The Apollo program was the successful conclusion of the U.S. effort to achieve, within the decade, the goal set by President John F. Kennedy on May 25, 1961, of landing a man on the Moon and returning him safely to Earth. It followed the Gemini manned-flight program conducted in 1966–67 to develop the necessary techniques of orbiting, docking, and extravehicular activity (EVA). The main elements of the Apollo project were the three-man Apollo spacecraft; the two-man Lunar Excursion Module (LEM), or Lunar Module (LM); and the Saturn family of rockets, consisting of the Saturn 1, the Saturn 1B, and the Saturn 5. These units made up the first manned, interplanetary transportation system. Using this system, astronauts landed on the Moon, where they explored and collected samples at six sites on the near side between July 1969 and the end of December 1972. The total cost of developing and operating the Apollo-Saturn transportation system in the lunar program was $25 billion.

Between October 1968, when the Apollo-Saturn transportation system underwent its first full space test, and July 1975, when it was used for the last time, the National Aeronautics and Space Administration (NASA) launched 15 manned Apollo-Saturn flights. Eleven of these were missions in the lunar landing program, including two test flights in low Earth orbit, two test flights in lunar orbit, six landings, and one circumlunar flight, during which the planned landing was aborted. During the testing period three fatalities occurred on the launchpad at the Kennedy Space Center, Florida, but none in actual flight.

After completion of the lunar landing program, four flights were carried out: three were missions that ferried astronauts to and from the Skylab experimental space station in 1973–74, and one was a joint flight with Soviet cosmonauts in the Apollo-Soyuz Test Project in 1975.

The Apollo Spacecraft

Developed from Mercury and Gemini technology, the Apollo spacecraft itself consisted of the combined Command and Service Module (CSM). It was 10.4 m (34 ft) long and 3 m (10 ft) in diameter at the blunt end. A major advance over earlier spacecraft was the inertial guidance system developed by the Massachusetts Institute of Technology.

The CSM was actually two modules. The crew rode in the Command Module (CM), which contained three couches and was pressurized with oxygen at 0.35 kg/cm2 (5 lb/in2). For reentry, the CM separated from the Service Module (SM); a heat shield protected it during reentry. During the first stage of the descent, the CM was stabilized by its own reaction control system. During the last stage it employed a drogue and three main parachutes.

Behind the CM was the SM, which housed the main engine, of 9,750-kg (21,500-lb) thrust; the reaction control system; fuel-cell batteries; oxygen and hydrogen tanks; and environmental control system. The main engine was used for course corrections and major changes in orbit, including the injection of the vehicle into lunar orbit and its escape from lunar orbit for return to Earth.

Manned Apollo Flights

The manned Apollo flights were preceded by testing, which began on May 28, 1964. Tragedy struck the program on Jan. 27, 1967, when fire erupted in the Apollo 1 Command Module while a crew was performing a flight simulation. Dense fumes from burning plastics fatally suffocated Col. Virgil I. ("Gus") Grissom, Lt. Col. Edward H. White II, and Navy Lt. Comdr. Roger B. Chaffee. Investigation revealed that the fire was caused by the electrical arcing of a short circuit in the cabin. The arcing ignited normally fire-resistant plastics, which became flammable in the pure oxygen atmosphere of the cabin.

On Oct. 11, 1968, Apollo 7, the first manned Apollo flight, was boosted by a Saturn 1B into low Earth orbit from the Kennedy Space Center. Aboard were Navy Capt. Walter M. Schirra, Jr., Air Force Maj. Donn F. Eisele, and Walter Cunningham, a civilian test pilot. During the 11-day mission the three crew members suffered from head colds, and friction over the work load developed with Mission Control at Houston. The Apollo CSM functioned with only minor problems. The flight demonstrated that the vehicle was spaceworthy for the duration of a lunar mission.

On the second manned Apollo-Saturn flight, Apollo 8, Col. Frank Borman, Lt. Col. William A. Anders, and Navy Capt. James A. Lovell flew ten orbits of the Moon on Dec. 24, 1968. The crew took turns reading aloud from the Book of Genesis, and their words were broadcast worldwide over the NASA communications network. The eight-day mission (Dec. 21–28) served as a reconnaissance for landing sites.

On Apollo 9 (Mar. 3–13, 1969), Col. James A. McDivitt, Col. David R. Scott, and a civilian pilot, Russell L. Schweickart, tested the Lunar Module in Earth orbit and practiced docking with it. The Lunar Module was then tested in lunar orbit on the Apollo 10 flight (May 18–26). Col. Thomas P. Stafford and Navy Comdr. Eugene A. Cernan piloted the Lunar Module to within 15,000 m (50,000 ft) of the lunar surface on May 22, while Navy Comdr. John W. Young remained in the orbiting Apollo CSM. Stafford and Cernan jettisoned the Lunar Module's descent stage and burned the ascent stage engine to rejoin the Apollo mother ship. An informal practice of using names to distinguish the Lunar Module from the Apollo when they were separated was begun during the Apollo 9 and 10 tests and was formalized during the landing missions. The Apollo 9 CSM was called Gumdrop and the LM, Spider; the Apollo 10 CSM was Charlie Brown and the LM, Snoopy.

First Lunar Landing

Launched July 16, 1969, Apollo 11 made the first manned lunar landing on July 20. As Lt. Col. Michael Collins orbited the Moon in the mother ship Columbia, Neil Armstrong and Col. Buzz Aldrin touched down on the basaltic regolith of Mare Tranquillitatis (Sea of Tranquillity) in the Lunar Module Eagle at 4:17:42 pm Eastern Daylight Time (EDT), with the historic report: "Houston, Tranquillity Base here. The Eagle has landed. " Armstrong was the first out: he stepped on the surface at 10:56 pm that day. Dropping the last meter from the ladder, he said: "That's one small step for [a] man, one giant leap for mankind " (NASA later reported that the word a had been lost in transmission).

On the Moon, Armstrong and Aldrin erected the American flag and set up scientific instruments, including a laser beam reflector, a seismometer that later transmitted evidence of a moonquake, and a sheet of aluminum foil to trap solar wind particles. The astronauts took soil and rock photographs and collected 24.32 kg (53.61 lb) of rock and dirt samples. Armstrong, the first out and the last back into the Lunar Module, spent 2 hours and 13 minutes outside. After Armstrong and Aldrin returned to Columbia in the ascent stage of the Eagle, Collins fired the Apollo main engine and at 12:56 am EDT on July 22 lifted the vessel out of lunar orbit for the return to Earth. The ascent stage of the Eagle was left in lunar orbit. The crew landed in the Pacific Ocean on July 24, 1969.

Scientific Exploration

Detailed scientific exploration began with the flight of Apollo 12, Nov. 14–24, 1969. Comdr. Pete Conrad, Jr., and Comdr. Alan L. Bean landed (on Nov. 19) in the Lunar Module Intrepid in Oceanus Procellarum (Ocean of Storms), while Comdr. Richard F. Gordon, Jr., cruised in orbit in the CSM Yankee Clipper. Conrad and Bean made two sorties of extravehicular activity (or EVA) on the surface, totaling 7 hours and 50 minutes. They unpacked the first Apollo Lunar Scientific Package (ALSEP), consisting of an array of scientific instruments, on the first EVA. On the second, they hiked almost a kilometer (a half mile) to inspect the Surveyor 3 spacecraft, and took 11 kg (25 lb) of its parts for analysis of the effect of the lunar environment on metal and glass. They brought back 33.9 kg (74.7 lb) of rocks and soil.

Two days after Apollo 13 was launched on Apr. 11, 1970, an oxygen tank exploded in the Service Module and crippled the vessel's power and life-support systems so badly that a planned landing in the Fra Mauro formation of the Moon was canceled. Navy Capt. James A. Lovell, Jr., and civilians Fred W. Haise, Jr., and John L. Swigert, Jr., used the descent engine of the LM Aquarius to accelerate the crippled CSM Odyssey around the Moon and back to Earth. Using Aquarius as a lifeboat, they returned to the vicinity of Earth, entered the Command Module, and landed it safely on April 17. Investigation showed that a thermostatically controlled switch had failed and allowed the oxygen tank to overheat.

Apollo 14 (Jan. 31–Feb. 9, 1971) reached the Fra Mauro uplands. Navy Capt. Alan B. Shepard, Jr., and Comdr. Edgar D. Mitchell landed in the LM Antares, while Maj. Stuart A. Roosa cruised overhead in the CSM Kitty Hawk. After deploying ALSEP instruments, including a second laser reflector, Shepard and Mitchell towed a rickshalike, two-wheeled cart containing tools and instruments to the edge of a crater. They collected 42.8 kg (94.3 lb) of rocks and soil and spent 9 hours and 9 minutes outside on two EVAs. Quarantining returned lunar astronauts at Houston for 14 days after their departure from the Moon was terminated after this mission.

Apollo 15 (July 26–Aug. 7, 1971) brought the first manned surface vehicle — the Lunar Rover — to the Moon. It was carried with its wheels folded, in the descent stage of the LM Falcon. While Maj. Alfred M. Worden orbited the Moon in the CSM Endeavor, Col. David R. Scott and Lt. Col. James B. Irwin landed the Falcon on the Apennine mountain front, near the Hadley Rille. They spent 18.5 hours roaming for more than 30 km (18.6 mi) on the surface in the Rover, setting up experiments, taking measurements, and collecting 77 kg (170 lb) of soil and rocks. A subsatellite containing instruments for measuring gamma- and X-radiation from the surface was deployed in lunar orbit for the first time by Worden.

The last two missions penetrated the lunar highlands. Apollo 16 (Apr. 16–27, 1972) was targeted for the Descartes highlands in the southern hemisphere. Navy Capt. John W. Young and Lt. Col. Charles M. Duke, Jr., landed on April 20 in the LM Casper, while Lt. Col. Thomas K. Mattingly II cruised in orbit in the CSM Orion. The explorers covered 27 km (16.8 mi) in their Rover and collected 95.6 kg (210.8 lb) of samples, in EVAs totaling 20 hours and 14 minutes.

Apollo 17 (Dec. 7–19, 1972) took the first geologist, Harrison H. Schmitt, to the Moon. He and Navy Capt. Eugene A. Cernan landed in the Taurus Mountains, near the Littrow crater, on December 11, in the LM Challenger. Comdr. Ronald E. Evans made observations from orbit in the CSM America. Cernan and Schmitt spent 22 hours outside and brought back 110 kg (242 lb) of rocks and soil cores, having traversed 35 km (22 mi) in their Rover. This was the final mission in the Apollo lunar landing program.


Bibliography: Cernan, Eugene, and Davis, Don, Last Man on the Moon (1999); Collins, Michael, Carrying the Fire (1975); Compton, W. D., A History of Apollo Lunar Exploration Missions (1990); Goldstein, S. H., Reaching for the Stars (1987); Lambright, W. Henry, Powering Apollo: James E. Webb of NASA (1995); Lovell, Jim, and Kluger, Jeffrey, Lost Moon (1994); Zimmerman, Robert, Genesis: The Story of Apollo 8 (1998).