After 1947, BuShips purchased ships for the Departments of the Army and the Air Force, coordinated Department of Defense (DOD) shipbuilding activities, and coordinated navy repair and conversion programs with other federal agencies. By 1949 the Naval Reactors branch of BuShips had been established under Hyman G. Rickover, which resulted in the highly successful naval nuclear power program. By 1955 Naval Reactors had developed the first nuclear-powered submarine, followed by the first nuclear-powered ballistic missile submarine in 1960, with other BuShips branches responsible for the non-nuclear portions of those submarines. In the 1950s BuShips was responsible for procuring the first supercarriers such as the and developing new ship types to carry naval surface-to-air missiles, notably guided missile "frigates" (hull classification symbol DLG) such as the .