Conducted between projects Mercury and Apollo, Gemini started in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual astronauts flew low Earth orbit (LEO) missions during 1965 and 1966.

Cost: $1.3 billion (1967), $7.8 billion (2019)
Country: United States
First crewed flight: Gemini 3, March 23, 1965
First flight: Gemini 1, April 8, 1964

Gemini was an early NASA human spaceflight program. Gemini helped NASA get ready for the Apollo moon landings. Ten crews flew missions on the two-man Gemini spacecraft. The Gemini missions were flown in 1965 and 1966. They flew between the Mercury and Apollo programs.

What Spacecraft Were Used for the Gemini Program?
NASA designed the Gemini capsule for this program. On the outside, it looked much like the capsule used for the Mercury missions. It was bigger than the Mercury capsule. It could hold two people instead of one. But each astronaut did not have much room. The Gemini capsule improved on the Mercury spacecraft. Basically, the Mercury spacecraft could change only the way it was facing in its orbit. The Gemini could change what orbit it was in.

NASA named the Gemini spacecraft and program after the constellation Gemini. The name is Latin for "twins." NASA used this name because the Gemini capsule would carry two people.

The Gemini capsule flew on a Titan II rocket. The two-stage Titan II was originally a missile. NASA made changes to the missile so it could carry people. Before the first astronauts flew on it, it launched without a crew so that NASA could test its safety.

What Happened on the Gemini Missions?
Astronauts accomplished many things on the Gemini missions. The first flight to carry astronauts was Gemini 3 (also known as Gemini-Titan 3 or GT-3). That flight tested the new vehicle. The Gemini 4 mission included the first U.S. spacewalk. Gemini 5 stayed in orbit for more than a week. The Gemini 6A and 7 missions were in space at the same time and met each other in orbit. Gemini 7 stayed in space for two weeks. Gemini 8 connected with another unmanned spacecraft in orbit.

The Gemini 9 mission tested different ways of flying near another spacecraft. It also included a spacewalk. Gemini 10 connected with another spacecraft and used its engines to move both vehicles. The Gemini 11 mission flew higher than any NASA mission before. The last mission, Gemini 12, solved problems from earlier spacewalks.

Why Was The Gemini Program Important?
Before Gemini, NASA had limited experience in space. The Mercury missions had proved astronauts could fly in space.

But before people could land on the moon, NASA had to learn many things. It had to learn what happened when astronauts spent many days in space. It had to learn how astronauts could go outside a spacecraft in a spacesuit. It had to learn how to connect two spacecraft together in space. Going to the moon would require doing all of these things. Before Gemini, NASA had not done any of them. Gemini proved NASA could do them all.