From: Portsmouth, UK
once the first person gets out of the escape hatch what keeps the water out of the inside of the submarine while the second and so forth escape?
The escape tower has hatches top and bottom. open Bottom hatch, person goes in. Shut bottom hatch. Equalise pressures (using LP air). Open top hatch. Close top hatch (from inside submarine. Drain tower. Repeat.
In a rush escape the bottom hatch is opened and the compartment flooded to above the level of the bottom hatch. The whole compartment is then pressurised to equalise outside sea pressure before the top hatch is opened. You duck under the bottom hatch and head straight up. This has the disadvantage of having people under pressure for a lot longer and introduces risks of the bends and CO2 poisoning.
Also found this:
Don't know what the requirement is today, but we did two 30' runs, one 60', and one 100'. These were free ascents. That is; wearing your best beachboy posing trunks (I suppose today it would be a pair of Speedoes), a stole (a sort of life jacket), and a nose clip. After the free ascents, we then made a "Suit" ascent from 100'.
A free ascent involved standing in a "pot" to the side of the tower (except for the 100', where it was done from a compartment at the base of the tower), the pot was then flooded to equalise the pressure and pop the hatch open. All the time that the pot was flooding, you had to hold your nose, and your mouth shut, and breath-out, reasonably hard to equalise the pressure against your ears. Thus reduce, or even negating a lot, and I mean a lot, of pain. Should you not be able to clear your ears, then the instructors would shove a load of "Otravine" up your snoz in the hope that it would then enable you to do so. Failing that, it was a case of "live with the pain son, it's not for long". Of course, if your eardrums went, then you really didn't need to worry about the pain anymore. The problem with that of course, was you could no longer hear the instructions being issued.
Back to the run. When pressure equalised, and ears cleared (or not), you would stick your bum out of the hatch (forgot to mention, we were also fitted with a belt, that had two straps hanging from the rear), the swimmers would grab the straps, pull you to the centre of the tank and let you go. The other thing here was, that you had to breath out in a steady stream all the way to the surface, otherwise you could go pop. This because at that depth you were at one atmosphere greater than on the surface, and therefore twice as much air in your lungs than necessary.
After the second 30', we would do the one 60', following the same format.
Should you still be alive, able to stand up, or walk in a straight line, it was on to the the 100' free ascent. This was conducted from the base of the tank, and you went out vertically, much as you would do in a real "Rush Escape" in either the fore, or after ends of a "real" (diesel) submarine.
Had you shown any signs of not following the instructions regarding breathing out, you would now be in a decompression chamber for the next week.
Finally it was the suit run. This time we were dressed up in an immersion suit, which covered your bonce, but they did at least provide a plastic window so you could witness your own demise. Underneath the hood you had your faithful nose clip on, to enable you to clear your ears. Instead of flooding an entire compartment, this time you were placed in a single man escape tower, and only this was flooded. The drawback with this was; that it flooded quicker, so you had to keep clearing your ears at what at the time, seemed like amazing speed. Once equalised, the lid opened, and out you would pop. The forward thinking "tank team" had this time fitted you with a sort of waste strop with a clip attached. So, once out of the tower, a swimmer would grab you, attach the clip the a length of steel wire which ran the entire length of the tower. The swimmer would then gesture for you to say something, usually on the lines of "bollox, let me go you bstd", and once done, he would do exactly that. This time you did not need to breath out, as your body was still at surface pressure. Once done, and all of your necessaries were still in the right place, you were done until five years hence.
"Grown ups are what's left when skool is finished."
"History started badly and hav been geting steadily worse."
- Nigel Molesworth.