Apollo

Flight Mode

One of the key technological decisions of the early Apollo program was the flight mode used to travel to the Moon and back. Early plans focused on direct ascent (DA) and Earth-orbit rendezvous (EOR). In DA a single vehicle would launch from Earth, travel to the Moon, land, take off again, and return to Earth. This mode had the advantage of simplicity but the disadvantage of requiring an enormous and expensive vehicle that could carry the fuel needed to make a soft landing on the Moon and relaunch from the lunar surface. As an alternative, National Aeronautics and Space Administration (NASA) rocket scientist Wernher von Braun advocated EOR, which involved separate launchings—two or more—of a propulsion stage and a piloted spacecraft into Earth orbit for assembly in orbit. The assembled vehicle would travel to the Moon, land, take off, and travel back to Earth. An advantage of EOR was that smaller rockets could be used to lift components and fuel into Earth orbit. It also would have provided the beginnings of a space station, which would be useful as part of a long-term strategy of exploration of space beyond the Moon. The United States was in a race, however, and the EOR process was inherently slow, given the multiple launches. It had the additional disadvantage of component parts that had to be brought together and assembled in space, a feat that had never been done before.

A third possible mode, lunar-orbit rendezvous (LOR), was championed by NASA engineer John Houbolt, but initially dismissed by most planners because it seemed even riskier. Failure would strand astronauts in orbit around the Moon. Perceived safety issues aside, however, LOR was an elegant solution because unneeded pieces of the spacecraft would be discarded along the way, reducing mass and fuel needs. A small, specially designed vehicle could make the descent to and launch from the lunar surface and rejoin a mother ship in lunar orbit for the trip back to Earth. Houbolt argued that LOR was even safer than EOR because the mass of the lander would be much smaller and there were no atmosphere or weather concerns in lunar orbit. The matter was effectively settled in June 1961, when von Braun recognized that LOR offered "the highest confidence factor of successful accomplishment within this decade." Lunar-orbit rendezvous was selected as the flight mode in early 1962.

Apollo Crews, Rockets, and Spacecraft

Apollo missions consisted of crews of three astronauts. Earth-orbiting Apollo missions were launched by Saturn 1B rockets, and the lunar missions were launched with the larger Saturn V rocket. Launches were made from the Kennedy Space Center at Cape Canaveral, Florida. The third and final stage of the Saturn V, the S-IVB, was jettisoned after propelling the spacecraft out of Earth orbit and toward the Moon. The Apollo spacecraft had three sections: the Command Module (CM), the Service Module (SM), and the Lunar Module (LM). The CM served as the crew's quarters as well as flight control. The SM contained propulsion and support systems. For most of the Earth-Moon trip, the CM and SM were linked and designated the Command-Service Module (CSM). After achieving lunar orbit, two crew members (the LM pilot and the commander) entered the LM, which transported them to the lunar surface and back and provided habitat and support while they were on the surface. The third crew member (the CM pilot) remained in the CSM, orbiting the Moon. When the LM launched from the Moon, it left behind its descent stage, which consisted of rockets and supports for a soft landing on the Moon. The ascent stage, essentially the crew cabin with small rockets, rejoined the CSM in lunar orbit (rendezvous). After the crew reentered the CSM, the LM was jettisoned to crash onto the Moon. The CSM made the return trip to Earth. Before entering Earth's atmosphere, the SM was also jettisoned. The CM with its occupants parachuted into the ocean to be retrieved by the U.S. Navy.

Before July 1969

The first launch of the Apollo program was designated AS-201 ("AS" standing for "Apollo-Saturn"), an unpiloted, suborbital flight of the Saturn booster on February 26, 1966. Unpiloted AS-203 followed on July 5 and AS-202 on August 25. AS-204 was scheduled to be the first piloted Apollo flight. During a preflight test on January 27, 1967, a fire broke out in the CM, killing astronauts Virgil I. Grissom, Edward H. White II, and Roger B. Chaffee. The fire resulted from a short in an electrical panel that ignited flammable materials in the 100-percent-oxygen atmosphere. NASA renamed the scheduled mission Apollo 1 and redesigned the CM. There were no flight missions designated Apollos 2 and 3. Apollo 4, an unpiloted mission launched on November 9, 1967, was the first flight involving all three stages of the Saturn V rocket. On January 22, 1968, the engines of the LM were test-fired in Earth orbit on the unpiloted Apollo 5. Apollo 6, launched on April 4, was another unpiloted test of the Saturn V and the first Apollo mission to carry a camera pointed toward Earth.

The first Apollo mission to take humans into space was Apollo 7, which launched on October 11, 1968. Astronauts Walter M. Schirra Jr., Donn F. Eisele, and R. Walter Cunningham tested the functionality and livability of the CSM for more than ten days while they orbited Earth 163 times. Although the LM was not flown on the mission, the astronauts assessed the capability of the CSM to rendezvous with the LM by separating from and reapproaching an orbiting S-IVB. Apollo 8, the first mission to bring humans to the vicinity of the Moon, was launched two months later on December 21. Astronauts Frank Borman, James A. Lovell Jr., and William A. Anders made ten orbits of the Moon and photographed prospective landing sites. They also provided some of the most memorable photos of Earth from space, including the famous photo of Earth rising over the lunar horizon.^* Apollo 8 astronauts provided live television broadcasts of their activities and views from space. Their reading from the Bible's Book of Genesis on Christmas Eve while in orbit around the Moon was heard by millions of people around the world.

Apollo 9 was launched on March 3, 1969, and orbited Earth for ten days with astronauts James A. McDivitt, David R. Scott, and Russell L. Schweickart. The mission was the first flight of an entire Apollo lunar payload and the first test of undocking and docking of the LM and CSM in space. Schweickart left the LM for a thirty-seven-minute extravehicular activity (EVA). In a dress rehearsal for the lunar landing, astronauts Eugene A. Cernan, John W. Young, and Thomas P. Stafford took Apollo 10 to the Moon and back on a mission lasting from May 18 to May 26, 1969. They tested LM-CSM undocking and docking and LM navigation in lunar orbit by taking the LM to within 14 kilometers (9 miles) of the lunar surface.

July 1969 and After

Apollo 11 was launched on July 16, 1969, with astronauts Neil A. Armstrong, Michael Collins, and Edwin E. "Buzz" Aldrin Jr. The LM Eagle made history by safely landing on the Moon's Mare Tranquillitatis four days later. Armstrong and Aldrin spent twenty-two hours on the lunar surface during which they did one EVA of two and a half hours, took photographs, and collected 22 kilograms (48.5 pounds) of rock and soil samples from around the LM.

Apollo 12 was launched four months later with crew members Charles "Pete" Conrad Jr., Richard F. Gordon Jr., and Alan L. Bean. On November 19, in one of the most impressive technical achievements of the cold war era, Conrad landed the LM Intrepid within walking distance, about 160 meters (525 feet), of the unpiloted Surveyor 3 spacecraft, which had landed in Oceanus Procellarum two and a half years earlier. In two EVAs of almost eight hours, and totaling about 1.5 kilometers (0.9 mile) of walking, Conrad and Bean deployed a package of surface experiments, retrieved parts from Surveyor 3, and collected 34 kilograms (75 pounds) of samples.

Apollo 13 (April 11-17, 1970), carrying Lovell (who had previously flown on Apollo 8), John L. Swigert Jr., and Fred W. Haise Jr., was intended to be the third lunar landing. About fifty-six hours into the mission and most of the way to the Moon, one of the two oxygen tanks exploded, causing the other one to also fail. The normal supply of electricity, light, and water to the CM was gone, with the craft about 300,000 kilometers (200,000 miles) from Earth. The lunar landing was aborted. Relying on power and oxygen from the LM, advice from Earth-based support experts, and their own ingenuity and stamina, the crew returned to Earth safely.

The near-tragedy delayed the program almost a year, but Apollo 14 was launched on January 31, 1971, with astronauts Alan Shepard (Mercury 3), Stuart A. Roosa, and Edgar D. Mitchell. In two EVAs totaling nearly nine and a half hours, Shepard and Mitchell deployed various instruments, walked about 3.5 kilometers (2.2 miles), and collected 42 kilograms (92.5 pounds) of samples from the Fra Mauro Formation, a deposit of ejecta from the Imbrium basin. The astronauts used a hand cart to transport tools and samples.

Apollo 15 (July 26 to August 7, 1971) brought Scott (Apollo 9) and James B. Irwin to the edge of Mare Imbrium at the base of the Apennine Mountains. The mission was the first to carry and deploy the lunar roving vehicle (LRV), a 210-kilogram (460-pound) electric car with four-wheel drive. The rover allowed the astronauts to travel much farther, 28 kilometers (17 miles), and collect more samples than on previous missions. In three EVAs the astronauts deployed scientific experiments and collected 77 kilograms (170 pounds) of samples. From orbit, CM pilot Alfred M. Worden operated spectrometers to detect X rays and gamma rays emitted from the Moon and a laser altimeter to measure topography.

Apollo 16 (April 16-27, 1972) went to the Central Highlands. Astronauts Young (Apollo 10) and Charles M. Duke Jr. used a second LRV to traverse 27 kilometers (17 miles) and collect 96 kilograms (212 pounds) of samples in three EVAs totaling twenty hours. In the CM, Thomas K. Mattingly II photographed the Moon and took measurements with various instruments.

Apollo 17 was launched on December 7, 1972. The crew consisted of Cernan (Apollo 10), Ronald E. Evans, and Harrison H. Schmitt, who was a geologist and the first scientist-astronaut. On three EVAs totaling twenty-two hours, Cernan and Schmitt used the LRV to traverse 30 kilometers (18.6 miles) in the Taurus-Littrow Valley of Mare Serenitatis and collect 110.5 kilograms (244 pounds) of samples. On December 13, 1972, Cernan climbed into the LM for the return trip, becoming the last person on the Moon. The political and technical ends achieved, the program, which cost about $20 billion, ran into budgetary reality.

After the lunar landings, Apollo spacecraft and crews were used in Earth orbit for three missions to the Skylab space station in 1973 and 1974 and the Apollo-Soyuz Test Project in 1975 (Apollo 18). In total, there were nine crewed missions to the Moon, each with three astronauts. Three astronauts (Lovell, Young, and Cernan) made the trip twice, so twenty-four humans made the trip to the Moon and back. Twelve of those astronauts landed and worked on the surface of the Moon.

SEE ALSO APOLLO 1 CREW (VOLUME 3); APOLLO LUNAR LANDING SITES (VOLUME 3); APOLLO-SOYUZ (VOLUME 3); ARMSTRONG, NEIL (VOLUME 3); ASTRONAUTS, TYPES OF (VOLUME 3); HISTORY OF HUMANS IN SPACE (VOLUME 3); HUMANS VERSUS ROBOTS (VOLUME 3); KENNEDY, JOHN F. (VOLUME 3); LUNAR ROVERS (VOLUME 3); NASA (volume 3); OXYGEN ATMOSPHERE IN SPACECRAFT (VOLUME 3); SCHMITT, HARRISON (VOLUME 3); SHEPARD, ALAN (VOLUME 3); SPACE CENTERS (VOLUME 3); SPACE SUITS (VOLUME 3); TOOLS, APOLLO LUNAR EXPLORATION (VOLUME 3); VEHICLE ASSEMBLY BUILDING (VOLUME 3); WHY HUMAN EXPLORATION? (volume 3); YOUNG, JOHN (VOLUME 3).

Randy L. Korotev

Bibliography

Brooks, Courtney G., James M. Grimwood, and Loyd S. Swenson Jr. Chariots for Apollo: A History of Manned Lunar Spacecraft. Washington, DC: National Aeronautics and Space Administration, 1979.

Chaikin, Andrew. A Man on the Moon: The Voyages of the Apollo Astronauts. New York:Penguin Books, 1994.

Cortright, Edgar M., ed. Apollo Expeditions to the Moon. Washington, DC: National Aeronautics and Space Administration, 1979.

Ertel, Ivan D., Roland W. Newkirk, and Courtney G. Brooks. The Apollo Spacecraft: A Chronology. Washington, DC: National Aeronautics and Space Administration, 1978.

Hansen, James R. Enchanted Rendezvous: John C. Houbolt and the Genesis of the Lunar-Orbit Rendezvous Concept. Washington, DC: National Aeronautics and Space Administration, 1995.

Heiken, Grant, David Vaniman, and Bevin M. French, eds. Lunar Sourcebook: A User's Guide to the Moon. Cambridge, UK: Cambridge University Press, 1991.

Launius, Roger D., and J. D. Hunley. An Annotated Bibliography of the Apollo Program. Washington, DC: National Aeronautics and Space Administration, 1994.

Murray, Charles, and Catherine Bly Cox. Apollo: The Race to the Moon. New York: Simon & Schuster, 1989.

Wilhelms, Donald E. To a Rocky Moon: A Geologist's History of Lunar Exploration. Tucson: University of Arizona Press, 1993.

Internet Resources

Brooks, Courtney G., James M. Grimwood, and Loyd S. Swenson Jr. Chariots for Apollo: A History of Manned Lunar Spacecraft. National Aeronautics and Space Administration. <http://www.hq.nasa.gov/office/pao/History/SP-4205/cover.html>.

Cortright, Edgar M., ed. Apollo Expeditions to the Moon. National Aeronautics and Space Administration. <http://www.hq.nasa.gov/office/pao/History/SP-350/cover.html>.

Ertel, Ivan D., Roland W. Newkirk, and Courtney G. Brooks. The Apollo Spacecraft: A Chronology. 1978. National Aeronautics and Space Administration. <http://www.hq.nasa.gov/office/pao/History/SP-4009/cover.htm>.

Hansen, James R. Enchanted Rendezvous: John C. Houbolt and the Genesis of the Lunar-Orbit Rendezvous Concept. 1995. National Aeronautics and Space Administration. <http://www.hq.nasa.gov/office/pao/History/monograph4/splash2.htm>.

Jones, Eric M. Apollo Lunar Surface Journal. 1995-2000. National Aeronautics and Space Administration. <http://www.hq.nasa.gov/office/pao/History/alsj/>.

Launius, Roger D., and J. D. Hunley. An Annotated Bibliography of the Apollo Program. National Aeronautics and Space Administration. <http://www.hq.nasa.gov/office/pao/History/Apollobib/cover.html>.