- 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 ofnuclear power , and describes augmenting or replacing the diesel-electric propulsion system of non-nuclear vessels. TheUnited States Navy uses thehull classification symbol "SSP" to designate boats powered by AIP, while retaining "SS" for classic diesel-electric attack submarines. [United States Navy Glossary of Naval Ship Terms (GNST). SSI is sometimes used, but SSP has been declared the preferred term by the USN. SSK (ASW Submarine) as a designator for classic diesel-electric submarines was retired by the USN in the 1950s, but continues to be used colloquially by the USN and formally by navies of the British Commonwealth and corporations such as Jane's Information Group.]AIP is usually implemented as an auxiliary source. Most such systems generate electricity which in turn drives an electric motor for propulsion or recharging the boat's batteries. The submarine's electrical system is also used to provide "hotel services"—ventilation, lighting, heating etc—although this consumes a small amount of power compared to that required for propulsion.
A benefit of this approach is that it can be retrofitted into existing submarine hulls by inserting an additional hull section. AIP does not normally provide the endurance or power to replace the atmospheric dependent propulsion, but allows it to remain submerged longer than a more conventionally propelled submarine. A typical conventional power plant will provide 3
megawatt s maximum, and an AIP source around 10% of that. A nuclear submarine's propulsion plant is usually much greater than 20 megawatts.Internal oxygen supply
History
In 1867
Narcís Monturiol i Estarriol successfully developed an early form of anaerobic air independent propulsion. In 1908 the Imperial Russian Navy launched theRussian submarine Pochtovy which used a gasoline engine fed with compressed air and exhausted under water.During
World War II the German firm Walter experimented with submarines that used concentratedhydrogen peroxide as their source of oxygen underwater. These usedsteam turbine s, employing steam heated by burning diesel fuel in the steam/oxygen atmosphere created by the decomposition of hydrogen peroxide by apotassium permanganate catalyst .Several experimental boats were produced, and one, U-1407, which had been scuttled at the end of the war, was salvaged and recommissioned into the
Royal Navy as HMS "Meteorite". The British built two improved models in the late 1950s, HMS "Explorer", and HMS "Excalibur".The
Soviet Union also experimented with the technology. Hydrogen peroxide was eventually abandoned since it is highly reactive when in contact with various metals, is volatile, and submarines had a high rate of consumption. Both the British and the Soviets, the only countries known to be experimenting with it, abandoned it when theUnited States developed anuclear reactor small enough for submarine propulsion.It was retained for propelling
torpedo es 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.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 withoxidant , usually stored asliquid oxygen , when submerged. Since the metal of an engine will burn in pure oxygen, the oxygen is usually diluted with recycled exhaust gas. As there is no exhaust gas upon starting,argon is used.The Soviet Union invested heavily in this technology, developing the small 650 ton "Quebec"-class submarine of which thirty were built between 1953 and 1956. These had three diesel engines—two were conventional and one was closed cycle using liquid oxygen. They had a poor safety record; the "M-256" was lost following an explosion and fire. They were sometimes nicknamed "cigarette lighters". The last was scrapped in the early 1970s.
The
German Navy 's formerType 205 submarine U1 was fitted with an experimental 3000 horsepower (2.2 MW) unit.Closed cycle steam turbines
The French
MESMA (Module d'Energie Sous-Marine Autonome) system is being offered by the French shipyard DCN. Currently a MESMA Section is retrofitted to an Agosta 90B of thePakistan Navy . It is essentially a modified version of their nuclear propulsion system with heat being generated byethanol and oxygen.tirling cycle engines
The Swedish shipbuilder
Kockums has constructed three Gotland class submarines for theSwedish Navy which are fitted with an auxiliary Stirling engine which uses liquid oxygen and diesel fuel to drive 75 kilowatt generators for either propulsion or charging batteries. The AIP endurance of the 1,500 tonne boats is around 14 days at five knots (9 km/h).Kockums has also delivered Stirling engines to Japan. The new Japanese submarines will all be equipped with Stirling engines. The first submarine, "Sōryū", in the class was launched on5 December 2007 and will be delivered to the navy in March 2009.Fuel cells
Siemens has developed a 30-50 kilowatt fuel cell unit. Nine of these units are incorporated into
Howaldtswerke Deutsche Werft AG's 1,830t submarine "U31", lead ship for the Type 212A class of theGerman Navy . The other boats of this class and HDW's AIP equipped export submarines (Type 209 mod and Type 214) use two 120 kW modules, also from Siemens. [ [http://www.naval-technology.com/projects/type_212/ Naval Technology - U212/U214 - Attack Submarine ] ]After the success of
Howaldtswerke Deutsche Werft AG's in its export activities, several builders have developed their own fuel-cell auxiliary units for submarines but until todayClarifyme|date=March 2008 no other shipyard has a contract for a submarine so equipped.Nuclear power
Nuclear reactors have been used for 50 years to power submarines, the first being USS "Nautilus". The
United States ,France , theUnited Kingdom ,Russia and thePeoples Republic of China are the only countries known to operate nuclear powered submarines. These five countries also have permanent seats on theUnited Nations Security Council and are the only countries allowed to possess nuclear weapons according to theNuclear Non-Proliferation Treaty . India is currently constructing a nuclear powered submarine codenamed ATV. India in the past has leased a Charlie class nuclear powered submarine from Russia and plans to acquire two usedAkula class submarine s which would be used for research purposes.Brazil is also known to research nuclear propulsion for submarine use. However, Air Independent Propulsion is a term normally used in the context of improving the performance of conventionally propelled submarines.There have nevertheless been suggestions for a reactor as an auxiliary power supply, which does fall into the normal definition of AIP. For example, there has been a proposal to use a small 200 kilowatt reactor for auxiliary power (styled a "
nuclear battery ") to improve the under-ice capability of Canadian submarines.Production Non-Nuclear AIP Submarines
As of 2008, some nations have non-nuclear AIP submarines:
* the ChineseType 041 submarine "Yuan" (Stirling AIP) of thePeople's Liberation Army Navy
* the French-Spanish "Scorpène"-class submarine (1,700 tonnes) (MESMA)
* the German Type 209-1400mod (1,810 tonnes) (Fuel cell)
* the Italo-GermanType 212 submarine (1,830 tonnes) (Fuel cell) of theGerman Navy andItalian Navy
* the German Type 214 (1,980 tonnes) (Fuel cell)
* the Russian Project 1650 "Амур"
* the Japanese Asashio (2,750 tonnes) (Stirling AIP) of theJapan Maritime Self-Defense Force
* the JapaneseSōryū class submarine (4,200 tonnes) (Stirling AIP) of theJapan Maritime Self-Defense Force
* the SwedishGotland class submarine (1,450 tonnes) (Stirling AIP) of theSwedish navy
* the SwedishSödermanland class submarine (1,500 tonnes) (Stirling AIP) of theSwedish navy
* The Turkish/German Type 214TN to be co-produced in Turkey, with 80% Turkish systems.Sweden is going to sell its remaining twoVästergötland class submarine s to theRepublic of Singapore Navy after they have been refitted with Stirling AIP systems like theSödermanland class submarine s.Also several shipbuilders offer AIP upgrades for existing submarines:
* GermanNordseewerke (Closed-cycle diesel)
* SwedenKockums (Stirling), owned by German companyThyssenKrupp
* PakistanAgosta 90 B submarine Hamza Made with cooperation with FranceReferences
External links
* [http://www.navy.mil/navydata/cno/n87/usw/issue_13/propulsion.htm Underseas Warfare article on AIP]
* [http://www.navyleague.org/seapower/aip_alternative.htm Seapower article]
* [http://www.iync.org/archive/iync2004/presentation/track_b/b1/christopher_cole.pdf Auxiliary nuclear reactor for Canadian submarines .PDF]
* [http://www.industry.siemens.com/broschueren/pdf/Marine/Sinavy/en/SINAVY_FuelCells_e_Fr_SMM2809.pdf Siemens fuel cells for submarines .PDF]
* [http://www2.sea.siemens.com/NR/rdonlyres/D3201AC8-C746-4EC8-975A-64E607662195/0/SiemensPresentsFuelCellattheAdvanceNavalPropulsionSymposium.pdf Research paper describing Siemens submarine fuel cells .PDF]
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