Re: [PSUBS-MAILIST] Sgt. Peppers O2 consumption rate question.

[MerlinSub@t-online.de (Carsten Standfuß)]

> Captain Nemo schrieb:
> 
> Carsten,
> 
> Approximately how long will 20 cubic feet of oxygen sustain you in
> your SGT. PEPPERS submarine, using an O2 replenishing / CO2 scrubbing
> life support system?  (A general estimation based on average
> consumption rate, temperature, and such will suffice.)
> 
> Thanks!
> Pat

Hi Pat .. I do not like cubic feet.. 

3rth roots of 20 cubic feet = a cubic block of 2,71 feet length, beam
and high
, with one feet is 0,3048 m 

2,71 x 0,3048 = 0,827 m 

0,827 m x 0,8327 x 0,827 m should be the equal of 20 cubic feet
= 0,566 cubi meter or 566 liter  (Hope thats right..)

stored by a pressure of 225 bar = 566/225 get a 2,47 Liter bottle

With 3,7854 Liter = one gallon it should be right a 

 2,47 / 3,79 = 0,65 Gallon bottle.

With a "You need at least 0,25 Liter/minute O2 each person"

566/ 0,25 = 2264 Minutes  divided by 60 Minutes = 37,73 hours

One day, one night, another day and the game is over. 

Acording to the rules : 
"For a one person sub it should be 
72 hours x 60 minutes x 0,25 Liters = 1080 Liters
1080 divided by a storage pressure of 220 bar = 4,9 Liters
4,9 divided by two groups = 2,5 Liter each bottle. " 

The scrubber question is more difficult and depents on 
the material you use. You will find some figures if you 
look in the internet for "Rebreather"  - I remember I found
some results the Royal Navy find out by using the "Buddy Inspiration"
with - I think - sodaline. I will look again for the figure and 
told the result to the Group. 

The CO2 absorber depents on the used material but the general rules are
: 
- CO2 partial pressure should be between 0,005 bar - 0,01 bar each time.
- CO2 production of each person should be calculate with 20 Liter/hour
  for each person at 20°C and 1 bar atmosphere. 
- At the end of the O2 run time the CO2 pressure should be under 0,02
bar inside the vessel. 

Sgt.Peppers use a pure O2 closed cycle rebreather made in russia for 
fire fighting purpose on ships. Works about 4 hours somebody
estimate to me - but according to the small O2 bottle 
it should be (0,7 L x 200 bar = 140 l / 0,25 L/min = 560 Min / 60 = 9,3
hours)
But the scrubber box is not very big - maybe 1,5 Liters. 

Normaly the free air inside my sub works for a maximium of 40 minutes
(starting strong  headeges) - so most dives are just 20 minutes 
without using the rebreather to save absorber and 02. 
Nobody will fill a russian 02 bottle made in 1965 here.. 
(thats is a private mail..). 

The two 4 Liter air-pressure bottles gives me additional 
1 hour but raise the air pressure inside to maximal : 
4 x 225 = 900 Liter, inside cabin free space 
about 400 liters , so 900/400 = 2,25 bar or equal a dive deep
of 22,5 meter or 74 feet.  

Hope helps a little - keep me inform if you get the 
scrubber consumtion figure for different materials out. 

Hope to send new pictures at the end of this week. 

Carsten