The SM-1, or Submarine Mobile Reactor-1, was a nuclear reactor designed for use in submarines. Developed by the United States Navy, it was the first reactor to be used in a submarine, providing the necessary power for propulsion and onboard systems. The SM-1 was operational from 1959 until 1976 and played a crucial role in advancing nuclear submarine technology. This reactor was part of the Nuclear Navy program, which aimed to enhance the capabilities of submarines by allowing them to operate underwater for extended periods without surfacing. The success of the SM-1 paved the way for more advanced reactors in later submarine designs, contributing to the evolution of naval warfare.