POSTS Asymmetry in Time Update: See: The EmDrive Just Won’t Die. From nextbigfuture: DARPA Laser Version of EMDrive Has a Test Result Better Than Commercial Ion Drive. These devices are composed of an asymmetric resonant chamber driven by a laser. I think the asymmetry in space causes momentum to not be conserved, but there is also asymmetry in time. I think turning the laser on and off randomly could improve the performance of the device by creating asymmetry in time.