Randall Clague wrote: > > At 03:07 PM 06/06/2002, [EMAIL PROTECTED] wrote: > > >The point of this exploration is to find a way to refill the pressurant > >tanks *in* the field. > > Ah. Well, we could probably live with the limitations and uncertainties of > doing it ourselves. It would be a nice backup to pre-filled bottles. But > $800 for a backup is way steep.
Seems like the best way is going to be to have some 6000 psi bottles and a valve manifold, and cascade-load the flight pressurant: Start by filling the flight tank from bottle #1... for the first several fills, that will get it up to 4500 psi; once bottle #1 drops below 4500 psi, bottle #2 can be used to top it up. When bottle #1 gets empty, have it refilled to 6000 psi and use it for #2, and move the former bottle #2 to the #1 station to use the rest of the gas in it. (Since the flight tank will be much smaller than the source bottles, if #1 starts at 6000 psi then the flight tank can be filled from it a number of times before its pressure drops below 4500 psi and some gas must be taken from #2.) For vehicles in the KISS/Spike category, it's going to be some while before our flight rate is so intensive that we'll need anything more than such a setup - which we may well be able to manifest for less tha the cost of a scuba compressor, and which will allow us to use commercial gases of known quality. Hmmm.... IIRC, the liquid density of cryo gases such as nitrogen and oxygen is about 1000 times their gas density at 1 atm. ... so if LN2 were sealed in a full tank and then allowed to warm to ambient, the tank would then contain gaseous nitrogen at about 1000 atm. (15000 psi). Of course, in order to use this process as a safe source of high- pressure gas, one would need valves and tankage that would withstand this pressure with a reasonable safety factor (over the entire temperature range in question - which would require materials not subject to low-temp embrittlement)! -dave w _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
