The nuclear-powered Thresher-class boats immediately succeeded the Skipjack-class and were the first United States Navy (USN) submarines to truly feature a useful deep sea diving capability. The group operated under the banner of the service for the good part of thirty years and remembered as quiet, fast vessels with excellent endurance (thanks to their nuclear powerpacks)for their time - becoming an ultra-important addition to American underwater operations during the Cold War period (1947-1991). USS Thresher (SSN-593) was the lead ship of the class and ordered on January 15th, 1958. Her construction was assigned to Portsmouth Naval Shipyard and the keel laid down on May 28th of that year. Launched on July 9th, 1960, USS Thresher was formally commissioned on August 3rd, 1961, fighting under the motto of "Vis Tacita" ("Silent Strength").
Aboard were a typical collection of 112 enlisted and officers. Displacement reached 3,540 tons (short) when surfaced and 3,770 tons when submerged. Overall length was 279 feet with a beam measuring 32 feet and a draught of 26 feet. Power was from a single Westinghouse S5W (Submarine, 5th Gen, Westinghouse) reactor unit coupled to Westinghouse geared steam turbines developing 15,000 horsepower to 1 x shaft astern. The boat could make headway at 33 knots when submerged at about 15 knots when surfaced. The nature of submarine design had changed to the point that boats were now faster under the water than on it. Armament centered on 4 x 21" (530mm) torpedo tubes fitted amidships (angled so as to fire forward and out).
Her external arrangement was consistent with submarine design of the time: The bow section was rounded and the sail fitted well-forward and held the dive planes. The hull was tubular and slim while tapering towards the stern. At the stern was a cruciform plane arrangement for controlling the sub and a single propeller was visible. Noise reduction techniques were used throughout her construction where possible and an advanced sonar set was fitted in the upper bow.
USS Thresher had a relatively quiet service life, taking part in exercises, tests and training in her early going. She was a prominent player in deep sea testing as well as furthering the SUBROC Anti-Submarine Missile (ASM) program. A nine-month period saw the boat given a "post-shakedown" in 1962 and she returned to service in 1963.
Having left Portsmouth on April 9th, 1963, USS Thresher was lost, with all 129 hands aboard, on April 10th while undergoing a deep sea diving test (USS Skylark ASR-20 remained topside to assist in the exercise). The wreckage was located some 217 miles off the eastern coast of Cape Cod at a depth of 8,400 feet. After the loss of Thresher was verified, the Navy retired the Thresher name (though not officially decommissioned out of respect for the boat was forever out on an "eternal patrol"). With the loss of USS Thresher, the class was renamed to Permit after the second boat of the group, USS Permit. After review of the Thresher incident, the last three boats of the Permit-class were completed with "SUBSAFE" features to enhance survivability of these units while at-sea.
The Thresher / Permit-class was succeeded in USN service by the Sturgeon-class.