Manned Spacecraft

The Mercury program came to a conclusion just a month before the end of the Vostok program and was followed by the U.S. two-person spacecraft, the Gemini. The Gemini cabin was not only larger than that of Mercury, it was also more sophisticated. The purpose of the Gemini program was to learn more about astronauts' ability to maneuver a spacecraft, to carry out extravehicular activities (EVAs or "space walks"), to rendezvous and dock with other spacecraft, and to perform other operations that would be necessary in the planned Apollo program, which would require such maneuvers to reach the Moon.

Ten Gemini missions flew during 1965 and 1966. During one of these, Gemini 4, astronaut Edward White performed the first extravehicular activity (EVA), a "space walk," by an American. White remained in space for a period of 21 minutes at the end of a 25 ft (7.5 m) umbilical cord connecting him to the main spacecraft.

The Soviets had decided to bypass two-person spacecraft entirely, and went directly to the development of a three-person vehicle. That program was code-named the Voskhod ("Rising") series. On Voskhod 2, the space previously used for the third cosmonaut was replaced with a flexible airlock that allowed egress from the spacecraft. Cosmonaut Alexei Leonov went EVA for over 23 minutes on March 18, 1965, the first time any human had "walked in space."