Quote from: StrongGR on 05/05/2015 08:22 pmAs far as I can tell, I am not the only one to have thought to a general relativity effect here. This paper uses a modified version of Einstein equations to explain what is going on in a conical resonant cavity without violating momentum conservation. The point is that the author uses a weak perturbation approximation and I do not know if this is fully justified.I had read that paper. Unfortunately, as the author of the paper states:Quote The weakest part of the theory seems to be that there is no clear way of preventing large gravitational effects due to the magnetic field of the Earth, as predicted by Eq. (17)Therefore the author himself admits that his model is contradicted by predicting large gravitational effects due to the Earth's magnetic field that are contrary to all experimental evidence.
As far as I can tell, I am not the only one to have thought to a general relativity effect here. This paper uses a modified version of Einstein equations to explain what is going on in a conical resonant cavity without violating momentum conservation. The point is that the author uses a weak perturbation approximation and I do not know if this is fully justified.
The weakest part of the theory seems to be that there is no clear way of preventing large gravitational effects due to the magnetic field of the Earth, as predicted by Eq. (17)
Multiple reflections of a photon help nothing.
The most important point to be made, is that to measure force, the cavity mustexperience acceleration. In a fully restrained cavity, thrust and reaction forcecancel out.
This situation is unique to a propellantless thruster such as EmDrive and analogieswith conventional devices are pointless.
It therefore appears that a force measurement can only be made in a dynamicenvironment, ideally by allowing the thruster to accelerate, measuring thatacceleration, and then calculating the thrust from T = -Ma
Quote from: ppnl on 05/06/2015 07:39 amMultiple reflections of a photon help nothing.Yeah. Because most of us are completely sure that newtons law are correct, the only way that EMDrive and similar devices could work is transferring momentum. What, where and how are the questions.It must be something different to photons and it must exists before, because push photons will mean less pushing for this energy.White talk about virtual particles. I thing that the form could be more exotic. Something like a partially stable perturbation of quantum vacuum. Something like a vortex in a fluid but in quantum form, like a field not locally binded to a particle.Whatever it was, it must carry energy by itself so push it carries more momentum that pure photons.If a photon is like a fish in water, these unknown "momentum carriers" must be like walls in water. It must push vacuum energy, so it carries more momentum in the same way as you push more mass for the same energy.
Could we perhaps view a resonating EM wave cavity as a means to dynamically 'synthesize' or evoke 'exotic matter' ?
Quote from: ppnl on 05/06/2015 07:39 amMultiple reflections of a photon help nothing.Yeah. Because most of us are completely sure that newtons law are correct, the only way that EMDrive and similar devices could work is transferring momentum. What, where and how are the questions.It must be something different to photons and it must exists before, because push photons will mean less pushing for this energy.
Hmm, so let me maybe replace the photon rocket idea with a solar sail.So you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.But suppose your sail could experience multiple collisions with each photon that came out of the emitter? So that's the waveguide that's allowing this to happen. And each of those collisions is transferring some momentum. So the sum total of all momentum that a photon can transfer to the waveguide can't exceed the original momentum of the photon when you first produced/emitted it. So net thrust is zero because of the anti-thrust from producing the original photon.Hmm, so now it doesn't work again...I better go ask GoatGuy.
Pulse phasing discussed here:
Quote from: TheTraveller on 05/06/2015 09:49 amPulse phasing discussed here:http://s000.tinyupload.com/index.php?file_id=05426775513544255924A interesting idea. That the EMDrive could be something like a "momentum capacitator", in form of photons inside the cavity. That must be accounted accurately, because is a good source of errors.Momentum could be "transfered" in time. A lot of photons are accumulated inside and when the walls of EMDrive change the temperature, the light reflect more than before, making do absorbed at different rates on different walls of the EMDrive making the net momentum accumulated in the photons.But if the photons are accumulated on some time and released on less time and measured in this smaller time window, the force could be accounted greater than really are.This hypotesis would require a "charging time" on the EMDrive before the measurement.
Pulse phasing discussed here:http://s000.tinyupload.com/index.php?file_id=05426775513544255924
So you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.
Quote from: sanman on 05/06/2015 07:11 amSo you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.If the sail is reflective then it delivers twice the momentum of when the photon was initially released. Think of it like a baseball. When someone throws it and another catches it, the actions cancel. This is like absorbing the photon. If the catcher throws it back again as well (reflection) this is like a whole new throw. Luckily due to conservation of momentum we need not worry about the details, we can just look at before and after.
So here's a theory, such as it is. The EM waves are 'cut' and 'squeezed' by the shape of the vessel.
Regarding the main controller parameter for the EM DriveIt is my understanding, from what Paul March wrote, that the main controlling parameter in determining the thrust generation performance of the EM-Drive is the rate of phase modulation of the RF signal that is injected into the resonant cavity. This requires an FM modulated signal of around 100 kHz deviation that dithers back and forth around the resonant cavity's resonant frequency as fast as possible. One has to feed the cavity through a 2 foot long RG-8 cable with Type-N connectors with the other end of this coax connected to a 3-Stub tuner that is used to set the 50 ohm Smith Chart Z-matching circle to an impedance solution that matches the 50 ohm load AND generates the narrowest +/-90 degree capacitive to inductive reactive phase change bandwidth in the cavity. This phase change bandwidth needs to be 10 kHz or less and preferable less than 4 kHz. This information is useful to correctly and consistently tune an EM-drive prototype for maximum thrust. If anybody has a different understanding of what he wrote, it would be useful to know.
My understanding was that he could set the match to obtain the maximum phase change across the resonance line. This would give him the maximum effective Q. The FM dither would be a means of following the resonance. Back when, I used a double balanced modulator to find the 2 half-power points as the most accurate way to identify the center frequency. (but I didn't need a carrier there, I was measuring linewidth) AM or FM can be used the same way and in these cases you have power at the center of the resonance.