(sanman) wrote
Electromagnetism may allow you to transfer momentum between an object
and the vacuum. If true, this implies a mechanism for propulsion
without propellant mass.

You can push on the Earth's magnetic field. Check out:

http://tethers.com/EDTethers.html

Also my simulator at http://spacetethers.com/spacetethers.html can
simulate the physics for this. The Earth's field drops off fast,
so you probably only want to do this in LEO. But you can use it
to boost a momentum exchange tether which can toss something
further.

-- Vince