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EmDrive  (Source: emdrive.com)
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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Use relatable units
By ppardee on 2/12/2013 1:21:01 PM , Rating: 2
OK, who here knows intuitively how much 750 mN of thrust is? Probably a lot fewer than know what a mN stands for (milliNewtons? very small fig cookie/cakes) I know that the Newton is the SI unit for force, but come one peeps. It is meaningless to 98% of the world.

750 mN = about .2 pounds force. So to put a 10 lbs satellite into space, it would require more than 50 of these thrusters? So, we're looking at a WHOLE lot of battery power to get into space. We use physical propellant because it is lighter and more compact than electric storage and whatever locomotive apparatus that utilizes it. Also, the solid rocket boosters and main rockets on the shuttle get lighter as they expend fuel.

Once you're IN space, however, this is probably the best thing ever. It would make a lunar waypoint very feasible. Get the space elevator going with shuttles taking you from the elevator to the lunar base and go to Mars on a solar powered EmDrive! Sign me up, Scotty!




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