Submarine

This article is about watercraft designed for submerged operation. For other uses, see Submarine (disambiguation).

A submarine (often shortened to sub) is a watercraft that can operate underwater on its own. It is different from a submersible, which has more limited underwater abilities. Sometimes the word "submarine" is also used, in history or informally, for remotely operated vehicles and robots, or for smaller vessels such as the midget submarine and the wet sub. No matter their size, submarines are called boats rather than ships.

Experimental submarines were built before the 19th century, but submarine design took off during that century, and several navies adopted them. Submarines were first used widely during World War I (1914–1918), and today many navies, large and small, use them. Military uses include attacking enemy surface ships or other submarines, protecting aircraft carriers, and launching a cruise missile to attack targets on land. They are also used for nuclear deterrence, secret gathering of information, and secretly placing frogmen or special forces. Civilian uses include marine science, salvage, exploration, and inspecting and maintaining underwater facilities. Some submarines are changed for special jobs, such as search-and-rescue and undersea cable repair. They also serve the tourism industry and undersea archaeology. Modern deep-diving submarines come from the bathyscaphe, which developed from the diving bell.

Most large submarines have a long tube-shaped body with rounded or pointed ends. Near the middle, a tall structure holds communication and sensing equipment, as well as periscopes. On modern submarines, this structure is called the "sail" in American English and the "fin" in European English. Earlier designs often had a "conning tower," a separate pressure hull above the main boat that allowed shorter periscopes. A propeller or pump jet sits at the back, along with several control fins. Smaller, deep-diving, and special-purpose submarines may be very different from this traditional design. Submarines dive and rise again by using diving planes and by changing the amount of water and air in their ballast tanks, which affects their buoyancy.

Submarines come in many types and abilities. Some are small and self-contained, carrying only one or two people and running for a few hours. Others can stay underwater for six months, such as the Russian Typhoon class, the biggest submarines ever built. Submarines can reach depths that are beyond what is practical, or even survivable, for human divers. Today, more countries are building and operating submarines than ever before in modern history, and China is leading this surge in construction.

History

Main article: History of submarines

The word submarine means 'underwater' or 'under-sea,' and as a noun it usually refers to a vessel that can travel underwater. People tried to build underwater craft for hundreds of years. In 1620, Cornelis Drebbel, a Dutchman working for James I of England, built a submersible that was moved by oars. The first military submersible was Turtle (1775), a hand-powered device designed by the American David Bushnell. In 1864, the Confederate navy's H. L. Hunley became the first military submarine to sink an enemy vessel. Submarines could not be used routinely by navies until suitable engines were developed.

Military submarines first made a major impact in World War I, when German U-boats were responsible for sinking RMS Lusitania. During World War II, Germany used submarines to try to cut Britain's supply routes by sinking more merchant ships than Britain could replace. The Imperial Japanese Navy operated a very varied fleet, but its submarines were relatively unsuccessful. The United States submarine force was the most effective anti-ship weapon in the American arsenal. After the war, nuclear power partly replaced diesel–electric propulsion, which allowed submarines to stay underwater for weeks or months. In 1959–1960, the first ballistic missile submarines entered service during the Cold War. See also: List of submarines of World War II

Usage

Before and during World War II, submarines were mainly used to attack enemy ships, either on the surface with deck guns or underwater with torpedoes. They were very effective at sinking shipping in both World Wars. Submarines were also used for Mine-laying, for special operations, and for hunting other submarines. Today, a submarine's main protection is staying hidden in the deep ocean. Modern submarines are built to be very quiet, which makes them hard to find, and a stealth submarine can force an enemy to search large areas of ocean.

Most of the world's submarines are military, but some are civilian and used for tourism, exploration, and inspecting oil and gas platforms and pipelines. Some are also used in illegal activities. The first tourist submarine, Auguste Piccard, entered service in 1964 at Expo64. In 1958, USS Nautilus used an inertial navigation system to reach the North Pole.

Technology

See also: Timeline of underwater technology

Further information: Marine propulsion, Air-independent propulsion, Nuclear marine propulsion, and Nuclear submarine

Further information: Diesel–electric powertrain

Main article: Air-independent propulsion

Main articles: Nuclear submarine and Nuclear marine propulsion

Main article: Sonar

Main article: Communication with submarines

A surfaced ship floats because it weighs less than the water it would push aside. To dive, a submarine must become heavier. It does this by filling its ballast tanks with water, and it empties them with air to rise again. Smaller depth control tanks help it keep a steady depth. Moving control surfaces, called diving planes, help the submarine steer up and down while it moves. Modern submarines are shaped like a cigar, a design sometimes called a teardrop hull, which cuts drag when the sub is underwater. The inner pressure hull must be very strong to withstand the water pressure at depth. Most are made of high-strength steel, and a few were built from titanium. Most submarines run on electric motors and batteries underwater, and on combustion engines when they are on the surface. Some large submarines use nuclear power instead.

Submarines carry weapons such as the torpedo, which was invented by Robert Whitehead in 1866. They use sonar to find targets and to listen for other ships. Modern submarines also use the Global Positioning System to check their position. Submarines communicate with distant command centers using radio, and they can stay underwater for months at a time when they have nuclear power or air-independent propulsion. Most modern military submarines make breathing oxygen from fresh water, and they clean the air of gases such as carbon dioxide.

Crew

A typical nuclear submarine has a crew of over 80, while conventional boats usually have fewer than 40. Crew members often work apart from their families for long periods in cramped conditions, and submarines normally keep radio silence to avoid being found. Operating a submarine is dangerous, even in peacetime, and many submarines have been lost in accidents. Most navies once kept women off submarines, even after they allowed women on surface warships. The Royal Norwegian Navy was the first to let women join submarine crews, in 1985, and the Royal Danish Navy followed in 1988. Others followed, including the Swedish Navy, the Royal Australian Navy, the Spanish Navy, the German Navy and the Canadian Navy. In 1995, Solveig Krey of the Royal Norwegian Navy became the first female officer to command a military submarine, HNoMS Kobben. In 2011, the British Defence Secretary Philip Hammond announced that the UK's ban on women in submarines would be lifted from 2013. In the United States, women were first allowed on submarines in 2010 after senior officials, including Ray Mabus, Michael Mullen and Gary Roughead, began work on the change. By late 2011, women were assigned to the USS Wyoming, and in 2013 the Navy announced that the USS Virginia and USS Minnesota would have female crew members by January 2015. In 2020, Japan's national naval submarine academy accepted its first female candidate.

In an emergency, submarines can contact other ships for help, and the crew can leave the vessel. Crew may use escape sets, such as the Submarine Escape Immersion Equipment, and leave through an escape trunk, a small airlock compartment that lets people escape in small groups. To avoid pulmonary barotrauma, a lung injury caused by pressure changes, escapers must keep an open airway and breathe out as they rise. Escapers from a pressurized submarine can still develop decompression sickness when they return to normal air pressure. Another option is a deep-submergence rescue vehicle, which can dock onto a disabled submarine and carry people out at the same pressure as inside. If the submarine is pressurized, survivors can enter a decompression chamber on a submarine rescue ship and transfer under pressure for safe surface decompression.