The fastest hypervelocity star I can find with a quick bit of googling is S5-HVS1, at 1700 km/s [1], slower than the hypothetical black-hole-accelerated ship ex

The fastest hypervelocity star I can find with a quick bit of googling is S5-HVS1, at 1700 km/s [1], slower than the hypothetical black-hole-accelerated ship example. You can't delve arbitrarily deep into a black hole's gravity well if you want to get something back; you need to stop at the horizon, where the escape velocity equals light speed. Dumping sacrificial mass into the hole is built into the Oberth effect scenario: the ship's extra speed (relative to the hole) is matched by a lower speed for the ejected reaction mass, which therefore falls toward the hole. I suppose you could imagine something like a circular accelerator built around the hole and powered by dropping masses into it. [1] https://newatlas.com/space/fastest-star-hypervelocity-ejected-milky-way/ https://newatlas.com/space/fastest-star-hypervelocity-ejecte...