I’ve held off mentioning this because… well, I’m tired of Wonderful Advances being announced, only to later be the result of experimental error, easily fixed by jiggling  wire. It seems likely that this is probably the case here, too:

Don’t Get Too Excited About NASA’s New Miracle Engine

A number of points are raised, but to me the most disturbing is this:

[The researchers] hook up a gizmo with all sorts of electromagnetic fields fluctuating around, then claim to measure an extremely tiny thrust (about the weight of a single grain of sand), which occurs even for the test article that wasn’t supposed to produce any thrust at all.

Ahhhhhhhh. When the engine produces the same thrust when it’s just an inert lump of metal as when it’s at full thrust… well, that just screams “experimental error” to me.