Gemini XII

At the completion of the previous Gemini flight, the program still had not demonstrated that an astronaut could work easily and efficiently outside the spacecraft. In preparation for Gemini XII new, improved restraints were added to the outside of the capsule, and a new technique—underwater training—was introduced, which would become a staple of future space-walk simulation. Aldrin's two-hour, 20-minute tethered space-walk, during which he photographed star fields, retrieved a micrometeorite collector and did other chores, at last demonstrated the feasibility of extravehicular activity. Two more stand-up EVAs also went smoothly, as did the by-now routine rendezvous and docking with an Agena which was done "manually" using the onboard computer and charts when a rendezvous radar failed. The climb to a higher orbit, however, was canceled because of a problem with the Agena booster.