A mission of NASA's Gemini program. Gemini 10 launched July 18, 1966, carrying Michael Collins and John Young. Their ship travelled 475 miles above the earth which was a record at the time. Collins left the spacecraft and walked in space.
The purpose of the mission was to attach scientific equipment to an orbiting Agena rocket. Because the craft was low on fuel, the mission had to be cut short, and the mission objectives were never achieved. The spacecraft returned to earth on July 21, 1966.