Re: RES: [PSUBS-MAILIST] Ambient pressure design considerations

[NeophyteSG@aol.com]

In a message dated 11/15/03 4:04:24 AM Pacific Standard Time, jorloujr@uol.com.br writes:

I'm afraid you're taking the wrong track.

Sadly, it would not be the first time but I don't think so this time.  I had to sit with it a while, go back and really look at rebreather principles again, go to the SportSub site to make sure it was the psub I had pictured in my mind, etc.  So, here's my attempt to explain where my brain took me.

 

"...every breath you expel in the SportSub is also expelled ..." This is not so. First off, you must analyse the whole breathing cycle and not only part of it.

 

Think about this: "...the only real difference...is that you have on the order of ... of air as a buffer". It's a huge difference. The buffer is the single most important thing in a rebreather, that's what makes rebreathing possible !

I'll see you a buffer and raise you a CO2 scrubber. :)  The SportSub doesn't have one because its inflow/exhaust rate is sufficient to avoid CO2 toxicity ... closer to a *really* big diving helmet or a diving bell than to a rebreather.  Yes, you do "rebreath" part of your breathing mixture but so do those who do 1-atm and surface every hour or so, and neither are "rebreather" systems.  The SportSub probably has a lower consumption rate than traditional Scuba systems, but that minimum necessary inflow rate is still governed by passenger CO2 production rates.  Even a semi-closed circuit would be leaps and bounds more efficient, much less a closed circuit system ... by and large due to the presence of a CO2 scrubber.

 

Make sense?  If I'm still wandering down the wrong track now's the time to convince me before I get lost! :)

 

Warm Regards

Shawn

 

 

*****

"To see a World in a Grain of Sand
And a Heaven in a Wild Flower,
Hold Infinity in the palm of your hand
And Eternity in an hour."

-- Auguries of Innocence, William Blake, ca 1803