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Re: [PSUBS-MAILIST] Pressure hull materials
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Good Morning:
I am new to the list and not very well versed in the subject, though I have
to say that I find the topic of your discussions fascinating. On the subject
of pressure hull materials I have a few thoughts. Perhaps someone with more
knowledge/ability/money can make use of it. If nothing else... perhaps it
will provide you with some amusement.
The basic function of a hull, as I understand the concept, is to provide a
"bubble" of air for the occupants of the submarine to breath. Now, if you
want to maintain an atmospheric pressure similar to that found at sea level,
you need a very rigid structure because the water pressure at depth will tend
to compress the shell. If one is not concerned with this, the hull's
rigidity is not at all a concern. Bubbles can form in great depths with
nothing but the surface tension of the water to hold their shape.
Now, suppose someone were to form a thick clear flexible plastic "bubble"
with a conventional rigid hatch and seal for entry/egress. One could
concievably use an old water bed mattress. As the "bubble" descends, the
non-rigid hull would compress. One could equalize this pressure by
compensating with bottled air. You would have to have a pressure valve
somewhere to keep the bubble from bursting from internal pressure.
Equalization could be maintained by simply opening the valve whenever it is
noticed that the hull is collapsing until air bleeds out through the pressure
valve.
The craft would have to have a light framework to affix things to... life
support components, electrical devices for light, etc. It would be not
unlike a semi-rigid dirigible... and the bottom of the craft would have to
have some ballast to maintain equilibrium as well as to allow it to sink
below the surface. Variable ballast tanks could also be formed from the same
stuff... though they would function more as "anti-ballast" tanks, since it
would be the absence of air that would cause the device to sink.
One obvious drawback would be the necessity of decompression... and I suspect
that there would be a very definite absolute depth limit... maybe a hundred
feet... but in small lakes and rivers, that would be sufficient. You'd have
to watch your time, just like a SCUBA diver, and come up slowly, allowing the
overpressure to bleed out.
For a model, a zip-lock plastic bag would suffice. Put a CO2 cartridge
inside it with a valve assembly for equalization experiments.
One other question.... Bushnell's Turtle as well as the CSA Hunley utilized
simple muscle power for propulsion. They didn't have electrics or internal
combustion engines. Has anyone postulated a modern Hunley that would use the
same type of propulsion?
OK, go ahead and laugh at me. I'm sure I've said more than a few amusing
things... but if my flexible hull concept is flawed, I would like to know why
it wouldn't work.
- --
Dale A. Raby
Editor/Publisher
The Green Bay Web
http://www.thegreenbayweb.com
Nothing is ever so bad that it couldn't be worse, and if it could be worse,
then maybe it's not so bad!
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