Science Nerds: Could Jupiter's Magnetic Field be harvested for energy?

[HappySkeptic]

What are you thinking of using Jupiter’s magnetic field to power?

A civilization. 

The Jovians live on orbital rings that they have built around the moons of Jupiter. Using a large "wire" (even several hundred kilometers long) would be possible for them to build. They are the most advanced civilization in the solar system. But I want it to be (theoretically) possible. Otherwise, I'll consider using fusion.

I think it would be possible.  I'm just not sure what engineering scale is needed to create enough energy for such a civilization.

Putting wires in space that generate energy causes drag.  The energy gained is your lost kinetic energy.  When ON a moon, the lost kinetic energy of the moon can be ignored, but in any orbital ring, you could be in trouble, unless the drag is directly in the direction of the moon's motion, and perpendicular to the ring (whereby the moon's gravitational field still pulls you along without upsetting the ring).

One thing about rings around things -- they aren't stable.  Larry Niven knew about this with his Ringworld series.  They need constant adjustments to stay in stable position, or they just drift and hit what they are moving around. They aren't actually in an orbit.

Now, separate orbiting bodies (like rotating space stations) are stable because perturbations just change the eccentricity of the orbit -- but too much purturbation (like would be caused by an energy-generating wire) would eventually de-orbit you. There is no free lunch there.

So, energy on the surface of the moons, is a YES. On an orbiting body is a NO