A submarine is a specialized ship that travels under water, usually for military purposes. Most major navies of the world employ submarines. Submarines are also used for marine and freshwater science and for work at depths too great for human divers. A U-Boat is an alternative name for a submarine (Unterseeboot), but it is mainly given to German submarines since WWII, being the German translation of the same. Another submaritime device is the diving bell.


Table of contents
1 Scientific and commercial submarines
2 Military submarines
2.1 Types of military submarines
2.2 History of military submarines


Scientific and commercial submarines
In common usage, submarine normally means military submarine; vessels used for research or commercial purposes are usually called submersibles. Non-military submarines are usually much smaller than military submarines. A type called a bathysphere lacks self-propulsion. A predecessor of the bathysphere, the diving bell, consisted of a chamber, with an open bottom, lowered into the water.

The first mechanically powered submersible was the steam driven Ictineo II, built in 1862 by Narcís Monturiol i Estarriol and whose purpose was to ease the harvest of coral.

Tourist submarines work mainly in tropical resort areas. In 1996, there were over fifty private submarines operating around the world, serving approximately two million passengers that year. Most of these submarines carried between twenty-five and fifty passengers at a time and sometimes made ten or more dives a day. In design, these submarines borrow mainly from research subs, having large windows for passengers' viewing and often placing significant mechanical systems outside the hull to conserve interior space. They are mainly battery-powered and very slow.

A fairly recent development, very small unmanned submarines called marine remotely operated vehicles are widely used today to work in water too deep or too dangerous for divers. For example, remotely operated vehicles (ROVs) repair offshore petroleum platforms and attach cables to sunken ships to hoist them. Such remotely operated vehicles are attached by a tether (a thick cable providing power and communications) to control center on a ship. Operators on the ship see video images sent back from the robot and may control its propellers and manipulator arm.


Military submarines
There are probably more military submarines in operation that any other type of submarine, though it is difficult to obtain exact figures because navies are secretive about their submarine fleets.

Submarines are useful to a military because they can approach their attack victim without necessarily being detected, then strike at close range. A great deal of attention in the design of a submarine is devoted to making its travel through the water silent to prevent its detection by enemy ships and submarines. Modern vessels have a cigar-shaped "albacore" shape. Their hulls are sleek and hydrodynamic. They are designed to remain submerged nearly all of the time, surfacing only rarely.

A raised tower on top of a submarine accommodates the length of the periscopes and electronics masts, which can include radio, radar, electronic warfare, and other systems. In the obsolete boat-shaped classes of submarines (see history, below), the control room, or conn, was located inside this tower, which was known as the conning tower. Since that time, however, conn has been located within the main body of the submarine, and the tower is more commonly called the sail today. In another interpretation, conning tower comes from the English verb to con, which means to navigate, indicating the presence of navigational systems in the conning tower. The conn should not be confused with the bridge, which is a small platform set into the top of the sail used for visual observation while running on the surface.

Sonar is a submarine's principal means of short-range submerged navigation. The global positioning system is used for long-range navigation. The periscope is only used occasionally, since the range of visibility below the sea is short.

A typical military submarine has a crew of over one hundred. Their job is one of the most difficult assignments in the navy, for they must work in isolation for long periods, without much contact with their families, since submarines normally maintain radio silence to avoid detection. Operating a submarine is dangerous, even in peacetime; many submarines have been lost in accidents (see history, below).


Types of military submarines
Military submarines come in two general types: ballistic-missile submarines and attack submarines. (Outside these categories may fall the many smaller midget submarines, used for sabotage, espionage and secretive transport. Note that North Korea's submarine fleet, estimated as the fourth-largest in the world in the 1990s, consists largely of smaller vessels. Also outside the two categories fall the World War II German milchcow submarines: submersible supply vessels.)

Ballistic missile submarines (or boomers, in American slang) carry nuclear weapons for attacking strategic targets such as cities or missile silos anywhere in the world. They are universally nuclear-powered, to provide the greatest stealthiness and endurance. They played an important part in Cold War mutual deterrence: since both the United States and the Soviet Union had the capability (or could contend to have) to heavily strike at the attacking nations should one attack the other, both nations were "deterred". China also possesses one ballistic missile submarine (Xia class). The American George Washington-class "boomers" were named for "famous Americans" and the later Ohio-class were named for states, with the exceptions that some of the "famous Americans" were foreigners and SSBN-730 gained the name of a Senator.

Submarines designed for the purpose of attacking merchant ships or other warships are known as attack or hunter-killer submarines. They typically carry torpedoes for attacking naval vessels, and sometimes cruise missiles for attacking land-based targets or shipping. They use a much wider variety of propulsion systems. The majority use the same diesel-electric combination developed early in the 20th century, many use nuclear power, and a growing number use some other form of air-independent propulsion such as fuel cells or Stirling engines. All of the hunter submarines of the United States use nuclear power. All American attack submarines (that had actual names rather than just alphanumeric designators) were named for "denizens of the deep" until the Los Angeles class, which are named for cities -- with the exceptions of several named for politicians, and the new Seawolf, which received the traditional name.


History of military submarines

Though the first submersible vehicles were tools for exploring under water, it did not take long for inventors to recognize their military potential. The first military submarine was the Turtle, a hand-powered spherical contraption designed by American David Bushnell that accommodated a single man. During the American Revolutionary War, the Turtle attempted and failed to sink a British warship, the HMS Eagle in New York harbor on September 7, 1776.

In 1800, Robert Fulton demonstrated the French, and then the British, how to destroy ships with his human-powered submarine "Nautilus", using a mine, but none of the governments showed any interest.

During the American Civil War, the Confederate States of America fielded a human-powered submarine, the CSS Hunley. It was used for attacking the North's ships, which were blockading the South's seaports. The submarine had a long pole on the front, upon which was attached an explosive charge. The sub was to sneak up to an enemy vessel, attach the explosive, move away, and then detonate. It was extremely hazardous to operate, and had no air supply other than what was contained inside the main compartment. On at least one occasion, the sub sank, and the entire crew perished. In 1863 the CSS Hunley sank the USS Housatonic in the Charleston Harbor, the first time a submarine successfully sank another ship. The Hunley did not survive the mission and was not a major factor in the war.

In 1870, writer Jules Verne published the science fiction classic 20,000 Leagues under the Sea, which concerns the adventures of a maverick inventor in a submarine more advanced than any that existed at that time. The fictional story inspired inventors to build submarines. The first mechanically powered military submarine (see Ictineo) was the steam-powered 'Resurgam', designed by a Manchester curate, the Reverend George Garrett, and built at Birkenhead in 1879. Garrett intended to demonstrate the 12 metre long vehicle to the British Navy at Portsmouth, but had mechanical problems, and while under tow the submarine was flooded and sank off North Wales. The first submarine built in series, however, was human-powered. It was the submarine of the Polish inventor Stefan Drzewiecki - 50 units were built in 1881 for Russian government. In 1884 the same inventor built an electric-powered sumbmarine. In 1899, the French steam and electric submarine "Narval" introduced the classic twin-hull design, with an inner hull inside an outer hull. The Irish inventor John Holland had better luck, and designed and built several quite successful gasoline- and electric powered submarines. Some of his vessels were purchased by the United States, the United Kingdom, and Japan, and commissioned into their navies.

Many more submarines were built subsequently by various inventors, but they were not to become effective weapons until the 20th century. Both battery power and gasoline power were tried.

The first military submarines to see effective use were the U-boats of Germany, first introduced in World War I. The innovation that made the U-boats practical war machines was their use of diesel. More like submersible ships than the submarines of today, U-boats operated primarily on the surface, submerging occasionally to attack. Thus, they were roughly triangular in cross-section, with a distinct keel, to control rolling while surfaced. The sinking of the ocean liner RMS Lusitania by a U-boat was a major factor in bringing the United States of America into the war.

Germany again put submarines to devastating effect against the merchant ships of the United Kingdom and the United States during World War II. Although the U-boats were improved, the main reason for their success was the introduction of mass-attack tactics called a pack (in German, Rudel) commonly traveled and fought together. (The term is often translated as "wolf-pack", but the German word does not specify wolves.) Germany attempted to maintain an blockade against the United Kingdom in the Battle of the Atlantic (1940). Although the German blockade was of great concern to Allied forces, they succeeded in blocking only a small fraction of Allied shipping, in part because the Allies had broken the German naval code and German tactics involved broadcasting target information.

Meanwhile the US used their submarines to attack merchant shipping, destroying more Japanese shipping than all other weapons combined. While the British and Japanese also fielded submarines, they were used in fleet actions where they were almost useless due to their low speeds.

In the 1950s, nuclear power partially replaced diesel fuel in those nations with access to nuclear technology. Equipment was also developed to extract oxygen from sea water. These two innovations gave submarines so equipped the ability to remain submerged for weeks or months, and enable previously impossible voyages such as USS Nautilus' crossing of the North pole beneath the Arctic ice cap in 1958. Non-nuclear nations continued to develop conventional forms of propulsion.

During the Cold War, the United States of America and the Soviet Union maintained large submarine fleets that engaged in cat-and-mouse games; Russia continues this tradition today. The Soviet Union suffered the loss of at least three submarines during this period: K-8 was lost in 1970, K-219 in 1986, and Komsomolets in 1989 (which held a depth record among the military submarines - 1000 m). (The loss by Russia, inheritor of the Soviet navy, of Kursk in 2000 cannot be attributed to the Cold War.) Many other Soviet subs, such as K-19 were badly damaged by fire or radiation leaks. The United States lost two nuclear submarines during this time: USS Thresher (SSN-593) and USS Scorpion (SSN-589). Their wrecks remain on the ocean floor with their nuclear reactors and nuclear weapons.

The United Kingdom employed nuclear-powered submarines against Argentina in 1982 during the two nations' dispute over the Falkland Islands. The sinking of the antiquated ARA General Belgrano by HMS Conqueror was the first sinking by a nuclear-powered submarine in wartime.

In 2000, the Russian submarine Kursk sank in the Arctic Ocean; an international rescue effort failed to save the crew. In 2001, the American submarine USS Greeneville accidentally struck and sank a Japanese ship, Ehime-Maru, killing nine Japanese crewmen. In August 2003, the Russian nuclear November class submarine K-159 sank in the Barents Sea. The submarine was decommissioned, and it had only ten crew on board.

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