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Hi Philip.
You said on descent that air from the ballast tanks
has to be vented to the cabin in order to kieep the pressure equal with the
outside.
Is this actually what you meant to say, and do you
mean that as you decended you would utilize the ballast tank air to help
pressurize
the cabin and counteract the outside water pressure
or did you mean to say air from pressurized tanks instead of ballast tanks would
be used?
If you meant exactly what you said and didn't make
a mistake and actually mean "compressed air tanks" then I have this
below to advise you.
If you just use the air in your ballast tanks
to pressurize the cabin on decent, what are you going to do when the outside
water pressure exceeds
the volume of air that your ballast tanks
held? Then there will be no more air volume from the ballast tanks to compress
into the cabin to counteract the outside
water pressure. This means you will run out
of enough ballast tank air to compress into the cabin to counteract the outside
water pressure.
You asked if on accent if the pressure inside the
cabin needs to be vented to prevent the sub from exploding. The answer is
yes. If you did not make a mistake in what
you said earlier about your ballast tanks venting
to the cabin, perhaps if you were in a POWERED accent you could actually
vent some of the now overpressurized air from the cabin
back to the ballast tanks and
function PARTIALLY like the hunley submarine's recycleable ballast air
system did. Unless you made a mistake in what you said, your system
sounds
like you plan to use use your ballast tank air to
pressurize the cabin against the outside water pressure, but this means you need
a pressure hull once your outside water
pressure exceeds the air volume you have available
to compress into your cabin from your ballast tanks or else you will
implode the sub. This would mean you would not have an ambient sub,
or
you would be ambient until your ballast
tank air ran out, and then you would need to have a pressure hull or
else use compressed air tanks to make up for no more ballast tank
air
being available once you had used it
all and it was now compressed inside your cabin, and your outside water pressure
still needed to be counteracted. Personally I would not trust a
cabin
pressure release valve to always work. What if it
malfunctioned? If it stuck you could blow the sub apart. Of course you could
always have several
pressure relief valves for safety backup, but it
would be a whole lot easier if you just had an always open hole in the bottom of
your ambient sub. This way no pressure
relief valve would be necessary. You can make the
hole in such a way so that no water sloshes into the sub. Think of a sailboat
keel/skeg box for the way to make
your hole. You would have a box like projection
coming up from the hull bottom and at the top of that box would be your
hole. This way you never have to worry about
a pressure relief valve malfunctioning and blowing
your sub apart, and the air pressure in your ambient sub will keep the water
from coming into the cabin. If any of this is confusing
to you let me know and I will try to explain it
better than I have. I was handicapped a bit in giving the above answers by
not knowing if you meant to say "ballast tanks" or "compressed air tanks"
when
you described how you plan to pressureize your
cabin. Let me know if this helped or if you need further
explaination.
Bill Akins.
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