39. Hyman Rickover
Hyman Rickover’s long naval career was based on his engineering skills. He was for example a consultant during the renovation of the electrical drive on USS California, sunk at Pearl Harbor. But it was his long leadership of the US Navy’s nuclear power programs which led to the nuclear powered supercarriers and submarines, starting with USS Nautilus. He served 63 years in uniform, longer than any man in the history of the US Navy and for decades every officer desiring to enter the Navy’s nuclear program had to pass a personal interview with the irascible Admiral, many of which became legend.