Tang-class submarine

USS Gudgeon (the three distinctive shark-fin domes are the PUFFS sonar, one is just aft of the sail, below the flag).
Class overview
Name:	Tang class
Builders:	Portsmouth Naval Shipyard Electric Boat Company
Operators:	United States Navy
Preceded by:	Tench class
Succeeded by:	USS Nautilus (SSN-571) USS Seawolf (SSN-575) Skate class
Built:	1949–1952
In commission:	1951–1983
Completed:	6
Retired:	6
Preserved:	2
General characteristics
Type:	Submarine
Displacement:	1,560–2,050 long tons (1,585–2,083 t) surfaced 2,260–2,700 long tons (2,296–2,743 t) submerged
Length:	268 ft (82 m), extended to 287 ft (87 m), then to 302 ft (92 m)
Beam:	27 ft (8.2 m)
Draft:	17 ft (5.2 m)
Propulsion:	three GM 16-338 "pancake" diesel engines (3,400 shp (2,500 kW) total), replaced by three Fairbanks Morse 38D8-1/8 opposed piston engines (4,800 shp (3,600 kW) total), two electric motors (4,700 shp (3,500 kW)), four 126-cell batteries, two shafts
Speed:	15.5 kn (28.7 km/h; 17.8 mph) surfaced 18.3 kn (33.9 km/h; 21.1 mph) submerged
Range:	11,500 nmi (21,300 km) at 10 kn (19 km/h; 12 mph) surfaced
Endurance:	1 hour at 17.5 kn (32.4 km/h; 20.1 mph) on battery
Test depth:	700 ft (210 m)
Complement:	8 officers, 75 enlisted
Armament:	8 × 21 in (533 mm) torpedo tubes (6 forward, 2 aft), 26 torpedoes

The Tang-class submarines were an American class of submarines developed from the Greater Underwater Propulsion Power Program (GUPPY) conversion program for World War II submarines, which incorporated German Type XXI U-boat technology into the United States Navy's submarine design. They comprised the state of the art in post-World War II conventionally powered submarine design; some of their features were incorporated into the nuclear-powered submarines that replaced them in the 1950s and beyond.

Probably the most important innovation of the Tangs, and their primary advantage over contemporary GUPPY conversions, was an increase in test depth from 400 ft (120 m) to 700 ft (210 m), achieved with HY-42 (42,000 psi (290 MPa) yield strength) steel. The improved HY-75 steel would not appear until mid 1950s. This allowed the class to take advantage of deeper ocean conditions to evade sonar, as well as maneuver more safely at moderate depths.

An unsuccessful innovation of the Tang design was the General Motors EMD 16-338 lightweight, compact, high-speed "pancake" engine. Very different from the classic diesel engines that nearly all preceding submarines used, which were laid out with a horizontal crankshaft, this new engine had a vertical crankshaft, and the cylinders were arranged radially like an aircraft engine. Three of these 13 ¹⁄₂-foot-tall (4.1 m), 4-foot-wide (1.2 m), eight-ton engines could be installed in a single engine room, thus deleting an entire compartment from the submarine's design. The goal was to reduce overall length, as testing had shown that shorter submarines were more maneuverable, especially in depth. Four compact Guppy-type 126-cell lead–acid batteries were installed to provide a high sustained submerged speed. The overall design allowed for a 25 kn (46 km/h) top speed and possible future propulsion replacement with a Type XVII U-boat-derived hydrogen peroxide turbine, closed-cycle diesel system, or even a nuclear power plant. However, attempts to develop the first two systems were unsuccessful, and nuclear power plants proved too large to be accommodated in the Tang-class hull.