Is the Impossible “Emdrive” Possible?

A controversial concept called the electromagnetic drive, or Emdrive for short has been called impossible. But one company believes the concept is viable and has worked for several years on building demonstration models. The Emdrive is a reactionless propulsion system that supposedly generates thrust by converting electrical energy via microwaves. If it works it could provide an almost endless supply of thrust for satellites and possibly other spacecraft. But no detectable energy emanates from the device, and most scientists say the Emdrive violates the well-established principle of the conservation of momentum. Satellite Propulsion Research, Ltd. (SPR), the company working on the drive now says researchers from China have confirmed the theory behind the Emdrive, and they should have a trial engine ready to test by the end of this year.

A reactionless drive was first proposed in the 1950’s, but came to attention in 2006 when New Scientist published an article about Dr. Roger Shawyer, who founded SPR, and claimed he had constructed a prototype that produced 88 millinewtons of forces while using only 700 watts of power. The idea was met with criticism from nearly all fronts.

The idea of the Emdrive involves forces created by reflecting microwaves between opposite walls of a cavity. If a cavity could be designed which would cause the forces on one side to be greater than the other, thrust could be achieved. The proposed cavity is cone shaped, which supposedly would provide the unequal force design.

In principle, no microwaves or anything else leaves the device, and so it is considered reactionless. But Shawyers website claims that the device is not reactionless, or a perpetual motion machine, because the force is created by a “reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it.”

Originally, Shawyer, a British scientist, got funding from the UK, and then from am US company. Now the researchers at China’s Northwestern Polytechnical University (NPU) in Xi’an say they have confirmed the Emdrive theory, and have gotten funding to build the device.

Their device is based on Shawyer’s theories, and if it works, it would confirm what Shawyer has been claiming all along. The Chinese lead researcher, Professor Yang Juan, previously has worked with microwave plasma thrusters, which has similar engineering principles. A recent article in Wired said he Chinese should be capable of determining whether the thruster really works or whether the apparent forces are caused by experimental errors.

If the Emdrive works, what would it mean for spaceflight? Shawyer says a solar-powered Emdrive could take a manned mission to Mars in 41 days.

Paper by Shawyer on the Emdrive (not peer reviewed)
Opposing paper by Dr. John Costella

Sources: Wired, Emdrive.com, Wiki