Swedish Navy Gotland-Class Submarine HSwMS Uppland Relaunched Following Mid-Life Upgrade

Swedish Navy Gotland-class diesel-electric submarine HSwMS Uppland was relaunched on June 19 following the completion of comprehensive mid-life upgrades (MLU).

HSwMS Uppland is the second 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 first submarine, HSwMS Gotland was relaunched during a ceremony at the Saab Kockums’ shipyard in Karlskrona, Sweden on June 20 last year.

“The relaunch of a second Air Independent Propulsion (AIP) submarine within 12 months illustrate the skills and capacity of a world-class shipyard”, said Saab, the contractor conducting the MLU, in a statement.

Gotland-class submarines are the first submarines in the world to feature a Stirling engine AIP system, which extends their underwater endurance from a few days to weeks. This capability had previously only been available with nuclear-powered submarines. The Stirling engines use liquid oxygen and diesel as the propellant.

“Few shipyards around the world have the experience of completely modifying a submarine, creating almost a new ship. We are the only one having completed it twice within 12 months, first with HMS Gotland and now HMS Uppland. If you take into account that smartphones did not even exist when these vessels were launched at the end of the 1990’s, you begin to grasp the huge leap submarine technology has taken during this period and how significant this mid-life upgrade is,” says Gunnar Wieslander, Senior Vice President, head of Saab business area Kockums.

HMS Uppland was designed and built by Kockums in Malmö in the early 1990’s and commissioned in 1997. The mid-life upgrade consists of modifications, replacement and upgrades of on-board systems and technologies, sustaining the submarine´s operability.

In 2015, Sweden’s Defense Material Administration (FMV) signed a contract with Saab Kockums which included the mid-life upgrade of two Gotland class submarines for SEK 2.1 million. The FMV has also asked for option prices for upgrades to the third vessel of the class.

The contract included the modifications the of two submarines, verification including Set to Work (STW), Harbour Acceptance Test (HAT), Sea Acceptance Test (SAT), training, documentation, spares and upgrade of land-based Training Facility.

For the upgrade, the submarine was cut open in the mid-tank section for adding a new section including sea water cooling, fresh water cooling and water chiller units.


The upgrade process entails many important systems, such as the Stirling Air Independent Propulsion (Stirling AIP MkIII). Sensors, management and communications system are replaced with updated versions. Even the traditional optical periscope is replaced with a new optronic mast.


The updated version of Uppland and her sister ship Gotland are paving the way for the development of the most modern AIP submarine under production today: the Blekinge-class (A26), for the Royal Swedish Navy.

More than 20 systems on-board the new Gotland-class will be implemented in the A26 which contributes to their de-risking for the A26. The MLU therefore contributes to the test and qualification of some of the innovative solutions to be implemented in the future A26 submarine class. This also gives great training opportunities for the crew when they in the future deploy onboard the A26.


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