Well, there is a strong theoretical problem with this propulsion method (known as Alcubierre drive).
The principle is that you curve positively space time in front (say with a point of huge energy or mass in front of the ship), and negatively at the back... that would create a gravitational pulse that will propulsive the ship forwards (the ship surfs the wave).
But how do you curve space-time negatively? With negative energy / mass? Good luck with that...