OT? Shawyer EM Drive Explained. Again.

It seems more likely that it's a variation on the Woodward effect, where the asymmetrical sloshing of energy density produces a nonzero higher-order term in the relativistic forces acting on the device; a Mach effect.

Devices based more directly on that effect (which include a coincident mechanical displacement: the resonator uses a piezo disk) have similar magnitudes of thrust. Which doesn't really confirm anything, as again these are still very small thrusts.

And yeah, the below description doesn't sound good. A QM description might show the wave function is imaginary near the shield, so that it's nonzero (in magnitude), but the observables (probability, classical field amplitudes) are zero. But that shouldn't be constant for all phases in a time-varying system, I think..?

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

The nub of it is this:

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."

Just the mention of photons in a cavity says to me that these guys have a strange understanding of EM fields in cavities, but ignoring that for a moment...

They go on to explain that the "exhaust" will forever be undetectable, but those waves which cancel exactly at the inner wall can't possibly be propagating in exactly the same direction, meaning at some distance from the cavity they will become out of phase and therefore be detectable as ordinary RF.

And this is the very first instance of photons "co-propagating with opposite phases" in nearly a century of people fooling around with cavity resonators? Why has nobody measured the loss from it before?

As a Golden Age SF geek I'd really like this thing to be real but this sounds like some overly educated folks fooling themselves.

Mark L. Fergerson

Strange is in the eye of the beholder. Viewing the propagation of radio waves as strictly an EM phenomenon is basically a way of making the math easy, by taking the behavior of a collection of big, low-energy photons to a limit where the number of photons is infinite. It's only as valid as the approximation (huge = infinite) is.

If anything is actually going on then it's a second- or third-order effect, which are not dealt with in traditional E&M theory.

I think you're summary is correct. The sentence that made me stop reading the paper is "We agree the vacuum is not a transfer medium for photons, instead we maintain that it is made of photons." They then go on to point to a bunch of indirect evidence for this, but they offer up no line of investigation to prove or disprove this.

What I want to know is -- why can't you just make an _open_ resonator with the antenna pointed in the direction you want to go away from, and use the momentum of the actual, real, microwave photons to generate thrust? Shouldn't this be more efficient that some weird (and presumably inefficient) "closed" resonator?

Taking physical systems to mathematical limits generally leads to unphysi cal predictions; you can't pack anywhere near infinitely many big, low ener gy photons into a cavity resonator. You'll get arc-over first...

I don't see higher-order effect appearing in any realizable asymmetrical cavity system.

What theory explains how, when you backtrack these pair-cancelling photon s, they all still have to originate at the input coupling? Where does the p hase inversion for some of them come from?

I meant "...meaning at some distance from the cavity their paths will div erge sufficiently that they will no longer cancel and therefore...".

I was distracted. Excuse, sticking to it.

Quantum theory does say the vacuum's full of virtual photons and virtual particle-antiparticle pairs, and so on, but it stops short of claiming they make up the vacuum. The Casimir effect verifies the virtual photons but do esn't demonstrate that the vacuum is "made of" photons in any meaningful wa y.

The A field permeates all of space and can't be shielded. In a sense phot ons are self-propagating disturbances in that field, but that doesn't mean the vacuum's "made of" the A field or its disturbances.

Sure, but best (mathematically ahem limited) case you get 1 whole newton of thrust per 300 MW dissipated (look up "photon rocket") plus you still ha ve an "exhaust port" which the EM Drive wouldn't if it worked.

There's also supposedly no microwave beam "exhaust plume", but if the thin g worked, and were scaled up to move a massive payload, wouldn't those magi cally disappearing antiphase photons show up eventually? I think so, and it likely wouldn't be pretty.

Mark L. Fergerson