Randall Clague wrote: > > At 07:58 PM 06/05/2002, The Silent Observer wrote: > > >Condensation is also a problem with SCUBA tanks; if they're allowed to > >drain off faster than the normal rate of breathing consumption there can > >be enough cooling effect to condense liquid water in the tank and > >promote corrosion. The analogy in the rocket would be condensation in > >the pressurant tank. > > I'm not too concerned about water in the pressurant per se - that's a well > known problem. What interests me is what effects we can expect from high > pressure and very fast blowdown. I'm specifically thinking about ice in > the lines. We saw this once before, when we did a procedures check after a > major mod of the static test hardware and associated checklist. When we > got to the firing section of the checklist, we tested the emergency vent > valve. It worked fine for a while, but around 200 psi it began to > sputter. Now how on Earth does a vent valve sputter? We're just dumping > nitrogen. > > So I waited for it to drop to 60 psi, which is what I put in my bicycle > tires, and stuck my hand in the nitrogen stream. It was cold. Well below > freezing. OK... It stopped for a second, than started back up suddenly, > as it had been doing. Only this time, when it started back up, it stung > the hell out of my hand. Hit my knuckle with something hard enough to > leave a white mark that persisted for several minutes. > > What the heck? There's nothing in there but nitrogen and a little bit of > water. What hit me? ...Oh! "Hey guys. This sputtering is going to be > normal during an emergency vent. And don't stick your hand in the gas > stream; there's ice in it." > > That was with many cc of water in the tank, but we were only coming down > from 450 psi or so. For the new system, we're looking at 4500 regulated to > 1000 blowing down to ambient in a few seconds.
Well, in that case, particularly if the tank had held at pressure for an extended time, the nitrogen was saturated with water in equilibrium with the water in the tank. Its dew point was room temp or above, so of course it froze when vented quickly. I dunno if you'd like spitting H2O2 ice out at high speed... -- Doug _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
