USS Thresher (SSN 593) 57th Anniversary

NAVSEA commemorates the 57th anniversary of the loss the nuclear powered attack submarine USS Thresher (SSN 593) which sank during sea trials off the coast of Massachusetts April 10, 1963.
On the anniversary of the sinking, NAVSEA remembers the 129 souls lost aboard the Thresher, including 16 of NAVSEA’s own Portsmouth Naval Shipyard workers and the importance of continually improving the safety of current systems.
NAVSEA Executive Director, Mr. James Smerchansky commenting about the loss two years ago of the Argentine submarine ARA San Juan (S-42) said, “It is a reminder that if you do not have diligent processes and people in place to follow those and execute those, that bad things are still capable of happening.”
Sinking of the Thresher
On the morning of April 10, 1963, Thresher sank during deep-diving tests about 190 nautical miles east of Boston, killing all crew and shipyard personnel aboard. She was commanded by Lt. Cmdr. John Wesley Harvey at the time. The day before, Thresher got underway from Portsmouth Naval Shipyard for sea trials following a nine-month post-shakedown maintenance availability. The boat had been re-certified and undocked April 8.
Two days later on April 10 at 6:30 a.m., Thresher commenced deep-dive trials. Following standard practice, Thresher dove slowly as she traveled in circles under the submarine rescue ship USS Skylark (ASR-20) to remain within communications distance, pausing every 100 feet of depth to check the integrity of all systems.
As Thresher neared her test depth, Skylark received garbled communications over the underwater telephone.
“...minor difficulties, have positive up-angle, attempting to blow,"
Then a final, even more garbled message, that included the number 900.
When Skylark received no further communication, surface observers gradually realized Thresher had sunk. Shortly thereafter, a sound was heard by Skylark which was monitoring the tests, indicating a possible implosion of the Thresher.
Thresher was the first nuclear submarine lost at sea and the first nuclear submarine of her class.
Following the incident, President John F. Kennedy ordered all flags to be flown at half-staff April 12-15 in honor of the lost sailors and shipyard personnel. Thresher was struck from the Naval Vessel Register April 16. Having been lost at sea, Thresher was not decommissioned by the U.S. Navy and remains on "Eternal Patrol.”
Investigation
A Navy Court of Inquiry was convened to investigate the sinking. Deep-sea photography, recovered artifacts, and an evaluation of her design and operational history led the Court of Inquiry to conclude Thresher had probably suffered the failure of a salt-water piping system joint which relied heavily on silver brazing instead of welding. High-pressure water spraying from a broken pipe joint may have shorted out one of the many electrical panels, causing a shutdown “scram” of the reactor, which in turn caused loss of propulsion. The inability to blow the ballast tanks also contributed to the sinking and was later attributed to excessive moisture in the submarine's high-pressure air flasks, moisture which froze and plugged the flasks' flow-paths while passing through the valves. The submarine, unable to maneuver to maintain depth or blow it ballast tanks to surface, descended to crush depth and imploded.
During the 1963 inquiry, Admiral Hyman Rickover stated:
"I believe the loss of the Thresher should not be viewed solely as the result of failure of a specific braze, weld, system or component, but rather should be considered a consequence of the philosophy of design, construction and inspection that has been permitted in our naval shipbuilding programs. I think it is important that we re-evaluate our present practices where, in the desire to make advancements, we may have forsaken the fundamentals of good engineering."
When the Court of Inquiry delivered its final report, it recommended that the Navy implement a more rigorous program of design review and safety inspections during construction. The sinking of this submarine was a defining moment for the U.S. Navy, leading to the implementation of a rigorous submarine safety program launched in December 1963, known as SUBSAFE.
Naval Sea Systems Command uses the anniversary of the Thresher loss as the basis for annual mandatory SUBSAFE training. During the training, employees are reminded of the importance of SUBSAFE and are refreshed on the latest industry safety standards. This training helps maintain a continuous focus on safety.