History Submarine torpedo
Prior to the invention of the self-propelled torpedo, the term was applied to any number of different types of explosive devices, generally having the property of being secret or hidden, including devices which today would include booby traps, land mines, naval mines, and others.
Much like the invention of the helicopter, the earliest torpedo concepts existed many centuries before being developed as working devices. The earliest known description is found in the work of Syrian engineer Hassan al-Rammah in 1275. His works show illustrations of a rocket-propelled device that appears to have been designed to move on the surface of water.
Early naval "torpedoes"
Although the term "torpedo" was not coined until 1800, the early submarine Turtle attacked using an explosive very similar in intent and function. Turtle dived under a British vessel to attach a bomb by means of an auger. The bomb was to be detonated by a timed fuse, probably a type of clockwork mechanism. In its only recorded attack, Turtle failed to penetrate the hull of HMS Eagle, which had been copper-plated to resist shipworms.
The first usage of the term torpedo to refer to a naval explosive was by American inventor Robert Fulton. In 1800, Fulton launched his submarine, Nautilus, and demonstrated its method of attack using a floating explosive charge Fulton called a torpedo. The submarine would tow the torpedo, submerging beneath an enemy vessel and dragging the torpedo into contact with it. Fulton successfully destroyed demonstration targets in both France and Britain, but neither government was interested in purchasing the vessel and Fulton's experiments ceased in 1805.
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. (As self-propelled torpedoes were developed the tethered variety became known as stationary torpedoes and later mines.) Several types of naval "torpedo" were developed and deployed, most often by the Confederates, who faced a severe disadvantage in more traditional warfare methods.
In this period, "torpedoes" floated freely on the surface or were bottom-moored just below the surface. They were detonated when struck by a ship, or after a set time, but were unreliable. These could be as much a danger to Confederate as to Union shipping, and were sometimes marked with flags that could be removed if Union attack was deemed imminent. Rivers mined with Confederate torpedoes were often cleared by Unionists placing captured Confederate soldiers with knowledge of the torpedoes' location in small boats ahead of the main fleet.
"Torpedoes" (mines) could also be detonated electrically by an operator on shore (as demonstrated also by Fulton), so friendly vessels or low-value enemy vessels could be ignored while waiting for the capital ships to sail over them. However, the Confederacy was plagued by a chronic shortage of materials including platinum and copper wire and acid for batteries, and the wires had a tendency to break. Electricity was a new technology, and the limitations of direct current for effective distance was poorly understood, so failures were also possible because of the decrease in voltage when the torpedoes were placed too far from the batteries. Former United States Navy Commander Matthew Maury, who served as a commander in the Confederate Navy, worked on the development of an underwater electrical mine.
David Farragut encountered tethered and floating contact mines in 1864 at the American Civil War Battle of Mobile Bay. After his leading ironclad, USS Tecumseh, was sunk by a tethered contact mine (torpedo), his vessels halted, afraid of hitting additional torpedoes. Inspiring his men to push forward, Farragut famously ordered, "Damn the torpedoes, full speed ahead!"
The first torpedo designed to attack a specific target was the spar torpedo, an explosive device mounted at the end of a spar up to 40 feet (12 m) long projecting forward underwater from the bow of the attacking vessel. When driven up against the enemy and detonated, a hole would be caused below the water line. Spar torpedoes were employed by the Confederate submarine H. L. Hunley, as well as by David-class torpedo boats, among others. However, these torpedoes were liable to cause as much harm to their users as to their targets.