Re: Concept: Didn't they do some experiments with...

Bitstring <6e10uvF4pevbU3@xxxxxxxxxxxxxxxxxx>, from the wonderful person John F. Eldredge <john@xxxxxxxxxxxxxx> said
On Mon, 14 Jul 2008 05:59:56 -0400, Jack Bohn wrote:

Don Bruder wrote:

Weren't there some experiments done by NASA with the concept of dropping
a conductor from the shuttle to drag in the magnetosphere with the idea
being that one could, in effect, use the earth as the magnetic "rotor"
of a generator, and the conductor acting as the stator coil. If it's
feasible - and it seems to me, at least at first glance, it could be,
that's a buttload of energy at little cost after the "installation" part
of getting it going.

I'm going through Niven's "Scatterbrain", and in the "Mars: Who Needs
It?" section, he's talking about beanstalks.

Suddenly, like magic, I've got this idea: A beanstalk is likely going to
want about 7.3 metric buttloads of energy to let the transport device
that's moving the cargo around run up and down the cable.

And since the beanstalk is there already, what's stopping it from doing
double duty to support a generating coil hanging up in the
magnetosphere, and letting it power itself... Probably with juice to
spare for the neighborhood?

Well, the conductor has to be moving with respect to the magnetic field,
"cutting the lines," as they say. The beanstalk is all doing one turn
in a day, the same as the Earth. (uh... The core turns in a day, too,
doesn't it? I would think by now at least it would, and the magnetic
field then stays essentially stable with respect to the surface of the
Earth and the length of the beanstalk.)

So, to answer the obvious next question: it wouldn't be unintentionally
bleeding off angular momentum, either.

If it isn't moving across the magnetic field, it also won't be generating
any energy.

I don't think it (a conductor being shoved though a magnetic field) generates any (net) energy anyway, it just swaps one sort for another (kinetic for electrical).

As for powering your beanstalk lift though, that's easy .. there's always stuff that people want brought down, to balance stuff they want taken up. If you ship enough EXTRA stuff down (water ice should be fairly harmless, but presumably refined metals pays better) you can actually generate power.

--
GSV Three Minds in a Can
12,169 Km walked. 2,402 Km PROWs surveyed. 43.4% complete.
.

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