Brent,
The bubble in a K-250 will still trap an air bubble.
A variety of methods have been experimented at great length over the years. The method of rapid flooding with a “blow & go” ascent directly to the surface has been determined to have the most success. Anytime to start complicating it, failure results as you are already in a very stressful situation. I have read numerous accident accounts and met with several people who have had direct knowledge of actual accidents. As several people have told you in the past…REMEMBER KISS, especially in emergencies. You are making the issue way to complicated. See my presentation when it becomes available as all of these issues are covered. The K-250 doesn’t have room for all the equipment and gas you want to add let alone the freeboard.
This year’s presentation will be a hands-on workshop on how to get a stranded hull back to the surface rapidly so as to rescue the operator at the surface. Unfortunately S.S. Excrutiator will not be in attendance to practice escape drills but hoping Steve’s Nemrod will make it into the States and to the Conference so that we can use it for a real salvage using lift bags. Need to get back to putting the finishing touches on the presentation and get materials shipped to Castine.
R/Jay
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Tuesday, July 08, 2008 12:53 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Compression Time Tables for Wet Exit
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