The S1C reactor was a prototype naval reactor designed for the United States Navy to provide electricity generation and propulsion on warships. The S1C designation stands for: * S = Submarine platform * 1 = First generation core designed by the contractor * C = Combustion Engineering (C-E) was the contracted designer The reactor was situated on land and known as the S1C Nuclear Power Training Unit (NPTU). Except for its size and electric drive, the system layout was very similar to the S5W reactor used in most nuclear-powered submarines at the time.