Vought SSM-N-9 Regulus II

The Vought SSM-N-9 Regulus II was a guided supersonic cruise missile armed with a nuclear warhead, meant to be launched from surface ships and submarines of the United States Navy. The Navy wanted it as the successor to the Regulus I, whose radio-command guidance needed a constant link to the launch ship and whose short range kept that ship exposed. The Regulus II used inertial navigation, better aerodynamics and more fuel, and its prototype first flew in May 1956; later test missiles used a General Electric J79 turbojet with a solid-fueled rocket booster. Forty-eight prototype test flights were flown, and the only submarine launch came from USS Grayback in September 1958. The program was terminated on 19 November 1958 in favor of the Polaris submarine-launched ballistic missile, when Vought had completed 20 missiles. Surviving missiles were converted into KD2U-1 supersonic target drones, later designated MQM-15A.