The USS Thresher (SSN-593) was lost at sea on 10 April 1963 during its first deep dive test (DDT) after a nine-month post-shakedown availability (PSA) at Portsmouth Naval Shipyard (PNSY). It was the first and remains the world’s worst nuclear submarine disaster, killing all 129 people on board. The July 2018 Proceedings article “Declassify the Thresher Data” described contributing factors to the loss and rejected the Naval Court of Inquiry (NCOI) Report’s opinion there was major flooding before implosion.1
The Thresher sank at a time when the United States was rapidly advancing technologically and during a period of geopolitical and military competition with the Soviet Union. What was the mindset that allowed the then-most advanced nuclear submarine in the world to be lost on what was supposed to be a routine and carefully planned dive to test depth (TD)? Being able to study all the factors contributing to Thresher’s loss could help prevent a similar disaster.
Because the Navy has aggressively protected information about the loss of the Thresher from the public, we hired an attorney, Robert Eatinger, and submitted a Freedom of Information Act (FOIA) request in April 2019. In response to that FOIA request, the Navy did not produce any records, so we filed a lawsuit in July 2019. In February 2020, a Federal judge ordered the Navy to start providing documents in May of this year.
Key Information Withheld
Only 19 of more than 1,700 pages of testimony about the Thresher disaster have been made public so far (including some testimony that was originally offered in open court with reporters present) – and no endorsements or exhibits of the Naval Court of Inquiry (NCOI) Report have been provided. Earlier FOIA requests for Thresher information, such as one filed in 2017 seeking the unclassified Sea Trial Agenda, produced no results. Another unfulfilled request was recently made on behalf of Bruce Harvey, the son of Lieutenant Commander Wes Harvey, Thresher’s commanding officer (CO), seeking his mother’s letter.
Outdated Information Must be Released
The Navy located 3,600 pages of information responsive to the FOIA request of April 2019. Executive Order 13526 requires declassification after 50 years; protected information, like Naval Nuclear Propulsion Information (NNPI), is not covered by the order. The loss of THRESHER, a significant historical event, requires the release of some NNPI that, after 57 years, is most likely antiquated and obsolete. Its release should pose no risk to the national security.
Making the Thresher information available to the public could answer a number of questions. We consider these ten to be the most important:
1. Why was the Main Ballast Tank (MBT) Blow System Poorly Designed?
The MBT Blow System was inadequate to surface the submarine from deep depth while flooding. Air bank capacity and blow rate were very limited by design, making nuclear propulsion the only way to bring the submarine to the surface. 2
2. Why did the NCOI Report Inaccurately Describe the Pier-side MBT Blow System Test?
The NCOI reported that two MBT blows failed to surface Thresher. The NCOI ordered a pier-side MBT blow test on Thresher’s sister ship, TINOSA, which was preparing for sea trials at PNSY.
Then-Lieutenant Zack Pate (later Captain) personally supervised this test. Pate’s description of that test in the June 2018 edition of The Submarine Review is markedly different than what the NCOI reported in Finding of Fact 50, “under a test required by the court the conical strainers in the reducers were blocked and ruptured by the formation of ice in about 30 seconds.” Pate says the air flow stopped and started every few seconds for 6 minutes, at which point the test was stopped and delivered one-tenth of the designed deballasting.3
After this MBT blow test failed, an inspection unexpectedly found conical strainers and orifice plates in the inlets to both high-pressure air-reducing valves. The PNSY design engineers who planned and witnessed the test and ship’s personnel were unaware of the presence of these orifice plates or strainers. The orifice plates, designed to reduce air flow rate to prevent the strainers from collapsing, crippled the inadequately designed MBT Blow System. An MBT blow test early in new construction would have discovered this fatal flaw.4
3. Was Critical Work Done by Plan?
NCOI Report Recommendation 14.a and Opinion 8.c imply the conical strainers were installed by plan. If the strainers were installed by plan, why weren’t the PNSY design engineers or ship’s personnel aware of this configuration?
4. Why Were the Strainers and Orifice Plates Not Removed?
The Marotta Company (now Marotta Controls) made the high-pressure air-reducing valves, conical strainers, and orifice plates, and PNSY installed them to prevent damage to the reducers by particles of industrial debris.5 Whether or not installed by plan, the strainers and orifice plates were temporary and should have been removed before sea trials.
5. Were Reactor Plant Operating Procedures a Factor?
NCOI Report Opinion 1.c acknowledges there were inadequate operating procedures for flooding and loss of reactor power. Access to the 1963 reactor plant operating procedures could explain events during the casualty.
Admiral Hyman Rickover and his Naval Reactors (NR) staff knew the negative publicity of a reactor accident on a nuclear submarine could seriously damage and possibly terminate the Naval Nuclear Propulsion Program, which was crucial to National Security.6 Rickover denied reactor safety (i.e., preventing a reactor-related accident) was more important than the safety of the ship and crew. While Rickover stated reactor plant procedures could be overridden to save the boat, others disagree.7
At the time of Thresher’s loss, Rickover required steam flow to be shut off to the propulsion turbines after an emergency reactor shutdown (scram). There was a procedure—not approved by Rickover until after Thresher’s loss—that allowed the use of steam produced by residual and decay heat in the reactor core after a reactor scram for emergency propulsion to drive the submarine to the surface. The Submarine Review article describing this procedure is highly credible because the authors of the article, in addition to Captain Pate, are a retired submarine group commander and a former Atlantic Submarine Force Commander.8
Captain James Collins, who served in the USS George Washington (SSBN-598) before Thresher’s loss, says the CO’s standing orders for a reactor scram prevented securing steam flow and to answer the ordered bell under certain conditions, such as being deep. Rickover allowed this violation of his procedures.9
Rickover, Navy engineers, and senior submarine officers knew Thresher’s air bank capacity and MBT system blow rate were inadequate to surface the ship when flooding near test depth (TD). This left nuclear propulsion as the sole means of emergency recovery.10 Two authors report Thresher’s test depth was 1,300 feet, if true that is nearly twice that of previous submarines’ TD of 700 feet. Why were the procedures to provide emergency propulsion not approved until after Thresher’s loss? Declassified testimony may provide insight, especially Rickover’s testimony.
6. Why the Debate Over Main Coolant Pump Speed?
In April 1963, Lieutenant Bruce Rule, U.S. Navy Reserve, was the analysis officer for the Navy’s Sound Surveillance System (SOSUS) Evaluation Office at Norfolk, Virginia. He testified at the NCOI in closed session as the submarine acoustic expert and later spent 42 years in the Office of Naval Intelligence as the lead acoustic expert. Rule says he testified that analysis of low frequency analyzing and recording data (LOFARGRAMs) from a SOSUS hydrophone array 30 nautical miles from where Thresher sank recorded main coolant pumps (MCPs) running in fast speed during the final dive, then stopped, and never restarted.12
NCOI Report Opinion 45 states:
“It is known, without much doubt, that at 0911R the Main Coolant Pumps of THRESHER, which had been running since the start of the dive, either stopped or were slowed. If the Main Coolant Pumps stopped, there would have been an automatic reactor shutdown (scram).”
Does the uncertainty as to whether the MCPs stopped or slowed arise because the NCOI did not trust or understand SOSUS technology or Rule’s testimony—or because the writing of the report was influenced to cast doubt that the reactor scrammed and doomed the ship?
An official historian of Admiral Rickover and NR writes that Rickover and his staff reviewed the MCP acoustic evidence and found it “very unsubstantial.” NR called in experts who supported Rule’s sworn NCOI testimony and confronted them. These experts changed their sworn testimony, agreed with NR, and signed documents attesting to this.13 Rule claims these experts were pressured to sign documents NR had drafted that recanted their testimony.14 One expert told Rule that when they were at NR Rickover said, "This may have been a training issue but I'm the only one who can say that and I'm not going to. The lawsuit asks for Thresher’s LOFARGRAMs and Rickover’s discussion of them.
Rule claims two commanders aggressively challenged him during his testimony before the NCOI to get him to say MCPs were in slow speed, not fast, during the DDT because running slow-speed MCPs was more reliable for maintaining propulsion, as propulsion was key to getting back to the surface.15
Ron Estes served 14 months as a reactor operator in Thresher and recalls the previous CO’s policy was to run MCPs in fast speed when going to test depth, allowing immediate use of flank speed to drive the submarine to the surface during an emergency.16 The previous CO’s testimony could resolve this.
7. Was the Sea Trials Agenda a Factor?
The PNSY Sea Trial Agenda scheduled a two-hour DDT in the morning, which would use the sea pressure of TD to test the hull, its fittings, and electrical cabling (e.g., sonar, radio antennas, running lights, etc.) outside the pressure hull while stopping at 400 feet, one-half TD, TD minus 300 feet, and TD to check for leaks.
A second DDT that afternoon would take six hours and would test equipment at intermediate depths, including seawater valves that were to be cycled at one-half TD and TD.17
The NCOI Report says damage from the Thresher’s shock trials in June was still being discovered late into the PSA and was severe enough to limit depth to 200 feet until after the PSA. Two hours was too short for a DDT after a PSA, especially if it was not known whether all the shock trial damage had been repaired. Could a single longer, more controlled DDT have prevented the loss?
8. Was Rickover’s DDT Procedure Rejected?
Rickover faced a similar problem when he was planning to ride Thresher during builder’s sea trials two years before. He testified that little thought was put into the planning of the DDT and that there was a lack of concern about going to a much deeper TD than previous submarines, especially considering Thresher’s inadequate MBT blow rate and air bank capacity at depth. He directed the rewriting of the DDT procedure to go deep slowly, stopping at incremental depths to test equipment and cycle critical valves.18
Vice Admiral Ron Thunman said during a recent interview that in 1968, before he took command of USS Plunger (SSN-595), Rickover said, “Don't be dumb and a cowboy by going directly to test depth during a test dive like Thresher did instead of at 100-foot increments.” Why no intervention by Rickover or his staff?
9. Was Inadequate Training a Factor?
Captain Joseph Yurso, U.S. Navy (Retired) was the PNSY Duty Officer the day Thresher was lost. His October 2017 Proceedings article says Thresher’s Ship Superintendent told him there was not enough time for training.19 Congressional testimony states crew training was added to the schedules of submarines in shipyards, implying a concern.20 The NCOI Report was concerned with the CO and Executive Officer being transferred in January 1963, but says Thresher was “well manned by experienced officers and men.” There is no public statement about a lack of crew training. The NCOI Report testimony and exhibits should show the manning levels, qualifications, and experience of the officers and crew.
10. Was the Boat Improperly Ballasted?
Was the permanent lead ballast adjusted prior to PSA sea trials? If not properly ballasted, Thresher could have been out of trim because of the addition of PUFFS passive ranging sonar hydrophones on the ends of the horizontal stabilizers during PSA (likely making the submarine heavy aft). If PSA weight and displacement configuration changes were not corrected with a permanent ballast adjustment, it could have been a factor in the ship’s loss.
It has been 57 years since the loss of the Thresher. Any information that was classified at the time of the ship’s loss should now pose no threat to national security. The Navy owes the public and itself a complete, transparent review of all the documentation surrounding this terrible disaster at sea. Information from the Thresher could still provide valuable lessons to current and future submariners and could also help the Navy avoid mistakes as it competes to maintain an edge over its current great power competitors.
1. Captain James B. Bryant, U.S. Navy (Retired), “Declassify the THRESHER Data,” Proceedings July 2018 edition, pp. 62–66. Hereafter cited as Bryant.
2. Phillip Martin Callaghan, Effects of the USS THRESHER Disaster upon Submarine Safety and Deep-Submergence Capabilities in the United States Navy (Blacksburg, VA: Virginia Polytechnic Institute and State University, 1987), Master of Arts thesis, pp.24-26 Hereafter cited as Callaghan. Stanford University Libraries, Loss of the U.S.S. “THRESHER”: Hearings before the Joint Committee on Atomic Energy, Congress of the United States, Eighty-Eighth Congress, first and second sessions on the loss of the U.S.S. THRESHER: June 26–27, July 23, 1963, and July 1, 1964. PDF FILE, pp. 85, 86. Hereafter cited as Stanford.
3.The Submarine Review June 2018 edition, “The Tragic Loss of the Nuclear Submarine THRESHER 10 April 1963,” by Captain Zack T. Pate, USN (Ret.), RADM David Goebel, USN (Ret.), and VADM George Emery, USN (Ret.), pp. 130–134. Hereafter cited as Review. Francis Duncan, Rickover and the Nuclear Navy: The Discipline of Technology (Annapolis, MD: Naval Institute Press, 1990). PDF, p. 88. Hereafter cited as Duncan.
4. Submarine Review pp. 133, 134.
5. Ibid., pp. 133, 134.
6. Richard G. Hewlett and Francis Duncan, The Nuclear Navy 1946–1962, pp. 342–345. Norman Polmar & Thomas B. Allen, Rickover Controversy and Genius: A Biography (Simon & Schuster, Inc., 1982) pp. 622–627.
7. Duncan, pp. 86–87 and 89–92.
8. Submarine Review, pp. 134-135. A source says this article was approved by the Navy; the publisher denies it. An article submitted last year to this magazine by one of the authors, Bryant, was sent to the Navy by the publisher for review and embargoed. This fact and the seniority of the authors suggests that the June 2018 article was reviewed by the Navy.
9. Bryant.
10. Callaghan, pp. 24–26. Stanford pp. 85, 86.
11. Norman Friedman, U.S. Submarines Since 1945: An Illustrated Design History (Naval Institute Press, Annapolis, MD, 1994, revised 2018), pp. 133, 269, 259, 271. Norman Polmar, The Death of the USS THRESHER (SSN 593): The Story Behind History’s Deadliest Submarine Disaster (The Lyons Press, Guilford, CT, 1964, revised 2001), p. 38.
12. Bruce Rule, Why the USS THRESHER (SSN 593) Was Lost, A Technical Assessment Based on Analyses of Acoustic Detections of the Event (Ann Arbor, MI: Nimble Books LLC, 2018), IV, 11.
13. Duncan, p. 90.
14. Bryant.
15. Ibid.
16. Ibid.
17. Department of the Navy, Office of the Judge Advocate General’s Corps, “The Loss at Sea of U.S.S. THRESHER,” June 20, 1963. Findings of Fact of the Court of Inquiry, pp. 139 and 141, Testimony pp. 39–41. Duncan, p. 77.
18. Stanford, pp. 85, 86.
19. Joseph F. Yurso, “Unraveling the THRESHER’s Story,” Proceedings, U.S. Naval Institute, October 2017 edition), p. 42.
20. Stanford, p. 94.