'Cheap and Quiet' Submarine from Sweden 'Sunk' a U.S. Navy Aircraft Carrier in a Wargame

What You Need to Know: The Swedish Navy's Gotland-class submarine, built between 1992 and 1996, revolutionized diesel-electric submarines with its Stirling engine air-independent propulsion (AIP) system, allowing it to remain submerged for up to 14 days.

-This advanced capability made the Gotland one of the first diesel-electric subs to challenge nuclear-powered vessels. In 2005, the Gotland proved its prowess during a U.S.-Swedish naval war game, where it successfully evaded an entire U.S. carrier strike group, including the USS Ronald Reagan.

-Its quiet Stirling engines helped it evade detection and land simulated torpedo strikes on the carrier, demonstrating the Gotland's stealth and operational effectiveness.

How Sweden’s Stirling-Powered Gotland-Class Sub Outmaneuvered the USS Ronald Reagan

The Gotland-class is a diesel-electric submarine built between 1992 and 1996 for the Swedish Navy. Three Gotlands were built, and all remain in active service. 

The Gotland is distinct for being the first submarine in the world to feature a Stirling engine air-independent propulsion system, or AIP. This system allows the Gotland to stay submerged for weeks, rather than just days. 

Enhanced Endurance Submarine

Before the Gotland-class incorporated the AIP system, only nuclear-powered submarines could stay submerged for weeks. Diesel-electric submarines had to surface after a few days. The AIP changed that, ushering in a new era for diesel-electric submarine endurance.

AIP is a marine propulsion technology that allows a non-nuclear submarine to operate without access to atmospheric oxygen. In the past, oxygen was accessed by snorkeling or surfacing.

The Gotland’s Stirling AIP systems burn diesel fuel with liquid oxygen to drive 75 kilowatt electrical generators for propulsion. The Gotland’s AIP system permits the vessel to stay submerged for 14 days while traveling at 5 knots – good for a range of 1,700 nautical miles.

Versatile and Advanced

The Gotland is considered one of the most modern submarines in the Swedish Navy, capable of performing a variety of missions including anti-ship/anti-submarine warfare; communications intelligence; electronic signals intelligence; forward surveillance; special operations; and mine-laying. In short, the Gotland is a versatile vessel.

Relative to modern American submarines, the Gotland is modestly sized at 198 feet long, with a 20-foot beam and 18-foot draft.

The Gotland displaces 1,574 tons when submerged. By comparison, the U.S. Navy’s Ohio-class submarine measures 560 feet long and displaces nearly 19,000 tons when submerged. 

It may be small, but the Gotland has proven itself capable of felling larger foes.

Aircraft Carrier Killer

During a 2005 war game involving the U.S. and Swedish navies, a $100 million Gotland-class vessel proved itself capable of foiling an entire American carrier strike group (CSG) that included the $6 billion USS Ronald Reagan supercarrier alongside destroyers, helicopters, and submarines.

During the war game, the Gotland was tasked with attacking the Ronald Reagan against the entire might of the CSG defending it.

The CSG was the heavy favorite, but the Gotland was able to elude the supercarrier’s passive sonar defenses and land multiple virtual torpedo strikes. The hypothetical damage inflicted would have been enough to sink the carrier.

Making the victory even more demoralizing to the Americans, the Gotland was able to slip away from the CSG undetected, all without sustaining a scratch.

The Gotland-class submarine won the encounter, uncontested.

Popular Mechanics explained how the Gotland pulled off the stunning victory:

“It’s all thanks to a very old-school engine. Instead of using its diesel to power an internal combustion engine (which is quite loud, what with the explosions and all), the Gotland-class sub instead uses highly optimized Stirling engines, not unlike what you might find as a desk toy, but considerably more high tech.” 

The Stirling engines, it turns out, are exceedingly quiet – even quieter than their nuclear contemporaries.

About the Author: Harrison Kass 

Harrison Kass is a defense and national security writer with over 1,000 total pieces on issues involving global affairs. An attorney, pilot, guitarist, and minor pro hockey player, Harrison joined the US Air Force as a Pilot Trainee but was medically discharged. Harrison holds a BA from Lake Forest College, a JD from the University of Oregon, and an MA from New York University. Harrison listens to Dokken.

Image Credit: Creative Commons.