Randall Clague wrote: > > Hey Doug, > > There's been some discussion on a sublist about using compressed air for a > pressurant, as long as we're doing monoprop. The issue of humidity came up... > > > > Since the air runs straight through the compressor and doesn't sit > > > in a storage tank, the air will be warm coming from it. Indeed, > > > that's why you see the cooling coils on the high pressure side, to > > > limit the temperature rise. At least, that's my understanding. > > > > Sure. But when it reaches our pressure vessel, it will still contain > >some water vapor. Then when we use that air to pressurize our fuel tank, > >some expansion and cooling will take place. There's at least the > >possibility of freezing, right? > > > > Am I missing something here? > > ...and I thought, hm, we have a professional rocket plumber right here on > the list; let's ask him. > > What say ye? How much of a problem is water vapor in compressed air used > as rocket pressurant? > > Thanks, > > -R
If it's dry enough to be used in a scuba bottle, it should be dry enough to be used to pressurize H2O2. The only time I've used compressed air was on the teacart long ago, and that was used on... water (the separate cooling loop). Just make *damn* sure that it's oil-free air- I suggest at least two stages of activated charcoal filtering after the compressor, or better yet, have your bottles filled by a dive shop- breathing air is oil-free. The compressor we use has two particle bed filters about a liter volume each, originally one with charcoal, the other with Drierite dessicant. For helium reclaim, I refilled both beds with charcoal, and added an external charcoal filter and ten micron particle filter. After every pumping job, I remove that filter, connect it to a Sargeant-Welch vacuum pump, and heat it to about 100 C for an hour or two to desorb everything. I need to figure out a way to regenerate the large filters in place, but until then I just replace their fillings every ten runs or so. My main conclusion is, for a small scale, it will be a lot cheaper to buy air or nitrogen than to pump it *and ensure the quality* yourself. Doug _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
