Agreed. When I make hard-ish science fiction settings that feature better drive technology than the real world, I assume that either: 1. A process can conver

Agreed. When I make hard-ish science fiction settings that feature better drive technology than the real world, I assume that either: 1. A process can convert normal matter to dark matter and at the same time accelerate that dark matter to some absurd speed -- so you can take a small reaction mass with you and use it very efficiently, but you don't have an ultra-efficient weapon system. 2. A process can push against some background medium of dark matter. But. If there is dark matter in the vicinity of Earth (and while I agree it's "in the same places as ordinary matter," that's at a macroscopic, galactic level), it's unlikely to be at some convenient rest-y-from-human-perspective frame of reference. Which would suggest that the EM drive would work better facing one direction than others. Which is, I think, not congruent with the experimental evidence in front of us.