On April 10, 1963, the nuclear powered attack submarine, USS Thresher, was undergoing deep-diving tests 220 miles (350 km) east of the city of Boston, Massachusetts. At that time, Thresher was the fastest and quietest submarine in the world, and had the most advanced weapons system.
Thresher was built to find and destroy Soviet submarines, and she was outfitted with a new sonar system that could detect other vessels at a much greater distance. She was also equipped with the U.S. Navy's newest anti-submarine missile, the SUBROC. The UUM-44 SUBROC (SUBmarine ROCket) was a type of submarine-launched rocket deployed as an anti-submarine weapon. It carried a 5 kiloton nuclear warhead.
Launched from the Portsmouth Naval Shipyard in New Hampshire on July 9, 1960, Thresher was the prototype for what would have been 25 "Thresher class" ships. After conducting numerous sea trials in both the western Atlantic and the Caribbean, Thresher returned to Portsmouth on July 16, 1962 for a post-shakedown examination, and she remained in port until April 8, 1963.
At 8:00 a.m. on April 9, 1963, Thresher, commanded by Lieutenant Commander John Wesley Harvey, and with 129 crew onboard, sailed out of port and rendezvoused with the submarine rescue ship Skylark. Performing multiple dives, Thresher remained in underwater communication with Skylark. The next day, on April 10th, Thresher began deep-dive trials.
As she neared her test depth, Skylark received a call that said, "[We are] experiencing minor difficulty, have positive up-angle, attempting to blow," followed by a garbled message that included "900 N". Another transmission included the phrase, "exceeding test depth ..." then, Skylark detected a high-energy, low-frequency noise. That noise was characteristic of an implosion, which is where the hull of a vessel is crushed by the tremendous pressure of the seawater surrounding it.
Loss of life greater than 100 men - Thresher and the Kursk
The U.S. Navy quickly mounted an intensive search, using the oceanographic ship Mizar, and they soon found the shattered remains of Thresher's hull lying on the sea floor, at a depth of 8,400 ft (2,600 m).
The bathyscaphe Trieste, fresh from visiting the deepest place on earth, the Challenger Deep in the Mariana Trench, was brought from San Diego, California to survey and photograph the debris field.
A Naval Court of Inquiry was convened to determine the cause of the accident, and it concluded that the Thresher had suffered a failure in its salt-water piping system joint, which caused high-pressure water to spray out. This could have shorted out an electrical panel, which in turn would have caused the sudden shutdown, or "scram", of the nuclear reactor. Without the nuclear reactor, there would have been a loss of propulsion.
Thresher's regular Reactor Control Officer, Lieutenant Raymond McCoole, was on shore caring for a sick wife, and his replacement was just out of nuclear power school. The replacement followed standard procedures following a scram, but this meant that the reactor couldn't be restarted immediately, which in turn meant that Thresher couldn't climb her way out of the deep.
Following Thresher's sinking, Admiral Hyman Rickover created a "Fast Recovery Startup" procedure that allowed a nuclear reactor to be immediately restarted after a scram.
Thresher still should been able to surface by blowing her ballast tanks, but excess moisture in her high-pressure air flasks had frozen in the cold water at depth, and that ice plugged the flasks. After Thresher, air dryers were installed in subs to unfreeze the flasks and allow emergency blows.
With no propulsion and no way to blow her tanks, Thresher began to sink until she imploded at a depth of 1,300 to 2,000 feet (400 - 610 m). During a 1963 inquiry into the sinking, Admiral 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."
On July 29, 1960, 20 days after Thresher had been launched, the USS Scorpion was launched at Groton, Connecticut. By 1962, her permanent port was Norfolk, Virginia. During the early 1960s, Scorpion participated in numerous naval exercises with the U.S. 6th Fleet and NATO.
A story says that during a "Northern Run" in 1966, Scorpion entered an inland Russian sea and filmed the firing of a Soviet missile through her periscope, before running from approaching Soviet Navy ships.
On February 1, 1967, Scorpion entered the Norfolk Naval Shipyard for what should have been a nine-month-long overhaul, but Navy requirements forced this to be shortened, and the same emergency system that had doomed Thresher was not corrected on Scorpion.
Following a Mediterranean Sea deployment, Scorpion left the U.S. Naval base at Rota, Spain with 99 crewmen on May 16, 1968, along with the USS John C. Calhoun. Scorpion was sent to observe Soviet naval activities in the Atlantic Ocean in the vicinity of the Azores. Besides two fast 32-knot Soviet November-class hunter-killer subs, the Soviet convoy also included an Echo II-class submarine, as well as a Russian guided missile destroyer. Scorpion observed and listened to the Soviet ships, then prepared to head back to Naval Station Norfolk.
Sometime after midnight on May 21st, Scorpion sent a message that was picked up by a U.S. Navy communications station in Nea Makri, Greece, in which the commander said that he was closing on a Soviet submarine and research group "to begin surveillance of the Soviets", and was running at a steady 15 kn (17 mph, 28 km/h) at a depth of 350 ft (110 m). That was the last communication from Scorpion.
The U.S. Navy began a search for the missing ship that employed the methods of Bayesian search theory, which was initially developed during the search for a hydrogen bomb lost off the coast of Palomares, Spain in January 1966. Again, the oceanographic reserarch ship Mizar was brought in to locate Scorpion, and she found her on the sea floor about 400 nautical miles (740 km) southwest of the Azores, and at a depth of 9,000 feet (3,000 m).
The bathyscaphe Trieste II, a successor to its sister Trieste was also deployed, and she collected pictures of the crash site. Tapes from the U.S. Navy's underwater SOSUS listening system contained the sounds of Scorpion's destruction.
A Naval Court of Inquiry determined that Scorpion's hull was crushed by implosion forces as it sank below crush depth at an estimated depth of 1,530 feet (470 m). Following implosion, she continued to fall another 9,000 feet (2,700 m) to the ocean floor. The U.S. Navy declassified many of this inquiry's documents in 1993.
The U.S. Navy periodically visits the site of Scorpion's wreck to test for the release of any fissile materials from her nuclear reactor and two nuclear weapons. The reports show a lack of radioactivity, which indicates that the nuclear reactor fuel remains intact, and that the two nuclear-tipped Mark 45 anti-submarine torpedoes (ASTOR) are also intact.
Several books have been written about Scorpion's sinking. 1999's "Blind Man's Bluff: The Untold Story of American Submarine Espionage", written by two New York Times reporters, it reported that concerns about the Mk 37 conventional torpedoes carried aboard Scorpion had been raised in 1967 and 1968, before Scorpion left Norfolk for her last mission. Those concerns focused on the battery that powered the torpedoes.
In 2005, "Red Star Rogue: The Untold Story of a Soviet Submarine's Nuclear Strike Attempt on the U.S."was published, claiming that the U.S. had sunk Soviet submarine K-129 off the coast of Oahu on March 7, 1968, and that the sinking of Scorpion was in retaliation.
Released in 2006, "Silent Steel: The Mysterious Death of the Nuclear Attack Sub USS Scorpion" provided a detailed account of every mechanical problem on the submarine that was cited by the U.S. Navy, or that was mentioned in crew men's letters, but the work does not determine a cause for the accident. In 2008, "All Hands Down" attempted to link the sinking of Scorpion with the Pueblo incident, the John Anthony Walker spy ring, and the Cold War.
Documents only declassified in December 2018, showed that former U.S. Naval Reserve Commander, Dr. Robert Ballard, had approached the Navy in 1982 for funding to search with his new deep-diving robot submersible for the wreck of the Titanic. The Navy had a counter proposal: they would give Ballard the funds if he would first survey the wreck sites of the Thresher and the Scorpion and assess the radioactive threat.
Ballard's robotic survey showed that Thresher had indeed imploded, and his 1985 survey of Scorpion's wreck site revealed a large debris field, and what Ballard described as a ship that looked "as though it had been put through a shredding machine." Also, in 1985, Ballard located the wreck of the Titanic.
Having been "lost at sea," neither Thresher nor Scorpion have been decommissioned by the U.S. Navy, instead, like all lost submarines, they remain on "Eternal Patrol."