A class of shark which is harmless to man and easily recognizable because its tail is longer than the combined length of body and head.
(SSN-593: displacement 3,700 (surfaced), 4,300 (submerged); length 278 feet 6 inches; beam 31 feet 8 inches; speed 20+ knots; complement 100; armament 4 torpedo tubes; class Thresher)
The second Thresher (SSN-593) was laid down on 28 May 1958 by the Portsmouth (N.H.) Naval Shipyard; launched on 9 July 1960; sponsored by Mrs. Frederick B. Warder; and commissioned on 3 August 1961, Comdr. Dean W. Axene in command.
Following trials the nuclear attack submarine took part in Nuclear submarine Exercise (NUSUBEX) 3-61 off the northeastern coast of the United States from 18 to 24 September.
On 18 October; the submarine headed south along the east coast. After calling at San Juan, Puerto Rico, she conducted further trials and test-fired her torpedo system before returning to Portsmouth on 29 November. The ship remained in port through the end of the year and spent the first two months of 1962 evaluating her sonar system and her Submarine Rocket (SUBROC) system. In March, the submarine participated in NUSUBEX 2-62, an exercise designed to improve the tactical capabilities of nuclear submarines , and in antisubmarine warfare training with Task Group ALPHA.
Off Charleston, the ship undertook operations observed by the Naval Antisubmarine Warfare Council, before she returned briefly to New England waters from whence she proceeded to Florida for SUBROC tests. However, while mooring at Port Canaveral, the submarine was accidentally struck by a tug which damaged one of her ballast tanks. After repairs at Groton, Conn., by the Electric Boat Company, the ship returned south for more tests and trials off Key West. Thresher then returned northward and remained in dockyard hands through the early spring of 1963.
In company with Skylark (ASR-20), Thresher put to sea on 10 April 1963 for deep-diving exercises. In addition to her 16 officers and 96 enlisted men, the submarine carried 17 civilian technicians to observe her performance during the deep-diving tests.
Fifteen minutes after reaching her assigned test depth, the submarine communicated with Skylark by underwater telephone, apprizing the submarine rescue ship of difficulties. Garbled transmissions indicated that far below the surface things were going badly wrong. Suddenly, listeners in Skylark heard a noise "like air rushing into an air tank"--then, silence.
Efforts to reestablish contact with Thresher failed, and a search group was formed in an attempt to locate the submarine. Rescue ship Recovery (ASR-43) subsequently recovered bits of debris, including gloves and bits of internal insulation. Photographs taken by bathyscaph Trieste proved that the submarine had broken up, taking all hands on board to their deaths in 5,500 of water, some 220 miles east of Boston. Thresher was officially declared lost in April 1963.
Subsequently, a Court of Inquiry was convened and, after studying pictures and other data, opined that the loss of Thresher was in all probability due to a silver-brazed piping joint welding failure that flooded the engine room with water. Salt water spray on electrical components caused short circuits, reactor shutdown and loss of propulsion power. The main ballast tank blow system then malfunctioned, most probably owing to ice formation in the piping, and the inadequate blow rate could not overcome resulting in flooding in the engine room.
Thresher is in six major sections on the ocean floor, with the majority in a single debris field about 400 yards square. The major sections are the sail, sonar dome, bow section, engineering spaces, operations spaces, and the tail section.
Owing to the pressurized-water nuclear reactor in the engine room, deep ocean radiological monitoring operations were conducted in August 1983 and August 1986. The site had been previously monitored in 1965 and 1977 and none of the samples obtained showed any evidence of release of radioactivity from the reactor fuel elements. Fission products were not detected above concentrations typical of worldwide background levels in sediment, water, or marine life samples.
A bow view of the nuclear submarine Thresher (SSN-593), 24 July 1961. (USN 1057645)