Apollo program

The Apollo program was a series of human spaceflight missions undertaken by the United States, during the years 1961 – 1974, using the Apollo spacecraft and Saturn space launch vehicle. It was conducted by the National Aeronautics and Space Administration (NASA) and was devoted to the goal, expressed in a 1961 address to the U.S. Congress by U.S. President John F. Kennedy, of "... landing a man on the Moon and returning him safely to the Earth ..." within the decade of the 1960s. That goal was successfully achieved by the Apollo 11 mission in July 1969.

The program continued until 1975 with five subsequent Apollo missions which also landed astronauts on the Moon, the last in December 1972. In the six successful Apollo spaceflights, twelve men walked on the Moon. As of 2011, these are the only times that humans have landed on another celestial body.

Equipment that was originally produced for the Apollo program was used for the later Skylab program during 1973 – 1974 and the joint U.S.−Soviet mission (Apollo−Soyuz Test Project) in 1975. Therefore, those subsequent programs are thus often considered to be part of the Apollo program.

Despite the many successes, there were two major failures, the first of which resulted in the deaths of three astronauts, Virgil "Gus" Grissom, Ed White and Roger Chaffee, in the Apollo 1 launchpad fire. The second was an explosion on Apollo 13, in whose aftermath the deaths of three more astronauts were averted by the efforts of flight controllers, project engineers, and backup crew members.

The Apollo program was named after the Greek god of the sun.

Background
The Apollo program was originally conceived early in 1960, during the 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 the sun 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 United States 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 the 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:

"I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth. No single space project in this period will be more impressive to mankind, or more important in the long-range exploration of space; and none will be so difficult or expensive to accomplish."

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. Some NASA employees disbelieved whether Kennedy's ambitious goal could be met.

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:
 * Direct Ascent: A spacecraft would travel directly to the Moon, landing and returning as a unit. This plan would have required a very powerful booster, the planned Nova rocket.
 * Earth Orbit Rendezvous: Two Saturn V rockets would be launched, one carrying the spacecraft and one carrying a propulsion unit that would have enabled the spacecraft to escape Earth orbit. After a docking in Earth orbit, the spacecraft would have landed on the Moon as a unit.
 * Lunar Surface Rendezvous: Two spacecraft would be launched in succession. The first, an automated vehicle carrying propellants, would land on the Moon and would be followed some time later by the manned vehicle. Propellant would be transferred from the automated vehicle to the manned vehicle before the manned vehicle could return to Earth.
 * Lunar Orbit Rendezvous (LOR): One Saturn V would launch a spacecraft that was composed of modular parts. A command module would remain in orbit around the Moon, while a lunar module would descended to the Moon and then return to dock with the command module while still in lunar orbit. In contrast with the other plans, LOR required only a small part of the spacecraft to land on the Moon, thereby minimizing the mass to be launched from the Moon's surface for the return trip.

In early 1961, direct ascent was generally the mission mode in favor at NASA. Many engineers feared that a rendezvous, which had never been attempted in space, would be impossible 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: "Without NASA's adoption of this stubbornly held minority opinion in 1962, the United States may still have reached the Moon, but almost certainly it would not have been accomplished by the end of the 1960s, President Kennedy's target date."

Spacecraft
The Apollo spacecraft consisted of three main sections, plus two minor sections.

The Command Module (CM) was the part in which the astronauts spent most of their time, including launch and landing. It was the only part that returned to Earth after the mission. The Service Module (SM) housed the equipment needed by the astronauts, such as oxygen tanks, and the engine that would take the spacecraft into and out of lunar orbit. The combined Command and Service modules were called the CSM.

The Lunar Module (LM) (also known as Lunar Excursion Module, or LEM), was the part of the spacecraft that actually landed on the Moon. It was comprised of a descent stage and an ascent stage, the former serving as a launch platform for the latter when the lunar exploration party blasted off for lunar orbit where they would dock with the CSM prior to returning to Earth. To learn lunar landing techniques, astronauts practiced in the Lunar Landing Research Vehicle (LLRV), a flying vehicle that simulated (by means of a special, additional jet engine) the reduced gravity that the Lunar Module would actually fly in. The LLRV was later replaced by the 3 Lunar Landing Training Vehicles (LLTV) which were the primary training vehicles used by the astronauts.

The Launch Escape Tower (LET) would carry the Command Module clear of the launch vehicle, should it explode during launch, and the Spacecraft Lunar Module Adapter (SLA) was used to connect the spacecraft to the Launch Vehicle. In addition, on Apollos 9 - 17, it housed and protected the Lunar Module and on the ASTP flight, it housed the docking adapter.

Apollo missions and astronauts
The various Apollo missions and the astronauts that crewed the manned missions are listed in the table below:

Moon rocks
Some of the Apollo program lunar missions collected and returned to Earth with samples of rocks and other materials from the Moon. In total, 381.7 kg (841.5 lb) were collected, much of which is now stored at the Lunar Receiving Laboratory in Houston.

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 evolution 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 is composed almost exclusively of the mineral anorthosite, and is believed to be representative of the highland crust. A geochemical component called KREEP (an acronym for rocks with high abundances of potassium, rare earth elements, and phosphorus) 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.

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 impacts 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.

Apollo Applications
In the speech which initiated Apollo, Kennedy declared that no other program would have as great a long-range effect on America's ambitions in outer space. 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.

One plan involved using the Saturn IB to take the Command/Service Module (CSM) to a variety of low-Earth orbits for missions lasting up to 45 days. Some missions would involve the docking of two CSMs, and transfer of supplies. The Saturn V would be necessary to take it to polar orbit, or sun-synchronous orbit (neither of which has yet been achieved by any manned spacecraft), and even to the geosynchronous orbit of Syncom 3, a communications satellite not quite in geostationary orbit. This was the first functioning communications satellite at that now-common great distance from the Earth, and it was small enough to be carried through the hatch and taken back to Earth for study as to the effects of radiation on its electronic components in that environment over a period of years. A return to the Moon was also planned, this time to orbit for a longer time to map the surface with high-precision equipment. This mission would not include a landing.

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, whilst 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 an unnamed 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 1964/5 Grumman, the primary contractor for the Apollo LM systems, attempted to interest the USAF and Navy in a military version of CSM/LM configuration. The LM would have been equipped with a manipulator arm and projectile weapons to intercept and disable enemy satellites. The proposal was never fully developed and was abandoned in 1967. In the same time period, Grumman proposed using an Apollo spacecraft to send a mission to land on a Near-Earth asteroid. Only about half a dozen were known at the time, with close approaches occurring about every three or four years. NASA found the scheme too marginal to pursue.

End of the program and lasting influences
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 cancelled 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; the others became museum exhibits.

The next generation of NASA spacecraft, the Orion (Formerly the Crew Exploration Vehicle or CEV), which is to replace the Space Shuttle following its retirement in 2010, is influenced largely by the Apollo Program. The most notable difference is that the CEV will return to Earth on land, much like the Russian Soyuz spacecraft, rather than at sea as the Apollos did. Like Apollo, the CEV will fly a lunar orbit rendezvous mission profile, but unlike Apollo, the lander, known as the Lunar Surface Access Module, 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 the LSAM 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.

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.

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". These photographs have also motivated many people toward environmentalism and space colonization.

The cost of the entire program is estimated at $135 billion (2006 dollars) ($25.4 billion in 1969 dollars). The Apollo spacecraft cost $28 billion (2006 dollars) to develop: $17 billion for the command and service modules, and $11 billion for the Lunar Module. The Saturn I, IB and V launch vehicle development cost about $46 billion.

It appears that much of the original film and telemetry data is missing. For more information see Apollo program missing tapes.