What if the craft itself had a magnet at the rear, with an equally sized magnet that you could either bring towards the craft to propel forward ....or controlling it away from the ships magnet to reduce the “push” between the two and eliminate the propulsion .... granted it would probably be long and the magnets would be tremendous in size. such a thing has to be possible to do in space, right? Controlling the distance between two giant magnets to propel a craft forward?
This can't work.
Please refer to the image below of my patented MagnaRocket.
The magnetic repulsion force pushing on the magnet at the rear of the MagnaRocket....also pushes back just as strongly on the magnet attached to the purple arms.
If you move the patented purple HingyArms to move the magnet closer, or further away, the magnetic force changes, but it still is the same on both magnets.
Net force...zero. Motion....zero.
(Note: MagnaRocket and HingyArms are not really patented)