torpedo, in naval warfare, a self-propelled submarine projectile loaded with explosives, used for the destruction of enemy ships. Although there were attempts at subsurface warfare in the 16th and 17th cent., the modern torpedo had its origin in the efforts of David Bushnell, who, during the American Revolution, experimented with a submarine for attaching underwater explosives to British ships. His attempts failed, but later Robert Fulton experimented with similar ideas. In the 19th cent. torpedoes developed at first as stationary mines placed in the water; these were used extensively by the Russians in the Crimean War and by the Confederacy in the U.S. Civil War. The first truly self-propelled torpedo was designed and built at Fiume in 1866 by Robert Whitehead, an Englishman. It was driven by a small reciprocating engine run by compressed air; a hydrostatic valve and pendulum balance, connected to a horizontal rudder, controlled the depth at which it ran. Directional accuracy was achieved in 1885 when John Adams Howell developed the gyroscope to control the vertical rudder. Torpedoes were used by Japan in the Russo-Japanese War and were widely employed in World War I. The torpedoes used in World War II were usually 20 to 24 ft (6.1–7.3 m) long, carrying up to 600 lb (272 kg) of explosives at a speed of 50 knots for more than 10,000 yd (9,144 m). The type of torpedo used in World War II has been largely superseded by the homing torpedo. In contrast to the older type, which traveled in a straight line on a preset course, the homing torpedo automatically changes its course to seek out its target. Most homing torpedoes are activated by sounds coming from the target (e.g., propeller or machinery noises), and they follow the sounds until making contact with the target. A homing torpedo runs through three phases: the enabling run, which takes it to the vicinity of the target; the search pattern, in which it maneuvers to find the target; and the homing, in which it pursues the target. The modern torpedo is generally propelled by an electric motor, but some of the newer, faster, high-diving torpedoes, designed for effectiveness against nuclear submarines, have solid-propellant-driven turbines. Some also may be equipped with nuclear warheads. Torpedoes can be fired from shore stations, surface vessels, and aircraft, as well as from submarines.
See Bureau of Naval Personnel, Principles of Naval Ordnance and Gunnery (1959); R. Fulton, Torpedo War and Submarine Explosions (1810, repr. 1971).
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