this gem ... hidden in the article:
"... whether it is possible for a spacecraft traveling at conventional speeds to achieve effective superluminal speed by contracting space in front of it and expanding space behind it. ..."
They've been playing at that for a while. It would allegedly work by creating a condition of cosmic expansion behind the craft and its converse in front of it, so the spacecraft is in a bubble where it's running slower than lightspeed (i.e. stopped) but the cosmic expansion and contraction regions behind and ahead of it each total to the opposite sides retreating or advancing faster than light (which is allowable).
I'm not holding my breath waiting for that to fall out of this - or anything. Effective superluminal translates to "Sending messaages into the past." and "Violating causality." if you pick your reference frames correctly. So I expect flies to appear in this ointment at some point: Like something broken about what happens at the sides, needing big-bang energy levels (and not being able to transfer them between the front and back so they're free), or not being able to set up the condition in front because the agency making it happen must involve actual superluminal signal propagation.
Nevertheless, an "electric motor" that works by pushing against virtual particle-antiparticle pairs (or the total mass of the matter in the universe, or of an inverse-square weighting-by-distance of it so it's mostly the local stuff, or dark matter, or the neutrino background, or whatever), instead of ejected exhaust, is just DANDY! Let's see if they can make it work for real at human-palpable, nontrivial, efficiencies and power levels.