Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1796328 times)

Offline SeeShells

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Regarding resonant modes in the frustum. Would there still be resonant modes if;

1. the frustum were open on the big end only?

2. the frustum were open on both ends?

IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?

If it's closed at the small end, it should still support odd harmonics of p modes. Correct?

Thank you!
Todd
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Shell

Offline rfcavity

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Regarding resonant modes in the frustum. Would there still be resonant modes if;

1. the frustum were open on the big end only?

2. the frustum were open on both ends?

IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?

If it's closed at the small end, it should still support odd harmonics of p modes. Correct?

Thank you!
Todd

It would support TExx modes but they would be travelling, out the end of the device. It wouldn't be a energy store like normal closed cavities, but simply an antenna.

https://en.wikipedia.org/wiki/Horn_antenna

Offline SeeShells

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Regarding resonant modes in the frustum. Would there still be resonant modes if;

1. the frustum were open on the big end only?

2. the frustum were open on both ends?

IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?

If it's closed at the small end, it should still support odd harmonics of p modes. Correct?

Thank you!
Todd

It would support TExx modes but they would be travelling, out the end of the device. It wouldn't be a energy store like normal closed cavities, but simply an antenna.

https://en.wikipedia.org/wiki/Horn_antenna
So even though the rectagon wire dimensions are a multiple of the 2.45 ghz wavelength  the waves would still pass? I know since the magnetron is such a wide band emitter you're probably right.
Shell

Online WarpTech

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Regarding resonant modes in the frustum. Would there still be resonant modes if;

1. the frustum were open on the big end only?

2. the frustum were open on both ends?

IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?

If it's closed at the small end, it should still support odd harmonics of p modes. Correct?

Thank you!
Todd

It would support TExx modes but they would be travelling, out the end of the device. It wouldn't be a energy store like normal closed cavities, but simply an antenna.

https://en.wikipedia.org/wiki/Horn_antenna

Is it possible in a cylinder (not a cone) to have a TExx mode that does not travel? It just resonates at one particular spot in the cylinder? Since this resonant mode is radial, not axial, I don't see why it would have any reason to move in either direction. c is in the radial direction. v in the axial direction should be 0.
Todd

Offline cej

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Here's a summary of how I interpret TheTraveller's explanation of Shawyer's claims, as I have gathered from roughly the last 15 pages of this thread by comments made by TheTraveller, WarpTech, hhexo, frobnicat, and others.

There has been much confusion over the EM Drive, and I believe a large factor contributing to this is Shawyer's tendency to lump what are actually three separate claims together. It makes sense for a sales pitch, but it leads to bad science.

Claim 1. The EM Drive is an inertial ratchet; it creates NO THRUST on its own.

It opposes change in momentum in one direction and does not oppose change in momentum in the opposite direction (it might even "encourage" this by making the drive's mass appear to be smaller in this direction). Unlike claiming that the drive alone creates thrust, this claim seems more likely to satisfy conservation of momentum.

Inertial ratchets are already studied in other contexts, e.g. to separate microscopic particles of varying mass. The novelty of this claim is that the EM Drive is magnitudes larger in size and seems to operate in a fundamentally different way.

Claim 2. An inertial ratchet can be made to do work: net thrust.

We already know that microscopic inertial ratchets can do work: see Brownian motors. The question here is how a macroscopic inertial ratchet can do work. Here are some possibilities I can think of:

1. Small vibrations (heat) that are external to the drive's frustum: like a Brownian motor. An inertial ratchet could become buoyant by inducing its own pressure gradient: particles would impart more momentum on the large end than the small end.
2. Attaching the EM Drive to an oscillating spring with a mass at the other end (see frobnicat's comment).
3. QV fluctuations / Casimir effect? Unlike the Q-Thruster, an inertial ratchet would not expel a virtual plasma, but it could become buoyant among virtual particles.
4. By opposing gravity to some degree, it might make traditional forms of propulsion more efficient?

To my knowledge, TheTraveller has only proposed #1 and WarpTech has argued against #4 being viable. The Wikipedia entry for Brownian ratchets also discusses why such devices are not free energy machines. It is not yet clear to me what the corresponding argument would be for the EM Drive.

Claim 3. The net thrust that can be generated by an inertial ratchet like the EM Drive (via Claim 2) leads to more efficient space travel than a photon rocket.


The reason why I am emphasizing three different claims is that I think this has a significant impact on how the experiments to validate or refute Shawyer's work should be conducted: these claims need to be tested individually. If this inertial ratchet interpretation is true, then it means that vibrations/noise have to be carefully understood and accounted for, but not necessarily eliminated. It would be no surprise that the experiments up to now have had inconsistent results because they attempt test claims 1 & 2 together by measuring thrust directly, but do not correctly distinguish between Claim 2 and noise.

Even if the EM Drive fails to pan out as a means of space travel, succeeding in any one of these 3 claims would be a useful scientific contribution.

Offline rfmwguy

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The em spectrum in space, ignore atmospheric line, galactic and quantum freqs have exponentially higher values...measured in temp K. The is much less to manipulate from 1-50 ghz...so cosmic soup is radio waves or near 1 thz. This chart is for seti types...dip is called the hydrogen hole. If I were scaling up the coke bottle experiment, would select nothing in the 1-50 ghz spectrum...interesting thought experiment.

http://www.setileague.org/photos/miscpix/waterhol.gif

Offline smartcat

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I used to be not just skeptical, but, Ahem, hostile, to this idea of superluminal transmission, because of violation of causality, and the appearance that a tachyonic telephone could be constructed.

However, upon examining the papers in detail, there is no doubt in my mind that it is impossible to send information using this superluminal transmission.  It has been shown a number of times, by different authors that this is impossible, just as it is impossible to use the coherence phenomenon of instantaneous action at a distance to send information.  This is precluded by quantum mechanics, in both cases.  There is nothing deterministic about the superluminal evanescent wave transmission that can be used to send any information superluminally, as what will be received superluminally will be scrambled up randomly in a non-deterministic way.  The signal received at the other end would be incomprehensible and contain no information.

Hence I no longer have any problem with this type of superluminal action.  Besides the impossibility to use it to send information, the superluminal aspect is restricted to the group velocity and not to the phase velocity, so one has to be careful about the physical interpretation of this superluminal effect.

I share the same feelings about "backwards in time", so I appreciate your soothing commentary  :)

Offline TheTraveller

I have advance & very agressive prostate cancer. Prostate has been removed along with a 9cm dia cancer mass. Seems they didnt get it all, so I'm back in hospital.

Haven't read the forum for days & likely will not for 3-5 more days.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline deltaMass

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That's awful. Get well soon!

Offline Rodal

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Regarding resonant modes in the frustum. Would there still be resonant modes if;

1. the frustum were open on the big end only?

2. the frustum were open on both ends?

IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?

If it's closed at the small end, it should still support odd harmonics of p modes. Correct?

Thank you!
Todd
Todd,

This is another case where both size, and frequency do matter.

Even without any hole, both in a cylinder and in a truncated cone, modes that are high in azimuthal quantum number "m": for  TEmnp with high m have no central field.   The higher m, the more they start to look like a whispering-gallery mode. 

Pictures of whispering-gallery modes:



This is a picture of London's St.Paul's cathedral, which is associated with the whispering-gallery phenomenon.  Climb 259 steps inside the dome, stand on one side of the circular gallery and talk very quietly and your speech can be heard quite clearly on the other side some 30m away.  You can see deltaMass at the Cathedral whispering something about conservation of energy to frobnicat who is at the opposite end of the Cathedral listening to deltaMass musings:





you will notice that there is a hole in the center of the whispering gallery.

This picture shows the quadrapole for mode TM212 used by NASA Eagleworks, for the electric field:



and for the magnetic field:



You can see that even this low mode will support a small hole through the middle of the big base without affecting it.

See for example the octopole TE411 for NASA's Brady cavity in the attachment below, which will support a much larger hole.

As "m" increases, the hole supported in the middle can be bigger and bigger.

For these modes, you can actually make a hole through the central portion where there is no field, and it won't make a difference.

As "m" increases the mode looks more and more like a ring.  In the limit you can still have resonance with very high "m" and a very thin ring.

When the hole is such that it is flash with the internal surface of the cylinder, "m" is infinite and you have no resonance.

Ditto for the big diameter in a truncated cone: you can have resonance at ever increasing "m" until the hole is flash with the interior surface, at which point m is infinite and you have no more resonance.

////////////////

You can also have resonance with holes on both ends, as long as they are not flash with interior surface.  The resonance will be at a higher frequency as "m" increases.   The big diameter hole size is what matters most.  When the big diameter hole is flash with the interior surface "m" is infinite, the natural frequency is infinite and you no longer have resonance.

//////////////

To answer your unnumbered question requires more wording and I don't have a picture to explain it at the moment. So maybe tomorrow.

« Last Edit: 06/27/2015 01:03 AM by Rodal »

Offline hhexo

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Moreover the acoustic Helmholtz resonance is the exact acoustic analogue of the microwave cavity Helmholtz resonance (except for the fact that the number of gas molecules is constant while the number of photons is not constant, and the fact that the photon gas has different temperature dependence).

The guitar string is not as good an analogue of the the microwave cavity Helmholtz resonance.

Hm... so you're suggesting we model the cavity as a Helmholtz resonator because the EmDrive cavity may not be totally sealed after all.
That's fine, but it changes the problem from what we've been working on so far. The initial claim was that the cavity is sealed.

Meanwhile I've been looking for data about variable thickness resonating string, and it turns out a lot of people researched the matter starting with Krein in the 1950s. If anyone's interested, this paper has an extensive bibliography with a lot of references:
http://arxiv.org/pdf/1006.2730v1.pdf

Also this book seems very useful for a lot of situations with acoustic waves:
https://books.google.co.uk/books?id=hmPSBQAAQBAJ

Offline Rodal

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I have advance & very agressive prostate cancer. Prostate has been removed along with a 9cm dia cancer mass. Seems they didnt get it all, so I'm back in hospital.

Haven't read the forum for days & likely will not for 3-5 more days.

Life after cancer: Eat, travel, read, laugh, have fun,  dance, exercise, work, run, a Scotch on the rocks, play, write, swim, run, sleep, ride, flirt, celebrate, love, smile, hottub, cook, a fine cigar, hug, a working EM Drive, yes, it is all worth fighting for.

Keep walking and let cancer be the shadow behind you that will disappear and be forgotten as time goes by.
« Last Edit: 06/27/2015 12:31 AM by Rodal »

Offline SeeShells

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I have advance & very agressive prostate cancer. Prostate has been removed along with a 9cm dia cancer mass. Seems they didnt get it all, so I'm back in hospital.

Haven't read the forum for days & likely will not for 3-5 more days.

MY thoughts and prayers to a quick recovery.

Shell

Online WarpTech

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...
1. Small vibrations (heat) that are external to the drive's frustum: like a Brownian motor. An inertial ratchet could become buoyant by inducing its own pressure gradient: particles would impart more momentum on the large end than the small end.
...

Could you elaborate on this "buoyant" effect and provide some references?

It is interesting because in my model of QG, a particle like a proton behaves like a "bag" of zero point fluctuations that act as the "driving" function for the harmonic oscillations. Radiation reaction acts as a damping function and the two are in equilibrium. Gravity arises as a broken symmetry. If you amplify the ZPF in the correct bandwidth, it will inflate the bag, making it buoyant in a gravitational field.  It's very counter-intuitive that adding energy reduces the energy density, but that is exactly what happens, just like a hot air balloon. Gravity obeys PV~T. Adding energy to the ZPF inflates the oscillator by dx and the volume of the probability density increases by dx^3, lowering the total Energy density. This is "Exotic Matter", it is the opposite effect of gravitational time dilation and length contraction.

Energy => E/sqrt(K)
Length => L/sqrt(K)

Where K is the refractive index of the vacuum in a gravitational field. If K < 1, Energy goes up, while Energy density goes down, which is "equivalent to" adding negative energy density to a positive energy density.
Todd

Offline aero

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Ok guys and gals, I hate to admit it but I'm confused again. I just re-ran rfmwguy's cavity and saved the ex, ey, and ez field components as well as the hy component. (It only took about 10 minutes so no time wasted) But now I am confused about what you all want to see. Had I output the hx and hz components also, (would have been no/little additional time penalty) then there would be 18 possible sets of 312 time slices. x, y, z view of each of 6 components of the EM field as follows.

1 - x, y, and z view of the Ex component
2 - x, y, and z view of the Ey component
3 - x, y, and z view of the Ez component
4 - x, y, and z view of the Hx component
5 - x, y, and z view of the Hy component
6 - x, y, and z view of the Hz component

Its not a big deal to make these data sets but uploading them takes time and can you make sense of that large number of files? I'll make them all and upload them all, as long as Google will give me the storage space but will all that data be useful?

I guess I'll just take the time to upload all 18 views, at least this once. That way we'll have something to look at to see if we really need them all. That seems to me to be the best answer to my confusion. Especially because I really want to know what resonance mode this is.
« Last Edit: 06/27/2015 01:18 AM by aero »
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Offline rfmwguy

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Ok guys and gals, I hate to admit it but I'm confused again. I just re-ran rfmwguy's cavity and saved the ex, ey, and ez field components as well as the hy component. (It only took about 10 minutes so no time wasted) But now I am confused about what you all want to see. Had I output the hx and hz components also, (would have been no/little additional time penalty) then there would be 18 possible sets of 312 time slices. x, y, z view of each of 6 components of the EM field as follows.

1 - x, y, and z view of the Ex component
2 - x, y, and z view of the Ey component
3 - x, y, and z view of the Ez component
4 - x, y, and z view of the Hx component
5 - x, y, and z view of the Hy component
6 - x, y, and z view of the Hz component

Its not a big deal to make these data sets but uploading them takes time and can you make sense of that large number of files? I'll make them all and upload them all, as long as Google will give me the storage space but will all that data be useful?
Aero I really appreciate ur efforts. At this point nothing else needs to be done. We have resonance at both lengths, I have a 100% chance of picking the right one. Thanks again buddy...

Offline Rodal

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Ok guys and gals, I hate to admit it but I'm confused again. I just re-ran rfmwguy's cavity and saved the ex, ey, and ez field components as well as the hy component. (It only took about 10 minutes so no time wasted) But now I am confused about what you all want to see. Had I output the hx and hz components also, (would have been no/little additional time penalty) then there would be 18 possible sets of 312 time slices. x, y, z view of each of 6 components of the EM field as follows.

1 - x, y, and z view of the Ex component
2 - x, y, and z view of the Ey component
3 - x, y, and z view of the Ez component
4 - x, y, and z view of the Hx component
5 - x, y, and z view of the Hy component
6 - x, y, and z view of the Hz component

Its not a big deal to make these data sets but uploading them takes time and can you make sense of that large number of files? I'll make them all and upload them all, as long as Google will give me the storage space but will all that data be useful?
I have routinely outputted all those components for my own purposes, in addition to the Sqrt of their sums for E and B, as well as the Poynting vector fields, and I have ocassionally also plotted the energy densities and the divergence of the Poynting vector field.  It is a 3D problem with both electric and magnetic fields.  It is only by looking at all the components that I gained an understanding of what is going on: first in my model and once I accomplished that, to understand what is going on physically.  To me, geometrical, visual understanding is fundamental in understanding the behavior of electromagnetic 3D fields.

Such understanding has come useful a number of times, not just for the EM Drive, for example this last time in answering Todd's question about the effect of openings at both ends.  And it has also been useful for other problems that have nothing at all to do with the EM Drive.

As to whether it is worthwhile for you to use your time to download them in the Google Drive, only you can be a judge of that :)

If you do download them.  Thanks for your efforts.  A few of the people in the thread, including me, will appreciate them.

Those that do not care, are not forced to look at them, any more than they are forced to read any messages on these threads :)
« Last Edit: 06/27/2015 01:52 AM by Rodal »

Offline aero

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Yes, there in lies the problem. Without looking at what I'm doing how can I learn from it?
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Offline Rodal

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Yes, there in lies the problem. Without looking at what I'm doing how can I learn from it?
Electromagnetic cavities have been used to measure, very accurately, the speed of light, they are used routinely at particle accelerators like CERN, they are used to look for Dark Matter (axions), they are used for optical, quantum mechanics, nanotechnology (nanocavities) and many other purposes.

So no matter what other people may think of this endeavor, our time modeling these electromagnetic modes in these cavities, has not been wasted,  there are much worst ways to use one's time.  It will be useful for other things, like everything in life, as Feynman said the amazing usefulness of math to describe our Universe....There are countless other problems you can use Meep for :)
« Last Edit: 06/27/2015 02:53 AM by Rodal »

Offline Notsosureofit

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Yup!  Old dog learns new tricks on almost every page !

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