RUR-4 Weapon Alpha

• Name — Weapon Alpha • Origin — United States • Type — Anti-submarine rocket • Is Missile — yes • Service — 1951–1969 • Used By — United States Navy Japan • Designer — Naval Ordnance Test Station • Design Date — 1946–1949 • Spec Label — Mark 1 • Weight — 525 lb • Length — 2.6 m • Diameter — 12.75 in • Filling — High explosive • Filling Weight — 250 lb • Detonation — Depth charge • Engine — 5.25 in rocket • Vehicle Range — 800 yd • Speed — 190 mph • Propellant — Solid fuel • Launch Platform — Ships

Similar to the earlier American Mousetrap, 375mm (14.8") Swedish Bofors, and 250mm (9.8") and 300mm (11.8") Soviet systems, all of which use multiple rockets, Weapon Alpha was developed toward the end of World War II, in response to the German Type XXI U-boat. Begun in a crash program in 1944–5 and put in service before undergoing operational evaluation, it emerged in 1949 as a 227-kg (500 lb) 127mm (5") rocket with a 113-kg (250 lb) warhead that sank at 12 m/s (40 ft/s) (compared to a depth charge, which sank at 2.7–5 m/s (8.9–16.5 ft/s)), an influence or time pistol, and a range of 360–730 m (400–800 yd). Coupled to the new SQG-1 depth-finding sonar (for setting the time fuse, rather than the hydrostatic pistol of a depth charge), it was to be fired from a revolving Mark 108 launcher (with 22 rounds of ready ammunition) at up to twelve rounds per minute. The ready-service magazine could not be reloaded while Weapon Alpha was in use. It was replaced by the RUR-5 ASROC, which was developed by the U.S. Navy in the 1950s. Nonetheless, Weapon Alpha remained in service through the 1960s until supplanted by ASROC.

• Illustration — A dismounted Mk 108 launcher at the Intrepid Sea-Air-Space Museum. • Illustration — The RUR-4's rocket round. • Illustration — RUR-4 launch from Wilkinson, 1956.