What Sank The Thresher?

WHEN THE NUCLEAR-POWERED SUB marine Thresher was launched into New Hampshire’s Piscataqua River on July 9, 1960, she represented the latest in naval technology. The Thresher was the ultimate attack submarine, designed to hunt and destroy enemy vessels. She had a high-speed hull, the most powerful sonar in existence, special silencing features, and advanced weapons. She could also dive deeper than any other submarine, making it hard for her to be detected and destroyed. But the Thresher was fatally flawed.

On April 10, 1963, she sank 220 miles off the coast of Cape Cod with 129 men aboard. There were no survivors to tell what had happened in what was then the worst submarine disaster in U.S. history. Hours after the tragedy a Navy court of inquiry was formed to investigate and hear evidence about the sinking. The five-member court heard 120 witnesses and collected 255 exhibits over eight weeks, most of it behind closed doors. Ultimately the evidence filled 1,718 pages bound into twelve secret volumes. In Congress the Joint Committee on Atomic Energy also conducted an investigation, some of it in secret, and issued a nearly 200-page report. The Navy has recently declassified some of the information collected during the two investigations, but most of it remains secret.

The cause of the sinking has never been conclusively determined, but lessons learned from the disaster continue to shape the Navy’s practices and have a bearing on all industries, defense-related or not. What the investigations discovered, aside from the specifics of the disaster, was a catastrophic failure in the Navy’s basic approach to design, development, and testing. They pointed up a critical need for the creation and implementation of engineering standards that would be strictly observed, especially in the design and construction of complex and technologically sophisticated systems.

For a variety of reasons, most notably political pressure to deploy new weapons systems quickly in response to the Soviet threat, standards were relaxed in the rush to launch the Thresher . As NASA did more than twenty years later with the explosion of the space shuttle Challenger , the Navy found out the hard way that there is no substitute for the most extreme vigilance when new materials must be relied on and new environments mastered. Further, the disaster highlighted the limits of technology and the consequences that can result from not knowing those limits. After the sinking the Navy developed for the first time regulations governing deep submergence operations that specified such parameters as depth and speed.

“In the engineering area you’ve got to be very, very careful in designs,” says John T. Conway. “You need a systems engineering approach.” Conway is chairman of the Defense Nuclear Facilities Safety Board in Washington, D.C., which provides advice and recommendations to the President and Secretary of Energy regarding public health and safety at defense nuclear facilities. He is well qualified to comment on the Thresher sinking and its implications because he was an observer at the Navy’s court of inquiry and was executive staff director for the Joint Committee on Atomic Energy during its investigation.

What investigators discovered was that the Thresher —and every other nuclear submarine—had been built to two different levels of standards. The nuclear power plants were constructed to very exacting tolerances. But as Vice Adm. Bernard L. Austin, then president of the Naval War College and president of the court of inquiry, told the congressional committee, workers saw their design criteria in non-nuclear areas as goals, not requirements. To get the job done on time, they were allowed to take liberties that eventually proved fatal. This disparity between nuclear and non-nuclear components developed even though the technical specification requirements in the nuclear and non-nuclear areas were fairly similar.

“That’s not a systems approach,” Conway says. “To protect the overall safety, you can’t compartmentalize. The envelope must include the entire system.”

Ironically, an incident aboard the Thresher in May 1961 had led Adm. Hyman G. Rickover, father of the nuclear Navy, to adopt new, tougher standards for the nuclear components of submarines. In that incident a one-inch pipeline failed because of a faulty silver-braze joint. Alarmed, Rickover implemented his own standards. He required that all nuclear systems exposed to seawater be fully welded instead of silver brazed, that all saltwater systems be fabricated to the same standards as the rest of the reactor plant, and that all joints and piping passing through the reactor compartment be welded, even though the piping wasn’t under his commission.

Of course, the crew and others aboard the Thresher had no reason to suspect its seaworthiness as they set sail on the morning of April 9, 1963, following an extended overhaul at the Portsmouth Naval Shipyard. Normally only 108 men would have been aboard, but a number of observers had joined the crew for this trip. The passengers included 4 Navy officers, 13 civilian employees from the shipyard, and 4 civilian representatives of defense contractors that had provided equipment for the Thresher . For a variety of personal reasons, 4 more members of the Thresher crew remained in port.

Among those left behind was Frank DeStefano, who was in Washington, D.C., for an appointment in Rickover’s office regarding his candidacy for officers’ school. DeStefano was a chief machinist’s mate, and the Thresher was his first assignment after completing submarine training. He was only twenty-nine years old and had been a member of the crew for just a few months before the tragedy occurred. He said he never felt threatened while aboard the Thresher , nor did he suspect that anything might be amiss.

“You always have a lump in your throat when you’re aboard a submarine,” says DeStefano, now an insurance adjuster in Florida after a twenty-year career in the Navy during which he rose to the rank of lieutenant commander. “But I never felt the Navy put its men or ships at risk.”

Escorting the submarine on its final journey was the USS Skylark , a 205-foot submarine-rescue ship with Lt. Cmdr. Stanley W. Hecker in command. The two ships, as required, rendezvoused throughout the first day as the Thresher completed a series of tests. During the night the two vessels separated and made their way to a designated meeting point 220 miles off Cape Cod.

AS NAVY INVESTIGATORS were best able to reconstruct later, the Thresher began its final day early. At 6:35 A.M. , while floating 8,500 feet above the ocean floor, she came up to periscope level. The vessel’s commanding officer, thirty-six-year-old Lt. Cmdr. John W. Harvey, peered out at a sea that was calm with a slight swell. The wind was blowing from the north-northeast at seven knots. Visibility was nearly ten miles. No other ships but the Skylark were in the vicinity.

Harvey, a 1950 Naval Academy graduate, had begun his submarine career in June 1951, serving aboard the diesel-powered USS Sea Robin . He later completed nuclear-power training under Rickover and served aboard the USS Nautilus , the world’s first nuclear submarine, as reactor control officer. From the Nautilus he became chief engineer for a land-based submarine reactor prototype in Windsor, Connecticut, where Navy reactors are tested. The reactor was destined for the USS Tullibee , and when it was commissioned in late 1960, Harvey was aboard as engineer officer. In May 1961 he was promoted to lieutenant commander and became the executive officer of the nuclear-powered USS Seadragon . From there he was promoted to command of the Thresher .

At 7:47 on that final morning, the Thresher began its slow descent to test depth, something she had done forty times before. The test depth, or maximum depth, for the Thresher was 1,300 feet. As the ballast tanks filled with water and the nose planed downward, the ship’s hull creaked and moaned from the weight of the ocean pressing against it.

At 400 feet the Thresher leveled off. She contacted the Skylark at 7:52. The stop was routine and allowed time to inspect for leaks before proceeding to greater depths.

When no leaks were reported, Harvey ordered the Thresher down to her maximum depth. Checking his vessel’s dials at 8:09, Harvey noted that she was at half her test depth. The Skylark was notified. Sixteen minutes later the submarine was at 1,000 feet.

At 9:02, with his vessel cruising at eighteen knots, Harvey asked the Skylark for a course reading and then ordered a change: “Twenty degrees right rudder and five degrees down angle.”

As the Thresher continued her descent, a loud clap rang out. From the engine room Harvey learned that a pipe had burst. Ice-cold ocean water poured into the vessel, creating a cloaking fog and mist. Crew members struggled to stop the leak, but their efforts were hampered by the fact that the valves needed to stop the flow were scattered about the room. It was 9:09 A.M.

Harvey jumped into action. “Full speed,” he ordered. “Up fifteen degrees. Blow the main ballast.”

The sound of compressed air rushing through long pipes resounded throughout the submarine as she tried to blow seawater from her ballast tanks and surface. But after ninety seconds the pipes fell silent. Harvey didn’t know why. Investigators later discovered that the escaping air, under 4,500 pounds per square inch of pressure, had turned moisture in the pipes into ice, blocking escape vents. When a gas expands rapidly, it cools—a phenomenon overlooked by the submarine’s designers.

Suddenly the vessel’s lights flickered and the main coolant pumps went quiet. Water soaking the vessel’s electrical circuits had caused a power outage, leading to an automatic shutdown of the reactor. The Thresher was without her main propulsion system.

To keep the Thresher moving forward and upward while crewmen scrambled to restart the reactor, Harvey gave an order to unclutch the main turbine and switch to the submarine’s battery-powered backup motor. Even at full throttle, top speed was a mere five knots.

“Experiencing minor difficulties. Have positive up angle. Am attempting to blow. Will keep you informed,” the Thresher reported to the Skylark at 9:13.

As the Thresher continued to drift forward, the crew shut down all unnecessary equipment to conserve power. A few moments later Harvey ordered a second blowing of the main ballast tanks. Again the crew could hear the pressurized air rushing through the pipes, but after sixty seconds the pipes fell silent once more because of ice blockage.

Alarmed at what was occurring, the Skylark attempted to contact the Thresher at 9:15 for an update, asking, “Are you in control?” There was no immediate reply. Two minutes later the Skylark received a garbled message. The only words that could be understood were “exceeding test depth.”

Aboard the Thresher the engineroom leak had grown to more than two inches in diameter, because of the tremendous pressures of the depth, and had become a forceful stream that was filling the vessel. Harvey’s attempt to maneuver the ship to safety ended as the auxiliary power ran out and the reactor remained shut down. The ship lost its forward momentum, slowed, and then began to drift backward and downward.

At 9:17 the Thresher sent another message. All that could be heard aboard the Skylark was the words “nine hundred north.” Some aboard the Skylark heard the sound of a ship breaking up. Navy listening devices ashore later confirmed “a high energy, low frequency noise disturbance of the type which could have been made by an implosion.”

Below its test depth the Thresher ’s hull had become like taffy, bending and twisting until the submarine collapsed into itself. The violent action split the hull into three main pieces: the bow section, the stern section, and the shielded reactor compartment. Some of the twisted and scattered remains were later recovered by Navy search vessels.

After two months of painstaking investigation, the court of inquiry singled out only one individual for criticism: Hecker, the Skylark ’s skipper. He was cited for failing to inform higher authorities of the full extent of the Thresher ’s problems in a timely manner—even though he had been under strict orders not to break radio silence. The court decided, however, that his action had in no way contributed to the loss of the submarine. The incident cost Hecker a promotion, although he remained a career Navy officer. He later commanded the submarine Sea Lion and served as deputy director of the Navy’s submarine and diving safety programs. Five years after the Thresher , in May 1968, Hecker again played a key role in a nuclear submarine sinking when he discovered and reported the USS Scorpion missing in the Atlantic with 99 men aboard.

In discussing the Thresher , a trace of bitterness comes to Hecker’s voice when he recalls his treatment and punishment by the court of inquiry. “There wasn’t a damn thing I could have done,” says Hecker, who is now retired in Mississippi. “They felt that perhaps we could have alerted our superiors sooner. Perhaps.”

While Hecker’s actions were of some interest to both naval and congressional investigators, their main goal was to thoroughly review the nuclear submarine program in light of the Thresher incident. The program had been going full throttle for years, seeking to deploy .submarines that could go faster, dive deeper, and stay submerged longer in order to keep pace with the Soviets. The Navy was also under political pressure to build its submarines quickly and inexpensively. Many had no doubt that the Navy could fulfill this mission, especially after the success of U.S. submarines during World War II. Some observers, however, think that the Navy’s apparent success in that war sowed the seeds of the Thresher disaster. While U.S. subs had proven to be very effective weapons, nearly a fifth of them (52 out of 288) had been lost during the war. Rickover believed that shoddy workmanship had caused some World War II submarine sinkings. He cited defective welding, which he said made the submarines susceptible to depth-charge attacks.

Adding to the Navy’s sense of security with its submarine technology was the remarkable Nautilus . After joining the fleet in September 1954, the Nautilus proved to be an awesome weapon. She was unbelievably adept at destroying targets while evading attack. By the fall of 1957 the Nautilus had been exposed to 5,000 dummy attacks in U.S. exercises. A conventional submarine would have been “killed” three hundred times; the Nautilus was killed three.

The Nautilus ’s ability to avoid detection and destruction had caused the Navy to reconsider its submarine warfare strategy. Fearing that the Soviets would soon be able to duplicate Nautilus technology, the Navy designed a new class of nuclear-powered attack submarines capable of hunting and destroying enemy subs. The Thresher was the first of this new generation.

The Thresher ’s keel was laid on May 28, 1958. She measured 278 feet 6 inches long. Her hull was 31 feet 8 inches at its widest and was built with advanced HY-80 steel, which had a yield strength of 80,000 pounds per square inch. She displaced 3,705 tons when surfaced and 4,311 when submerged. Her surface speed was 15 knots; submerged, 28 knots. She had 4 torpedo tubes and 23 torpedoes. The Thresher was also armed with submarine rockets, which were launched like ordinary torpedoes but could race to the surface, fly through the air for miles, and then destroy enemy submarines or surface vessels.

After her commissioning on August 3, 1961, the Thresher underwent nearly a year of trials and tests in the Atlantic. Key among them were shock tests, which subjected the submarine to a series of explosions outside her hull in order to determine the vessel’s ability to withstand an attack. The new hull performed as expected during the tests, but the Thresher sustained damage as the explosions shifted equipment and stressed piping, joints, rivets, and other structural items.

Immediately after the tests in July 1962, the Thresher returned from Key West to the Portsmouth Naval Shipyard for what would be her final overhaul. The Thresher was the first and, as it later turned out, only nuclear submarine designed and built by Portsmouth since its founding as the nation’s original naval shipyard in June 1800. The 278-acre facility, located on an island on the Maine-New Hampshire border, had built eighty-two submarines during World War II. After the war it continued to contribute, now to the nuclear program. But it was often the target of critics, especially Rickover, who once called it “the most inefficient nuclear submarine yard, public or private, I have ever seen.” (Today the shipyard is being studied for possible shutdown by the Defense Base Realignment and Closure Commission and is the subject of an ongoing border dispute between the two states it straddles.)

During the overhaul the Thresher ’s hull was cut open in many places to allow for the removal and repair of heavy equipment. Of particular concern to the repair crews was the Thresher ’s silver-brazed piping. Silver brazing is the process of joining metals with silver solder instead of the more common lead solder. Silver solder melts at a higher temperature and gives a stronger bond. There were hundreds of silver-braze joints in the Thresher , many on pipes that penetrated the craft’s hull.

ON AUGUST 28, 1962, Adm. R. L. Moore, Jr., deputy chief of the Navy’s Bureau of Ships (BuShips), wrote a detailed letter to the shipyard’s commander expressing concern about the Thresher . Moore requested that the piping be subjected to both visual and nondestructive testing during the overhaul to ensure that it met Navy standards. Specifically, Moore requested that at least one inspection team test the joints using ultrasonic equipment. Ultrasonic testing was a new and little-tried technology at the time, but it held great promise. “The intent of the Bureau,” Moore wrote, “is that the inspection directed by this letter shall serve as a pilot test of silver-brazed piping inspections in operating ships which were constructed without benefit of present-day quality controls.”

This was not the first time the Thresher had been subjected to ultrasonic testing. From April 16, 1962, to May 21, 1962, while at the Electric Boat Company shipyard in Groton, Connecticut, in preparation for shock tests, 115 silver-braze joints in the Thresher ’s hydraulic systems had been ultrasonically tested. “Of these,” the court of inquiry later reported, “eight did not meet all requirements of then existing bonding standards. Two of these joints were replaced. The remaining six were accepted after decision by the Bureau of Ships that the existing deficiencies were not such as to warrant repairs.”

During the final overhaul an ultrasonic exam of 145 joints (out of about 3,000 on the entire ship), completed by November 29, 1962, resulted in a rejection rate of 14 percent. Despite these results, Portsmouth “did not aggressively pursue the ultrasonic inspection of sil-braze joints in Thresher ,” the court of inquiry determined, even though the rejection rate “was a clear indicator that additional action was required.”

The problem was that there were no clear-cut procedures for correcting the faulty joints. During the Atomic Energy Committee investigation, Sen. John O. Pastore, the chairman, asked how it was possible that such defects could be ignored. Vice Admiral Austin, president of the court of inquiry, replied that he had quizzed the shipyard’s commander about the very same thing.

“We did question him, sir, and he, in retrospect, admitted that he thought he should have looked into this more thoroughly, but at the time he did not consider it a dangerous situation. They were trying to meet a deadline date for the completion of the ship’s availability, and to have gone further with the testing would have required unlagging of piping and delaying the ship and running up the cost of the overhaul and, you know, the many attendant things when you delay the ship,” Austin said.

Pastore asked who had empowered the shipyard commander to make such a decision. Rear Adm. William A. Brockett, chief of BuShips, replied that Navy procedure allowed shipyard commanders to make such decisions because they were on-site and had hands-on knowledge of the ships. Further, Brockett argued that Moore’s letter didn’t require the shipyard commander to do anything more than try ultrasonic testing. In fact, after receiving the letter, Portsmouth wanted to test only those joints that it had repaired. The Bureau of Ships would not allow so minimal a testing program. Eventually a compromise was reached that required the testing of only those joints that time would allow and that were easily accessible. In hindsight, Brocket! said the shipyard commander was also wrong in not immediately reporting the results to his superior officers. The shipyard’s report on the Thresher overhaul didn’t arrive at the Bureau of Ships until after the sinking.

Expanding its inquiry beyond the Thresher , the court of inquiry found “indications of high rejection rates” of silver-braze joints at all shipyards. “There is a need to re-emphasize and improve, where indicated, the quality assurance program in shipbuilding and repair yards,” it concluded, and “vigorous steps should be taken to correct [it].”

In addition to the Thresher , the court found that “serious failures” of silverbraze joints had occurred in the submarines Barbel, Skate, Snook, Sculpin , and Ethan Allen . The most significant of these incidents involved the Barbel , a diesel-powered attack submarine built at Portsmouth and commissioned on January 17, 1959. She nearly sank on November 30, 1960, after a five-inch silver-braze joint failed. According to the Barbel ’s, deck log, now on file with the National Archives, the engine room flooded shortly after 10:00 A.M. , when a seawater pipe broke. The submarine was hastily rigged for collision as the captain ordered an emergency surfacing. The flooding knocked out the submarine’s gyrocompass, two main generators, trim system, trim pump, and primary pump as well as a seawater circulating pump. There were no casualties.

LATER IT WAS DETERMINED that the Barbel joint had failed because stainless steel, not silver, had been used to make the braze. The incident focused attention on the inadequacy of Portsmouth’s quality control on silverbraze joints, but according to the court of inquiry, “the information was not shared and acted upon.” Procedures were not reviewed and corrected, unlike today, when thousands of audits and inspections take place each year. As the court of inquiry stated, “deficiencies which probably caused Thresher ’s loss … could have been reduced by thorough and imaginative analysis and timely dissemination of all information to be had from the Barbel and other casualties.”

Another issue reviewed by congressional investigators was the Navy practice of rotating officers from assignment to assignment. During the Thresher ’s final overhaul four of her top officers were reassigned. All had played important roles in the overhaul, and their departures between November 1962 and January 1963 interfered with the repair and inspection process. “The substantially contemporaneous transfer of Thresher ’s Commanding Officer, Executive Officer, Ship’s Superintendent and Assistant Ship’s Superintendent in the final portion of her post shakedown availability was not conducive to optimum completion of the work undertaken,” the court of inquiry determined.

Cmdr. Dean L. Axene, the Thresher ’s first commanding officer, was reassigned to the John C. Calhoun , a new nuclear-powered Polaris-class submarine then under construction. Axene protested, arguing that he should stay through the overhaul period. But in January 1963 he was succeeded as commanding officer by Harvey, his former shipmate.

Axene’s participation could have been critical to a successful overhaul. He had written a letter on November 16, 1962, evaluating the submarine’s first year of operation and citing some problems. For instance, he said the Thresher ’s unique shape made her hard to handle on or near the surface. Also, Axene said, the ship was too complex in many areas. Most notably, he wrote: “In my opinion the most dangerous condition that exists in Thresher is the danger of salt water flooding while at or near test depth.”

NOW LIVING IN FLOR ida and retired after a long career during which he rose to the rank of rear admiral, Axene is reluctant to talk about the Thresher , explaining that he said what he had to say during the court of inquiry. “The loss of the Thresher was investigated, studied, and what have you,” he says. “I don’t like to see it dredged up again. She was a great ship with a lot of good men. Her sinking advanced submarine technology. That accident or one like it was going to happen one day.”

As part of its investigation, the court of inquiry conducted several tests of standard submarine equipment. In one test it witnessed firsthand the vulnerability of the submarine’s electrical switchboards. During a dramatic dockside experiment, a strong jet of water was directed at such a switchboard. It shorted out, proving that the design was safe only from dripping water.

During another, more revealing test the filters (known as strainers) on the compressed-air lines of the USS Tinosa , sister ship to the Thresher , were blocked to simulate conditions the Thresher might have experienced at test depth. Within thirty seconds ice formed and caused a rupture of a seawater pipe. The Thresher crew had no idea that this could occur, because Atlantic Fleet Submarine Force instructions had not required the Thresher to test her sea valves on deep dives before April 10. Further, the Navy had not changed the blowing-system requirements of its submarines, even though their missions were taking them to ever greater depths. Even more astonishing, the strainers on which the ice had formed were not required by the ship’s design. They had been added by the valve’s manufacturer in order to protect the sensitive valves against damage from particulants, such as dust, dirt, and rust particles. The potential impact that the strainers might have on the overall system was never evaluated.

Another critical lesson of the disaster was the determination by investigators that too many seawater pipes penetrated the hull, especially for a deep-diving vessel subjected to extreme pressure. Water is vital to the functioning of a nuclear reactor and other operations. Ideally a submarine would have no pipes through the hull, but since that’s not possible, designers sought to minimize the number of pipes in future designs. Reactor operating procedures were modified so that any heat remaining in a reactor after a shutdown could be used to create steam for continued propulsion. In addition, later submarines were given an emergency blow system, separate from the regular ballast system, that allowed for a much faster ascent.

Finally, congressional investigators examined the workmanship and skills of the laborers who built the Thresher . Rickover testified that not only workers but inspectors responsible for upholding standards didn’t believe the standards were necessary. Admiral Brockett told the Atomic Energy Committee: “One of the things that we find is no matter how many pieces of paper we produce in Washington, you do not always find they are observed in the field. As a result, we are sending out audit teams to find out how well the instructions are being carried out.”

Brockett continued: “This quality control problem is a difficult one. If I can philosophize on that, the pride of workmanship of the individual mechanic is not enough even where it exists. It is too bad, but it is so. We have the hardest time trying to convince people of this fact.” Following the admiral’s lead, Rep. Chet Holifield said: “The pride of craftsmanship of the old trained artisan is gone. The young men are not going into these difficult artisan craftsmanship jobs to learn. They don’t have to. They join a union, and if they stay there so long somehow or other they get stepped up and they get to the point where they are drawing journeyman’s wages without the skills they had in the old days.”

Rickover told the congressional committee that he had not been personally convinced there was a problem with workmanship until he demanded that specifications for nuclear components be met. Then he had discovered “carelessness, looseness and poor practices.” Rickover went on to say that he had found it alarming that the court of inquiry, while acknowledging the application of higher standards in the nuclear area, had not recommended that the same standards be applied shipwide. He vigorously defended the integrity of the nuclear facilities built under his watch (Rickover asserted that it had not been proven that the Thresher lost propulsion, and true or not, it is unclear whether any amount of propulsion would have saved it) while criticizing the standards, procedures, and workmanship in other areas. “The high performance required of these ships, the exotic materials being used, the pushing of older materials to greater limits—all this, in my opinion, means the Navy cannot afford not to use higher standards throughout,” Rickover said.

When questioned on whether he had ever expressed his concerns about standards and quality to his superiors before the sinking, Rickover said that he had. He said senior officers believed that implementing tougher standards would have added to the costs of submarines, something they wanted to avoid. In fact, some nonnuclear standards were lowered to save money. But Rickover told congressional investigators that building submarines to standard would add only about 2 percent to the cost of each vessel.

“If you have good procedures, good specifications, and good people you will save money,” Rickover said. ”… If you buy one really good suit, it is better than two cheap suits. It is that sort of saving.”

Rickover had alluded to the potential dangers facing the Navy and other industries in an address to the National Metal Congress in New York City on October 29, 1962. In that speech he discussed the implementation of new technology: “We must accept the inexorably rising standards of technology and we must relinquish comfortable routines and practices rendered obsolete because they no longer meet the new standards. This is our never-ending challenge.”

A member of the Atomic Energy Committee asked Rickover if his public statements and other warnings had ever prompted a reply from his superiors. He replied that they had not. “Of course, there is another question you can ask me,” Rickover continued. “‘Why in light of this didn’t you do something? Why didn’t you come to this committee when with a strict interpretation of the law the committee is to be kept fully and currently informed?’ You might ask me this. I will tell you why. The issue had been raised with my superior in the Navy. I can’t come to a congressional committee with every technical issue I have. A congressional committee is not the best forum to air technical issues because you will get experts who will argue both sides of the issue convincingly. I did everything I could to point this out. At the same time I did everything I could to keep my own areas out of trouble. That is all I could do.”

When it had finished its work, the court of inquiry issued a public statement that said in part: “The evidence does not establish that the deaths of those embarked in Thresher were caused by the intent, fault, negligence, or inefficiency of any person or persons in the naval service or connected therewith.” Congressional investigators asked how it was possible that no one could be held at fault for the sinking. It was left to Rickover to answer on behalf of the Navy.

“Who is responsible? With the present Navy system, this is an almost impossible question to answer,” Rickover said, alluding to the frequent change of personnel and lack of procedure. “The nearest you can come is to say that ‘the Navy is responsible.’ In other words all you can do is point to a collectivity.”

In the wake of the disaster and investigations, the Navy took steps to clean house and implemented many wide-sweeping reforms. It distributed copies of the court of inquiry’s report to all fleet commanders for further dissemination. It also temporarily restricted the diving depths of its submarines and established in February 1964 the Submarine Safety Center in Groton. Among its many tasks the safety center developed a safety manual and lesson plans for teaching submariners and collected and shared information on submarine accidents and incidents.

Under SUBSAFE the Navy strengthened its training programs. It placed particular emphasis on flooding and casualty simulation, especially for new vessels joining the fleet. Another key element of the SUBSAFE program required that high-pressure blowing systems be modified to vent directly into main ballast tanks instead of through manifolds and that piping be widened to overcome the icing problem. The program also required installation of new centralized emergency valves that enabled one person to shut down internal piping circuits. And all seawater piping was redesigned to withstand the same pressures as the outside hull.

ALTHOUGH THE NAVY has never forgotten the Thresher , the vessel and the cause of her sinking quickly faded from the front pages. Navy tradition aided the process as the Thresher class of submarines was renamed the Permit class, after its successor the USS Permit . Frank DeStefano also cites the finality of the disaster as a factor in the nation’s forgetfulness: “It happened so quickly. There was nothing left. Memories of things like that fade. It’s human nature.” But the most important lessons had been learned, and in the almost thirty years since Scorpion , the Navy has not seen another major submarine sinking.

Dean J. Golembeski wrote “Struggling to Become an Inventor,” about Chester Carlson and xerography, in the Winter 1989 Invention & Technology.