Chinese researchers claim to have verified the theory behind a space drive that by all rights should not work. According to British scientist Roger Shawyer, his electromagnetic drive, or Emdrive, needs no propellants, but instead converts electrical energy into thrust via microwaves by exploiting the properties of relativity. To describe Shawyer's work as controversial understates the reaction. The Chinese have some expertise on thrusters using similar construction but based on conventional physics, and they should be able to tell whether the drive is actually working or whether the forces are the result of experimental errors. If they're right, this might transform the economics of satellites, open up new possibilities for space exploration - and give the Chinese a decisive military advantage in space.

Needless to say, independent confirmation is a big deal -- though many will want to see it published in a peer-reviewed journal. Even when it is, I doubt the controversy will subside. Prof. Yang has plenty of experience in this type of area, having previously done work on microwave plasma thrusters, which use a resonant cavity to accelerate a plasma jet for propulsion. While the theory behind the Emdrive is very different, the engineering principles of building the hardware are similar. The Chinese should be capable of determining whether the thruster really works or whether the apparent forces are caused by experimental errors.

The thrust produced is small, but significant. Shawyer compares a C-Band Emdrive with the existing NSTAR ion thruster used by NASA. The Emdrive produces 85 mN of thrust compared to 92 for the NSTAR (that's about one-third of an ounce), but the Emdrive only consumes a quarter of the amount of power and weighs less than 7 kilos, compared to over 30 kilos. The biggest difference is in propellant: NSTAR uses 10 grams per hour; the Emdrive uses none. As long as it has an electricity supply, the Emdrive will keep going.

The possibilities are phenomenal: Instead of going out of service when they run out of fuel, satellites would have greatly extended endurance and be able to move around at will. (We wouldn't have to shoot them down because of the risk from toxic fuel either.) Deep space probes could go further, faster –- and stop when they arrive. Shawyer calculates that a solar-powered Emdrive could take a manned mission to Mars in 41 days. Provided it works, of course.