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EmDrive  (Source:
It's a a propellantless microwave thruster that defies Newton's laws of motion

Chinese scientists have taken on a heavily criticized space drive idea that could one day launch satellites, deep space probes and even flying cars.

The research team hails from Northwestern Polytechnic University in Xi'an, and was led by Yang Juan. What they developed was a propellantless microwave thruster called EmDrive, which is a controversial idea because it goes against Newton's laws of motion -- and many have claimed to create a "propellantless" thruster before and failed.

Newton's laws of motion are all based on the idea that firing propellant out of the back at a high speed will push a craft forward. While solar cells offer infinite power, thrust is limited by propellant. Many have tried to get around this, but several scams have made this particular field a joke in the scientific world.

While space drives tend to rely on Newton's laws of motion, the EmDrive is a closed, conical container that has a net thrust toward the wide end when filled with resonating microwaves. This goes against Newton, who said that no closed system could have a net thrust. However, EmDrive works because the microwaves have a group velocity (the speed of a collection of electromagnetic waves) that is greater in one direction than the other -- which is where Albert Einstein's theory of relativity comes in.

British engineer Robert Shaywer, who began looking at the concept of a propellantless thruster when he opened his own company called Satellite Propulsion Research in 2001, is the original creator of the EmDrive. He made demonstration thrusters to prove it could be done, and even made sure the test results were accurate (meaning, the results weren't affected by friction, ionization, air currents, electromagnetic effects or interference). The first, made in 2003, had a thrust of 16 mN. This was enough to show it could be done.

However, he received a ton of criticism for his idea and was ridiculed in his own country. But the Chinese team at Northwestern Polytechnic University believed in his research and took the project head on to author the latest study, "Net Thrust Measurement of Propellantless Microwave Thruster."

The Northwestern Polytechnic University team was able to create the EmDrive with 720 mN of thrust with a couple of kilowatts of power.

So what purpose does EmDrive have? It could halve launch costs of satellites because as much as half the launch weight of these objects are attributed to propellant.

Shawyer is even working on a superconducting thruster that could be ready as soon as 2016. It would boost the Q value of the cavity, which determines the amount of thrust produced. He said it could be boosted by a factor of several thousand, possibly equating to a tonne of thrust per kilowatt of power.

Source: Wired

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By lawsonb on 2/18/2013 1:55:09 PM , Rating: 2
All of the posts shown are important, and to the point (more or less). I possess only an undergraduate degree in physics. But what I have learned is that to pooh-pooh some concept via a knee-jerk response, can be very dangerous. Should the claims of the proponent prove correct, then the scoffer(s) will suffer the egg-on-face syndrome. We must be extremely careful to avoid this type of sneering skepticism. There is a big difference between such baloney devices as the old "Dean drive", which clearly attempted (and failed), to thumb its nose at Newton's laws, and this concept which appears to depend on Einstein's theory. Now I am on both sides of this fence. All I can say is that: Elaborate claims require elaborate proof. I congratulate the Chinese for having the guts to investigate the Emdrive concept without carrying the cock-sure intellectual baggage that some many in the west are carrying. Even if this proves to be a blind alley, at least they are not so hide-bound as to dismiss it out-of-hand.
Imagine the fun we could have if this proves to be viable! Then Shawyer and his supporters could strut to-and-fro in front of their detractors and gloat!

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