----- Original Message -----
Subject: Re: [PSUBS-MAILIST] acrylic dome
escape pod question for Cars.
>One thing I am wondering about is, once you
pressurize the hull to ambient so the dome will lift off taking you to the
surface,
>this means your lungs are now filled with
pressurized air instead of 1 atmosphere air. Wouldn't this mean you would have
to
>forcefully expel the air by saying a loud
AHHHHH or even yelling as you rose to keep the pressurized air from bursting
your lungs
>rather than just breathing normally like you
said to do?
Yes, your lungs are now at ambient. No,
you don't have to yell or be loud at all. Vocalizing is a feedback
system letting you know that your trachea is, in fact, wide open and expelling
air on the way up. You should never have to forcefully expel air -
Boyle's Law will take care of that for you :-)
>As the dome rose the air in the dome would
spill out the bottom as it expanded
>and the air remaining in the dome would
become less pressurized so as you breathed that dome air you would be
breathing steadily
>decreasing in pressure air. So as you rose
and breathed out of the dome you would not burst your lungs because the
air
>you were breathing from the dome was
decreasing in pressure. That would work if you rose slowly.
A rapid ascent as Carsten suggests does
require a wide open trachea and breathing normally will be a bit of a
challenge depending on the rate of ascent. If the roa was very
controlled, then normal breathing is fine. The real world, IMHO, is a
little less forgiving than that and most emergencies require rapid responses,
i.e., I'm outta here now.
>But in reality wouldn't the dome rise so fast
that there would not be time for your lungs to
adjust to the decrease in air pressure before >they burst from the rapid
ascent and air expansion?
Not at all! The dome WILL provide
a rocket assist to be sure - I mean, it's shaped like a bullet!!!
Compare the ID of your trachea with the volume required to vent from your
lungs and you'll see what I mean. Lots of ID and a very small lung
volume. Nevertheless, I would never personally use a dome to assist
me. You need SOME time for the N2 to dissolve and shift
around.
>Also what would happen if you lost hold of
the handles? Do you think it might be a good idea to have a shoulder harness
on that would >clip attach to the handles on the dome so if your hands
lost hold you would not lose the
dome?
If you let go of the handles you'll come up
slower (unless you were wearing your Daytons - mean looking leather
biker-boots). Your lungs will bring you up if you have street clothes
on. A dome assisted ascent would be fine for the first bit (a very
relative term), but, at around one atm. I'd let go of the damned thing and
flare out (arch by body backwards) to create more resistance for that last ten
metres. That's the part that's going to kill you. The expanding
air in your lungs will ensure you do not black out - it's truly a weird
sensation to not breathe on an emergency ascent and yet have plenty of
air. Mind you, this is a short term measure. Even aerating the
lungs with pure O2 is not enough to bring O2 into the body - you have to move
the lungs to cause a gas exchange into the blood stream (Google:
ICU ventilators)
Hope this helps! :-)
Rick Lucertini
Vancouver, Canada
Hi Bill..
Proposal for an emergency procedure to get
out of a
boat with top side dome:
- Open the holder for the dome -outside
pressure will hold him in place.
- if nessesary remove hinges holder
bolts.
- Open the big flood vale in the bottom area
- if abvailable
open also the remains of compressed storage air to
the
cabin to speed up the compression process.
- if inside and outside
pressure is equal the dome will lift away -
make sure that your
hands on the two inside handles of the dome and
you head is inside
the dome bubble.
- This parachute dome will lift you with a high spped to
the surface -
make sure that you breath normaly in and out. Make sure that
the design
of your flood vale is that way that the flooding get quick - so
that you
have not to much time to stay under higher pressure - because of
the
decompression tickness..
best regards
Carsten