Gemini 8

Gemini 8 (officially Gemini VIII) was the sixth manned spaceflight in NASA's Gemini program. The mission conducted the first docking of two spacecraft in orbit, but suffered the first critical in-space system failure of a U.S. spacecraft which threatened the lives of the astronauts and required immediate abort of the mission. The crew was returned to Earth safely. The only other time this happened was on the flight of Apollo 13.

It was the twelfth manned American flight and the twenty-second manned spaceflight of all time (including X-15 flights over 100 kilometres (62 mi)). Command pilot Neil Armstrong's flight marked the second time a U.S. civilian flew into space (Joseph Albert Walker became the first US civilian on X-15 Flight 90). Armstrong had resigned his commission in the United States Naval Reserve in 1960. The Soviet Union had launched the first civilian, Valentina Tereshkova (also the first woman) aboard Vostok 6 on June 16, 1963.