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Hugh, It was hard for me to reconcile at first also. It is a
density issue the air being buoyant wants to rush out and it sucks you out with
it and it entrains water with it. I once cracked (fortunately didn’t
open it fully) a hatch on a sunken sub at 135 fsw. The ensuing gas escape
caused a strong suctional force upward and resulted in a boil 30 feet in
diameter and a foot high at the surface…pushed the surface support boat
back to the limits of its mooring. The Brits went back to the Med and tested a later version of
their escape apparatus/exposure suit and broke their record by a short distance.
The US Submarine Service has now adopted the British-style escape apparatus (I
believe the Mk-10) and retired the Steinke Hood which I have previous used in practice
as part of submarine training. It is a rapid express train ride to the surface! In my presentation was a table and graph that should for various
depths how long you have to get out of the sub and start for the surface.
The deeper the water, the shorter the time period. You can’t
realize how debilitating the temperature of the water can be. Reading
accounts of previous escapes and talking with one of the survivors from the USS
Squalus really sinks home that you want to make your escape efforts as soon
as possible if a better solution is not available. Something to keep in mind that when we speak of hoods and escape
apparatus from subs, this gear is all made for large subs with dedicated escape
chambers that facilitate using this escape gear. We don’t have that
option in most PSUBS. R/Jay From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Hugh Fulton Hi Jay, Obviously agree with you on flooding etc and getting out but cant
reconcile with being blown out if the sub was full of compressed air.
Just from a theoretical point of view:- As it would be at same pressure as
outside it would similar to opening the hatch at 2 ft below the surface with
just a huge inrush of water and the problem as I see it would be the same as
trying to exit a toilet bowl while flushed!! ( We Downunder always revert
to toilet humour) However I do remember seeing an escape hood which
has been successfully used from about 600 ft I believe was the figure
claimed. However being a diver myself and having been down to 185 ft with
Scuba it’s a hell of a long way up without fins. I would be
interested in how the hood actually functions. I understand it has a
small pony bottle but don’t know what capacity. I think that flooding through a valve would give time to equalize
your ears and provided you had your head close to the top the air would be
compressed by the flooding of the water to the point where you would need to
submerge your head and start with the breathing apparatus. We should work
out what the time frames should be as if the size of valve is stipulated then
it could be worked out. The hood idea is the best as expelled air can be
rebreathed and a constant flow of replenishing would give buoyancy to the hood
etc etc. Interesting but scary. http://www.silvercrestsubmarines.co.uk/news.html
is the link to see the escape suits. Just hope we never get into that circumstance. Regards Hugh |