[Paleopsych] Very alternative energy: the space tether experiment

[Steve Hovland]

#25c.     The Space Tether Experiment
The space tether experiment, a joint venture of the US and Italy, called 
for a scientific payload--a large, spherical satellite--to be deployed from 
the US space shuttle at the end of a conducting cable (tether) 20 km (12.5 
miles) long. The idea was to let the shuttle drag the tether across the 
Earth's magnetic field, producing one part of a dynamo circuit. The return 
current, from the shuttle to the payload, would flow in the Earth's 
ionosphere, which also conducted electricity, even though not as well as 
the wire.

One purpose of such a set-up might be to produce electric power, generating 
current to run equipment aboard the space shuttle. That electric comes at a 
price: it is taken away from the motion energy ("kinetic energy") of the 
shuttle, since the magnetic force on the tether opposes the motion and 
slows it down. In principle, it should also be possible to reverse this 
process: a future space station could use solar cells to produce an 
electric current, which would be pumped into the tether in the opposite 
direction, so that the magnetic force would boost the orbital motion and 
would raise the orbit to a higher altitude.

http://www-istp.gsfc.nasa.gov/Education/wtether.html