Torpedo, a self-propelled, cigar-shaped, underwater missile. Torpedoes can be launched from ships, submarines, airplanes, or they can form part of a guided-missile system. They carry either conventional or nuclear explosives and can detonate either on contact or within magnetic range of their target. Torpedoes are intended for underwater attack against either surface ships or submarines.
One of the standard modern torpedoes is the electrically propelled homing torpedo. It consists of five major parts: nose, warhead, battery compartment, afterbody, and tail. Acoustic transmitter-receivers are placed in the nose to home the torpedo to its target by detecting noise generated by the target or echoes received from the target. The warhead contains an explosive charge and exploder mechanism. The battery compartment holds storage batteries that generate current to drive electric motors in the afterbody. The motors, in turn, power the propellers and rudders in the tail. The afterbody, in effect the torpedo's engine room, also contains an electrically operated gyroscope to control the torpedo's course and a depth mechanism to control the depth at which it runs.
To protect the launching vehicle, the torpedo arms itself after it has been fired. A submarine-launched torpedo is usually ejected by compressed air from tubes built in the submarine's structure. Homing torpedoes dropped from airplanes are attached to a parachute to break their fall and protect delicate instruments. Some of the most sophisticated long-range torpedoes launched from surface ships are rocket-assisted torpedoes mounted in an air frame and fired by a rocket motor. An antisubmarine rocket system called ASROC, and a rocket-assisted torpedo that can be launched from a submarine, called SUBROC, are used by the U.S. Navy,.
An American, David Bushnell, conducted many of the earliest experiments with underwater explosives late in the 18th century. His work was continued by Robert Fulton, who named his own underwater mine a torpedo after a small marine worm that attacked the bottom of wood ships. The spar torpedo, an explosive charge attached to a long spar, was used with some success during the Civil War. The first self-propelled torpedo, driven by compressed air, was designed by an English inventor, Robert Whitehead, in 1866. Within two years he perfected a depth mechanism, and within six years he sold rights to produce so-called automobile torpedoes to most of the European powers.