The Apollo Program was a human spaceflight program undertaken by NASA during the years 1961–1975 with the goal of conducting manned moon landing missions. In 1961, President John F. Kennedy announced a goal of landing a man on the moon by the end of the decade. It was accomplished on July 20, 1969 by the landing of astronauts Neil Armstrong and Buzz Aldrin, with Michael Collins orbiting above during the Apollo 11 mission. Five other Apollo missions also landed astronauts on the Moon, the last one in 1972. These six Apollo spaceflights are the only times humans have landed on another celestial body. The Apollo program, specifically the lunar landings, is often cited as the greatest technological achievement in human history.
Apollo was the third human spaceflight program undertaken by NASA, the space agency of the United States. It used Apollo spacecraft and Saturn launch vehicles, which were later used for the Skylab program and the joint American-Soviet Apollo-Soyuz Test Project. These later programs are thus often considered to be part of the overall Apollo program.
The goal of the program, to land on the moon and return, was accomplished with only two major setbacks. The first resulted in the deaths of three astronauts, Gus Grissom, Ed White and Roger Chaffee, in the Apollo 1 launchpad fire. The second was an in-space explosion on Apollo 13, which badly damaged the spacecraft on the moonward leg of its journey. The three astronauts aboard narrowly escaped with their lives, thanks to the efforts of flight controllers, project engineers, backup crew members and the skills of the astronauts themselves.
The program set major milestones in the history of human spaceflight. This program stands alone in sending manned missions beyond low Earth orbit. Apollo 8 was the first manned spacecraft to orbit another celestial body, while Apollo 17 marks the time of the last moonwalk and also the last manned mission beyond low Earth orbit. The major space exploration milestones leading up to the moon landing include:
The program spurred advances in many areas of technology peripheral to rocketry and manned spaceflight. These include major contributions in the fields of avionics, telecommunications, and computers. The program sparked interest in many fields of engineering, including pioneering work using statistical methods to study the reliability of complex systems made from component parts. The physical facilities and machines which were necessary components of the manned spaceflight program remain as landmarks of civil, mechanical, and electrical engineering. Many objects and artifacts from the program are on display at various locations throughout the world, notably at the Smithsonian's Air and Space Museums.
The Apollo program was originally conceived early in 1960, during the Dwight Eisenhower administration, as a follow-up to America's Mercury program. While the Mercury capsule could only support one astronaut on a limited earth orbital mission, the Apollo spacecraft was intended to be able to carry three astronauts on a circumlunar flight and perhaps even on a lunar landing. The program was named after the Greek god of light and music by NASA manager Abe Silverstein, who later said that "I was naming the spacecraft like I'd name my baby." While NASA went ahead with planning for Apollo, funding for the program was far from certain, particularly given Eisenhower's equivocal attitude to manned spaceflight. In November 1960, John F. Kennedy was elected President after a campaign that promised American superiority over the Soviet Union in the fields of space exploration and missile defense. Using space exploration as a symbol of national prestige, he warned of a "missile gap" between the two nations, pledging to make the U.S. not "first but, first and, first if, but first period." Despite Kennedy's rhetoric, he did not immediately come to a decision on the status of the Apollo program once he was elected President. He knew little about the technical details of the space program, and was put off by the massive financial commitment required by a manned moon landing. When NASA Administrator James Webb requested a thirty percent budget increase for his agency, Kennedy supported an acceleration of NASA's large booster program but deferred a decision on the broader issue.
On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first man to fly in space, reinforcing American fears about being left behind in a technological competition with the Soviet Union. At a meeting of the U.S. House Committee on Science and Astronautics held only one day after Gagarin's flight, many congressmen pledged their support for a crash program aimed at ensuring that America would catch up. Kennedy, however, was circumspect in his response to the news, refusing to make a commitment on America's response to the Soviets. On April 20 Kennedy sent a memo to Vice President Lyndon B. Johnson, asking Johnson to look into the status of America's space program, and into programs that could offer NASA the opportunity to catch up. Johnson responded on the following day, concluding that "we are neither making maximum effort nor achieving results necessary if this country is to reach a position of leadership." His memo concluded that a manned moon landing was far enough in the future to make it possible that the United States could achieve it first.
On May 25, 1961, Kennedy announced his support for the Apollo program as part of a special address to a joint session of Congress:
At the time of Kennedy's speech, only one American had flown in space — less than a month earlier — and NASA had not yet sent a man into orbit. Even some NASA employees doubted whether Kennedy's ambitious goal could be met.
Answering President Kennedy's challenge and landing men on the moon by the end of 1969 required the most sudden burst of technological creativity, and the largest commitment of resources ($25 billion), ever made by any nation in peacetime. At its peak, the Apollo program employed 400,000 people and required the support of over 20,000 industrial firms and universities.
Choosing a mission mode
Once Kennedy had defined a goal the Apollo mission planners were faced with the challenge of designing a set of flights that could meet this stated goal while minimizing risk to human life, cost, and demands on technology and astronaut skill. Four possible mission modes were considered:
In early 1961, direct ascent was generally the mission mode in favor at NASA. Many engineers feared that a rendezvous—let alone a docking—neither of which had been attempted even in Earth orbit, would be extremely difficult in lunar orbit. However, dissenters including John Houbolt at Langley Research Center emphasized the important weight reductions that were offered by the LOR approach. Throughout 1960 and 1961, Houbolt campaigned for the recognition of LOR as a valid and practical option. Bypassing the NASA hierarchy, he sent a series of memos and reports on the issue to Associate Administrator Robert Seamans; while acknowledging that he spoke "somewhat as a voice in the wilderness," Houbolt pleaded that LOR should not be discounted in studies of the question.
Seamans' establishment of the Golovin committee in July 1961 represented a turning point in NASA's mission mode decision. While the ad-hoc committee was intended to provide a recommendation on the boosters to be used in the Apollo program, it recognized that the mode decision was an important part of this question. The committee recommended in favor of a hybrid EOR-LOR mode, but its consideration of LOR — as well as Houbolt's ceaseless work — played an important role in publicizing the workability of the approach. In late 1961 and early 1962, members of NASA's Space Task Group at the Manned Spacecraft Center in Houston began to come around to support for LOR. The engineers at Marshall Space Flight Center took longer to become convinced of its merits, but their conversion was announced by Wernher von Braun at a briefing in June 1962. NASA's formal decision in favor of LOR was announced on July 11, 1962. Space historian James Hansen concludes that:
Additionally, the selection of the LOR method would be further validated when Apollo 13's service module was stricken while on a trajectory towards the moon. Without the secondary, independent life support system found in the Lunar module, the astronauts would have perished.
The decision in favor of lunar orbit rendezvous dictated the basic design of the Apollo spacecraft. It would consist of two main sections: the Command/Service Module (CSM), in which the crew would spend most of the mission, and the Lunar Module (LM), which would descend to and return from the lunar surface.
The command module (CM) was conical in shape, and was designed to carry three astronauts from launch into lunar orbit and back from the moon to splashdown. Equipment carried by the command module included reaction control engines, a docking tunnel, guidance and navigation systems and the Apollo Guidance Computer. Attached to the command module was the service module (SM), which housed the service propulsion system and its propellants, the fuel cell power system, four maneuvering thruster quads, the S-band antenna for communication with Mission Control, and storage tanks for water and air. On Apollo 15, 16 and 17 it also carried a scientific instrument package. The two sections of the spacecraft would remain attached until just prior to re-entry, at which point the service module would be discarded. Only the command module was provided with a heat shield that would allow it and its passengers to survive the intense heat of re-entry. After re-entry it would deploy parachutes that would slow its descent through the atmosphere, allowing a smooth splashdown in the ocean.
Under the leadership of Harrison Storms, North American Aviation won the contract to build the CSM for NASA. Relations between North American and NASA were strained during the Apollo program, particularly after the Apollo 1 fire during which three astronauts died. The cause of the accident was determined to be an electrical short in the wiring of the command module; while determination of responsibility for the accident was complex, the review board concluded that "deficiencies existed in Command Module design, workmanship and quality control."
The Lunar Module (LM) (also originally known as Lunar Excursion Module, or LEM), was designed solely to land on the moon, and to ascend from the lunar surface to the command module. It had a limited heat shield and was of a construction so lightweight that it would not have been able to fly in Earth gravity. It carried two crewmembers and consisted of two stages, a descent and an ascent stage. The descent stage incorporated compartments in which cargo such as the Apollo Lunar Surface Experiment Package and Lunar Rover could be carried.
The contract for design and construction of the lunar module was awarded to Grumman, and the project was overseen by Tom Kelly. There were also problems with the lunar module; due to delays in the test program, the LM became what was known as a "pacing item," meaning that it was in danger of delaying the schedule of the whole Apollo program. Due to these issues, the Apollo missions were rescheduled so that the first manned mission with the lunar module would be Apollo 9, rather than Apollo 8 as was originally planned.
When the team of engineers led by Wernher von Braun began planning for the Apollo program, it was not yet clear what sort of mission their rocket boosters would have to support. Direct ascent would require a booster, the planned Nova rocket, which could lift a very large payload. NASA's decision in favor of lunar orbit rendezvous re-oriented the work of Marshall Spaceflight Center towards the development of the Saturn 1B and Saturn V. While these were less powerful than the Nova would have been, the Saturn V was still much more powerful than any booster developed before—or since.
The Saturn V consisted of three stages and an Instrument Unit which contained the booster's guidance system. The first stage, the S-IC, consisted of five F-1 engines arranged in a cross pattern, which produced a total of 7.5 million pounds of thrust. They burned for only 2.5 minutes, accelerating the spacecraft to a speed of approximately 6000 miles per hour (2.68 km/s). During development, the F-1 engines were plagued by combustion instability—if the combustion of propellants was not uniform across the flame front of an engine, pressure waves could build which would cause the engine to destroy itself. The problem was solved in the end through trial and error, fine-tuning the engines through numerous tests so that even small charges set off inside the engine would not induce instability.
The second stage, the S-II, used five J-2 engines. They burned for approximately six minutes, taking the spacecraft to a speed of 15,300 miles per hour (6.84 km/s) and an altitude of about 115 miles (185 km). At this point the S-IVB third stage took over, putting the spacecraft into orbit. Its one J-2 engine was designed to be restarted in order to make the translunar injection burn.
The Saturn IB was an upgraded version of the earlier Saturn I. It consisted of a first stage made up of eight H-1 engines and a second S-IVB stage which was identical to the Saturn V's third stage. The Saturn IB had only 1.6 million pounds of thrust in its first stage—compared to 7.5 million pounds for the Saturn V—but was capable of putting a command and lunar module into earth orbit. It was used in Apollo test missions and in both the Skylab program and the Apollo-Soyuz Test Program. In 1973 a refitted S-IVB stage, launched by a Saturn V, became the Skylab space station.
In September 1967, the Manned Spacecraft Center in Houston, Texas, proposed a series of missions that would lead up to a manned lunar landing. Seven mission types were outlined, each testing a specific set of components and tasks; each previous step needed to be completed successfully before the next mission type could be undertaken. These were:
Later added to this were H missions, which were short duration stays on the Moon with two LEVAs ("moonwalks"). These were followed by the J missions, which were longer three day stays, with three LEVAs and the use of the lunar rover. Apollo 18 to 20 would have been J missions, as Apollo 15 to 17 were. In addition, a further group of flights — the I missions — were planned, which would have been long duration orbital missions using a Service Module bay loaded with scientific equipment. When it became obvious that later flights were being cancelled, such mission plans were brought into the J missions that were actually flown.
Preparations for the Apollo program began long before the manned Apollo missions were flown. Test flights of the Saturn I booster began in October 1961 and lasted until September 1964. Three further Saturn I launches carried boilerplate models of the Apollo command/service module. Two pad abort tests of the launch escape system took place in 1963 and 1965 at the White Sands Missile Range.
The only unmanned missions to officially include Apollo as part of their name rather than serial number were Apollo 4, Apollo 5 and Apollo 6. Apollo 4 was the first test flight of the Saturn V booster. Launched on November 9, 1967, Apollo 4 exemplified George Mueller's strategy of "all up" testing. Rather than being tested stage by stage, as most rockets were, the Saturn V would be flown for the first time as one unit. The mission was a highly successful one. Walter Cronkite covered the launch from a broadcast booth about 4 miles (6 km) from the launch site. The extreme noise and vibrations from the launch nearly shook the broadcast booth apart- ceiling tiles fell and windows shook. At one point, Cronkite was forced to dampen the booth's plate glass window to prevent it from shattering. This launch showed that additional protective measures were necessary to protect structures in the immediate vicinity. Future launches used a damping mechanism directly at the launchpad which proved effective in limiting the generated noise.
Apollo 6 was the last in the series of unmanned Apollo missions. It launched on April 4, 1968, and landed back on Earth almost ten hours later at 21:57:21 UTC.
On each manned mission there were three astronauts: a commander, a command module pilot (CMP), and a lunar module pilot (LMP). In the case of a moon landing the commander and the LMP descended to the Moon, while the CMP remained in lunar orbit.
Apollo 7, launched on October 11, 1968 was the first manned mission in the Apollo program. It was an eleven-day Earth-orbital mission intended to test the redesigned command module. It was the first manned launch of the Saturn IB launch vehicle, and the first three-man American space mission.
By the summer of 1968 it became clear to program managers that a fully functional LM would not be available for the Apollo 8 mission. Rather than perform a simple earth orbiting mission, they chose to send Apollo 8 around the moon during Christmas. The original idea for this switch was the brainchild of George Low. Although it has often been claimed that this change was made as a direct response to Soviet attempts to fly a piloted Zond spacecraft around the moon, there is no evidence that this was actually the case. NASA officials were aware of the Soviet Zond flights, but the timing of the Zond missions does not correspond well with the extensive written record from NASA about the Apollo 8 decision. It is relatively certain that the Apollo 8 decision was primarily based upon the LM schedule, rather than fear of the Soviets beating the Americans to the moon.
Between December 21, 1968 and May 18, 1969, NASA launched three Apollo missions (8, 9, and 10) using the Saturn V launch vehicle. Each mission had a crew of three astronauts, and the last two included Lunar Modules, but none of these were intended as Moon landing missions.
The next two flights (11 and 12) included successful Moon landings. The Apollo 13 mission was aborted before the landing attempt, but the crew returned safely to Earth. The four subsequent Apollo missions (14 through 17) included successful Moon landings. The last three of these were J-class missions that included the use of Lunar Rovers.
Apollo 17 launched December 7, 1972 and was the last Apollo mission to the moon. Mission commander Eugene Cernan was the last person to leave the Moon's surface. The crew returned safely to Earth on December 19, 1972.
Apollo applications program
Following the success of the Apollo program, both NASA and its major contractors investigated several post-lunar applications for the Apollo hardware. The "Apollo Extension Series", later called the "Apollo Applications Program", proposed up to thirty flights to earth orbit. Many of these would use the space that the lunar module took up in the Saturn rocket to carry scientific equipment.
Of all the plans, only two were implemented: the Skylab space station (May 1973 – February 1974), and the Apollo-Soyuz Test Project (July 1975). Skylab's fuselage was constructed from the second stage of a Saturn IB, and the station was equipped with the Apollo Telescope Mount, itself based on a lunar module. The station's three crews were ferried into orbit atop Saturn IBs, riding in CSMs; the station itself had been launched with a modified Saturn V. Skylab's last crew departed the station on February 8, 1974, while the station itself returned prematurely to Earth in 1979, by which time it had become the oldest operational Apollo component.
The Apollo-Soyuz Test Project involved a docking in Earth orbit between a CSM and a Soviet Soyuz spacecraft. The mission lasted from July 15 to July 24, 1975. Although the Soviet Union continued to operate the Soyuz and Salyut space vehicles, NASA's next manned mission would not be until STS-1 on April 12, 1981.
In general the rocks collected from the Moon are extremely old compared to rocks found on Earth, as measured by radiometric dating techniques. They range in age from about 3.2 billion years old for the basaltic samples derived from the lunar mare, to about 4.6 billion years for samples derived from the highlands crust. As such, they represent samples from a very early period in the development of the Solar System that is largely missing from Earth. One important rock found during the Apollo Program was the Genesis Rock, retrieved by astronauts James Irwin and David Scott during the Apollo 15 mission. This rock, called anorthosite, is composed almost exclusively of the calcium-rich feldspar mineral anorthite, and is believed to be representative of the highland crust. A geochemical component called KREEP was discovered that has no known terrestrial counterpart. Together, KREEP and the anorthositic samples have been used to infer that the outer portion of the Moon was once completely molten (see lunar magma ocean).
Almost all of the rocks show evidence for having been affected by impact processes. For instance, many samples appear to be pitted with micrometeoroid impact craters, something which is never seen on earth due to its thick atmosphere. Additionally, many show signs of being subjected to high pressure shock waves that are generated during impact events. Some of the returned samples are of impact melt, referring to materials that are melted in the vicinity of an impact crater. Finally, all samples returned from the Moon are highly brecciated as a result of being subjected to multiple impact events.
Analysis of composition of the lunar samples support the giant impact hypothesis, that the Moon was created through a "giant impact" of a large astronomical body with the Earth.
Program costs and cancellation
In March 1966, NASA told Congress the "run-out cost" of the Apollo program to put men on the moon would be an estimated $22.718 Billion for the 13-year program which eventually accomplished six successful missions between July 1969 and December 1972.
According to Steve Garber, the NASA History website curator, the final cost of project Apollo was between $20 and $25.4 billion in 1969 dollars (or approximately $135 billion in 2005 dollars).
The costs associated with the Apollo spacecraft and Saturn rockets amounted to about $83 billion [Apollo spacecraft: $28 billion (Command/Service Module: $17 billion; Lunar Module: $11-billion), Saturn I, Saturn IB, Saturn V launch vehicles: about $46 billion] in 2005 dollars.
Originally three additional lunar landing missions had been planned, as Apollo 18 through Apollo 20. In light of the drastically shrinking NASA budget and the decision not to produce a second batch of Saturn Vs, these missions were canceled to make funds available for the development of the Space Shuttle, and to make their Apollo spacecraft and Saturn V launch vehicles available to the Skylab program. Only one of the remaining Saturn Vs was actually used to launch the Skylab orbital laboratory in 1973; the others became museum exhibits at the John F. Kennedy Space Center in Cape Canaveral, Florida, George C. Marshall Space Center in Huntsville, Alabama, Michoud Assembly Facility in New Orleans, Louisiana, and Lyndon B. Johnson Space Center in Houston, Texas.
Scientific and engineering legacy
The Apollo program stimulated many areas of technology. The flight computer design used in both the lunar and command modules was, along with the Minuteman Missile System, the driving force behind early research into integrated circuits. The fuel cell developed for this program was the first practical fuel cell. Computer-controlled machining (CNC) was pioneered in fabricating Apollo structural components.
Influence on future human space exploration
Neil Armstrong, the commander of the first successful landing Apollo 11, is often asked by the press for his views on the future of spaceflight. In 2005, he said that a human voyage to Mars will be easier than the lunar challenge of the 1960s: "I suspect that even though the various questions are difficult and many, they are not as difficult and many as those we faced when we started the Apollo (space program) in 1961."
In a speech on January 14, 2004, President Bush announced a new Vision for Space Exploration, which included plans for the United States to return astronauts to the Moon no later than 2020 (with the first human landing -- Orion 15 -- currently planned for 2019). This mission would be a part of the Constellation program, NASA's program to create a new generation of spacecraft for human spaceflight.
Replacing the Space Shuttle following its retirement in 2010 will be the Orion crew capsule, which closely resembles the Apollo command module in its aerodynamic shape. NASA administrator Michael D. Griffin has described the capsule as "Apollo on steroids," and the New Scientist magazine reports that "some critics... say the whole Orion program is little more than a throwback to Apollo-era technology." In other respects, however—including its cockpit displays and its heatshield—Orion will be employing new technology. More closely based on Apollo designs is the upper stage of the Ares I, the launch vehicle designed to take Orion into orbit. It will be based on a J-2X engine, a redesigned version of the J-2 engine used in the Saturn family of boosters. In working on the J-2X, NASA engineers have visited museums, searched for Apollo-era documentation and consulted with engineers who worked on the Apollo program. "The mechanics of landing on the moon and getting off the moon to a large extent have been solved," said Constellation program manager Jeff Hanley. "That is the legacy that Apollo gave us."
Like Apollo, Orion will fly a lunar orbit rendezvous mission profile, but unlike Apollo, the lander, known as Altair, will be launched separately on the Ares V rocket, a rocket based on both Space Shuttle and Apollo technologies. Orion will be launched separately and will link up with Altair in low earth orbit like that of the Skylab program. Also, Orion, unlike Apollo, will remain unmanned in lunar orbit while the entire crew lands on the lunar surface, with the lunar polar regions in mind instead of the equatorial regions explored by Apollo. Constellation will also employ an Earth orbit rendezvous mission profile, which was dropped in favor of lunar orbit rendezvous in Apollo.
A world wide audience
Approximately one fifth of the population of the world watched the live transmission of the first Apollo moonwalk.
Psychological impact on the astronauts
Many astronauts and cosmonauts have commented on the profound effects that seeing Earth from space has had on them. One of the most important legacies of the Apollo program was the now-common, but not universal, view of Earth as a fragile, small planet, captured in the photographs taken by the astronauts during the lunar missions. The most famous of these photographs, taken by the Apollo 17 astronauts, is "The Blue Marble" (see image at right). These photographs have also motivated many people toward environmentalism.
There have been numerous documentary films covering the Apollo project and the space race including:
Published - July 2009
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