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Regardless, you still need compressed air to blow
the tanks. Exterior main ballast tanks really only need to be blown near
the surface, where the pressure is less (unless you need some kind of emergency
blow). Just enough to keep you afloat/sink. It's always smarter to
have a pressure tank instead of going "direct". The main ship compressor
simply maintains say a 3000 psi level at all times, either from surface air or
bladder air. All other ballast tanks are blown from here. Military
subs go up and down in this way I'm sure as it doesnt give off any bubbles, and
they raise/lower depth an unlimited amount of time; simply recycling the air
they have.
Figure, you can hold a closet-full of air inside a
small scuba tank. That's plenty. Of course, the initial main ballast
vent would be to the atmosphere since it'd probably take FOREVER to compress
them into a tank. Being able to get the air back into the sub
just seems like an extra layer of flexibility, albeit unnecessary since you can
just use the outside air - hehe. That main vent would simply be a one-way valve
to keep the water out of the bladder btw.
As for the rest of the smaller ballast/trim tanks
they could more easily/quickly be compressed back into the main compressor
tank.
I guess you could say if you had a ballast/trim
system that really only employed a few tanks it'd be beneficial to use a bladder
as u could use it at depth to raise/lower depth without wasting air or having to
build a bulky ballast tank. The positive pressure outside the bladder aids
in getting the air back into the main compressor tanks.
Anyways, just thoughts. Those kevlar pressure
bags are very expensive. But it limits component exposure to the
elements and cuts down on airspace. Only really pays if you're
building the "ultimate sub" and mostly is beneficial for consumable and
waste tanks. Using them for ballast tanks just cuts down on the
steel I guess. Still fun to dream though. :)
All in all, composites are the future for
sub-building. We all know this. Fun to think of ways to apply the
technology.
SH
p.s.
btw, I looked up a few compressors. The ones
fire departments use can do like 20 cubit feet/minute at 6,000 psi.
Obviously much faster at lower pressures. Of course, then you have to
factor in the total airspace added from using a large compressor to begin
with. Would simply using more TANKS be better?? UGH! too much
to think about.
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