Type XVII submarine
The Type XVII U-boats were small coastal submarines that used a high-test peroxide propulsion system, which offered a combination of air-independent propulsion and high submerged speeds. == Background == In the early 1930s Hellmuth Walter had designed a small, high-speed submarine with a streamlined form propelled by high-test peroxide (HTP) and in 1939 he was awarded a contract to build an experimental vessel, the 80 ton V-80, which achieved an underwater speed of 28.1 knots (52.0 km/h; 32.3 mph) during trials in 1940.