Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1875934 times)

Offline Notsosureofit

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Just worked out number of coupled cycles.  Posting on emdrive.

works out to f*c/g where g is the accelerated frame......
« Last Edit: 06/02/2015 01:40 AM by Notsosureofit »

Offline Rodal

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Just worked out number of coupled cycles.  Posting on emdrive.

works out to f*c/g where g is the accelerated frame......

OK, I'll look for it.  Incidentally why did you choose PQ = 2*10^6 watts for your example ? any particular reason, relating to one of the test cases?

Offline Notsosureofit

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Just convenient

Offline Rodal

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Just convenient
Since PQ is arbitrary,  wouldn't it be preferable to choose some power of 10, like 10^6 watts or 10^7 watts?

Then the vertical axis for force acts like a scaled force, and it is (a little) easier for the reader to find out the force based on a given PQ ?

Otherwise one could plot force/(PQ) but dimensionally force/(PQ) would be a really small number  :)

Offline Rodal

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This is fantastic !

What made you think of that?

Great work

Quote from: Notsosureofit
An interesting expression to examine is fc/g

It represents the number of cycles for the photons in the cavity to reach velocity c if they were free to do so at the acceleration g. In that respect it represents a degree of coupling between the standing waves in the cavity and a traveling wave.
Do the three curves represent p=1, p=2 and p=3 ? (where p is the quantum number TMmnp or TEmnp in the longitudinal direction ?)
« Last Edit: 06/02/2015 02:21 AM by Rodal »

Offline Notsosureofit

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Yes p = 1,2,3

Yes, I was looking at your request for couplings.

Notice that for a cylindrical cavity, it takes an infinite amount of time.
« Last Edit: 06/02/2015 02:28 AM by Notsosureofit »

Offline Rodal

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Yes p = 1,2,3

Yes, I was looking at your request for couplings.
Are both TM and TE modes shown or did you consider just TM modes ?

Offline SeeShells

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I should know better than to post a 1st draft of anything, but here goes nothing...

What I've done is put together all of the pieces we have been working on, between Egan, Yang, De Aquino and Shawyer. What I ended up with didn't surprise me. What did is how much this "mimics" gravity  in the PV Model is not even funny!

Let the show begin!

Todd

The show is not ready for prime-time yet, but working on it...

Continuing from here:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1381966#msg1381966

An outstanding important question in developing this theory of EM Drive motion due to internal evanescent waves produced by geometrical attenuation (due to tapering of the walls of the truncated cone towards the small end) is whether the evanescent waves can couple to the enhanced energy density due to Q resonance standing waves.  It is is very important to show this, because otherwise the EM Drive would not be able to be superior to a perfectly collimated photon rocket.  The stored energy density from resonance is the key.

It is important to show whether there is coupling of the evanescent waves with the standing waves.  That there is coupling between travelling waves and evanescent waves is shown in the paper of Zeng and Fan where one mode after another gets attenuated as it propagates towards the small end.  However that's for an open waveguide, where travelling waves and evanescent waves can be easily shown to be in phase (particularly for phase constant equal to zero).  Doubts were expressed in this thread as to whether this is possible for standing waves and evanescent waves.

The answer appears to be yes, at least in some qualified situations.  There are a number of papers showing coupling between whispering -gallery modes and evanescent waves.  It is far from clear whether whispering-gallery modes could be present in the EM Drive operation, (whispering-gallery modes would involve much higher frequencies -what is the highest frequency that a Magnetron puts out ?-).

This recent reference (2013) shows whispering-gallery modes in the microwave frequency at 10 GHz: http://arxiv.org/pdf/hep-ph/0506074

The fact that whispering-gallery modes can couple with evanescent waves is interesting enough.

Coupling between high Q cavities (of the ring type) and evanescent waves have also been shown.

Constructive interference.

It looks like the analysis may require numerical analysis, as all the papers I have seen so far have used the Finite Difference method to solve the problem numerically. 

The problem is difficult, mathematically, but entirely within Standard Physics.

It is intriguing whether some of the gradient theories (Shawyer's gradient in group velocity, McCulloch's gradient of Unruh wavelengths,  Notsosureofit gradient of dispersion, and this one geometrical attenuation gradient with coupling of standing and evanescent waves, are related somehow, rather than just superficially).





I honestly believe Todd has the tiger by the tail here and is on the right track. My math is just too rusty but not bad enough not to understand and see the connections.  Feeling here is something that needs to be followed. Good work Todd and a great followup Rodal.

Offline Notsosureofit

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Yes p = 1,2,3

Yes, I was looking at your request for couplings.
Are both TM and TE modes shown or did you consider just TM modes ?

All the modes are there.  Same data table as above.

Offline Quintaglio

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This is my first post so I hope you forgive me if I make any mistakes

When the microwave is sent through the cavity is it passing through a vacum or is the chamber full with some sort of gas?

If there is a gas inside the cavity would the microwave heat this, and with the conical shape allow the heat to pass up the cones wall?

Stuart

Offline Rodal

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...

Notice that for a cylindrical cavity, it takes an infinite amount of time.
Is that because for a cylindrical cavity  delta f is zero (since the the diameters at both ends is the same, there is no gradient in that case), and therefore the acceleration g is zero for a cylindrical cavity, and therefore the number of cycles fc/g -> Infinity for a cylindrical cavity ?

This goes nicely with the fact that for a perfectly cylindrical cavity there is no geometrical attenuation, hence no travelling waves being cut-off and becoming evanescent waves.
« Last Edit: 06/02/2015 02:50 AM by Rodal »

Offline Notsosureofit

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Offline Rodal

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Yes
Then, if the fellows in Aachen, Germany, have scaled all their cavity dimensions for Baby EM Drive such that

bigdiameterAACHEN = bigdiameterNASA / (frequencyAACHEN/frequencyNASA)

smalldiameterAACHEN =smalldiameterNASA / (frequencyAACHEN/frequencyNASA)

lengthAACHEN = lengthdiameterNASA / (frequencyAACHEN/frequencyNASA)

they don't have to worry about operating at frequencyAACHEN = 24 GHz, since the number of cycles needed for the photons in the cavity to accelerate to c (if they were free to do so), the coupling, would be what your curve shows at around frequencyNASA = 2 GHz, the NASA frequency ?
« Last Edit: 06/02/2015 03:09 AM by Rodal »

Offline deltaMass

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 :o Are you guys seriously talking about accelerating photons?  ???

Offline WarpTech

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...
My feeling is that you are on the right track. For some reason I keep thinking that there is a rotational factor (about the cavity axis) and a related symmetry issue; as in perhaps needing to break the symmetry to reach a stable state.

Thanks. The geometry breaks the symmetry, but I've been playing with a coaxial frustum idea, fed from the small end so that I can start with a DC analysis and an AC, 1/4-wave stub analysis. What I'm learning is that as charge moves front to back, it "sees" it's reflection in the big end ground plane and is attracted to it, accelerating the wave. As charge moves from back to front, it sees less of a reflection, practically "none" if the frustum were a pointed cone. Instead, the charge density spikes.

Since I'm feeding it from the small end with an axial conductor down the middle, the magnetic field is circular around the axis. It's a 1-turn, air-core inductor. The Electric field is split, with the voltage gradient vector between the axis and the frustum, -Del(Phi) due to the applied voltage source, and a vector following each conductor, -dA/dt as it charges.  The A field is parallel to the conductor surfaces.

The attenuation "relative" phase factor (k - Beta) can then be seen quite obviously I think, (still working on verifying that). What I see is inside a coax, the magnetic field is only dependent on the current on the inner conductor. So the phase of the magnetic wave is relative to the axis. Remember if we have positive charge oscillating on the axial conductor, we have negative charge on the inside of the outer conductor. Where the magnetic wave crosses the frustum, the relative phase is a variable depending on R(z). There is a forward-rectified Lorentz force acting on the frustum, but there is no opposing force on the inner conductor because the B field is perpendicular and very small at the center due to the circular symmetry. There is however, a strong opposing force at the back end plate that may or may not fully cancel it as it's charging.

I'll say more once I've worked it out for myself. I want to prove there are asymmetrical forces as it's charging and discharging. Once the principle is understood, we can do real engineering designs for kN of thrust.

Todd

Offline WarpTech

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Just worked out number of coupled cycles.  Posting on emdrive.

works out to f*c/g where g is the accelerated frame......

Where is it posted?

Offline ThinkerX

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Quote
Just worked out number of coupled cycles.  Posting on emdrive.

works out to f*c/g where g is the accelerated frame......

Quote
Where is it posted?

The wiki linked to on post 1, page 1 of this thread.




Offline OttO

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After Notsosurofit post, it would be interesting to know if the tapered cavity could work in purely optical mode (with a laser feeding it) :P

For DIY let's build areas of 10*10 blue ray diodes...
« Last Edit: 06/02/2015 06:47 AM by OttO »

Offline zen-in

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The show is not ready for prime-time yet, but working on it...

Continuing from here:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1381966#msg1381966

An outstanding important question in developing this theory of EM Drive motion due to internal evanescent waves produced by geometrical attenuation (due to tapering of the walls of the truncated cone towards the small end) is whether the evanescent waves can couple to the enhanced energy density due to Q resonance standing waves.  It is is very important to show this, because otherwise the EM Drive would not be able to be superior to a perfectly collimated photon rocket.  The stored energy density from resonance is the key.

It is important to show whether there is coupling of the evanescent waves with the standing waves.  That there is coupling between travelling waves and evanescent waves is shown in the paper of Zeng and Fan where one mode after another gets attenuated as it propagates towards the small end.  However that's for an open waveguide, where travelling waves and evanescent waves can be easily shown to be in phase (particularly for phase constant equal to zero).  Doubts were expressed in this thread as to whether this is possible for standing waves and evanescent waves.

The answer appears to be yes, at least in some qualified situations.  There are a number of papers showing coupling between whispering -gallery modes and evanescent waves.  It is far from clear whether whispering-gallery modes could be present in the EM Drive operation, (whispering-gallery modes would involve much higher frequencies -what is the highest frequency that a Magnetron puts out ?-).

This recent reference (2013) shows whispering-gallery modes in the microwave frequency at 10 GHz: http://arxiv.org/pdf/hep-ph/0506074

The fact that whispering-gallery modes can couple with evanescent waves is interesting enough.

Coupling between high Q cavities (of the ring type) and evanescent waves have also been shown.

Constructive interference.

...


I have serious doubts this theory of thrust generated from evanescent waves interacting with the standing wave at the short end of the cavity has any basis in physics.    Evanescent waves are synonomous with near field radiation in the RF world; at least this is what the Wikipedia page says:
"In electrical engineering, evanescent waves are found in the near-field region within one third of a wavelength of any radio antenna...."
http://en.wikipedia.org/wiki/Evanescent_wave
There are no evanescent waves inside the cavity because the Poynting vector = 0.   An antenna or feed horn does have evanescent waves, although RF engineers refer to that as the near field radiation.   There are also evanescent waves inside the copper but those are contained in a very small thickness due to the skin effect.   There are no standing waves inside the copper to interact with those evanescent waves.

Even if evanescent waves and the standing wave did coexist in the same space there would be no magical effect as claimed.   That superposition of RF voltages and currents is resolved as just another humdrum vector by the use of the Superpositioning Theorem.   If it was any different our universe would be a very different place and we would likely not even be here.

In the last thread there were claims the em-drive cavity produced a warp field.   The "evidence" presented for this claim was a rather ordinary interference pattern.   Now there is another esoteric theory.    The problem is there is no data to even support claims a thrust is being produced.   No one has replicated this claimed em-drive and supplied data to prove there is any thrust.    That would be the first step.    The proof would be a  180 test that shows thrust above the error bars and is repeatable and with that experiment replicated in an open lab with all raw data being reported.   

Offline Mulletron

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Yes
Then, if the fellows in Aachen, Germany, have scaled all their cavity dimensions for Baby EM Drive such that

bigdiameterAACHEN = bigdiameterNASA / (frequencyAACHEN/frequencyNASA)

smalldiameterAACHEN =smalldiameterNASA / (frequencyAACHEN/frequencyNASA)

lengthAACHEN = lengthdiameterNASA / (frequencyAACHEN/frequencyNASA)

they don't have to worry about operating at frequencyAACHEN = 24 GHz, since the number of cycles needed for the photons in the cavity to accelerate to c (if they were free to do so), the coupling, would be what your curve shows at around frequencyNASA = 2 GHz, the NASA frequency ?

Photons don't accelerate. No reference required. It is basic. Any theory requiring such condition needs to go.
Challenge your preconceptions, or they will challenge you. - Velik

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