The RUR-4 "Weapon Alpha" (originally Weapon Able) was an American naval

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 ahead-throwing ASW rocket launcher

Multiple rocket launcher

A multiple rocket launcher is a type of unguided rocket artillery system. Like other rocket artillery, multiple rocket launchers are less accurate and have a much lower rate of fire than batteries of traditional artillery guns...

.

Similar to the earlier American Mousetrap

Mousetrap (weapon)

Mousetrap was an anti-submarine rocket used mainly during the Second World War by the U.S. Navy and the U.S. Coast Guard. Its development was begun in 1941 as a replacement for Hedgehog, a British-made projector, which was the first ahead-throwing ASW weapon...

, 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

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, in response to the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 Type XXI

German Type XXI submarine

Type XXI U-boats, also known as "Elektroboote", were the first submarines designed to operate primarily submerged, rather than as surface ships that could submerge as a means to escape detection or launch an attack.-Description:...

 U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

. Begun in a crash program in 1944-5 and put in service before undergoing operational evaluation, it emerged in 1950 as a 227 kg (500lb) 127mm (5") rocket

Rocket

A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

 with a 113 kg (250lb) warhead that sank at 12m/s (40ft/s) (compared to a depth charge

Depth charge

A depth charge is an anti-submarine warfare weapon intended to destroy or cripple a target submarine by the shock of exploding near it. Most use explosives and a fuze set to go off at a preselected depth in the ocean. Depth charges can be dropped by either surface ships, patrol aircraft, or from...

, which sank at between 2.7-5m/s {8.9-16.5ft/s}), an influence

Influence

Influence may refer to:In science and technology:*Sphere of influence , the region around a celestial body in which it is the primary gravitational influence on orbiting objects...

 or time

Timer

A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass.Timers can be mechanical, electromechanical,...

 pistol

Pistol (disambiguation)

A pistol is a small handheld firearm but may also refer to:* Magnetic pistol, on a naval mine or torpedo, for detonation near a target * Pistol squat, variant of lower body exercise used in strength training...

, and a range of 360-730m (400-800yd).