Re: Solar sailing

From: Adrian Tymes (
Date: Sat Mar 03 2001 - 00:29:04 MST

Spike Jones wrote:
> In principle this scheme would provide thrust, but its not clear
> the advantage of having the propellant in a solid form to start with.
> Why not just use the standard liquid fuel with the energy to drive
> the propellant stored in the propellant itself?

Umm...miscommunication. I meant as in a railgun or coilgun - where
the propellant is (hopefully!) non-explosive - in order to get higher
exhaust velocity, and thus a lower mass fraction. (Checking a bit into
this, I'd probably want coilgun, since that's simpler and doesn't wear
down its rails during normal operation. Simple good. No-self-hurt
good. Of course, that's assuming I can get the necessary power...but
then, I was already looking into plasma rockets, which have similar
concerns in that regard.)

> By now you have likely heard the sad news about the X33 cancellation.
> Altho I am disappointed, I cannot say I am surprised. I never had much
> hope that the Venture Star or the X34 would go. At conferences of
> the Society of Aerospace Weight Engineers, a society to which I have
> belonged for about 16 years, side sessions would often form to discuss
> single stage to orbit. I attended these but often felt they lose sight of
> the
> ultimate goal, which is cheap access to space. The SSTO guys seem to
> think the ultimate goal is SSTO. My observation only, but it leads me
> to post my own slogan, which should be my sig line:
> Anything that can be done with one stage can be done better with two. spike

I heard they're having a really hard time getting non-final stages to
be reused. Which means they have to remanufacture the lower stages.
No prob if the lower stages were cheap, but they're not. That's the
main point of SSTO: if your entire vehicle is designed for reuse, then
you can spread the cost of the entire vehicle over multiple launches,
thus you get cheap per-launch.

Now, that being said, I've seen the same problem you identify. Counter
(or, source of) problem: how do you identify "this design objective
leads to cheapness" where there's little obvious connection between
cost and engineering objectives? (It seems that one could do a cost
breakdown of current examples - specifically the shuttle - to find out
what not to do again. Unless that data is has already been obtained,
but then, how would one gain access to it?)

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