----- Original Message -----
Sent: Sunday, August 08, 2010 1:06
PM
Subject: Re: [PSUBS-MAILIST] escaping
from a K250 at 200ft
Hi, Alan
Yeah, we ran the 'pressure up and escape' numbers
for the micro sub 'Sea Urchin' some years ago. As I recall, escape from the
rated depth (350') was quite practical. As a rule of thumb, you save your
ballast air (and 02) for the final blow. The speed of initial filling is not
as critical as the last few minutes before the entry dome/hatch comes off. You
have to remember that when your sub is half -full of water, you are only at 33
feet of pressure (29.4 PSI), when it's 3 quarters full, you're only at 66' and
so on. My plan on the Sea-Urchin was to have the hinge on the inside
with the ability to pull the hinge pin out so that the entry dome is held
on only by water pressure - we planned to have two 'armpit slings' stowed in a
small package that is easily opened - and the sling ends were to be
affixed to the inside of the dome seat ring. The procedure for bail out was to
get a reading on the volume of the ballast air (by supply gauge) left, flood
up with water until either the time was beginning to exceed the no-decom
table (the depth IN the sub, not ambient depth) or you had flooded right
up. Probably, you'd blow the last 10 or 15 % by air, Make sure the slings are
firmly attached and blast in the air! The dome/hatch achieves lift-off with
your head and shoulders in the gas bubble of the dome, your body acts as the
drogue to keep the dome from tipping, you are breathing constantly-refreshed
air (and avoiding embolism, therby) as the gas expands and bubbles out - you
hit the surface and duck out and then yank on your Mae West cord to inflate
your life-jacket and await pick-up by your chase boat (or commence floundering
towards shore if you were subbing with no surface craft in attendance).
The numbers indicated that the likelihood of
bends was very low - since your exposure to full depth is extremely brief. We
were more concerned about the instant hit of hp nitrogen to those not
accustomed to deep gas change-overs. It can be quite . . .err. .
.'startling'! Hence the snugged-up slings- rather than internal handles ( my first thought) - even if you're
narked out of your skull at the onset the slings will hold you in position
until your calm. cool thoughts return. Actually, though, those stalwart
psubbers who are also tech -divers will recognize that the likelihood of bad
narcosis trip from this very brief 'deep air dive' is even less than the
bends (according to the work done by researchers Overton and Mayer on the
oil/water solubility ratios and the time required for the combination of Co2
and N2 to act.
I had developed a bubble stage
called the 'Newt-Chute' as a safety refuge and self-rescue/self-decom vehicle
for deep Heo2 bounce diving - which we (OII/Can-Dive) were doing a lot of at
that time (in the early 70's) I gave a paper at the Offshore Technology
Conference titled "Diving Bell escape systems - some observations and test
results) Perry started building and selling these bubble stages shortly after
that and then COMEX after them- and they became known in the industry as
'Class 2 bells'). While testing the Newt
-Chute, the dome-lift to the surface occurred to me and we tried it in several
different configurations and it worked fine. More than a decade later we
re-purposed the idea to sub escape.
Sorry for such a long answer,
Alan.
Phil Nuytten
----- Original Message -----
Sent: Saturday, August 07, 2010 3:48
PM
Subject: [PSUBS-MAILIST] escaping from
a K250 at 200ft
Hi All,
I know escaping from a sub has been discussed
before, but has anybody crunched
the numbers to see if it's possible from a
depth of say 200ft in a K250 or 350.
How long does it take to fill the hull with the
flood valve? The water would be coming
in at 100 psi but this pressure would diminish
progressively as the hull filled. At 3/4
full it would be 25 psi. At what stage would
you start adding compressed air
to help with the equalization of the hull &
how much air would you need & how fast would
it flow in?
If you filled your ballast tanks with air to
try and escape an entanglement first you might
not have enough left to help equalize the
hull.
When the flood time is known, how saturated
with nitrogen are you & what are your chances
of surviving the bends if you opened the hatch
& went straight up?
If this was pre calculated it might be
concluded that a scuba tank (or 2) was needed & decompression
stops at varying depths & times were
necessary.
I don't know the internal volume of a K250, I
think the flood valve is 2"
Regards
Alan