On Wed, 17 Oct 2007 07:54:09 -0700, Ian
wrote:

The linear velocity of the earth at
the equator is 40,000km / 24 hrs = 462 m/s. The absolute best you can
therefore hope to achieve with a homopolar generator is 462 m/s * 0.07
mT = 0.03 V/m.

A 20m mast will therefore give you a whopping 0.6V (maximum) to play

Unfortunately your calculation is more or less meaningless, and I can
only hope you had a good calculator and didn't waste a lot of time on
it. Since the earth and its magnetic field rotate together, the
maximum velocity relative to the magnetic field, is precisely zero. So
zero voltage is what you get that way.

Of course you actually would get about 12 000 volts, but another way.
Static electricity. A big tower will hold a lot, and it has been known
to kill. Scientific American had an article detailing how to make a
5000 volt motor a pinwheel that uses corona discharge from the tips of
the blades, and spins pretty fast for a little chunk of aluminum foil.
Powered by a vertical wire.

Incidently, orbiting objects do move fast with respect to the field,
and a long wire will stretch out vertically due to tides. This will
creat drag, and lower the orbit if you extract any juice this way. On
the other hand, if you feed in juice from solar cells you get a
current in a magnetic field and have a weak motor, which could,
gradually raise the altitude of the orbit. You would use no reaction
mass, the attraction of the idea. I have seen calculations, probably
in Analog.

This is perhaps a place to use your nice calculation.

Casady