Moon landing

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Still frame from the video transmission of Neil Armstrong stepping onto the surface of the Moon on 20 July 1969. An estimated 500 million people worldwide watched this event, the largest television audience for a live broadcast at that time.[1][2]

A moon landing is the arrival of a spacecraft on the surface of a planet's natural satellite, and in this case, refers specifically to landings on the lunar surface of Earth's Moon. This includes both manned and unmanned (robotic) missions.


[edit] Unmanned landings

Since the Soviet Union first succeeded in implementing the concept in 1966, this term referred to 18 spacecraft landings on the Moon through 1976. Nine of these missions returned to Earth bearing samples of moon rocks. United States and India are the other countries to make unmanned moon landings.

The Soviet Union later achieved sample returns via the unmanned Luna 16, Luna 20 and Luna 24 moon landings. Since this was during the time of the Cold War, the contest to be the first on the Moon was one of the most visible facets of the Space Race.

[edit] Manned landings

The United States space agency NASA achieved the first manned landing on Earth's Moon as part of the Apollo 11 mission commanded by Neil Armstrong. On July 20, 1969, Armstrong landed the lunar module Eagle on the surface of the Moon with a companion, while the third astronaut orbited above. Armstrong was the first human to set foot on the moon, with Buzz Aldrin being the second. Armstrong and Aldrin spent a day on the surface of the Moon before returning to Earth. NASA carried out six manned moon landings between 1969 and 1972.

[edit] Scientific background

The primary concern of any moon landing is the high velocity involved that arises 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, only a rocket can continue to increase its speed at high altitudes in the vacuum outside the Earth's atmosphere.

Upon approach of the target moon, the spacecraft must decelerate enough to land safely. The velocity to be shed from the target moon's gravitational attraction is roughly equal to the escape velocity of the target moon. For Earth's Moon, this figure is 2.4 kilometers per second or around 6,000 miles per hour. This change in velocity (referred to as the 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 a moon landing on Titan such as that carried out by the Huygens probe. 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.

Whatever method is used to slow a spacecraft as it nears a moon, the key requirement for a "true" moon landing is to be traveling at a survivable speed upon reaching the moon's surface that allows continued operation after touchdown. Such landings may be characterized as "soft" if a human could survive them, and "hard" if only a ruggedized machine would do so. Initial American attempts at performing the first hard moon landing in 1962 failed; the Soviets succeeded in making the first successful hard landing on the Moon in 1966. Generally a hard landing is categorized as one occurring at 100 miles per hour or slower.

Above these speeds, the space mission ends not in a landing but a so-called crash impact where the vehicle and its instruments do not survive touchdown, which without braking rockets generally occurs at speeds of 3000-5000 miles per hour. Such impacts can occur because of malfunctions in a spacecraft, or they can be deliberately arranged for vehicles that do not have an on board landing rocket such as the 2008 Indian MIP. There have been many such moon crashes. 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 and reaching intermediate orbits prior to landing; in particular, lunar orbit rendezvous. Thus systems engineering and logistics become major factors in the design of any moon landing mission.

[edit] 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 Soviet, 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 the atom bomb, which killed tens 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 October 4, 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. This dramatic and successful demonstration of the new R-7 Semyorka rocket on only its third test flight meant that the Soviets could use ballistic missiles carrying hydrogen bombs in a surprise attack against any target on Earth, a frightening new capability the Americans did not have. Further, 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, respectively.

The American response to these Soviet achievements was to greatly accelerate previously languishing space and missile projects. 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 the newly formed NASA space agency for various projects which would demonstrate 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.

[edit] U.S. unmanned hard landings (1958-1965)

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; however Rangers 4 and 6 successfully repeated the Soviet lunar impacts as part of their secondary missions. Failures included three American attempts 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 at around 6,000 miles per hour as planned.

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 Failure - 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 Failure - spacecraft computer; crash impact
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

[edit] 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 over 37,000 miles (60,000 km), twice as far away 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.

[edit] Ranger missions

The Ranger 1 and 2 Block I missions were virtually identical. 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 670,000 miles (1,080,000 km). 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. All three Block II missions carried a 94 pound, two-foot diameter landing sphere (made of balsa wood) designed to withstand a 150 mile per hour impact. 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 56 pound, one-foot diameter metal payload sphere floated and was free to rotate in a liquid freon reservoir contained in the landing sphere. 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. Four pounds of water were also included to provide thermal control for the lander, absorbing heat and boiling off as low-pressure steam during the hot lunar daytime and retaining sufficient heat to allow the lander electronics to avoid freezing temperatures during the cold lunar nighttime. The batteries and water supply 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 ten-foot-high, 730 pound Ranger Block II mother ship carried a 200 scan line television camera which was to capture images from 2,400 miles (3,900 km) down to 37 miles (60 km) during the free-fall descent to the lunar surface. The 13 pound camera was designed to transmit a picture every 10 seconds. Other instruments gathering data before the mother ship crashed onto the Moon at 6,500 miles per hour were a gamma ray spectrometer to measure overall lunar chemical composition and a radar altimeter. At eight seconds before impact and 13 miles (21 km) above the lunar surface, the radar altimeter was to give a signal ejecting the landing capsule and its 236 pound solid-fueled braking rocket overboard from the Block II mother ship. The braking rocket was to slow the landing sphere to a dead stop at 1,100 feet (340 m) above the surface and separate, allowing the landing sphere to free fall once more and hit the surface at a survivable speed of 100 miles per hour.

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.

First image of the Moon taken by a US spacecraft, Ranger 7. The large crater at center right is Alphonsus

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 weighing a total of 350 pounds 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. The final pictures taken were expected to have a resolution of around two feet. 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 failure 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.

[edit] U.S.S.R. unmanned hard landings (1958-1966)

While American lunar exploration missions were undertaken in full view of public scrutiny, Soviet moonshots of the 1960s and 1970s were conducted under a policy of extreme governmental secrecy. Only with the coming of glasnost in the late 1980s and the fall of the Soviet Union in 1991 did historical records come to light allowing a 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. 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 failure in reaching the Moon. Launch explosions were not acknowledged at all. This policy had the effect of hiding Soviet moonshot failures from public view, making their successes seem even more impressive.

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 Failure - missed moon, but first spacecraft to solar orbit
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
Luna-9 1580 Semyorka - 8K78 31 January 1966 Moon landing Success - first lunar hard landing, numerous photos
Luna-13 1580 Semyorka - 8K78 21 December 1966 Moon landing Success - second lunar hard landing, numerous photos
In the Ocean of Storms, a widely reprinted 1967 Soviet painting by Aleksei Leonov and Andrei Sokolov, depicts a future traveler examining the Luna 9 braking rocket and landing capsule which had performed the first unmanned moon landing in 1966. Leonov, who had previously made the first spacewalk, was at this time generally viewed as the Soviet cosmonaut most likely to become the first human on the Moon.

The Luna 9 spacecraft, launched by the Soviet Union, performed the first successful Moon landing on February 3, 1966 using the "hard landing" technique. Airbags protected its 200 pound ejectable capsule which survived an impact speed of over 30 miles per hour—the speed of many automobile accidents causing fatalities on Earth. Luna 13 duplicated this feat with a similar moon landing on December 24, 1966. Both returned panoramic photographs that were the first views from the lunar surface.

[edit] American unmanned soft landings (1966-1968)

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.

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

[edit] Transition from direct ascent landings to lunar orbit operations (1966)

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, visually graphing how the U.S. started behind but eventually in the mid 1960s caught up and surpassed the Soviet Union, culminating in Moon landings.

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 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.

[edit] 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 1582 Molniya-M 31 March 1966 Lunar orbiter Success - 2738 km x 2088 km x 72 deg orbit, 178 m period, 60 day science mission
Luna-11 1640 Molniya-M 24 August 1966 Lunar orbiter Success - 2931 km x 1898 km x 27 deg orbit, 178 m period, 38 day science mission
Luna-12 1620 Molniya-M 22 October 1966 Lunar orbiter Success - 2938 km x 1871 km x 10 deg orbit, 205 m period, 89 day science mission
Cosmos-159 1700 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 1700 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 5700 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 5700 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.

[edit] U.S. 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 - 1160 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 - 1860 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 - 1860 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 - 6111 km X 2706 km x 86 deg orbit, 721 m period, 180 day photography mission
Lunar Orbiter 5 386 Atlas - Agena 1 August 1967 Lunar orbiter Success - 6023 km X 195 km x 85 deg orbit, 510 m period, 183 day photography mission

[edit] Soviet circumlunar loop flights (1967-1970)

It was 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. 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. 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 5400 Proton 10 March 1967 High Earth Orbit unmanned Failure - stranded in elliptical high Earth orbit, unable to initiate controlled high speed atmospheric reentry test
Cosmos-154 5400 Proton 8 April 1967 High Earth Orbit unmanned Failure - stranded in elliptical high Earth orbit, 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 5140 Proton 2 March 1968 High Earth Orbit unmanned Failure - 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 5375 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 5375 Proton 10 November 1968 Circumlunar Loop non-human biological payload Failure - 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 5979 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 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
Earthrise, 24 December 1968 (NASA)

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, believing from faulty CIA intelligence that a Soviet manned lunar flight was imminent in late 1968[dubious ], NASA fatefully changed the flight plan of Apollo 8 from an Earth-orbit to a riskier 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.

[edit] American manned Moon landings (1969-1972)

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

[edit] 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.

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.

In conversation with Webb, Kennedy said:

Everything we do ought to really be tied in to getting on to the moon ahead of the Russians [...] otherwise we shouldn't be spending that kind of money, because I'm not interested in space [...] The only justification for [the cost] is because we hope to beat [the USSR] to demonstrate that instead of being behind by a couple of years, by God, we passed them.[citation needed]

The Saturn V booster was the key to U.S. moon landings. It used more efficient liquid hydrogen fuel instead of kerosene in its upper stages in order to lift heavier payloads beyond Earth orbit. The Saturn had a perfect record of zero failures in thirteen launches. By contrast, the Soviet N-1 exploded in flight during four secret test launches and never achieved operational status.

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.

[edit] 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.

[edit] 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. Ironically, 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 on the Moon (manual landing required), exploration on foot in direct vicinity of landing site
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 walking distance (less than 200 meters) of the Surveyor 3 probe
Apollo 13 Saturn V James Lovell, Jack Swigert, Fred Haise 11 April 1970 Lunar landing Successful Failure [3] - 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 May 14, 1973 Earth orbit Success - Launch of Skylab space station
Skylab 2 Saturn 1B Charles "Pete" Conrad, Paul Weitz, Joseph Kerwin May 25, 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 July 28, 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 November 16, 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 July 15, 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, with twelve walking on its surface and three making the trip twice. Apollo 8 was a lunar-orbit-only mission, Apollo 10 included powered descent and then an abort-mode ascent of the LM, 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.[4]

[edit] Human 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

[edit] 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.[5]

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

On August 16, 2006, the Associated Press reported that NASA is currently 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.[6]

[edit] Soviet unmanned soft landings (1969-1976)

U.S.S.R. Mission Mass (kg) Booster Launched Mission Goal Mission Result Landing Zone Lat/Lon
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 5700 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 5600 Proton 12 September 1970 Sample return Success - returned 0.10 kg of moon dust back to Earth Mare Fecunditatis 000.68S 056.30E
Luna-17 5700 Proton 10 November 1970 Lunar rover Success - Lunokhod-1 rover traveled 10.5 km across lunar surface Mare Imbrium 038.28N 325.00E
Luna-18 5750 Proton 2 September 1971 Sample return Failure - lunar crash impact Mare Fecunditatis 003.57N 056.50E
Luna-20 5727 Proton 14 February 1972 Sample return Success - returned 0.05 kg of moon dust back to Earth Mare Fecunditatis 003.57N 056.50E
Luna-21 5950 Proton 8 January 1973 Lunar rover Success - Lunokhod-2 rover traveled 37.0 km across lunar surface LeMonnier Crater 025.85N 030.45E
Luna-23 5800 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 5800 Proton 9 August 1976 Sample return Success - returned 0.17 kg of moon dust back to Earth Mare Crisium 012.25N 062.20E

[edit] Indian unmanned hard landings (2008-)

India became the third country to reach the surface of the moon with a dedicated scientific probe when its lunar orbiting spacecraft Chandrayaan 1 released the Moon Impact Probe. MIP reached the surface of the Moon at 2034 UT(0804 IST) on Nov 14 2008. This date was chosen to commemorate the birthday of Jawaharlal Nehru, the first Indian Prime Minister who initiated India's space program. Developed in India by the Indian Space Research Organisation (ISRO), the MIP had the Indian flag painted on its exterior. Although Japan and ESA had previously commanded their orbiters Hiten and SMART-1 to crash in selected zones on the Moon's surface at the end of their respective lifetimes, India's MIP was the first probe designed specifically for a trip to the lunar surface since the Soviet lander Luna 24 in 1976.

Weighing 34 kilograms, the box shaped MIP 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 as MIP approached it, relaying those pictures back to Earth during the MIP's descent. The mass spectrometer made measurements of the extremely thin lunar atmosphere. The radar altimeter measured the rate of descent of the MIP probe to the lunar surface, testing that technology for future Indian soft landing missions. Such a soft landing is planned for 2010 or 2011 during the upcoming Chandrayaan 2 mission.

The Indian MIP-1 probe did not include braking rockets and was destroyed upon impacting the lunar surface at its planned speed of 3,100 miles per hour. Its achievement is roughly equivalent to the American Ranger 7 mission flown in 1964.

Indian Mission Mass (kg) Booster Launched Mission Goal Mission Result Landing Zone Lat/Lon
MIP 32 PSLV C11 14 November 2008 Lunar Impact Success - Crashed at 3,100 miles per hour as planned, measured atmosphere and descent rate, returned high-altitude photos taken before impact. Shackleton (crater) 000.00S 016.30E

[edit] 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 October 2009. 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.

[edit] Future plans

The next lunar orbiter currently scheduled for launch is 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.[7] Two missions, the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS), originally planned to be launched in October 2008,[8] are now currently scheduled for a launch on June 2, 2009, at the earliest.[9]

Russia plans to send cosmonauts to the Moon by 2025 and establish a permanent manned base there in 2027-2032.[10]

ISRO, the Indian National Space agency, has announced the Chandrayaan program for Lunar exploration. The second mission Chandrayaan II plans to land a motorised rover by 2010/2011.

Other nations, including China, have expressed interest in pursuing human landings on the Moon, but none have currently announced formal plans.

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.

[edit] Hoax accusations

Some conspiracy theorists have insisted that the Apollo moon landings were a hoax. These accusations flourish in part because predictions by enthusiasts that Moon landings would become commonplace have not yet come to pass. Some claims can be empirically discredited by three retroreflector arrays left on the Moon by Apollo 11,[11] 14 and 15. Today, anyone on Earth with an appropriate laser and telescope system may bounce laser beams off these devices, verifying deployment of the Lunar Laser Ranging Experiment at historically documented Apollo moon landing sites. This evidence gives strong standing to Man-Made devices having made successful landings.

[edit] See also

[edit] References & notes

[edit] External links

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