In 2005, US Navy aircraft carrier the USS Ronald Reagan met its match in the form of a diesel-powered Swedish submarine. During war games, the Gotland-class submarine was able to sneak through the passive sonar defenses of the USS Ronald Reagan and its battle group to score a few, virtually, torpedo hits, sinking the cruiser and getting away without a scratch.
The question is how. This Real Engineering video explains, it’s all thanks to a very old-school engine. The Gotland-class sub instead of standard diesel engine, uses highly optimized Sterling engines. This type of engines are very quiet and they are used to charge batteries directly running the engines. The result of this technology is a submarine that is quieter than any other diesel engine and even quieter than nuclear powered subs.
After this virtual defeat, the US Navy leased a Gotland class submarine from Sweden in order to figure out how to counter this stealth feature.
