See: https://www.technologyreview.com/s/601299/the-curious-link-between-the-fly-by-anomaly-and-the-impossible-emdrive-thruster/
Not a whole lot new, but interesting to see the MIT Technology Review pick up the story. The article briefly describes Mike McCulloch's suggestion that Unruh radiation, a type of blackbody radiation, is at work. I myself suspect that the emission of neutrinos is involved. Eric
