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. US President John F. Kennedy announced this goal in 1961, and it was accomplished on July 20, 1969 by Neil Armstrong, and Buzz Aldrin, with Michael Collins in Moon orbit 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 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, as articulated by President Kennedy, was accomplished with only two major failures. The first failure 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 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.
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:
First, 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. John F. Kennedy
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 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.
We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too. John F. Kennedy
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:
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.
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 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.
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/sec) 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.
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. 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.
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 kept orbiting it.
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.
That's one small step for [a] man, one giant leap for mankind.| | |Neil Armstrong
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. It appears that much of the original film and telemetry data for the Apollo 11 mission is missing. For more information see Apollo program missing tapes.
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.
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 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.
|Apollo 11||22 kg|
|Apollo 12||34 kg|
|Apollo 14||43 kg|
|Apollo 15||77 kg|
|Apollo 16||95 kg|
|Apollo 17||111 kg|
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 led to the conclusion, reached in 1984, that the Moon was created through a "giant impact" of a large astronomical body with the Earth.
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.
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. and How Apollo Has Influenced Society
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."
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.
Approximately one fifth of the population of the world watched the live transmission of the first Apollo moonwalk.
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 .