Moon landing

Moon landing
Still frame from the video transmission of Neil Armstrong stepping onto the surface of the Moon at 02:56 UTC on 21 July 1969. An estimated 500 million people worldwide watched this event, the largest television audience for a live broadcast at that time.[1][2]
Location of all successful soft landings on the Moon to date. Dates are landing dates in UTC.

A moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both manned and unmanned (robotic) missions. The first human-made object to reach the surface of the Moon was the Soviet Union's Luna 2 mission on 13 September 1959.[3] The United States's Apollo 11 was the first manned mission to land on the Moon on 20 July 1969.[4] There have been six manned landings (between 1969 and 1972) and numerous unmanned landings.


Unmanned landings

Several nations have sent numerous spacecraft to the surface of the Moon. The Soviet Union performed the first moon landing in 1959 by destructively crashing the Luna 2 spacecraft at high speed onto the lunar surface, a feat duplicated in 1962 by the Americans with Ranger 4. During the time of the Cold War, such contests to be the first on the Moon with a particular capability was one of the most visible facets of the Space Race.

More recently other nations have crashed spacecraft on the surface of the Moon at speeds of around 5000 miles per hour, often at precise, planned locations. These have generally been end-of-life lunar orbiters that because of system degradations could no longer overcome perturbations from lunar mascons to maintain their orbit. Japan's lunar orbiter Hiten crash impacted the Moon's surface on 10 April 1993. The European Space Agency performed a controlled crash impact with their orbiter SMART-1 on 3 September 2006. India's Space Agency ISRO performed a controlled crash impact with its Moon Impact Probe (MIP) on 14 November 2008. The MIP was notable for being an ejected probe from the Indian Chandrayaan-1 lunar orbiter and for performing remote sensing experiments during its descent to the lunar surface. Radio contact with the Chadrayaan-1 has been lost and it will also crash on the lunar surface in late 2011 or early 2012. Most recently, the Chinese lunar orbiter Chang'e 1 executed a controlled crash onto the surface of the Moon on 1 March 2009.

Only eighteen spacecraft have used braking rockets to survive their moon landings and perform scientific operations on the lunar surface – six manned, a dozen unmanned, all launched by either the Soviets or the Americans between 1966 and 1976. The USSR accomplished the first soft landings and took the first pictures from the lunar surface with ruggedized camera packages on their Luna 9 and Luna 13 missions. The Americans followed with five unmanned Surveyor soft landings and six manned Apollo missions. After the American manned Apollo landings, the Soviet Union later achieved sample returns of lunar soil via the unmanned Luna 16, Luna 20 and Luna 24 Moon landings; their Luna 17 and Luna 21 were successful unmanned rover missions. Not included in this accounting is the Soviet Luna 23 mission, which successfully landed but whose scientific equipment then failed, or the American Surveyor 4, with whom all radio contact was lost only moments before a possible perfect automated soft landing.

Manned landings

A total of twelve men have landed on the Moon. This was accomplished with two US pilot-astronauts flying a Lunar Module on each of six NASA missions across a 41-month time span starting on 21 July 1969 UTC, with Neil Armstrong and Buzz Aldrin on Apollo 11 (with Armstrong being first to set foot on the surface), and ending on 14 December 1972 UTC with Gene Cernan and Jack Schmitt on Apollo 17 (with Cernan being the last to step off the lunar surface). All Apollo lunar missions had a third crew member who remained onboard the Command Module. The last three missions had a rover for increased mobility.

Scientific background

The primary concerns of any moon landing are the high velocities involved that arise from the effects of gravity. In order to go to any moon, a spacecraft must first leave the gravity well of the Earth. The only practical way of accomplishing this currently is with a rocket. Unlike other airborne vehicles such as balloons or jets, a rocket is the only known form of propulsion which can continue to increase its speed at high altitudes in the vacuum outside the Earth's atmosphere.

Upon approach of the target moon, a spacecraft will be drawn ever closer to its surface at increasing speeds due to gravity. There are three possible outcomes: a crash landing where no attempt is made to slow down and the spacecraft is totally destroyed upon impact; a hard landing where the impact speed is reduced to less than 100 miles/hour or so, survivable by ruggedized machines but not humans; and a soft landing where the spacecraft decelerates precisely enough to land safely on the surface with negligible speed at contact. The first three attempts by the Americans to perform a successful hard moon landing with a ruggedized seismometer package in 1962 all failed.[5] The Soviets first achieved the milestone of a hard lunar landing with a ruggedized camera in 1966, followed only months later by the first unmanned soft lunar landing by the Americans. The escape velocity of the target moon is roughly equivalent to the speed of a crash landing on its surface, and thus is the total velocity which must be shed from the target moon's gravitational attraction for a soft landing to occur. For Earth's Moon, this figure is 2.38 kilometres per second (1.48 mi/s).[6] Such a change in velocity (referred to as a delta-v) is usually provided by a landing rocket, which must be carried into space by the original launch vehicle as part of the overall spacecraft. An exception is the soft moon landing on Titan carried out by the Huygens probe in 2005. As the only moon with an atmosphere, landings on Titan may be accomplished by using atmospheric entry techniques that are generally lighter in weight than a rocket with equivalent capability.

The Soviets succeeded in making the first crash landing on the Moon in 1959.[7] Crash landings [8] may occur because of malfunctions in a spacecraft, or they can be deliberately arranged for vehicles which do not have an on board landing rocket. There have been many such moon crashes, often with their flight path controlled to impact at precise locations on the lunar surface. For example, during the Apollo program the S-IVB third stage of the Saturn V moon rocket as well as the spent ascent stage of the lunar module were deliberately crashed on the Moon several times to provide impacts registering as a moonquake on seismometers that had been left on the lunar surface. Such crashes were instrumental in mapping the internal structure of the Moon.

If a return to Earth is desired after a moon landing is accomplished, the escape velocities of the Moon and Earth must again be overcome for the spacecraft to come to rest on the surface of the Earth. Rockets must be used to leave the Moon and return to space. Upon reaching Earth, atmospheric entry techniques are used to absorb the kinetic energy of a returning spacecraft and reduce its speed for safe landing. These functions greatly complicate a moon landing mission and lead to many additional operational considerations. Any moon departure rocket must first be carried to the Moon's surface by a moon landing rocket, increasing the latter's required size. The moon departure rocket, larger moon landing rocket and any Earth atmosphere entry equipment such as heat shields and parachutes must in turn be lifted by the original launch vehicle, greatly increasing its size by a significant and almost prohibitive degree. This necessitates optimizing the sizing of stages in the launch vehicle as well as consideration of using space rendezvous between multiple spacecraft.

Political background

The intense and expensive effort devoted in the 1960s to achieving first an unmanned and then ultimately a manned moon landing can only be understood in the political context of its historical era. World War II with its 60 million dead, half Soviets, was fresh in the memory of all adults. In the 1940s, the war had introduced many new and deadly innovations including blitzkrieg-style surprise attacks used in the invasion of Poland and in the attack on Pearl Harbor; the V-2 rocket, a ballistic missile which killed thousands in attacks on London and Antwerp; and the atom bomb, which killed hundreds of thousands in the atomic bombings of Hiroshima and Nagasaki. In the 1950s, tensions mounted between the two ideologically opposed superpowers of the United States and the Soviet Union that had emerged as victors in the conflict, particularly after the development by both countries of the hydrogen bomb.

On 4 October 1957, the Soviet Union launched Sputnik 1 as the first artificial satellite to orbit the Earth and so initiated the Space Age. This unexpected event was a source of pride to the Soviets and shock to the Americans, who could now potentially be surprise attacked by nuclear-tipped Soviet rockets in under 30 minutes. Also, the steady beeping of the radio beacon aboard Sputnik 1 as it passed overhead every 96 minutes was widely viewed on both sides as effective propaganda to Third World countries demonstrating the technological superiority of the Soviet political system compared to the American one. This perception was reinforced by a string of subsequent rapid-fire Soviet space achievements. In 1959, the R-7 rocket was used to launch the first escape from Earth's gravity into a solar orbit, the first crash impact onto the surface of the Moon and the first photography of the never-before-seen far side of the Moon. These were the Luna 1, Luna 2 and Luna 3 spacecraft.

The American response to these Soviet achievements was to greatly accelerate previously existing military space and missile projects and to create a civilian space agency, NASA. Military efforts were initiated to develop and produce mass quantities of intercontinental ballistic missiles (ICBMs) that would bridge the so-called missile gap and enable a policy of deterrence to nuclear war with the Soviets known as Mutually Assured Destruction or MAD. These newly developed missiles were made available to civilians of NASA for various projects (which would have the added benefit of demonstrating the payload, guidance accuracy and reliabilities of American ICBMs to the Soviets). While NASA stressed peaceful and scientific uses for these rockets, their use in various lunar exploration efforts also had secondary goal of realistic, goal-oriented testing of the missiles themselves and development of associated infrastructure, just as the Soviets were doing with their R-7. The tight schedules and lofty goals selected by NASA for lunar exploration also had an undeniable element of generating counter-propaganda to show to other countries that American technological prowess was the equal and even superior to that of the Soviets.

Early Soviet unmanned lunar missions (1958–1966)

Luna 3 – transmitted first photos of the far side of the Moon

After the fall of the Soviet Union in 1991 historical records were released to allow the true accounting of Soviet lunar efforts. Unlike the American tradition of assigning a particular mission name in advance of launch, the Soviets assigned a public "Luna" mission number only if a launch resulted in a spacecraft going beyond Earth orbit. The policy had the effect of hiding Soviet Moon picture failures from public view. If the attempt failed in Earth orbit before departing for the Moon, it was frequently (but not always) given a "Sputnik" or "Cosmos" earth-orbit mission number to hide its purpose. Launch explosions were not acknowledged at all.

U.S.S.R. Mission Mass (kg) Launch vehicle Launched Mission goal Mission result
Semyorka – 8K72 23 September 1958 Lunar Impact Failure – booster malfunction at T+ 93 sec
Semyorka – 8K72 12 October 1958 Lunar Impact Failure – booster malfunction at T+ 104 sec
Semyorka – 8K72 4 December 1958 Lunar Impact Failure – booster malfunction at T+ 254 sec
Luna-1 361 Semyorka – 8K72 2 January 1959 Lunar Impact Partial success – first spacecraft to reach escape velocity, lunar flyby, solar orbit; Missed the Moon
Semyorka – 8K72 18 June 1959 Lunar Impact Failure – booster malfunction at T+ 153 sec
Luna-2 390 Semyorka – 8K72 12 September 1959 Lunar Impact Success – first lunar impact
Luna-3 270 Semyorka – 8K72 4 October 1959 Lunar Flyby Success – first photos of lunar far side
Semyorka – 8K72 15 April 1960 Lunar Flyby Failure – booster malfunction, failed to reach Earth orbit
Semyorka – 8K72 16 April 1960 Lunar Flyby Failure – booster malfunction at T+ 1 sec
Sputnik-25 Semyorka – 8K78 4 January 1963 Moon landing Failure – stranded in low Earth orbit
Semyorka – 8K78 3 February 1963 Moon landing Failure – booster malfunction at T+ 105 sec
Luna-4 1422 Semyorka – 8K78 2 April 1963 Moon landing Failure – lunar flyby at 5,000 miles (8,000 km)
Semyorka – 8K78 21 March 1964 Moon landing Failure – booster malfunction, failed to reach Earth orbit
Semyorka – 8K78 20 April 1964 Moon landing Failure – booster malfunction, failed to reach Earth orbit
Cosmos-60 Semyorka – 8K78 12 March 1965 Moon landing Failure – stranded in low Earth orbit
Semyorka – 8K78 10 April 1965 Moon landing Failure – booster malfunction, failed to reach Earth orbit
Luna-5 1475 Semyorka – 8K78 9 May 1965 Moon landing Failure – lunar impact
Luna-6 1440 Semyorka – 8K78 8 June 1965 Moon landing Failure – lunar flyby at 100,000 miles (160,000 km)
Luna-7 1504 Semyorka – 8K78 4 October 1965 Moon landing Failure – lunar impact
Luna-8 1550 Semyorka – 8K78 3 December 1965 Moon landing Failure – lunar impact during landing attempt

Early American unmanned lunar missions (1958–1965)

Artist's portrayal of a Ranger spacecraft right before impact
One of the last photos of the Moon transmitted by Ranger-8 right before impact

In contrast to Soviet lunar exploration triumphs in 1959, success eluded initial American efforts to reach the Moon with the Pioneer and Ranger programs. Fifteen consecutive U.S. unmanned lunar missions over a six year period from 1958 to 1964 all failed their primary photographic missions;[9][10] however, Rangers 4 and 6 successfully repeated the Soviet lunar impacts as part of their secondary missions.[11][12] Failures included three American attempts[5][11][13] in 1962 to hard land small seismometer packages released by the main Ranger spacecraft. These surface packages were to use retrorockets to survive landing, unlike the parent vehicle, which was designed to deliberately crash onto the surface. The final three Ranger probes performed successful high altitude lunar reconnaissance photography missions during intentional crash impacts between 2.62 and 2.68 kilometres per second (9,400 and 9,600 km/h) [14][15][16]

U.S. Mission Mass (kg) Launch vehicle Launched Mission goal Mission result
Pioneer 0 38 Thor-Able 17 August 1958 Lunar orbit Failure – first stage explosion; destroyed
Pioneer 1 34 Thor-Able 11 October 1958 Lunar orbit Failure – software error; reentry
Pioneer 2 39 Thor-Able 8 November 1958 Lunar orbit Failure – third stage misfire; reentry
Pioneer 3 6 Juno 6 December 1958 Lunar flyby Failure – first stage misfire, reentry
Pioneer 4 6 Juno 3 March 1959 Lunar flyby Partial success – first US craft to reach escape velocity, lunar flyby too far to shoot photos due to targeting error; solar orbit
Pioneer P-1 168 Atlas-Able 24 September 1959 Lunar orbit Failure – pad explosion; destroyed
Pioneer P-3 168 Atlas-Able 29 November 1959 Lunar orbit Failure – payload shroud; destroyed
Pioneer P-30 175 Atlas-Able 25 September 1960 Lunar orbit Failure – second stage anomaly; reentry
Pioneer P-31 175 Atlas-Able 15 December 1960 Lunar orbit Failure – first stage explosion; destroyed
Ranger 1 306 Atlas – Agena 23 August 1961 Prototype test Failure – upper stage anomaly; reentry
Ranger 2 304 Atlas – Agena 18 November 1961 Prototype test Failure – upper stage anomaly; reentry
Ranger 3 330 Atlas – Agena 26 January 1962 Moon Landing Failure – booster guidance; solar orbit
Ranger 4 331 Atlas – Agena 23 April 1962 Moon Landing Partial success – first U.S. spacecraft to reach another celestial body; crash impact – no photos returned
Ranger 5 342 Atlas – Agena 18 October 1962 Moon Landing Failure – spacecraft power; solar orbit
Ranger 6 367 Atlas – Agena 30 January 1964 Lunar impact Failure – spacecraft camera; crash impact
Ranger 7 367 Atlas – Agena 28 July 1964 Lunar impact Success – returned 4308 photos, crash impact
Ranger 8 367 Atlas – Agena 17 February 1965 Lunar impact Success – returned 7137 photos, crash impact
Ranger 9 367 Atlas – Agena 21 March 1965 Lunar impact Success – returned 5814 photos, crash impact

Pioneer missions

Three different designs of Pioneer lunar probes were flown on three different modified ICBMs. Those flown on the Thor booster modified with an Able upper stage carried an infrared image scanning television system with a resolution of 1 milliradian to study the Moon's surface, an ionization chamber to measure radiation in space, a diaphragm/microphone assembly to detect micrometeorites, a magnetometer, and temperature-variable resistors to monitor spacecraft internal thermal conditions. The first, a mission managed by the United States Air Force, exploded during launch; all subsequent Pioneer lunar flights had NASA as the lead management organization. The next two returned to Earth and burned up upon reentry into the atmosphere after achieved maximum altitudes of around 70,000 and 900 miles (1,400 km), far short of the roughly 250,000 miles (400,000 km) required to reach the vicinity of the Moon.

NASA then collaborated with the United States Army's Ballistic Missile Agency to fly two extremely small cone-shaped probes on the Juno ICBM, carrying only photocells which would be triggered by the light of the Moon and a lunar radiation environment experiment using a Geiger-Müller tube detector. The first of these reached an altitude of only around 64,000 miles (103,000 km), serendipitously gathering data that established the presence of the Van Allen radiation belts before reentering Earth's atmosphere. The second passed by the Moon at a distance of more than 37,000 miles (60,000 km), twice as far as planned and too far away to trigger either of the on-board scientific instruments, yet still becoming the first American spacecraft to reach a solar orbit.

The final Pioneer lunar probe design consisted of four "paddlewheel" solar panels extending from a one-meter diameter spherical spin-stabilized spacecraft body that was equipped to take images of the lunar surface with a television-like system, estimate the Moon's mass and topography of the poles, record the distribution and velocity of micrometeorites, study radiation, measure magnetic fields, detect low frequency electromagnetic waves in space and use a sophisticated integrated propulsion system for maneuvering and orbit insertion as well. None of the four spacecraft built in this series of probes survived launch on its Atlas ICBM outfitted with an Able upper stage.

Following the unsuccessful Atlas-Able Pioneer probes, NASA's Jet Propulsion Laboratory embarked upon an unmanned spacecraft development program whose modular design could be used to support both lunar and interplanetary exploration missions. The interplanetary versions were known as Mariners; lunar versions were Rangers. JPL envisioned three versions of the Ranger lunar probes: Block I prototypes, which would carry various radiation detectors in test flights to a very high Earth orbit that came nowhere near the Moon; Block II, which would try to accomplish the first Moon landing by hard landing a seismometer package; and Block III, which would crash onto the lunar surface without any braking rockets while taking very high resolution wide-area photographs of the Moon during their descent.

Ranger missions

The Ranger 1 and 2 Block I missions were virtually identical.[17][18] Spacecraft experiments included a Lyman-alpha telescope, a Rubidium-vapor magnetometer, electrostatic analyzers, medium-energy-range particle detectors, two triple coincidence telescopes, a cosmic-ray integrating ionization chamber, cosmic dust detectors, and scintillation counters. The goal was to place these Block I spacecraft in a very high Earth orbit with an apogee of 110,000 kilometres (68,000 mi) and a perigee of 60,000 kilometres (37,000 mi).[17] From that vantage point, scientists could make direct measurements of the magnetosphere over a period of many months while engineers perfected new methods to routinely track and communicate with spacecraft over such large distances. Such practice was deemed vital to be assured of capturing high-bandwidth television transmissions from the Moon during a one-shot fifteen minute time window in subsequent Block II and Block III lunar descents. Both Block I missions suffered failures of the new Agena upper stage and never left low earth parking orbit after launch; both burned up upon reentry after only a few days.

The first attempts to perform a Moon landing took place in 1962 during the Rangers 3, 4 and 5 missions flown by the United States.[5][11][13] All three Block II missions basic vehicles were 3.1 m high and consisted of a lunar capsule covered with a balsa wood impact-limiter, 650 mm in diameter, a mono-propellant mid-course motor, a retrorocket with a thrust of 5080 pound-force (22.6 kN),[11] and a gold- and chrome-plated hexagonal base 1.5 m in diameter. This lander (code-named Tonto) was designed to provide impact cushioning using an exterior blanket of crushable balsa wood and an interior filled with incompressible liquid freon. A 42 kg (56 pounds) 30-centimetre-diameter (0.98 ft) metal payload sphere floated and was free to rotate in a liquid freon reservoir contained in the landing sphere[citation needed]. This payload sphere contained six silver-cadmium batteries to power a fifty-milliwatt radio transmitter, a temperature sensitive voltage controlled oscillator to measure lunar surface temperatures, and a seismometer that was designed with sensitivity high enough to detect the impact of a five pound meteorite on the opposite side of the Moon. Weight was distributed in the payload sphere so it would rotate in its liquid blanket to place the seismometer into an upright and operational position no matter what the final resting orientation of the external landing sphere. After landing plugs were to be opened allowing the freon to evaporate and the payload sphere to settle into upright contact with the landing sphere. The batteries were sized to allow up to three months of operation for the payload sphere. Various mission constraints limited the landing site to Oceanus Procellarum on the lunar equator, which the lander ideally would reach 66 hours after launch.

No cameras were carried by the Ranger landers, and no pictures were to be captured from the lunar surface during the mission. Instead, the 3.1 metres (10 ft) Ranger Block II mother ship carried a 200-scan-line television camera which was to capture images during the free-fall descent to the lunar surface. The camera was designed to transmit a picture every 10 seconds.[11] Seconds before impact, at 5 and 0.6 kilometre (3.1 and 0.37 mi) above the lunar surface, the Ranger mother ships took picture (which may be viewed here. Other instruments gathering data before the mother ship crashed onto the Moon were a gamma ray spectrometer to measure overall lunar chemical composition and a radar altimeter. The radar altimeter was to give a signal ejecting the landing capsule and its solid-fueled braking rocket overboard from the Block II mother ship. The braking rocket was to slow and the landing sphere to a dead stop at 330 metres (1,080 ft) above the surface and separate, allowing the landing sphere to free fall once more and hit the surface[citation needed].

On Ranger 3, failure of the Atlas guidance system and a software error aboard the Agena upper stage combined to put the spacecraft on a course that would miss the Moon. Attempts to salvage lunar photography during a flyby of the Moon were thwarted by in-flight failure of the onboard flight computer. This was probably because of prior heat sterilization of the spacecraft by keeping it above the boiling point of water for 24 hours on the ground, to protect the Moon from being contaminated by Earth organisms. Heat sterilization was also blamed for subsequent in-flight failures of the spacecraft computer on Ranger 4 and the power subsystem on Ranger 5. Only Ranger 4 reached the Moon in an uncontrolled crash impact on the far side of the Moon.

Heat sterilization was discontinued for the final four Block III Ranger probes. These replaced the Block II landing capsule and its retrorocket with a heavier, more capable television system to support landing site selection for upcoming Apollo manned Moon landing missions. Six cameras were designed to take thousands of high-altitude photographs in the final twenty minute period before crashing on the lunar surface. Camera resolution was 1,132 scan lines, far higher than the 525 lines found in a typical American 1964 home television. While Ranger 6 suffered a failure of this camera system and returned no photographs despite an otherwise successful flight, the subsequent Ranger 7 mission to Mare Cognitum was a complete success. Breaking the six-year string of failures in American attempts to photograph the Moon at close range, the Ranger 7 mission was viewed as a national turning point and instrumental in allowing the key 1965 NASA budget appropriation to pass through the United States Congress intact without a reduction in funds for the Apollo manned Moon landing program. Subsequent successes with Ranger 8 and Ranger 9 further buoyed American hopes.

Soviet unmanned soft landings (1966–1976)

Luna 13 lander
Model of Luna 16 Moon soil sample return lander
Model of Soviet Lunokhod automatic moon rover
U.S.S.R. Mission Mass (kg) Booster Launched Mission goal Mission result Landing zone Lat/Lon
Luna-9 1580 Semyorka – 8K78 31 January 1966 Moon landing Success – first lunar soft landing, numerous photos Oceanus Procellarum 7.13°N 64.37°W
Luna-13 1580 Semyorka – 8K78 21 December 1966 Moon landing Success – second lunar soft landing, numerous photos Oceanus Procellarum 18°52'N 62°3'W
Proton 19 February 1969 Lunar rover Failure – booster malfunction, failed to reach Earth orbit
Proton 14 June 1969 Sample return Failure – booster malfunction, failed to reach Earth orbit
Luna-15 5,700 Proton 13 July 1969 Sample return Failure – lunar crash impact Mare Crisium unknown
Cosmos-300 Proton 23 September 1969 Sample return Failure – stranded in low Earth orbit
Cosmos-305 Proton 22 October 1969 Sample return Failure – stranded in low Earth orbit
Proton 6 February 1970 Sample return Failure – booster malfunction, failed to reach Earth orbit
Luna-16 5,600 Proton 12 September 1970 Sample return Success – returned 0.10 kg of Moon soil back to Earth Mare Fecunditatis 000.68S 056.30E
Luna-17 5,700 Proton 10 November 1970 Lunar rover SuccessLunokhod-1 rover traveled 10.5 km across lunar surface Mare Imbrium 038.28N 325.00E
Luna-18 5,750 Proton 2 September 1971 Sample return Failure – lunar crash impact Mare Fecunditatis 003.57N 056.50E
Luna-20 5,727 Proton 14 February 1972 Sample return Success – returned 0.05 kg of Moon soil back to Earth Mare Fecunditatis 003.57N 056.50E
Luna-21 5,950 Proton 8 January 1973 Lunar rover SuccessLunokhod-2 rover traveled 37.0 km across lunar surface LeMonnier Crater 025.85N 030.45E
Luna-23 5,800 Proton 28 October 1974 Sample return Failure – Moon landing achieved, but malfunction prevented sample return Mare Crisium 012.00N 062.00E
Proton 16 October 1975 Sample return Failure – booster malfunction, failed to reach Earth orbit
Luna-24 5,800 Proton 9 August 1976 Sample return Success – returned 0.17 kg of Moon soil back to Earth Mare Crisium 012.25N 062.20E

The Luna 9 spacecraft, launched by the Soviet Union, performed the first successful soft Moon landing on 3 February. Airbags protected its 99 kilograms (220 lb) ejectable capsule which survived an impact speed of over 15 metres per second (54 km/h).[19] Luna 13 duplicated this feat with a similar Moon landing on 24 December 1966. Both returned panoramic photographs that were the first views from the lunar surface.[20]

Luna 16 was the first robotic probe to land on the Moon and safely return a sample of lunar back to Earth.[21] It represented the first lunar sample return mission by the Soviet Union, and was the third lunar sample return mission overall, following the Apollo 11 and Apollo 12 missions. This mission was later successfully repeated by Luna 20 (1972) and Luna 24 (1976).

In 1970 and 1973 two Lunokhod ("Moonwalker") robotic lunar rovers were delivered to the Moon, where they successfully operated for 10 and 4 months respectively, covering 10.5 km (Lunokhod 1) and 37 km (Lunokhod 2). These rover missions were in operation concurrently with the Zond and Luna series of Moon flyby, orbiter and landing missions.

American unmanned soft landings (1966–1968)

Launch of Surveyor 1.
Pete Conrad, commander of Apollo 12, stands next to Surveyor 3 lander. In the background is the Apollo 12 lander, Intrepid.

The American robotic Surveyor program was part of an effort to locate a safe site on the Moon for a human landing and test under actual lunar conditions the radar and landing systems required to make a true controlled touchdown. Five of Surveyor's seven missions made successful unmanned Moon landings. Surveyor 3 was visited two years after its Moon landing by the crew of Apollo 12. They removed parts of it for examination back on Earth to determine the effects of long-term exposure to the lunar environment.

U.S. Mission Mass (kg) Booster Launched Mission goal Mission result Landing zone Lat/Lon
Surveyor 1 292 Atlas – Centaur 30 May 1966 Moon landing Success – 11,000 pictures returned, first American Moon landing Oceanus Procellarum 002.45S 043.22W
Surveyor 2 292 Atlas – Centaur 20 September 1966 Moon landing Failure – midcourse engine malfunction, placing vehicle in unrecoverable tumble; crashed southeast of Copernicus Crater Sinus Medii 004.00S 011.00W
Surveyor 3 302 Atlas – Centaur 20 April 1967 Moon landing Success – 6,000 pictures returned; trench dug to 17.5 cm depth after 18 hr of robot arm use Oceanus Procellarum 002.94S 336.66E
Surveyor 4 282 Atlas – Centaur 14 July 1967 Moon landing Failure – radio contact lost 2.5 minutes before touchdown; perfect automated Moon landing possible but actual outcome unknown Sinus Medii unknown
Surveyor 5 303 Atlas – Centaur 8 September 1967 Moon landing Success – 19,000 photos returned, first use of alpha scatter soil composition monitor Mare Tranquillitatis 001.41N 023.18E
Surveyor 6 300 Atlas – Centaur 7 November 1967 Moon landing Success – 30,000 photos returned, robot arm & alpha scatter science, engine restart, second landing 2.5 m away from first Sinus Medii 000.46N 358.63E
Surveyor 7 306 Atlas – Centaur 7 January 1968 Moon landing Success – 21,000 photos returned; robot arm & alpha scatter science; laser beams from Earth detected Tycho Crater 041.01S 348.59E

Transition from direct ascent landings to lunar orbit operations

Within four months of each other in early 1966 the Soviet Union and the United States had accomplished successful Moon landings with unmanned spacecraft. To the general public both countries had demonstrated roughly equal technical capabilities by returning photographic images from the surface of the Moon. These pictures provided a key affirmative answer to the crucial question of whether or not lunar soil would support upcoming manned landers with their much greater weight.

However, the Luna 9 hard landing of a ruggedized sphere using airbags at a 30-mile (48 km)-per-hour ballistic impact speed had much more in common with the failed 1962 Ranger landing attempts and their planned 100-mile (160 km)-per-hour impacts than with the Surveyor 1 soft landing on three footpads using its radar-controlled, adjustable-thrust retrorocket. While Luna 9 and Surveyor 1 were both major national accomplishments, only Surveyor 1 had reached its landing site employing key technologies that would be needed for a crewed flight. Thus as of mid-1966, the United States had begun to pull ahead of the Soviet Union in the so-called Space Race to land a man on the Moon.

A chart showing relative accomplishments with probes and human flights.

Advances in other areas were necessary before manned spacecraft could follow unmanned ones to the surface of the Moon. Of particular importance was developing the expertise to perform flight operations in lunar orbit. Ranger, Surveyor and initial Luna Moon landing attempts all utilized flight paths from Earth that traveled directly to the lunar surface without first placing the spacecraft in a lunar orbit. Such direct ascents use a minimum amount of fuel for unmanned spacecraft on a one-way trip.

In contrast, manned vehicles need additional fuel after a lunar landing to enable a return trip back to Earth for the crew. Leaving this massive amount of required Earth-return fuel in lunar orbit until it is actually used later in the mission is far more efficient than taking such fuel down to the lunar surface in a Moon landing and then hauling it all back into space yet again, working against lunar gravity both ways. Such considerations lead logically to a lunar orbit rendezvous mission profile for a manned Moon landing.

Accordingly, beginning in mid-1966 both the U.S. and U.S.S.R. naturally progressed into missions which featured lunar orbit operations as a necessary prerequisite to a manned Moon landing. The primary goals of these initial unmanned orbiters were extensive photographic mapping of the entire lunar surface for the selection of manned landing sites and, for the Soviets, the checkout of radio communications gear that would be used in future soft landings.

An unexpected major discovery from initial lunar orbiters were vast volumes of dense materials beneath the surface of the Moon's maria. Such mass concentrations ("mascons") can send a manned mission dangerously off course in the final minutes of a Moon landing when aiming for a relatively small landing zone that is smooth and safe. Mascons were also found over a longer period of time to greatly disturb the orbits of low-altitude satellites around the Moon, making their orbits unstable and forcing an inevitable crash on the lunar surface in the relatively short period of months to a few years. Thus all lunar orbiter satellites eventually become unintentional "lunar landers" at the end of their missions.

Controlling the location of impact for spent lunar orbiters can have scientific value. For example, in 1999 the NASA Lunar Prospector orbiter was deliberately targeted to impact a permanently shadowed area of Shoemaker Crater near the lunar south pole. It was hoped that energy from the impact would vaporize suspected shadowed ice deposits in the crater and liberate a water vapor plume that would be detectable from Earth. No such plume was observed. However, a small vial of ashes from the body of pioneer lunar scientist Eugene Shoemaker was delivered by the Lunar Prospector to the crater named in his honor – currently the only human remains on the Moon today.

Soviet lunar orbit satellites (1966–1974)

U.S.S.R Mission Mass (kg) Booster Launched Mission goal Mission result
Cosmos – 111 Molniya-M 1 March 1966 Lunar orbiter Failure – stranded in low Earth orbit
Luna-10 1,582 Molniya-M 31 March 1966 Lunar orbiter Success – 2,738 km x 2,088 km x 72 deg orbit, 178 m period, 60 day science mission
Luna-11 1,640 Molniya-M 24 August 1966 Lunar orbiter Success – 2,931 km x 1,898 km x 27 deg orbit, 178 m period, 38 day science mission
Luna-12 1,620 Molniya-M 22 October 1966 Lunar orbiter Success – 2,938 km x 1,871 km x 10 deg orbit, 205 m period, 89 day science mission
Cosmos-159 1,700 Molniya-M 17 May 1967 Prototype test Success – high Earth orbit manned landing communications gear radio calibration test
Molniya-M 7 February 1968 Lunar orbiter Failure – booster malfunction, failed to reach Earth orbit – attempted radio calibration test?
Luna-14 1,700 Molniya-M 7 April 1968 Lunar orbiter Success – 870 km x 160 km x 42 deg orbit, 160 m period, unstable orbit, radio calibration test?
Luna-19 5,700 Proton 28 September 1971 Lunar orbiter Success – 140 km x 140 km x 41 deg orbit, 121 m period, 388 day science mission
Luna-22 5,700 Proton 29 May 1974 Lunar orbiter Success – 222 km x 219 km x 19 deg orbit, 130 m period, 521 day science mission

Luna 10 became the first spacecraft to orbit the Moon on 3 April 1966.

American lunar orbit satellites (1966–1967)

U.S. Mission Mass (kg) Booster Launched Mission goal Mission result
Lunar Orbiter 1 386 Atlas – Agena 10 August 1966 Lunar orbiter Success – 1,160 km X 189 km x 12 deg orbit, 208 m period, 80 day photography mission
Lunar Orbiter 2 386 Atlas – Agena 6 November 1966 Lunar orbiter Success – 1,860 km X 52 km x 12 deg orbit, 208 m period, 339 day photography mission
Lunar Orbiter 3 386 Atlas – Agena 5 February 1967 Lunar orbiter Success – 1,860 km X 52 km x 21 deg orbit, 208 m period, 246 day photography mission
Lunar Orbiter 4 386 Atlas – Agena 4 May 1967 Lunar orbiter Success – 6,111 km X 2,706 km x 86 deg orbit, 721 m period, 180 day photography mission
Lunar Orbiter 5 386 Atlas – Agena 1 August 1967 Lunar orbiter Success – 6,023 km X 195 km x 85 deg orbit, 510 m period, 183 day photography mission

Soviet circumlunar loop flights (1967–1970)

Zond mounted on top stage of Proton booster in assembly hangar

It is possible to aim a spacecraft from Earth so that it will loop around the Moon and return to Earth without actually entering lunar orbit, following the so-called free return trajectory. Such circumlunar loop missions are simpler than actual lunar orbit missions because rockets for lunar orbit braking and Earth return are not required. However, a manned circumlunar loop trip poses significant challenges above and beyond those found in a manned low-Earth-orbit mission, offering valuable lessons in preparation for a manned Moon landing. Foremost among these are mastering the demands of re-entering the Earth's atmosphere upon returning from the Moon. Manned Earth-orbiting vehicles such as the Space Shuttle return to Earth from speeds of around 17,000 miles per hour (27,400 km/h, 7,600 m/s). Due to the effects of gravity, a vehicle returning from the Moon hits Earth's atmosphere at a much higher speed of around 25,000 miles per hour (40,200 km/h, 11,200 m/s). The g-loading on astronauts during the resulting deceleration can be at the limits of human endurance even during a nominal reentry. Slight variations in the vehicle flight path and reentry angle during a return from the Moon can easily result in fatal levels of deceleration force.

Achieving a manned circumlunar loop flight prior to a manned lunar landing became a primary goal of the Soviets with their Zond spacecraft program. The first three Zonds were unmanned planetary probes; after that, the Zond name was transferred to a completely separate manned program. The initial focus of these later Zonds was extensive testing of required high-speed reentry techniques. This focus was not shared by the Americans, who chose instead to bypass the stepping stone of a manned circumlunar loop mission and never developed a separate spacecraft for this purpose.

Initial manned spaceflights in the early 1960s placed a single person in low Earth orbit during the Soviet Vostok and American Mercury programs. A two-flight extension of the Vostok program known as Voskhod effectively used Vostok capsules with their ejection seats removed to achieve Soviet space firsts of multiple person crews in 1964 and spacewalks in early 1965. These capabilities were later demonstrated by the Americans in ten Gemini low Earth orbit missions throughout 1965 and 1966, using a totally new second-generation spacecraft design that had little in common with the earlier Mercury. These Gemini missions went on to prove critical techniques for orbital rendezvous and docking that were crucial to a manned lunar landing mission profile.

After the end of the Gemini program, the Soviets Union began flying their second-generation Zond manned spacecraft in 1967 with the ultimate goal of looping a cosmonaut around the Moon and returning him immediately to Earth. The Zond spacecraft was launched with the simpler and already operational Proton launch rocket, unlike the parallel Soviet manned Moon landing effort also underway at the time based on third-generation Soyuz spacecraft requiring development of the advanced N-1 booster. The Soviets thus believed they could achieve a manned Zond circumlunar flight years before an American manned lunar landing and so score a propaganda victory. However, significant development problems delayed the Zond program and the success of the American Apollo lunar landing program led to the eventual termination of the Zond effort.

Like Zond, Apollo Moon flights were generally launched on a free return trajectory that would return them to Earth via a circumlunar loop in the event that a Service Module malfunction failed to place them in lunar orbit as planned. This option was implemented after an explosion aboard the Apollo 13 mission in 1970, which is the only manned circumlunar loop mission flown to date.

U.S.S.R Mission Mass (kg) Booster Launched Mission goal Payload Mission result
Cosmos-146 5,400 Proton 10 March 1967 High Earth Orbit unmanned Partial success – Successfully reached high Earth orbit, but became stranded and was unable to initiate controlled high speed atmospheric reentry test
Cosmos-154 5,400 Proton 8 April 1967 High Earth Orbit unmanned Partial success – Successfully reached high Earth orbit, but became stranded and was unable to initiate controlled high speed atmospheric reentry test
Proton 28 September 1967 High Earth Orbit unmanned Failure – booster malfunction, failed to reach Earth orbit
Proton 22 November 1967 High Earth Orbit unmanned Failure – booster malfunction, failed to reach Earth orbit
Zond-4 5,140 Proton 2 March 1968 High Earth Orbit unmanned Partial success – launched successfully to 300,000 km high Earth orbit, high speed reentry test guidance malfunction, intentional self-destruct to prevent landfall outside Soviet Union
Proton 23 April 1968 Circumlunar Loop non-human biological payload Failure – booster malfunction, failed to reach Earth orbit; launch preparation tank explosion kills three in pad crew
Zond-5 5,375 Proton 15 September 1968 Circumlunar Loop non-human biological payload Success – looped around Moon, returned live biological payload safely to Earth despite landing off-target outside the Soviet Union in the Indian Ocean
Zond-6 5,375 Proton 10 November 1968 Circumlunar Loop non-human biological payload Partial success – looped around Moon, successful reentry, but loss of cabin air pressure caused biological payload death, parachute system malfunction and severe vehicle damage upon landing
Proton 20 January 1969 Circumlunar Loop non-human biological payload Failure – booster malfunction, failed to reach Earth orbit
Zond-7 5,979 Proton 8 August 1969 Circumlunar Loop non-human biological payload Success – looped around Moon, returned biological payload safely to Earth and landed on-target inside Soviet Union. Only Zond mission whose reentry G-forces would have been survivable by human crew had they been aboard.
Zond-8 5,375 Proton 20 October 1970 Circumlunar Loop non-human biological payload Success – looped around Moon, returned biological payload safely to Earth despite landing off-target outside Soviet Union in the Indian Ocean

Zond 5 was the first spacecraft to carry life from Earth to the vicinity of the Moon and return, initiating the final lap of the Space Race with its payload of turtles, insects, plants and bacteria. Despite the failure suffered in its final moments, the Zond 6 mission was reported by Soviet media as being a success as well. Although hailed worldwide as remarkable achievements, both of these Zond missions actually flew off-nominal reentry trajectories resulting in deceleration forces that would have been fatal to human crewmembers had they been aboard. As a result, the Soviets secretly planned to continue unmanned Zond tests until their reliability to support manned flight had been demonstrated. However, due to NASA's continuing problems with the lunar module, and because of CIA reports of a potential Soviet manned circumlunar flight in late 1968, NASA fatefully changed the flight plan of Apollo 8 from an Earth-orbit lunar module test to a lunar orbit mission scheduled for late December 1968.

In early December 1968 the launch window to the Moon opened for the Soviet launch site in Baikonur, giving the USSR their final chance to beat the US to the Moon. Cosmonauts went on alert and asked to fly the Zond spacecraft then in final countdown at Baikonour on the first manned trip to the Moon. Ultimately, however, the Soviet Politburo decided the risk of crew death was unacceptable given the combined poor performance to that point of Zond/Proton and so scrubbed the launch of a manned Soviet lunar mission. Their decision proved to be a wise one, since this unnumbered Zond mission was destroyed in another unmanned test when it was finally launched several weeks later.

By this time flights of the third generation American Apollo spacecraft had begun. Far more capable than the Zond, the Apollo spacecraft had the necessary rocket power to slip into and out of lunar orbit and to make course adjustments required for a safe reentry during the return to Earth. The Apollo 8 mission carried out the first manned trip to the Moon on 24 December 1968, certifying the Saturn V booster for manned use and flying not a circumlunar loop but instead a full ten orbits around the Moon before returning safely to Earth. Apollo 10 then performed a full dress rehearsal of a manned Moon landing in May 1969. This mission stopped short at ten miles (16 km) altitude above the lunar surface, performing necessary low-altitude mapping of trajectory-altering mascons using a factory prototype lunar module that was too overweight to allow a successful landing. With the failure of the unmanned Soviet sample return Moon landing attempt Luna 15 in July 1969, the stage was set for Apollo 11.

Manned Moon landings (1969–1972)

The U.S. Saturn V versus the Soviet N1.

American strategy

The U.S. Moon exploration program originated during the Eisenhower administration. In a series of mid-1950s articles in Collier's magazine, Wernher von Braun had popularized the idea of a manned expedition to the Moon to establish a lunar base. A manned Moon landing posed several daunting technical challenges to the U.S. and USSR. Besides guidance and weight management, atmospheric re-entry without ablative overheating was a major hurdle. After the Soviet Union's launch of Sputnik, von Braun promoted a plan for the United States Army to establish a military lunar outpost by 1965.

After the early Soviet successes, especially Yuri Gagarin's flight, U.S. President John F. Kennedy looked for an American project that would capture the public imagination. He asked Vice President Lyndon Johnson to make recommendations on a scientific endeavor that would prove U.S. world leadership. The proposals included non-space options such as massive irrigation projects to benefit the Third World. The Soviets, at the time, had more powerful rockets than the United States, which gave them an advantage in some kinds of space missions. Advances in U.S. nuclear weapons technology had led to smaller, lighter warheads, and consequently, rockets with smaller payload capacities. By comparison, Soviet nuclear weapons were much heavier, and the powerful R-7 rocket was developed to carry them. More modest potential missions such as flying around the Moon without landing or establishing a space lab in orbit (both were proposed by Kennedy to von Braun) were determined to offer too much advantage to the Soviets, since the U.S. would have to develop a heavy rocket to match the Soviets. A Moon landing, however, would capture world imagination while functioning as propaganda.

Apollo landing sites

Mindful that the Apollo Program would economically benefit most of the key states in the next election—particularly his home state of Texas because NASA's base was in Houston—Johnson championed the Apollo program. This superficially indicated action to alleviate the fictional "missile gap" between the U.S. and USSR, a campaign promise of Kennedy's in the 1960 election. The Apollo project allowed continued development of dual-use technology. Johnson also advised that for anything less than a lunar landing the USSR had a good chance of beating the U.S. For these reasons, Kennedy seized on Apollo as the ideal focus for American efforts in space. He ensured continuing funding, shielding space spending from the 1963 tax cut and diverting money from other NASA projects. This dismayed NASA's leader, James E. Webb, who urged support for other scientific work.

The Saturn V booster was the key to U.S. Moon landings. The Saturn had a perfect record of zero failures in thirteen launches.

Whatever he said in private, Kennedy needed a different message to gain public support to uphold what he was saying and his views. Later in 1963, Kennedy asked Vice President Johnson to investigate the possible technological and scientific benefits of a Moon mission. Johnson concluded that the benefits were limited, but, with the help of scientists at NASA, he put together a powerful case, citing possible medical breakthroughs and interesting pictures of Earth from space. For the program to succeed, its proponents would have to defeat criticism from politicians on the left, who wanted more money spent on social programs, and on those on the right, who favored a more military project. By emphasizing the scientific payoff and playing on fears of Soviet space dominance, Kennedy and Johnson managed to swing public opinion: by 1965, 58 percent of Americans favored Apollo, up from 33 percent two years earlier. After Johnson became President in 1963, his continuing defense of the program allowed it to succeed in 1969, as Kennedy had originally hoped.

Soviet strategy

Soviet leader Nikita Khrushchev did not relish "defeat" by any other power, but equally did not relish funding such an expensive project. In October 1963 he said that the USSR was "not at present planning flight by cosmonauts to the Moon," while insisting that the Soviets had not dropped out of the race. Only after another year would the USSR fully commit itself to a Moon-landing attempt, which ultimately failed.

At the same time, Kennedy had suggested various joint programs, including a possible Moon landing by Soviet and American astronauts and the development of better weather-monitoring satellites. Khrushchev, sensing an attempt by Kennedy to steal Russian space technology, rejected the idea: if the USSR went to the Moon, it would go alone. Korolyov, the RSA's chief designer, had started promoting his Soyuz craft and the N-1 launcher rocket that would have the capability of carrying out a manned Moon landing. Khrushchev directed Korolyov's design bureau to arrange further space firsts by modifying the existing Vostok technology, while a second team started building a completely new launcher and craft, the Proton booster and the Zond, for a manned cislunar flight in 1966. In 1964 the new Soviet leadership gave Korolyov the backing for a Moon landing effort and brought all manned projects under his direction. With Korolyov's death and the failure of the first Soyuz flight in 1967, the co-ordination of the Soviet Moon landing program quickly unraveled. The Soviets built a landing craft and selected cosmonauts for the mission that would have placed Aleksei Leonov on the Moon's surface, but with the successive launch failures of the N1 booster in 1969, plans for a manned landing suffered first delay and then cancellation.

Apollo missions

U.S. Mission Booster Crew Launched Mission goal Mission result
AS-201 (Apollo 1A) Saturn 1B Unmanned 26 February 1966 Suborbital Partial success – Unmanned suborbital flight was the first test flight of Saturn 1B and of the Apollo Command and Service Modules; problems included the failure of service module engine to fire for longer than 60 seconds and an electrical systems failure in the command module
AS-203 (Apollo 2) Saturn 1B Unmanned 5 July 1966 Earth orbit Success – fuel tank behaviour test and booster certification – informally known as Apollo 2
AS-202 (Apollo 3) Saturn 1B Unmanned 25 August 1966 Suborbital Success – command module reentry test successful, even though reentry was very uncontrolled – informally known as Apollo 3
AS-204 (Apollo 1) Saturn 1B Virgil I. "Gus" Grissom, Edward White, Roger B. Chaffee (Launch cancelled) Earth orbit Failure – never launched: command module destroyed and three astronauts killed on 27 January 1967 by fire in the module during a test exercise – Retroactively, the mission's name was officially changed to "Apollo 1" after the fire. Despite the fact that it was scheduled to be the fourth Apollo mission (and despite the fact that NASA planned to call the mission AS-204), the flight patch worn by the three astronauts, which was approved by NASA in June 1966, already referred to the mission as "Apollo 1"
Apollo 4 Saturn V Unmanned 9 November 1967 Earth orbit Success – first test of new booster and all elements together (except lunar module), successful reentry of command module
Apollo 5 Saturn 1B Unmanned 22 January 1968 Earth orbit Success – first flight of lunar module, multiple space tests of lunar module, no controlled reentry – used the Saturn 1B rocket original slated for the cancelled "Apollo 1" mission
Apollo 6 Saturn V Unmanned 4 April 1968 Earth orbit Partial success – severe oscillations during orbital insertion, several engines failing during flight, successful reentry of command module (though mission parameters for a 'worst case' reentry scenario could not be achieved)
Apollo 7 Saturn 1B Walter M. "Wally" Schirra, Donn Eisele, Walter Cunningham 11 October 1968 Earth orbit Success – eleven-day manned Earth orbit, command module testing (no lunar module), some minor crew issues
Apollo 8 Saturn V Frank Borman, Jim Lovell, William A. Anders 21 December 1968 Lunar orbit Success – ambitious mission profile (changed relatively shortly before launch), first human lunar orbit (no lunar module), first earthrise seen by men and major publicity success, some minor sleeping and illness issues
Apollo 9 Saturn V James McDivitt, David Scott, Russell L. "Rusty" Schweickart 3 March 1969 Earth orbit Success – ten-day manned Earth orbit, with EVA and successful manned flight / docking of lunar module
Apollo 10 Saturn V Thomas P. Stafford, John W. Young, Eugene Cernan 18 May 1969 Lunar orbit Success – second manned lunar orbit, test of lunar module in lunar orbit, coming as close as 8.4 nautical miles (15.6 km) to the Moon's surface
Apollo 11 Saturn V Neil Armstrong, Michael Collins, Edwin A. "Buzz" Aldrin 16 July 1969 Lunar landing Success – First manned landing, exploration on foot.
Apollo 12 Saturn V Charles "Pete" Conrad, Richard Gordon, Alan Bean 14 November 1969 Lunar landing Success – mission almost aborted in-flight after lightning strike on takeoff caused telemetry loss, successful landing within 200 meters of the Surveyor 3 probe
Apollo 13 Saturn V Jim Lovell, Jack Swigert, Fred Haise 11 April 1970 Lunar landing Successful failure[22] – problematic oscillations on start, unrelated explosion in service module during Earth-Moon transition caused mission to be aborted – crew took temporary refuge in lunar module and eventually returned to Earth with command module after single pass around Moon and made it through reentry.
Apollo 14 Saturn V Alan B. Shepard, Stuart Roosa, Edgar Mitchell 31 January 1971 Lunar landing Success – software and hardware problems with lunar module almost caused landing abort during lunar orbit, first color video images from the Moon, first materials science experiments in space
Apollo 15 Saturn V David Scott, Alfred Worden, James Irwin 26 July 1971 Lunar landing Success – first longer (3 days) stay on Moon, first use of lunar rover to travel total of 17.25 miles (27.76 km), more extensive geology investigations
Apollo 16 Saturn V John W. Young, Ken Mattingly, Charles Duke 16 April 1972 Lunar landing Success – malfunction in a backup yaw gimbal servo loop almost aborted landing (and reduced stay duration on Moon by one day to three for safety reasons), only mission to target lunar highlands
Apollo 17 Saturn V Eugene Cernan, Ronald Evans, Harrison H. "Jack" Schmitt 7 December 1972 Lunar landing Success – last (and still most recent) manned landing on the Moon, only mission with geologist
Skylab 1 Saturn V Unmanned 14 May 1973 Earth orbit Success – Launch of Skylab space station
Skylab 2 Saturn 1B Charles "Pete" Conrad, Paul Weitz, Joseph Kerwin 25 May 1973 Space station mission Success – Apollo spacecraft takes first US crew to Skylab, the first American space station, for a 28 day stay
Skylab 3 Saturn 1B Alan Bean, Jack Lousma, Owen Garriott 28 July 1973 Space Station mission Success – Apollo spacecraft takes second US crew to the Skylab space station for a 59 day stay
Skylab 4 Saturn 1B Gerald Carr, William Pogue, Edward Gibson 16 November 1973 Space station mission Success – Apollo spacecraft takes third US crew to the Skylab space station for an 84 day stay
ASTP (Apollo 18) Saturn 1B Thomas P. Stafford, Vance D. Brand, Donald K. "Deke" Slayton 15 July 1975 Earth orbit Success – Apollo-Soyuz Test Project, in which an Apollo space craft conducted rendezvous and docking exercises with Soviet Soyuz 19 in space – sometimes referred to as "Apollo 18"
Planned Apollo 18, Apollo 19, and Apollo 20 Moon Missions Saturn V Missions cancelled Never launched Lunar landings Cancelled – Several more missions (with detailed planning for up to Apollo 20) were cancelled

In total, twenty-four American astronauts have traveled to the Moon. Three have made the trip twice, and twelve have walked on its surface. Apollo 8 was a lunar-orbit-only mission, Apollo 10 included undocking and Descent Orbit Insertion (DOI), followed by LM staging to CSM redocking, while Apollo 13, originally scheduled as a landing, ended up as a lunar fly-by, by means of free return trajectory; thus, none of these missions made landings. Apollo 7 and Apollo 9 never left Earth orbit. Apart from the inherent dangers of manned Moon expeditions as seen with Apollo 13, one reason for their cessation according to astronaut Alan Bean is the cost it imposes in government subsidies.[23]

Manned Moon landings

Mission Name Lunar Lander Lunar landing date Lunar blastoff date Lunar landing site Duration on lunar surface Crew Number of EVAs Total EVA Time
Apollo 11 Eagle 20 July 1969 21 July 1969 Sea of Tranquility 21:31 Neil Armstrong, Edwin "Buzz" Aldrin 1 2:31
Apollo 12 Intrepid 19 November 1969 21 November 1969 Ocean of Storms 1 day, 7:31 Charles "Pete" Conrad, Alan Bean 2 7:45
Apollo 14 Antares 5 February 1971 6 February 1971 Fra Mauro 1 day, 9:30 Alan B. Shepard, Edgar Mitchell 2 9:21
Apollo 15 Falcon 30 July 1971 3 August 1971 Hadley Rille 2 days, 18:55 David Scott, James Irwin 3 18:33
Apollo 16 Orion 21 April 1972 24 April 1972 Descartes Highlands 2 days, 23:02 John Young, Charles Duke 3 20:14
Apollo 17 Challenger 11 December 1972 14 December 1972 Taurus-Littrow 3 days, 2:59 Eugene Cernan, Harrison H. "Jack" Schmitt 3 22:04

Other aspects of the Apollo Moon landings

Unlike other international rivalries, the Space Race has remained unaffected in a direct way regarding the desire for territorial expansion. After the successful landings on the Moon, the U.S. explicitly disclaimed the right to ownership of any part of the Moon.

President Richard Nixon had speechwriter William Safire prepare a condolence speech for delivery in the event that Armstrong and Aldrin became marooned on the Moon's surface and could not be rescued.[24]

In the 1940s writer Arthur C. Clarke forecast that man would reach the Moon by 2000.

On 16 August 2006, the Associated Press reported that NASA is missing the original Slow-scan television tapes (which were made before the scan conversion for conventional TV) of the Apollo 11 Moon walk. Some news outlets have mistakenly reported that the SSTV tapes were found in Western Australia, but those tapes were only recordings of data from the Apollo 11 Early Apollo Surface Experiments Package.[25]

20th–21st century unmanned crash landings

Hiten (Japan)

At the end of its mission, the Japanese lunar orbiter Hiten was commanded to crash into the lunar surface and did so on 10 April 1993 at 18:03:25.7 UT (11 April 03:03:25.7 JST).[26]


At the end of its mission, the ESA lunar orbiter SMART-1 performed a controlled crash into the Moon, at about 2 km/sec. The time of the crash was 3 September 2006, at 5:42 UT.[27]

Chandrayaan-1 (India)

Chandrayaan-1 was India's first unmanned lunar probe. It was launched by the Indian Space Research Organisation (ISRO) in October 2008, and operated until August 2009.[28] The mission, including a lunar orbiter and an impactor, was launched by a modified version of the PSLV, PSLV C11 on 22 October 2008 from Satish Dhawan Space Centre, Sriharikota, Nellore District, Andhra Pradesh, about 80 km north of Chennai, at 06:22 IST (00:52 UTC). The mission was a major boost to India's space program, as India researched and developed its own technology in order to explore the Moon. The vehicle was successfully inserted into lunar orbit on 8 November 2008, and the impactor, the Moon Impact Probe, impacted near Shackleton Crater at the south pole of the lunar surface at 14 November 2008, 20:31 IST.[29] The estimated cost for the project was 3.86 billion Indian rupees (US$80 million).

Weighing 34 kilograms, the box shaped impactor carried three instruments—a video imaging system, a mass spectrometer and a radar altimeter. The video imaging system took pictures of the Moon’s surface from high altitudes, relaying those pictures back to Earth during the descent. The mass spectrometer made measurements of the extremely thin lunar atmosphere. The radar altimeter measured the rate of descent of the probe to the lunar surface, testing that technology for future soft landing missions. The probe did not include braking rockets and was destroyed upon impacting the lunar surface at its planned speed of 5,000 kilometres per hour (3,100 mph).[30]

The orbiter completed 3,000 orbits acquiring 70,000 images of the lunar surface.[31][32] They were first transmitted to Indian Deep Space Network at Byalalu near Bangalore, and then to the Indian Space Research Organisation Telemetry, Tracking and Command Network at Bangalore. ISRO claims that the landing sites of the Apollo Moon missions have been mapped by the orbiter using multiple payloads. Six of the sites have been mapped including that of Apollo 11, the first mission that brought humans on the Moon.[33]

The Moon Mineralogy Mapper instrument, provided by NASA, confirmed the presence of water on the Moon.[34][35] This was also confirmed by the mass spectrometer on the MIP.[36]

Chang'e 1 (China)

The Chinese lunar orbiter Chang'e 1 executed a controlled crash onto the surface of the Moon on 1 March 2009, 2044 GMT, after a 16-month mission.[37]

US orbital missions since 2009

The most recent lunar mission has been the NASA's Lunar Reconnaissance Orbiter mission. The Lunar Precursor Robotic Program (LPRP) is a program of robotic spacecraft missions which NASA will use to prepare for future human spaceflight missions to the Moon.[38] Two missions, the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (or LCROSS), originally planned to be launched in October 2008,[39] but was launched on 18 June 2009.[40]

Other moon landings

Progress in space exploration has recently broadened the phrase moon landing to include other moons in the solar system as well. The Huygens probe of the Cassini mission to Saturn performed a successful unmanned moon landing on Titan in 2005. Similarly, the Soviet probe Phobos 2 came within 120 miles (190 km) of performing an unmanned moon landing on Mars' moon Phobos in 1989 before radio contact with that lander was suddenly lost. A similar Russian sample return mission called Phobos-Grunt ("grunt" means "soil" in Russian) is scheduled for launch in early 2012. There is widespread interest in performing a future moon landing on Jupiter's moon Europa to drill down and explore the possible liquid water ocean beneath its icy surface.

Proposed future missions

The most recently launched lunar orbiter is China's Chang'e 2, which was launched in early October 2010. China is also planning to land motorized rovers and collect samples in the Chang'e 3 and Chang'e 4 missions and return lunar soil samples by 2018.[41]

Russia's Luna-Glob 1 expected to be launched in 2012. In 2007 the head of the Russian Space Agency announced plans to send cosmonauts to the Moon by 2025 and establish a permanent manned base there in 2027–2032.[42]

ISRO, the Indian National Space agency, is planning a second version of Chandrayaan named Chandrayaan 2. According to former ISRO Chairman G. Madhavan Nair, "The Indian Space Research Organisation (ISRO) hopes to land two motorised rovers – one Indian and another Russian – on the Moon in 2013, as a part of its second Chandrayaan mission. The rover will be designed to move on wheels on the lunar surface, pick up samples of soil or rocks, do on-site chemical analysis and send the data to the mother-spacecraft Chandrayaan II, which will be orbiting above. Chandrayaan II will transmit the data to Earth." The payloads have already been finalized.[43][44] ISRO has mentioned that due to weight restrictions it will not be carrying any overseas payloads on this mission. The lander weight is projected to be 1,250 kg, and the spacecraft will be launched by the Geosynchronous Satellite Launch Vehicle.

The Google Lunar X Prize competition offers a $20 million award for the first privately funded team to land a robotic probe on the Moon. Like the Ansari X Prize before it, the competition aims to advance the state of the art in private space exploration.[45]

Hoax accusations

Astronaut Buzz Aldrin, lunar module pilot of the first lunar landing mission, poses for a photograph beside the deployed United States flag during an Apollo 11 Extravehicular Activity (EVA) on the lunar surface.

Some people insist that the Apollo Moon landings were a hoax. Their accusations flourish in part because enthusiastic predictions that Moon landings would become commonplace have not yet come to pass. However, empirical evidence is readily available to show that manned moon landings did indeed occur. Anyone on Earth with an appropriate laser and telescope system can bounce laser beams off three retroreflector arrays left on the Moon by Apollo 11,[46] 14 and 15, verifying deployment of the Lunar Laser Ranging Experiment at historically documented Apollo Moon landing sites and so proving equipment constructed on Earth was successfully transported to the surface of the Moon. In addition, in August 2009 NASA's Lunar Reconnaissance Orbiter began to send back high resolution photos of the Apollo landing sites. These photos show not only the large Descent Stages of the lunar landers left behind but also tracks of the astronauts' walking paths in the lunar dust.[47]

See also

References and notes

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  12. ^ "NASA – NSSDC – Spacecraft – Ranger 6 Details". Retrieved 17 february 2011. 
  13. ^ a b "NASA – NSSDC – Spacecraft – Ranger 5 Details". Retrieved 17 february 2011. 
  14. ^ "NASA – NSSDC – Spacecraft – Ranger 7 Details". 
  15. ^ "NASA – NSSDC – Spacecraft – Ranger 8 Details". 
  16. ^ "NASA – NSSDC – Spacecraft – Ranger 9 Details". 
  17. ^ a b "NASA – NSSDC – Spacecraft – Ranger 1 Details". Retrieved 17 february 2011. 
  18. ^ "NASA – NSSDC – Spacecraft – Ranger 2 Details". Retrieved 17 february 2011. 
  19. ^ "Astronautix Luna E-6". Retrieved February 2011. 
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  21. ^ Burrows, William E. (1999). This New Ocean: The Story of the First Space Age. Modern Library. pp. 432. ISBN 0375754857. 
  22. ^ Apollo 13 – A Successful Failure
  23. ^ "In the Shadow of the Moon". Retrieved 7 February 2008. 
  24. ^ "White House "Lost In Space" Scenarios". Retrieved 7 February 2008. 
  25. ^ "Apollo TV Tapes: The Search Continues". Retrieved 8 February 2008. 
  26. ^ Hiten, NSSDC, NASA. Accessed on line 18 October 2010.
  27. ^ SMART 1, NSSDC, NASA. Accessed on line 18 October 2010.
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  29. ^ "Chandrayaan-I Impact Probe lands on the Moon". Times Of India. Retrieved 14 November 2008. 
  30. ^ Lunar Missions Detect Water on Moon
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