He was born in San Antonio, Texas and earned a B.S. from the U.S. Military Academy in 1952, and an M.S. in aeronautical engineering from the University of Michigan in 1959. He later married and had two children.
He was chosen with the second group of astronauts in 1962. As pilot of Gemini 4 was the first American to make a spacewalk, and was backup command pilot for Gemini 7. He had been selected to be command module pilot for the first Apollo program flight.