Getting to the Moon

Apollo 11 left Earth on 16 July 1969 and its crew splashed down eight days later, on 24 July.

Aim where the Moon will be

The Moon is 384,400 km away on average and moves along its orbit at about 1 km every second, so a spacecraft cannot simply point at it and go. It has to aim at the place the Moon will be when it arrives, about three days later. The Apollo flights did it in steps, and the same steps still describe most trips to the Moon.

First the Saturn V put the spacecraft and its third stage into a low parking orbit round Earth, where the crew checked everything. Then the third stage fired again, raising the speed to nearly escape velocity, so the spacecraft coasted out on a long path that the Moon's gravity would catch. Near the Moon the spacecraft fired its own engine to slow down and drop into lunar orbit. This plan, called lunar orbit rendezvous, was the key decision of the programme. As the course on the Moon explains, the spacecraft had three parts: a command module where the crew lived, a service module with the engine and supplies, and a separate lunar module that took two of the three astronauts down to the surface and back up to the waiting command module.

Apollo 11

Apollo 11 launched on 16 July 1969 with Neil Armstrong, Michael Collins and Edwin "Buzz" Aldrin. On 20 July Armstrong and Aldrin flew the lunar module Eagle down to the Sea of Tranquility while Collins orbited in the command module Columbia. After their moonwalk the upper half of Eagle lifted off, docked with Columbia, and the crew splashed down in the Pacific on 24 July. Six Apollo missions landed between 1969 and 1972 and twelve astronauts walked on the Moon. Apollo 13 had to turn back after an explosion in April 1970 and came home safely, and the last landing, Apollo 17, launched on 7 December 1972.

Half a century later people went back towards the Moon. Artemis II launched on 1 April 2026 with NASA astronauts Reid Wiseman, Victor Glover and Christina Koch and Canadian Space Agency astronaut Jeremy Hansen. It looped round the Moon without landing and passed Apollo 13's record for the farthest humans have travelled from Earth, reaching about 406,771 km.

Coming home is the hardest part to survive. A spacecraft falling back from the Moon's distance arrives at the top of the atmosphere at almost escape speed: energy conservation gives about 11 km/s at 120 km up. The air brakes it from there, and the front of the capsule is covered with a heat shield that chars and wears away, carrying the heat off with it. The capsule must hit the air at just the right angle. Too steep and the braking and heating are too violent; too shallow and it can skip back out.

Korea's Danuri

Korea reached the Moon with a robot. KARI's Danuri (KPLO), a 678 kg orbiter, launched on a SpaceX Falcon 9 on 5 August 2022 Korean time. Instead of the fast three-day route it took a low-energy path that swung out to about 1.55 million km and used the pull of the Sun, Earth and Moon to save fuel. After 5.94 million km it reached the Moon on 17 December, made three braking burns on 17, 21 and 26 December, and settled into a circular orbit 100 km above the surface, going round about every two hours at 1.62 km/s. The Korean government called it the seventh country to explore the Moon. Its mission has since been extended to 2027, flying lower: first at 60 km, then in an oval orbit 60 to 200 km above the surface (KASA).