FTL speed requires infinite amount of energy in this iteration of physics, except for case when vacuum is not empty, but even in this case medium cannot move at

FTL speed requires infinite amount of energy in this iteration of physics, except for case when vacuum is not empty, but even in this case medium cannot move at supersonic speed of medium, while still in one piece. If far away vacuum moves at FTL speed, then there must be "sonic" barrier somewhere.