A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability. The term submarine most commonly refers to a large crewed autonomous vessel; however, historically or more casually, submarine can also refer to medium-sized or smaller vessels (midget submarines, wet subs), remotely operated vehicles or robots.
The noun submarine evolved as a shortened form of submarine boat. For reasons of naval tradition, submarines are usually referred to as "boats" rather than as "ships", regardless of their size.
History
The first military submarine was Turtle (1775), a hand-powered device designed by David Bushnell to attach explosive charges to ships in a harbor. The first military submarine to sink a warship was H.L. Hunley, a Confederate submarine that sank the Union sloop-of-war Housatonic on February 17, 1864, though the Hunley was also lost, apparently shortly after the attack.
More sophisticated submarines were built during the late 19th century. The development of effective submarine designs was driven by inventors including John Philip Holland and Simon Lake, whose designs were adopted by many navies.
Types of Submarines
- Attack submarines (SSN) — Nuclear-powered submarines designed to destroy enemy submarines and surface ships
- Ballistic missile submarines (SSBN) — Nuclear-powered submarines carrying intercontinental ballistic missiles for nuclear deterrence
- Cruise missile submarines (SSGN) — Submarines armed with cruise missiles for land-attack and anti-ship missions
- Diesel-electric submarines (SS/SSK) — Conventional submarines powered by diesel engines on the surface and electric batteries submerged
Design Principles
Modern submarines are cigar-shaped, with a rounded bow and a tapered stern. The hull is designed to minimize hydrodynamic drag while submerged. Submarines use ballast tanks to control their buoyancy: flooding the tanks with water causes the submarine to dive, while blowing compressed air into the tanks forces the water out, causing the submarine to surface.
Early submarines used a hand-cranked propeller or, later, an open bottom, lowered into the water.