Submarine SnorkelsDuring World War Two German submarine losses increased sharply as radar-equipped Allied aircraft attacked U-boats running on the surface recharging their batteries. To charge the batteries that powered the electric motors for submerged operations, all submarines had to surface to run their air-breathing diesel engines. To counter the Allied radar threat the Germans perfected a Dutch device known as the snorkel. Using a snorkel a submarine could run its diesel engines and recharge its batteries while operating just below the surface. Air for the diesel engines was drawn into the submarine through the snorkel that was extended to the surface. To some extent the snorkel reduced vulnerability to detection and attack, but it protruded above the surface and could be detected by radar. The Germans introduced the snorkel too late in the war to make a difference.
JapanAlthough the U.S. Navy still had a relatively small number of subs when World War Two broke out, this fact did little to dampen the spirits of American submariners. On January 7th, 1942, one month after the attack on Pearl Harbor, the USS Pollack (SS-179) sank a Japanese freighter off Tokyo Bay. It would be the first of many sinkings by U.S. submarines. When the figures were finally tabulated, it was found that American submarines sank five and one-half million tons of Japanese shipping, over half of the entire Japanese merchant fleet. U.S. subs accounted for about 60 per cent (over 1300 ships) of all Japanese merchant and warship tonnage sunk, yet the submarine strength at that time comprised less than two per cent of the entire U. S. Fleet.
The U.S. sub campaign deprived Japanese industry of raw materials and effectively shut down Japan's economy. The price of this success was high, 52 American submarines and over 3500 sailors remain on eternal patrol.
Greater Underwater Propulsion ProgramTechnological advancements like sonar, radar, and the snorkel came about as a result of the pressures of WW II, and the U.S. Navy applied these advances to improving its Submarine Force. In the late 1940s the Navy began the Greater Underwater Propulsion Program (Guppy), a modernization program for World War Two fleet-type submarines.
Under Guppy the fleet boats were streamlined by reducing the submarine's superstructure and removing deck guns. Snorkel masts were installed to allow Guppys to remain submerged while they ran their diesel engines and charged batteries. Finally, improved storage battery technology permitted longer submerged operations between battery charges. However, the Guppy program was evolutionary, a development of existing technologies.