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From: SASW%MIT-MC@sri-unix.UUCP
Newsgroups: net.space
Subject: space elevators
Message-ID: <12845@sri-arpa.UUCP>
Date: Thu, 27-Oct-83 02:15:00 EDT
Article-I.D.: sri-arpa.12845
Posted: Thu Oct 27 02:15:00 1983
Date-Received: Wed, 26-Oct-83 01:35:18 EDT
Lines: 23

From:  Steven A. Swernofsky <SASW @ MIT-MC>

Seth,

I think your physical description of "space elevators" leaves out some
important facts, but I am not sure if this is reflected in your energy
equations.

1.  The energy expended is NOT the same as a rocket launch.  A rocket
launch must expend energy to carry the payload to orbit and more energy
to carry the energy-to-carry-the-payload along with the payload.  An
elevator can carry the latter in the elevator shaft.  Thus, the space
elevator is more efficient in carrying things to orbit.

2.  The energy expended is "stored" in the payload's new position in the
Earth's gravity well, and can be recovered.  The object can be driven
DOWN the elevator, generating energy via flywheels or electromagnetic
generators.  The structure of the elevator makes this possible, where a
rocket-based means of propulsion would not.  In fact, a space elevator
can be (ideally) driven completely by energy recovered from objects
"dropped" from deep space or even lunar orbit.

-- Steve