Please report any broken links or trouble you might come across to the Webmaster.
Please take a moment to let us know so that we can correct any problems and make your visit as enjoyable and as informative as possible.

NavSource Online: Submarine Photo Archive

Patch on right contributed by John J. Cook, Decal in middle by , patch on left contributed by Mike Smolinski

Thresher (SSN-593)
Loss & Inquiry

Radio Call Sign: November - Alpha - Delta - Quebec

Awards, Citations and Campaign Ribbons

National Defense Service Medal

To Additional Pages

Keel Laying - Active Service

Thresher Class Attack Submarine: Laid down, 28 May 1958, at Portsmouth Naval Shipyard, Kettery, ME; Launched, 9 July 1960; Commissioned, USS Thresher (SSN-593), 3 August 1961; Final Disposition, sunk. 10 April 1963, as a result of a casualty during diving tests, in 1,400 fathoms of water, approximately 220 miles east of Boston, MA; Struck from the Naval Register, 10 April 1963.

Specifications: Displacement, Surfaced: 3,540 t., Submerged: 4,200 t.; Length 278' 6"; Beam 31' 8"; Speed, Surfaced 15 kts, Submerged 30 kts; Test Depth 1300'; Complement 143; Armament, four 21" torpedo tubes, UUM-44A SUBROC, UGM-84A/C Harpoon, MK57 deep water mines, MK60 CAPTOR mines, Sensors, BQQ-5 bow-mounted sonar, TB-16 Towed Sonar Array; Propulsion System, one S5W nuclear reactor, two steam turbines, single propeller, 15,000 shp.
Click On Image
For Full Size Image
SizeImage DescriptionContributed By
Memorial plaque610kThresher (SSN-593) Wreck Site Sketch drawn by the AP artist John A. Carlton on 11 April 1963. USN photo courtesy of Ron Reeves.
Thresher57k Navy ships circle in the vicinity of the site of Thresher's (SSN-593) sinking, 15 April 1963, five days after her loss. Ships are (left to right): Thomas Jefferson (SSBN-618); Sunbird (ASR-15); Warrington (DD-843), group flagship; and Redfin (SS-272). Photographed by PHCS Parker. Official U.S. Navy Photograph # NH 97555, from the collections of the Naval Historical Center.
Thresher68k "Debris on the ocean floor 8,400 feet below the surface may be a clue to the final resting place of the nuclear submarine Thresher (SSN-593). Taken last week by an underwater camera system operated by the oceanographic research vessel Atlantis II, these photographs show scattered bits of unidentified debris. The round objects are sea urchins which may range in size from four to twelve inches in diameter. The Navy states that the photographs in themselves are not conclusive evidence of the location of the missing submarine which sank on 10 April 1963, 220 miles east of Cape Cod. Ships of the searching force are continuing a minute search of the area with underwater cameras, sonar and other detection devices." Quoted from the original caption released with this photograph on 22 May 1963. Official U.S. Navy Photograph # NH 97556, from the collections of the Naval Historical Center.
Thresher99k "Three of fifteen packages of neoprene 'O' rings recovered by drag lines from the Lamont Laboratories oceanographic research ship Conrad in the area of prime interest in the search for the nuclear submarine Thresher (SSN-593). The recovery was made on the 28th of May, and the package was forwarded to the Court of Inquiry, Portsmouth, N.H., for examination. After examination and tracing of stock numbers it was definitely determined that one of the fifteen packages could have come only from the Thresher. The 'O' rings are shown on the packaging material after opening." The original view, from whose caption the quoted text is taken, was released on 1 June 1963. Official U.S. Navy Photograph # NH 97569, from the collections of the Naval Historical Center.
Thresher75k "Parts of a battery recovered by the Navy's bathyscaph Trieste during the first series of dives June 24th through 30th, 220 miles east of Cape Cod where the nuclear powered submarine Thresher (SSN-593) sank April 10. The centered object is an internal battery grid, encircled by re-enforcing members." The original view, from whose caption the quoted text is taken, was released on 5 September 1963. Official U.S. Navy Photograph # NH 97568, from the collections of the Naval Historical Center.
Thresher58k "This brass pipe, with the inscription: 'JO 10 ... 3-O-5091-05; DM 263-109-61; PL-1862791 PC.75; 1.050 Brass Pipe; 593 Boat', was recovered by the bathyscaph Trieste during the second series of dives in the search for Thresher (SSN-593). The nuclear powered submarine which sank April 10 some 220 miles east of Cape Cod had the hull number '593'." The original view, from whose caption the quoted text is taken, was released on 13 September 1963. Official U.S. Navy Photograph # NH 97570, from the collections of the Naval Historical Center.
Thresher121k "Mosaic of the sail. The conning station is at Arrow (1), upside down with the leading edge to the left in this photograph. The sail planes (2) are completely reversed. Below the sail is a torpedo shutter door (3). An air bottle is at (4) ... . Actuating gear for torpedo shutter door (5)." Quoted text is from the caption released with the original image, which was received by the Naval Photographic Center in December 1966. View shows the starboard side of the sail. Official U.S. Navy Photograph # NH 97560, from the collections of the Naval Historical Center.
Thresher136k "Starboard side of the Thresher (SSN-593) sail with portions of the hull number '593' visible." Photographed from a deep-sea vehicle deployed from Mizar (T-AGOR-11). The original photograph bears the date October 1964. Quoted text is from the caption released with that print. Official U.S. Navy Photograph # NH 97559, from the collections of the Naval Historical Center.
Thresher68k High pressure air flask and other debris on the ocean floor in the vicinity of the Thresher (SSN-593)." The original view, from whose caption the quoted text is taken, is undated. It shows an area of wreckage next to the top of the submarine's sail. Official U.S. Navy Photograph # NH 97561, from the collections of the Naval Historical Center.
Thresher96k Overhead view of Thresher's (SSN-593) upper rudder, photographed from a deep-sea vehicle deployed from Mizar (T-AGOR-11). The view shows draft markings on the rudder side and a navigation light at its top. The original photograph bears the date October 1964. Thresher was lost on 10 April 1963. Official U.S. Navy Photograph # NH 97557, from the collections of the Naval Historical Center.
Thresher132k "Draft markings on the topside rudder of Thresher (SSN-593). Part of the port stern plane of the sunken sub can be seen in the foreground. The bit of line on the right is connected to the underwater camera-magnetometer sled towed by Mizar (T-AGOR-11)." The original photograph bears the date October 1964. Quoted text is from the caption released with that print. Official U.S. Navy Photograph # NH 97558, from the collections of the Naval Historical Center.
Thresher78k "Sonar Dome -- A section of a sonar dome from the bow of a Thresher class submarine photographed August 24 during the second series of dives by the bathyscaph Trieste. The bathyscaph has completed 10 dives some 220 miles east of Cape Cod where the nuclear powered submarine Thresher (SSN-593) sank April 10." The original view, from whose caption the quoted text is taken, was released on 5 September 1963. Official U.S. Navy Photograph # NH 97562, from the collections of the Naval Historical Center.
Thresher106k "Sonar Dome -- An external portion of a sonar dome used exclusively in Thresher class submarines was photographed by the bathyscaph Trieste. August 24 during the second series of dives in the area where the nuclear powered submarine Thresher (SSN-593) sank April 10." The original view, from whose caption the quoted text is taken, was released on 5 September 1963. Official U.S. Navy Photograph # NH 97563, from the collections of the Naval Historical Center.
Thresher66k "A fragment of the anchor from the Thresher (SSN-593) located near the wreckage." The original view, from whose caption the quoted text is taken, is undated. Official U.S. Navy Photograph # NH 97564, from the collections of the Naval Historical Center.
Thresher82k "Insulation -- Rockwool thermal insulation photographed August 24 during the bathyscaph Trieste's second series of dives some 220 miles east of Cape Cod where Thresher (SSN-593) sank April 10. This type of insulation is used in all U.S. submarines." The original view, from whose caption the quoted text is taken, was released on 5 September 1963. Official U.S. Navy Photograph # NH 97565, from the collections of the Naval Historical Center.
Thresher57k "Photographs taken by Conrad, Lamont Laboratory's research ship, on 14 June 1963 in the Thresher (SSN-593) search area. An air bottle similar to that carried aboard Navy ships. The diagonal lines and the ball in the center of the picture is part of the lighting system for the underwater camera." The original view, from whose caption the quoted text is taken, was released on 19 June 1963. Official U.S. Navy Photograph # NH 97566, from the collections of the Naval Historical Center.
Thresher64k "An internal watertight submarine door photographed August 24 during the bathyscaph Trieste's second series of dives some 220 miles east of Cape Cod where the nuclear powered submarine Thresher (SSN-593) sank 10 April 1963." The original view, from whose caption the quoted text is taken, was released on 5 September 1963. Official U.S. Navy Photograph # NH 97567, from the collections of the Naval Historical Center.
Thresher1.30kDedication of the Thresher (SSN-593) plaque at St. Peters Chapel at Mare Island on 10 April 1964. The chapel was built in 1901 and still stand at the former shipyard. The plaque is still in place as well. Left to right: Capt. F. M. Smith (Production Officer), CDR C. H. Swift, Jr.. (CHC) and RADM E. J. Fahy (Shipyard Commander). USN photo # 62890-4-64, courtesy of Darryl L. Baker.
Thresher129kThresher (SSN-593) Memorial plaque.Courtesy of John J. Cook.
Thresher42k Thresher (SSN-593) Marker Buoy Label. USN photo courtesy of
Memorial plaque91kMemorial plaque at Independence Seaport Museum, Philadelphia PA, July 2006 for the crews of United States submarines lost during peace time accidents:
F-1 (SS-20), F-4 (SS-23), G-2 (SS-27), H-1 (SS-28), O-5 (SS-66), O-9 (SS-70), S-4 (SS-109), S-51 (SS-162), Squalus (SS-192), Scorpion (SSN-589) & Thresher (SSN-593).
Photo courtesy of Wendell Royce McLaughlin Jr.
Tolling The Boats 669k Active duty and veteran submariners stand together at the 29th annual "Tolling The Boats" Memorial Service held at the World War II National Submarine Memorial-West, Naval Weapons Station Seal Beach, Calif. May 29, 2006. The ceremony honored members of the Silent Service who gave their lives during World War II and the Cold War for their country and the cause of freedom. U.S. Navy photo # N-1159B-052 by Journalist 1st Class Brian Brannon, courtesy of
593 92k Thresher (SSN-593) to be honored with special postmark Photograph courtesy of via Ron Reeves.
593 542kVice Adm. Michael Connor, commander of Submarine Forces, delivers remarks during a memorial service for the 50th anniversary of the loss of the U.S. Navy submarine Thresher (SSN-593). The ceremony honored the 129 men lost on Thresher, which sank off the cost of Cape Cod on April 10, 1963 during sea trials. More than 700 Thresher family members and former crew members attended the service. U.S. Navy photo # 130406-N-TT535-002 by Jim Cleveland, courtesy of
Photo added 04/14/13.
593 207kNearly 1,000 relatives, former shipmates and coworkers of the 129 brave pioneers came together to commemorate the 50th anniversary of the loss of Thresher (SSN-593) at a ceremony held at Portsmouth High School 6 April. U.S. Navy photo # 130406-N-TN558-014 by Mass Communication Specialist 1st Class (SW/EXW) Jason J. Perry, courtesy of
Photo added 04/14/13.
593 517k A wreath floats 6 2013 April in the Piscataqua River off the Memorial Bridge to honor the 129 men lost on aboard the U.S. Navy submarine Thresher (SSN-593), which sank off the cost of Cape Cod on 10 April 1963 during sea trials. U.S. Navy photo # 130406-N-TT535-008 by Jim Cleveland, courtesy of
Photo added 04/14/13.

The Thresher sank during the deep dive portion of Phase C Sea Trials in April 1963. Quite a bit was known (and later discovered) about the Thresher disaster. Sadly, the same cannot be said of the sinking of the Scorpion (SSN-589). The Scorpion was lost during a mission in 1968 and while the U.S. Government convened inquiries, it has never issued any official explanation or cause of the loss, and instead has left the door open to several theories. This lack of closure is a void that has over the years been filled by poorly researched cloak-and-dagger accounts of the loss of the Scorpion.
The following is a copy of a letter written by Neal Collier to the Scorpion Families on the Scorpion-99 Yahoo Group. It was written in response to the most recent of these ‘un-official’ accounts. It is reprinted here because it contains some Thresher-related information, but more importantly to show that these two ships, the men that were lost, and the families and loved-ones left behind are inexorably linked in history – past, present, and future.

For the Scorpion 99, John Howland
I was 4 when my father was lost on the Thresher. He had transferred on as the Engineer’s relief just prior to Sea Trials. I don’t think he was even part of the crew for more than a few weeks.
I went in to the Navy myself – many different reasons – and ended up on the Archerfish (SSN-678), meeting the boat in the Med. After about a year we went to the Portsmouth Naval Shipyard (PNS) for an overhaul. The PNS was where the Thresher had undergone her last overhaul, and from which she went on her last dive. While there I took the opportunity to speak to a LOT of SY Workers and Navy types. I discovered that the PNS took the Thresher sinking very seriously and take the hard-earned lessons to heart in everything they do. The Shipyard lost officer observers and civilian Shipyard workers when the Thresher sank. Many people forget that. Each and every person that I spoke to who worked on her or remembered her was reduced to tears when we discussed the tragedy.
So what happened? Why did the Thresher sink? The sad fact is that usually the reason bad things happen is that humans are involved and humans, well, they make a lot of mistakes. For the Thresher, there were so many mistakes made it is difficult to name them all. One that comes to mind is the depth of water in which she sank. Test Depth is a certain depth. It’s classified, but for argument's sake let’s say Test Depth is 400 feet. (It is deeper than that, but we’ll use that in this example.) If you were conducting deep depth test and the boat could only go safely to 400 feet, you probably would want to be in water that was just a bit deeper than that. You would also want to have the ability to provide support if trouble occurred. The Thresher was on the way to Test Depth in water that was about 8400 feet deep and no rescue vessels were in the vicinity. Think about the monumental arrogance and stupidity that resulted in that location being chosen. There were others, but the gist here is that many, many mistakes were made. From that tragedy, though, came many positive changes. SUBSAFE was the big one. Design and operational changes occurred, too.
- SUBASFE - A complex and comprehensive submarine overhaul maintenance and repair management system with checks and double-checks to ensure any / all critical operational and safety components are thoroughly tracked, tested, and checked after maintenance, repair, or modification prior to allowing them to be released for use.
- Moisture separators on the High Pressure Air Compressors (HIPACS) to remove moisture known to cause the 'Venturi Effect' which freezes the Tank Emergency Main Ballast Tank Blow Valves when they are needed the most.
- Prior to the Thresher disaster, submarines were routinely put through a gauntlet of depth charges causing structural damage that was then measured and evaluated. This is no longer done to operational vessels.
- Fast SCRAM recovery. The ability to rapidly and safely bring the reactor (the steam source for the engines to turn the propeller) back from a shutdown state.
- Equipment Cooling. Prior to the Thresher, equipment was cooled mainly from pipes that carried seawater through tubes that cooled the equipment. This meant that there were many feet of pipe throughout the sub carrying water at extreme pressures. Design changes were made to install large heat exchangers that transferred cold from the seawater to fresh water at much lower pressures. The fresh water was then pumped to the equipment to cool it.
- Silver brazing and radiography. When pipe was cut and welded, a special silver braze was used to seal the weld and make it water tight. Silver welding was hard to get right and many welds were not able to withstand the pressures to which they were subjected. This practice was ultimately stopped. In addition, very few welds were looked at using radiography (think of the dentist looking at your teeth). Taking radio-graphic pictures of critical welds is now done (and in some cases re-done) for all piping and hull welds.
The above are a few major examples. I hasten to add that the Thresher did not 'create' these changes; they (and many more) were already being studied, debated, and discussed at the time. The Thresher was only the catalyst to make them happen; to push it through Congress.
I do not know a lot about the Scorpion but have read a few books and accounts. From a Scorpion perspective, I think the article from Proceedings (July 1998) summed it up as the Navy just did not learn the lessons from the Thresher. A stuck Trash Disposal Unit (TDU) valve was postulated as the most probable reason the Scorpion was lost. A guy I knew on the Shark (SSN-591) (sister ship to the Scorpion) said that TDU valve got stuck on a mission and the Captain would not let anyone touch it until they got into port. They must have been teaching that as a potential problem at Prospective Commanding Officer's (PCO) School.
People just like the sexy conspiracy stuff, I guess. Revenge for the sinking of the .... Wait a minute. What, now? Our culture loves a good story and we want so desperately to believe the unbelievable. When in Orlando at a Navy service school I heard of the “Thresher Tape” where supposedly members of the crew left messages to loved ones that the Skylark (a recording and communications ship) picked up before she sank. I heard this from many different people at different commands. I searched at several different commands in a vain attempt to find that recording. It took me until years after I got out of the Navy to come to the realization that it was baloney. A family friend (USNA ’56) explained it to me this way “OK, the ship is sinking. Are you going to work like heck to fix it, or are you going to line up outside the Radio Room to record a message?”.
I was at a Naval awards ceremony a few years back and a female officer (LtCDR) informed me at the reception that her husband told her of a top secret mission where the Thresher actually had SEALS on board during Phase C Sea Trials. I have to tell you, had I said to her what I was actually thinking at the time, I probably would have been thrown off that base.
There are other examples (too many, unfortunately). People who you would think know better don’t. There are all these crazy theories and stories. Thankfully, there are no books written about the Thresher (except maybe the Polmar book), so I don't have to go through that. I was recently lent a book about the 'secret' submarine war by a co-worker who is also ex-Navy. After a quick scan I was not happy with what I read and did a web search on the book. The results (poorly researched, mostly fiction, etc.) confirmed my suspicions. I spoke to the guy who lent it to me, explaining how I would feel if idiots who actually believe the tripe sent out via emails wrote a book about some plot against the Soviets involving the Thresher; involving these noble men who gave their lives for their country; cheapening their memory and honor for a few bucks, for some fame, for --- what exactly? When I told my co-worker this he leaned back in his chair and said very humbly, “I hadn’t thought of that.” The crazy theories and stories make me sick and angry, to be honest. They create a false and phantom history and – in my view – move the discussion farther away from where it needs to be: how can we create a stronger and safer submarine force and never NEVER let this kind of tragedy happen again?
OK. I have said enough. As a closer I would say that we need to be vigilant, to keep the memories alive, and to stay true to our loved ones and their memory through memorial services and discussions. We need to keep the memory of those lost – and how they were lost – alive for this and future generations.
1 - "Those who don't know history are destined to repeat it." Edmund Burke (1729-1797)
2 - We honor those who we love and respect. When we stop doing that we lose our humanity.
3 - Memorial services give those who have not grieved the opportunity to do so when they are ready.
Sincerely, Neal Collier

In Memorium:

In the Second Book of Shmuel (Samuel), 22nd chapter, 5th through the 20th verses, translated from the original in Hebrew and published by the Koren Publishers of Jerusalem, Israel, 1982, can perhaps aptly describe the fate of the crew and all other U.S. submariners who died defending their county:

"When the waves of death compassed me / the floods of ungodly men made me afraid; / the bonds of She'ol encircled me; / the snares of death took me by surprise; / in my distress I called upon the Lord, / and cried to my G-D: / and he heard my voice out of his temple, / and my cry entered into his ears. / Then the earth shook and trembled; /the foundations of heaven moved / and shook because of his anger /...the heavy mass of waters, and thick clouds of the skies /... And the channels of the sea appeared, / the foundations of the world were laid bare, / at the rebuking of the Lord, at the blast at the breath of his nostrils. / He sent from above, he took me; / he drew me out of many waters; / he delivered me from my strong enemy, and from those who hated me; for they were too strong for me. / They surprised me in the day of my calamity: / but the Lord was my stay / He brought me forth also into a large place: / he delivered me because he delighted in me./"
Photo courtesy of Tom Kermen. Dante's Prayer courtesy of Loreena McKennitt via
Thresher306kFour page Memorial PDF pamphlet of the Thresher (SSN-593).

Thresher (SSN-593) Loss: 50 Year Anniversary
On 10 April 2013 it will be the 50th Anniversary of the loss of the Thresher.
This posting is being made at the request of Bruce Rule, the author of this analysis.
It is now possible with recently declassified documentation and other supporting data, all in the public domain, to provide this scientific analysis.
A version of this posting has been sent in letter form to ADM K. H. Donald, Director Naval Nuclear Propulsion and Captain L. Bryant Fuller III, Shipyard Commander Portsmouth Naval Shipyard.

Subject: Why the Thresher (SSN-593) Was Lost?
In April 1963, the author, then the Analysis Officer at the Sound Surveillance System (SOSUS) Evaluation Center in Norfolk, VA, had just completed the U.S. Nuclear Submarine Acoustic Data Handbook, a comprehensive summary of the low frequency, narrowband acoustic signature characteristics of all U.S. nuclear submarines then operational, including the Thresher. That document was based on analysis of more than 700 acoustic detection events of all nuclear submarines.
Acting in that capacity, and with those technical qualifications, the author, subsequently the lead acoustic analyst at the Office of Naval Intelligence for 42 years and author of WHY THE USS SCORPION (SSN-589) WAS LOST, reviewed on page 151 of the WINTER 2012 issue of THE SUBMARINE REVIEW (WI12TSR), called in acoustic data from all Atlantic SOSUS stations to determine if the loss of the Thresher had been acoustically detected. That analysis identified a signal of extreme amplitude produced by the collapse of the Thresher pressure hull at 09:18:24R on 10 April 1963. The derived position - a four nautical mile (nm) by eight nm ellipse with a major axis oriented 040-220 - provided the basis for the successful search for the Thresher wreckage.
That analysis also determined the Thresher non-vital electrical bus, after two minutes of line-frequency instability, failed for unknown reasons at 0911R while the nuclear reactor coolant pumps (RCPs) were in FAST. (Note: the SSTGs were not acoustically detected; the instability of the non-vital bus was derived from measured instability in the RCP rotational-rates. The non-vital bus line frequency was determined by correcting for the 2.5 percent slip of the RCP drive motors. Also note that the signal strength of the RCP sources at 0911R, at a detection range of about 30 nm, indicated that had the RCPs been shifted to SLOW at 0911R, they should still have been acoustically detected - but no such detection occurred.) The electrical load thrown on the vital bus at 0911R by the failure of the non-vital bus with the RCPs in FAST exceeded the capabilities of the vital bus; the RCPs (initially detected at 0845R in FAST as Thresher, according to the deep-dive OP-PLAN, was approaching a depth of 1000 feet) went off-line and the reactor scrammed at 0911R. The coincident detection of an acoustic signature component at a fixed ratio relative to the RCP source unique to S5W RCPs confirmed the SOSUS detection was Thresher. There were no acoustic detections by SOSUS of any Thresher main propulsion sources as would have been probable had speeds above about 14 knots been employed. The author provided the above assessments of RCP operating mode and loss of signal in testimony before the Thresher Court of Inquiry (COI) on 18 April 1963 with supporting testimonies by BUSHIPS Code 345 and the David Taylor Naval Ships Research and Development Center personnel, respectively, CAPT Patrick Leahy and Mr. Edwin Savasten.
At 0913R, two minutes AFTER - repeat, AFTER - the reactor scrammed, Thresher informed her escort ship, the Skylark (ASR-20) by underwater telephone, that she was (quote) experiencing MINOR difficulty.(end quote) The COI concluded the rupture of a silver-brazed, sea-connected pipe had produced flooding in the engine room that shorted-out electrical systems causing the scram, an assessment still accepted at the highest levels within the Navy; however, that assessment requires that flooding at test-depth that resulted in a reactor scram and a loss of propulsion be described by Thresher as a (quote) minor difficulty. (end quote)
At 0917R, Skylark received a final communication from Thresher that contained the number 900. That number is assessed to have been the depth in feet (referenced to test-depth as required by the deep-drive OP-PLAN security directive) by which Thresher had exceeded her test-depth of 1300 feet, or 2200 feet. With an estimated average sink-rate of about 130 feet per minute, the Thresher pressure-hull collapsed at 09:18:24R at a depth of about 2400 feet, more than 400 feet below her estimated collapse depth. Independent confirmation of that assessment has been provided by a post COI testimony analysis of the collapse event acoustic bubble-pulse frequency which indicated a depth between 2000 and 2400 feet. (See "Technical Comment" page 134 of the WI12TSR.) The author has no information on the change in displacement produced by hull compression at great depth and the extent to which that decrease could have accelerated the Thresher sink-rate.
There was not in 1963 - nor is there now - any evidence in the specific case of the loss of Thresher to support the COI conclusion that on 10 April there was a rupture of a silver-brazed, sea-connected pipe that caused a reactor scram. The occurrence of silver-brazing problems earlier with Thresher, and with other submarine hulls, is NOT conclusive evidence that it occurred during the 10 April deep-dive, especially since Thresher's 0913R transmission to Skylark makes no mention of flooding and because the results of analysis of the SOSUS acoustic data are consistent with failure of the non-vital electrical bus which resulted in a reactor scram at test-depth because the RCPs were operating in FAST. Unable to deballast because of a subsequently confirmed ice-formation condition in the high-pressure air lines, Thresher sank to collapse at extreme depth without any prior flooding. Both the pressure hull and all sea-connected systems survived well beyond design specifications. As discussed in The Death of the Thresher by Norman Polmar, Thresher had made some 40 dives to test depth prior to April 1963.
To repeat, there was not - as maintained on page 122 of the WI12TSR - any (quote) failure of a silver-brazed fitting in the engine room, with immediate flooding, and subsequent emergency shutdown of the nuclear reactor (scram due to spray on the engine room affecting electrical control panels) (end quote); hence, it is wrongly asserted, also on page 122, that Portsmouth Naval Shipyard personnel were responsible for the loss of the Thresher because of the failure of a silver-brazed fitting.
The acoustic bubble-pulse data indicate the Thresher pressure hull and all internal compartments were completely destroyed in less than one-tenth of a second (100 milliseconds), significantly less than the minimum time required for human perception of any event: 50 milliseconds for retina integration plus 100 milliseconds for cognitive integration. Measurements made during the lowering and recovery of an instrumented diesel submarine to collapse depth are consistent with the conclusion that the water-ram produced by the initial breaching of the Thresher pressure hull at 2400 feet traversed the diameter of the pressure hull in about 0.005 seconds (five milliseconds), a velocity of about 4000 mph. That force would have torn the pressure hull longitudinally and vertically as verified by imagery of the Thresher wreckage. Even allowing for differences in pressure hull design, the extent of the damage to Thresher, compared to the Scorpion, which collapsed at 1530 feet, indicates Thresher collapsed at significantly greater depth.
The above discussed information on the failure of the non-vital bus, the RCP operating mode and implications for a reactor scram is provided in COI documents available in the public domain.
As of March 2007, the Office of Naval Intelligence still held a photo-copy of the SOSUS paper display (LOFARgram) upon which the above assessments are based. There were no SOSUS recordings of the Thresher event. The original SOSUS LOFARgram data from all Atlantic stations - except Barbados, which was bathymetrically blocked - were destroyed by SOSUS Evaluation Center personnel because the data was more than five years old and because it was concluded another submarine would not be lost. The date of destruction of the original Thresher acoustic data was 22 May 1968, coincidently the same day on which it was subsequently determined the Scorpion was lost.
With the approach of the 50th anniversary in 2013 of the loss of Thresher, it would be appropriate for the Navy to officially acknowledge why the Thresher was lost for the benefit of surviving family members and friends of those onboard who may find some solace in the knowledge that the collapse event occurred too fast to be apprehended, and also for the benefit of those surviving Portsmouth Naval Shipyard personnel who continue to be falsely implicated in the loss of the Thresher by assertions that a silver-brazed fitting failed.
As previously stated, the Thresher pressure hull and all sea-connected systems significantly exceeded design specifications; there was no flooding before collapse of the pressure hull at extreme depth.
Although this analysis advances an understanding of why the Thresher was lost by establishing there is no evidence of the failure a silver-brazed fitting during the 10 April deep-dive, the analysis still leaves the perhaps unanswerable question of why the non-vital bus failed after two minutes of line frequency instability.
The Thresher was lost nearly half a century ago because her nuclear reactor shut down at test depth of 1300 feet and the crew could neither blow ballast nor restart the reactor in the seven minutes during which Thresher sank to collapse at a depth of about 2400 feet.

Dave Johnston also added: Thresher's inability to blow the ballast tanks had nothing to do with the reactor shutdown. It was a separate problem that unfortunately reared it's head at the wrong time. The blow system had plenty of capacity and it can be manually operated. That was not the problem. When the high pressure air that was used to blow the tanks left the storage banks, it passes through the control valves that keep it in the banks under pressure. Anytime a compressed gas expands, it cools rapidly. As the very cold air passed through the valves, frost began to form due to the presence of moisture in the air. It very quickly built up (a matter of a few seconds) and froze solid in the valves. The solid ice stopped the air just as effectively as shutting the valves, thus the Thresher was unable to blow her tanks.
This problem was discovered in one of the Thresher's sister boats when a test was conducted alongside the pier. Everyone involved was shocked at what happened. This discovery resulted in an immediate redesign of the whole ballast tank blow system. The valves were redesigned and moisture traps were installed in the air lines. The new design was completely effective and it eliminated the problem. Unfortunately, it was far too late for the Thresher's crew.
Text courtesy of Ron Reeves, Bill Gonyo, & Dave Johnston.
US Navy photo courtesy of Scott Koen &
593 942kTwo page PDF on events leading to Thresher's (SSN-593) sinking and the creation of SUBSAFE. Photograph courtesy of Ron Reeves.

View the Thresher (SSN-593)
DANFS history entry located on the Haze Gray & Underway Web Site.
Crew Contact And Reunion Information
U.S. Navy Memorial Foundation
Fleet Reserve Association

Additional Resources and Web Sites of Interest
On Eternal Patrol
Talk:USS Thresher (SSN-593) by Al Bonnyman
SSN-594 Permit Class - FAS web site
Looking back on the USS Thresher
USS Thresher Memorial Ceremony
50th Annual USS Thresher Memorial Service
USS Thresher, Going Quietly

Back To The Main Photo IndexBack To the Submarine Index
Problems and site related matters, E-mail Webmaster
This page is created by Gary Priolo and maintained by Michael Mohl
©1996 - 2014, NavSource History All rights reserved.