Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1804773 times)

Online Rodal

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Thrust To Power Derivation

I posted the attached derivation the other day. The only response was an off the cuff remark from @deltaMass. I guess what I'm looking for is some discussion on why this is wrong, or not. The algebra is correct, the interpretation is that as the Xmn "resonant" wave propagates down the expanding waveguide, the gradient enhances the thrust. I estimated using Wolfram Alpha's waveguide simulator (using 2 different size waveguides) that if the wavelength expansion follows the taper, and the frequency is very near the cut-off. The resulting thrust to power is several orders of magnitude greater than a photon rocket, over a short distance. If the waveguide is long, then it all reduces to 1/c at the far end. If there is no taper, it reduces to 1/v_phase. Taper adds a gradient that depends on the direction of the taper. In one direction it attenuates, in the other it accelerates.

Let me know what you think.
Todd
I applaud your effort to explain the magnification of thrust over a photon rocket.

My comment on the derivation is that you have to justify how you immediately go into a differential equation where the frequency omega and the wavenumber k are treated as differentials but the cylindrical Bessel function stays constant and unadulterated.

You need to justify the meaning of kdk.  You need to justify how can a cylindrical Bessel function enter into a tapered waveguide: which is a cone.  This is the same approximation that TheTraveller, Notsosureofit and others do ab initio.  It needs to be justified.   I agree that solving the exact solution in terms of Legendre Associated functions and Spherical Bessel functions does not appear feasible in terms of obtaining a closed-form solution, but perhaps you could attempt a perturbation analysis for example instead of jumping right away into a differential equation for a tapered waveguide with Bessel cylindrical functions.

A perturbation solution in terms of small cone half-angle, for example, where the cylinder is the limit geometry for cone half-angle approaching zero.  For small cone angles the solution should be close to a cylindrical Bessel function, but how close does it have to be?

If it is very close, the magnification factor may be negligible, as the magnification factor arises from the cone angle being different from zero.

The perturbation approach also would provide an estimate of the errors involved in the solution (an estimate of the size of the neglected higher order terms).
« Last Edit: 07/25/2015 06:03 PM by Rodal »

Online aero

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@Rodal
Small end cuts for the lateral, small end antenna are here- Go all the way to the bottom, it is a large file and Google takes some time to load it. The big end cuts are at the top, the y-z views are in the middle and the small end cuts are at the bottom. No, I can't guarantee that the lattice is the same for this data as it is for more recent data. The image files, views, are still valid for what it's worth.

https://drive.google.com/file/d/0B1XizxEfB23taGRGU1ozYUNuYTg/view?usp=sharing

That is my recollection. However it is confusing and perhaps not complete WRT the data I have been generating recently for your use.  I suggest that if you can't quickly make sense of the data, that I remove the existing file named csv data in the Yang-Shell folder and regenerate data to your latest requirements for both big end lateral and small end lateral antenna, stored in separate folders. Now that I hopefully have my bash shell file corrected, it should be quick, though I will need to re-run meep to guarantee the same lattice.
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Online Rodal

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Unless I am mistaken, there is only 1 recognized force (besides experimental error) that could account for variance due to orientation in a vacuum: Electromagnetism. Gravity as we understand it is not variable in a 360 degree horizontal rotation...Am I right on this assumption, Doc?
Ha, my message is gone puff.

You rescued it:
Yes, the first thing that comes to mind is electromagnetism, concerning orientation dependence in a horizontal plane, but I think that Sean Carroll and John Baez will use the dependence on orientation as being an experimental artifact arising from the device used to measure the force: they and other skeptics may posit that the measuring device itself was subject to orientation dependence (*) due to purely mechanical reasons and hence that the measured forces are within experimental errors and thus subject to be attacked as noise.

(*) Frobnicat has explained orientation dependence problems with a torque balance, for example, arising from the position of the center of mass.
« Last Edit: 07/25/2015 06:07 PM by Rodal »

Online Rodal

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@Rodal
Small end cuts for the lateral, small end antenna are here- Go all the way to the bottom, it is a large file and Google takes some time to load it. The big end cuts are at the top, the y-z views are in the middle and the small end cuts are at the bottom. No, I can't guarantee that the lattice is the same for this data as it is for more recent data. The image files, views, are still valid for what it's worth.

https://drive.google.com/file/d/0B1XizxEfB23taGRGU1ozYUNuYTg/view?usp=sharing

That is my recollection. However it is confusing and perhaps not complete WRT the data I have been generating recently for your use.  I suggest that if you can't quickly make sense of the data, that I remove the existing file named csv data in the Yang-Shell folder and regenerate data to your latest requirements for both big end lateral and small end lateral antenna, stored in separate folders. Now that I hopefully have my bash shell file corrected, it should be quick, though I will need to re-run meep to guarantee the same lattice.

Yeah, I'm sorry: I tried to make sense out of it but it was just too much work to check those files.  I'm not sure whether they are right or not.  It would be very helpful if you could rerun and label the files as you did with the more recent ones: B for big end, S for small end, etc.  Your latest labeling is very good and intuitive. 
« Last Edit: 07/25/2015 06:05 PM by Rodal »

Online aero

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@Rodal
Small end cuts for the lateral, small end antenna are here- Go all the way to the bottom, it is a large file and Google takes some time to load it. The big end cuts are at the top, the y-z views are in the middle and the small end cuts are at the bottom. No, I can't guarantee that the lattice is the same for this data as it is for more recent data. The image files, views, are still valid for what it's worth.

https://drive.google.com/file/d/0B1XizxEfB23taGRGU1ozYUNuYTg/view?usp=sharing

That is my recollection. However it is confusing and perhaps not complete WRT the data I have been generating recently for your use.  I suggest that if you can't quickly make sense of the data, that I remove the existing file named csv data in the Yang-Shell folder and regenerate data to your latest requirements for both big end lateral and small end lateral antenna, stored in separate folders. Now that I hopefully have my bash shell file corrected, it should be quick, though I will need to re-run meep to guarantee the same lattice.

Yeah, I'm sorry: I tried to make sense out of it but it was just too much work to check those files.  I'm not sure whether they are right or not.  It would be very helpful if you could rerun and label the files as you did with the more recent ones: B for big end, S for small end, etc.  Your latest labeling is very good and intuitive.

Ok, I'll do that. It will be a few hours until its uploaded.
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Offline dustinthewind

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

space time is only flat where there is no gravity.  This is why light follows a curved path in the presence of a gravitational well.  http://www.math.brown.edu/~banchoff/STG/ma8/papers/dstanke/Project/curved_space.html

If you can artificially engineer a gravitational well of sorts, "maybe not exactly gravity but mimic it at a specific frequency", then you might be able to effectively curve space and time/energy at that particular wavelength. 
« Last Edit: 07/25/2015 06:46 PM by dustinthewind »

Offline birchoff

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Just a heads up you guys dont have to wait till tuesday to get tajmar's paper. its availabe from AIAA's archive for 25 bucks. Working my way through it and his other papers....

Offline X_RaY

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

space time is only flat where there is no gravity.  This is why light follows a curved path in the presence of a gravitational well.  http://www.math.brown.edu/~banchoff/STG/ma8/papers/dstanke/Project/curved_space.html

If you can artificially engineer a gravitational well of sorts, "maybe not exactly gravity but mimic it at a specific frequency", then you might be able to effectively curve space and time/energy at that particular wavelength.
Every kind of energy in a given volume leads to deformed spacetime. The question is, is it a the dominant effect inside the frustum to generate the measured thrust. IMHO the Coupling of the EM field and the gravitative would be strong enough the measure that in other experiments also.

Offline deltaMass

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

space time is only flat where there is no gravity.  This is why light follows a curved path in the presence of a gravitational well.  http://www.math.brown.edu/~banchoff/STG/ma8/papers/dstanke/Project/curved_space.html

If you can artificially engineer a gravitational well of sorts, "maybe not exactly gravity but mimic it at a specific frequency", then you might be able to effectively curve space and time/energy at that particular wavelength.
Think about what you just said. What "gravity simulation" corresponds to a mirror reflecting light?  Did it curve space-time?

No, it did not.

Offline wembley

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I'm concerned with the headline "EmDrive could reach Pluto in 18 months" being so at odds with what I heard was Prof. Tajmar's experimental data he had obtained a couple of months ago:


Well, it might be that Prof Tajmar's setup had rather a low Q value, but this was not important as his test apparatus went down to sub-micronewton measurement.

Offline rfmwguy

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Just a heads up you guys dont have to wait till tuesday to get tajmar's paper. its availabe from AIAA's archive for 25 bucks. Working my way through it and his other papers....
Excellent! Questions abound, obviously. Good luck digging thru it. While reposting may not be cool until after the presentation, summation is welcomed.


Offline rfmwguy

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Unless I am mistaken, there is only 1 recognized force (besides experimental error) that could account for variance due to orientation in a vacuum: Electromagnetism. Gravity as we understand it is not variable in a 360 degree horizontal rotation...Am I right on this assumption, Doc?
Ha, my message is gone puff.

You rescued it:
Yes, the first thing that comes to mind is electromagnetism, concerning orientation dependence in a horizontal plane, but I think that Sean Carroll and John Baez will use the dependence on orientation as being an experimental artifact arising from the device used to measure the force: they and other skeptics may posit that the measuring device itself was subject to orientation dependence (*) due to purely mechanical reasons and hence that the measured forces are within experimental errors and thus subject to be attacked as noise.

(*) Frobnicat has explained orientation dependence problems with a torque balance, for example, arising from the position of the center of mass.
Thanks Doc...very possible test aparatus itself is subject to magnetic orientation. Which begs the question why not rotate the frustum only. May not be possible, but think it would be the logical choice to avoid induced variables.

Offline dustinthewind

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

space time is only flat where there is no gravity.  This is why light follows a curved path in the presence of a gravitational well.  http://www.math.brown.edu/~banchoff/STG/ma8/papers/dstanke/Project/curved_space.html

If you can artificially engineer a gravitational well of sorts, "maybe not exactly gravity but mimic it at a specific frequency", then you might be able to effectively curve space and time/energy at that particular wavelength.
Think about what you just said. What "gravity simulation" corresponds to a mirror reflecting light?  Did it curve space-time?

No, it did not.
I was mostly just addressing what curved space was.

I did mention about the engineering and I think that was in relation to Tod's idea.  That being I thought for instance the idea Tod was working on was that one end of the frustum was slowing light down.  Light slowing down in a gravitational well but in this case only working at wavelengths near the cut off diameter of the frustum (suggested as a black hole?). 

I guess I was paralleling this to slowing down light and increasing its effective mass.  Here is a link and a quote:
http://www.physicscentral.com/explore/action/light.cfm "Itís possible to slow light down by making it interact with matter and, in a sense, converting photons to something with mass. "

I am not sure the idea parallels all that well.   Maybe the light could be interacting with plasma I suppose but maybe that's a stretch. 

A possibly related link here: https://sites.google.com/site/oferfirst/ quote: "These so-called dark-state polaritons exhibit several unique properties: their group velocity is much smaller than the speed of light in vacuum owing to their stationary atomic components; their group-velocity dispersion endows them with an effective mass; and their absorption (scattering) is suppressed despite the light being resonant with the atomic transitions."
« Last Edit: 07/25/2015 07:56 PM by dustinthewind »

Online Rodal

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Just a heads up you guys dont have to wait till tuesday to get tajmar's paper. its availabe from AIAA's archive for 25 bucks. Working my way through it and his other papers....

Please let us know whether you see anything different from what I posted.  Thanks

Offline Star One

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Just a heads up you guys dont have to wait till tuesday to get tajmar's paper. its availabe from AIAA's archive for 25 bucks. Working my way through it and his other papers....
Excellent! Questions abound, obviously. Good luck digging thru it. While reposting may not be cool until after the presentation, summation is welcomed.

Wouldn't even a summation be rather rude until he's presented it himself?

Offline birchoff

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Just a heads up you guys dont have to wait till tuesday to get tajmar's paper. its availabe from AIAA's archive for 25 bucks. Working my way through it and his other papers....
Excellent! Questions abound, obviously. Good luck digging thru it. While reposting may not be cool until after the presentation, summation is welcomed.

How is InputPower determiend for the http://emdrive.wiki/Experimental_Results table. Is it the power fed to the RF source? or the power leaving the RF source being fed to the cavity?

Online Rodal

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Unless I am mistaken, there is only 1 recognized force (besides experimental error) that could account for variance due to orientation in a vacuum: Electromagnetism. Gravity as we understand it is not variable in a 360 degree horizontal rotation...Am I right on this assumption, Doc?
Ha, my message is gone puff.

You rescued it:
Yes, the first thing that comes to mind is electromagnetism, concerning orientation dependence in a horizontal plane, but I think that Sean Carroll and John Baez will use the dependence on orientation as being an experimental artifact arising from the device used to measure the force: they and other skeptics may posit that the measuring device itself was subject to orientation dependence (*) due to purely mechanical reasons and hence that the measured forces are within experimental errors and thus subject to be attacked as noise.

(*) Frobnicat has explained orientation dependence problems with a torque balance, for example, arising from the position of the center of mass.
Thanks Doc...very possible test aparatus itself is subject to magnetic orientation. Which begs the question why not rotate the frustum only. May not be possible, but think it would be the logical choice to avoid induced variables.
Yes that's what Tajmar did: he tested the EM Drive in different orientations.

Online Rodal

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I'm concerned with the headline "EmDrive could reach Pluto in 18 months" being so at odds with what I heard was Prof. Tajmar's experimental data he had obtained a couple of months ago:


Well, it might be that Prof Tajmar's setup had rather a low Q value, but this was not important as his test apparatus went down to sub-micronewton measurement.
Did Tajmar ever say that his experimental results can be extrapolated to reach Pluto in 18 months using an EM Drive as the means of propulsion?
« Last Edit: 07/25/2015 08:19 PM by Rodal »

Offline birchoff

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I'm concerned with the headline "EmDrive could reach Pluto in 18 months" being so at odds with what I heard was Prof. Tajmar's experimental data he had obtained a couple of months ago:


Well, it might be that Prof Tajmar's setup had rather a low Q value, but this was not important as his test apparatus went down to sub-micronewton measurement.
Did Tajmar ever say that his experimental results can be extrapolated to reach Pluto in 18 months?

Not in the conference paper

Offline Star One

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That title was chosen I reckon because people searching for news on Pluto would get that article coming up as well.
« Last Edit: 07/25/2015 07:57 PM by Star One »

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