Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1805415 times)

Offline Rodal

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With all the fooling I've done with meep recently, I discovered a new trick. I can show different views of slices of a 4-D data set. Here is the closed cavity with the Gaussian drive frequency centered at 2.253 GHz though Meep/Harminv says it resonates at 2.343 GHz. These are all at timestep 1420. What mode is this illustrated.

Shown are big end, center and small end slices "x", and y and z axial slices.
What is the reason for the elliptical shape of the electromagnetic field in the circular cross-section views?



The boundary conditions should be perfectly circular for a truncated cone. 
Therefore one expects a circularly symmetric electromagnetic field instead of this surprising elliptical electromagnetic field.
There appears to be an asymmetry in the circular cross section of your model responsible for this ellipse.
What feature of the model does the major and minor axes of the ellipse align with?

They seem to align with the cut-outs your model has at 0 , 90, 180 and 270 degrees.

What is the asymmetry responsible for the major axis of the ellipse aligning itself with the cut-outs at 0 and 180 degrees instead of 90 and 270 degrees ?

Or, in other words, why should there be an ellipse instead of a rhombus-like shape with symmetry every 90 degrees (the angle between the cut-outs) instead of every 180 degrees?
« Last Edit: 06/15/2015 09:50 AM by Rodal »

Offline TheTraveller

I have a more general question about the evolution of all this research.

According to Shawyer, we have to increase the Q factor up to billions in order to scale the thrust (with the help of superconducting cavities). Hence Shawyer envisioned not only thrusters for spaceprobes and spaceships, but also "lift engines" here on Earth, with -literally speaking- flyings cars and the like around the corner.

If Shawyer is wrong regarding the scale law of thrust vs Q (and the lack of published experimental results of superconducting EmDrives up to now would bolster this pessimistic view), but the EmDrive is still real, would the thrust stay very low even with high power, restricting the applications to space-based thrusters only?

If an alternate model is right, for example Todd's: wavelength attenuation produces thrust in a refractive index gradient, due to an energy density unevenly distributed thanks to a proper asymmetric geometry aka the frustum: the thrust is then maximized while increasing the attenuation, and not increasing the energy stored into the cavity via the Q factor (the "tug of war" between attenuated energy and stored energy).

If this model is right, according to you WarpTech, would the max. thrust be caped well below one gee, or do you think your model could enable lift-engines in Earth gravity field, with enough power on board? (powerful still cheap and light energy source, I'm not speaking of fitting a nuclear power plant in a car…)

May I suggest dealing with really high Q cavities is REALLY hard. Narrow band Rf needs to spot on, massive cavity detune with the slightest acceleration or the slightest temp change. Shawyer has revealed enough publically, that to me, he knows the issues and is working them.

His next peer reviewed paper on the SC EM Drive that has been developed with partners is due to be released in 2015. Expect there will be performance data in the paper. I keep watching the IAC 2015 site for his paper to be listed for the mid Oct 2015 event.

https://iafastro.directory/iac/browse/IAC-15/catalog-technical-programme#sec.C4 subsection (C4.8. Advanced and Combined Propulsion Systems)
« Last Edit: 06/15/2015 10:12 AM by TheTraveller »
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Offline Chris Bergin

Remember to "attach" images, not embed them.

Only use the embed [img ] code when the image is small. Anything wider than the width of the thread makes the page unreadable as it stretches it (we're working on auto reduction, but different browsers work different ways, etc.)

Sounds like you're having interesting fun on here, so as you were.....
« Last Edit: 06/15/2015 01:34 PM by Chris Bergin »

Offline francesco nicoli

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we profanes are in need of an update in a while! :) I see lots of work is going on and I am impressed on the role this forum is having, but unfortunately I can't follow much of developments...how the new experiments are going?

Offline Rodal

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WE HAVE RESONANCE!

Attached is TE01x analysis for the Baby EM Drive.

With flat end plates, length resonance can occur anywhere from

the min spacing of:

1) centre of big end plate to centre of small end plate

to max spacing of :

2) outer edge big end plate to outer edge small end plate.

As you can see TE013 generates a length resonance ring just inside the maximal outer edge spacing.

For the Baby EM Drive, there are several resonance modes. Which is driven depends on excitation method, antenna placement and antenna design.

Spreadsheet attached.

I get TE013 for Baby EM Drive with my exact solution at a frequency of 24.34 GHz.  There are many other natural frequencies close by though, so there will be participation from other modes as well.

I imagine that it is not a coincidence that TE013 is the natural frequency that matches their excitation frequency.  TE01p has been the preferred mode of excitation of both Shawyer for the Demo and the Flight Thruster, and by Prof. Yang, and it was also the mode shape that gave the highest Force/InputPower for NASA Eagleworks  (see http://emdrive.wiki/Experimental_Results ), so it looks to me that the fellows at Aachen calculated this before they machined Baby EM Drive.  These guys did their homework  ;)

The end plates of the Baby EM Drive are flat, so a lot of close frequencies should obtain resonance. For your 24.34GHz spherical end plate case, the results are attached, which show resonance a bit further away from the side wall but not at the minimal centre to centre end plate spacing.

Would expect thrust to be MUCH greater with spherical and plates as much more (should be all of it) end plate surface area is working at resonance as against a thin ring (very small area) at each end plate.

I calculated the natural frequency of the EM Drive based on the formula for a perfect cylinder ( https://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity ) (using the cylindrical Bessel functions that you use in your spreadsheet), based on the Mean diameter (the average of the small and big diameters of the Baby EM Drive),  I obtained the following frequency for TE013 for perfectly flat ends:

24.41 GHz

which compares to the value I obtained using my exact solution:

24.34 GHz

The difference between these values is only

0.29%

Suggestion:  this difference (0.29%) is very small, particularly compared with the uncertainties of:

--precision of the dimensional measurements of the Baby EM Drive
--precision in machining the Baby EM Drive: precision in radial runout, precision in concentricity, precision in longitudinal runout
--precision in excitation frequencies of the Baby EM Drive by the radar they are using


Therefore undue emphasis on such small differences and undue emphasis on a large number of digits for precision may be unwarranted at this point in time, particularly when using a spreadsheet based on using cylindrical Bessel functions that are known to apply only for cylinders and that are not able to satisfy the boundary conditions of a truncated cone.

The most that can be confidently said is that the Baby EM Drive if excited at 24 to 25 GHz will experience a number of mode shapes with different participation factors, and that TE013 is one of the main mode shapes expected to participate.  To be more precise would require a spectrum analysis of the truncated cone, taking into account all the frequencies excited by the radar used in the Baby EM Drive as well as knowing more about the precision of their geometrical measurement and the precision of their machining the Baby EM Drive.
« Last Edit: 06/15/2015 01:39 PM by Rodal »

Offline Rodal

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we profanes are in need of an update in a while! :) I see lots of work is going on and I am impressed on the role this forum is having, but unfortunately I can't follow much of developments...how the new experiments are going?

Hi   :)

IMHO the main topics of discussion at the moment are:

EXPERIMENTAL: the breakthrough in miniaturization: the Baby EM Drive with 1/10 the geometrical dimensions of other EM Drives, running at 10 times higher frequency: 24 GHz, by two fellows in Aachen, Germany.  See:  https://hackaday.io/project/5596-em-drive

The test inside the transparent jar (NOT a vacuum chamber) displays gyroscopic oscillations ("nutation") and decay with time that almost mask the response of the EM Drive (still, a small effect on the rotation speed appears to be there).  A subsequent test of the EM Drive in a torsional hanging pendulum was the subject of even more uncertainty as the magnitude of spurious oscillations completely overwhelm any possible signal response.







THEORETICAL: Todd "WarpTech" theory based on geometrical attenuation: that due to the tapering geometry of the EM Drive, standing waves are cut-off and become evanescent waves near the small base of the truncated cone.   Evanescent waves are known to carry momentum (unlike standing waves).  The problem is that the evanescent waves are inside the EM Drive and this still appears to break conservation of momentum unless they are able to leak out somehow (in which case it has to be shown how can they leak out in such a way as to exceed the performance of a photon rocket).

This discussion has also been useful concerning optimization of the shape of an EM Drive to maximize thrust output.
It points (pun intended  ;) ) towards a more pointy cone, with a smaller diameter base (compared to the big base) than used up to now.  All the theories (Todd's attenuation theory, Shawyer's, McCulloch's, Yang's, Notsosureofit) point in the same geometrical direction. 

EDIT: Todd's attenuation theory differs in one very important aspect: while all the other theories predict thrust to linearly increase with quality factor of resonance ("Q"), Todd's attenuation theory shows a "tug of war" between Q and attenuation (cut-off of natural frequencies), and maximum thrust should take place at a yet unknown compromise between the two.







DATABASE: EM DRIVE wiki. The information in the EM Drive wiki continues to expand.  We now have a very extensive and useful table of EM Drive experiments with lots of annotated information:  http://emdrive.wiki/Experimental_Results

and a page for independent replications and building of new EM Drives:

http://emdrive.wiki/Building
« Last Edit: 06/15/2015 02:07 PM by Rodal »

Offline WarpTech

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I have a more general question about the evolution of all this research.

According to Shawyer, we have to increase the Q factor up to billions in order to scale the thrust (with the help of superconducting cavities). Hence Shawyer envisioned not only thrusters for spaceprobes and spaceships, but also "lift engines" here on Earth, with -literally speaking- flyings cars and the like around the corner.

If Shawyer is wrong regarding the scale law of thrust vs Q (and the lack of published experimental results of superconducting EmDrives up to now would bolster this pessimistic view), but the EmDrive is still real, would the thrust stay very low even with high power, restricting the applications to space-based thrusters only?

If an alternate model is right, for example Todd's: wavelength attenuation produces thrust in a refractive index gradient, due to an energy density unevenly distributed thanks to a proper asymmetric geometry aka the frustum: the thrust is then maximized while increasing the attenuation, and not increasing the energy stored into the cavity via the Q factor (the "tug of war" between attenuated energy and stored energy).

If this model is right, according to you WarpTech, would the max. thrust be caped well below one gee, or do you think your model could enable lift-engines in Earth gravity field, with enough power on board? (powerful still cheap and light energy source, I'm not speaking of fitting a nuclear power plant in a car…)

It's difficult to answer. Going by Shawyer's and Nasa's data, I'd say it's a very long shot of scaling it, but going by Yang's it seems more likely.

The Power input is the rate of change in work "W". It results in doing work on the field via the Poynting vector, and also -J*E, which is the current density flowing in the frustum conductors. So look at E and look at J and see where it can be maximized.

IMO, the frustum "should" exert thrust ONLY when charging or discharging. It's should not work when it's at equilibrium with a constant Q value, no matter how high it is.

One question on my mind is, if the Center of Mass (CM) could be moving because the mass of the field dissipates or is attenuated. One or the other or both, it's equivalent to expelling the field out the back. The CM may move forward, then loose mass, before it can oscillate and cause a back reaction, back to where it started. So it "walks" forward, either gaining or losing mass on each step. If the CM is held at constant mass, nothing should happen.

Todd
« Last Edit: 06/15/2015 02:16 PM by WarpTech »

Offline Rodal

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I have added Baby EM Drive to the list of experiments.  http://emdrive.wiki/Experimental_Results

The geometry of Baby EM Drive is essentially the geometry of NASA's truncated cone, scaled down by 1/10 so that it can resonate at 10 times higher frequency in a fundamental mode.  The cone angle is very close to NASA's truncated cone.  Small differences in geometry were carried out (apparently not by chance but by judicious choice based on numerical analysis) so that Baby EM Drive would resonate in mode shape TE013, instead of mode TM212 chosen by NASA for most of their experiments.  TE01p is a transverse electric mode shape with a magnetic axial field that is known to produce a large amplitude or response, and this has been confirmed by the fact that all researchers: Shawyer, Yang and NASA have reported the largest force/InputPower when using this mode shape.

The force entries in the experimental chart remain to be filled until they report a meaningful force measurement for Baby EM Drive.
« Last Edit: 06/15/2015 02:27 PM by Rodal »

Offline TheTraveller

.....
I calculated the natural frequency of the EM Drive based on the formula for a perfect cylinder ( https://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity ) (using the cylindrical Bessel functions that you use in your spreadsheet), based on the Mean diameter (the average of the small and big diameters of the Baby EM Drive),  I obtained the following frequency for TE013 for perfectly flat ends:

24.41 GHz

which compares to the value I obtained using my exact solution:

24.34 GHz
......

With respect that is not now effective guide wavelength is calculated. Roger Shawyer told me how to do it and I shared this here several times. It is in my SS.

The effective guide wavelength is not based on the average of the 2 end plate diameter. It is the numerically integrated value of 10,000 diameters (well I use 10,000, could be more, could be less) including and in between the plates.

For the Baby EMD the guide wavelength for the mean/average diameter is = 0.016501. The numerically integrated effective guide wavelength is = 0.018224, which is why your resonance is too high as your effective guide wavelength is too small.

Have attached the latest version of the SS, which has a new feature.

"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
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Offline Rodal

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.....
I calculated the natural frequency of the EM Drive based on the formula for a perfect cylinder ( https://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity ) (using the cylindrical Bessel functions that you use in your spreadsheet), based on the Mean diameter (the average of the small and big diameters of the Baby EM Drive),  I obtained the following frequency for TE013 for perfectly flat ends:

24.41 GHz

which compares to the value I obtained using my exact solution:

24.34 GHz
......

With respect that is not now effective guide wavelength is calculated. Roger Shawyer told me how to do it and I shared this here several times. It is in my SS.

The effective guide wavelength is not based on the average of the 2 end plate diameter. It is the numerically integrated value of 10,000 diameters (well I use 10,000, could be more, could be less) including and in between the plates.

For the Baby EMD the guide wavelength for the mean/average diameter is = 0.016501. The numerically integrated effective guide wavelength is = 0.018224, which is why your resonance is too high as your effective guide wavelength is too small.

Have attached the latest version of the SS, which has a new feature.

Let's agree to disagree on this point otherwise this is going to run for ever.  You calculate the effective guide wavelength and the cut-off based on Bessel cylinder functions that do not satisfy the boundary conditions of the problem.  It is an ad-hoc solution that agrees with Shawyer's formulation (not an exact solution to Maxwell's equations for a truncated cone with flat ends)  .  You think it is better to proceed that way than using Finite Element analysis or using the exact solution for a truncated cone with spherical ends.

In this case (Baby EM Drive natural frequency 24 GHz TE013) it makes very little difference.

My point was that we cannot justify to include so many digits of numerical precision with geometrical dimensions (runout, concentricity) of unknown precision, and without performing a spectrum solution, as the participation of other modes in the response is not taken into account (the response of any system will not be the response of a single mode, but will include other mode shapes as well).
« Last Edit: 06/15/2015 02:47 PM by Rodal »

Offline TheTraveller

.....
I calculated the natural frequency of the EM Drive based on the formula for a perfect cylinder ( https://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity ) (using the cylindrical Bessel functions that you use in your spreadsheet), based on the Mean diameter (the average of the small and big diameters of the Baby EM Drive),  I obtained the following frequency for TE013 for perfectly flat ends:

24.41 GHz

which compares to the value I obtained using my exact solution:

24.34 GHz
......

With respect that is not now effective guide wavelength is calculated. Roger Shawyer told me how to do it and I shared this here several times. It is in my SS.

The effective guide wavelength is not based on the average of the 2 end plate diameter. It is the numerically integrated value of 10,000 diameters (well I use 10,000, could be more, could be less) including and in between the plates.

For the Baby EMD the guide wavelength for the mean/average diameter is = 0.016501. The numerically integrated effective guide wavelength is = 0.018224, which is why your resonance is too high as your effective guide wavelength is too small.

Have attached the latest version of the SS, which has a new feature.

Let's agree to disagree on this point otherwise this is going to run for ever.  You calculate the effective guide wavelength and the cut-off based on Bessel cylinder functions that do not satisfy the boundary conditions of the problem.  It is an ad-hoc solution that you like because it agrees with Shawyer's formulation .

My point was that there is no justification to include so many digits of numerical precision based on an ad-hoc formula based on cylinder functions and geometrical dimensions (runout, concentricity) of unknown precision, and not performing a spectrum solution, as the participation of other modes in the response is not taken into account (the response of any system will not be the response of a single mode, but will include other mode shapes as well).

It is not what I like or not. It is now Roger Shawyer instructed me to calculate the effective guide wavelength.

It is your method which does not agree with how Roger Shawyer and SPR do the effective guide wavelength calculation.
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Offline inquisitive-j

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I have been following the emDrive for sometime now. I've had a google alert on it for over a year, and I kept up with thread 2 up until around page 140. That thread has now been ended at page 209, and this thread is at now at page 91. I have to admit that I am not anxious to read through the roughly 160 pages that have been posted in my absence but would still love to know what's going on with the emDrive in Eagleworks. I have a suggestion/request that I think could help streamline this discussion a bit. I think that there should be a separate thread that can be commented on ONLY by the people at Eagleworks for the purpose of information dissemination. This way a person wouldn't have to sift through hundreds of pages to find the results of the latest emDrive experiments or the plans for the next experiment. If a thread in this forum couldn't be created with that restriction, perhaps a post on another site that was linked on this thread would do. This would help people like me, who want to catch up after an absence and would give everyone in this thread an easy go-to reference for their thoughts and discussions.

This would be a nice follow up to the great "Evaluating NASA’s Futuristic EM Drive" article which gives a nice broad introduction to the emdrive (http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/). My suggested thread would give people a more detailed, up to date view of what has happened with the emDrive and what eagleworks is planning next. This wouldn't need to be a lot of work either. For everything up to the present, simply copying and pasting the Eagleworks teams posts scattered through the 3 main threads into one place would do.

Online RotoSequence

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It is not what I like or not. It is now Roger Shawyer instructed me to calculate the effective guide wavelength.

It is your method which does not agree with how Roger Shawyer and SPR do the effective guide wavelength calculation.

Is there a numerical reason to believe that the SPR method delivers superior results to Rodal's?
« Last Edit: 06/15/2015 02:53 PM by RotoSequence »

Offline TheTraveller

It is not what I like or not. It is now Roger Shawyer instructed me to calculate the effective guide wavelength.

It is your method which does not agree with how Roger Shawyer and SPR do the effective guide wavelength calculation.

Is there a numerical reason to believe that the SPR method delivers superior results to Rodal's?

SPR design EM Drives and use this method (embodied in their in house software) to calculate resonance.
« Last Edit: 06/15/2015 03:00 PM by TheTraveller »
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Offline kdhilliard

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I think that there should be a separate thread that can be commented on ONLY by the people at Eagleworks for the purpose of information dissemination.

Has anyone from Eagleworks other than Paul March (NSF user Star-Drive) posted here?

All his posts can be seen here.  His last post was on 2015-04-30, the day after NSF's Evaluating NASA’s Futuristic EM Drive feature article was published.

~Kirk

Edit: Typo
« Last Edit: 06/15/2015 03:03 PM by kdhilliard »

Offline TheTraveller

I think that there should be a separate thread that can be commented on ONLY by the people at Eagleworks for the purpose of information dissemination.

Has anyone from Eagleworks other than Paul March (NSF user Star-Drive) posted here?

All his posts an be seen here.  His last post was on 2015-04-30, the day after NSF's Evaluating NASA’s Futuristic EM Drive feature article was published.

~Kirk

Paul March was told to stop posting to NSF or he would lose his job.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline Star One

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I think that there should be a separate thread that can be commented on ONLY by the people at Eagleworks for the purpose of information dissemination.

Has anyone from Eagleworks other than Paul March (NSF user Star-Drive) posted here?

All his posts can be seen here.  His last post was on 2015-04-30, the day after NSF's Evaluating NASA’s Futuristic EM Drive feature article was published.

~Kirk

Edit: Typo

All that can be said is that for the moment there is no posts from that direction, and not likely to be for the time being so the OP's suggestion is something of a non-starter.

@TheTraveller first I've heard of that.:eek:
« Last Edit: 06/15/2015 03:07 PM by Star One »

Offline TheTraveller

I think that there should be a separate thread that can be commented on ONLY by the people at Eagleworks for the purpose of information dissemination.

Has anyone from Eagleworks other than Paul March (NSF user Star-Drive) posted here?

All his posts can be seen here.  His last post was on 2015-04-30, the day after NSF's Evaluating NASA’s Futuristic EM Drive feature article was published.

~Kirk

Edit: Typo

All that can be said is that for the moment there is no posts from that direction, and not likely to be for the time being so the OP's suggestion is something of a non-starter.

@TheTraveller first I've heard of that.:eek:

Several others have confirmed as did Paul in a email to me.
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Offline inquisitive-j

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Has anyone from Eagleworks other than Paul March (NSF user Star-Drive) posted here?

All his posts can be seen here.  His last post was on 2015-04-30, the day after NSF's Evaluating NASA’s Futuristic EM Drive feature article was published.

~Kirk

Edit: Typo

I'm not sure. Paul March was the person I had in mind the most when I was posting that. I didn't think to look at his profile for a complete list of posts. I also didn't realize that he posted so little outside of emDrive discussion. I was hoping that he had posted in the 2-3 months that I'd been away from the threads, but I suppose not.

Edit- This is the first I'm hearing that Paul March was instructed not to post anymore, and if true, it is very disappointing. I was looking forward to updates on experiments run future plans.
« Last Edit: 06/15/2015 03:14 PM by inquisitive-j »

Offline TheTraveller

Has anyone from Eagleworks other than Paul March (NSF user Star-Drive) posted here?

All his posts can be seen here.  His last post was on 2015-04-30, the day after NSF's Evaluating NASA’s Futuristic EM Drive feature article was published.

~Kirk

Edit: Typo

I'm not sure. Paul March was the person I had in mind the most when I was posting that. I didn't think to look at his profile for a complete list of posts. I also didn't realize that he posted so little outside of emDrive discussion. I was hoping that he had posted in the 2-3 months that I'd been away from the threads, but I suppose not.

Can check his stats here:
http://forum.nasaspaceflight.com/index.php?action=profile;area=summary;u=2074

Was last loggged on 15 June, so he does read forum posts.
« Last Edit: 06/15/2015 03:13 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
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