What are the thoughts about using a magnetic sail propelled by a powerful alpha emitter (e.g. polonium)? Imagine a 1kg sphere of polonium radiating alpha particles in all directions. Attached to the sphere, via boon, is a powerful magnetic field emitter that would repulse or even deflect forward thrusted alpha particles. Would the net momentum propel the sail in the direction of the magnetic field? Also, perhaps this could be made more effecient by having magnetic fields emitters attached around the sphere and deflecting the alpha particles at an angle away from the forward momentum. Even a rear magnetic field which is attracted to alpha particles could assist in effeciency. The benefit of this is that the density of alpha particles will only fall off over time versus distance (e.g. the sun). Also, the high velocity alpha particles wouldn't damage the magnetic field (but yes, perhaps they would damage the magnetic field emitter).