On Fri, 1 Nov 2002 08:03:45 -0500, "Sean Patrick Daly" <[EMAIL PROTECTED]> wrote:
>I don't know about anyone else, but I'm under the impression that the higher >you go, the colder you get. So I guess the real question is... What is going >to happen to the H2O2 above say... 50,000+ feet? Will the engine restart at >those temperatures? Will there ever be a need to? Oh yes. Higher, actually...but if you're coming back from orbit in a VTVL, and you haven't got the engines lit by the time you're down to 50,000 feet, then you will have a burning desire, excuse the pun, to get them lit *right now*. If you're not coming back from orbit, you probably don't have to worry much about peroxide temperature. You haven't been up more than 45 minutes. If you're doing a low suborbital, you definitely don't have to worry about peroxide temperature. As Mitch put it, "There are much better ways of hovering than standing on a pillar of fire." Every second those engines are running is near and dear to your wallet, so you're going to want to keep the flight as short as you can. 15 minutes is a good sounding rocket flight. >Personally, I would be a little concerned if I was in a craft that was >powered by a propulsion system only designed to operate on the ground at or >near sea level. I guess you haven't seen Dave Masten drooling over aerospikes, then. :-) Automatic altitude compensation. Automatic temperature compensation, too, come to think of it. Colder air is denser, and ambient density is what an aerospike cares about. >I guess that none of this would matter if the engine will >only be fired for one long continuous burn... But, if there were ever a need >to restart the engine once it's been off for 5 minutes at well below >freezing temperatures, I'd have some sort of heating system on the tank. Or you'd have run the numbers on heat loss given the thermal mass of the peroxide, the tank, and the vehicle, and the ambient environment, and concluded that you don't need to heat the tank. We ran a similar exercise here for Armadillo's life support system. We concluded that they didn't need one. The flight is so short, and the cabin so large, that CO2 levels won't rise to uncomfortable levels during the flight even if they don't scrub the air. We also determined that dumping the air overboard and replenishing it from on board tanks was simpler than scrubbing it, since they're going to bring the tanks along anyway, for redundancy. -R -- "...And the last thing I remember is asking, 'What could go wrong?'" _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
