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Jay, It sounds like it's worth the time and effort to design the conning tower to have large enough valve(s) to let all the air out when you need to fully flood the sub. If you can hold your breath for a bit towards the end when your using a SCUBA regulator to breath, then you can open the hatch with no air under it. I would like to avoid getting ripped out of a sub if at all possible. I spent some time talking to my relative Carey that has built two hyperbaric chambers and he reminded me of a couple things and brought up another idea I would like us to consider. First he liked the idea of adding compressed air to be able to equalize the pressure in the sub to the external pressures so you can safely compress up without collapsing your ear drums. This of course keeps you warm and dry longer and the compressed air you aid, will heat the air to some degree. Of course in this state your absorbing nitrogen, so you would need to do decompression stop on your accent, which takes more equipment. In this scenario, once you have equalized the air and your ready to flood the sub, you can do so quickly without hurting your ears and be exposed to the cold water in the sub for less time. Of course doing decompression stops will not be fun unless you are wearing some great gear. So what was suggested was to breath pure O2 for about 30 minutes at 2 atm then compress up the interior of the sub, to clear all the nitrogen out of your body. You will not get oxygen poisoning in that short of time, and since the O2 molecule is so much smaller then the nitrogen molecule you can then exit the sub and go straight for the surface without getting the bends. At 2 atm it should take about 3.5 hours to get oxygen toxicity breathing pure O2. You might very well be able to get the nitrogen out of your body faster while breathing 100% 02 at higher pressures. But I'll have to see if I can find some tables and other materials on that matter. So how does one breath pure O2 inside a submarine and not have the O2 released into the subs air space where it can explode if there is a spark? We had a three ideas of how to do that, but we need to work on the issue a bit longer. One idea was to use a small high pressure compressor with a couple of check valves to slowly suck out the air your breathing to the outside of the sub using a modified two way regulator mask like we use to breath pure 02 in a hyperbaric chamber. Another was to configure a rebreather system to breath pure O2, but since you would need to exhale the nitrogen, you would also be exhaling a lot of extra O2 into the sub. I'll have to refer the rebreather option over to Carsten and the other guys here that are familiar with different rebreather systems. Regards, Brent Hartwig From: bottomgun@mindspring.com To: personal_submersibles@psubs.org Subject: RE: [PSUBS-MAILIST] Compression Time Tables for Wet Exit Date: Sun, 6 Jul 2008 22:32:30 -0400 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
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