Loss of USS Thresher

USS Thresher (Naval Historical Center)

 On April 10, 1963 USS Thresher (SSN-593) lost while conducting post-overhaul sea trials about 200 miles off the coast of Cape Cod. Thresher was accompanied by the submarine rescue ship USS Skylark (ASR-20) on the morning of April 10 when she started deep-diving tests. As Thresher neared her test depth, Skylark received garbled communications over underwater telephone indicating "...minor difficulties, have positive up-angle, attempting to blow." When Skylark received no further communication, surface observers gradually realized Thresher had sunk. Publicly it took some days to announce that all 129 officers, crewmen, and military and civilian technicians aboard were lost with the submarine.

The Navy’s investigation concluded that while Thresher was operating at test depth, a leak had developed at a silver-brazed joint in an engine room seawater system; water from the leak may have short-circuited electrical equipment, causing cascading casualties. She sank in approximately 8,400 feet of water. The SUBSAFE program was initiated as a result of this accident.

Thresher insignia (Naval Historical Center)

Thresher was the first of a new class of submarine designed for optimum performance of sonar and weapons systems, but after her loss the class was referred to as the Permit (SSN-594) class.