Hints of a way forward: Plasma Magnet & E-sail: space is NOT empty (to a potentially useful degree)
Plasma magnet offers ~10^6 ratio of drag power to excitation power. But... how to slow down at destination?
Paraphrasing: While I was at X-Cor, about every 6 months I'd pull this out and think about it.
Need to think about the fundamental physics of propulsion.
Most all propulsion involves using some energy to push on some thing.
1. Propellers, ramjets, cars, etc: internal energy used to push externally-supplied reaction mass. Governed by "propeller equations": power = thrust * airspeed, thrust = Mdot * delta-airspeed.