13. Gemini VIII was the first in-space disaster which required the mission to be aborted
Gemini VIII was scheduled to be a three-day mission in which the spacecraft would rendezvous with an unmanned Agena docking vehicle and dock, both steps necessary as part of the planned Apollo program. It also included a spacewalk to retrieve a piece of experimental equipment from the docking vehicle. Neil Armstrong was the Command Pilot for the mission, and David Scott was the Pilot. It was the first space mission for both men. When Gemini VIII arrived at the rendezvous with the Agena it spent about thirty minutes inspecting the docking vehicle for any damage sustained during its launch. Finding none, Armstrong moved forward and docked the spacecraft, the first docking operation of any spacecraft.
Shortly after docking the Agena began to yaw, and Armstrong, after attempting to stop the motion using the Gemini’s thrusters, decided to undock. As Gemini withdrew from the dock, which was by then tumbling, it entered into a tumbling pattern of its own which increased in speed with the loss of mass from the dock. Armstrong’s ability as a pilot and engineer allowed him to analyze, diagnose, and correct the problem as his spacecraft was tumbling at a rate of one revolution per second. After realizing the problem was with the Gemini, the decision was made to return to earth after one more orbit, allowing them to get closer to a recovery zone. The problem was later determined to have been a malfunctioning thruster on Gemini VIII.