Re: [PSUBS-MAILIST] Deep Escape Ascents (was Scuttle valve)

[SJSVOB@aol.com]

> could someone check some decomp charts and advise what is the maximum depth you could free ascend from (bounce dive?) and not suffer the bends?  The charts in this case assume that the diver has descended to this depth, absorbing nitrogen as they go.  They don't calculate rapid pressurisation from 1ATM to ambient without ensuing travel time, so the value would likely be VERY conservative.  Maximum bailout depth without surface support (hyperbaric chamber) may well be fatal from well above the 300 foot record.


I'm not aware of any charts developed for bounce diving but I'm no expert.  ZPlan is a utility available for free over the web for technical divers to plan dives.  Out of curiosity I plugged in a time of 1 minute spent at 300 feet breathing normal air and I got the result I included below.  I do not think this is very useful/applicable to psubbers, and I think it suffers from the problems you stated.   I'm just posting it for anyone who is curious. 

You all are probably already aware that: Breathing pressurized air at 300 feet is problematic (Nitrogen Narcosis and Oxygen Toxicity), which is why sport divers don't (or rather shouldn't) go that deep.    At 300 feet on air the PPO2 is 2.116.  Over a 1.6 partial pressure of oxygen (PPO2) the risk of oxygen toxicity "greatly increases" (I do not know how risky exactly this is for a psubber in a dire circumstance breathing it only temporarily).   Also what about the danger of sparks, (created by flooding electrical equipment), in a high pressure environment creating a fire?

Am wondering: How about a drouge device to slow ascent, only to be deployed when the escaping mariner, with an escape hood, reaches shallower depths?


               Zplan v1.03                     
  (c) Copyright 1997-98, William M. Smithers    

                DIVE PLAN                      

Waypoint  at  300ft for   1:00 (6) on Air,        PPO2 2.116, END 300
Deep Stop at  240ft for   0:20 (7) on Air,        PPO2 1.735, END 240
Deep Stop at  230ft for   0:20 (7) on Air,        PPO2 1.671, END 230
Deep Stop at  220ft for   0:20 (8) on Air,        PPO2 1.608, END 220
Deep Stop at  210ft for   0:20 (8) on Air,        PPO2 1.544, END 210
Deep Stop at  200ft for   0:20 (9) on Air,        PPO2 1.481, END 200
Deep Stop at  190ft for   0:20 (9) on Air,        PPO2 1.417, END 190
Deep Stop at  180ft for   0:20 (9) on Air,        PPO2 1.354, END 180
Deep Stop at  170ft for   0:20 (10) on Air,        PPO2 1.290, END 170
Deep Stop at  160ft for   0:20 (10) on Air,        PPO2 1.227, END 160
Deep Stop at  160ft for   0:20 (11) on Air,        PPO2 1.227, END 160
Deep Stop at  140ft for   0:20 (11) on Air,        PPO2 1.100, END 140
Deep Stop at  130ft for   0:20 (11) on Air,        PPO2 1.036, END 130
Deep Stop at  120ft for   0:20 (12) on Air,        PPO2 0.972, END 120
Deep Stop at  120ft for   0:20 (12) on Air,        PPO2 0.972, END 120
Deep Stop at  100ft for   0:20 (13) on Air,        PPO2 0.845, END 100
Deep Stop at  90ft for   0:20 (13) on Air,        PPO2 0.782, END 90
Deep Stop at  80ft for   0:20 (14) on Air,        PPO2 0.718, END 80
Deep Stop at  70ft for   0:20 (14) on Air,        PPO2 0.655, END 70
Deep Stop at  60ft for   0:20 (14) on Air,        PPO2 0.591, END 60
Deep Stop at  50ft for   0:20 (15) on Air,        PPO2 0.528, END 50
Deep Stop at  50ft for   0:20 (15) on Air,        PPO2 0.528, END 50
Deep Stop at  30ft for   0:20 (16) on Air,        PPO2 0.401, END 30
Norm Stop at  20ft for   3:00 (19) on Air,        PPO2 0.337, END 20
Norm Stop at  10ft for   8:00 (26) on Air,        PPO2 0.274, END 10

TOTAL DECO TIME: 18 minutes.
DIVE RUN TIME: 26 minutes.
CNS Total: 136.9%
OTU's: 20

Time to Fly: 1.0 Hours

62.8Cu ft of 21.0% consumed.
62.8Cu ft total open circuit gas consumed.