Gemini 5

Gemini 5 carried Gordon Cooper and Pete Conrad on an endurance flight from August 21 to 29, 1965. Its nearly eight days in orbit demonstrated that astronauts and spacecraft could operate for a period comparable to an Apollo lunar journey. Fuel cells supplied electrical power, enabling a much longer flight than battery-powered Gemini 4. Medical studies examined adaptation to weightlessness and the return to normal gravity. The crew deployed a rendezvous evaluation pod, but falling oxygen pressure in the fuel-cell supply prompted cancellation of the planned approach and temporary power conservation. Ground analysis allowed normal power use to resume. The crew subsequently performed radar tests and a simulated rendezvous, while later maneuvering-thruster failures restricted operations. Gemini 5 returned one orbit early because of threatening weather near the recovery area. Despite the incomplete pod exercise and a landing short of the target, the mission established long-duration experience needed for Apollo and later station operations.