Extra-vehicular activity (EVA) is any activity done by an astronaut or cosmonaut outside of a spacecraft beyond the Earth's appreciable atmosphere. The term most commonly applies to a spacewalk made outside a craft orbiting Earth (such as the International Space Station), but also has applied to lunar surface exploration (commonly known as moonwalks) performed by six pairs of American astronauts in the Apollo program from 1969 to 1972. On each of the last three of these missions, astronauts also performed deep-space EVAs on the return to Earth, to retrieve film canisters from the outside of the spacecraft. Astronauts also used EVA in 1973 to repair launch damage to Skylab, the United States' first space station.
A "Stand-up" EVA (SEVA) is where the astronaut does not fully exit a spacecraft, but is completely reliant on the spacesuit for environmental support. Its name derives from the astronaut "standing up" in the open hatch, usually to film or assist a spacewalking astronaut.
EVAs may be either tethered (the astronaut is connected to the spacecraft; oxygen and electrical power can be supplied through an umbilical cable; no propulsion is needed to return to the spacecraft), or untethered. Untethered spacewalks were only performed on three missions in 1984 using the Manned Maneuvering Unit (MMU), and on a flight test in 1994 of the Simplified Aid for EVA Rescue (SAFER). A SAFER is a safety device worn on tethered U.S. EVAs, since the capability of returning to the spacecraft is essential.
Apollo 11 was the spaceflight which landed the first humans, Neil Armstrong and Edwin "Buzz" Aldrin, Jr, on Earth's Moon on July 20, 1969, at 20:17:39 UTC. The United States mission is considered the major accomplishment in the history of space exploration.
Launched from the Kennedy Space Center Launch Complex 39 in Merritt Island, Florida on July 16, Apollo 11 was the fifth manned mission, and the third lunar mission, of NASA's Apollo program. The crew consisted of Armstrong as Commander and Aldrin as Lunar Module Pilot, with Command Module Pilot Michael Collins. Armstrong and Aldrin landed in the Sea of Tranquillity and became the first humans to walk on the Moon on July 21. Their Lunar Module, Eagle, spent 21 hours 31 minutes on the lunar surface, while Collins remained in orbit in the Command/Service Module, Columbia. The three astronauts returned to Earth on July 24, landing in the Pacific Ocean. They brought back 47.5 pounds (21.5 kg) of lunar rocks.
Apollo 11 fulfilled U.S. President John F. Kennedy's goal of reaching the Moon before the Soviet Union by the end of the 1960s, which he had expressed during a 1961 mission statement before the United States Congress: "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth."