Gotland-class submarine

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Gotland-class submarine

Overview
The Gotland-class is a Swedish Navy group of diesel-electric attack submarines built by Kockums in the 1990s. They are famous for being the first submarines in the world to use Stirling engine air‑independent propulsion (AIP), which lets them stay underwater for weeks instead of days. They are small, quiet, and highly maneuverable, designed for anti-ship and anti-submarine warfare, intelligence gathering, forward surveillance, special operations, and mine-laying.

Design and capabilities
- Propulsion: On the surface, two MTU diesel engines power the boat. Submerged, a Stirling engine runs a 75 kW generator to drive propulsion or charge batteries, allowing long underwater endurance.
- Stealth: Low noise hull design, vibration isolation, slow-turning propeller, and various coatings reduce detectability. AIP and a quiet Stirling engine help the submarine stay hidden underwater.
- Performance: Surfaced speed around 11 knots; submerged speed up to about 20 knots on batteries, with lower speed when using AIP.
- Size and crew: Displacement around 1,500 tons surfaced, roughly 1,600 tons submerged; about 18–22 officers and 6–10 ratings.
- Sensors and armament: CSU 90-2 sonar suite; four 533 mm torpedo tubes, two 400 mm torpedo tubes, and space for 48 naval mines. The mast carries advanced sensors while remaining covert.

Units
- HSwMS Gotland (Gtd)
- HSwMS Uppland (Upd)
- HSwMS Halland (Hnd)
Built in the early 1990s (laid down 1992–1994; launched 1995–1996) and all active in Sweden’s 1st Submarine Flotilla.

Operational history (highlights)
- Early missions and trials established Gotland-class capabilities as stealthy, ocean-going diesel-electric submarines.
- 2000: HSwMS Halland participated in multinational exercises in the Mediterranean and the Atlantic; the submarine reportedly operated undetected while recording contacts.
- 2004–2007: Gotland was leased to the United States Navy for antisubmarine-warfare training and exercises, with the arrangement extended for another year in 2006. The deal highlighted the Gotland’s stealth advantages.
- 2005: Gotland demonstrated its reach by taking photos of USS Ronald Reagan during a wargaming exercise in the Pacific.
- 2010s–present: Sweden launched a major mid-life upgrade program to extend Gotland-class service life. Two boats (Gotland and Uppland) were upgraded starting around 2015, with Gotland returning to active duty in 2018 after upgrading more than 20 systems. Uppland relaunched in 2019 and delivered to the Navy in 2020.
- 2022–2025: A mid-life upgrade (MLU) contract was signed for the third Gotland-class submarine (and related boats), with Halland receiving a dedicated upgrade. Halland was relaunched in February 2025 after its upgrade. The upgrades aim to keep the class capable into the mid-2020s and beyond, and the work has fed into improvements for Sweden’s newer A26 submarines as well.
- Overall, the Gotland-class remains a symbol of Sweden’s emphasis on stealth, endurance, and modernizing its submarine fleet to meet 21st-century security needs.

Current status
As of the mid-2020s, all three Gotland-class boats (Gotland, Uppland, Halland) have undergone, or are undergoing, mid-life upgrades to extend their operational lives and capabilities. Sweden continues to invest in new stealth submarines (Type 26 program) while keeping the Gotland-class active through mid-life modernization.

Note
The class is often cited for its pioneering use of Stirling engine AIP and for its demonstrated stealth and endurance, which have influenced submarine design worldwide.