KITTERY, Maine — The first sign of trouble for the USS Thresher was a garbled message about a “minor difficulty” after the nuclear-powered submarine descended to about 1,000 feet on what was supposed to be a routine test dive off Cape Cod.
Minutes later, the crew of a rescue ship made out the ominous words “exceeding test depth” and listened as the sub disintegrated under the crushing pressure of the sea. Just like that, the Thresher was gone, along with 129 men.
Fifty years ago, the deadliest submarine disaster in U.S. history delivered a blow to national pride during the Cold War and became the impetus for safety improvements. To this day, some designers and maintenance personnel listen to an audio recording of a submarine disintegrating to underscore the importance of safety.
“We can never, ever let that happen again,” said Vice Adm. Kevin McCoy, an engineer and former submariner who now serves as commander of the Naval Sea Systems Command in Washington, D.C.
This weekend, hundreds who lost loved ones when the Thresher sank will gather at memorial events in Portsmouth, N.H., and Kittery, Maine.
Built at Portsmouth Naval Shipyard in Kittery, and based in Groton, Conn., the first-in-class Thresher was the world’s most advanced fast attack submarine when it was commissioned in 1961.
Featuring a cigar-shaped hull and nuclear propulsion, the 278-foot-long submarine could travel underwater for unlimited distances. It could dive deeper than earlier submarines, enduring pressure at unforgiving depths. It was designed to be quieter, to avoid detection.
On April 10, 1963, the submarine already had undergone initial sea trials and was back in the ocean about 220 miles off Cape Cod, Mass., for deep-dive testing. Some submariners are baffled by the initial message about a minor difficulty because it’s believed a brazed joint on an interior pipe had burst — a problem anything but minor.