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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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RE: For An Analysis of
By Gondor on 2/9/2013 1:49:41 PM , Rating: 1
So basically this boils down to some kind of energy source (solar panels ?) being used to emit photons, these photons impacting into something solid and thereby transferring a portion of their energy to move the object ... as in lightbulb shining onto a "sail" ?

(insert caricature of a sailboat with a big fan at the back blowing into its sail)


RE: For An Analysis of
By Regected on 2/9/2013 2:54:42 PM , Rating: 5
Mythbusters did just that and it worked


RE: For An Analysis of
By Alexvrb on 2/9/2013 11:51:24 PM , Rating: 2
Ah, Mythbusters. If that doesn't scream scientific method, I don't know what does. Although they still are a smidge behind Ghost Hunters in terms of credibility.

Disclaimer: I still find Mythbusters to occasionally be entertaining as hell. Ghost Hunters... only the South Park version.


RE: For An Analysis of
By serkol on 2/10/2013 10:46:35 AM , Rating: 2
Do you have any doubts about such sailboat actually moving? It will definitely move. It will move even faster if you remove the sail.


RE: For An Analysis of
By Visual on 2/11/2013 4:30:08 AM , Rating: 2
but in the other direction :p


RE: For An Analysis of
By Solandri on 2/11/2013 10:36:57 PM , Rating: 2
It's called a thrust reverser. Planes and waterjets use them all the time to move in the opposite direction of the thrust coming out the engine.

The faulty logic is in thinking the air the fan blows hits the sail and just stops or flows out perfectly sideways. If that were true, then yes it wouldn't go anywhere. But it doesn't stop, it bounces back resulting in a net flow of air opposite the direction the fan is blowing. Hence thrust reverser.


RE: For An Analysis of
By 91TTZ on 2/12/2013 4:37:20 PM , Rating: 2
But that makes efficiency go down the drain. If you had a fan you'd be much better off removing the sail and then steering the fan to propel yourself around.


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