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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.space
Subject: Re: Tethered Generators
Message-ID: <40@ssc-vax.UUCP>
Date: Wed, 8-Aug-84 11:58:43 EDT
Article-I.D.: ssc-vax.40
Posted: Wed Aug  8 11:58:43 1984
Date-Received: Fri, 10-Aug-84 02:00:58 EDT
References: <671@ihuxt.UUCP>
Organization: Boeing Aerospace, Seattle
Lines: 26

[7 August 1984]

     The way you make up frictional drag losses in LEO with a conductive
tether is to use a solar array to force current up the tether.  By reversing
the 'generator effect', you now have a motor.  The system now gains
orbital energy at the expense of electricity.

     Force on a current-carrying wire in a magnetic field is

          IL x B
 
where I=current in Amperes, L=length of wire(meters),x= cross product (math
function that tells which way force is directed), and B is magnetic field in
Teslas.  In order to have a one way current, you have to collect electrons
at one end (a large sheet of aluminum), and get rid of them at the other
(an electron gun).  Losses in the system are parasitic power to run the
electron gun (10-20%), and I*I*R resistance losses in the wire.

     Although this propulsion system only works well in the ionosphere,
it gets lots better thrust per watt than ion propulsion, and consumes
no fuel to boot.  It can also be scaled arbitrarily small, i.e.
1 Ampere, 100 meter wire, television type electron gun, = 1/300 newton.

Dani Eder / Boeing Aerospace Company / ssc-vax!eder