Gotland - class submarine The " Gotland " class submarines of the Swedish Navy are modern diesel - electric submarines , which were designed and built by the Kockums shipyard in Sweden . They are the first submarines in the world to feature a Stirling engine air - independent propulsion ( AIP ) system , which extends their underwater endurance from a few days to weeks . This capability had previously only been available with nuclear - powered submarine s . Features . As of 2008 , the " Gotland " - class attack submarine is one of the most modern submarines of the Swedish Navy in service , mainly designed for submarine missions such as anti - ship / anti - submarine warfare , collecting of intelligence ( communications intelligence ( COMINT ) , electronic signals intelligence ( ELINT ) ) , forward surveillance , special operations and mine - laying tasks . On the water surface , the submarine is powered by two sets of MTU engines . While submerged , the Kockums - built Stirling engine Air Independent Propulsion ( AIP ) system is used to drive a generator for either propulsion or charging the batteries . A Stirling engine is particularly well suited for a submarine because the engine is near silent and can use the surrounding sea water as a heat sink to increase efficiency . Submerged endurance is dependent on the amount of liquid oxygen stored on - board and is described as " weeks " . The class is characterized by its low acoustic signatures , extreme shock resistance and a competent combat system . Kockums touts extreme maneuverability for this class due to the hull design and a well - placed X rudder . The X rudder provides four control surfaces , along with two mounted on the sail , which enables sharp turns and the ability to operate very close to the seabed . Ship automation and computerized steering allow a single operator to steer the submarine in depth and course , which also results in a smaller crew complement , leading to good accommodation standards and low operating costs . The class has many features that enhance stealth , helping it to remain undetected . All shipboard machinery are isolated and mounted on rubber dampeners to reduce vibrations and noises ; a hydrodynamic hull design to reduce noise , infrared signature , and active sonar response ; counteracting its magnetic signature with 27 independent electromagnets ; short circuiting extremely low frequency ( ELF ) electrical fields ; various hull coatings to reduce active sonar response ; and coating the mast with radar absorbing material . Combined with the near silent operation of the Stirling generator and slow turning propeller to prevent cavitation , the boats are very difficult to detect underwater , especially in their normal area of operations , the Baltic Sea . Deployments . After being refit and upgraded to sustain the higher temperatures of tropical water , HMS " Halland " took part in a multi - national exercise in the Mediterranean from September 16 , 2000 . Allegedly , there she remained undetected while still recording many of her friendly adversaries , attracting interest from the participating countries . In early November the same year , she participated in a NATO " blue - water " exercise in the Atlantic . There she reportedly won a victory in a mock " duel " with Spanish naval units , and then the same in similar duel against a French SSN , a nuclear - powered attack submarine . She also " defeated " an American SSN , the USS " Houston " . Secondment to United States Navy . In 2004 , the Swedish government received a request from the United States of America to lease HMS " Gotland " – Swedish - flagged , commanded and manned , for a duration of one year for use in anti - submarine warfare exercises . The Swedish government granted this request in October 2004 , with both navies signing a memorandum of understanding on March 21 , 2005 . The lease was extended for another 12 months in 2006 . In July 2007 , HMS " Gotland " departed San Diego for Sweden . HMS " Gotland " managed to snap several pictures of the USS " Ronald Reagan " during a wargaming exercise in the Pacific Ocean , effectively " sinking " the aircraft carrier . The exercise was conducted to evaluate the effectiveness of the US Fleet against diesel - electric submarine s , which some have noted as severely lacking . Overhaul . In March 2013 , Kockums received an order for an overhaul for two of the Gotland class submarines . The overhaul is expected to be completed by 2017 . With these upgrades , the submarines will be able to remain in active duty until after 2025 alongside the new A26 submarine s ( " NGU " ) .