The modern torpedo is a self-propelled weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with its target or in proximity to it.
Historically, it was called an automotive, automobile, locomotive or fish torpedo; colloquially called a fish. The term torpedo was originally employed for a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate an underwater self-propelled weapon. The original torpedo is a kind of fish: an electric ray.
While the battleship had evolved primarily around engagements between armoured ships with large-caliber guns, the torpedo allowed torpedo boats and other lighter surface ships, submersibles, even ordinary fishing boats or frogmen, and later, aircraft, to destroy large armoured ships without the need of large guns, though sometimes at the risk of being hit by longer-range shellfire.
Today's torpedoes can be divided into lightweight and heavyweight classes; and into straight-running, autonomous homers, and wire-guided. They can be launched from a variety of platforms.
The word torpedo comes from the name of a genus of electric rays in the order Torpediniformes, which in turn comes from the Latin "torpere" (to be stiff or numb). In naval usage, the American Robert Fulton introduced the name to refer to a towed gunpowder charge used by his French submarine Nautilus (first tested in 1800) to demonstrate that it could sink warships.
The concept of a torpedo existed many centuries before it was developed as a working device. A possible early description is found in the works of Syrian engineer Hassan al-Rammah in 1275, who described "an egg which moves itself and burns".
Early naval mines
Although, in modern usage, 'torpedo' refers to an underwater self-propelled explosive, the term was historically also applied to primitive naval mines. These were used on an ad hoc basis during the early modern period up to the late 19th century. Early spar torpedoes were created by the Dutchman Cornelius Drebbel in the employ of King James I of England; he attached explosives to the end of a beam affixed to one of his own submarines and they were used (to little effect) during the English expeditions to La Rochelle in 1626.
An early submarine, the Turtle, attempted to lay a bomb with a timed fuse on the hull of HMS Eagle, but failed in the attempt. In 1800, the American inventor Robert Fulton, while working in France, coined the term torpedo in reference to the explosive charges he outfitted his submarine Nautilus with, which he then offered to the French government and British government, both of whom were uninterested.
Torpedoes were used by the Russian Empire during the Crimean War in 1855 against British warships in the Gulf of Finland. They used an early form of chemical detonator.
During the American Civil War, the term torpedo was used for what is today called a contact mine, floating on or below the water surface using an air-filled demijohn or similar flotation device. These devices were very primitive, and were apt to prematurely explode. They would be detonated on contact with the ship, or after a set time, although electrical detonators were also occasionally used. The USS Cairo was the first warship to be sunk on 1862 by an electrically detonated mine. Spar torpedos were also used; an explosive device was mounted at the end of a spar up to 30 feet (9.1 m) long projecting forward underwater from the bow of the attacking vessel, which would then ram the opponent with the explosives. These were used by the Confederate submarine H. L. Hunley to sink the USS Housatonic although the weapon was apt to cause as much harm to its user as to its target.
Invention of the modern torpedo
Following the invention of the Whitehead torpedo by British engineer Robert Whitehead in 1866, the word torpedo came to describe self-propelled projectiles that traveled under or on water. By the turn of the 20th century, the term no longer included mines and booby-traps as the navies of the world added submarines, torpedo boats and torpedo boat destroyers to their fleets.
A prototype self-propelled torpedo was created by a commission placed by Giovanni Luppis, an Austrian naval officer from Rijeka, a port city of the Austro-Hungarian Monarchy, and Robert Whitehead, an English engineer who was the manager of a town factory. In 1864, Luppis presented Whitehead with the plans of the salvacoste (coastsaver), a floating weapon driven by ropes from the land that had been dismissed by the naval authorities due to the impractical steering and propulsion mechanisms.
Whitehead was unable to improve the machine substantially, since the clockwork motor, attached ropes, and surface attack mode all contributed to a slow and cumbersome weapon. However, he kept considering the problem after the contract had finished, and eventually developed a tubular device, designed to run underwater on its own, and powered by compressed air. The result was a submarine weapon, the Minenschiff (mine ship), the first modern self-propelled torpedo, officially presented to the Austrian Imperial Naval commission on December 21, 1866.
The first trials were not successful as the weapon was unable to maintain a course on a steady depth. After much work, Whitehead introduced his "secret" in 1868 which overcame this. It was a mechanism consisting of a hydrostatic valve and pendulum that caused the torpedo's hydroplanes to be adjusted so as to maintain a preset depth.
Torpedo boats and guidance systems
Ships of the line were superseded by ironclads, large steam powered ships with heavy gun armament and heavy armour, in the mid 19th century. Ultimately this line of development lead to the dreadnought category of all-big-gun battleship, starting with HMS Dreadnought.
Although these ships were incredibly powerful, the new weight of armour slowed them down, and the huge guns needed to penetrate that armour fired at very slow rates. This allowed for the possibility of a small and fast ship that could attack the battleships, at a much lower cost. The introduction of the torpedo provided a weapon that could cripple, or sink, any battleship.
The first boat designed to fire the self-propelled Whitehead torpedo was HMS Lightning, completed in 1877. The French navy followed suit in 1878 with Torpilleur No 1, launched in 1878 though she had been ordered in 1875. The first torpedo boats were built at the shipyards of Sir John Thornycroft, and gained recognition for their effectiveness.
At the same time inventors were working on building a guided torpedo. Prototypes were built by John Ericsson, John Louis Lay, and Victor von Scheliha, but the first practical guided missile was patented by Louis Brennan, an emigre to Australia, in 1877.
It was designed to run at a consistent depth of 12 feet (3.7 m), and was fitted with an indicator mast that just broke the surface of the water; at night the mast had a small light fitted which was only visible from the rear. Two steel drums were mounted one behind the other inside the torpedo, each carrying several thousands yards of high-tensile steel wire. The drums were connected via a differential gear to twin contra-rotating propellers. If one drum was rotated faster than the other, then the rudder was activated. The other ends of the wires were connected to steam-powered winding engines, which were arranged so that speeds could be varied within fine limits, giving sensitive steering control for the torpedo.
The torpedo attained a speed of 20 knots (23 mph) using a wire .04 inches (1.0 mm) in diameter but later this was changed to .07 inches (1.8 mm) to increase the speed to 27 knots (31 mph). The torpedo was fitted with elevators controlled by a depth-keeping mechanism, and the fore and aft rudders operated by the differential between the drums.
Brennan travelled to Britain, where the Admiralty examined the torpedo and found it unsuitable for shipboard use. However, the War Office proved more amenable, and in early August 1881 a special Royal Engineer committee was instructed to inspect the torpedo at Chatham and report back directly to the Secretary of State for War, Hugh Childers. The report strongly recommended that an improved model be built at government expense. In 1883 an agreement was reached between the Brennan Torpedo Company and the government. The newly appointed Inspector-General of Fortifications in England, Sir Andrew Clarke, appreciated the value of the torpedo and in spring 1883 an experimental station was established at Garrison Point Fort, Sheerness on the River Medway and a workshop for Brennan was set up at the Chatham Barracks, the home of the Royal Engineers. Between 1883 and 1885 the Royal Engineers held trials and in 1886 the torpedo was recommended for adoption as a harbour defence torpedo. It was used throughout the British Empire for more than fifteen years.
Around 1897, Nikola Tesla patented a remote controlled boat and later demonstrated the feasibility of radio-guided torpedoes to the United States military, only to be turned down.