On Tue, 28 Jan 2003 14:08:54 -0800, David Weinshenker <[EMAIL PROTECTED]> wrote:
>Hmm... I presume those specific impulses should be "km/sec" rather than >"m/sec"? They seemed on the high side until I noted the expansion conditions >they were determined at: 1000 -> 0.2 psia, or 5000:1 pressure ratio...! > >(So that's how to get 1.88 km/sec out of >H2O2 monoprop and 3.73 km/sec out of LOX-RP1!) > >Since the subject of the paper was propulsion for planetary missions (which will >fly in vacuum), I suppose calculating for such expansion ratios may be appropriate... >are they within reach of practical nozzles? I don't see why not. An expansion ratio of 5000 is a diameter ratio of about 71. That gives you a 2.84 meter nozzle for a 4 cm throat. That's doable. It's a small engine, but planetary missions don't need high thrust as much as they need high efficiency. Still, that's a huge nozzle. I don't know enough about nozzle design to say for sure, but I have a feeling that 5000:1 is beyond the point of maximum delta-v, and that a smaller nozzle would save more in mass fraction than it cost in Isp. -R -- "We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true." -- Robert Wilensky, UC Berkeley _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
