After Shepherd was selected for NASA Astronaut Group 10 in 1984, rumors spread that he had answered a standard interview question about what he did best by saying, "kill people with knives" but he later refused to confirm or deny the account, commenting "it's too good a story". He was the first military non-aviator in astronaut training, following his unsuccessful application for NASA Astronaut Group 9 in 1980. In 1986, Shepherd's Navy SEAL training proved unexpectedly useful to NASA as he helped to direct the underwater salvage operations of the Space Shuttle "Challenger" after its destruction. Shepherd then served as a Mission Specialist on three Space Shuttle flights: mission STS-27 in 1988, mission STS-41 in 1990, which deployed the "Ulysses" probe, and mission STS-52 in 1992. He was the first member of NASA Astronaut Group 10 to fly a space mission.