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April 10th 2008 marked the 45th anniversary of the sinking of USS Thresher and the tragic deaths of all 129 men onboard — 112 military and 17 civilians.

The USS Thresher, which gave its name to a new class of submarines, was launched at the Portsmouth Naval Shipyard, N.H., on July 9, 1960, and commissioned on August 3, 1961. A new class of nuclear submarines designed for optimum performance, the Thresher was capable of diving deeper and running quieter than non-nuclear powered submarines, since nuclear engines do not require air to generate large amounts of electricity thus allowing the submarines to remain submerged over longer periods of time and to move considerably faster. The absence of combustion engines eliminated the noise of pistons and made the submarines quieter.

Being the first submarine in its class, USS Thresher underwent two years of trials at sea, including in the Atlantic and Caribbean areas in 1961 and 1962, and demonstrated her ability to travel at a depth of 1300 feet at a speed of 20 knots. She took part in the Nuclear Submarine Exercise (NUSUBEX) 3-61 off the northeastern coast of the U.S. and in the NUSUBEX 2-62 exercise. While mooring at Port Canaveral, on her way to SUBROC tests, the USS Thresher was struck by a tug and one of her ballast tanks was damaged. Following repairs and an overhaul, in Connecticut, she headed south for further tests and trials off the coast of Florida and retuned north where, through early spring 1963, she remained at the dock.

According to public documents, on April 9, 1963 the USS Thresher, under the escort of the submarine rescue ship the USS Skylark, left the Portsmouth Naval Shipyard and headed out to the continental shelf off Cape Cod, Massachusetts, for deep diving tests. At 6:35 a.m., on the morning of April 10, the USS Thresher reportedly spotted the USS Skylark through her periscope and prepared to dive to her maximum depth. At 7:45 a.m. the crew reported that the submarine was at half her test diving depth. At 9:03 a.m. came the message informing of a “minor problem.” Shortly after this came another message — “Attempting to blow.” This would indicate that attempts were being made to lighten the submarine by blowing water out of the ballast tanks to allow the presumably weakened propellers to get it to the surface. At 9:18 a.m. the Skylark picked up sounds of compressed air blowing and the creaking of straining metal.

Two days after the disaster, President John F. Kennedy issued Executive Order 11104 ordering all U.S. Flags to fly at half-staff from April 12 to April 15.

The investigation conducted by the Navy pointed to several issues. The first was a problem with the silver-brazed joints that, because of poor brazing, allowed seawater to leak into the electronic controls of the nuclear reactor, which shut down. Also, due to a failure to meet design specifications, the ballast tanks were unable to empty themselves fast enough because of icing on the line strainers, which prevented the submarine from resurfacing. Finally, the diving exercise was conducted at depths that were beyond the USS Skylark’s ability to come to the submarine’s rescue.

The tragic loss of the USS Thresher and all men onboard prompted the Navy to undertake a massive program called SubSafe aimed at correcting design and construction problems with existing nuclear submarines, and those under construction or in the planning phase. Four issues were of particular concern to the Navy, namely design and construction; brazing; quality assurance; and procurement. Additionally, the need for deeper submersibles to collect data from the deep ocean floor and to conduct rescue operations resulted in new designs for deep submergence vehicles.

On the 25th anniversary of the accident, Vice Admiral Bruce Demars, then the Navy’s Chief submarine officer, said at a ceremony in Norfolk, Virginia, marking, “The loss of Thresher initiated fundamental changes in the way we do business ... We have not forgotten the lessons learned.”

Forty years after the accident, in early April 2003, Senators John E. Sununu and Judd Gregg, both from New Hampshire, introduced legislation, which unanimously passed in the Senate, commemorating this tragic event and calling for the creation of a memorial at Arlington National Cemetery.

The USS Thresher’s remains lie in six major sections at a depth of 8400 feet below the sea. Deep sea radiological monitoring operations were conducted in 1983 and 1986 and no fission products above typical concentrations were said to be detected.

Researched and written by museum volunteer Etienne Huygens.

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