On Friday October 19 His Swedish Majesty Ship (HSwMS) Gotland started its sea trials at the Saab shipyard in Karlskrona, after a comprehensive Mid-Life Upgrade (MLU) to ensure its operational service to Sweden beyond 2025. HSwMS Gotland is the first of two submarines being upgraded with the mid-life modifications, which consist of upgrades of onboard systems and technology, sustaining the submarine’s operational capability to meet future naval challenges. The sea trials mark an important phase in the MLU project. This is the first time the crew will be able to operate the new systems in the true environment. After extensive training in the land based training facility, they will now be able to see the true potential of their submarine
The upgrade process entails many important systems, such as the Stirling Air Independent Propulsion (AIP) for longer duration underwater and the combat system. Even the traditional optical periscope is replaced with a new optronic mast for enhanced surveillance. More than 20 systems on-board the upgraded Gotland-class will be implemented in the new A26 submarine for Sweden. The Gotland MLU therefore contributes to the test and qualification of some of the innovative solutions to be implemented in the future Swedish A26 submarines. After tests and verifications, the submarine will be delivered back to the Swedish Navy.
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. 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 antiship/antisubmarine warfare, collecting of intelligence, forward surveillance, special operations, and mine-laying tasks. 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. The class has many features that enhance stealth, helping it to remain undetected. All shipboard machinery is isolated and mounted on rubber dampeners to reduce vibrations and noises; a hydrodynamic hull design reduces noise, infrared signature, and active sonar response. Combined with the near-silent operation of the Stirling generator and slow-turning propeller to prevent cavitation, the boats are very difficult to detect under water, especially in their normal area of operations, the Baltic Sea.
The Gotland-class submarines 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. In 2004, the Swedish government received a request from the United States to lease HSwMS Gotland – Swedish-flagged, commanded and manned, for a duration of one year for use in antisubmarine warfare exercises. The Swedish government granted this request in October 2004, with both navies signing a memorandum of understanding on 21 March 2005. The lease was extended for another 12 months in 2006. In July 2007, HSwMS Gotland departed San Diego for Sweden. HSwMS Gotland managed to snap several pictures of 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 submarines, which some have noted as severely lacking.