Navy

Did Sweden Make America's Nuclear Submarines Obsolete?

In the 1990s, submarines powered by Air Independent Propulsion (AIP) technology entered operational use. Though the concept dated back to the 19th century and had been tested in a few prototype vessels, it was left to Sweden to deploy the first operational AIP-powered submarine, the Gotland-class, which proved to be stealthy and relatively long enduring. The 60-meter long Gotlands are powered by a Stirling-cycle engine, a heat engine consuming a combination of liquid oxygen and diesel fuel.

Since then, AIP powered-submarines have proliferated across the world using three different types of engines, with nearly 60 operational today in fifteen countries. Around fifty more are on order or being constructed.