The Porpoise class were submarines built for the United States Navy in the late 1930s, and incorporated a number of modern features that would make them the basis for subsequent , , , , , and classes. In some references, the Porpoises are called the "P" class. Design The four submarines of the P-1 and P-3 types were authorized for construction in Fiscal Year 1934. The P-1 type was developed by Portsmouth. It was a full double hull design that was essentially an enlarged Cachalot. The P-3 type was developed by Electric Boat and was a partial double hull with single hull ends, a refinement of an earlier hull type used on the USS Dolphin (SS-169). Six submarines of the P-5 type were authorized for construction in Fiscal Year 1935. The Navy thought the Electric Boat design to be the better of the two, so all six boats were built to the partial double hull pioneered by Electric Boat. All ten submarines carried the same armament and propulsion machinery, and had the same operating characteristics and thus were considered to be the same class. The five boats of this class built at the government owned Portsmouth Navy Yard and Mare Island Navy Yard were the last submarines in the USN to be built to a riveted construction method. While welding was used in non-critical areas, riveting was still used on the inner and outer hulls. Design conservatism and the economic realities of the Great Depression drove this decision by Portsmouth. The five boats built by Electric Boat were the first all welded submarines in the USN. All submarines built for the USN after this class by all yards were of all-welded construction. In general, they were around long and diesel-electric powered. Displacement was 1,934 tons submerged for the first four boats, 1,998 tons for the later ones. The goal of a 21-knot fleet submarine that could keep up with the standard-type battleships was still elusive. The relatively high surfaced speed of was primarily to improve reliability at lower cruising speeds. A major improvement essential in a Pacific war was an increase in range from Perch onwards, nearly doubling from to at . This allowed extended patrols in Japanese home waters, and would remain standard through the Tench class of 1944. Although it proved successful with improved equipment beginning with the Tambor class of 1940, the diesel-electric drive was troublesome at