Re: [PSUBS-MAILIST] PSUB Fatalities...

[MerlinSub@t-online.de (Carsten Standfuß)]

Hi Sean ..

"Sean T. Stevenson" schrieb:
> 
> On Tue, 07 Mar 2000 19:58:06 +0100, Carsten Standfuá wrote:
> 
> >The bottom time for free escape without stopping is about 1 minute in
> >90m deep...
> >Its   2 minutes in 80 m deep,
> >Its   2 minutes in 70 m deep,
> >Its   3 minutes in 60 m deep,
> >Its   4 minutes in 50 m deep,
> >Its   7 minutes in 40 m deep,
> >Its  17 minutes in 30 m deep,
> >Its  45 minutes in 20 m deep,
> >Its 653 minutes in 9 m deep,
> >
> >Carsten
> 
> Sorry to have to call you on this, Carsten, but it's garbage.  Where
> are you getting these numbers from?  You can not do a free ascent
> without stopping while using an escape aid, and expect to be fine
> because you are within the NDL of some arbitrary table.  Most common
> dive tables (PADI, NAUI, BSAC, TDI, IANTD, et al) utilize neo Haldanean
> compartment based decompression models, the most common of these being
> A.A. Buhlmann's ZHL-12 algorithm (Navy and DCIEM are experimentally
> derived representations of the same thing).  The Buhlman model assumes
> a 33 foot per minute ascent rate (the equivalent of making a 20 second
> stop every ten feet throughout the ascent).  The tables distributed by
> the dive training agencies are generously padded, but considering your
> likely ascent rate during a psub escape (using liftbags etc.) the model
> goes right out the window.  Add to that the fact that, in the event of
> flooding the psub, the trapped air inside (previously at 1 atm) is
> compressed, and at 90 meters would have a partial pressure of 2.1 atm -
> extremely dangerous in the water.  To avoid any sort of oxygen toxicity
> problem you would need to go on your escape gas from the start, which
> contraindicates using a bailout cyclinder with as limited a volume as a
> spare air.
> 
> I don't know how long the procedure of flooding the sub, opening the
> hatch and getting out would take, but I wouldn't bet my life on being
> able to do it on a breath hold.  Heliox 16 is the most logical choice
> for a bailout gas, because it gives the deepest range that is
> breathable all the way up, and eliminates the nitrogen to minimize the
> severity of the bend.  (When I say "bend" I mean it in the
> physiological context.  In some instances it may be entirely
> sub-clinical.)  This is a bit of a moot point.  Regardless of
> circumstances I would rather be bent and alive than the alternative...
> Obviously, the less time at depth the better, but your numbers don't
> really apply.
> 
> When discussing these escape scenarios, I was thinking more along the
> lines of a catastrophic loss of hull integrity, caused by a cracked
> viewport or failed through-hull fitting.  If I were merely disabled,
> provided I wasn't going to sink to the crush depth, I would just sit
> and wait for assistance until the life support ran out before bailing.
> 
> -Sean

You right and your are not right..

1.) You are right the partial pressure of oxgyen will be 2,1 bar 
at 90 m deep. And this is dangerous if you use it under this prssure
about a half hour or longer( Dr.med O.F.Ehm page 164). 

If your flooded vale needs a half hour to flooded your sub - I am sure
you have a big problem. If you sub flooded your sub in yust 2-3 minutes
you will not have a problem with oxygen poision. 

A way will maybe to switch off the oxgen bottle from your live support
system and let the CO2 Absorber running. After 40 minutes in my sub
the O2 indicator will be show that the partial pressure of oxygen is
gone from 0,21 bar to 0,17 - 0,11 bar , than switch off main battery
security switch, open flooded vale and you have plenty time against 
oxgen poison trouble. At 1,7bar about 5 hours.. before your lungs gets
irreparbale damages. 

2.) Another point is the bubbles in your blood during decompression.
You told that the tables gives a 33 foot per minute ascent rate. 
And thats is shit ! The dangerous area in this 90m accident are the last
20-30 Meter ! The rate in not constant. I now the table say its constant
but look from 90m to 80 m = 9 bar / 8 Bar  = 12,5% lower
pressure but from 20m to 10m is 2/1 bar = 100 % more pressure equil
bigger bubbels or in other words you can run from 90m to 45 m 
9/4,5 = 100% decompression in the same time (same size of bubbels in
your blood as from 20m to 10m or from 10m to zero. If your "stay" from 
90m to 80m with  33 foot per minute ascent rate your make a mistake !
Take hurry up in this deep and keep off your airball in 40/30 meter
deep. But right the total way should be in about 9 minutes - so a small
scuba gear will help... 

No problem with oxygen under pressure for short times - 
and I use also Bühlmann table (a old one from 1983). 
And I think its a lot of saftey in the tables. 

3.) If my window brokes - my lungs and parts of my head will be 
destroyed - I am shure of that - also I get a schock. So I will died
if my window broke. More intressting senario is that the main thruster
catch a rope or a net on a sunken wreck. So the drop keel will not help.
Than I have plenty of time to think about the situation. 

regards Carsten - sorry my english language but what is "garbage" ??