Re: [PSUBS-MAILIST] life support method?

["Captain Nemo" <vulcania@interpac.net>]

----- Original Message -----
From: <VBra676539@aol.com>
To: <personal_submersibles@psubs.org>
Sent: Friday, August 04, 2000 2:25 PM
Subject: Re: [PSUBS-MAILIST] life support method?


> Al and all,
>
> Which is why two-thirds of the sub operators in the world were and are
quite content to have a dependable pair of 02 meters and a good barometer.
That pressure change from C02 buildup is pretty dependable. Set the
barometer to zero after closing the hatch then turn the scrubber on for 15
minutes or so out of the hour to when you get a couple of inches of
pressure. Simple as pie.
>
> Vance
>

Hmmm, interesting...

This is sort of like what I was doing, but I was operating on calculated
estimates of O2 consumption, without the benefit of gauges.

I was leaving my homemade O2 scrubber on all the time because I thought I
had to.  Noisy!  The fan was the 12-volt "heater-defroster blower" ripped
out from the under-dash of my '66 Chevy Sportvan.  The housing was
scratch-built.  The duct was a section of that flexible coiled stuff (like
what's probably coming out of the back of your laundry dryer) containing a
gym sock full of SODASORB pellets.  In addition to this, I had two small
axial-flow cabinet-cooling fans fore and aft, circulating the cabin
atmosphere.

When I valved in a blast (now THERE'S a scientific measurement of volume!)
of oxygen every so often,  I could feel the pressure differential on my
eardrums.

Admittedly, that was pretty fly-by-night; and I don't recommend others
follow my example;  but we knew we were only going to be doing short test
runs (our operational window was limited by high-tide water on the ramp
where we could launch and recover the sub to the trailer); and we did
successful "environmental endurance tests" on dry land for longer times than
we were going to need in the water; so, by the time we actually did our wet
proving tests, we were pretty confident the life support system was working
well enough to suit our needs.

But let me see if I understand this meter-barometer method now:  When the
barometer pressure builds, I run my scrubber until it zeros again, and that
will maintain the normal level of CO2 in the mix, right?

What, if any, effect will variations in cabin temperature have on the
barometer?  (On the surface, my little black Nautilus can get pretty hot;
underwater, she cools down pretty quick.)

And the O2 meters: this is a gauge that gives me a readout of O2 in the mix;
and I manually valve in oxygen as necessary to keep it at the correct
indicated percentage, right?

So basically: if I button up topside; check the barometer as a reference;
run the scrubber only enough to maintain barometric pressure; and add only
enough O2 to sustain a normal oxygen level with reference to the meter: I've
got a "normal air environment" with correct percentages of Nitrogen, Oxygen,
and CO2 in the mix, right?

(But PLEASE, don't mention PIE!  I'm on Day 54 of 84 of the BFL CHALLENGE
2000, and just thinking about that flaky, melts-in-your-mouth crust; those
cinnamon-laced baked apple slices; sweet sugar frosting lacing the top;
maybe crowned with whipped cream, a maraschino cherry, and some of those
chocolate sprinkles; plus a big scoop of vanilla (oh what the hell,
Neapolitan!!!) ice cream on the side; and a tall, cold glass of fresh whole
milk....(slobber...drool....AAARRRGGGHHH!!!!  Lynn!  Lock the 'fridge before
I hurt myself!)

;-)

Pat