Submarine

A **submarine** is a watercraft capable of independent operation underwater.

Various human nations, as well as other civilisations throughout the galaxy, have been known to operate different types of submarines in various capacities.

## Human submarines

Submersibles supported by surface vessels were used by human scientific organisations for underwater exploration beginning in the mid-19th century. Great Britain and France first deployed early and primitive coastal submarines for military use during the Crimean War in 1853.

Prussia developed the capability to fire long-range offensive rockets from submerged submarines before 1870. These weapons were used to great effect in the Franco-Prussian War, where Prussia used submarine-launched rockets to destroy the French rocket base at Toulouse.

By the time of the Great War in 1914, all of the major combatant nations had deployed several different types of ocean-going and coastal attack submarines. Most also had large ocean-going submarines that could fire offensive rockets while fully submerged underwater. During the Great War, the so-called "rocket submarines" were frequently used to attack high-value targets, sometimes using rockets tipped with chemical warheads.

During the Great War the German Empire, whose waters were blockaded by the large and powerful Royal Navy of Great Britain, used attack submarines to sink thousands of British, French, Russian, Italian and Canadian-flagged merchant ships carrying war material and supplies across the Atlantic from the Americas to Allied nations. German submarines did not intentionally attack ships bearing the flag of the United States or other neutral nations, with the Germans not wanting to risk bringing the U.S. into the war on the Allied side. In response, the Allies organised trans-Atlantic merchant ships in convoys escorted by aircraft carriers, surface warships equipped with anti-submarine weapons, and airships.

There was initially little investment in submarine technology after the end of the Great War. It was presumed that the gravity drive and advanced spaceships would make ocean-based naval warfare on Earth obsolete, however this changed in the late 1950s when the United States began experimenting with submarines propelled through the water using gravity drives instead of traditional propellers and which used atomic reactors for their electrical and oxygen generation systems. This new generation of gravity drive-powered submarines was incredibly fast, with top speeds exceeding 60 knots, and they could stay underwater practically indefinitely due to their nuclear energy generation systems. While gravity drive-powered aircraft and airships were still much faster, it was thought that submarines could still be very useful for launching surprise attacks and intelligence gathering due to how difficult they were to detect. In 1963, the United States Navy introduced the first of what it termed "deterrent submarines" - huge boats which were propelled by gravity drives, used small nuclear reactors for their electrical and oxygen generation systems, and were armed with long-range autonomous gravity drive-powered cruise missiles equipped with nuclear warheads. Unlike land-based nuclear strike aircraft and missile launchers, which could potentially be located and destroyed by an adversary before they were able to counterattack, a patrolling deterrent submarine would be very difficult to destroy in an enemy first strike attack with nuclear weapons. The United States also constructed similar attack submarines powered by gravity drives and nuclear reactors, but they were primarily equipped with torpedoes for sinking enemy submarines and surface ships.

The United States also experimented with a submarine that used a turbine powered by minaturised gravity drives to generate electrical power instead of a nuclear reactor. While this anti-gravity generator was much more efficient than a nuclear reactor, crucially the spinning of the large turbine blades made the submarine much noisier and easier to detect while the generator was running. This technology was therefore abandoned, and the United States continued to use nuclear reactors to power the electrical systems of its submarines.

The Soviet Union, which had focused on developing fusion energy and fusion weapons instead of nuclear technology, developed its own deterrent submarine with its propulsion, electrical and oxygen generation systems powered by a fusion reactor. The Soviet Union's fusion-powered submarines were operationally deployed from 1967. As the Soviet Union did not yet have access to the gravity drive like the United States and had to rely on the fusion reactor to drive a traditional propeller its submarines were slower than their American equivalents, with a top speed of around 45 knots. However, the smaller size of the Soviet fusion reactors meant that their submarines could be more compact. The Soviet deterrent submarines were also considerably better-armed, trading the nuclear gravity drive-powered cruise missiles of the American submarines for submarine-launched ballistic missiles propelled by fusion rockets and equipped with fusion warheads.

In 1969, Japan became the third nation after the United States and the Soviet Union to begin deploying deterrent submarines. The Japanese submarines were similar to those used by the United States, with gravity drives for propulsion, nuclear reactors to power electrical and life support systems, and an armament of gravity drive-propelled cruise missiles equipped with nuclear warheads.