Submarine

• 1. Introduction

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  The submarine has carried human beings into a realm that, for most of history, was completely out of reach. In 1960, Jacques Piccard and Lieutenant Don Walsh of the US Navy descended in the vessel Trieste to the floor of the Challenger Deep, the deepest southern part of the Mariana Trench, at a depth the onboard systems recorded as 11,521 meters. No crewed or uncrewed vessel had ever reached that point in the Earth's oceans before. That single descent captures something essential about the submarine: it is a machine built to survive where nothing else can go.

  Yet the submarine is also a weapon of extraordinary consequence. During World War II, German U-boats came close to strangling Britain's Atlantic supply lines. American submarines, though representing only about two percent of the US Navy, destroyed over thirty percent of the Japanese Navy and more than sixty percent of Japan's merchant fleet. The question of how a leaky, hand-powered wooden vessel of the seventeenth century became that kind of force is one of the most surprising stories in the history of technology.

  The story moves through centuries of experiment, failure, and sudden breakthrough. It passes through a Dutch inventor in the service of a Stuart king, through an Irish-American designer who sold his boat to the United States Navy for the first time in 1900, through the encrypted signals of the Enigma machine and the tactics that broke them. What drives the whole arc is a deceptively simple idea: a vessel that disappears beneath the surface becomes almost impossibly difficult to find and destroy.

• 2. Early Experiments

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  In 1562, an account in Opusculum Taisnieri described two Greeks submerging and resurfacing in the river Tagus near Toledo in the presence of the Holy Roman Emperor Charles V, carrying flames that reportedly stayed alight. Whether the report is fully reliable is uncertain, but it signals how old the fascination with underwater travel is.

  The first recorded plan for an underwater navigation vehicle came from the English mathematician William Bourne, who wrote it down in 1578. A few decades later, the Spanish designer Jerónimo de Ayanz y Beaumont, who lived from 1553 to 1613, went considerably further: he produced detailed drawings for two types of air-renovated submersible equipped with oars, autonomous floating snorkels driven by inner pumps, portholes, and gloves for manipulating objects underwater. His stated purpose was warfare: approaching enemy ships undetected and attaching timed gunpowder charges to their hulls.

  The first submersible for which reliable construction records exist was built in 1620 by Cornelis Drebbel, a Dutchman working in the service of King James I of England. It was propelled by oars. By the mid-eighteenth century, more than a dozen patents for submersible boats had been granted in England alone. In 1747, Nathaniel Symons patented the first known working example of a ballast tank for submersion, using leather bags that could fill with water to take the craft down and be wrung out to bring it back up.

  The first American military submersible arrived in 1775: a hand-powered, acorn-shaped device designed by David Bushnell to carry a single person. It was the first verified submarine capable of independent underwater movement, and the first to use screws for propulsion. In 1864, the Confederate navy's submarine became the first military submarine to sink an enemy vessel, the Union sloop-of-war, using a gunpowder-filled keg on a spar. The Hunley also sank, probably because the explosion's shock waves killed the crew before they could pump the bilge or move the boat away.

• 3. The Engine Problem

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  For most of the nineteenth century, the submarine's greatest limitation was not depth or hull strength but power. Human arms can only push a vessel so far and so fast. Widescale naval use was impossible until suitable engines arrived.

  The period from 1863 to 1904 resolved this. The first submarine not relying on human power was the French vessel launched in 1863, which ran on compressed air at 180 pounds per square inch. The Spanish designer Narcís Monturiol launched the first air-independent and combustion-powered submarine from Barcelona in 1864, using a chemical reaction involving zinc, manganese dioxide, and potassium chlorate to generate both heat for a steam engine and oxygen for the crew. A similar principle was not tried again until the German Navy tested a hydrogen peroxide system on the experimental V-80 submarine in 1940.

  The torpedo changed the strategic equation entirely. Robert Whitehead, a British engineer, designed the first practical self-propelled torpedo in 1866. That invention, which the source notes has remained essentially the same for more than a hundred and forty years, gave the submarine something far more dangerous than a spar charge: the ability to strike from a distance while remaining concealed.

  The Irish-American inventor John Philip Holland built a model submarine in 1876, demonstrated a prototype in 1878, and eventually designed the Holland Type VI, launched on the 17th of May 1897 at Navy Lieutenant Lewis Nixon's Crescent Shipyard in Elizabeth, New Jersey. The United States Navy purchased it on the 11th of April 1900 and commissioned it as the Navy's first submarine. The French followed with a steam and electric vessel commissioned in June 1900 that introduced the double-hull design, with a pressure hull inside an outer shell; these ships had a submerged range of over a hundred miles. Four years later, the French submarine Aigrette took another step by replacing the gasoline surface engine with a diesel, improving fuel efficiency and safety. Seventy-six submarines of that lineage were completed before 1914.

• 4. The World Wars

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  Germany entered the First World War with only twenty submarines ready for combat, though those included vessels of the diesel-engined U-19 class, which had a range of five thousand miles and a speed of eight knots sufficient to operate around the entire British coast. The Royal Navy, by comparison, had seventy-four submarines of mixed effectiveness. In August 1914, a flotilla of ten U-boats sailed from Heligoland to attack Royal Navy warships in the North Sea, the first submarine war patrol in history. By the war's end, U-boats had sunk more than five thousand Allied ships.

  The Second World War raised those stakes dramatically. Germany's effort to cut Britain's Atlantic supply routes, attacking more merchant ships than Britain could replace, very nearly succeeded. The key tactical innovation was Rudeltaktik, the mass-attack wolfpack method, made possible by communications encrypted through the Enigma cipher machine. Wolfpack coordination worked until Enigma was cracked. By the end of the war, U-boats had sunk nearly three thousand Allied ships: one hundred and seventy-five warships and two thousand eight hundred and twenty-five merchant vessels. Germany's U-boat fleet paid a severe price: seven hundred and ninety-three submarines lost and roughly twenty-eight thousand submariners killed out of forty-one thousand who served, a casualty rate of about seventy percent.

  The Imperial Japanese Navy operated the most varied submarine fleet of any navy in the war, including crewed torpedoes called Kaiten, midget submarines, and vessels capable of carrying multiple aircraft. Japan also fielded one of the most technically advanced torpedoes of the conflict, the oxygen-propelled Type 95. Despite this, Japan chose to direct its submarines against enemy warships rather than merchant shipping, and warships proved fast and well-defended targets. The American approach was opposite. US submarines were only about two percent of the Navy's total strength but destroyed over thirty percent of the Japanese Navy, including eight aircraft carriers, one battleship, and eleven cruisers. They also sank more than sixty percent of Japan's merchant fleet, crippling the country's ability to supply its military and factories. The total US submarine haul reached one thousand five hundred and sixty enemy vessels, representing 5.3 million tons of shipping, or fifty-five percent of all Japanese tonnage sunk by any means.

  One episode from the Royal Navy illustrates how far submarine tactics had advanced by that point. The British submarine Venturer sank an enemy submarine while both were fully submerged, the only documented instance of its kind. The Venturer crew manually computed a successful firing solution against a three-dimensionally maneuvering target. The techniques they used became the foundation of modern torpedo computer targeting systems.

• 5. Nuclear Power and the Cold War

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  In July 1953, a World War II fleet boat modified to carry missiles fired the first cruise missile ever launched from a submarine, the SSM-N-8 Regulus, which could carry a nuclear warhead. That vessel and its sister ship became the United States' first nuclear deterrent patrol submarines.

  Nuclear propulsion changed the nature of the submarine more fundamentally than any development since the torpedo. A steam turbine driven by a reactor eliminated the need for atmospheric oxygen, meaning that a submarine's time submerged was limited only by its food supplies: breathing air was recycled and fresh water was distilled from the sea. Nuclear submarines also have unlimited range at top speed. In 1959-1960, both the United States and the Soviet Union put their first ballistic missile submarines into service as part of their Cold War deterrent strategies.

  The Cold War produced its share of disasters. The Soviet Union lost at least four submarines during this period. One vessel was lost in 1968; part of it was later retrieved from the ocean floor by the CIA using the Howard Hughes-designed ship Glomar Explorer. Another Soviet boat, which held a depth record among military submarines of one thousand meters, was lost in 1989. The US lost two nuclear submarines: one due to equipment failure during a test dive at its operational limit, another to unknown causes.

  Beyond those losses, the period also produced the first submarine sinking since World War II. During the Indo-Pakistani War of 1971, a Pakistan Navy submarine sank the Indian frigate, the first such combat sinking since 1945. In 1982, during the Falklands War, the British nuclear submarine sank the Argentine cruiser, the first sinking by a nuclear-powered submarine in war. After that single event, the Argentine Navy concluded it had no effective defense against submarine attack and withdrew its entire surface fleet to port for the remainder of the conflict.

• 6. How a Submarine Dives

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  All surface ships, and submarines while surfaced, weigh less than the volume of water they would displace if fully submerged: that is what keeps them afloat. To dive, a submarine must reverse that condition, either by increasing its own weight or by decreasing the water it displaces.

  The mechanism submarines use is the ballast tank. Main ballast tanks, which operate at ambient pressure, flood with water to submerge and fill with air to surface. While submerged, they typically remain flooded; on many submarines, they occupy the space between the outer light hull and the inner pressure hull. For precise depth control, submarines use smaller tanks called depth control tanks, which can also be positioned along the hull's length to manage the vessel's fore-and-aft tilt.

  As a submarine descends, pressure increases significantly. For steel submarines, water pressure on the hull can reach four megapascals; for titanium submarines, up to ten megapascals. The hull compresses, which reduces its displacement, and buoyancy drops. A submerged submarine is inherently unstable, tending to either sink or float upward, which means depth control is a continuous active task rather than a passive one.

  Hull shape matters enormously. The modern cigar shape, sometimes called a teardrop hull, reduces hydrodynamic drag when submerged but is less suited to surface operation. Early submarines had to compromise because their propulsion systems forced them to spend most of their time on the surface. Late in World War II, faster submerged operation became possible and aerial surveillance made surface running dangerous, so hull designs shifted back toward the teardrop form to reduce drag and noise.

  The pressure hull itself must be nearly perfectly circular in cross-section: even a twenty-five millimeter deviation from roundness causes more than a thirty percent decrease in the hull's maximum hydrostatic load and consequently its safe diving depth. All joints must be welded without defects and are checked multiple times using different methods. Each modern US attack submarine costs approximately $2.6 billion, or more than $200,000 per ton of displacement, and the precision required to build the pressure hull is a significant part of why.

• 7. Civilian and Unconventional Uses

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  Tourism was an early civilian application. The first tourist submarine went into service in 1964 at Expo64. By 1997, forty-five tourist submarines were operating around the world. In a typical operation, passengers transfer from a surface vessel to a submarine offshore; the submarine then visits underwater points of interest, usually natural or artificial reef structures at depths between roughly a hundred and a hundred and twenty feet.

  The Submarine Voyage ride at Disneyland opened in 1959 but was not a true submarine: it ran on tracks and was open to the atmosphere. The distinction matters. True civilian submarines are used for marine science, salvage, exploration, and infrastructure inspection including pipelines and oil and gas platforms.

  At the other end of the civilian spectrum, drug smugglers in South America began deploying what are called narco-submarines to evade law enforcement. Most are self-propelled semi-submersibles that keep a portion of the craft above the waterline at all times. In September 2011, Colombian authorities seized a sixteen-meter-long submersible capable of holding a crew of five, estimated to have cost about two million dollars, belonging to FARC rebels. It had capacity to carry at least seven tonnes of drugs.

  Polar operations constitute a distinct chapter in submarine history. On the 3rd of August 1958, the USS Nautilus used an inertial navigation system to reach the North Pole, the first vessel to do so. On the 6th of May 1986, three submarines met and surfaced together at the Geographic North Pole, the first time three submarines had surfaced simultaneously at that location. Today, climate change and warming oceans are expected to complicate the detection of submarines at depth in much of the world, a strategic variable that will shape submarine operations in ways not yet fully understood.