I.

Introduction

Submarine, naval vessel designed principally for underwater operations and equipped with guided missiles and torpedoes as its basic weapons.

The modern submarine is a watertight craft with a welded, cigar-shaped hull. Most of it is occupied by the pressure hull, an inner chamber designed to withstand the tremendous pressures experienced at great ocean depths; the remainder consists of an outer chamber that houses ballast tanks. Rising from the hull is a structure called the sail. Known as the conning tower on older submarines, the sail of a modern nuclear submarine houses periscopes, radar and radio masts, snorkel, and diving planes. During surface operation the sail serves as the vessel’s bridge. When submerged, the functions of the bridge are transferred to the control room, which is located in the pressure hull directly below the sail.

To submerge the submarine, water is admitted to the ballast tanks in sufficient quantities to sink it to the desired depth. Resurfacing is accomplished by the use of compressed air to force the water out of the tanks. At the bow or sail, and at the stern, are horizontal rudders, known as diving planes, which give the vessel longitudinal stability when diving or rising.

The main tactical weapon of most submarines that serve as attack boats is the torpedo, launched from torpedo tubes in the bow. The main weapon of missile boats is the medium- or long-range intercontinental ballistic missile (ICBM), fired from vertical tubes located amidships.

II.

Early History

The first successful underwater craft was a leather-encased wooden rowing boat, built in England in the 1620s by the Dutch inventor Cornelis Drebbel. The vessel carried 12 oarsmen and several passengers below the surface of the Thames in a series of trips lasting several hours. Drebbel reputedly used air tubes supported on the surface of the water by floats to replenish the oxygen supply while the boat was underwater.

The first submarine to be used as an instrument of war was an egg-shaped craft, which carried only one crew member. Called Bushnell’s turtle, it was invented in the 1770s by an American engineer, David Bushnell. This craft was propelled by hand-operated screw-like devices; it submerged when a valve admitted sea water into a ballast tank and rose when the tank was emptied by a hand pump. Lead ballast kept the boat upright. Because it lacked an underwater supply of oxygen, the boat could remain submerged for only half an hour. During the American War of Independence it was used in an unsuccessful attack on a British ship anchored in New York Harbor.

In 1800 the American inventor Robert Fulton built a 6.4-m (21-ft) submarine, the Nautilus, which was similar in shape to the modern submarine and included two important innovations: rudders for vertical and horizontal control and compressed air as an underwater supply of oxygen. When submerged, the Nautilus was powered by a hand-operated, four-blade propeller. On the surface the boat was propelled by means of sails attached to a folding mast.

Four submersible vessels were built during the American Civil War by Confederate forces for use against the Union fleet.

In the latter half of the 19th century many attempts were made to develop an adequate means of submarine propulsion. Inventors experimented with compressed air, steam, and electricity as power sources. The first practical submarine with an efficient source of power, developed by the American inventor John Philip Holland, was powered by a dual-propulsion system. Launched in 1898, the submarine, which had an overall length of 16.2 m (53 ft), was equipped with a petrol-driven engine for surface cruising and an electric motor for underwater power.

III.

20th Century

The American engineer Simon Lake made several contributions to the development of the modern submarine, designing the free-flooding superstructure in 1898. In 1906 German engineers adapted the diesel internal-combustion engine to the submarine. With the development of the periscope and the self-propelled torpedo, the submarine became a formidable factor in naval warfare. The effectiveness of the underwater craft as a deadly weapon was first demonstrated during World War I, when German submarines, known as U-boats, were used extensively against Allied warships and merchant vessels. Their success led to the development of depth charges that were launched from surface vessels.

Between World War I and World War II various improvements were made in submarine design and operation. Underwater sound devices for sonar and ultrasonics were developed for communications and the detection of enemy ships. Rescue devices, such as the lightweight breathing apparatus called the Momsen lung, became standard equipment for crews in case of emergency.

By World War II a typical submarine had a surface speed of about 18 knots using diesel engines and a submerged speed of 8 knots using electric motors. In operating submerged the range was limited by storage-battery power, and the submarine was forced to surface periodically in order to recharge its batteries.

During World War II the German navy developed the snorkel, a device which permits the submarine to recharge its batteries while cruising at periscope depth. The snorkel consists of a long tube extending above the surface of the sea; in the tube are inlet ducts to supply air to the diesel engines and outlet ducts to carry off the engine-exhaust gases. The snorkel increased the underwater range of the submarine enormously. In 1950 a snorkel-equipped submarine set a distance record for underwater navigation by sailing submerged from Hong Kong to Honolulu, a distance of about 8,370 km (5,200 mi) in 21 days.

A new type of hull, shaped like a blimp, was introduced in the USS Albacore, launched in 1953. This hull design proved so successful in providing greater submerged speeds that the teardrop-hull configuration was utilized in nearly all subsequent submarine construction.

In 1954 the British navy launched HMS Explorer, which was powered by turbines using hydrogen peroxide fuel, which greatly extended the underwater range.

IV.

Nuclear Submarines

The most revolutionary development in the science of underwater navigation was the application of nuclear energy to submarine propulsion. The first nuclear-powered submarine, the USS Nautilus, was launched in 1954 and commissioned the following year. In a trial run conducted in 1955, the Nautilus sailed totally submerged from New London, Connecticut, to San Juan, Puerto Rico—a distance of 2,170 km (1,350 mi) in 84 hours. Its cruising speed submerged was more than 20 knots for an almost unlimited range. Early in August 1958 the Nautilus made the first undersea transit of the North Pole, cruising under the polar ice pack from Point Barrow, Alaska, to a point between Spitsbergen, Norway, and Greenland.

The USS Skipjack, launched in 1956, combined nuclear propulsion with the blimpish hull form of the Albacore and a single propeller. Advanced versions of this submarine, known as the Thresher class, were placed in operation in the early 1960s. In 1963 the USS Thresher was lost, with 129 men on board, during deep-diving tests in the Atlantic. The tragedy prompted extensive investigation and resulted in innovations in submarine design and undersea rescue technology, making deep-sea exploration and diving safer ventures in the future. The United States has more than 100 submarines in operation, almost all of them nuclear-powered. Most are equipped with a nuclear reactor designed to provide propulsion for at least 640,000 km (400,000 mi) without refuelling.

V.

Submarine-Launched Ballistic Missiles

In 1960 the first submarines incorporating a battery of solid-propellant submarine-launched ballistic missiles (SLBM) with nuclear warheads were built in the United States. Known as the Polaris missile, this weapon was capable of striking targets about 4,000 km (2,500 mi) from a submerged nuclear-fuelled ballistic-missile submarine (SSBN). In the mid-1960s a long-range, inertially guided antisubmarine missile was developed that could be launched underwater from the torpedo tubes of a submarine. In the late 1960s the Polaris missile was replaced on some submarines by Poseidon, a new longer-range SLBM, capable of carrying up to ten nuclear warheads.

The Trident I and II systems are the successors to Polaris and Poseidon. They include the new US Ohio class of nuclear submarine equipped with 24 launching tubes, each containing an intercontinental ballistic missile with a range of 7,400 km (4,600 mi). The Trident C-4 and the longer-range Trident D-5 SLBM have replaced Polaris and Poseidon on 17 US ballistic missile submarines.

Britain has 4 SSBNs, each carrying 16 Vanguard-class US-produced Trident D-5 missiles. While the Trident I (or C-4) missile can deliver eight independently targetable 100-kiloton nuclear warheads, Trident II (or D-5) carries some ten 475-kiloton warheads and has a range of 11,300 km (7,000 mi). Britain’s Vanguard submarines have been built to carry Trident II with British-made warheads. All tactical (short-range) nuclear warheads have been withdrawn from ships and submarines.