Thresher

USS Thresher, lead ship of a class of 3700-ton nuclear-powered attack submarines, was built at Portsmouth Naval Shipyard, Kittery, Maine. Commissioned in August 1961, she conducted lengthy trails in the western Atlantic and Caribbean areas in 1961 and 1962, providing a thorough evaluation of her many new technological features and weapons. After the completion of these test operations Thresher returned to her builders for overhaul. On 10 April 1963, after the completion of the work, Thresher began post-overhaul trials. Accompanied by the submarine rescue ship Skylark ASR-20 she transited to an area some 220 miles east of Cape Cod, Massachusetts and started deep diving tests. As these proceeded garbled communications were received by Skylark indicating trouble aboard the submarine. It gradually became apparent that she had sunk taking the lives of 129 officers, crewmen and civilian technicians. After an extensive underwater search utilizing the bathyscaph Trieste, oceanographic ship Mizar, and other ships Thresher's shattered remains were located on the sea floor some 8400 feet below the surface. Deep sea photography recovered artifacts and an evaluation of her design and operations permitted a Court of Inquiry to determine that she had probably sunk due to a piping failure, subsequent loss of power and inability to blow ballast tanks rapidly enough to avoid sinking.