# Tang-class submarine

The Tang-class submarines were the first submarines designed (under project SCB 2) and built by the United States Navy after World War II. They incorporated the best features of the high-speed German Type XXI U-boat and the venerable U.S. Navy fleet submarine. The Tang class, with the fleet submarines converted under the Greater Underwater Propulsion Power (GUPPY) program, had much higher submerged performance than their predecessors, but were quickly surpassed by the nuclear-propelled submarines that entered service beginning in 1954. Six units in total were built.

## Design

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 the same High Tensile Steel (HTS; 42,000 psi (290 MPa) yield strength) as the Balao and Tench classes. 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, rated at 1,000 bhp. 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. Four 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, and had less submerged drag. 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.
When the boats went to sea in the early 1950s, the new engines did not work well. Their compact, high-speed design made them difficult to maintain, and they tended to leak oil into their generators. In 1956, the Navy decided to replace the pancake engines with three ten-cylinder Fairbanks-Morse opposed-piston 38D 8-1/8 diesels. These were similar to those of late-war World War II boats, but uprated from 1,350 shp (1,010 kW) to 1,600 shp (1,200 kW) each. To accommodate the larger engines, the boats had to be lengthened some nine feet in the engine room (three additional frames between frames 69 and 70). Accordingly, in 1957 and 1958, the first four Tangs were lengthened, while Gudgeon and Harder, still on the ways, were built to the new length with the new engines. This propulsion plant was used for almost all subsequent US conventional submarines.
The torpedo tubes were also redesigned. The six forward tubes now used air-powered piston ejection pumps, which forced a slug of water through a slide valve behind the torpedo to push it out, rather than the pulse of air used in previous designs. Because this design is somewhat quieter and does not release an air bubble every time a torpedo is fired, it has been used in all subsequent submarine designs throughout the world. The four stern tubes of previous classes were reduced to two shorter, simpler tubes that could not accommodate the longer anti-ship torpedoes and had no capability to actively eject torpedoes. Rather, they were designed for the Mark 27 and planned Mark 37 swim-out torpedoes.

## Boats in class

In October 1946, the first two boats were ordered. Tang was built at Portsmouth Naval Shipyard; Trigger at the Electric Boat yard in Groton, Connecticut. In 1947, contracts were awarded to Portsmouth for Wahoo and to Electric Boat for Trout. Then in 1948, a similar pair of contracts were awarded to Portsmouth for Gudgeon and to Electric Boat for Harder. They are named for six US submarines lost during World War II, of which most of their commanding officers were killed in action while combating Japanese surface vessels.
| Name | Hull number | Builder | Laid Down | Launched | Commissioned | Decommissioned | Period of service | Fate |
| Tang | SS-563 | Portsmouth Naval Shipyard | 18 April 1949 | 19 June 1951 | 25 October 1951 | 8 February 1980 | 28.3 | Transferred to Turkey 6 August 1987, decommissioned 2004, preserved as a museum |
| Trigger | SS-564 | Electric Boat | 24 February 1949 | 14 June 1951 | 31 March 1952 | 2 July 1973 | 21.3 | Transferred to Italy 10 July 1973, decommissioned 28 February 1986 and fate unknown. |
| Wahoo | SS-565 | Portsmouth Naval Shipyard | 24 October 1949 | 16 October 1951 | 30 May 1952 | 27 June 1980 | 28.0 | Scrapped 1984 |
| Trout | SS-566 | Electric Boat | 1 December 1949 | 21 August 1951 | 27 June 1952 | 2 January 1977 | 24.5 | Transferred to Iran 19 December 1978, transfer rescinded March 1979, in limbo 1979–92, USN sonar testbed 1994–2007, scrapped 2008 |
| Gudgeon | SS-567 | Portsmouth Naval Shipyard | 20 May 1950 | 11 June 1952 | 21 November 1952 | 30 September 1983 | 30.8 | Transferred to Turkey 1983, decommissioned 2004, preserved as a museum |
| Harder | SS-568 | Electric Boat | 30 June 1950 | 3 December 1951 | 19 August 1952 | 31 January 1974 | 21.4 | Transferred to Italy 18 August 1974, decommissioned and scrapped 1988. |
In 1967, Tang, Wahoo, Gudgeon, and Harder received an additional 15-foot (4.6 m) section (five additional frames between frames 42 and 43) to accommodate the BQG-4 Passive Underwater Fire Control Feasibility System (PUFFS) passive ranging sonar installation, with three tall domes added topside, and additional fire control equipment that enabled the use of the Mark 45 nuclear torpedo. This left the boats similar in size and capability to the GUPPY III conversions.

## Museum ships

Two boats of this class, TCG Pirireis (ex-Tang) and TCG Hizirreis (ex-Gudgeon), are preserved as museum ships in Turkey. Pirireis is at the İnciraltı Sea Museum in İzmir, and Hizirreis is at the Kocaeli Museum Ships Command in Izmit.