Submarine

This article is about boats built to travel underwater. For other uses, see Submarine (disambiguation).

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

People built experimental submarines before the 1800s. Submarines became much more advanced during that century, and several navies began using them. Submarines were first used widely during World War I (1914–1918). Today, many navies, large and small, use them. Navies use submarines to attack enemy surface ships or other submarines, to protect aircraft carriers, and to launch a cruise missile at targets on land. They are also used for nuclear deterrence, gathering information in secret, and secretly placing frogmen or special forces. People also use submarines for marine science, salvage, exploring, and checking and repairing 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 grew 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 look 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 carry only one or two people, and they can run 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 too deep for human divers to reach safely. Today, more countries are building and operating submarines than ever before in modern history, and China is leading this growth.

History

Main article: History of submarines

A submarine is a vessel that can travel underwater. The word means 'underwater' or 'under-sea.' 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 ship. Navies could not use submarines often until good engines were developed.

Military submarines first became important in World War I. German U-boats sank the RMS Lusitania. During World War II, Germany used submarines to try to cut off Britain's supplies by sinking many ships. The Imperial Japanese Navy had many different kinds of ships, but its submarines were not very successful. The United States submarine force was one of the most effective weapons against ships in the American military.

After the war, nuclear power partly replaced diesel–electric engines. This let submarines 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. They could fire from the surface with deck guns, or underwater with torpedoes. They were very good at sinking ships 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, so they are hard to find. A stealth submarine can make an enemy search large areas of ocean.

Most of the world's submarines belong to the military. Some are civilian and are used for tourism, exploration, and checking oil and gas platforms and pipelines. Some are also used in illegal activities. The first tourist submarine, Auguste Piccard, began 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 ship on the surface floats because it weighs less than the water it pushes aside. To dive, a submarine must become heavier. It fills its ballast tanks with water, and it empties them with air to rise again. Smaller depth control tanks help it stay at 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 helps it move through water more easily. The inner pressure hull must be very strong to handle the water pressure deep down. Most are made of strong steel, and a few were built from titanium. Most submarines use electric motors and batteries underwater, and combustion engines 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 where they are. They talk to distant command centers by 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. Conventional boats usually have fewer than 40 crew members. Crew members often live apart from their families for long periods, in tight spaces. Submarines usually keep radio silence so they are not found. Working on a submarine is dangerous, even in peacetime, and many submarines have been lost in accidents. Most navies once did not allow women on submarines, even though they allowed women on surface warships. The Royal Norwegian Navy was the first to let women join submarine crews, in 1985. The Royal Danish Navy followed in 1988. Other navies 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 end from 2013. In the United States, women were first allowed on submarines in 2010. Senior officials, including Ray Mabus, Michael Mullen and Gary Roughead, had started work on the change. By late 2011, women were assigned to the USS Wyoming. 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, a submarine can contact other ships for help. The crew can also leave the vessel. Crew may use escape sets, such as the Submarine Escape Immersion Equipment. They can 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 get decompression sickness when they return to normal air pressure. Another option is a deep-submergence rescue vehicle. It 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. They can transfer under pressure for safe surface decompression.