Re: Impractical Spaceflight
Wed, 19 Aug 1998 08:37:52 -0700 (PDT)

Philip Witham [] wrote:
>NASA has lost all credibility regarding practicality.

Uh, this is the aeronautical side of NASA, who've done quite a lot for improving efficiency of aircraft in the last few decades. And the question was whether multi-stage winged vehicles were practical; clearly they think it's a practical proposition and we'll find out soon enough when they try it.

>All SSTO concepts and projects I've heard of have mass ratios (launch mass
> to payload) of around 100:1 in their theoretical fully developed form.

So (approximately) does the shuttle, and some other launch vehicles; and Roton claims 7,000lbs payload for a <400,000lb launch mass, say 55:1. The shuttle's what, 2000 tons with a 30 ton payload? 70:1?

> None I've heard of are even slated to carry any payload in their
> early forms, only after a later ($billions and years later) full scale
> version will that last 1% of performance margin needed to carry payload
> show up.

Uh, Roton, Skylon, Kistler's SSTO design before they canned it, etc, etc. I don't know of any SSTO outside the government that's not supposed to be operational very quickly. As far as I'm aware the first Roton is supposed to carry 7,000lbs to orbit after initial testing.

> This is welfare for aerospace contractors.

Uh, this is private funding for companies building spacecraft.

> Contrast that to the 30:1 mass
> ratio for a small (100,000 lb to LEO) two stage re-useable Truax style
> booster made of maraging steel.

3% if the design works. Or 0.3% when you consider that you can't put more than one satellite on top in case it blows up. Compared to around 2% if Roton works, and no staging or recovery to pay for.

>Gary Hudson did. He advocated it for years in an SSTO booster.

In that case he isn't as smart as I thought, though that may have been back in the days when there weren't as many alternatives.

>Yes, in steady, level, subsonic flight they transfer jet fuel very
>carefully, with a person at the controls at either end. Transferring
>LOX during accelerating, vertical, perhaps trans-or-supersonic rocket
>flight was what one concept proposed.

Uh, which one? The only such proposal I know of was Black Horse, which transferred hydrogen peroxide in, you guessed it, steady, level subsonic flight.