As the torpedo increased in capability, it naturally grew in size: by 1912, the 18‐inch Mark 7 measured 17 feet in length, weighed 1,628 pounds, and carried a warhead of 326 pounds of TNT to a range of 6,000 yards at 35 knots. In 1914, the navy settled on a diameter of 21 inches for most of its new torpedoes—a standard that endured for the rest of the century.
Over the interwar period, Newport, under the guidance of the talented mechanical engineer and submariner Ralph Waldo Christie, pushed ahead with a number of advanced concepts: exotic propulsion systems using oxygen, hydrogen peroxide, or electric motors to give wakeless runs; large, air‐dropped torpedoes; and magnetic exploders to increase lethality by detonating the torpedo under its target. As financial constraints prevented the navy from pursuing all of these promising leads, it concentrated on the last two. Introduced in 1936 was the Mark 13 air‐dropped weapon, which imposed severe speed and altitude restrictions on the aircraft carrying it. Also flawed was the new Mark 6 magnetic exploder. Expensive and highly secret, it entered the inventory in the 1930s, but was neither tested extensively nor issued to the fleet until 1941.
World War II put U.S. torpedoes to the operational test for the first time, and they were found wanting. Following the Japanese attack on Pearl Harbor, U.S. destroyers, submarines, and aircraft were all hobbled by torpedo problems. American torpedo bombers at Midway suffered appalling losses as they made their low‐level attacks. The Mark 6 exploder frequently failed, and its backup contact pistol proved too fragile. The Mark 14 submarine torpedo, introduced in 1931, left a prominent wake, tended to run deep, and sometimes even circled. A series of distressing incidents highlighted the problems. Tang, one of the most successful submarines, was sunk by its own weapon. Two destroyers, ordered to scuttle the damaged Hornet after the Battle of Santa Cruz, fired sixteen torpedoes at the carrier without sinking it. In a particularly damning episode on 24 July 1943, the submarine Tinosa shot fifteen torpedoes into the largest tanker in the Japanese merchant fleet; only four exploded.
Hurried remedial measures developed by the navy, the scientific community, and industry resolved the difficulties. Aircraft torpedoes were modified so that they could be dropped at much faster speeds and higher altitudes. The Mark 6 magnetic exploder was deactivated. New types of torpedoes were hurried into production, the most important being the Mark 18 electric and the homing types. The former, built by Westinghouse and introduced in September 1943, offered the great advantage of leaving no bubble trail. By 1945, 65 percent of all shots were by electrics. Also strikingly successful was the acoustic homing torpedo developed by Bell Labs, General Electric, and Harvard for antisubmarine work. Dubbed for security reasons the Mine Mark 24, the torpedo followed sound pulses to its underwater target. Beginning in May 1943, the air‐dropped Mark 24, nicknamed “Fido,” sank thirty‐one submarines; its surface ship variant claimed thirty‐three additional victims.
Wartime expenditure of torpedoes was prodigious. U.S. submarines fired 14,748 torpedoes, sinking 214 warships and 1,178 merchant vessels. U.S. aircraft made 1,287 attacks, scoring 514 hits. Overall, about 33 percent of torpedoes fired hit their targets. The navy kept up with mushrooming demand by reopening its World War I facility at Alexandria, Virginia, and by contracting with private firms (Bliss, Pontiac, and Westinghouse). Overall production totaled 57,655 torpedoes between 1 January 1939 and 1 June 1946.
Although the last U.S. operational use of torpedoes came on 1 May 1951, when navy planes breached the Hwachon dam in North Korea during the Korean War, development of the weapon continued apace, largely to match increasingly capable Soviet nuclear submarines. On operational service from 1958 to 1977 was the Mark 45 Astor, with a nuclear warhead. By the 1990s, two types remained in service: the 3,450‐pound Mark 48 (range 35,000 yards, speed 55 knots, depth over 2,500 feet) and the Mark 46 lightweight torpedo for close‐in use by aircraft or surface ships.
[See also Navy, U.S.: 1899–1945; Navy, U.S.: Since 1946; Navy Combat Branches: Submarine Forces.]
Buford Rowland and and William B. Boyd , U.S. Navy Bureau of Ordnance in World War II, 1953.
Norman Friedman , U.S. Naval Weapons, 1983.
John Campbell , Naval Weapons of World War Two, 1985.
Edwyn Gray , The Devil's Device: Robert Whitehead and the History of the Torpedo, 1991.
Robert Gannon , Hellions of the Deep: The Development of American Torpedoes in World War II, 1996.
Malcolm Muir, Jr.
tor·pe·do / tôrˈpēdō/ • n. (pl. -does) 1. a cigar-shaped self-propelled underwater missile designed to be fired from a ship or submarine or dropped into the water from an aircraft and to explode on reaching a target. ∎ a signal placed on a railroad track, exploding as the train passes over it. ∎ a firework exploding on impact with a hard surface. ∎ inf. a submarine sandwich. ∎ inf. a gangster hired to commit a murder or other violent act. ∎ an explosive device lowered into oil wells to clear obstructions.2. (also tor·pe·do ray) an electric ray.• v. (-does, -doed) [tr.] attack or sink (a ship) with a torpedo or torpedoes. ∎ fig. destroy or ruin (a plan or project): fighting between the militias torpedoed peace talks.DERIVATIVES: tor·pe·do·like / -ˌlīk/ adj.