group, and the site of station 3 was in 2019 renamed Ballet Crater. Cernan took a sample at Station 3 that was to be maintained in vacuum until better analytical techniques became available, joking with the CAPCOM, Parker, about placing a note inside. The container remained unopened until 2022. Stopping at station 4—Shorty crater—the astronauts discovered orange soil, which proved to be very small beads of volcanic glass formed over 3.5 billion years ago. This discovery caused great excitement among the scientists at Mission Control, who felt that the astronauts may have discovered a volcanic vent. However, post-mission sample analysis revealed that Shorty is not a volcanic vent, but rather an impact crater. Analysis also found the orange soil to be a remnant of a lava fountain. This lava fountain sprayed molten lava high into the lunar sky in the Moon's early days, some 3.5 billion years ago and long before Shorty's creation. The orange volcanic beads were droplets of molten lava from the fountain that solidified and were buried by lava deposits until exposed by the impact that formed Shorty, less than 20 million years ago.
The final stop before returning to the LM was Camelot crater; throughout the sojourn, the astronauts collected of samples, took another seven gravimeter measurements, and deployed three more explosive packages. Concluding the EVA at seven hours and thirty-seven minutes, Cernan and Schmitt had completed the longest-duration EVA in history to-date, traveling further away from a spacecraft and covering more ground on a planetary body during a single EVA than any other spacefarers. The improvised fender had remained intact throughout, causing the president of the "Auto Body Association of America" to award them honorary lifetime membership. Third EVA. The third moonwalk, the last of the Apollo program, began at 5:25 p.m. EST on December 13. Cernan and Schmitt rode the rover northeast of the landing site, exploring the base of the North Massif and the Sculptured Hills. Stopping at station 6, they examined a house-sized split boulder dubbed Tracy's Rock (or Split Rock), after Cernan's daughter. The ninth and final planned station was conducted at Van Serg crater. The crew collected of lunar samples and took another nine gravimeter measurements. Schmitt had seen a fine-grained rock, unusual for that vicinity, earlier in the mission and had stood it on its edge; before closing out the EVA, he went and got it. Subsequently, designated Sample 70215, it was, at , the largest rock brought back by Apollo 17. A small piece of it is on exhibit at the Smithsonian Institution, one of the few rocks from the Moon that the public may touch. Schmitt also collected a sample, designated as Sample 76535, at geology station 6 near the base of the North Massif; the sample, a troctolite, was later identified as the oldest known "unshocked" lunar rock, meaning it has not been damaged by high-impact geological events. Scientists have therefore used Sample 76535 in thermochronological studies to determine if the Moon formed a metallic core or, as study results suggest, a core dynamo.
Before concluding the moonwalk, the crew collected a breccia rock, dedicating it to the nations of Earth, 70 of which were represented by students touring the U.S. and present in Mission Control Center in Houston, Texas, at the time. Portions of this sample, known as the Friendship Rock, were subsequently distributed to the nations represented by the students. A plaque located on the LM, commemorating the achievements made during the Apollo program, was then unveiled. Before reentering the LM for the final time, Cernan remarked, Cernan then followed Schmitt into the LM; the final lunar excursion had a duration of seven hours and fifteen minutes. Following closing of the LM hatch and repressurization of the LM cabin, Cernan and Schmitt removed their spacesuits and reconfigured the cabin for a final rest period on the lunar surface. As they did following each of the previous two EVAs, Cernan and Schmitt discussed their geological observations from the day's excursion with mission control while preparing to rest.
Solo activities. While Cernan and Schmitt were on the lunar surface, Evans remained alone in the CSM in lunar orbit and was assigned a number of observational and scientific tasks to perform while awaiting the return of his crewmates. In addition to the operation of the various orbital science equipment contained in the CSM's SIM bay, Evans conducted both visual and photographic observation of surface features from his aerial vantage point. The orbit of the CSM having been modified to an elliptical orbit in preparation for the LM's departure and eventual descent, one of Evans' solo tasks in the CSM was to circularize its orbit such that the CSM would remain at approximately the same distance above the surface throughout its orbit. Evans observed geological features visible to him and used handheld cameras to record certain visual targets. Evans also observed and sketched the solar corona at "sunrise," or the period of time during which the CSM would pass from the darkened portion of the Moon to the illuminated portion when the Moon itself mostly obscured the sun. To photograph portions of the surface that were not illuminated by the sun while Evans passed over them, Evans relied in conjunction on exposure and Earthlight. Evans photographed such features as the craters Eratosthenes and Copernicus, as well as the vicinity of Mare Orientale, using this technique. According to the Apollo 17 Mission Report, Evans was able to capture all scientific photographic targets, as well as some other targets of interest.
Similarly to the crew of Apollo 16, Evans (as well as Schmitt, while in lunar orbit) reported seeing light "flashes" apparently originating from the lunar surface, known as transient lunar phenomena (TLP); Evans reported seeing these "flashes" in the vicinity of Grimaldi crater and Mare Orientale. The causes of TLP are not well-understood and, though inconclusive as an explanation, both of the sites in which Evans reported seeing TLP are the general locations of outgassing from the Moon's interior. Meteorite impacts are another possible explanation. The flight plan kept Evans busy, making him so tired he overslept one morning by an hour, despite the efforts of Mission Control to awaken him. Before the LM departed for the lunar surface, Evans had discovered that he had misplaced his pair of scissors, necessary to open food packets. Cernan and Schmitt lent him one of theirs. The instruments in the SIM bay functioned without significant hindrance during the orbital portion of the mission, though the lunar sounder and the mapping camera encountered minor problems. Evans spent approximately 148 total hours in lunar orbit, including solo time and time spent together with Cernan and Schmitt, which is more time than any other individual has spent orbiting the Moon.
Evans was also responsible for piloting the CSM during the orbital phase of the mission, maneuvering the spacecraft to alter and maintain its orbital trajectory. In addition to the initial orbital recircularization maneuver shortly after the LM's departure, one of the solo activities Evans performed in the CSM in preparation for the return of his crewmates from the lunar surface was the plane change maneuver. This maneuver was meant to align the CSM's trajectory to the eventual trajectory of the LM to facilitate rendezvous in orbit. Evans fired the SPS engine of the CSM for about 20 seconds in successfully adjusting the CSM's orbital plane. Return to Earth. Cernan and Schmitt lifted off from the lunar surface in the ascent stage of the LM on December14, at 5:54 p.m. EST. The return to lunar orbit took just over seven minutes. The LM, piloted by Cernan, and the CSM, piloted by Evans, maneuvered, and redocked about two hours after liftoff from the surface. After docking, the crew transferred equipment and lunar samples from the LM to the CSM for return to Earth. The crew sealed the hatches between the CSM and the LM ascent stage following completion of the transfer and the LM was jettisoned at 11:51 p.m. EST on December14. The unoccupied ascent stage was then remotely deorbited, crashing it into the Moon with an impact recorded by the seismometers left by Apollo 17 and previous missions. At 6:35 p.m. EST on December16, the CSM's SPS engine was ignited once more to propel the spacecraft away from the Moon on a trajectory back towards Earth. The trans-Earth injection SPS burn lasted just over two minutes.
During the return to Earth, Evans performed a 65-minute EVA to retrieve film cassettes from the service module's SIM bay, with assistance from Schmitt who remained at the command module's hatch. At approximately 160,000 nautical miles (184,000 mi; 296,000 km) from Earth, it was the third "deep space" EVA in history, performed at great distance from any planetary body. As of , it remains one of only three such EVAs, all performed during Apollo's J-missions under similar circumstances. It was the last EVA of the Apollo program. During the trip back to Earth, the crew operated the infrared radiometer in the SM, as well as the ultraviolet spectrometer. One midcourse correction was performed, lasting 9 seconds. On December 19, the crew jettisoned the no-longer-needed SM, leaving only the CM for return to Earth. The Apollo 17 spacecraft reentered Earth's atmosphere and splashed down safely in the Pacific Ocean at 2:25 p.m. EST, from the recovery ship, . Cernan, Evans, and Schmitt were then retrieved by a recovery helicopter piloted by Commander Edward E. Dahill, III and were safe aboard the recovery ship 52 minutes after splashdown. As the final Apollo mission concluded successfully, Mission Control in Houston was filled with many former flight controllers and astronauts, who applauded as "America" returned to Earth.
Aftermath and spacecraft locations. Following their mission, the crew undertook both domestic and international tours, visiting 29 states and 11 countries. The tour kicked off at Super Bowl VII, with the crew leading the crowd in the Pledge of Allegiance; the CM "America" was also displayed during the pregame activities. None of the Apollo 17 astronauts flew in space again. Cernan retired from NASA and the Navy in 1976. He died in 2017. Evans retired from the Navy in 1976 and from NASA in 1977, entering the private sector. He died in 1990. Schmitt resigned from NASA in 1975 prior to his successful run for a United States Senate seat from New Mexico in 1976. There, he served one six-year term. The Command Module "America" is currently on display at Space Center Houston at the Lyndon B. Johnson Space Center in Houston, Texas. The ascent stage of Lunar Module "Challenger" impacted the Moon on December 15, 1972, at 06:50:20.8 UTC (1:50 a.m. EST), at . The descent stage remains on the Moon at the landing site, . In 2023, a study of Apollo-era data from the Lunar Seismic Profiling Experiment showed that the descent stage was causing very slight tremors each lunar morning as components expanded in the heat.
Eugene Cernan's flown Apollo 17 spacesuit is in the collection of the Smithsonian's National Air and Space Museum (NASM), where it was transferred in 1974, and Harrison Schmitt's is in storage at NASM's Paul E. Garber Facility. Amanda Young of NASM indicated in 2004 that Schmitt's suit is in the best condition of the flown Apollo lunar spacesuits, and therefore is not on public display. Ron Evans' spacesuit was also transferred from NASA in 1974 to the collection of the NASM; it remains in storage. Since Apollo 17's return, there have been attempts to photograph the landing site, where the LM's descent stage, LRV and some other mission hardware, remain. In 2009 and again in 2011, the Lunar Reconnaissance Orbiter photographed the landing site from increasingly low orbits. At least one group has indicated an intention to visit the site as well; in 2018, the German space company PTScientists said that it planned to land two lunar rovers nearby.
American Revolution The American Revolution (1765–1783) was an ideological and political movement in the Thirteen Colonies in what was then British America. The revolution culminated in the American Revolutionary War, which was launched on April 19, 1775, in the Battles of Lexington and Concord. Leaders of the American Revolution were colonial separatist leaders who, as British subjects, initially sought incremental levels of autonomy but came to embrace the cause of full independence and the necessity of prevailing in the Revolutionary War to obtain it. The Second Continental Congress, which represented the colonies and convened in present-day Independence Hall in Philadelphia, formed the Continental Army and appointed George Washington as its commander-in-chief in June 1775, and unanimously adopted the Declaration of Independence the following year, which inspired, formalized, and escalated the war. For most of the eight-year war, its outcome appeared uncertain. But in 1781, a decisive victory by Washington and the Continental Army in the Siege of Yorktown inspired King George III and the British to negotiate an end to colonial rule in the colonies and acknowledge their independence, which was codified in the Treaty of Paris in 1783, leading to the establishment of the sovereign United States of America.
Discontent with colonial rule began shortly after the defeat of France in the French and Indian War in 1763. Even though the colonies had fought in and supported the war, British Parliament imposed new taxes to compensate for wartime costs and turned control of the colonies' western lands over to the British officials in Montreal. Representatives from several colonies convened the Stamp Act Congress in 1765; its "Declaration of Rights and Grievances" argued that taxation without representation violated their rights as Englishmen. In 1767, tensions flared again following British Parliament's passage of the Townshend Acts. In an effort to quell the mounting rebellion, King George III deployed British troops to Boston, where British troops killed protesters in the Boston Massacre on March 5, 1770. In 1772, anti-tax demonstrators destroyed the Royal Navy customs schooner "Gaspee" off present-day Warwick, Rhode Island. On December 16, 1773, in a seminal event in the American Revolution's escalation, Sons of Liberty activists wearing costumes of Native Americans instigated the Boston Tea Party, during which they boarded and dumped chests of tea owned by the British East India Company into Boston Harbor. London responded by closing Boston Harbor and enacting a series of punitive laws, which effectively ended self-government in Massachusetts but also served to expand and intensify the revolutionary cause.
In late 1774, 12 of the Thirteen Colonies sent delegates to the First Continental Congress, which met inside Carpenters' Hall in Philadelphia; the Province of Georgia joined in 1775. The First Continental Congress began coordinating Patriot resistance through underground networks of committees. Following the Battles of Lexington and Concord, Washington and the Continental Army responded by surrounding Boston, forcing the British to withdraw by sea in March 1776, and leaving Patriots in control in every colony. In August 1775, King George III proclaimed Massachusetts to be in a state of open defiance and rebellion. In 1776, the Second Continental Congress began debating and deliberating on the Articles of Confederation, an effort to establish a self-governing rule of law in the Thirteen Colonies. On July 2, they passed the Lee Resolution, affirming their support for national independence, and on July 4, 1776, they unanimously adopted the Declaration of Independence, authored primarily by Thomas Jefferson, which embodied the political philosophies of liberalism and republicanism, rejected monarchy and aristocracy, and famously proclaimed that "all men are created equal".
The Revolutionary War continued for another five years during which France ultimately entered the war, supporting the colonial cause of independence. On September 28, 1781, Washington, with support from Marquis de Lafayette, the French Army, and French Navy, led the Continental Army's most decisive victory, capturing roughly 7,500 British troops led by British general Charles Cornwallis during the Siege of Yorktown, leading to the collapse of King George's control of Parliament and consensus in Parliament that the war should be ended on American terms. On September 3, 1783, the British signed the Treaty of Paris, granting their former colonies nearly all the territory east of the Mississippi River and south of the Great Lakes. About 60,000 Loyalists migrated to other British territories in Canada and elsewhere, but the great majority remained in the United States. With its victory in the American Revolution, the United States became the first constitutional republic in world history founded on the consent of the governed and the rule of law.
Origins. Under the British policy of salutary neglect, Britain traded with the colonies but otherwise mostly left them alone over the first 150 years of the colonies’ existence. The colonists became accustomed to running their own affairs, and they liked it. This British policy changed significantly after the French and Indian War, prompting the Thirteen Colonies to seek greater autonomy from Britain. After the Revolution, one colonist, Capt. Levi Preston, of Danvers, Massachusetts, was asked why the Americans rebelled against England, responded, "…we always had governed ourselves, and we always meant to. They didn’t mean we should." 1651–1763: Early seeds. The Thirteen Colonies were established in the 17th century as part of the English Empire, and they formed part of the British Empire after the union of England and Scotland in 1707. The development of a unique American identity can be traced to the English Civil War (1642–1651) and its aftermath. The Puritan colonies of New England supported the Commonwealth government responsible for the execution of King Charles I. After the Stuart Restoration of 1660, Massachusetts did not recognize Charles II as the legitimate king for more than a year after his coronation. In King Philip's War (1675–1678), the New England colonies fought a handful of Native American tribes without military assistance from England, thereby contributing to the development of a uniquely American identity separate from that of the British people.
In the 1680s, Charles and his brother, James II, attempted to bring New England under direct English control. The colonists fiercely opposed this, and the Crown nullified their colonial charters in response. In 1686, James finalized these efforts by consolidating the separate New England colonies along with New York and New Jersey into the Dominion of New England. Edmund Andros was appointed royal governor and tasked with governing the new Dominion under his direct rule. Colonial assemblies and town meetings were restricted, new taxes were levied, and rights were abridged. Dominion rule triggered bitter resentment throughout New England. When James tried to rule without Parliament, the English aristocracy removed him from power in the Glorious Revolution of 1688. This was followed by the 1689 Boston revolt, which overthrew Dominion rule. Colonial governments reasserted their control after the revolt. The new monarchs, William and Mary, granted new charters to the individual New England colonies, and local democratic self-government was restored.
After the Glorious Revolution in 1688, the British Empire was a constitutional monarchy with sovereignty in the King-in-Parliament. Aristocrats inherited seats in the House of Lords, while the gentry and merchants controlled the elected House of Commons. The king ruled through cabinet ministers who depended on majority support in the Commons to govern effectively. British subjects on both sides of the Atlantic proudly claimed the unwritten British constitution, with its guarantees of the rights of Englishmen, protected personal liberty better than any other government. It served as the model for colonial governments. The Crown appointed a royal governor to exercise executive power. Property owners elected a colonial assembly with powers to legislate and levy taxes, but the British government reserved the right to veto colonial legislation. Radical Whig ideology profoundly influenced American political philosophy with its love of liberty and opposition to tyrannical government. With little industry except shipbuilding, the colonies exported agricultural products to Britain in return for manufactured goods. They also imported molasses, rum, and sugar from the British West Indies. The British government pursued a policy of mercantilism in order to grow its economic and political power. According to mercantilism, the colonies existed for the mother country's economic benefit, and the colonists' economic needs took second place. In 1651, Parliament passed the first in a series of Navigation Acts, which restricted colonial trade with foreign countries. The Thirteen Colonies could trade with the rest of the empire but only ship certain commodities like tobacco to Britain. Any European imports bound for British America had to first pass through an English port and pay customs duties. Other laws regulated colonial industries, such as the Wool Act 1698, the Hat Act 1731, and the Iron Act 1750.
Colonial reactions to these policies were mixed. The Molasses Act 1733 placed a duty of six pence per gallon upon foreign molasses imported into the colonies. This act was particularly egregious to the New England colonists, who protested it as taxation without representation. The act increased the smuggling of foreign molasses, and the British government ceased enforcement efforts after the 1740s. On the other hand, certain merchants and local industries benefitted from the restrictions on foreign competition. The limits on foreign-built ships greatly benefitted the colonial shipbuilding industry, particularly in New England. Some argue that the economic impact was minimal on the colonists, but the political friction that the acts triggered was more serious, as the merchants most directly affected were also the most politically active. The British government lacked the resources and information needed to control the colonies. Instead, British officials negotiated and compromised with colonial leaders to gain compliance with imperial policies. The colonies defended themselves with colonial militias, and the British government rarely sent military forces to America before 1755. According to historian Robert Middlekauff, "Americans had become almost completely self-governing" before the American Revolution, a practice that was consistent with the British monarchy's practice of salutary neglect.
During the French and Indian War (1754–1763), the British government fielded 45,000 soldiers, half British Regulars and half colonial volunteers. The colonies also contributed money to the war effort; however, two-fifths of this spending was reimbursed by the British government. Great Britain defeated France and acquired that nation's territory east of the Mississippi River. In early 1763, the Bute ministry decided to permanently garrison 10,000 soldiers in North America. This would allow approximately 1,500 politically well-connected British Army officers to remain on active duty with full pay (stationing a standing army in Great Britain during peacetime was politically unacceptable). A standing army would provide defense against Native Americans in the west and foreign populations in newly acquired territories (the French in Canada and the Spanish in Florida). In addition, British soldiers could prevent white colonists from instigating conflict with Native Americans and help collect customs duties. Migration beyond the Appalachian Mountains increased after the French threat was removed, and Native Americans launched Pontiac's War (1763–1766) in response. The Grenville ministry issued the Royal Proclamation of 1763, designating the territory between the Appalachian Mountains and the Mississippi River as an Indian Reserve closed to white settlement. The Proclamation failed to stop westward migration while angering settlers, fur traders, and land speculators in the Thirteen Colonies. 1764–1766: Taxes imposed and withdrawn.
George Grenville became prime minister in 1763, and "the need for money played a part in every important decision made by Grenville regarding the colonies—and for that matter by the ministries that followed up to 1776." The national debt had grown to £133 million with annual debt payments of £5 million (out of an £8 million annual budget). Stationing troops in North America on a permanent basis would cost another £360,000 a year. On a per capita basis, Americans only paid 1 shilling in taxes to the empire compared to 26 shillings paid by the English. Grenville believed that the colonies should help pay the troop costs. In 1764 Parliament passed the Sugar Act, decreasing the existing customs duties on sugar and molasses but providing stricter measures of enforcement and collection. That same year, Grenville proposed direct taxes on the colonies to raise revenue, but he delayed action to see whether the colonies would propose some way to raise the revenue themselves.
The Parliament at Westminster saw itself as the supreme lawmaking authority throughout the Empire and thus entitled to levy any tax without colonial approval or even consultation. They argued that the colonies were legally British corporations subordinate to the British Parliament. Parliament insisted that the colonists effectively enjoyed a "virtual representation", as most British people did, since only a small minority of the British population were eligible to elect representatives to Parliament. However, Americans such as James Otis maintained that there was no one in Parliament responsible specifically to any colonial constituency, so they were not "virtually represented" by anyone in Parliament. The Rockingham government came to power in July 1765, and Parliament debated whether to repeal the stamp tax or to send an army to enforce it. Benjamin Franklin appeared before them to make the case for repeal, explaining that the colonies had spent heavily in manpower, money, and blood defending the empire, and that further taxes to pay for those wars were unjust and might bring about a rebellion. Parliament agreed and repealed the tax on February 21, 1766, but they insisted in the Declaratory Act of March 1766 that they retained full power to make laws for the colonies "in all cases whatsoever". The repeal nonetheless caused widespread celebrations in the colonies. 1767–1773: Townshend Acts and the Tea Act.
In 1767, the British Parliament passed the Townshend Acts, which placed duties on several staple goods, including paper, glass, and tea, and established a Board of Customs in Boston to more rigorously execute trade regulations. Parliament's goal was not so much to collect revenue but to assert its authority over the colonies. The new taxes were enacted on the belief that Americans only objected to internal taxes and not to external taxes such as custom duties. However, in his widely read pamphlet, "Letters from a Farmer in Pennsylvania", John Dickinson argued against the constitutionality of the acts because their purpose was to raise revenue and not to regulate trade. Colonists responded to the taxes by organizing new boycotts of British goods. These boycotts were less effective, however, as the goods taxed by the Townshend Acts were widely used. In February 1768, the Assembly of Massachusetts Bay Colony issued a circular letter to the other colonies urging them to coordinate resistance. The governor dissolved the assembly when it refused to rescind the letter. Meanwhile, a riot broke out in Boston in June 1768 over the seizure of the sloop "Liberty", owned by John Hancock, for alleged smuggling. Customs officials were forced to flee, prompting the British to deploy troops to Boston. A Boston town meeting declared that no obedience was due to parliamentary laws and called for the convening of a convention. A convention assembled but only issued a mild protest before dissolving itself. In January 1769, Parliament responded to the unrest by reactivating the Treason Act 1543 which called for subjects outside the realm to face trials for treason in England. The governor of Massachusetts was instructed to collect evidence of said treason, and the threat caused widespread outrage, though it was not carried out.
On March 5, 1770, a large crowd gathered around a group of British soldiers on a Boston street. The crowd grew threatening, throwing snowballs, rocks, and debris at them. One soldier was clubbed and fell. There was no order to fire, but the soldiers panicked and fired into the crowd. They hit 11 people; three civilians died of wounds at the scene of the shooting, and two died shortly after. The event quickly came to be called the Boston Massacre. The soldiers were tried and acquitted (defended by John Adams), but the widespread descriptions soon began to turn colonial sentiment against the British. This accelerated the downward spiral in the relationship between Britain and the province of Massachusetts. A new ministry under Lord North came to power in 1770, and Parliament repealed most of the Townshend duties, except the tax on tea. This temporarily resolved the crisis, and the boycott of British goods largely ceased, with only the more radical patriots such as Samuel Adams continuing to agitate. In June 1772, American patriots, including John Brown, burned a British warship that had been vigorously enforcing unpopular trade regulations, in what became known as the "Gaspee" Affair. The affair was investigated for possible treason, but no action was taken.

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