Donald Kent "Deke" Slayton (1924–1993) was one of the Mercury Seven but was grounded before his Mercury flight due to a heart arrhythmia discovered in 1962. A WWII Air Force fighter pilot and test pilot, he became chief of the Astronaut Office at NASA, managing crew selection and flight assignments from 1962 to 1972. After his cardiac condition was resolved, he finally flew in space on the Apollo-Soyuz Test Project (1975) at age 51.