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Retired Submarine Commander Sues Navy to Release USS Thresher Investigation

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  • #16
    The meaning of "900 North"

    '900 North' was Thresher's last UQC(underwater telephone) transmission to her escort ship USS Skylark.

    At 075 Thresher advised Skylark that her depth was 400ft.

    At 0754 Thresher advised Skylark that(for security reasons) all future references to depth would be given relative to test depth. The number 900 was thus an indirect reference by Thresher to her depth at 0917: 900ft below her test depth of 1300ft or 2200ft. The word 'north' is assessed to have been a direction. In this case 'up' as north is on a map, i.e. test depth was above Thresher by 900ft at 0917.

    This explanation was dismissed in the court of inquiry, because it required the Thresher's hull pressure to have survived greater than the crush depth of 1950ft. Furthermore, it would have invalidated their conclusion that flooding had occurred at test depth(1300 feet).

    The idea of flooding didn't add up then, nor is it even credible now. Thresher made no mention of flooding during her decent, nor did Skylark hear it. A test demonstration at dry dock No 2 at Portsmouth naval shipyard was held for the court of inquiry. A stream of water was released to atmosphere at Thresher's test depth pressure(580 psi) against a piece of electronic equipment. One witness Russell Preble, CDR USN (ret) observed that test, and said the noise was overwhelming, nothing could be heard over the noise. No orders could be heard over the roar of the water striking anything in it's way. This would have been heard by the men on Skylark, and observed on the underwater hydrophones that picked up the entire event.
    And given the size of the pipes that the court of inquiry claimed to have leaked, they don't seem to have calculated the amount of water that would have entered the sub in those six minutes(from 1300ft(at 0911) to the 900 north(0917) quote). Why the court of inquiry blame silver blazing when no reports of flooding was recorded, or reported, and Thresher survived without breach to almost twice test depth... it seems the court of inquiry was deflecting blame. It appears relying on the nuclear power plant alone without a designed or tested backup appears to be Thresher's demise.
    "In modern war... you will die like a dog for no good reason."
    Ernest Hemingway.

    In english "silence" means yelling louder than everyone else.

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    • #17
      Originally posted by Achtung Baby View Post

      USS Thresher was 2,400ft when she imploded, her collapse depth was 1,950ft. So the personal at Portsmouth Naval Shipyards actually did a commendable job in building the sub. The original court of inquiry's suggestion of flooding doesn't add up, I'll go into more detail about that later.
      I was thinking in terms of the size of the debris field. That's why I wondered how deep it was.
      Quis Custodiet Ipsos Custodes? Who is watching the watchers?

      Comment


      • #18
        Originally posted by Mountain Man View Post

        I was thinking in terms of the size of the debris field. That's why I wondered how deep it was.
        She broke up in six major sections, the majority of the debris field is around 400 hundred yards square. She imploded around 2,400 ft, and is resting at 8,400 feet. And given how far down she reached before the implosion, the quality of her construction cannot be dismissed.
        The pressure of the water at 2,400 ft was immense, it is estimated that the velocity of the water ram entering her compartments was 2,600 mph, or about 4 feet per millisecond. At those speeds, the ram would have traversed the maximum internal diameter of the pressure hull in about 0.008 seconds. The initial breach would have also generated a shock wave that propagated through the entire hull at the velocity of the speed of sound in steel, about 20,000 feet per second... five times the velocity of the water ram.
        That shockwave, acting on a structure that is already stressed to the point of collapse, probably triggered additional failure points before the flooding reached those points. This can tear the pressure hull longitudinally and vertically.
        USS Thresher was destroyed in 47 milliseconds, half the minimum time required for human cognitive perception of the event.
        Last edited by Achtung Baby; 24 Sep 19, 17:42.
        "In modern war... you will die like a dog for no good reason."
        Ernest Hemingway.

        In english "silence" means yelling louder than everyone else.

        Comment


        • #19
          I have read that air compressing at that speed literally ignites into a fireball. Is that the case?

          What do you see as the goal of the sub com's inquiry? Given what you've posted it appears that this was merely a tragic and unfortunate accident.
          Quis Custodiet Ipsos Custodes? Who is watching the watchers?

          Comment


          • #20
            Originally posted by Achtung Baby View Post
            The meaning of "900 North"

            '900 North' was Thresher's last UQC(underwater telephone) transmission to her escort ship USS Skylark.

            At 075 Thresher advised Skylark that her depth was 400ft.

            At 0754 Thresher advised Skylark that(for security reasons) all future references to depth would be given relative to test depth. The number 900 was thus an indirect reference by Thresher to her depth at 0917: 900ft below her test depth of 1300ft or 2200ft. The word 'north' is assessed to have been a direction. In this case 'up' as north is on a map, i.e. test depth was above Thresher by 900ft at 0917.

            This explanation was dismissed in the court of inquiry, because it required the Thresher's hull pressure to have survived greater than the crush depth of 1950ft. Furthermore, it would have invalidated their conclusion that flooding had occurred at test depth(1300 feet).

            The idea of flooding didn't add up then, nor is it even credible now. Thresher made no mention of flooding during her decent, nor did Skylark hear it. A test demonstration at dry dock No 2 at Portsmouth naval shipyard was held for the court of inquiry. A stream of water was released to atmosphere at Thresher's test depth pressure(580 psi) against a piece of electronic equipment. One witness Russell Preble, CDR USN (ret) observed that test, and said the noise was overwhelming, nothing could be heard over the noise. No orders could be heard over the roar of the water striking anything in it's way. This would have been heard by the men on Skylark, and observed on the underwater hydrophones that picked up the entire event.
            And given the size of the pipes that the court of inquiry claimed to have leaked, they don't seem to have calculated the amount of water that would have entered the sub in those six minutes(from 1300ft(at 0911) to the 900 north(0917) quote). Why the court of inquiry blame silver blazing when no reports of flooding was recorded, or reported, and Thresher survived without breach to almost twice test depth... it seems the court of inquiry was deflecting blame. It appears relying on the nuclear power plant alone without a designed or tested backup appears to be Thresher's demise.
            The flooding need not have been severe. A small.water leak over the electrical.conrols over the circuit breakers could have cause the reactor to scram and shut down, leaving the ship wirhout power. The ship could have been slightly negatively bouyant if it was still going down to design depth as part of the trials. Without power, the ship would keep sinking, and the deeper rhe sub sank, the less bouyant she became and the faster the ship would sink until it reached crushed depth, where it would be crushed like a can. I heard a.rumor that they could hear the USS Thresher crew banging on pipes, what they though happened was that there was a little moisture in the compressed air tanks, so that when they tried to form an emergency blow, the pipes froze, forming an ice plug.

            Nuclear submarines like the Thresher had use a lot of designs carryoverdd from the WW2 submarines, and these designs proved inadequate for the much deeper diving nuclear submarines - lots od seawater openings, brazing of joints instead of welds. Also, super cautious operating of reactors. At the time, when the reactor scrammed, procedure required shutting the steam throttles, leaving the submsrine without propulsion.. Procedures were later revised to allow rhe residual.stram in thr steam boilers to drive the submarine to the surface.

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            • #21
              She was heavily negative buoyant, it sank much faster than normal.
              The rumours about banging pipes is just that rumours, many experts have gone through the details and that would've been easily distinguished. The small leaks can't be ignored, IIRC the sub wasn't diving with the precautions of detailed checking for leaks as she went deeper.
              "In modern war... you will die like a dog for no good reason."
              Ernest Hemingway.

              In english "silence" means yelling louder than everyone else.

              Comment


              • #22
                Any report on how the lawsuit is going?
                Quis Custodiet Ipsos Custodes? Who is watching the watchers?

                Comment

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