Air-independent propulsion

Air-Independent Propulsion (AIP), is a term that encompasses technologies which allow a submarine to operate without the need to surface or use a snorkel to access atmospheric oxygen. The term usually excludes the use of nuclear power, and describes augmenting or replacing the diesel-electric propulsion system of non-nuclear vessels.

Internal oxygen supply

History

During the Second World War the German firm Walter experimented with submarines that used concentrated hydrogen peroxide as their source of oxygen underwater. These used steam turbines which used steam heated by burning diesel fuel in the hydrogen/oxygen atmosphere created by the decomposition of hydrogen peroxide by a potassium permanganate catalyst.

Related Topics:
Second World War - German - Walter - Hydrogen peroxide - Steam turbine - Hydrogen - Potassium permanganate - Catalyst

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Several experimental boats were produced, and one, U-1407, which had been scuttled at the end of the war was savlaged and recomissioned into the Royal Navy as HMS Meteorite. The British built two improved models in the late 1950s, HMS Explorer, and HMS Excalibur.

Related Topics:
Royal Navy - HMS ''Meteorite'' - 1950s - HMS ''Explorer'' - HMS ''Excalibur''

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The Soviet Union also experimented with the technology. Hydrogen Peroxide was eventually abandoned since it was highly reactive when it came into contact with various metals, was volatile and submarines suffered from a high rate of consumption. Both countries abandoned it when the United States succeeded in developing a nuclear reactor small enough to be installed in a submarine.

Related Topics:
Soviet Union - United States - Nuclear reactor

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It was retained for propelling torpedoes by the British and the Soviet Union, although hastily abandoned by the former following the HMS Sidon tragedy. Both this and the loss of the Russian Submarine Kursk were due to accidents involving hydrogen peroxide propelled torpedoes.

Related Topics:
Torpedo - HMS ''Sidon'' - Russian Submarine ''Kursk''

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Closed cycle diesel engines

This technology uses a submarine diesel engine which can be operated conventionally on the surface, but which can also be provided with oxidant, usually stored as liquid oxygen, when submerged. Since the metal of an engine will burn in pure oxygen they usually dilute the oxygen with recycled exhaust gases. As there are no exhaust gases to use when the engine is started, initially argon is used.

Related Topics:
Diesel engine - Oxidant - Liquid oxygen - Argon

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The Soviet Union invested heavily in this technology, developing the small 650 ton Quebec-class submarine of which thirty examples were built between 1953 and 1956. These had three diesel engines—two conventional ones and one closed cycle engine which used liquid oxygen. They had a poor safety record, for instance the M-256 was lost following an explosion and fire. They were sometimes sarcastically nicknamed cigarette lighters. The last was scrapped in the early 1970s.

Related Topics:
''Quebec''-class - 1953 - 1956 - ''M-256'' - 1970s

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Currently the German U-1 boat is fitted with a 3000 horsepower (2.2 MW) experimental unit.

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Closed cycle steam turbines

The French (Module d'Energie Sous-Marine Autonome) system is the only one which is in current use, and is essentially a modified version of their nuclear propulsion system with heat being generated by ethanol and compressed oxygen.

Related Topics:
French - Ethanol

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Stirling cycle engines

The Swedish shipbuilder Kockums Naval Systems has constructed four submarines for the Swedish Navy which are fitted with auxilary Stirling-cycle engines which burn liquid oxygen and diesel fuel driving 75 kilowatt generators for either propulsion or charging batteries. The AIP endurance of the 1,500 ton boats is around 14 days at five knots (9 km/h).

Related Topics:
Swedish - Kockums Naval Systems - Swedish Navy

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