Chris Groves – What happens during an escape – pressure equalisation
Well, it’s realistic but what you’re not feeling is the pressure, the hyperbaric pressure that you need, because the pressure inside the submarine is normal atmospheric pressure basically, broadly, and then depending on what depth you’re at in a distressed submarine, depends on how much pressure is there outside, so at some stage when you get up into the Escape Tower, you shut the bottom bit of the Escape Tower.
In order to open the top bit of the Escape Tower, you’ve got to flood water into the Main Tower and you’ve got to equalise the pressure between the Tower and the outside pressure, which means that you’re pressurising a tin can that’s human being sized if you like, to the same pressure as the water is outside. You can’t do that slowly because that’s really dangerous, so you’ve got to do it pretty quick,
The reality of it is that you’re probably going to burst both eardrums. The pain in that is actually the pressure going onto the eardrums.
Once the eardrums are burst, you’ve got what the SETT Staff would call a ‘free flood head’ and there’s no pain on the eardrums any longer and your eardrums will fix and that happens really quite quickly ‘cos time under pressure is what gives you hyperbaric injuries, the bends and things like that.
So, what you want is the least time under pressure as you possibly can and then it’s the change in pressure which gives you issues, but all the time that your head is in air, you can carry on breathing normally ‘cos you’re breathing the air outside your lungs is the same pressure as the air that’s in your lungs, so you can just keep breathing that.
As soon as your head goes into water, you must keep blowing out, keep blowing out, keep blowing out because the air inside your lungs as you reduce the pressure, as you come shallower as you’re coming up through the water is expanding, so you just have to keep blowing out and keep blowing out and keep blowing out, even if you don’t think you can, you’ve just got to keep blowing out.
