Project Gemini was the second human spaceflight program of the National Aeronautics and Space Administration. It operated between Projects Mercury and Apollo, with 10 manned flights occurring in 1965 and 1966. Its objective was to develop techniques for advanced space travel, notably those necessary for Project Apollo, whose objective was to land humans on the Moon. Gemini missions included the first American extravehicular activity, and new orbital maneuvers including rendezvous and docking.

Project Mercury was the first human spaceflight program of the United States. It ran from 1959 through 1963 with the goal of putting a human in orbit around the Earth. The Mercury-Atlas 6 flight on 20 February 1962 was the first Mercury flight to achieve this goal. Early planning and research was carried out by the National Advisory Committee for Aeronautics, and the program was officially conducted by the newly created NASA. The name comes from Mercury, a Roman mythological god who is often seen as a symbol of speed. Mercury is also the name of the innermost planet of the solar system, which moves faster than any other and hence provides an image of speed, although Project Mercury had no other connection to that planet.

The Mercury program cost approximately $384 million, or about $2.7 billion in 2007 dollars. It was developed by a team of predominantly German rocket engineers who had emigrated to the United States after World War II.