If you have read the book The Right Stuff or watched the movie with the same name, you may know a thing or two about the Mercury program—which was NASA’s first human spaceflight program. And of course, many are familiar with the Apollo program, which famously put the first human on the Moon. However, there would be no Apollo program without the Gemini program, which took place in between the Mercury and Apollo programs from 1964 to 1965.  

Whereas Mercury focused on getting people up into space, Gemini worked toward keeping them up there for an extended period of time—in preparation for Apollo lunar trips of one to two weeks—and practicing the maneuvers and techniques need to carry out a landing. The Gemini program sent two-astronaut spacecraft into Earth orbit. The missions helped NASA understand and master the challenges of spacewalking, rendezvous and docking, and long-duration spaceflight. Explore some of the key accomplishments of the Gemini program below. 

The Launch Vehicle and Spacecraft 

To launch Mercury and Gemini spacecraft, NASA used ballistic missiles designed to carry nuclear warheads. For the Apollo program, huge Saturn launch vehicles were specially designed to carry the much larger lunar spacecraft. 

The Gemini spacecraft began as the Mercury Mark II, an enlarged capsule made by McDonnell Aircraft in St. Louis. As contractor for the Mercury spacecraft, the company had experience vital to Gemini’s success. 

Frank Borman and James Lovell spent 14 days in the cramped cockpit in the photo above from December 4 to 18, 1965. The two hatches have been removed, making the cabin seem roomier than it really was. Each astronaut had only a small window in front of his face.  

Their mission was primarily medical. They endured experiments regarding food, waste, and sleep. Gemini VII also served as the target vehicle for Gemini VI-A during the world’s first space rendezvous. 

Learning to Rendezvous in Space 

The Apollo command and lunar modules had to link up after a lunar landing. NASA used the Gemini program to practice rendezvous and docking in space.  

Gemini VI was supposed to dock with an Agena rocket stage, but the Agena failed to reach orbit. So when NASA launched Gemini VII on a 14-day medical mission in late 1965, it also launched Gemini VI, renumbered to Gemini VI-A because of the changed mission, to meet up with it. The two spacecraft successfully rendezvoused. In 1966, Gemini VIII succeeded in docking with an Agena. 

Learning to Live in Space 

Flying to the Moon would require missions lasting over a week; it took three days just to get there. No Mercury astronaut had spent more than 34 hours in space. Gemini missions needed to prove that humans could live in weightlessness for up to two weeks. Three Gemini missions in 1965 extended time in space from four to 14 days. 

Learning to Walk in Space 

To walk on the Moon or perform useful tasks in space, astronauts had to be able to leave the spacecraft—what NASA called extravehicular activity, or EVA. EVA proved more difficult than expected. Astronauts became overheated and exhausted. It took NASA until the last Gemini mission to refine the techniques and equipment to make spacewalking effective. 

The Gemini program was an essential step for NASA in getting humans to the Moon. See a short summary of each of the 10 missions below.