Apollo program



The Apollo program was the spaceflight effort that landed the first humans on Earth's Moon.

Conceived during the Presidency of Dwight D. Eisenhower and carried out by the National Aeronautics and Space Administration of the United States (NASA), Apollo began in earnest after President John F. Kennedy proposed the national goal of "landing a man on the Moon and returning him safely to the Earth" by the end of the 1960s in a May 25, 1961 address to Congress.[1] [2]

Kennedy's goal was accomplished with the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Lunar Module (LM) on the Moon on July 20, 1969 and walked on its surface while Michael Collins remained in lunar orbit in the command spacecraft, and all three landed safely on Earth on July 24. Five subsequent Apollo missions also landed astronauts on the Moon, the last in December 1972. In these six spaceflights, 12 men walked on the Moon. These are the only times humans have landed on another celestial body.[3]

Apollo ran from 1961 to 1972, following the Mercury and Gemini programs. It used Saturn family rockets as launch vehicles. Apollo / Saturn vehicles were also used for an Apollo Applications program which consisted of three Skylab space station missions in 1973–74, and a joint U.S.–Soviet mission in 1975.

Apollo was successful despite two major setbacks: the 1967 Apollo 1 cabin fire that killed the entire crew during a pre-launch test; and an in-flight failure on the 1970 Apollo 13 flight which disabled the command spacecraft's propulsion and life support, forcing the crew to use the LM as a "lifeboat" for these functions until they could return to Earth safely.

Apollo set major milestones in human spaceflight. It 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 marked the last moonwalk and the last manned mission beyond low Earth orbit. The program spurred advances in many areas of technology incidental to rocketry and manned spaceflight, including avionics, telecommunications, and computers. Apollo also sparked interest in many fields of engineering and left many physical facilities and machines developed for the program as landmarks. Its command modules and other objects and artifacts are displayed throughout the world, notably in the Smithsonian's Air and Space Museums in Washington, DC and at NASA's centers in Florida, Texas and Alabama. The Apollo 13 Command Module is housed at the Kansas Cosmosphere and Space Center in Hutchinson, Kansas.

Background
See also: Space RaceThe Apollo program was 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 to be able to carry three astronauts on a circumlunar flight and eventually to 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."[4] Dr. Silverstein recalls he chose the name after perusing a book of mythology at home one evening, early in 1960. He thought that the image of "Apollo riding his chariot across the Sun was appropriate to the grand scale of the proposed program."[5] While NASA went ahead with planning for Apollo, funding for the program was far from certain given Eisenhower's ambivalent attitude to manned spaceflight.[6] President Kennedy addresses Congress, 1961, proposing to put a man on the Moon before the end of the decadeIn 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."[7] Despite Kennedy's rhetoric, he did not immediately come to a decision on the status of the Apollo program once he became 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.[8] When Kennedy's newly-appointed NASA Administrator James Webb requested a 30 percent budget increase for his agency, Kennedy supported an acceleration of NASA's large booster program but deferred a decision on the broader issue.[9]

On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person 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 one day after Gagarin's flight, many congressmen pledged their support for a crash program aimed at ensuring that America would catch up.[10] Kennedy, however, was circumspect in his response to the news, refusing to make a commitment on America's response to the Soviets.[11]

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.[12] Johnson responded approximately one week later, concluding that "we are neither making maximum effort nor achieving results necessary if this country is to reach a position of leadership."[13] His memo concluded that a manned Moon landing was far enough in the future that it was likely the United States would achieve it first.[13]

On May 25, 1961, Kennedy announced his support for the Apollo program during 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.—[1] President Kennedy speaks at Rice University (17 min, 47 sec)At the time of Kennedy's proposal, only one American had flown in space—less than a month earlier—and NASA had not yet sent an astronaut into orbit. Even some NASA employees doubted whether Kennedy's ambitious goal could be met.[2] Kennedy even came close to agreeing to a joint US-USSR moon mission, to eliminate duplication of effort.<sup class="reference" id="cite_ref-13">[14]

Landing men on the Moon by the end of 1969 required the most sudden burst of technological creativity, and the largest commitment of resources ($24 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.<sup class="reference" id="cite_ref-14">[15] President Kennedy delivers a speech at Rice University on the American space program, September 12, 1962.It also required the conversion of the Space Task Group, which had been directing the nation's manned space program from NASA's Langley Research Center, into a new NASA center, the Manned Spacecraft Center (MSC), to be housed in a new facility built in Houston, Texas on land donated by Rice University. In September 1962, by which time two Project Mercury astronauts had orbited the Earth, and construction of the MSC facility was under way, Kennedy visited Rice to reiterate his challenge in a famous speech: But why, some say, the moon? Why choose this as our goal? And they may well ask, why climb the highest mountain? Why, 35 years ago, fly the Atlantic? ... We choose to go to the Moon. 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 we intend to win ...

Many years ago the great British explorer George Mallory, who was to die on Mount Everest, was asked why did he want to climb it. He said, "Because it is there." Well, space is there, and we're going to climb it, and the Moon and the planets are there, and new hopes for knowledge and peace are there. And, therefore, as we set sail we ask God's blessing on the most hazardous and dangerous and greatest adventure on which man has ever embarked.—<sup class="reference" id="cite_ref-Rice_Speech_15-0">[16] ==Choosing a mission mode== See also: Moon landingOnce Kennedy had defined a goal, the Apollo mission planners were faced with the challenge of designing a set of flights that could meet it while minimizing risk to human life, cost, and demands on technology and astronaut skill. Four possible mission modes were considered: Early Apollo configuration for Direct Ascent and Earth Orbit Rendezvous, 1961*Direct Ascent: A spacecraft would travel directly to the Moon as a unit, land, and return leaving its landing stage on the Moon. This plan would have required a more powerful launch vehicle, the planned Nova rocket. An early model of the pre-LOR concept, c. 1962.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 viable 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.<sup class="reference" id="cite_ref-16">[17]
 * Earth Orbit Rendezvous (EOR): Multiple rockets (up to 15 in some plans) would be launched, each carrying various parts of a Direct Ascent spacecraft and propulsion units 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 excursion module would descend to the Moon and then return to dock with the command ship 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.

Seamans' establishment of the Golovin committee in July 1961 represented a turning point in NASA's mission mode decision.<sup class="reference" id="cite_ref-hansen21_17-0">[18] 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 Langley Center (which was in process of transitioning to the newly formed Manned Spacecraft Center in Houston), began to come around to support for LOR.<sup class="reference" id="cite_ref-hansen24_18-0">[19] 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.<sup class="reference" id="cite_ref-19">[20]

The LOR method had the advantage of allowing the lander spacecraft to be used as a "life boat" in the event of a failure of the command ship. This happened on Apollo 13 when an oxygen tank failure left the command ship without electrical power. The Lunar Module provided propulsion, electrical power and life support to get the crew home safely.

Spacecraft
Apollo CSM-LM, compared to scale with the smaller Gemini and Mercury spacecraft. Their Saturn, Titan and Atlas launch vehicles are also compared, in a smaller scale.Main article: Apollo spacecraftPreliminary design studies of Apollo spacecraft began in 1960 as a three-man command module supported by one of several service modules providing propulsion and electrical power, sized for use in various possible missions, such as: shuttle service to a space station, a circumlunar flight, or return to Earth from a lunar landing. Once the Moon landing goal became official, detailed design began of the Command/Service Module (CSM), in which the crew would spend the entire direct-ascent mission and lift off from the lunar surface for the return trip. (An even larger, separate propulsion module would have been required for the lunar descent.)

The final choice of lunar orbit rendezvous changed the CSM's role to a translunar ferry used to take the crew and a new spacecraft, the Lunar Module (LM), which would take two men to the lunar surface and return them to the CSM.

As the program concept evolved, use of the term "module" changed from its true meaning of an interchangeable component of systems with multiple variants, to simply a component of the complete lunar landing system.

Command/Service Module
Apollo 15 CSM in lunar orbitThe Command Module (CM) was the crew cabin, surrounded by a conical re-entry heat shield, designed to carry three astronauts from launch to lunar orbit and back to an Earth ocean splashdown. As such, it was the only component of the Apollo spacecraft to survive without major configuration changes as the program evolved from the early Apollo study designs. 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 cylindrical Service Module (SM), which housed the service propulsion engine and its propellants, the fuel cell power system, four maneuvering thruster quads, a high-gain S-band antenna for communications between the Moon and Earth, and storage tanks for water and oxygen. On the last three lunar missions, it also carried a scientific instrument package. Because its configuration was chosen early before the selection of lunar orbit rendezvous, the service propulsion engine was sized to lift the CSM off of the Moon, and thus oversized to about twice the thrust required for translunar flight.

As used in the actual lunar program, the two modules remained attached throughout most of the flight to make a single ferry craft known as the Command/Service Module (CSM), which carried a separate lunar lander (only half as heavy as the CSM) to the Moon, and the astronauts home to Earth. Just before re-entry, the Service Module was discarded and only the Command Module re-entered the atmosphere, using its heat shield to survive the intense heat caused by air friction. After re-entry it deployed parachutes that slowed its descent, allowing a smooth splashdown in the ocean.

Under the leadership of Harrison Storms, North American Aviation won the contract to build the CSM, and also the second stage of the Saturn V launch vehicle for NASA. Relations between North American and NASA were strained during the winter of 1965-66 by delivery delays, quality shortfalls, and cost overruns in both components.<sup class="reference" id="cite_ref-20">[21] They were strained even more a year later when a cabin fire killed the crew of Apollo 1 during a ground test. The cause was determined to be an electrical short in the wiring of the Command Module; while the determination of responsibility for the accident was complex, the review board concluded that "deficiencies existed in Command Module design, workmanship and quality control."<sup class="reference" id="cite_ref-21">[22] This eventually led to the removal of Storms as Command Module program manager.<sup class="reference" id="cite_ref-22">[23]

Lunar Module
Apollo 16 LM on the MoonThe Lunar Module (LM) (originally known as the Lunar Excursion Module, or LEM), was designed to fly between lunar orbit and the surface, landing two astronauts on the Moon and taking them back to the Command Module. It had no aerodynamic heat shield and was of a construction so lightweight that it would not have been able to fly through the Earth's atmosphere. It consisted of two stages, a descent and an ascent stage. The descent stage contained compartments which carried cargo such as the Apollo Lunar Surface Experiment Package and Lunar Rover.

The contract for design and construction of the Lunar Module was awarded to Grumman Aircraft Engineering Corporation, 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 a "pacing item," meaning that it was in danger of delaying the schedule of the whole Apollo program.<sup class="reference" id="cite_ref-23">[24] The first manned LM was not ready for its planned Earth orbit test in December 1968, but the program was kept on schedule by cancelling a second manned Earth orbit LM flight.

Launch vehicles
When the team of engineers led by Wernher von Braun began planning for the Apollo program, it was not yet clear what mission their rockets would have to support. Direct ascent would require a more powerful launch vehicle, the planned Nova, which could carry a very large payload to the Moon. NASA's decision in favor of Lunar Orbit Rendezvous re-oriented the work of the Marshall Space Flight Center towards the development of the Saturn I, Saturn IB and Saturn V. While the Saturn V was less powerful than the Nova would have been, it was still much more powerful than any rocket developed before, or since. (The USSR N1 was approximately as powerful, but it was never successful.)

Saturn IB
A Saturn IB rocket launches Apollo 7, October 11, 1968.Main article: Saturn IBThe Saturn IB was an upgraded version of the earlier Saturn I rocket, which was used in early Apollo boilerplate launches. It consisted of: The Saturn IB was capable of putting a partially-fueled Command/Service Module, or a Lunar Module, into earth orbit.<sup class="reference" id="cite_ref-24">[25] It was used in five of the Apollo test missions including the first manned mission. It was also used in the manned missions for the Skylab program and the Apollo-Soyuz Test Project.
 * An S-IB first stage powered by eight H-1 engines burning RP-1 with LOX oxidizer, to produce 1,600,000 pounds-force (7,100 kN) of thrust;
 * An S-IVB-200 second stage, powered by one J-2 engine burning liquid hydrogen with LOX oxidizer, to produce 225,000 lbf (1,000 kN) of thrust; and
 * An Instrument Unit which contained the rocket's guidance system.

Saturn V
A Saturn V rocket launches Apollo 11 in 1969The Saturn V was a three-stage rocket consisting of: Three Saturn V vehicles launched on Earth orbital flights. Two of the three (Apollo 4 and 6) were unmanned tests of the command and service modules, and the third was a manned flight, Apollo 9, testing the lunar module. Nine Saturn Vs launched manned Apollo missions to the Moon, including Apollo 11. It was also used for the unmanned launch of Skylab.
 * An S-IC first stage, powered by five F-1 engines arranged in a cross pattern, burning RP-1 with LOX oxidizer to produce 7,500,000 lbf (33,000 kN) of thrust. They burned for 2.5 minutes, accelerating the spacecraft to a speed of approximately 6,000 miles per hour (2.68 km/s).<sup class="reference" id="cite_ref-25">[26]
 * An S-II second stage, powered by five of the J-2 engines used in the S-IVB. 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) .<sup class="reference" id="cite_ref-26">[27]
 * An S-IVB-500 third stage similar to the Saturn IB's second stage, with capability to restart the J-2 engine. The engine would burn for approximately two and a half minutes and shut down when a low-Earth parking orbit was achieved. After approximately two orbits to confirm the spacecraft was ready to commit to the lunar trip, the engine was restarted to make the translunar injection maneuver taking the spacecraft into an extremely high orbit where it would be captured by the Moon's gravity.<sup class="reference" id="cite_ref-27">[28]
 * An instrument unit with a guidance system similar to that used on the Saturn IB.

Missions
Far side of the Moon by Apollo 16Apollo launches ^ Saturn IB launches from AS-201 through ASTPSaturn V launches, 1967–1973 (Last: Skylab)=== Unmanned missions=== Apollo required more than six years of spacecraft and launch vehicle development and testing before the first manned missions could be flown. Test flights of the Saturn I launch vehicle 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. Three unmanned tests of Apollo components with the Saturn IB (Apollo-Saturn, or AS) were officially designated (in their chronological order of launch) as AS-201, AS-203, and AS-202.

The only unmanned missions to be publicly designated as "Apollo" followed by a sequence number were Apollo 4, Apollo 5 and Apollo 6.<sup class="reference" id="cite_ref-28">[29] The simple numbering was started at "4" to follow the three Apollo-Saturn IB flights, though all subsequent flights kept the "AS" designations: AS-204 and following for Saturn IB flights, and AS-501 and following for Saturn V flights.

Apollo 4 was the first unmanned test flight of the Saturn V launch vehicle, carrying a Command/Service Module (CSM). 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. 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.<sup class="reference" id="cite_ref-29">[30] 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. The mission was a highly successful one, demonstrating the capability of the Command Module's heat shield to survive a trans-lunar return reentry by using the Service Module engine to ram it into the atmosphere at higher than the usual earth-orbital reentry speed.

Apollo 5 was the first unmanned test flight of the Lunar Module (LM) in Earth orbit, launched on January 22, 1968, by a Saturn IB. The critical LM engines were successfully tested (though a computer programming error cut one test firing short), including an in-flight test of the second stage engine in "abort mode," in which the ascent engine is fired simultaneously with the jettison of the descent stage. This capability was made available, only to be used in the event of a critical problem on the Moon landing, such as running out of descent fuel, but was never needed.

Apollo 6 was the last unmanned Saturn V flight, launched on April 4, 1968. It carried a CSM and a Lunar Module Test Article near the mass of the Lunar Module for ballast. It was planned to achieve translunar injection, then after 5 minutes, use the Service Module engine to return the CM to Earth, thus demonstrating the Saturn V's ability to send the Apollo craft to the Moon, and a direct return-to-Earth abort capability. However, "pogo" vibrations caused premature shutdown of two second-stage engines, and failure of the third stage to re-light for the translunar injection. Instead, the Service Module engine was used as in Apollo 4 to raise the craft to a higher Earth orbit, and bring the CM back at a velocity midway between that of low Earth orbit and lunar return velocity. This mission was considered successful enough to launch men on the next Saturn V flight, since fixes for the vibration problem were identified.

Manned missions
Hasselblad camera used in the Apollo ProgramThe manned missions carried three astronauts, designated as Commander (CDR), Command Module Pilot (CMP), and Lunar Module Pilot (LMP). Besides exercising all crew command decisions, the Commander was the primary pilot of both spacecraft (when present) and was first to exit the LM on the surface of the Moon. The CMP functioned as navigator, usually performed the initial docking with the LM, and remained in the Command/Service Module when his companions flew the LM. The LMP functioned as engineering officer, monitoring the systems of both spacecraft. On a landing mission, he accompanied the Commander on the lunar surface. On the last flight, the LMP was a professional geologist, Dr. Harrison Schmitt.

Apollo 7, launched on October 11, 1968, was the first manned mission in the program. It was an 11-day Earth-orbital flight intended to test the Command Module, redesigned following the Apollo 1 fire. It was the first manned launch of the Saturn IB launch vehicle and the first three-man American space mission. Lunar Roving Vehicle used on Apollos 15–17Between December 21, 1968 and May 18, 1969, NASA planned to launch three manned test / practice missions using the Saturn V launch vehicle and the complete spacecraft including the LM. But by the summer of 1968 it became clear to program managers that a fully functional LM would not be available for the Apollo 8 launch. Rather than waste the Saturn V on another simple Earth-orbiting mission, they chose to send the crew planned to make the second orbital LM test in Apollo 9, to orbit the Moon in the CSM on Apollo 8 during Christmas. The original idea for this switch was the brainchild of George Low, Manager of the Apollo Spacecraft Program Office. 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 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. The Apollo 8 decision was primarily based upon the LM schedule, not fear of the Soviets beating the Americans to the Moon. Plaque left on the Moon by Apollo 17This was followed by the first orbital manned LM flight on Apollo 9 (with the original Apollo 8 crew), and the lunar "dress rehearsal" Apollo 10 which took the LM to within 50,000 feet (15 km) of the surface, but did not land. That's one small step for [a] man, one giant leap for mankind.

— Neil Armstrong before stepping on the Moon during Apollo 11 mission<sup class="reference" id="cite_ref-30">[31] 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, 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.

Astronauts
Forty-one astronauts were assigned to fly Apollo spacecraft; thirty-two of them were part of the Apollo program, with the rest not flying until the subsequent Skylab and Apollo-Soyuz programs. Twenty-four of the Apollo program astronauts left Earth’s orbit and flew around the Moon (Apollo 7 and Apollo 9 did not leave low Earth orbit).

Twelve of these astronauts walked on the Moon’s surface, and six of those drove a lunar rover on the Moon. While three astronauts flew to the Moon twice, none of them landed on the Moon more than once. The nine Apollo missions to the moon occurred between December of 1968 and December of 1972.

Apart from these twenty-four people who visited the Moon, no human being has gone beyond low Earth orbit. They have, therefore, been farther from the Earth than anyone else. They are also the only people to have directly viewed the far side of the Moon. The twelve who walked on the Moon are the only people ever to have set foot on an astronomical object other than the Earth. Of the twenty-four lunar astronauts taking part in the Moon missions, two went on to command a Skylab mission, one commanded Apollo-Soyuz, one flew as commander for shuttle approach and landing tests and two went on to command orbital shuttle missions. A total of twenty-four Apollo-era astronauts (as well as pre-Apollo astronaut John Glenn) flew the space shuttle.

Capsule Communicator
Mission rules specified that, in most circumstances, only one person in the Mission Control Center would communicate directly with the in-flight crew; this was to be another astronaut, who would be best able to understand the situation in the spacecraft and communicate with the crew in the clearest way. These individuals were designated Capsule Communicators or CAPCOMs, a term carried over from the Mercury and Gemini programs. They were usually chosen from the backup and support crews, and worked in shifts during long missions. The periodic beeps heard during communications with the astronauts are known as Quindar tones.

Samples returned
The Apollo program returned 841.5 lb (381.7 kg) of rocks and other material from the Moon, much of which is stored at the Lunar Receiving Laboratory in Houston. The only sources of Moon rocks on Earth are those collected from the Apollo program, the former Soviet Union's Luna missions, and lunar meteorites.

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.<sup class="reference" id="cite_ref-31">[32] 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 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 near 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.<sup class="reference" id="cite_ref-32">[33]

Program costs and cancellation
When President Kennedy first chartered the Moon landing program, a preliminary cost estimate of $7 billion was generated, but this proved an extremely unrealistic guess of what could not possibly be determined precisely, and James Webb used his administrator's judgement to change the estimate to $20 billion before giving it to Vice President Johnson.<sup class="reference" id="cite_ref-Butts_33-0">[34] Webb's estimate shocked many at the time, but ultimately proved to be reasonably accurate. The final cost of project Apollo was reported to Congress as $25.4 billion in 1973.<sup class="reference" id="cite_ref-34">[35] It took up the majority of NASA's budget while it was being developed. For example, in 1966 it accounted for about 60 percent of NASA's total $5.2 billion budget.<sup class="reference" id="cite_ref-35">[36]

In 2009, NASA held a symposium on project costs which presented an estimate of the Apollo program costs in 2005 dollars as roughly $170 billion. This included all research and development costs; the procurement of 15 Saturn V rockets, 16 Command/Service Modules, 12 Lunar Modules, plus program support and management costs; construction expenses for facilities and their upgrading, and costs for flight operations. This was based on a Congressional Budget Office report, A Budgetary Analysis of NASA’s New Vision for Space, September 2004.<sup class="reference" id="cite_ref-Butts_33-1">[34]

Canceled missions
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 on Merritt Island, 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.

Apollo Applications Program
Following the success of the Apollo program, both NASA and its major contractors investigated several post-lunar applications for Apollo hardware. The Apollo Extension Series, later called the Apollo Applications Program, proposed up to 30 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 and the Apollo–Soyuz Test Project.

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, and the station itself re-entered the atmosphere in 1979, by which time it had become the oldest operational Apollo-Saturn component.

The Apollo-Soyuz Test Project involved a docking in Earth orbit between a CSM and a Soviet Soyuz spacecraft from July 15 to July 24, 1975. NASA's next manned mission would not be until STS-1 in 1981.

Recent observations
“There the [Apollo 11] lunar module sits, parked just where it landed 40 years ago, as if it still really were 40 years ago and all the time since merely imaginary.” –The New York Times<sup class="reference" id="cite_ref-nyt_lro_lm_img_36-0">[37] In 2008, Japan Aerospace Exploration Agency's SELENE probe observed evidence of the halo surrounding the Apollo 15 lunar module blast crater while orbiting above the lunar surface.<sup class="reference" id="cite_ref-37">[38] In 2009, NASA's robotic Lunar Reconnaissance Orbiter, while orbiting 50 kilometres (31 mi) above the moon, photographed the remnants of the Apollo program left on the lunar surface, and photographed each site where manned Apollo flights landed.<sup class="reference" id="cite_ref-38">[39] <sup class="reference" id="cite_ref-39">[40]

In a November 16, 2009 editorial, The New York Times opined: [T]here’s something terribly wistful about these photographs of the Apollo landing sites. The detail is such that if Neil Armstrong were walking there now, we could make him out, make out his footsteps even, like the astronaut footpath clearly visible in the photos of the Apollo 14 site. Perhaps the wistfulness is caused by the sense of simple grandeur in those Apollo missions. Perhaps, too, it’s a reminder of the risk we all felt after the Eagle had landed — the possibility that it might be unable to lift off again and the astronauts would be stranded on the Moon. But it may also be that a photograph like this one is as close as we’re able to come to looking directly back into the human past.<sup class="reference" id="cite_ref-nyt_lro_lm_img_36-1">[37] Proposed future lunar landing missions, such as the Google Lunar X Prize, intend to record close-up images of the Apollo Lunar Modules and other artificial objects on the surface.<sup class="reference" id="cite_ref-40">[41]

Science and engineering
Further information: NASA spinoff technologiesThe Apollo program, specifically the lunar landings, has been called the greatest technological achievement in human history.<sup class="reference" id="cite_ref-41">[42] <sup class="reference" id="cite_ref-42">[43] The 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.

Cultural impact
"Everything that I ever knew - my life, my loved ones, the Navy - everything, the whole world was behind my thumb." –James Lovell"We went to explore the Moon, and in fact discovered the Earth." –Eugene CernanThe crew of Apollo 8, the first manned spacecraft to orbit the Moon, sent televised pictures of the Earth and the Moon back to Earth (left), and read from the creation story in the Biblical book of Genesis, on Christmas Eve, 1968, This was believed to be the most widely watched television broadcast until that time. The mission and Christmas provided an inspiring end to 1968, which had been a bad year for the U.S., marked by Vietnam War protests, race riots, and the assassinations of civil rights leader Martin Luther King and Senator Robert Kennedy.

An estimated one-fifth of the population of the world watched the live transmission of the first Apollo moonwalk.<sup class="reference" id="cite_ref-43">[44]

Although the dramatic accident of Apollo mission 13 was a well-known event, many people from around the world witnessed the magical return of the Apollo 13 crew members. However, the mission was not a very popular event during its launch, and TV rating was at its historical low for space mission launches. ABC was showing the Dick Cavett Show when Apollo 13 incident happened. That night Dick Cavett mentioned the mission on his show, saying how 3 million fewer viewers watched the launch compare to the last mission, and even more comparing to the first few missions. ABC switched from the talk show to a "Special Report on Apollo 13". Then the TV screen displayed a special message on the Apollo 13 spacecraft and its failure. As the disaster happens, TV viewers were interested in the space mission once again. Apollo 13 became headlines for every newspaper and TV programs.

One legacy of the Apollo program is the now-common view of Earth as a fragile, small planet, captured in photographs taken by the astronauts during the lunar missions. The most famous, taken by the Apollo 17 astronauts, is The Blue Marble (right). These photographs have also motivated some people toward environmentalism.<sup class="reference" id="cite_ref-44">[45]

Many astronauts and cosmonauts have commented on the profound effects that seeing Earth from space has had on them;<sup class="Template-Fact" style="white-space: nowrap;">[citation needed] the 24 astronauts who traveled to the Moon are the only humans to have observed Earth from beyond low Earth orbit, and have traveled farther from Earth than anyone else to date.

The program succeeded in accomplishing one of President Kennedy's goals, which was to take on the Soviet Union in the space race and beat it by accomplishing a singular and significant achievement and thereby showcase the superiority of the capitalistic, free-market system as represented by the US. The Economist noted, however, the irony that in order to achieve the goal the Apollo program was successful by organizing tremendous public resources within a vast, centralized bureaucracy under government direction.<sup class="reference" id="cite_ref-45">[46]

Apollo 11 broadcast data restoration project
As part of Apollo 11's 40th anniversary in 2009, NASA spearheaded an effort to digitally restore the existing videotapes of the mission's live televised moonwalk.<sup class="reference" id="cite_ref-46">[47] After an exhaustive three-year search for missing tapes of the original video of the Apollo 11 moonwalk, NASA concluded the data tapes had more than likely been accidentally erased.<sup class="reference" id="cite_ref-NPR_tapes_47-0">[48] We're all saddened that they're not there. We all wish we had 20-20 hindsight. I don't think anyone in the NASA organization did anything wrong, I think it slipped through the cracks, and nobody's happy about it.—Dick Nafzger, TV Specialist, NASA Goddard Space Flight Center<sup class="reference" id="cite_ref-NPR_tapes_47-1">[48] The Moon landing data was recorded by a special Apollo TV camera which recorded in a format incompatible with broadcast TV. This resulted in lunar footage that had to be converted for the live television broadcast and stored on magnetic telemetry tapes. During the following years, a magnetic tape shortage prompted NASA to remove massive numbers of magnetic tapes from the National Archives and Records Administration to be recorded over with newer satellite data. Stan Lebar, who designed and built the lunar camera at Westinghouse Electric Corporation, also worked with Nafzger to try to locate the missing tapes.<sup class="reference" id="cite_ref-NPR_tapes_47-2">[48] So I don't believe that the tapes exist today at all. It was a hard thing to accept. But there was just an overwhelming amount of evidence that led us to believe that they just don't exist anymore. And you have to accept reality.—Stan Lebar, Lunar Camera Designer, Westinghouse Electric Corporation<sup class="reference" id="cite_ref-NPR_tapes_47-3">[48] With a budget of $230,000, the surviving original lunar broadcast data from Apollo 11 was compiled by Nafzger and assigned to Lowry Digital for restoration. The video was processed to remove random noise and camera shake without destroying historical legitimacy.<sup class="reference" id="cite_ref-Moon_footage_restore_48-0">[49] The images were from tapes in Australia, the CBS News archive, and kinescope recordings made at Johnson Space Center. The restored video, remaining in black and white, contains conservative digital enhancements and did not include sound quality improvements.<sup class="reference" id="cite_ref-Moon_footage_restore_48-1">[49]

Documentaries
Numerous documentary films cover the Apollo program and the space race, including:
 * Moonwalk One (1970)
 * For All Mankind (1989)
 * Moon Shot (documentary commemorating 25 years since the landings) (1994)
 * From the Earth to the Moon (TV miniseries) (1998)
 * Moon from the BBC miniseries The Planets (1999)
 * Magnificent Desolation: Walking on the Moon 3D (2005)
 * In the Shadow of the Moon (2007)
 * When We Left Earth: The NASA Missions (miniseries) (2008)
 * James May on the Moon (documentary commemorating 40 years since the landings) (2009)
 * NASA's Story