Article Summary: On April 10, 1963, the USS Thresher (SSN-593), a state-of-the-art nuclear attack submarine, sank during deep-diving tests 220 miles off Cape Cod, claiming the lives of 129 crew and shipyard personnel.
Key Point #1 – A suspected piping failure and ballast system malfunction led to the submarine exceeding its crush depth, imploding instantly. The tragedy prompted the SUBSAFE program, a rigorous overhaul of U.S. Navy submarine safety protocols.
Key Point #2 – Decades later, recently declassified SOSUS data sheds new light on the disaster. The USS Thresher remains a stark reminder of the dangers of deep-sea exploration and the lessons learned in submarine engineering.
USS Thresher: The Tragic Story Behind the Navy’s First Lost Nuclear Submarine
The USS Thresher (SSN-593) was the lead boat of her class of nuclear-powered attack submarines in the United States Navy. She was the US Navy’s second submarine named after the thresher shark.
The other USS Thresher (SS-200) was the most decorated United States Navy submarine of World War II, with 15 battle stars and a Navy Unit Commendation.
On April 10, 1963, Thresher sank during deep-diving tests about 220 miles east of Cape Cod, Massachusetts, killing all 129 crew and shipyard personnel aboard. Her loss was a watershed for the US Navy, leading to the implementation of a rigorous submarine safety program known as SUBSAFE.
The first nuclear submarine lost at sea; Thresher was also the third of four submarines lost with more than 100 people aboard, the others being the French Surcouf, sinking with 130 personnel in 1942, USS Argonaut, lost with 102 aboard in 1943, and Russian Kursk, which sank with 118 aboard in 2000.
After the terrible sinking and the loss of the entire crew, the Navy struggled to find the answers to why she sank.
And even today, different theories persist.
The Fateful Shake-Down Cruise
Lieutenant Commander John Wesley Harvey was named the new commander. He had a wealth of experience, including participating in the Nautilus expedition under the ice at the North Pole. He was considered an up-and-coming officer in the Navy.
The reactor was started at 0345 hrs on April 9, 1963, and by 0730, she was ready to go. She started her final voyage. Of the 129 personnel on board were 12 officers and 96 enlisted men of the submarine’s crew; a Submarine Force staff officer; three officers and 13 Portsmouth yard civilian employees; a Naval Ordnance Laboratory specialist; and three civilian factory representatives.
At 0949 hrs, east of Boston, she rendezvoused with the submarine rescue ship USS Skylark (ASR-20), which would accompany the submarine on her trials. The 205-foot Skylark carried divers and specialized equipment to enable her to moor over a stricken submarine and rescue personnel with her cable-lowered rescue chamber.
The sub made a shallow dive and communicated with the Skylark via an underwater telephone called the UQC. The captain then radioed to the Skylark to rendezvous with her about 220 miles east of Cape Cod.
Early on the morning of April 10, the Thresher came up to periscope depth, and an hour later, the captain radioed that he was taking the boat to test depth, which is the maximum operating depth for the submarine (1,300 feet).
The two vessels kept in contact through the various depths along the way. At 0912 hours, Skylark crew members remember the Thresher radioing back, “Experiencing minor problem … Have positive angle … Attempting to blow.” And, “Experincing minor difficulty … Have positive up angle … Attempting to blow … Will keep you informed.”
At 0914, the Skylark asked for the sub’s course and bearing, and repeated it several times. At 0917, the final garbled message from the Thresher included the words “test depth.” It was later deduced that the message was probably “exceeding test depth.”
Just seconds later, the Skylark’s commanding officer, Lieutenant Commander Stanley W. Hecker, heard what sounded like “a ship breaking up … like a compartment collapsing.”
The Navy initiated a massive search, but all they found was an oil slick, rubber gloves, and thick yellow plastic.
The Court of Inquiry Of the Thresher Sinking
In April – June 1963, the Navy opened a court of inquiry over the sinking of the boat. Headed by Vice Admiral Bernard L. Austin, the court interviewed 120 witnesses, reviewed 1,700 documents, and examined 255 exhibits.
USS Thresher Artist Rendering. Image Credit: Creative Commons.
Despite not having found the boat yet, the court made 55 opinions and 19 recommendations. Without direct evidence, that is rather hard to do. After a review of the evidence, the Court of Inquiry determined that the Thresher sank due to a piping failure, subsequent loss of power, and the inability to blow ballast tanks rapidly enough to avoid sinking.
However, recently released SOSUS (Sound Surveillance System) data, which was installed at the time to listen for inbound Soviet submarines, contained an acoustical record of the loss of the Thresher. At 0909 on April 10, there was a frequency change in the pumps that moved water to cool the reactor, followed shortly after by attempts to blow the main ballast with no effect. At 0911, all the noise from the pumps for water and air stopped.
It is possible the Thresher’s attempts to blow the ballast may have been prevented by the ice that formed on the compressed air valves on the main ballast tanks. This issue cropped up before with other nuclear subs working at depth.
USS Thresher. Image Credit: Creative Commons.
At this point, the sub continued to sink and rapidly approached its crush depth. When the final collapse came, it happened in about 100 milliseconds, too fast for anyone on the ship to see or feel it. The inward force of the ship imploding was greater than the force of the Hiroshima atomic bomb.
The Thresher then came apart in six main pieces and sunk to 8,430 feet beneath the sea with the remains of her crew.
She was supposed to be the technical marvel of the newest generation of submarines, with a massive sonar system, the new antisubmarine missile SUBROC, and more.
About the Author:
Steve Balestrieri is a 19FortyFive National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing for 19FortyFive, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications.
