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China's Radical New Space Drive
First time accepted submitter Noctis-Kaban writes "Scientists in China have built and tested a radical new space drive. Although the thrust it produces may not be enough to lift your mobile phone, it looks like it could radically change the satellite industry. Satellites are just the start: with superconducting components, this technology could generate the thrust to drive everything from deep space probes to flying cars. And it all started with a British engineer whose invention was ignored and ridiculed in his home country."
The FAQ deals with conservation of momentum, allowance for bouyancy, electromagnetic effects, convection and other issues here: http://emdrive.com/faq.html. A fantastic picture of the device on this page: http://emdrive.com/.
Here are some of the FAQ answers:
Q. Why does the EmDrive not contravene the conservation of momentum when it operates in free space?
A. The EmDrive cannot violate the conservation of momentum. The electromagnetic wave momentum is built up in the resonating cavity, and is transferred to the end walls upon reflection. The momentum gained by the EmDrive plus the momentum lost by the electromagnetic wave equals zero. The direction and acceleration that is measured, when the EmDrive is tested on a dynamic test rig, comply with Newtons laws and confirm that the law of conservation of momentum is satisfied.
Q. Are there any convection currents which might affect the results?
A. Convection currents did not affect the results, as measurements were taken with the thrust vector up, down and horizontal. Test runs were also carried out using a thermal simulation heater to quantify the effects of change of coolant temperature.
Q. Have electromagnetic effects been taken into account? These include interactions between current-carrying conductors and between such conductors carrying RF currents and nearby metallic structures in which currents might be induced.
A. Stray electromagnetic effects were eliminated by using different test rigs, by testing two thrusters with very different mounting structures, and by changing the orientation by 90 degrees to eliminate the Earth’s magnetic field.
experiment (since IANAP), I do want to say that there seems to be a troubling trend amongst the best and the brightest in many STEM fields to mistake theory for reality. Theory is great and proceeds under the scientific method from empirical observation, but as we've seen throughout history, new phenomena and corner cases to arise and require theory to be amended.
While it is certainly worthwhile to keep an open mind and question our assumptions, there are a variety of different levels of confidence we have in different ideas. The major conservation laws (linear momentum, energy, angular momentum) are mathematically equivalent (via Noether's theorem) to symmetries of the space. If the laws of motion are independent of position then linear momentum is conserved. If linear momentum is not conserved, than the laws of motion are not independent of position. (similarly for rotation invariance angular momentum conservation and time invariance conservation of energy).
http://en.wikipedia.org/wiki/Noether's_theorem
So this goes way beyond understanding of EM theory - if we have a case where momentum is not conserved, that will fundamentally change how we think the universe is put together. In my mind it is much much much more likely that there is error or fraud or psychosis than momentum is not being conserved.
... sort of. And it is established physics. See Swimming in Spacetime: Motion by Cyclic Changes in Body Shape, Science, 2/27/2003, by Jack Wisdom.
But this mechanism relies on general relativistic effects, and only works in curved spacetime. Momentum conservation is not violated, because while the location of the object changes, its momentum (thus velocity) does not -- it simply cyclicly translates itself through space.
My first thought reading about the EmDrive was that Shaywer had found a way to reproduce this effect using a microwave cavity. But unless I'm mistaken, this does not appear to be the case, and I don't follow the arguments that Shaywer's drive should work.
Sorry, no. The whole point of skepticism is to assign a negative (false) value to anything but proven assertions.
That's a related concept properly called positivism.
It is a miracle that curiosity survives formal education. - Einstein
EM can serve as reaction mass, but it creates very little momentum.
This shows the problem :
http://en.wikipedia.org/wiki/Nuclear_photonic_rocket
PS. with antimatter/matter fuel a photonic drive would make sense.