BTW, even if could do one, it would be unstable:
http://arxiv.org/pdf/1111.4356v2.pdf
"superluminal warp drives are quantum mechanically unstable because they produce a Hawking-like radiation which is blue shifted at their front wall without any bound. When the dispersion relation is subluminal, the horizons act as a resonant cavity producing a dynamical black-hole laser instability. When it is superluminal, instead, the emitted flux grows linearly in time due to infrared effects."