Monday, April 10, 2006
The Thresher Disaster, April 10, 1963
Today in 1963, the USS Thresher, an American nuclear-powered attack submarine, sank in the Atlantic Ocean 220 miles east of Cape Cod, Massachusetts. Everyone on board-129 officers, crewman and civilians in all-went down with the ship. The disaster shocked the world and changed the way the US Navy operates and maintains its submarine fleet.
The Thresher was the lead ship in her class when she was commissioned in August, 1961. She used a proven reactor design (the S5W built by Westinghouse) and carried four torpedo tubes amidships to make way for new and powerful bow-mounted sonar equipment. The first year of her life was spent in sea trials.
In the spring of 1963, the Thresher was coming out of her first refit period and was made ready for post-overhaul trials. On April 9, the sub and her escort, the submarine rescue ship USS Skylark, head for open ocean off the coast of Massachusetts. The next morning, she began deep-diving tests, staying in contact with the Skylark via underwater telephone.
Communications between the two ships soon became garbled. From what they could make out, the crew of the Skylark reported that the Thresher had experienced some sort of difficulty and was still diving. Finally, a short message was understood clearly “...minor difficulties, have positive up-angle, attempting to blow.” It was the last message the submarine would ever send.
The water in the area of the sinking is over 8,000 feet deep, far deeper than any normal submarine could go. The Navy used the deep-diving bathyscaphe Trieste and oceanographic surface ships to find the wreckage. Eventually, the ship was found to be in six major sections; smaller debris was found in an area of about 134,000 square meters.
A Naval Court of Inquiry determined that the ship probably sank due to a failure in the saltwater intake and piping system on the ship, which in turn caused a loss of electrical power and a shutdown of the reactor. The ship could not blow her ballast tanks fast enough to avoid going past the crush depth of the hull. A theory was later put forth that the valves used to bleed air in the tanks may have frozen due to moisture in the tanks, but this is impossible to prove.
As a result of the loss of the Thresher, the Navy instituted the SUBSAFE program designed to ensure proper construction and maintenance of any component of a submarine which comes into contact with seawater. No SUBSAFE-certified ship has ever been lost.
The US Navy continues to monitor the area of the Thresher sinking to ensure that harmful levels of radiation are not released into the area. To this day, the nuclear fuel remains intact in the reactor and radiation remains typical of worldwide background levels.