Project Gemini was NASA's second human spaceflight program. It was a United States space program started in 1961 and concluded in 1966. Project Gemini was conducted between projects Mercury and Apollo. The Gemini spacecraft carried a two-astronaut crew. Ten crews flew low Earth orbit (LEO) missions between 1965 and 1966. It put the United States in the lead during the Cold War Space Race with the Soviet Union.
Its objective was to develop space travel techniques to support Apollo's mission to land astronauts on the Moon. Gemini achieved missions long enough for a trip to the Moon and back, perfected working outside the spacecraft with extra-vehicular activity (EVA), and pioneered the orbital maneuvers necessary to achieve space rendezvous and docking. With these new techniques proven in Gemini, Apollo could pursue its prime mission without doing these fundamental exploratory operations.
The astronaut corps that supported Project Gemini included the "Mercury Seven", "The New Nine", and the 1963 astronaut class. During the program, three astronauts died in air crashes during training, including the prime crew for Gemini 9. This mission was performed by the backup crew, the only time that had happened in NASA's history to that date.