The

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used b ...

''Södermanland'' class of diesel-electric submarines consists of and . These two submarines were originally launched as s in 1987 and 1990, and have been relaunched as a new class after extensive modernization in 2003 and 2004 by

Kockums AB Saab Kockums AB is a shipyard headquartered in Malmö, Sweden, owned by the Swedish defence company Saab Group. Saab Kockums AB is further operational in Muskö, Docksta, and Karlskrona. While having a history of civil vessel construction, Koc ...

. The

pressure hull A submarine hull has two major components, the ''light hull'' and the ''pressure hull''. The light hull (''casing'' in British usage) of a submarine is the outer non-watertight hull which provides a hydrodynamically efficient shape. The pressur ...

had been cut in two after the

sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails ma ...

and a long new section with an

air-independent propulsion Air-independent propulsion (AIP), or air-independent power, is any marine propulsion technology that allows a non-nuclear submarine to operate without access to atmospheric oxygen (by surfacing or using a snorkel). AIP can augment or replace the ...

system was inserted. It contains two

Stirling engine A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas (the '' working fluid'') between different temperatures, resulting in a net conversion of heat energy to mechanical work. More spe ...

s which are coupled to

electric generators In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power (chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, gas ...

and heated by burning

diesel fuel Diesel fuel , also called diesel oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and ...

with

liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an a ...

stored in

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

tanks. The AIP system can provide electric energy to extend the submarine's submerged time from days to weeks. , ''Södermanland'' is planned to remain in service until at least 2024-25 when it was to be replaced by the future s. However, the ''Östergötland'' was decommissioned in 2021, and is in material reserve. Two submarines of similar design, known as the are in service with the

Republic of Singapore Navy The Republic of Singapore Navy (RSN) is the naval service branch of the Singapore Armed Forces (SAF) responsible for defending the country against any sea-borne threats, and the protection of its sea lines of communications, that would com ...

Units

References

External links

Kockums page about the Södermanland classKockums AIP Stirling system
Submarines of the Swedish Navy Submarine classes of the Swedish Navy Naval ships of Sweden {{submarine-stub