The Emthruster: Thrust without reaction?

[Rynn]

My money is on experimental error given that they report that their negative control also produced thrust:

Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article)

Original conference paper here: http://ntrs.nasa.gov/search.jsp?R=20140006052