I skimmed over Crane and Westmoreland's paper[1] and an article that discusses specific designs[2], and I'm still unsure how one would keep the vehicle and blac

I skimmed over Crane and Westmoreland's paper[1] and an article that discusses specific designs[2], and I'm still unsure how one would keep the vehicle and black hole moving together while also generating thrust. It seems like there would be a conservation of energy problem, regardless of the design. I'm not a physicist, so I'm probably missing something. Most things one would use for thrust in space are inherently repulsive. The part I'm having trouble with is that it seems like even though a black hole would put out a lot of energy, it wouldn't be inherently repulsive, and so any vehicle would have to exert a station-keeping (or orbit-keeping) force equivalent to whatever the over-all black hole engine was emitting, making the engine itself useless. This seems especially true for the design in the second article, where the Dyson shell weighs 600 times as much as the singularity. But again, I'm probably missing something obvious since it's outside my areas of expertise. [1] https://arxiv.org/abs/0908.1803 https://arxiv.org/abs/0908.1803 [2] https://www.space.com/24306-interstellar-flight-black-hole-power.html https://www.space.com/24306-interstellar-flight-black-hole-p...