Apollo, Moon-landing project conducted by the U.S. National Aeronautics and Space Administration in the 1960s and 70s. The Apollo program was announced in May 1961, but the choice among competing techniques for achieving a Moon landing and return was not resolved until considerable further study. In the method ultimately employed, a powerful launch vehicle (Saturn V rocket) placed a 50-ton spacecraft in a lunar trajectory. Several Saturn launch vehicles and accompanying spacecraft were built. The Apollo spacecraft were supplied with rocket power of their own, which allowed them to brake on approach to the Moon and go into a lunar orbit. They also were able to release a component of the spacecraft, the Lunar Module (LM), carrying its own rocket power, to land two astronauts on the Moon and bring them back to the lunar orbiting Apollo craft.

The first manned Apollo flight was delayed by a tragic accident, a fire that broke out in the Apollo 1 spacecraft during a ground rehearsal on January 27, 1967, killing all three astronauts. On October 11, 1968, following several unmanned Earth-orbit flights, Apollo 7 made a 163-orbit flight carrying a full crew of three astronauts. Apollo 8 carried out the first step of manned lunar exploration; from Earth orbit it was injected into a lunar trajectory, completed lunar orbit, and returned safely to Earth. Apollo 9 carried out a prolonged mission in Earth orbit to check out the LM. Apollo 10 journeyed to lunar orbit and tested the LM to within 15.2 km (50,000 feet) of the Moons surface. Apollo 11, in July 1969, climaxed the step-by-step procedure with a lunar landing; on July 20 astronaut Neil Armstrong became the first human to set foot on the Moons surface.

Apollo 13, launched in April 1970, suffered an accident caused by an explosion in an oxygen tank but returned safely to Earth. Remaining Apollo missions carried out extensive exploration of the lunar surface, collecting 382 kg (842 pounds) of Moon rocks and installing many instruments for scientific research, such as the solar wind experiment, and the seismographic measurements of the lunar surface. Apollo 17, the final flight of the program, took place in December 1972. In total, 12 American astronauts walked on the Moon during the six successful lunar landing missions of the Apollo program.

A chronology of spaceflights in the Apollo program is shown in the table.

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Apollo | space program | Britannica.com