 Complete the following phrase:  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 its 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, Shepherds Navy SEAL training proved unexpectedly useful to NASA as he helped to direct the underwater salvage operations of the Space Shuttle Challenger after its 