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Hi Patrick.
To answer your question, the answer is yes. As long
as your hull will withstand the interior pressure and not burst
outward when you reach the lessened external hull
pressure at the surface. This is getting into
decompression diving
though. You don't want to go there unless it is an
emergency and you got stuck too long on the bottom and have no
choice other than to surface immediately or
die.
In that case always carry DECOMPRESSION as well as
no decompression dive tables with you and always time your bottom time like any
diver. Then you will
know how much pressure to let out and at what
intervals before you can pop the hatch. But there are too many things to go
wrong
and kill you as I have said before. Yes it is
possible. I wouldn't recommend doing it on purpose. Imagine for a moment that
you
are going underwater in a surface style
decompression chamber. That is basically what you are doing. At scuba depths
for
SCUBA diving tables times, (NOT decompression
diving tables) your decompression chamber is only exerting a small
amount
of pressure on your body with the increased
internal hull pressure needed to counteract the external water pressure. At 30
ft
(according to PADI scuba dive tables) depth you can
stay for an absolute maximum of 205 minutes. At 40 ft it is 140
minutes,
at 50 ft it is 80 minutes, at 60 ft it is 55
minutes, at 70 ft it is 40 minutes, at 80 ft it is 30 minutes, at 90 ft it is 25
minutes, at 100
ft it is 20 minutes, at 110 ft it is 16 minutes at
120 ft it is 13 minutes, at 130 ft it is 10 minutes, at 140 ft it is 8
minutes.
Normal breathing air mix scuba diving without
decompression (called no decompression diving) does not go deeper than 140 ft.
Then as Rick pointed
out there is mixed air such as nitrox that allows
you more bottom time because it has a higher concentration of of O2 in the mix
so
you do not saturate with nitrogen as quickly. You
will learn about nitrox mixed gas diving if you first get certified as a open
water diver
and then take your advanced divers course and
include your nitrox course in with the advanced course. Now imagine you stay too
long on
the bottom or get stuck after staying too long and
get free, but before you get free you closed your pressure release valves
because you knew when
you dropped the decompression chambers weights it
would rocket up and if you decompressed that fast it would kill you so you
closed the valves, drop
the weights and rocket to the surface. You had
better have built a very strong hull to withstand that kind of pressure because
if it blows apart and you
are instantly decompressed you WILL die. If you
have to build a hull that strong you now have a hull that is strong enough for a
1 atm sub which you
could have built in the first place and never got
stuck in this decompression situation. DANGER, DANGER, DANGER. You might survive
but my bet would
be the hull would blow and so would you with
resulting death from rapid decompression chamber failure. Remember the James
Bond movie where the main bad guy put one
of his own henchmen into the decompression chamber?
Then he pressurized the chamber and then hit the viewport window with an axe
instantly decompressing
the chamber and instantly blowing the henchmans
eyes, eardrums and guts out. Do you see now why this would not only require a 1
atm strength hull but
would be extremely dangerous even with a 1 atm
hull? What if a valve or its back up valve both sticks and you cannot bleed
pressure from the boat slowly at the surface in accordance
with your emergency decompression diving tables?
Now your body is pressurized and over saturated with nitrogen and you are
sitting at the surface in your decompression
chamber not able to decompress slowly nor at the
proper intervals and running out of air which will eventually make you open
the hatch which will blow open forcefully instantly
decompressing the sub and you die. I would
not want to be in that situation. Anyone out there interested in trying it
now?
Bill Akins.
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