Re: [PSUBS-MAILIST] atmospheric control

To get bent, you'd need to be exposed beyond the no decompression dive limits. For ambient I think that's just a matter of watching the dive computer and don't exceed the no decompression limit. For bailing from a 1 atm the pressure exposure is going to be limited to when the hull starts to flood. So you've got to decide if you want to ride to the bottom and wait for rescue or bail.

I figure that unless you have an ascent line from the bottom to the surface that a controlled ascent would be very difficult to pull off. When I've gone diving it always takes some time for me to get the weights right for pieces of wet suite I'm wearing. I don't think both me and my partner would get it right, especially if were just in street cloths. I plan to have spare air bottles in the cabin, but once out I figure it's wait for your partner to clear the hatch and then just blow and go. Other that the sub being on the bottom and having an assent line, is there any good way for making a controlled ascent? I guess it could be done with overweighed BC's but I'm not sure it would be worth the snag hazards and a spare air bottle will not give you a lot of time so then a pony bottle is needed and now I've got to get that through the hatch.

So what would you do to bail from an ambient that's is on it way to the bottom?

Doug J
www.SubmarineBoat.com

"All animals are equal, but some animals are more equal than others"

Simon,

I gave a presentation at the PSUBS 2007 Conference on this subject. Argon is actually a very bad choice, while it is a good thermal insulator (approximately 1.5x air) it is highly narcotic at relatively shallow depths and its greater density while cause breathing issues. Pre-breathing oxygen can be a good idea if done before exposure to higher pressures. The best bet is to press down quickly (you will probably rupture your ear drums) and make a controlled ascent with a 40 cf bail out tank of air. This is the short answer.

R/Jay

Respectfully,

Jay K. Jeffries

Andros Is., Bahamas

As scarce as the truth is, the supply has always been in excess of the demand.

-Josh Billings

-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of SIMON WALKDEN
Sent: Friday, January 23, 2009 5:32 PM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] atmospheric control

Hopefully someone will have an answer to this; while pondering

atmospheric control, I was trying to figure out the best way to make

things as safe as possible. Hypothetically, let's say you're in an

ambient sub and need to make an emergency surfacing. Or, you're in a

1atm and need to abandon your vessel - whatever the circumstance, you

need to be exposed to great pressure differentials in a short space of

time.

Diving physiology stipulates that you will get the bends. So, why not

control the nitrogen levels in a submersible and replace it with, say,

argon? Are there any specific reasons people do not control the

breathing mix in submersibles the way they are in technical diving

(other than the risk being so minute)?

"Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum

immane mittam."

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