On the eternal patrol

To the Editor:

This month will mark the 50th anniversary of a loss for the Silent Service. The morning of April 10th, 1963 saw the nuclear attack submarine USS Thresher (SSN-593) some 200 miles east of Cape Cod. Close to two years old, she had recently been overhauled, and was taking part in a deep-diving test. Civilian technicians were aboard, bringing her complement to 129 souls. With the submarine rescue ship USS Skylark on standby, Thresher slipped beneath the waves in what should have been a normal diving test. Tragically, this was not the case.

After a little over an hour, Skylark became informed of Thresher experiencing problems through its underwater telephone. The skipper, Lieutenant Commander John Harvey, stated the sub was experiencing a minor difficulty, and was attempting to blow Threshers' main ballast tanks. This statement was followed by the sound of compressed air. A minute or two later, Skylark received a garbled message with the clear words of "Test depth". Barely a minute passed when an eerie noise met the ears of those listening: the sound of collapsing compartments.

A widespread search of the seabed was soon conducted. Using resources such as the bathyscaph Trieste, the Navy was able to locate Thresher by June. As feared, the attack sub had imploded and broke apart, her crew lost.

Following an extensive investigation, the most plausible scenario was determined that through a piping failure, Thresher suffered severe flooding in her engine room. With electrical equipment shorted out, an automatic shutdown (scram) of the reactor would have occurred. There should have been steam left to surface, but this was not used (there's speculation that the Reactor Control Officer would have isolated the steam system, following procedure to restart the reactor). Thresher's main ballast tank system also failed. The investigation speculated that ice formed between the high pressure air and ballast tanks from the temperature drop during compression, preventing water expulsion. With no propulsion or expenditure of ballast, Thresher would have descended past test depth and imploded.

There were serious ramifications made after the tragedy. The procedure to handle the reactor following a scram was changed. There was also creation of the safety program known as SUBSAFE. As we pass through the tenth of April, I would ask for a moment of silence for the crew of the Thresher, having joined the Eternal Patrol.

Austin Sullivan

Stafford Springs, Conn. & Danville, Vt.


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