Submarine

:For the sandwich, see Submarine sandwich

Submarine propulsion

Until the advent of nuclear marine propulsion, most 20th century submarines used batteries for running underwater and gasoline (petrol) or diesel engines on the surface and to recharge the batteries. Early boats used gasoline but this quickly gave way to diesel because of the greatly reduced flammability of diesel. The diesel-electric submarine became the standard means of propulsion. Initially the diesel or gasoline engine and the electric motor were on the same shaft which also drove a propeller with clutches between each of them. This allowed the engine to drive the electric motor as a generator to recharge the batteries and also propel the submarine if required. The clutch between the motor and the engine would be disengaged when the boat dived so that the motor could be used to turn the propeller. The motor could have more than one armature on the shaft — these would be electrically coupled in series for slow speed and parallel for high speed (known as "group down" and "group up" respectively).

Related Topics:
Nuclear marine propulsion - 20th century - Gasoline - Diesel

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In the 1930s the principle was modified for some submarines designs, particularly those of the U.S. Navy and the British U-class. The engine was no longer attached to the motor/propeller drive shaft but drove a separate generator which would drive the motors on the surface and/or recharge the batteries. This allowed much more flexibility, for example the submarine could travel slowly on the surface whilst the engines were running at full power to recharge the batteries as quickly as possible. Despite this flexibility, battery/diesel submarines are required to surface frequently to recharge the batteries, as the diesel engines require oxygen from the atmosphere.

Related Topics:
1930s - U.S. Navy - U-class

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There were other power sources tried—oil-fired steam turbines powered the British "K" class submarines built during the First World War and in following years but these were not very successful.

Related Topics:
"K" class submarines - First World War

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This was selected to give them the necessary surface speed to keep up with the British battle fleet.

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Steam power was resurrected in the 1950s with the advent of the nuclear-powered steam turbine driving a generator which is now used in all large submarines. By removing the requirement for atmospheric oxygen these submarines can stay submerged indefinitely so long as food supplies remain (air is recycled and water distilled from the ocean). These vessels nevertheless always have a small battery and diesel engine/generator installation for emergency use should the reactor have to be shut down.

Related Topics:
1950s - Distilled

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Anaerobic propulsion was employed by the first mechanically driven submarine Ictineo II in 1864. Ictineo's engine used a chemical mix containing a peroxide compound, that generated heat for steam propulsion while at the same time solved the problem of oxygen renovation in an hermetic container for breathing purposes. The system wasn't employed again until 1940 when the German Navy tested a system employing the same principles, the Walter turbine, on the experimental V.80 submarine and later on the naval U.791 submarines.

Related Topics:
Anaerobic - Ictineo II - 1864 - Peroxide - Oxygen - Hermetic - 1940 - Walter - Turbine - V.80 - U.791

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At the end of the Second World War the British and Russians experimented with Hydrogen Peroxide/Kerosine engines which could be used both above and below the surface. The results were not encouraging enough for this technique to be adopted at the time, although the Russians deployed a class of submarines with this engine type code named Quebec by NATO, they were considered a failure. Today several navies, notably Sweden now use air-independent propulsion boats which substitute liquid oxygen for hydrogen peroxide.

Related Topics:
Second World War - British - Hydrogen Peroxide - Quebec - Sweden - Air-independent propulsion - Oxygen

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Most small modern commercial submarines which are not expected to operate independently just use batteries which can be recharged by a mother-ship following every dive.

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Towards the end of the 20th century, some submarines began to be fitted with pump-jet propulsors instead of propellors. Although these are heavier, more expensive, and often less efficient than a propellor, they are significantly quieter, giving submarine commanders an important tactical advantage.

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A further possible propulsion system for submarines is the Magnetohydrodynamic drive, or "caterpillar drive", which has no moving parts. It was popularized in the movie version of The Hunt for Red October, written by Tom Clancy, which portrayed it as a virtually silent system. (In the book, a form of propulsor was used rather than an MHD). Although some experimental surface ships have been built with this propulsion system, speeds have not been as high as those hoped. In addition, the great noise created by the formation of bubbles, and the higher power settings a submarine's reactor would need compared to a propulsor, mean that it is unlikely to be considered for any military purpose.

Related Topics:
Magnetohydrodynamic drive - The Hunt for Red October - Tom Clancy

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Another fictional, but detailed, account of the technology behind a modern military submarine, including sketches of an ultra-quiet propulsion system, can be found in the thriller Ninth Day of Creation, published in 2000. In this case the submarine depicted is the USS Columbia (SSN-771), an actual Los Angeles class submarine commissioned in 1995.

Related Topics:
Ninth Day of Creation - 2000 - USS Columbia (SSN-771) - Los Angeles class submarine - 1995

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