🚀 go-pugleaf

In article <BzC0s3.E60@bunyip.cc.uq.oz.au> scooper@kepler.physics.uq.oz.au (Steven Cooper) writes:
>Pardon my ignorance folks, but what is this DC thing?
>...Who is designing/building it? 

See some of the other recent postings for details.

>Now, I'm really confused about how you make an SSTO. As far as my meagre 
>understanding goes, the final velocity of a rocket is the exhaust velocity
>times the logarithm of the mass ratio.

That's correct, ignoring gravity losses and air friction and assuming
a standing start.  (Most of these assumptions can be rationalized by just
adjusting the desired final velocity a bit.)

>How easy is it to get 5 miles per second with a
>single stage? I thought that exhaust velocities were only about 3000 m/s 
>which would require a mass ratio of about 14. With payload and fuel for
>landing this sounds quite difficult.

It's a bit challenging but no longer looks that hard.  Modern exhaust
velocities are up around 4500m/s, if you're willing to accept the hassles
of working with liquid hydrogen.

Note that Atlas did it with a stage and a half -- dropping two engines
but nothing else -- in 1958.  Using 3000m/s exhaust velocity, too.

Even the shuttle isn't moving that fast at SRB burnout; the second stage
(main engines burning alone) does most of the work.  Gary Hudson claims
that if you deleted the SRBs and the orbiter, and just put six SSMEs
under the external tank, it could reach orbit (with a respectable payload)
as an SSTO expendable.

Making it reusable is somewhat harder.  But everyone who's studied the
technical details says it now looks feasible.
-- 
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  henry@zoo.toronto.edu  utzoo!henry