American space program to practice rendezvous and docking techniques and to gain experience of long-duration space missions. The Gemini missions showed that men could live safely in space for periods long enough to reach the Moon and return, and that the docking operations required for Moon missions could be successfully accomplished. The achievements of the Gemini program established American leadership in the space race.
The Gemini project was born late in 1961, while the first Mercury flights were underway. The capsule had to be bigger than Mercury and it had to be manoeuvrable, with considerable on-board control. To assist with rendezvous and docking, and to make pinpoint landings possible, a microcomputer was installed, the forerunner of the Apollo on-board computers without which the Moon landings could never have been made.
The crew capsule in Gemini, called the re-entry module, was conical, with an extended nose called the rendezvous and recovery section, which contained rendezvous radar and landing parachutes. Also in the nose were 16 thrusters for attitude control during re-entry; these added considerably to the accuracy of Gemini splashdowns. The base diameter of the re-entry module was 7 feet 6 inches (2.3 in), and the diameter of the extended nose 39 inches (1 m). The conical crew section was 5 feet 10½ inches (1.8 m) long; including the rendezvous and recovery section, it was 11 feet (3.35 m) long.
Behind the re-entry module was the adapter module, in two parts: the retrograde section, containing retro-rockets; and the equipment section, containing fuel cells for electricity generation, and attitude control rockets for in-flight manoeuvring. Before re-entry, the equipment section was jettisoned to reveal the retro-rockets, which later were also jettisoned to leave the heat shield at the base of the re-entry module. The base diameter of the adapter module was 10 feet (3 m), and its total length 7 feet 6 inches (2.3 m). The complete Gemini weighed about 8,000 lb. (3,600 kg).
Astronaut access to the capsule was through two hatches, one above each crew seat. Each hatch had a crescent-shaped forward-facing window. A two-stage Titan II rocket launched Gemini spacecraft. In the event of a launch failure, the astronauts would be catapulted to safety by ejector seats. For spacewalks, both astronauts donned suits, the craft was depressurized, and one of the hatches was opened. An astronaut either left the capsule entirely, or performed a “stand-up” EVA by looking out the hatch.
Gemini was tested in orbit before manned flights began. -The complex nature of the missions demanded a new control center; this was the Manned Spacecraft Center (now Johnson Space Center) in Houston. Gemini 4 was the first mission not controlled from the Cape.
The Gemini series accomplished the first orbit change by a manned spacecraft (Gemini 3), the first space docking (Gemini 8), and various duration records for spaceflight and extravehicular activity. Considerable photography of the Earth’s surface and weather patterns was also accomplished during the Gemini missions, paving the way for later Earth resource surveys.