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 to become the prime crew 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.
Apollo 14 had visited and sampled a ridge of material ejected by the impact that created the Mare Imbrium impact basin. Likewise, Apollo 15 had also sampled material in the region of Imbrium, visiting the basin's edge. Because the Apollo 14 and Apollo 15 landing sites were closely associated with the Imbrium basin, there was still the chance that different geologic processes were prevalent in areas of the lunar highlands far from Mare Imbrium. Scientist Dan Milton, studying photographs of the highlands from Lunar Orbiter photographs, saw an area in the Descartes region of the Moon with unusually high albedo that he theorized might be due to volcanic rock; his theory quickly gained wide support. Several members of the scientific community noted that the central lunar highlands resembled regions on Earth that were created by volcanism processes and hypothesized the same might be true on the Moon. They hoped scientific output from the Apollo 16 mission would provide an answer. Some scientists advocated for a landing near the large crater, Tycho, but its distance from the lunar equator and the fact that the Lunar Module would have to approach over very rough terrain ruled it out.
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.