Warp drives are very interesting configurations of General Relativity, since they provide, at least theoretically, a way to travel at superluminal speeds. Even if one succeeded in building them, it would still be necessary to check whether they would survive to the switching on of quantum effects. In this contribution we describe the behavior of the Renormalized Stress Energy Tensor (RSET) associated with a scalar field living in a superluminal warp-drive spacetime created out of an initially flat geometry. We find that the RSET grows in time close to the bubble front wall, supporting the conclusion that these geometries are unstable against semiclassical back-reaction.
