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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space
Subject: Re: Elevators
Message-ID: <3239@utzoo.UUCP>
Date: Thu, 6-Oct-83 19:08:59 EDT
Article-I.D.: utzoo.3239
Posted: Thu Oct  6 19:08:59 1983
Date-Received: Thu, 6-Oct-83 19:08:59 EDT
References: <12246@sri-arpa.UUCP>
Organization: U of Toronto Zoology
Lines: 20

Unfortunately, starting from 200 miles up helps you very little
when it comes to achieving orbit.  It helps some, but most of the
fuel burned by, say, a Shuttle, goes into velocity rather than
height.  17000 mph takes a lot of rocket.  You definitely want
to take the elevator all the way up to Clarke ("geostationary")
orbit, so that you are at orbital velocity when you let go.

As for the time taken, nobody in his right mind has suggested
that the elevators move as slowly as 100 mph.  Clarke had his
"production" elevator cars highly supersonic even while still
within the atmosphere.  Given enough power to drive it, a 1000-mph
elevator should be straightforward with only minimal upgrades
to current technology.  (The Space Studies Institute's prototype
mass drivers have already demonstrated electromagnetic propulsion
at far higher accelerations than a passenger system would ever
need -- and the latest one is self-centering, so no guide rails
or suspension systems are needed.)
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry