Mousetrap (anti-Submarine Projector, Marks 20 and 22) was an anti-submarine rocket launcher used mainly during World War II by the United States Navy^[1] and Coast Guard.^[2] Its development began in 1941 as a replacement for Hedgehog anti-submarine mortar. Those were spigot-launched, which placed considerable strain on the launching vessel's deck, whereas Mousetrap was rocket-propelled. As a result, Mousetrap's four or eight rails for 7.2-inch (183 mm) rockets saved weight and were easier to install.

The rockets weighed 65 pounds (29 kg) each, with a 33-pound (15 kg) Torpex warhead and contact pistol, exactly like Hedgehog.^{[citation needed]}

By the end of the war, over 100 Mark 22 Mousetraps were mounted in U.S. Navy ships, including three each on 12 destroyers,^[1] and submarine chasers (usually two sets of rails).^[3]

• Round weight: 65 lb (29 kg)
• Warhead: 33 lb (15 kg)
• Range: about 280 m (920 ft)
• Firing speed: one round every 3 seconds (maximum)
• No. of rails:
  • Mark 20: 4
  • Mark 22: 8

• Fitzsimons, Bernard, ed. (1978). "Mousetrap". The Illustrated Encyclopedia of Twentieth Century Weapons and Warfare. Vol. 18. London: Phoebus Publishing. pp. 1946–1947. OCLC 271437802.

• ASW Weapons of the United States of America at NavWeaps
• ASW Weapons of World War II of Russia / USSR at NavWeaps