The U. S. Navy has lost two nuclear submarines in its history: the USS Thresher and the USS Scorpion. On April 10, 1963, the nuclear-powered attack submarine USS Thresher was undergoing deep dive tests 220 miles (350 km) east of the city of Boston, Massachusetts.
At the time, Thresher was the fastest and quietest submarine in the world, and it had the most advanced weapon system. It was equipped with a new sonar system that could detect other vessels at a much greater distance, as well as the U. Navy's newest anti-submarine missile, the SUBROC. The UUM-44 SUBROC (SubMarine Rocket) was a type of submarine-launched rocket deployed as an anti-submarine weapon, carrying a 5 kiloton nuclear warhead.
The Navy quickly undertook an intensive search, using the oceanographic vessel Mizar, and soon found the shattered remains of Thresher's hull at the bottom of the sea, at a depth of 8,400 feet (2,600 m). The Bathyscaphe of Trieste, fresh from visiting the deepest place on earth, the Challenger Deep in the Mariana Trench, was brought from San Diego, California, to study and photograph the rubble field. A Naval Court of Investigation was convened to determine the cause of the accident and concluded that Thresher had suffered a failure in the junction of the saltwater piping system, causing high pressure water to be sprayed. This could have caused a short circuit in an electrical panel, which in turn would have caused the nuclear reactor to shut down suddenly or quickly shut down.
Without the nuclear reactor, there would have been a loss of propulsion. On July 29, 1960, 20 days after the launch of Thresher, the USS Scorpion was launched in Groton, Connecticut. By 1962, its permanent port was Norfolk, Virginia. In 1966, Scorpion entered an inland sea of Russia and filmed the firing of a Soviet missile through his periscope before fleeing from Soviet ships.
On February 1, 1967, Scorpion entered the Norfolk Naval Shipyard for what should have been a nine-month review but Navy requirements forced it to be shortened and emergency systems were not corrected in Scorpion. After a deployment in the Mediterranean Sea, Scorpion left with 99 crew members from Rota Naval Base in Spain to observe Soviet naval activities in the Atlantic Ocean near the Azores. In addition to two fast November-class Soviet 32-knot hunter-killer submarines, the Soviet convoy also included an Echo II class submarine as well as a Russian guided missile destroyer. Scorpion watched and listened to the Soviet ships before preparing to return to Norfolk Naval Station.
However, it never arrived and its location remained a mystery for several months until it was eventually discovered after extensive research. The bathyscaphe Trieste II collected images of the scene of the accident and Navy's underwater SOSUS listening system contained sounds of Scorpion's destruction. The Navy regularly visits both Thresher and Scorpion wreck sites to test for any fissile material from their nuclear reactors and two nuclear weapons. Reports show a lack of radioactivity indicating that their nuclear reactor fuel remains intact and their two Mark 45 nuclear-tipped anti-submarine torpedoes (ASTOR) are also intact.
Ballard's robotic study showed that Thresher had indeed imploded and his 1985 study of Scorpion wreck site revealed a large debris field with what Ballard described as a ship that appeared to have been put through a crushing machine. The sinking of both Thresher and Scorpion remain officially unanswered questions but recent declassified files confirm that U. Navy did not cover up these mysterious accidents. Both submarines remain in Eternal Patrol having been lost at sea without being dismantled by U.