At 10:58 AM 06/06/2002, [EMAIL PROTECTED] wrote:

>My key concern is having the regulator on the high pressure tank
>freeze up if we used standard air from a scuba-type compressor.
>In other words, is the 'dry air' that is OK for scuba applications,
>sufficient enough to avoid freezing during *very fast* pressurant
>tank blowdowns?

Flow rate isn't that much different, which surprised me.  We'll be 
pressuring at about 1.5 liters/sec, or 90 liters/min, which is a lot.  But, 
a SCUBA regulator has to deliver air at the rate the diver inhales, and a 
diver working hard can inhale at 60 liters/min.  He probably shouldn't, but 
limiting his air supply when he's working hard is a good way to get a 
panicked diver (the technical term for panicked diver is "corpse"), so the 
regulator will be capable of a good deal more than he is.

We would be OK with a SCUBA compressor.  We'd be even more OK getting our 
tanks refilled at a SCUBA shop; some shops charge $10/tank, and others 
don't charge anything (they're hoping you'll by their dive gear - since we 
won't be buying dive gear, we should make a token payment even if it's 
free).  Let someone else worry about the maintenance on the compressor.

>I don't have the same concern for the main tank,
>as the thermal mass of the peroxide should prevent any freezing.

Oh yeah.  Open eyes, engage brain...

>Besides, the adiabatic heating should cause the N2/air going into
>the main tank to get warmer than ambient.

That's at prop tank pressurization, isn't it?  And that assumes the prop 
tank isn't full of propellant.  I think the prop tank will cool to near 
ambient between pressurization and firing.  Of course, as our procedures 
get better, that becomes less and less true...

-R

--
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PETE     -    People for the Ethical Treatment of Electrons
Randall Clague                                [EMAIL PROTECTED]

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