I worry a bit about the core assumption behind the Alcubierre drive concept. Here’s why: although Einstein’s field equations of general relativity permit the kind of “geometric” approach the drive proposes, quantum field theory doesn’t do so (at least as I understand things). Just as with the notion of a wormhole (two entangled black holes connected by an ER bridge) when you look closely there’s a catch: in the case of the ER bridge it is the inconvenient fact that it expands faster than anything can traverse it; so you can go in but you can never emerge again. With the Alcubierre drive I worry that there are waveform-related problems associated with the distortion of spacetime that a purely relativistic modeling doesn’t reveal. Perhaps once we have a fully developed theory of quantum gravity, this problem will either come into sharp focus or be shown not to be a problem at all.