The Permit-class submarine (known as the Thresher class until the lead boat USS Thresher was lost) was a class of nuclear-powered fast attack submarines (hull classification symbol SSN) in service with the United States Navy from the early 1960s until 1996. They were a significant improvement on the Skipjack class, with greatly improved sonar, diving depth, and silencing.[1] They were the forerunners of all subsequent US Navy SSN designs. They served from the 1960s through to the early 1990s, where they were decommissioned due to age.[2] They were followed by the Sturgeon and Los Angeles classes.

The Thresher class was one of several results from a study commissioned in 1956 by Chief of Naval Operations (CNO) Admiral Arleigh Burke. In "Project Nobska", the Committee on Undersea Warfare of the United States National Academy of Sciences, collaborating with numerous other agencies, considered the lessons of submarine warfare and anti-submarine warfare learned from various prototypes and experimental platforms.

 

General characteristics
Type	Nuclear submarine
Displacement	3,750 long tons (3,810 t) surfaced 4,300 long tons (4,369 t) submerged[1]
Length	278 ft 5 in (84.86 m)
Beam	31 ft 7 in (9.63 m)
Draft	25 ft 2 in (7.67 m)
Propulsion	1 S5W PWR 2 steam turbines, 15,000 shp (11 MW) 1 shaft
Speed	15 knots (28 km/h; 17 mph) surfaced 28 knots (52 km/h; 32 mph) submerged
Range	Unlimited, except by food supplies
Test depth	1,300 ft (400 m)
Complement	112
Sensors and processing systems	BQQ-2 sonar (later BQQ-5) Mark 113 Fire-control system (later Mark 117) Periscopes
Electronic warfare & decoys	ESM
Armament	4 × 21 inch (533 mm) torpedo tubes amidships 12-18 × Mark 37 torpedoes, later replaced by Mark 48s 4-6 × UUM-44 SUBROC anti-submarine missiles 4 × UGM-84 Harpoon anti-ship missiles