Navy

Sweden Makes Some Tough Submarine (1 Sunk a U.S. Aircraft Carrier)

Back in the 1960s, Sweden had begun developing a modernized version of the Stirling engine, a closed-cycle heat conversion engine first developed in 1818. This was first used to power a car in the 1970s, then the Swedish ship-builder Kockums successfully retrofitted a Stirling engine to power a Swedish Navy A14 submarine Nacken in 1988. Because the Stirling burns diesel fuel using liquid oxygen stored in cryogenic tanks rather than an air-breathing engine, it can quietly cruise underwater at low speeds for weeks at a time without having to surface.

Kockums went on to build three Gotland-class submarines in the late 1990s, the first operational submarines designed with Air-Independent Propulsion systems. The Gotland became famous for sinking a U.S. aircraft carrier in a 2005 military exercise; its characteristics and operational history are further described in this earlier article. Stirling AIP technology has subsequently been incorporated into numerous Japanese and Chinese submarines, while Germany and France developed more expensive fuel-cell and steam-turbine based AIP submarines instead.