Submarines and their usage

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has only limited underwater capability. The term submarine most commonly refers to large crewed autonomous vessels; 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 word submarine was originally an adjective meaning “under the sea”, and so consequently other uses such as “submarine engineering” or “submarine cable” may not actually refer to submarines at all. Submarine was shortened from the term “submarine boat”.

Experimental sub with hydrofoils in Monterey BaySubmarines are referred to as “boats” for historical reasons because vessels deployed from a ship are referred to as boats. The first submarines were launched in such a manner. The English term U-boat for a German submarine comes from the German word for submarine, U-Boot, itself an abbreviation for Unterseeboot (“undersea boat”).

Although experimental submarines had been built before, submarine design took off during the 19th century. Submarines were first widely used in World War I, and feature in many large navies. Military usage ranges from attacking enemy ships or submarines, aircraft carrier protection, blockade running, ballistic missile submarines as part of a nuclear strike force, reconnaissance, conventional land attack (for example using a cruise missile), and covert insertion of special forces. Civilian uses for submarines include marine science, salvage, exploration and facility inspection/maintenance. Submarines can also be specialised to a function such as search and rescue, or undersea cable repair. Submarines are also used in tourism and for academic research.

Submarines have one of the largest ranges of capabilities in any vessel, ranging from small autonomous examples to one or two-person vessels operating for a few hours, to vessels which can remain submerged for 6 months such as the Russian Typhoon class. Submarines can work at greater depths than are survivable or practical for human divers. Modern deep diving submarines are derived from the bathyscaphe, which in turn was an evolution of the diving bell.

Most large submarines comprise a cylindrical body with conical ends and a vertical structure, usually located amidships, which houses communications and sensing devices as well as periscopes. In modern submarines this structure is the “sail” in American usage (“fin” in European usage). A “conning tower” was a feature of earlier designs: a separate pressure hull above the main body of the boat that allowed the use of shorter periscopes. There is a propeller (or pump jet) at the rear and various hydrodynamic control fins as well as ballast tanks. Smaller, deep diving and specialty submarines may deviate significantly from this traditional layout.

Military usage?
Retractable 7.5 cm submarine gun produced by the Krupp company circa 1900Before and during World War II, the primary role of the submarine was anti-surface ship warfare. Submarines would attack either on the surface or submerged, using torpedoes or (on the surface) deck guns. They were particularly effective in sinking Allied transatlantic shipping in both World Wars, and in disrupting Japanese supply routes and naval operations in the Pacific in World War II.

Mine-laying submarines were developed in the early part of the 20th century. The facility was used in both World Wars. Submarines were also used for inserting and removing covert agents and military forces, for intelligence-gathering and to rescue aircrew during large-scale air attacks on islands, where the airmen would be told of safe places to crash-land damaged aircraft so the submarine crew could rescue them. Submarines could carry cargo through hostile waters or act as supply vessels for other submarines.

Submarines could usually locate and attack other submarines only on the surface, although HMS Venturer (P68) managed to sink U-864 with a four torpedo spread while both were submerged. The British developed a specialised anti-submarine submarine in World War I, the R class. After World War II, with the development of the homing torpedo, better sonar systems, and nuclear propulsion, submarines also became able to hunt each other effectively.

A model of Günther Prien’s U-47, German WWII Type VII diesel-electric hunterThe development of submarine-launched nuclear missiles and submarine-launched cruise missiles gave submarines a substantial and long-ranged ability to attack both land and sea targets with a variety of weapons ranging from cluster bombs to nuclear weapons.

The primary defense of a submarine lies in its ability to remain concealed in the depths of the ocean. Early submarines could be detected underwater by the sound they made. Water is an excellent conductor of sound, and submarines can detect and track comparatively noisy surface ships from long distances. Modern submarines are built with an emphasis on stealth. Advanced propeller designs, extensive sound-reducing insulation, and special machinery allow a submarine to be as quiet as ambient ocean noise, making them extremely difficult to detect. It takes specialized technology to find and attack modern submarines.

Active sonar uses the reflection of a sound emitted from the search equipment to detect submarines. It has been used since World War II by surface ships, submarines or even aircraft, but it gives away the position of the emitter and is susceptible to counter-measures.

A concealed military submarine is a real threat and, because of its stealth, it can force an enemy navy to waste resources searching large areas of ocean and protecting all ships against possible attack. This advantage was vividly demonstrated in the 1982 Falklands War when the British SSN HMS Conqueror sank the Argentine cruiser General Belgrano. After the sinking the Argentine Navy realized that they were vulnerable to submarine attack, and that they had no defense from it. Thus the Argentine surface fleet withdrew to port for the remainder of the war, though an Argentine submarine remained at sea.
Civil Uses?
Although the majority of the world’s submarines are military ones, there are some civil submarines. They have a variety of uses, including tourism, exploration, oil and gas platform inspections and pipeline surveys. The first tourist submarine was launched in 1985, and by 1997 there were 45 of them operating around the world.

A semi-civilian use was the adaption of U-boats for cargo transport during WWI and WWII