simpson took a two-year leave of absence from westinghouse in 1946 to work at oak ridge national laboratory where they applied nuclear energy to the generation of power. when he returned to westinghouse he became responsible for research and development of nuclear energy generation at the bettis atomic power laboratory. he was deeply involved in the design and construction of the first submarine atomic power plant in the uss "nautilus" (ssn-571). in the late 1950s, he organized the westinghouse astronuclear laboratory, with a federal contract to build a nuclear thermal rocket. it was successfully tested, but sidelined by nasa’s gemini program.