I happened to read a good book about the loss of the Russian submarine inthe Barents Sea (the “KURSK”). Apparently, around 23 crew members survived the explosion that sank the sub-these crew members were all in the rear compartment. Now, the KURSK sank in 350 feet of water-can submariners escape from such a depth (and survive)? From what I understand, to get out of such a situation, you would have to:
-get into and escape hatch chamber.
-flood the chamber untill the air pressue inside equals the water pressure outside.
-open the escape hatch and float to the surface (exhaling all the way so your lungs don’t burst!)
Now, I’ve met sailors who have done this (in an escape tower tank). They say it is a terrifying experience, even in the safety of a training tank. For 23 scared russian sailors, in the blackness of 350 feet (and water at 34 degrees F), this would truly be terrible.
So, are submariners really going to try this? I imagine at the depths that subs are capable of , escape is probably not a feasible option.
Incidentally, the KURSK sailors were doomed: the propeller shafts on Russian subs leak-so water was probably up to the men’s waists when they died. I wondered why they didn’t move into the reactor room (it was walledby 5" steel bulkheads. probably they would have been fried by the radiation, but at least they would not have drowned.
All I can say is: I would not want to be a Russian submariner!
Would there not also be an issue with decompression if you actually managed to reach the surface, or would the brief time under pressure not have caused any Nitrogen to enter the blood?
Mangetout, I believe that exhaling during your ascent acts to force the nitrogen out of your body, thus avoiding decompression sickness. Even if that’s not correct, I’m sure even a bad case of the bends is worth not drowning to death.
Unless you are under pressure while still in the submarine, there shouldn’t be any issue with decompression sickness when returning to the surface. You would probably pop both eardrums, and probably drown before you made it to the surface, but if you lived, you would not get the bends.
Regards,
Shodan
Nah…you have two things to worry about when under pressure. Decompression sickness (the Bends) and air embolisms. Your lungs, with pressurized air in them, will expand as pressure decreases (rising to the surface) causing the air sacks in your lungs to pop releasing air into your blood stream. Not a good thing to have happen.
For the bends to occur you need to be breathing pressurized air for some time. This is what dive tables are for that scuba divers use. It tells them how much decompression time they need at what depths based upon the depth of the dive and the time of the dive. In the extreme, such as saturation diving where divers spend days a few hundred feet under water, the decompression time is measured in days. For most recreational purposes decompression times rarely exceed 5-10 minutes (you rise to a certain depth and just stay there for a few minutes). Exhaling all the way up from a dive will not prevent the bends whatsoever.
Air embolisms on the other hand can occur immediately. Your lungs air fairly weak things and can only handle a pressure differential of a few pounds. IIRC from my diving course the pressure difference from as little as five feet under water is more than your lungs can cope with. Don’t believe me? Stick a hose in your mouth and swim five feet under water (with someone holding the other end of the hose out of the water) and try to breathe. You won’t be able to at all and it doesn’t matter how wide the diameter of the hose is (it’s ok to try this…no issues with the bends or embolisms or anything…just try not to suck in any water when you attempt to breathe).
When rising from depth the embolism is the reason for exhaling all the way up. Needless to say when you are stuck far underwater breathing out all your air seems counterintuitive but you had better do it. When you think all your air is gone and you rise some more more air will seem to ‘magically’ appear in your lungs and come out.
All of that said submarines are NOT pressurized. If they were they would not be able to pop to the surface at will, pop the hatch and let the sailors off. Military submarines can raise and lower their depth at will and the sailors can walk out as they please when on the surface. The only thing I can guess is that to keep the sailor’s ribcage from being crushed they have to take a breath of pressurized air equalized to the surrounding sea pressure before leaving the submarine. In this case you most definitely want to exhale all the way up. Now that I think of it this is probably what the deal is. In this case however there is no issue with the bends…that one breath is nowhere near sifficient to saturate your blood with enough nitrogen to cause you any problems.
It should be noted that in the water temperature that the Kursk was in chances are it was preferrable to stay aboard the submarine than to try and escape. Without special protective gear to keep you warm in the water you will have less than 10 minutes to live in water that temperature. A rise from the depth of 350 feet is going to take you probably close to two minutes alone givng you a surface time to survive of maybe 8 minutes or less. Your rescuers had better be right there to pluck you out of the water when you pop up. If they are even a mile away (assuming they notice you immediately) they had better have some fairly fast boats in the water to come to your aid before you become a popsicle.
Actually in fairness you might make it. The 10 minute deal sends you into shock but theoretically you might actually survive much longer. If you have a floatation device that keeps your head out of the water you probably won’t drown when you lose consciousness (which you will). After that you might be revived after hours in the water. Chances aren’t great but is has actually happened. Some time ago a kid in Chicago fell through the ice and was actually underwater for over an hour (IIRC). Beyond hypothermia you’d drowning was a foregone conclusion. However, the cold water essentially put the kid into a sort of sci-fi like suspended animation…heart rate slowed dramatically and oxygen use was minimal. The kid was plucked from the water and successfully ressucitated. He lost some use of one of his hands due to cold damage but beyond that he made a full recovery.
That story is more a freak occurrence though than something you can count on…most people die in such circumstances. To leave the Kursk via escape hatch in that water you had better be pretty certain help is immediately above if you expect any real chance to survive. Of course if your air has run out or some other problem aboard the submarine makes your death imminent in the next 5 minutes or less you may as well take your shot at escaping…not much to lose at that point.
I don’t think this is necessary. An outward pressure difference will definitely rupture your lungs, but I think an inward pressure (external pressure) will only compress your lung and not cause any injury.
I’ve been out of town for the last few days, but couldn’t let a submarine thread go by without posting…
As has been posted, submarines are not pressurized. The sub’s internal air pressure is kept at or near atmospheric pressure.
With respect to the escape system used on U.S. subs, one thing to keep in mind is that the system is designed as an airlock. The idea is to get people out without flooding the rest of the boat. The basic idea is to: (1) undog and open the lower hatch; (2) enter the escape trunk; (3) shut and dog the lower hatch; (4) undog the upper hatch; (5) fill the escape trunk with water to about chest height; (6) open a high pressure air valve that will pressurize the escape trunk until the trunk pressure slightly exceeds the surrounding sea pressure; (7) swim up when the internal escape trunk pressure causes the upper hatch to pop open; and (8) ascend as quickly as possible, exhaling continuously. The upper hatch can then be remotely shut by personnel below, who can then open the lower hatch. Then repeat for the next group.
Some notes: Steps (6) to (8) need to be completed as quickly as possible. Every breath taken under pressure increases the amount of pressurized nitrogen being dissolved in the bloodstream. The idea is to minimize the time spent breathing pressurized air. We had tables that had maximum times to reach the surface from the time that the trunk was pressurized. Times for relatively shallow depths were in minutes. Times for deeper depths were in seconds. 
Since getting to the surface from a relatively deep depth in less than a minute was clearly impossible, the chances of experiencing possibly fatal complications during the ascent from such depths increased accordingly. We were also told that our eardrums would likely rupture during ascent.
In practice, we did not put much stock in the escape trunks. The scenarios in which they might be useful (we felt) were so limited so as to make them all but useless. Specifically, a sub would have to have a flooded compartment that would prevent her from making it to the surface, but this would have to happen in relatively shallow water. In other words, for “minor” uncontrolled flooding, the sub would just emergency blow to the surface, and abandon ship in lifeboats if necessary. Major flooding would take a sub to the bottom, and since the average depth of the oceans is about 12,000 feet, the sub will eventually reach crush depth and implode.
We used to say that the escape trunks were for “mommies and Senators.” 
(“You mean our boys don’t have any way of getting out of this tin can if it goes down?!”) That being said, the Kursk disaster has caused me, at least, to rethink this. That was exactly the type of situation in which an escape trunk could be used, though the angle she was at on the bottom might have made matters more difficult.
Technically, US boats do free ascent using the Steinke Hood system, which is basically an inflatable life jacket with a hood on it. This system is effective up to depths of 600 feet. I stumbled across this article the other day, and it explains the new rescue system. As far as the training was concerned, my class had a blast. Of course it was a serious endeavor, but man, poppin’ out of the trunk and travelling 60 feet straight up in 5 seconds was too cool!!!
BF,
ex-bubblehead and steinke hood maintenance tech
I have thought about this too.
If water leaking into the sub was REPLACING air that leaked out, they would not necessarily be pressurized, so no bends.
If the water leaking in pressurized the existing air, and no air leaked out they could very well suffer the bends upon surfacing.
I just finished reading the book, The Terrible Hours by Peter Maas. It is about the 1939 rescue of the non-drowned portion of the crew of the submarine Squalus which had sank in 250 feet of water. I really enjoyed it, and related to the OP it covers the difficulties involved with a submarine rescue. From the Amazon site:
To add a little bit to what has been said, there are three and possibly four problems facing a free acent
[list=1]
[li]The bends,as explained in prior posts. The no decompession limit gets less and the pressure (depth) increases. Now the bends do not always = fatal, by they can be way serious. (of course staying in the sub does = fatal you do the math)[/li][li]Not exhaling enough causing an embolism (this is actually easier than it sounds) you blow out air as fast as you can. As the pressure is decreasing the air in your lungs is expanding, so you never run out. The deepest I have ever free acended was about 75 feet when I had equipment failure.[/li][li]Hypothermia / Shock from the water temp when exposed it in the escape trunk. Ever jumped in to a pool of icey water?[/li][li]Nitrogen narcosis [This effects SCUBA divers, not sure about someone doing a sub escape] for a diver each 50 feet of depth is like drinking a martini. Divers have been known to offer their regulators to passing fish “because he looked like he needed some air” If the sub were deep enough this might make the sailor forget what he should be doing. Not good.[/li][/list=1]