On Fri, 26 Sep 2003, Thomas McNeill wrote:
> ...the correct DeltaV you either need a very high Isp or
> a very [high] mass ratio, am I correct?
Correct... or some reasonable combination thereof. You need an excellent
mass ratio unless your Isp is most unreasonably high.
> Anyone here an advocate for using H2O2 on a SSTO craft?
Oh, I think one or two such folks could be found here. :-) It has
advantages (high density, room temperature) and disadvantages (not the
hottest of oxidizers). The idea is challenging but not ridiculous.
> I continue to calculate very high G forces.
> Anyone have any good ideas on how to accomplish this
> without high Gs?
I think you're assuming constant thrust, which is a bad assumption for
most any flavor of SSTO. Given the necessary mass ratio, it's pretty much
essential to have some sort of deep-throttling capability, so thrust near
the end of ascent is very much reduced from thrust at takeoff. One good
way to do this, given the difficulties of deep throttling for rocket
engines, is to have multiple engines and shut some of them down.
Not even a LOX/LH2 SSTO can run at constant thrust, if only because the
high Gs impose too much load on the structures, and the situation is even
worse for lower-Isp combinations that need higher mass ratios.
Henry Spencer
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