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From: REM%MIT-MC@sri-unix.UUCP
Newsgroups: net.space
Subject: space elevators
Message-ID: <12817@sri-arpa.UUCP>
Date: Thu, 20-Oct-83 07:35:00 EDT
Article-I.D.: sri-arpa.12817
Posted: Thu Oct 20 07:35:00 1983
Date-Received: Wed, 26-Oct-83 02:18:47 EDT
Lines: 18

From:  Robert Elton Maas <REM @ MIT-MC>

Yes the energy actually applied to the rocket payload would be the
same with an elevator. There are two major differences:
 (1) Rockets are very inefficient, most of the fuel is wasted in the
exhaust, very little is applied to knetic energy of the rising rocket.
 (2) Much of the energy actually applied to the body of a rocket is
spent lifting fuel and rocket engines rather than payload. Typically
the whole rocket at launch weighs an order of magnitude more
than the payload, so even with a perfect rocket you'd get only about
10% overall efficiency.

The combination of these two inefficiencies means very very little of
the energy in the rocket fuel actually gets applied to the payload.
With electric elevators you get nearly 100% efficiency from
electricity to payload-motion, and the way you make the electricity in
the first place is highly efficient too, much more efficient than the
burning of rocket fuel is.