[peeters]

> I think we could solve that problem by removing Jupiter. If we drop it into the Sun, we can gain all of its orbital energy in the process.

How did you come up with dropping Jupiter into the sun being a net energy producing operation? You have to cancel out around 10^35 J of kinetic energy to drop it from its orbit, and that is real work. How do you get that 10^35 J back? (Ignoring that from your own math, that E35J is around 100,000 years of the sun's total energy output).

[kragen]

I don't know, but Jupiter has that kinetic energy now, and if you slow it down until it falls into the Sun, it won't have it anymore. The energy has to go somewhere.

Maybe you scoop up big balloons of gas, slingshot them to Mercury with a tether, catch them with another tether on the dark side of Mercury to decelerate them (thus generating electricity which you use to make some kind of fuel), and toss them Sunwards from there.

Or maybe you use an electromagnetic mass driver in the Asteroid Belt to launch an unbelievable number of small rocky masses to a gravitational slingshot around Jupiter back to the same mass driver again, but at a higher velocity, so they generate electric power when it catches them before launching them again. Each mass goes through this circuit tens of thousands of times.

There are lots of possibilities.

[vikramkr]

You're not capturing usable energy, to slow it down, you're accelerating it the other way, consuming usable energy

[beAbU]

You reach up and pull jupiter down while pulling yourself up?

Not an orbital mechanicist though.

[peeters]

Pulling an object "down" (ie towards the gravitational focus) doesn't lower the energy of its orbit, it just changes the eccentricity. To lower its orbit you have to slow it down.