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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.

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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?

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