History: NASA Archive Photography

- Project Gemini (1962–1966, manned missions from 1965)
Project Gemini focused on conducting experiments and developing and practicing techniques required for lunar missions. The first Gemini flight with astronauts on board, Gemini 3, was flown by Gus Grissom and John Young on March 23, 1965. Nine missions followed, showing that long-duration human space flight and rendezvous and docking with another vehicle in space were possible, and gathering medical data on the effects of weightlessness on humans. Together with that, Gemini missions also included the first American spacewalks.
Even though the Gemini project managed to make a docking a year before the Soviet space program, it was too early to call it a victory. The maneuvers practiced by Gemini could be used in two ways: a spacecraft could dock with a rocket stage in orbit around the Earth and use it for going to the Moon or a spacecraft together with a Moon lander could be sent to the Moon by a single rocket and then separate and dock again after the lander had been down on the surface. However, there was a third and more direct way of going to the Moon; the Soviet Union could just build a big rocket and land the top of it on the Moon. That again could take itself back to Earth without using rendezvous or docking. In that case the Gemini project would have been a waste of time.
- Apollo program (1961–1972, manned missions from 1968)