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The Loss of the Thresher- New Analysis

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The Loss of the Thresher- New Analysis

Postby Tom Dougherty » Thu Jul 19, 2012 3:37 pm

The following is the text of a letter set to the Director of Naval Nuclear Propulsion by R. Bruce Rule on July 3 of this year. It is his analysis on the probable cause of the loss of the USS Thresher (SSN 593) in April, 1963:
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3 July 2012

From: R. B. Rule, 3931 Brookfield Ave, Louisville, KY, 40207-2001

To: ADM K. H. Donald, Director, Naval Nuclear Propulsion, 1333 Issac Hull Ave. SE, Washington, DC 20376

Subj: Why the USS THRESHER (SSN-593) Was Lost

In April 1963, the originator, 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 USS THRESHER (SSN-593). 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 originator, subsequently the lead acoustic analyst at the Office of Naval Intelligence for 42 years and the author of the book 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 USS THRESHER had been acoustically detected. That analysis identified a signal of extremely high 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 with determination of the non-vital bus line frequency 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) with supporting testimonies by BUSHIPS Code 345 and the David Taylor Naval Ships Research and Development Center personnel, respectively, a CAPT Leahy and Mr. Sam Savastin.

At 0913R, two minutes AFTER the reactor scrammed, THRESHER informed her escort ship, the USS 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 capability 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 (900 feet/7 mins), 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 signal frequency which indicated a depth between 2000 and 2400 feet. (See "Technical Comments" page 134 of the WI12TSR.) The originator 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 is not now - nor was there in 1963 - any evidence in the specific case of THRESHER to support the COI conclusion that the rupture of a silver-brazed, sea-connected pipe caused a reactor scram. THRESHER's 0913R transmission to SKYLARK - which make no mention of flooding - and 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. 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 USS THRESHER because of the failure of a silver-brazed fitting.

The bubble-pulse data indicates 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 speed 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 USS SCORPION (SSN-589), 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 are 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 bathymetricalty blocked - were destroyed by SOSUS Evaluation Center personnel when 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, the same day on which it was subsequently determined the USS 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 USS 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 by those onboard, and also for the benefit of those surviving Portsmouth Naval Shipyard personnel who continue to be falsely implicated in the loss of the USS 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.

Bruce Rule
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Comments from those who served?
Last edited by Tom Dougherty on Thu Jul 19, 2012 7:25 pm, edited 1 time in total.
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Re: The Loss of the Thresher- New Analysis

Postby JWLaRue » Thu Jul 19, 2012 5:48 pm

Would love to see John Craven's response to this (as well as to the Scorpion's loss).

This is a very cogent explanation of the event.

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Re: The Loss of the Thresher- New Analysis

Postby PaulC » Thu Jul 19, 2012 7:04 pm

Wow, fascinating, Tom! Thanks for posting that.
Warm regards,

Paul Crozier
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Re: The Loss of the Thresher- New Analysis

Postby Tom Dougherty » Thu Jul 19, 2012 7:23 pm

Would love to see John Craven's response to this (as well as to the Scorpion's loss).

Any particular reason why Scorpion is on your mind, Jeff?
(Heh, heh)
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Re: The Loss of the Thresher- New Analysis

Postby JWLaRue » Thu Jul 19, 2012 7:56 pm

...there might be a reason. :mrgreen:

I think a number of members will have her on their minds come September as well.

-Jeff
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Re: The Loss of the Thresher- New Analysis

Postby salmon » Thu Jul 19, 2012 10:49 pm

Hmmmm..this must be an encrypted message about a future release? In 1/72?
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Re: The Loss of the Thresher- New Analysis

Postby JWLaRue » Thu Jul 19, 2012 10:52 pm

Interesting guess, but alas...no.

You need to think what the two of us have in common and why September was mentioned. :?:

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Re: The Loss of the Thresher- New Analysis

Postby salmon » Thu Jul 19, 2012 10:56 pm

Same region and a regatta?
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Re: The Loss of the Thresher- New Analysis

Postby JWLaRue » Fri Jul 20, 2012 10:47 am

Nope.
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Re: The Loss of the Thresher- New Analysis

Postby salmon » Fri Jul 20, 2012 12:11 pm

O.K. So, the bottom line is, I do not know you guys well enough. And I can't guess worth a bean! LOL
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Re: The Loss of the Thresher- New Analysis

Postby Casey Thrower » Mon Aug 13, 2012 10:57 pm

Speculation will always be the only way any partial conclusion will be drawn to Thresher and the Scorpion. The difference between Thresher and Scorpion was that Thresher was not flooded and upon implosion, there wasn't much left. As Scorpion broke apart, she was already flooded before implosion, so much larger sections were found. Threshers SCRAM, if there was one, may have been brought on by several unknown reasons. Also, SUBSAFE was a result of Thresher due to her ballast lines freezing and stopping up the air lines to blow her tanks. Unlike airliners with black boxes and recovery of the plane parts, the exact cause of both subs reason for sinking will never be known. Because of their depth, possible nuclear contamination and condition the wreck sites, we will never be able to examine them closely enough. I do tire of reading the conspiracy nuts who say it had to be the Russians with either ramming the boats or torpedoes. Scorpion may have had a torpedo hatch open to the sea or flooding through the trash disposal unit. Thresher likely had a SCRAM and couldn't blow her tanks due to the frozen lines, sank past her crush depth and imploded. When you need to SCRAM and have no power, you want gravity on your side. Clearly this wasn't the case with Thresher.
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Re: The Loss of the Thresher- New Analysis

Postby Tom Dougherty » Tue Aug 14, 2012 3:06 pm

As Scorpion broke apart, she was already flooded before implosion, so much larger sections were found.


Casey,
Wrong, wrong, wrong!. Stop paying attention to the Craven BS stories! I hate Conspiracy Theories as well, and the only way to fight them is to present facts. In the case of Scorpion, there are indeed a lot of facts. Some of these are conveniently ignored in most instances to make favorite theories fit.

It was known in the 1960's that Scorpion was NOT flooded and imploded at about 1500 feet. Because of the initial differences of the Thresher and Scorpion wrecks, it was initially believed the situation observed at Scorpion was not due to implosion. At the Court of Inquiry, Peter Palermo who was Director of the Submarine Structures Section of the Naval Ship Engineering Center stated that from his analysis, implosion was “the primary cause of failure” and Scorpion had imploded once it reached crush depth. The failure mode, different from Thresher, was due to Scorpion’s stern cone cylinder junction at frame 67. Physicist Robert Price demonstrated that this point was the weakest in the hull, and pressure induced failure led to the driving forward of the stern engine room into the auxiliary machinery space, accompanied by a supersonic wall of water. This water hammer implosively shattered the operations compartment and blew the bow off at frame 46. The implosion, as well as other acoustic events, were caught on the hydrophone string at La Palma in the Canary Islands. The acoustic traces along with a great deal of other information will be published in the September 2012 SubCommittee Report.

Because of their depth, possible nuclear contamination and condition the wreck sites, we will never be able to examine them closely enough.

The wreck of Scorpion has been investigated close up on multiple occasions. I have a mid 1980's video tape of Alvin parked on the bottom resting on top of the Scorpion's sail, taken from a revised and improved version of Jason Jr. This small ROV was subsequently "flown" into the bow section of the Scorpion to investigate what was thought to be a potential hatch opening into the torpedo room (it wasn't). Very close inspection of both wrecks has been made, and the area monitored for radioactivity (from the nuclear torpedo and the S5W reactor. Nothing so far. The point is that a lot of evidence exists and in the case of Scorpion, it is very clear that a main battery explosion of one or more of the Gould TLX-53-A (due probably to an older method of securing ventilation during battery charge) occurred, almost certainly killing the crew due to the overpressure contained within the hull, and the Scorpion slowly drifted down over the next 22 minutes to 1500+ feet and then imploded. Much evidence will be presented (including the above mentioned acoustic traces from LaPalma and the condition of TLX-53-A fragments recovered by Trieste II) in the September SCR.

Did I mention you should read the upcoming September SCR? (Jeff paid me to put in that last line).
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Re: The Loss of the Thresher- New Analysis

Postby JWLaRue » Tue Aug 14, 2012 3:59 pm

Tom Dougherty wrote:Did I mention you should read the upcoming September SCR? (Jeff paid me to put in that last line).
Good to know I'm getting my money's worth! LOL!

But seriously, the article that Tom has written for the September about the loss of the Scorpion is a must read for all. It is the most cogent and complete analysis of this unfortunate event.

-Jeff
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Re: The Loss of the Thresher- New Analysis

Postby Casey Thrower » Wed Aug 15, 2012 10:08 am

Looking forward to it. I read anything I can get my hands on concerning the Scorpion and Thresher. By the way, I would have hoped that pictures of the Scorpion site would have been released by Woods Hole or at least the government by now. I wouldn't think that there is any classified pictures that were taken that could not be released. Lastly, it has always been believed that the Scorpion was at least flooded in the bow section which would account for her being bow heavy causing the stern to telescope into the machinery section of the boat due to loads. Then then boat partially imploded or the very least broke up. I still don't think we will ever know the true cause for Scorpion or Thresher. I believe that a black box type of equipment should be part of the boat, that would be jettisoned if it were to sink beyond a certain depth. At least then one could know the cause of the sinking.
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Re: The Loss of the Thresher- New Analysis

Postby Tom Dougherty » Wed Aug 15, 2012 10:45 am

Lastly, it has always been believed that the Scorpion was at least flooded in the bow section which would account for her being bow heavy causing the stern to telescope into the machinery section of the boat due to loads.


Believed by who?? That makes no hydrodynamic sense at all! How on earth could the bow being heavy cause the stern section to telescope forward into the AMR??? What loads are you talking about? The heaviest part of the submarine is the reactor plant, forward of the section that telescoped! If a submarine is in a steep dive, you don't have the stern section folding forward. Nor would the act of crashing into the bottom have caused reinforced HY-80 to telescope forward. Secondly, Scorpion hit the bottom at about 15-18 miles per hour and third, the evidence of the debris field; as the section with the telescoped aft section is some distance from the bow section on the bottom. The pieces clearly fell to the bottom AFTER the submarine broke apart. See this reconstruction of the wreck site: http://postimage.org/image/nx6jxi3rt/

In the September SCR, you will see an extensive article explaining the most plausible scenario based on: 1.) acoustics from the La Palma hydrophone array; 2.) the state of the wreckage on the bottom and 3.) fragments recovered from the bottom, most notably pieces of the TLX-53-A main battery. The recovered plastic piece of main storage battery was subjected to microscopic and spectrographic analyses. The Naval Research Laboratory concluded that it was violently but locally torn, and the deformation appears to have started on the inside of the cover, that is, on the battery side. Twenty fragments of the aluminum flash arresters from the battery were found embedded in the plastic at high velocity. This was indicative of injection of the material by an explosion. Analysis by the Portsmouth Naval Shipyard Team noted the large amount of battery debris visible in photographs taken by Trieste. This group speculated that the explosion occurred when the battery was dry, due to the velocity of the debris, and the battery may have exploded due to an accumulation of hydrogen gas.

By the way, I would have hoped that pictures of the Scorpion site would have been released by Woods Hole or at least the government by now.

http://www.history.navy.mil/photos/images/h97000/h97220k.jpg
http://www.history.navy.mil/photos/images/h97000/h97222k.jpg
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