9 1953 Submarine Thermal Reactor Also known as S1W, the Submarine Thermal Reactor marked the birth of America’s nuclear navy.The prototype reactor, which was cooled and moderated by pressurized water, and the propulsion equipment were built at Idaho’s Naval Reactors Facility.The reactor and support systems were located inside a hull section duplicating the size and specifications of the USS Nautilus, the Navy’s first nuclear-powered submarine, which was under construction in Connecticut at the time.To facilitate shielding research, a tank of water surrounded a portion of the hull. Before the Nautilus was launched, S1W and its crew simulated a 96-hour voyage from Newfoundland to Ireland. For decades, the reactor aided in the testing of advanced designs and provided training for sailors. “ The nation that first develops nuclear engines will rule the oceans of the world; our enemies are working on such engines; we must be first.” — Adm. Hyman Rickover