Gemini 8 performed the first docking between two spacecraft in orbit on 16 March 1966.
Astronauts Neil Armstrong and David Scott flew Gemini 8 and docked with an uncrewed Agena target vehicle. The achievement was essential preparation for Apollo, whose lunar missions required spacecraft to rendezvous and connect in orbit.
Soon after docking, the combined spacecraft began spinning rapidly because of a stuck thruster on Gemini 8. Armstrong and Scott undocked, but the problem continued. Armstrong used the reentry-control system to stop the rotation, ending the emergency while consuming much of the spacecraft’s control fuel.
The mission was terminated early, so Gemini 8 did not complete its planned objectives. It nevertheless proved that orbital docking was possible and demonstrated the importance of precise spacecraft control. Gemini 6A and Gemini 7 had earlier achieved the first crewed rendezvous, but they did not dock; that distinction belongs to Gemini 8.