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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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Neutrinos
By ChronoReverse on 2/10/2013 1:54:36 AM , Rating: 3
http://xkcd.com/955/ I'll take all comers, just leave a message here :P

I'm glad China is funding this so the conspiracy theorists can't claim that some corporation buried the research. Five years down the road, there won't be any hover-vehicles in China.

As an added side benefit, if they really did find a way to generate thrust in a close system without any reaction mass or light pressure, i.e., create momentum out of thin air (aka breaking conservation of momentum), then it's theoretically possible to build a perpetual motion machine from this too.

Let's say I'm betting on not happening just like the thousand times before.




RE: Neutrinos
By PaFromFL on 2/10/2013 8:45:33 AM , Rating: 2
The high Q comment sort of implied a perpetual motion machine but didn't actually make the claim that no energy input would be required for thrust.

My guess is that the group velocity or photon momentum was not properly modeled. From a momentum and energy standpoint, photons trapped in a resonant cavity are similar to gas molecules. Gas molecules possess much more momentum than photons, but do not produce unbalanced thrust when bouncing around in conical containers. When a photon reflects off a conducting surface, the induced currents conserve momentum.


RE: Neutrinos
By DiscoWade on 2/10/2013 8:56:17 AM , Rating: 2
quote:
As an added side benefit, if they really did find a way to generate thrust in a close system without any reaction mass or light pressure, i.e., create momentum out of thin air (aka breaking conservation of momentum), then it's theoretically possible to build a perpetual motion machine from this too.


Homer: "In this house we obey the laws of thermodynamics!"
http://www.youtube.com/watch?v=6vxHkAQRQUQ


RE: Neutrinos
By Amiga500 on 2/10/2013 2:26:20 PM , Rating: 3
quote:
As an added side benefit, if they really did find a way to generate thrust in a close system without any reaction mass or light pressure, i.e., create momentum out of thin air (aka breaking conservation of momentum), then it's theoretically possible to build a perpetual motion machine from this too.


No no no no no.

If there is energy entering the system, it is not out of thin air.

E=mc^2


RE: Neutrinos
By ChronoReverse on 2/10/2013 4:35:14 PM , Rating: 3
It's not as simple as that. Conservation of momentum has a lot of deep implications as a fundamental symmetry. If it were not conserved (this experiment _might_ conserve energy but it doesn't conserve momentum) you can start doing very funky things because a lot of physics depends on momentum to be conserved (and we've never found anything that breaks that).

From reading other articles about this emdrive, it looks like the guy pretty dismissed testing the drive in a vacuum box which rings even more alarm bells. With 2.5MW, just heating a panel would produce significant thrust via the air heating and pushing off.


RE: Neutrinos
By drycrust3 on 2/11/2013 4:46:50 AM , Rating: 2
Just as an aside, we don't actually have any idea what makes gravity work. Gravity is definitely a closed system.
If gravity works, and we know it does, and it doesn't obey the normal laws of physics, just like the Emdrive supposedly doesn't, then it stands to reason that there is a way to make something accelerate without openly using normal Newtonian physics.


RE: Neutrinos
By JediJeb on 2/11/2013 10:05:05 PM , Rating: 2
The thing is we don't know how gravity works. It would be interesting though if somehow this system is interacting with gravity is a way that generates a net thrust.

I know that is a stretch, but since no one knows exactly how gravity works, it can not be ruled out simply because it sounds too far out to consider. We know that there are fluctuations in the microwave background that is related to the overall distribution of mass within the universe, but what if it is caused by some interaction between gravity and microwaves that we have never before considered.

While it still needs to be proven multiple times in different ways, and every possible interference eliminated in the experiments, anyone who would dismiss even the first attempts simply by saying "it defies what we know" they are going down the same road as those who said the sun could not be the center of the solar system because that defied what they knew at the time. What we currently think we understand about the universe may be 99% correct or it may be 1% correct, who knows for sure.


RE: Neutrinos
By JediJeb on 2/11/2013 9:39:11 PM , Rating: 2
quote:
As an added side benefit, if they really did find a way to generate thrust in a close system without any reaction mass or light pressure, i.e., create momentum out of thin air (aka breaking conservation of momentum), then it's theoretically possible to build a perpetual motion machine from this too.


Since microwaves are electromagnetic maybe this is an effect of light pressure, it just isn't visible light.

This engine requires energy input to generate the microwaves, so unless the propulsion can turn a generator and the system has more than a 100% conversion of electricity into thrust then it could never be used to make a perpetual motion machine.


"Mac OS X is like living in a farmhouse in the country with no locks, and Windows is living in a house with bars on the windows in the bad part of town." -- Charlie Miller














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