World War II

 

The Argonaut was the largest non-nuclear submarine ever built by the US Navy, and led to the highly successful American Gato and Balao class submarines used in World War II.

 

The ultimate diesel-electric submarine developed during wartime was the German Type XXI, a 250-foot-long, 1,600-ton boat capable of submerging at 17.5 knots for over an hour, or at 6 knots for two days, or "crawling" at a slow speed for four days. These submarines were equipped with snorkels (see below) so they did not have to fully surface to recharge their batteries after being deployed underwater. The Type XXI had an operating depth of 269 meters, more than twice the normal depth at the time, and was armed with four 33 mm guns and six bow torpedo tubes (capable of carrying 23 torpedoes). These features made all previous submarines obsolete. If the war had continued beyond the spring of 1945, existing Allied anti-submarine forces would have had serious problems with these boats.

 

A final wartime German design of particular interest was the Walther turbine propulsion system. Because combustion requires oxygen, previously it was not possible to use steam turbines or diesel engines while a submarine was submerged and lacking air. German scientist Helmut Walther developed a turbine propulsion system that used oxygen produced by hydrogen peroxide to run a turbine underwater.