🚀 go-pugleaf

In article <77146@ut-emx.uucp> johncobb@ut-emx.cc.utexas.edu (John W. Cobb)  
writes:
> There is a potential drop across the distance.
> So you are connecting a junction at two points and extracting electrical
> energy from it. It is a free lunch scenario. The energy is extracted
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> from the stored energy in the magnetic field structure of the earth.

Actually, no: TNSTAAFL :-)

The electrical energy produced by the tether DOES come from the shuttle's  
orbital motion. That J x B force you mention acts as a drag force on the  
tether as long as electrical power is taken from the tether. However, if  
electrical power is given to the tether, the J x B force will accelerate the  
tether, giving energy back to the shuttle. That right-hand rule comes in  
pretty handy in explaining the details.

--
John R. Manuel                 Department of Physics, University of Alberta
manuel@space.ualberta.ca                 Edmonton, Alberta, CANADA, T6G 2J1
Office: (403) 492-2526          (NeXTMail OK)           Fax: (403) 492-0714