The list of things that handwavium does that drives physicists up the wall and closer to professorship is long. Reactionless drives are high on that list. For hundreds of years we've known exactly what to expect thanks to Newton's Third Law: For every action there is an equal and opposite reaction. Unless the 'wave is involved, then it's all action, all the time.
Reactionless thrusters and drives merrily flip Newton off and continue on their way, providing thrust for what is essentially no exhaust plume at all. As such the inner workings of the various kinds of reactionless engines are rather poorly understood. Some seem to be gravity based, some play merry hob with inertia, and others are just plain strange, even by the 'wave's standards.
- I leave the tasteful jokes to someone else
- Unless an exhaust plume would be Cool.