The Gemini spaceflights of 1965–66 were designed to acquire the skills necessary for the Apollo lunar landing program. A key step was performing docking between two vehicles in space; in the Apollo program, the command module, which carried the astronauts, would have to dock with the lunar module, which would carry two astronauts to the lunar surface. On the previous flights, Gemini 6 and 7 had performed a rendezvous in space, coming within just 30 centimeters (1 foot) of each other.
Gemini 8, commanded by Neil Armstrong and with David Scott as pilot, was scheduled for a three-day mission in which it would dock with a modified rocket stage called the Gemini Agena target vehicle (GATV) and Scott would perform a space walk. The GATV lifted off at 10:00 AM on March 16, 1966. Gemini 8 lifted off at 11:41 AM. Six and a half hours later, Gemini 8 docked with the GATV, the first docking in space.
But 27 minutes after docking, the two spacecraft began to spin out of control. Armstrong undocked Gemini 8, but the spacecraft kept on spinning one revolution every second. (A thruster on Gemini had short-circuited and had been firing nonstop.) The two astronauts got the spacecraft under control before they would have blacked out, but they had to use 75 percent of the fuel in the reentry thrusters to do it. Armstrong and Scott wanted to continue the mission, but since they had used up so much of the reentry fuel, NASA ordered them to return to Earth. The mission lasted only 10 hours and 41 minutes, but it did accomplish the vital step of the first space docking.