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Water, Pressure, & Submarines

  1. Dec 10, 2013 #1
    First of all, I would like to say hello to everyone! I am not sure that this is the right place to post this, or even the right forum. Looks like everyone is very knowledgeable here, and I hope someone can help me with some issues.

    My name is Jim. I am with Spektrum Industries.

    We specialize in many different industries; from Computer (IT) to Watercraft and Military applications.

    We are currently working on a prototype of a submarine. We do not have anyone on board that can assist us in answering these questions.

    However because we are in need of some help, if we are able to find someone that has the experience and knowledge in physics that is required for this, job they might have a position at our company.

    1.) If you have a cylindrical shaped submarine 8 feet in diameter, and you are 33 feet under the water, what would be the pressure per square inch applied to the submarine?

    2.) If the submarine changed depths from 33 feet to 66 feet, would the pressure per square inch double or be a completely different number?

    3.) If the submarine is made of steel, 8 feet in diameter, 18 feet long, has rounded ends, and the steel is 1 inch thick, at what depth would it implode in salt water?

    4.) With a regular plate glass window (like lexan glass - bullproof) 2 inches thick, and placed inline with the outside of the submarine, at what depth would this glass window experience issues?

    Is there a depth at which the water would destroy the window. (Shear)

    Thank you again in advance.

    If this is not the right forum, and you know of another one, please advise.

    Thank you.

  2. jcsd
  3. Dec 10, 2013 #2


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    Hi Jim. Welcome to Physics Forums!

    To answer several of your questions I used Google search. After approximately two minutes and eight seconds I found this from the Office of Naval Research:
    Ocean Water: Pressure
    Even though we do not feel it, 14.7 pounds per square inch (psi), or 1kg per square cm, of pressure are pushing down on our bodies as we rest at sea level. Our body compensates for this weight by pushing out with the same force.
    Since water is much heavier than air, this pressure increases as we venture into the water. For every 33 feet down we travel, one more atmosphere (14.7 psi) pushes down on us. For example, at 66 feet, the pressure equals 44.1 psi, and at 99 feet, the pressure equals 58.8 psi.

    To travel into this high-pressure environment we have to make some adjustments. Humans can travel three or four atmospheres and be OK. To go farther, submarines are needed.
    Animals that live in this watery environment undergo large pressure changes in short amounts of time. Sperm whales make hour-long dives 7,380 feet (2,250 meters) down. This is a pressure change of more than 223 atmospheres! By studying and understanding how these animals are able to withstand great pressure changes, scientists will be able to build better tools for humans to make such journeys.

    http://www.onr.navy.mil/focus/ocean/water/pressure1.htm [Broken]

    What would the salary for the position at Spektrum Industries be?
    Last edited by a moderator: May 6, 2017
  4. Dec 10, 2013 #3


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    I'd like some of that too. Or perhaps a consultancy fee - either to help with submarine specifications or help with Google searching.
  5. Dec 10, 2013 #4

    Thank you for the quick response. I am sorry I should have been a bit more clear about what I meant. This article in which you posted in good, but I need something a bit more technical. Plus there are questions still unanswered, such as the how a cylindrical steel shape can withstand water/pressure and how much. Is there a formula.

    As far as Spektrum Industries is concerned this is only a research project and right now minimal funding has been given to see what the costs would be to design such a vehicle. So at this point in time there is no salary associated with this.

    I am very confident however that in the near future there will be positions opened for those that have the knowledge and ability to construct and use products such as AutoDesk/AutoCAD to design and implement a working version of what we are talking about here.

    Thank you for your response.

  6. Dec 10, 2013 #5

    Thank you for that comment. I understand that these questions may be either confusing, or like we are trying to get free answers to a serious problem.

    Realistically what we are trying to do right now is simple look at the possibilities of doing this. There are other companies out there that make submarines, such as TitanSubs, however we wish to design something a bit more industrial commercial, for heavy duty applications.

    Right now our budget for this operation/looking at the possibilities and research is 20,000.

    We need to find out exact pricing to make a prototype and then we can submit for more funding. We work directly with other large enterprises that have agreed to fund a project, again depending on the feasibility.

    Thank you for your comment.

  7. Dec 10, 2013 #6


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    Jim, if you are going to play with submarines, you'll need a critter called a 'naval architect'.

    You don't specify what kind of 'watercraft' work Spektrum does, but there might be one of those critters lurking nearby.
  8. Dec 10, 2013 #7

    We are in the process right now of trying to find a Naval Engineer/Architect but it has become a very hard challenge. Also the one person we did find was unable to help as he had prior obligations and would only help if offered a full time position. So we are in between a rock and a hard place.

    Once we have numbers, cost, time frame, materials, etc I can submit to our financial department and build a development team. But I am a bit lost. Trying my best here.

  9. Dec 10, 2013 #8


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    This is a demanding project and the first thing you need is some serious structural design expertise (what drawing package you use is pretty secondary importance). You need someone on board for whom the simple basics about hydrostatic pressure and strength of materials are second nature (from your questions, it seems you have little knowledge of these things). Once you are at a few atmospheres of pressure, absolutely Everything is harder to engineer. Is this venture of yours a commercial one and do you think you have found a possible market slot? If it is, then I suggest you try something a bit less technically risky. There are good reasons why small Subs are very expensive.
    I cannot find any reference to your "TitanSubs" on Google.
  10. Dec 10, 2013 #9
    I am sorry, I meant to type "TritonSubs" dot com. This is definitely a commercial project. I just need to find these people which seems like finding a needle in a haystack.
  11. Dec 10, 2013 #10


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    I rather guessed this was commercially speculative rather than based on Engineering Zeal. You are risking all the time and money you invest if you are not prepared to pay an awful lot of money on the necessary expertise. You not only need someone who is proven to be good but you need to be able to recognise the quality of the work being done. I think the expression is 'critical mass', which is needed for a successful project of this nature. Optimism is not enough; you need a healthy skepticism about these things. How much profit (real) is Triton Subs actually making, I wonder? Very low volume, very high risk. There are hundreds of small firms that have gone to the wall, even in the well established business of boat design and building.
    Otoh, you have an advantage in the existence of many modern materials that are available, making this sort of thing much more feasible than it would have been a few years ago. I should certainly like a ride in something like the Triton Subs company produce - as long as it has a good track record of not drowning people.
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