USS Thresher (SSN-593)

The USS Thresher (SSN-593) was an American fast attack submarine, which was powered by one S5W nuclear reactor. She sank by implosion during deep-diving tests on April 10, 1963, off the coast of Massachusetts, killing 129 officers and sailors. Extremely quiet, she had been designed to hunt Soviet submarines during the Cold War.

The USS Thresher had been launched on July 9, 1960, and commissioned on August 3, 1961. Built at Portsmouth Naval Shipyard, she was the lead submarine of her class of 14 boats. The other subs were Permit (SSN-594), Plunger (SSN-595), Barb (SSN-596), Pollack (SSN-603), Haddo (SSN-604), Guardfish (SSN-612), Flasher (SSN-613), Greenling (SSN-614), Gato (SSN-615), Haddock (SSN-621).

Below, the Thresher on sea trials in July 1961. It had a better hardened hull against explosive shock and introduced new sensors.

Technical Description

The design of USS Thresher (SSN-593) featured major advantages in five vital areas: depth, quieting, sonar, shock hardening, and weapons. She had a greater operating depth than her predecessors of the Skipjack class. Her pressure hull was made of HY-80 steel. Although it was the same type of steel used to produce the Skipjack submarines, to build the Thresher, the American engineers used improved welding techniques and piping, giving her a test depth of 400 m (700 feet).

To reduce the coolant piping and turbine noises, the sub machinery was isolated from the hull using a technique called "rafting", which the Royal Navy had developed for the Ton-class minesweeper. This arrangement decreased the sound transmission through the hull into the sea water. Thus, the twin steam turbines and related gearing were set up on a sound-isolating raft, not directly attached to the hull.

The most advanced electronic feature of the USS Thresher was her AN/BQQ-2 sonar system, which replaced the old BQR-2 and BQR-4 passive sonars. The BQQ-2 revolved around a 15-foot diameter sphere which was fitted with 1,241 hydrophones. Thus, it was capable of greater passive detection than older types of sonars as it could distinguish target noise from own ship and background sea noises. It also had an active acoustic pinging component.

Specifications

Type: attack nuclear submarine

Displacement: 4,369 tons (submerged), 3,810 tons (surfaced)

Length: 84.86 m (278 feet, 5 inches)

Beam: 9.63 m (31 feet, 7 inches)

Draft: 7.67 m (25 feet, 2 inches)

Propulsion: one pressurized water reactor S5W, which produced 11 MGW, with two steam turbines and one shaft, which generated 15,000 SHP.

Maximum Speed: 28 knots (submerged), 15 knots (surfaced).

Range: unlimited propulsion; food supplies for up to 90 days.

Compliment: 113 sailors and officers.

Armament: four 533-mm torpedo tubes, eighteen Mk-37 torpedoes.

Below, the AN/BQQ-2 sonar, the most advanced sonar of the time.

Front view of the SSN-593 on September 20, 1961.