A ship capable of underwater operation. The idea is an old one, but the first working craft was not built until 1620, by Cornelius Drebbel; it was a wooden frame covered with greased leather. The first submarine used in warfare was invented by David Bushnell (1776). It was a one-man, hand-powered, screw-driven vessel supposed to attach mines to enemy ships. In the US Civil War the Confederate States produced several submarines. Propulsion, the major problem, was partly solved by the Rev. G. W. Garrett, who built a steam-powered submarine (1880). In the 1890s John P. Holland and his rival Simon Lake designed vessels powered by gasoline engines on the surface and electric motors when submerged, the forerunners of modern submarines. They were armed with torpedoes and guns.
Great advances were made during World War I and WWII, which demonstrated the submarine's military effectiveness. The German U-boats were notably efficient , and introduced snorkels to hinder detection while recharging batteries. But none of these vessels could remain submerged for very long, and a true (long-term) submarines awaited the advent of nuclear power. The first nuclear-powered submarines was U.S.S. Nautilus (1955), which in 1958 made the first voyage under the polar ice-cap. The US, Russia, UK, and France have nuclear submarine fleets equipped fitted with ballistic missiles.
Modern submarines are streamlined vessels, generally with a double hull, the inner being a pressure hull with fuel and ballast tanks between it and the outer hull. The submarine submerges by flooding its ballast tanks to reach neutral buoyancy, i.e., displacing its own weight of water (see Archimedes' principle, and dives using its hydrofoil diving planes. Submarines are equipped with periscopes and inertial guidance systems. Submarines are also used for oceanographic research and exploration, salvage, and rescue.
A new generation of submersibles has emerged since the late 1950s for engineering and research work. A typical craft has a spherical passenger capsule capable of withstanding water pressure down to about 3,600m (12,000ft). Attached to this is a structure containing batteries, an electric motor with propeller, lighting, a mechanical arm for gathering samples, and other technical equipment. A specially designed support ship launches and retrieves the submersible, Some submersibles are unmanned and operated by remote control from the surface.
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