Re: To space without rockets ?

Mark Grant (
Tue, 28 Oct 1997 14:24:18 +0000

Berrie [] wrote:
> Ok. I see the problem. So you hardly save anything (fuel) by starting from
> 100 km.

Actually, if you're using a rocket that's not true. You save a
significant amount, both because you get above most of the air,
which eats up a large fraction of a rocket's fuel in drag, and
because you can use vacuum nozzles, which are several percent
more economical than sea-level nozzles. This (lifting the rocket
to 80,000 feet with zero velocity) was the approach that Kistler
Aerospace planned to use for their first 'SSTO' before they
switched to more traditional designs.

However, the fact remains that you're at most 25% of the way to
orbit. I have, though, read theoretical designs which launched
the payload vertically to a couple of hundred kilometers, then
'slowed it' into an orbiting space station using a mass-driver.
Sadly, building such a station would probably be almost as hard
as building a beanstalk, as the mass-driver had to be hundreds
of kilometers in length.