Gemini VIII

On March 16, 1966, Gemini VIII accomplished one of spaceflight’s essential milestones: the first docking of two vehicles in orbit, as Neil Armstrong guided his capsule to a gentle link-up with an uncrewed Agena target vehicle. Rendezvous and docking were non-negotiable skills for the Apollo lunar missions, and Gemini VIII proved they could be done.

Minutes after docking, a stuck thruster sent the joined spacecraft into a violent spin approaching one revolution per second. Armstrong undocked and wrestled the tumbling capsule under control using the reentry thrusters — a decision that forced an emergency landing in the Pacific but saved the crew. His calm under pressure was long remembered when crews were chosen for the first lunar landing.