Deke Slayton was a Mercury Astronaut, who was one of the original seven astronauts chosen for Project Mercury, the first human spaceflight program of the United States. He was an Air Force test pilot and later served as NASA's Director of Flight Crew Operations. He was also the only member of the Mercury Seven to not fly in a Mercury spacecraft due to a medical issue. He eventually flew on the Apollo-Soyuz Test Project in 1975.