  ''Warp drive'' spacetimes are useful as ''gedanken-experiments'' and as a
theoretician's probe of the foundations of general relativity. Applying
linearized gravity to the weak-field warp drive, i.e., for non-relativistic
warp-bubble velocities, we find that the occurrence of energy condition
violations in this class of spacetimes is generic to the form of the geometry
under consideration and is not simply a side-effect of the ''superluminal''
properties. Using the linearized construction it is now possible to compare the
warp field energy with the mass-energy of the spaceship, and applying the
''volume integral quantifier'', extremely stringent conditions on the warp
drive spacetime are found.
