Gemini 8 was the first NASA mission to dock two spacecraft in orbit, joining its crew capsule with an uncrewed Agena target vehicle on March 16, 1966.
Neil Armstrong and David Scott completed the docking over the Pacific Ocean. Soon afterward, the combined spacecraft began spinning rapidly because of a stuck thruster. Armstrong undocked the vehicles and used the Gemini capsule’s reentry-control system to stop the rotation.
The emergency forced NASA to end the mission early, but the docking objective had been achieved. The experience demonstrated both the value and the danger of orbital rendezvous operations, which were essential to Apollo’s planned lunar-orbit rendezvous technique.
Gemini 8 is sometimes remembered mainly for its emergency. Its successful docking was equally important: it proved that spacecraft could meet and connect in orbit under crew control.