Project Gemini - Spacecraft

Spacecraft

NASA selected McDonnell Aircraft, which had been the prime contractor for the Project Mercury capsule, to build the Gemini capsule in 1961 and the first capsule was delivered in 1963. The spacecraft was 19 feet long and 10 feet wide with a launch weight of 8,490 pounds. The Gemini capsule first flew with a crew on March 23, 1965.

Gemini was the first manned spacecraft to include an onboard computer, the Gemini Guidance Computer, to facilitate management and control of mission maneuvers. Unlike the Mercury, it used ejection seats, in-flight radar and an artificial horizon—devices similar to those used in the aviation industry.

Unlike Mercury, which could only rotate around the axes of pitch, yaw, and roll to change its orientation in space, the Gemini spacecraft was designed also to translate in all three of the perpendicular axes (forward/backward, left/right, up/down), and also to alter its orbital inclination and altitude. It used these capabilities to dock with the Agena target vehicle, which had its own rocket engine which could be used to perform larger altitude changes.

A major difference between the Gemini and Mercury spacecraft was that Mercury had all systems other than the reentry rockets situated within the capsule, most of which were accessed through the astronaut's hatchway. In contrast, Gemini housed power, propulsion, and life support systems in a detachable Equipment Module located behind the Reentry Module, which made it similar to the Apollo Command/Service Module design. Many components in the capsule itself were reachable through their own small access doors.

The original intention for Gemini was to land on solid ground instead of at sea, using a Rogallo wing rather than a parachute, with the crew seated upright controlling the forward motion of the craft. To facilitate this, the airfoil did not attach just to the nose of the craft, but to an additional attachment point for balance near the heat shield. This cord was covered by a strip of metal which ran between the twin hatches. This design was ultimately dropped, and parachutes were used to make a sea landing as in Project Mercury. The capsule was suspended at an angle closer to horizontal, so that a side of the heat shield contacted the water first. This eliminated the need for the landing bag cushion used in the Mercury capsule.

Early short-duration missions had their electrical power supplied by batteries; later endurance missions used the first fuel cells in manned spacecraft.