Södermanland class submarine
The Swedish
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 Södermanland class of diesel-electric
Diesel-electric transmission or diesel-electric powertrain is used by a number of vehicle and ship types for providing locomotion.A diesel-electric transmission system includes a diesel engine connected to an electrical generator, creating electricity that powers electric traction motors...

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s consist of the HMS Södermanland and HMS Östergötland. These two submarines were originally launched as Västergötland class submarine
Västergötland class submarine
The Västergötland class of diesel-electric submarines was introduced in 1987 by the Swedish Navy. The original four ships of her class, HMS Västergötland, HMS Hälsingland, HMS Södermanland and HMS Östergötland, were built between 1983 and 1988 by Kockums AB...

s in 1987 and 1990, and have been relaunched as a new class after extensive modernization 2003 and 2004 by Kockums AB. The pressure hull had been cut in two after the sail
Sail (submarine)
In naval parlance, the sail or fin of a submarine is the tower-like structure found on the dorsal surface of submarines...

 and a 12 m long new section with an air-independent propulsion
Air-independent propulsion
Air-independent propulsion 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 was inserted. It contains a Stirling engine
Stirling engine
A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....

 which is coupled to an electric generator and heated by burning diesel fuel with liquid oxygen
Liquid oxygen
Liquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...

 stored in cryogenic tanks. The AIP system can provide electric energy to extend the submarine's submerged time from days to weeks.

The class is planned to remain in service until 2018-19 when it will be replaced by the future A26 submarine.


Ship name Laid down Launched Commissioned Service Status
HMS Södermanland 12 April 1988 21 April 1989 1st Submarine Flotilla Refitted 2003, Active
HMS Östergötland 9 December 1988 1989 1st Submarine Flotilla Refitted 2004, Active

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