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Finnish Scientist Provides Another Explanation For The 'Impossible' EM Drive (examiner.com)
MarkWhittington quotes a report from Examiner: Ever since the EmDrive entered the news about a year or so ago, it has sparked considerable controversy. The device is alleged to work by using microwaves that produce, in some fashion as yet unknown to science, thrust. Many scientists suggest that the EM drive is impossible as it violates known physics. However, a number of tests conducted in Great Britain, Germany, China, and at NASA's Eagleworks at the Johnson Spaceflight Center have resulted in thrust that cannot, as yet, be explained by experimental error. The International Business Times reported that a Finnish scientist has published an article in a peer-reviewed science journal with a possible explanation as to how the drive works. International Business Times writes, "A new peer-reviewed paper on the EmDrive from Finaland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting photons that leak out of the closed cavity, producing an exhaust. The research, entitled "On the exhaust of electromagnetic drive," is published in the journal AIP Advances 6 and is the brainchild of Dr Arto Annila, a physics professor at the University of Helsinki; Dr Erkki Kolehmainen, an organic chemistry professor at the University of Jyvaskyla; and Patrick Grahn, a multiphysicist at engineering software firm Comsol."
Recent reports about propulsion without reaction mass have been met on one hand with enthusiasm and on the other hand with some doubts. Namely, closed metal cavities, when fueled with microwaves, have delivered thrust that could eventually maintain satellites on orbits using solar power. However, the measured thrust appears to be without any apparent exhaust. Thus the Law of Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster’s cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagnetic fields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum, gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired-photon conclusion.
Relevant portion of abstract bolded
There's one problem though...
I seem to recall that the net thrust exhibited by the em-drive is greater than the photon pressure of the microwaves. if the thrust was being produced by cancelling photon pairs escaping the system, then it would be some fraction of that potential, not greater than.
I can see this explaining SOME of the thrust, but the deal breaker is the thrust being higher than the photon pressure of the microwaves it runs on. (Else, it would be easier and more efficient to just aim the magnetron's waveguide out the back of the ship.)
Shawyer's non-peer reviewed "quantized inertia" explanation that abuses unruh radiation is more likely to explain the greater thrust values (and also makes some testable predictions.)
Well, maybe you should read the article. They postulate that the exhaust is indeed paired photons, which are impossible to observe. I'm just not convinced that such an EM drive will be more efficient than simply placing a lump of decaying matter at the focus of a reflector and using ordinary infrared photons as the drive.
Excuse me, but please get off my Pennisetum Clandestinum, eh!
That's not how destructive interference works in the EM field. The photons at a point of destructive interference are diverted to area of constructive interference. They don't continue on as an unobservable photon pair. A point of destructive interference in a wave means the photons aren't there. In terms of the wave equation it means the probability of finding a photon at that location is 0. That's not because photons masking each other, it's because physically they are never present at that point.
For anyone interested, the "quantized inertia" explanation was proposed by McCulloch, and is here: http://dx.doi.org/10.1209/0295-5075/111/60005