🚀 go-pugleaf

In <C025yp.A1.1@cs.cmu.edu> roberts@cmr.ncsl.nist.gov (John Roberts) writes:

>There's a very good argument for multistage rockets - it makes the mass
>ratio much simpler to manage (see some of the books by Willy Ley).

There's also a very good argument for multistage airplanes -- it makes
the mass ratio simpler to manage.

However, while multistage airplanes have been builting and tested
in trans-Atlantic service, airplane manufacturers quickly realized
that the key to producing a successing airliner was not minimizing
mass ratio, but minimizing operating costs.

In a competitive market, a launcher with a large mass ratio and
low operating costs will beat a launcher with small mass ratio
and high operating costs every time.

Achieving this requires careful attention to sound engineering
principles including, above all, KISS -- Keep It Simple, Stupid. 
What's needed is a simple, reliable design, without bells, whistles,
or stages.


>Unfortunately, it also adds to the complexity and reliability problems of
>the launcher, which is why we'd like to go to SSTO if we can. Thanks to
>advances in technology, it may now be practical, and DC will be a great
>breakthrough if it works. 

Advances in technology, perhaps, but hardly recent advances.  The old
Saturn S-IVB stage could've been turned into a SSTO launcher, with a
payload the size of a Gemini spacecraft.  The "unattainable mass ratio"
is nothing more than an aerospace legend.


>But that doesn't mean designers were foolish to
>use multistage systems in the past - and some applications, such as direct
>flight to the moon without refueling, will probably remain unattainable by
>SSTO for a long time.

Actually, SSTM (you can hardly call it SSTO :-) would be quite attainable
given a nuclear rocket engine with a sufficiently high thrust-to-weight
ratio.  Unfortunately, launching nuclear rockets from Earth was politically
unacceptable even before we had Captain Planet for Veep.