Right, that may be possible, but the original poster seems to be wanting known offshoots of technology, not sci-fi types. An article I recently saw on the warp drive indicated that the energy requirements may be absolutely absurd. (As in greater than the total energy of all the matter in the...
If I could toss in a couple of cents on this.
Real world hard physics without exotic (currently non-existent sci-fi) technology tends be be rather slow on both planetary and especially interstellar games. Though I have no idea what timescale you'll be using.
A ship with twice as much thrust...