Moon landing

• 1. Introduction

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  In December 1972, Gene Cernan stepped off the lunar surface, the last of twelve astronauts to walk on the Moon. After him, the dust settled and stayed undisturbed for decades. No spacecraft made a soft landing without significant damage between Luna 24 in 1976 and Chang'e 3 in 2013. That is a gap of thirty-seven years in the human reach toward another world. The first object ever to touch the Moon was Luna 2, which arrived in 1959 by crashing into it on purpose. The story that runs between these dates is not a smooth ascent. It is a record of explosions on the launch pad, spacecraft stranded in Earth orbit, and probes that missed the Moon entirely or slammed into it at the wrong speed. Why did two superpowers pour so much effort into landing on a place with no air and no water? Why did landing matter more than flying past or orbiting? And how does a machine traveling at thousands of kilometers per hour bring itself to a dead stop on a surface no one had ever touched? The answers begin with a simple distinction that decides whether a mission is a triumph or a wreck: the difference between a hard landing and a soft one.

• 2. Hard And Soft

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  A spacecraft approaching the Moon is pulled toward the surface at ever-increasing speed by gravity. To survive, it has two choices. It can decelerate to less than about 160 kilometers per hour and be ruggedized to withstand the impact, which is a hard landing. Or it can slow to negligible speed at the moment of contact, which is a soft landing and the only option for humans. The Soviet Union performed the first hard landing in 1959, deliberately crashing Luna 2 into the surface at high speed. The United States duplicated the feat in 1962 with Ranger 4. The escape velocity of Earth's Moon is 2.38 kilometers per second, and a soft landing requires shedding nearly all of that velocity, usually with a braking rocket carried up from Earth. Sixteen Soviet, U.S., Chinese, and Indian spacecraft eventually used such retrorockets to settle gently and run experiments. There is one strange exception to the rocket rule. The Huygens probe reached Saturn's moon Titan in 2005 by using atmospheric entry techniques, possible because Titan has the thickest atmosphere of any moon. Crash landings were not always failures. During the Apollo program, the spent S-IVB third stage of the Saturn V and the discarded ascent stage of the Lunar Module were deliberately crashed into the Moon. Their impacts registered as moonquakes on seismometers left behind, and those readings helped map the internal structure of the Moon.

• 3. Two Superpowers, One Sky

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  On the 4th of October 1957, the Soviet Union launched Sputnik 1, the first artificial satellite to orbit the Earth, and the Space Race began. Its radio beacon beeped overhead every 96 minutes, and the much larger R-7 booster could be seen co-orbiting beside it. To the United States the implication was alarming. The same rockets could carry nuclear warheads across the world in under thirty minutes. The shock was sharpened by what followed. In 1959 the R-7 launched the first escape from Earth's gravity into solar orbit, the first crash impact onto the Moon, and the first photographs of its never-before-seen far side. These were Luna 1, Luna 2, and Luna 3. The American response was to accelerate military missile work and to create a civilian space agency, NASA. The political background reached back to World War II, which had produced the V-2 ballistic missile that killed thousands in attacks on London and Antwerp, and the atom bomb. One proposal from the United States Air Force was Project A119, a plan to detonate a nuclear explosive on the Moon. Carl Sagan researched its effects, and a human landing was ultimately favored because the negative outcomes of the explosion were judged too great. That choice pointed the entire effort toward putting people, not bombs, on the surface.

• 4. A Catalogue Of Failure

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  Fifteen consecutive U.S. uncrewed lunar missions from 1958 to 1964 failed their primary photographic goals. The Pioneer and Ranger programs could not reach the Moon, and the record is a litany of pad explosions, misfires, and reentries. The Soviet side hid its own failures by design. The Soviets assigned a public Luna number only if a launch sent a spacecraft beyond Earth orbit. Failures that stranded in Earth orbit were often relabeled as Sputnik or Cosmos missions, and launch explosions were not acknowledged at all. After the fall of the Soviet Union in 1991, the records were released and the true tally emerged. Booster malfunctions ended attempt after attempt, sometimes within seconds of liftoff. The American Ranger landers carried an ingenious design. A 42-kilogram metal payload sphere floated in a reservoir of liquid freon inside a balsa-wood impact-limiter, weighted so it would rotate to set its seismometer upright no matter how the lander came to rest. The sphere held a seismometer sensitive enough to detect the impact of a 5-pound meteorite on the opposite side of the Moon. The first three Ranger landing attempts in 1962 all failed, with heat sterilization of the spacecraft on the ground blamed for in-flight computer and power failures. The turning point came in 1964 and 1965. Ranger 7 returned 4308 photos before crashing into Mare Cognitum, breaking a six-year string of failures. That success was instrumental in letting the 1965 NASA budget pass through Congress without cuts to the crewed program.

• 5. Learning To Touch Down

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  The Luna 9 spacecraft made the first successful soft Moon landing on the 3rd of February 1966. Airbags protected its 99-kilogram ejectable capsule, which survived an impact speed of over 15 meters per second and returned the first panoramic photographs from the lunar surface. Luna 13 repeated the feat in December of the same year. The United States followed with the Surveyor program, built to find a safe site for a human landing and to test the radar and landing systems for a true controlled touchdown. Five of Surveyor's seven missions succeeded. Surveyor 1 returned 11,000 pictures and reached its site on three footpads using a radar-controlled, adjustable-thrust retrorocket. That technology mattered more than it might seem. The Luna 9 airbag landing at a ballistic impact speed had more in common with the failed 1962 Ranger attempts than with Surveyor's gentle, controlled descent. Only Surveyor 1 had landed using the methods a crewed flight would need. By mid-1966 the United States had begun to pull ahead. The Soviets kept returning lunar soil with robots, sending Luna 16 home with samples in 1970, but two Lunokhod rovers showed how much robots could do. Lunokhod 1 covered 10.5 kilometers and Lunokhod 2 covered 37 kilometers across the surface, operating for ten months and four months respectively. There was a deeper hurdle waiting in orbit. The first lunar orbiters discovered mascons, dense concentrations of material beneath the maria that could send a crewed lander dangerously off course in the final minutes of descent.

• 6. The Long Way Home

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  A vehicle returning from the Moon hits Earth's atmosphere at around 40,000 kilometers per hour, far faster than the roughly 27,000 of a craft returning from low Earth orbit. The deceleration can reach the limits of human endurance even in a normal reentry. A slight error in flight path or reentry angle can produce fatal forces. Mastering that return became the central goal of the Soviet Zond program, which sent spacecraft looping around the Moon on a free return trajectory without entering orbit. Zond 5 was the first spacecraft to carry life from Earth to the vicinity of the Moon and back, with a payload of two tortoises, insects, plants, and bacteria. It returned safely in 1968 despite landing off-target in the Indian Ocean. Zond 6 looped the Moon as well, but loss of cabin air pressure killed its biological payload and a parachute failure caused severe damage on landing. Both Zond flights flew off-nominal reentries that would have been fatal to a human crew. In December 1968 cosmonauts at Baikonur went on alert and asked to fly the Zond then in final countdown, hoping to beat the Americans to the Moon. The Soviet Politburo decided the risk of crew death was unacceptable and scrubbed the launch. Their caution proved wise, because that same unnumbered Zond was destroyed in another uncrewed test when it finally launched weeks later. Worried by CIA reports of a possible Soviet circumlunar flight, NASA changed the plan of Apollo 8 from an Earth-orbit test to a lunar orbit mission. Apollo 8 carried out the first human trip to the Moon on the 24th of December 1968, flying ten full orbits and returning safely.

• 7. Twelve On The Surface

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  Twenty-four U.S. astronauts traveled to the Moon's vicinity under the Apollo program, three of them twice, and twelve walked on its surface. The path there ran through political will. President John F. Kennedy asked Vice President Lyndon Johnson which scientific achievement would prove U.S. world leadership, and Johnson answered that the country had an even chance of beating the Soviets to a crewed landing but not at anything less. Landing, unlike a flyby or an orbiting lab, would capture the world's imagination. Public opinion shifted with the campaign. By 1965-58 percent of Americans favored Apollo, up from 33 percent two years earlier. The Saturn V launch vehicle achieved a perfect record of zero catastrophic failures in thirteen launches. Apollo 10 flew a full dress rehearsal in May 1969, dropping within 47,400 feet of the surface with a lunar module too heavy to land. Then came the six landings, spanning a 41-month period that began on the 20th of July 1969 with Neil Armstrong and Buzz Aldrin aboard Apollo 11. Each landing was flown by two pilot-astronauts in a Lunar Module while a third crew member stayed in the command module. Apollo 11 set down at the Sea of Tranquility, Apollo 15 at Hadley Rille, Apollo 17 at Taurus-Littrow. President Richard Nixon had speechwriter William Safire prepare a condolence speech in case Armstrong and Aldrin became marooned and could not be rescued. The Soviet effort to match them collapsed after the death of chief designer Sergey Korolev and the successive launch failures of the N1 booster in 1969. A landing craft had been built and Alexei Leonov selected, but the crewed landing was first delayed, then cancelled.

• 8. Footprints And Flags

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  Scientists believe the six American flags planted by astronauts have been bleached white by more than forty years of solar radiation. Images from the Lunar Reconnaissance Orbiter Camera show that five of the six are still standing and casting shadows. The exception is Apollo 11. Buzz Aldrin reported that its flag was blown over by the exhaust from the ascent engine during liftoff. The artifacts left behind tell their own story of loss and rediscovery. NASA lost the original slow-scan television tapes of the Apollo 11 Moon walk, made before conversion for conventional TV. Those tapes were found in 2008 and sold at auction in 2019 for the 50th anniversary of the landing. The long quiet after Apollo broke in stages. Chang'e 3 ended the drought with China's first soft landing on another body, releasing the Yutu rover, which moved 114 meters before a malfunction stopped it. In 2019 Chang'e 4 became the first spacecraft to land on the far side of the Moon, touching down in Von Kármán crater and relying on the Queqiao relay satellite at the Earth-Moon L2 point to talk to Earth. On the 23rd of August 2023, ISRO landed Chandrayaan-3 near the lunar south pole, making India the fourth nation to soft-land. Japan became the fifth with the SLIM lander on the 19th of January 2024. The newest chapter belongs to commercial flight. Intuitive Machines' Odysseus landed in February 2024 as the first privately owned spacecraft to reach the Moon, though a broken leg left it tilted at 18 degrees. A year later, Firefly Aerospace's Blue Ghost landed upright near Mons Latreille in Mare Crisium, the first fully successful commercial landing, operating for 14 days and into 5 hours of the lunar night before its mission concluded on the 16th of March 2025.