Slayton, Donald Kent (1924-1993), was one of the original seven United States astronauts and a member of the first joint space mission with the Soviet Union. On July 17, 1975, Slayton, Thomas P. Stafford, and Vance D. Brand docked their Apollo spacecraft with a Soviet Soyuz spacecraft carrying Alexei A. Leonov and Valery N. Kubasov in orbit around the earth.