The UGM-89 Perseus was a proposed U.S. Navy submarine-launched anti-ship (AShM) and anti-submarine (ASW) cruise missile that was developed under the Submarine Tactical Missile (STAM) project, which was also referred to as the Submarine Anti-ship Weapon System (STAWS).
This missile system was to be the centerpiece for a proposed third-generation nuclear-powered cruise missile submarine championed by then-Vice Admiral Hyman G. Rickover, the influential but controversial head of the Navy's nuclear propulsion program.
[3][4] The Navy issued the STAM requirement in March 1969, and the Lockheed Missiles and Space Company (LMSC) responded to this proposal, which included the formation of an undersea warfare program organization in Sunnyvale, California.
[5][8] Because of its large size, the UGM-89 Perseus missile could not be launched from the Navy's standard 21 in (530 mm) submarine torpedo tubes, but would be carried in a vertical launching system (VLS) housed within the proposed cruise missile submarine's hull.
[2][5] By 1971, the STAM project had evolved into a long-range Advanced Cruise Missile (ACM) program capable of undertaking a variety of combat missions, including strategic nuclear strike (see table below).