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The sinking of the Scorpion SSN 589

  1. Aug 4, 2011 #1
    To all,

    I have a problem I would like to solve and I need help. Just some background info to start. I was a member of the crew aboard the Scamp SSN 588 the sister ship to SSN 589. Ever since she sunk I have always wondered why she sunk. Now I believe there is a viable answer to this question. An acoustics expert has listened to the sounds of her demise and is convinced that a hydrogen explosion in her battery compartment caused her to ultimately sink.

    His scenario goes like this. During battery charging one of the battery terminals overheated and melted and caused a spark that ignited the hydrogen in the battery compartment. The force of this explosion, he estimates that 2 explosions of 20 lbs of TNT each approximately .5seconds apart, damaged the interior superstructure to the extent that it disabled/killed the crew and she started sinking, from there it took approximately 22 minutes till her pressure hull collapsed.

    To see an internal view of her watch this video, at the end of the video you can see how her wreakage was strewn over the ocean floor.:

    http://www.youtube.com/watch?v=0fPxtFVl4Gs&feature=related

    Too see the report go here:

    http://www.burtonsys.com/USS_Scorpion.html

    Looking at the interior of the sub, the batteries are in the bottom compartment next to the keel under the crews quarters, above that is the officers quarters and mess hall, above that is the control room, sonar shack, yeomans shack and radio room.
    Forward behind a water tight bulkhead is the torpedo room aft is a fuel oil tank for the diesel engine that helped with radiation protection from the reactor compartment aft of it, then the engine room then the steam generator compartment.

    So it goes like this: Torpedo Room /Bulkhead/ Control compartment /Oil Tank-Bulkhead/ Reactor Compartment /Bulkhead/ Engine compartment /Bulkhead/ Steam Generator Compartment- Shaft Alley/ Propeller with a water tight boot of course.

    Now to my problem.
    Could 2 explosions equivalent to 2 20 lb TNT detonations (.5 seconds apart) cause enough damage to totally disable/kill the crew.

    I know this is a daunting task and that a scale emperical model would be financialy unfeasible
    but, is there a modelling program out there that could model this event, and if so, who would volunteer ;-)

    Also, does anyone have any information about the force that 20 lbs of TNT can generate?
     
    Last edited: Aug 4, 2011
  2. jcsd
  3. Aug 4, 2011 #2

    Drakkith

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    Staff: Mentor

    I don't know if it could have totally disabled the entire crew, but would that be necessary? Is the location of the batteries close enough to enough major systems to cause failure and sinkage as a result of the explosion, even the crew attempts to prevent it? I'm not familiar with subs, so I don't know how many redundant systems they have or what the escape options for the crew are in case of emergencies.
     
  4. Aug 4, 2011 #3
    Drakkith,

    There is a "Trim Pump" at the forward end of the crews compartment, if it was torn from it's pipe attachment in a certain way it could lead to flooding.

    I guess my ultimate question would be, could these 2 explosions 20 lbs of TNT each .5 seconds apart have enough energy to blow the floor of the crews quarters apart and cause serious internal damage to all the compartments in the control section.

    If someone knows just how much energy is in 1 stick of TNT that could be used to make some SWAGS I'm guessing.
     
  5. Aug 5, 2011 #4
  6. Aug 5, 2011 #5
    gmax137

    I would hope by reading my thread it would be obvious. I guess I wasn't clear, so let me clarify. Since the explosions took place in the battery compartment, which is below the crews quarters, how much force would be required to breach the floor of the crews quarters (since it is also the roof of the battery compartment).

    From what I remember it is approximately 3/8" steel plate with an area of approximately 30' x 30'. I do believe the steel used is HY 80 which has a tensil strength of 80 KSI.

    Since your response was in Joules and ft/lbs, I'm not sure that is useful information, in this situation, since I'm trying to figure out how much pressure (psi) would have been exerted on the crews quarters floor.

    I know the battery took up most of the space in the battery compartment, below the crews quarters, but there was a space (approximately 3 feet) between the top of the batteries and the crews quarters floor. so if we take 30' x 30' x 3' we get a volume of ~2700 cubic feet. If the energy you have provided (42 million joules x 2 = 84 million joules) were released in less than 1 second, how would that affect the floor of the crews compartment? In other words, how much pressure (psi) would be exerted on the crews quarters floor?

    I'm pretty sure this is the Physics forum, I'm hoping someone on here is curious enough to try and help me solve this problem ;-)
     
    Last edited: Aug 5, 2011
  7. Aug 5, 2011 #6
    Tommy - you asked for the energy content of TNT; that's what I gave you. I do not know how to use that to determine the pressure in the battery room and whether it would be enough to rupture the floor. Those are two separate questions and neither one is easy to answer. That's all I meant by saying 'not sure what you're going to do with the info.'
     
  8. Aug 5, 2011 #7

    RonL

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    Gold Member

    I can't give much in the way of numbers, but maybe I can help you understand what those forces will do.
    Testing for leaks in fuel and water compartments of push boats being built, we were very careful to not exceed 1 to 1-1/2 PSI, at that pressure the bulkhead walls would flex slightly and the sound was like an explosion or loud gun blast (a bit scary to say the least). Soapy water sprayed on any welded seam or fitting would show bubbles from even the smallest pin-hole opening in the weld.
    If you have seen video of a percussion bomb destroying a building 50' or so below, then think of some extreme blast in the confined area of the inside of a hull, even without numbers I can without any question think the reasoning is correct, that an area inside the hull would have quickly been over pressured to point of failure.

    Just my opinion, based on using low pressure air in large volume tanks.

    Ron

    P.S. We used a compressor that could deliver 250 CFM @ 120 PSI, the fitting and control valve (IIRC) was 3/8", the time to bring pressure up was not long at all. I don't know an exact figure, but on a volume of 2700 cubic feet I think 5 PSI would distort the walls and fracture most welds.
     
    Last edited: Aug 5, 2011
  9. Aug 5, 2011 #8
    Ron,

    Thanks for the reply. Do you remember how thick the bulkhead walls were? I'm hoping someone can help me convert 84 million joules of energy released in less than 1 second into psi in a confined space of ~2700 cubic feet. I would think this is a classic physics problem, but I can't find the information I would need to make the calculations, or should I say, even if I did I probably wouldn't understand it ;-)
     
  10. Aug 5, 2011 #9
    I think it is a matter of the weakest point, not the entire mass of the walls.
     
  11. Aug 5, 2011 #10
    gmax137

    I hope I didn't offend you, I was only trying to explain what I wanted the information for and trying to clarify the problem. I am still hoping someone can help my in converting the 82 million joules released in less than 1 second into psi in a confined space of ~2700 cubic feet. I'm wondering if this was ever used as a physics question in a physics test, but maybe with different numbers?
     
  12. Aug 5, 2011 #11

    RonL

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    Gold Member

    As I recall, most interior bulkhead walls were 1/4", 5/16" or 3/8", depending on how large of an area that had no intersecting support, such as the engine room. all bulkhead sheets were reinforce with 1/4" thick angle irons,in general about 3"X4" or 4"X4", in most cases vertical on one side and horizontal on the other.

    I think the technique of "explosive molding" will offer some insight on how the interior of the sub was affected, I will look later today, but you might try wiki and see what shows up. A look into "air tank rupture" will also give information about the devastating effects of high pressure gas volume release.

    My method of energy to pressure calculation would most likely be unorthodox I'm sure, so maybe someone else will step in, I'll check back later today.

    Ron
     
  13. Aug 5, 2011 #12
    some facts
    Detonation velocity
    TNT - 6940m/s
    pentane - 1680m/s ( flame speed of combustion = 0.34 m/s )
    hydrogen - ??

    1 gram of TNT produces about 1 litre of gas
    20 kg of TNT produces about 20,000 litres of gas

    1 litre is 10cm^3 ( a cube 10 cm on each side )
    1000 litres is 1 m^3
    20,000 litres is 20 m^3 ( or about 2.7 m on each face of a cube )

    If you know the size of the compartment you can calculate the increase in pressure, by the explosion of 20kg of TNT.


    Next you could attempt to calculate the amount of hydrogen needed so that in an exothermic reaction with oxygen, the pressure in the compartment would amount to the same.

    Questions:
    1. Would the batteries have been able to produce that amount of hydrogen?
    2. Would that amount of hydrogen have been able to accumulate, or allowed to accumulate, considering that some type of aeration system would have been operating?
    3. Would there have been enough oxygen in the compartment to enable a stoichiometric reaction?
    4. Is the detonation shock wave of the explosion more important than the rise in pressure and temperature.

    Hope that helps, and recheck my calculations for verification.
     
  14. Aug 5, 2011 #13
    256bits = 32 bytes ;-)

    WOW! THANK YOU 256! Now we are talking. Let me answer your questions.

    1. & 2. Yes, when lead acid batteries are subject to an equalizing charge (to help slow down the sulfation process) there are copious amonts of outgassing. Approximately every 10 charge/discharge cycles a equalizing charge is applied, it is a higher voltage than normal charge voltage. Thus the ventilating fans should be run at high speed during this charge.
    I can remember guys responsible for the battery charging on the Scamp indicating that hydrogen generation was getting too high and they needed to stop charging the battery.

    3. This is a good question, I would think that the oxygen in the incoming ventilation air would possibly supply this. This is why I think there were 2 explosion within .5 seconds of each other. The first explosion used up all the available oxygen within the stoichiometric range but when the floor of the crews quarters was breach extra oxygen flowed in and resulted in the second explosion.

    4. This is a very good question. I am familiar with the flame front you get in internal combustion gas engines where the air/fuel mixture when ignited results in a rapid flame front but not an explosion as in a diesel engine, where detonation of the fuel is utilized.

    The Detonation Velocity of of Hydrogen gas in a confined space is ~1650 - 4000 meters per second depending on the concentration of the hydrogen gas.

    The Compartment had ~2700 cubic feet of free space. So, I'm not sure how you would go about calculating the pressure increase in the compartment. Since 20,000 liters of gas is 706 cubic feet how would the calculation look?

    I'm thinking the detonation shock waves would be devastating. That begs the question, what would be the instantaneous forces applied to the underside of the crews quarters floor?
     
    Last edited: Aug 5, 2011
  15. Aug 5, 2011 #14
    From what I can gather from calculations on the web it looks like a confined hydrogen explosion will produce ~ 8 bar pressure. That equals ~120 psi in less than 1 second.

    With the crews quarters floor ~129,600 square inches we end up with ~7776 tons of pressure applied to the underside of the crews quarters floor. Since a large diesel locomotive weighs ~150 tons that's the weight of 51 freight trains!
     
  16. Aug 6, 2011 #15
    You are asumming? that the whole battery compartment was filled with explosive gas. That would be the worst case scenario.

    Getting back to the TNT.
    Quick calculation
    P1V1 = P2V2
    1 atm x (2700ft^3 + 706 ft^3) = P2 x 2700 ft^3

    P2 = 1.3 atm
    or 0.3 atm above normal pressure in the sub interior
    Assuming the sub is at 1 atm=14.7 ( not sure what their interior pressure is maintained at )
    that gives 4.41 psi
    that is a rough calculation.

    Roni posted that in their pressure testing they would not exceed 1 to 1-1/2 psi.

    Would 4.41psi been enough to cause a rupture?
     
  17. Aug 6, 2011 #16

    RonL

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    Gold Member

    Most of our test were between .5 and .75 PSI, as I suspect 4.41 PSI would produce a force that caused flex across a large area and the result could have ripped apart any number of pipes that might have been conduits of different types of explosive liquids or gases. Plumbing under the floor plates would be logical to me.

    The batteries might have only been the trigger event, but the time factor for an explosion can be pretty quick.

    Lots of things to speculate about, I know nothing about submarine design and mechanics.

    Ron

    P.S. For what it might be worth, floor plates are generally designed to be very easy to lift and put to the side, in order to have access to anything under them. But that would depend on whether a sub is built to roll over similar to aircraft.
     
    Last edited: Aug 6, 2011
  18. Aug 6, 2011 #17
    That is just an estimated 4.5 psi from the expansion of the gas of 20 pds of TNT. A shock wave from a rapid expansion adds to the destructive power, with the pressure front being ballistic and concentrating the force temporarily.

    I guess the explosion of hydrogen gas would do likewise damage.
     
  19. Aug 6, 2011 #18
    256bits

    Thanks again for the reply. If you look here and use "Hydrogen" for the gas they too calculate ~120 psi, you need to go down the page select a gas then input how many pounds, if you input .7 lbs of Hydrogen click calculate then scroll down the page to see the answer, it ends up being ~20lbs of TNT:

    www.nrc.gov/reading-rm/doc-collections/.../15_Explosion_Calculations.xls[/URL]

    Anyway let me know your thoughts on this calculator.

    4.41 psi would equal 285 tons of pressure, that's ~2 Freight Trains. I would have to say even that would rupture the floor.
     
    Last edited by a moderator: Apr 26, 2017
  20. Aug 6, 2011 #19
    I don't know if this is helpful, but an H2/air mix that is more than 75% H2 will not explode (that the "upper explosive limit").
     
  21. Aug 6, 2011 #20
    256bits

    Yeah, that's what I'm thinking it's not just the pressure from the expansion of the gas but the force applied by the shock wave. The acoustics expert indicated that they were explosions.
     
    Last edited: Aug 6, 2011
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