Gemini, a Latin word for twins, was designed to carry two astronauts and served as a precursor program for the Apollo lunar landing effort. While the Gemini spacecraft superficially resembled Mercury, it was in fact an entirely new orbital vehicle. It consisted of two sections: a manned spacecraft and an unmanned adapter section. The two astronauts sat in ejection seats in case of a problem during launch.

At the forward end of the manned spacecraft, was a cylinder designed for docking with another spacecraft. The manned spacecraft also contained the re-entry parachute and attitude-control thrusters. As they had been with Mercury, four solid-propellant retrorockets were attached to the heat shield to help bring the spacecraft back to Earth. The adapter section contained all equipment not required inside the manned section: the fuel cells for generating electricity and drinking water, oxygen tanks, eight attitude-control thrusters, orbital maneuvering engines, propellant tanks for the thrusters and reactant tanks for fuel cells.

Between March 1965 and November 1966, 10 manned Gemini missions orbited the Earth. Two unmanned Gemini missions were launched before the manned flights began. During the 20 months of the Gemini Program, 16 U.S. astronauts would spend a total of 1,940 hours in space answering the critical questions: could astronauts rendezvous and dock with another space vehicle, safely walk in space and endure a two week mission? The answer to all of those questions was yes, and what followed from that experience was the Apollo Program, putting Americans on the moon and safely returning them to Earth.

The Museum's display is a full-scale model of the Gemini spacecraft, hanging from the ceiling in the Modern Jet & Space Age Gallery.