Comment There is a way around that... (Score 1) 265
This kind of 'thruster' simply can't work in any practical way.
Actually that depends. As you remove the electrons the charge will build up which means that you have an increasing electric field. Providing that you kick out the electrons with sufficient energy to escape the field the field will continue increasing and will reach the point where it will breakdown even in vacuum.
For a high enough field strength virtual electron-positron pairs will gain sufficient energy as they are pulled apart to become real. The electron will be attracted back to the craft to neutralize some of the positive charge there and the positron will be repelled out into space creating even more thrust. The result is that after achieving a critical charge the charge will stop increasing.
However you will need a huge charge build up to get this far and you would probably need high energy gamma rays to give the electrons sufficient energy to escape the intense electric field required (otherwise they will not leave the material). Since you are, at this point, essentially converting energy into mass and flinging it out the back of the craft I also expect that your net thrust would be no different than just reflecting the incident photons.