Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1802087 times)

Offline SeeShells

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So much has been talked about on evanescent waves I felt I needed a refresher and found this of youtube and I think it help me understand and refresh my understanding of evanescent waves.


Interesting that this looks like the angles of a Frustum.


Reading and watching videos this morning.

Shell

Offline rfmwguy

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It would be interesting if one of the experimenters would hang a magnet in front and behind their frustum. Since the frustum is copper, there should not be any movement of the magnet unless DC magnetic fields are passing through it. It should be fairly easy to see if the magnets start swinging when the magnetron is turned ON.

Of course a Gauss meter sensitive to 2.5 GHz would be better for collecting data. A magnet will at least tell us if "something" is coupling through to the outside world.

Todd
And I thought I was going to surprise everyone with my magnet idea. You're just too sharp! It is a great idea for a simple test isn't it?

I think so. Yesterday when I offered my conjecture that the currents are DC, I hadn't realized that a microwave magnetron is said to operate on a 50% duty cycle. The easiest way to do that is a 1/2 wave rectifier. That got me thinking that maybe the waves are driven with a DC offset from the transformer, and exponentially decay right out of the magnetron.

Hmmm, methinks the voltage doubler cap and diode circuit generating 4kv bias from a 2kv transformer on everyday microwave power supplies does indeed cause the 50% duty cycle. Its pulsed, as in radar...rapidly expanding and collapsing fields...the buzzing noise julian commented on...tilt  :o

I found some schematics for microwave ovens. Yup... that's exactly how it works. The magnetron sees only a 0.7V diode-drop on it's input during the positive half-cycle at 60Hz, and -4kV with an exponential decaying  voltage on the negative half-cycle, with a time constant set by the capacitor and the power consumption of the Magnetron. Such a source is probably 99.999% guaranteed to produce an accumulated DC offset in a low-impedance short-circuit such as a frustum.

Therefore, rather conclusively then, exponentially decaying evanescent waves are not only caused by the geometry, they are being input by the source!

That could be a key difference then between those who used Magnetrons, and Brady who used an RF amplifier. I recall Star Drive saying that "dithering the input" seemed to have the best results.
Todd

I agree @warptech, this could be a key in understanding the effect. Bad news for CW experimenters like me, BUT there is an old friend, the pulse modulator:

http://www.gtmicrowave.com/SPST_PIN_Diode_Pulse_Modulator_Model_S1P_69_3JH.php

Methinks this is why this forum exists, to question assumptions and to take previous low-budget testing to the next level of thought, then experimentation.

Why have we not seen (variable) pulse modulated testing of the RF source? While many are focused on mechanicals and continuous wave models (like me), it might have been worthy to have pulse width and rep rate variables on the RF source...maybe.
« Last Edit: 06/18/2015 12:08 PM by rfmwguy »

Online Rodal

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An AC magnetic field at GHz with zero bias will show squat on a bar magnet.

Correcto! But a DC magnetic field is not shielded by copper and evanescent waves do not have time averages equal to zero. Therefore, the volt-seconds product applied to the conductors by the E field is not 100% canceled on each cycle. A DC bias can (and probably does) exist, and that is what can escape outside the copper walls because the skin effect does not apply.

I'm working on the paper now to show a DC field will exert thrust on a conical section, without microwaves. As it moves forward, B-field escapes, lowering the potential energy and impedance, allowing it to draw more power from the battery. Watt goes in is Watt comes out! :) It is a near-field photon rocket that works due to inefficient coupling and leakage inductance. It may not work, but I'm going to write it up anyway.

Since gravity in the PV Model is basically a gradient in the inductance and capacitance, it is simply another expression of how it mimics gravity. It has a DC bias in one direction and this is unique to a cone!
Todd

It is noteworthy that Greg Egan (in his analysis of the EM Drive http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html ) discards the static (DC) solution of Maxwell's equations:

Quote from: Greg Egan
(Note that although [8] also gives the vector field L = grad f as a further solution, the curl of a gradient is zero, and if either curl E = 0 or curl B = 0 that would imply, via Maxwell’s equations, a completely static solution.)

So, Greg Egan does not take into consideration the following solutions of Maxwell's equations:


1) the static (DC) solution  L = grad f  (he admits this in his paper)

2) evanescent waves                          (he does not state explicitly that he does not consider this solution)

Greg Egan only considers the standing wave solution.
« Last Edit: 06/18/2015 01:06 PM by Rodal »

Offline VAXHeadroom

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For any interested: I found this book on the shelves at work yesterday.  It's an unabridged 1955 reprint of a 1912 work by H.Bateman, exhaustively referenced, but to stuff that's probably unobtanium.  It still refers to the aether and references GR as a 'recent theory' :)
Note the stamp on the front "Litton Library".  This was in the library of Litton's AMECOM division which was purchased by Northrop Grumman in 2001 (I came along with the purchase!).  The last time it was checked out of the library was 1970 :)
If anyone cares I can scan any portions of this which might be of interest.
« Last Edit: 06/18/2015 01:03 PM by VAXHeadroom »
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Online Rodal

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More null data from the Baby EM Drive.  They increased the damping by further immersion in water (why don't they use oil instead ?).   The researchers admit that it is difficult to extract a meaningful signal from these data, as the noise from the data gets damped, it is evident that the signal is null:


https://hackaday.io/project/5596-em-drive/log/19695-torsion-test-4-inversed
« Last Edit: 06/18/2015 01:16 PM by Rodal »

Online kdhilliard

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I am grateful to Costella for pointing out that not only does Shawyer not understand Newton's laws (or if he does, is unable to communicate them clearly), but also seems incapable of correctly drawing force vectors at the sidewall. This in Shawyer's mind gave a finite net thrust, based purely on the summation of his incorrect reflected force vectors over the complete surface of the frustum. A childish error unworthy of even a junior reliability engineer, one might say?

Are you seriously considering Roger Shawyer predicted the forces produced by his EmDrive using… arrows on a drawing, instead of equations?

Do we even know the history of Shawyer's theory vs. experimentation?

Without knowing better, I'm left wondering if some of his more egregious misapplications of Newton's laws were attempts to align his theory with experimental results.  The two most obvious are:

1. In his Theory Paper he claims that there is a greater radiation pressure (times Q) on the interior face of the large end of the frustum than on the small end.  He does not mention the direction of acceleration, leaving everyone to understand that the EmDrive should accelerate large end first.  But in his IAC-08 paper he adds, "Note that to maintain the principle of the conservation of momentum, the acceleration of the waveguide due to thrust is opposite to the actual thrust direction."  This is a bizarre statement, as his thrust is a net force on the frustum itself, not on any exhaust propellant.  Did he initially expect the EmDrive to accelerate large end first, and only mis-invoked Newton's third law of motion (where's the second body?) after initial experimental evidence suggested that it would accelerate small end first.  (V 9.4 of his Theory Paper is dated 2006, but it is possible that he addressed direction of acceleration earlier but never got around to rolling it into his Theory Paper.)

2. In his Measurement Paper he claims that when an EmDrive is "at rest, no force can be measured."(Pg. 2)  As has been pointed out in this forum, some displacement is necessary to measure any force, via compression of a load cell, for instance, but with a constant application of force the system is at rest following that initial displacement.  Shawyer explicitly states that such a measurement will not work for the EmDrive.  "Because the thruster is at rest, no force will be measured on the load cell."(Pg. 3)  He goes on to say:
Quote from: Measurement Paper, Pg. 3
A number of methods have been used in the UK, the US and China to measure the forces produced by an EmDrive thruster.  In each successful case, the EmDrive force data has been superimposed on an increasing or decreasing background force, generated by the test equipment itself.

Indeed, in the UK when the background force changes were eliminated, in an effort to improve force measurement resolution, no EmDrive force was measured.  This was clearly a result of attempting to measure the forces on a fully static thruster, where T and R cancel each other.
This sounds as if he initially expected to receive better results from a less noisy test rig, but when he ran his refined experiment he measured no force, and instead of concluding that his earlier measurements were artifacts of the more noisy rig, he expanded on his "T vs. R opposing forces generated by the same body" ideas to explain away the results.

It would be interesting to hear Shaywer describe how his theory evolved as a result of his experimentation.

~Kirk

Offline PaulF

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Why have we not seen (variable) pulse modulated testing of the RF source? While many are focused on mechanicals and continuous wave models (like me), it might have been worthy to have pulse width and rep rate variables on the RF source...maybe.
I asked this same question in thread 2 a while back. There was no reply, so I too am curious about this.


Online Rodal

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Why have we not seen (variable) pulse modulated testing of the RF source? While many are focused on mechanicals and continuous wave models (like me), it might have been worthy to have pulse width and rep rate variables on the RF source...maybe.
I asked this same question in thread 2 a while back. There was no reply, so I too am curious about this.
Paul March (NASA, "Star-Drive") has extensive discussions on Frequency Modulation, Amplitude Modulation and Phase Modulation on Thread 2 of the EM Drive, including Dr. White's computer analysis of the effect of such modulations on the thrust force, and their plans to investigate this this summer.  So he may be running such modulation tests right now at NASA, for all we know.
« Last Edit: 06/18/2015 01:56 PM by Rodal »

Offline rfmwguy

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More null data from the Baby EM Drive.  They increased the damping by further immersion in water (why don't they use oil instead ?).   The researchers admit that it is difficult to extract a meaningful signal from these data, as the noise from the data gets damped, it is evident that the signal is null:


https://hackaday.io/project/5596-em-drive/log/19695-torsion-test-4-inversed

Doc, what is your educated guess as to null results? Input power? Scaling errors? Non-scaleable?

Online Rodal

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More null data from the Baby EM Drive.  They increased the damping by further immersion in water (why don't they use oil instead ?).   The researchers admit that it is difficult to extract a meaningful signal from these data, as the noise from the data gets damped, it is evident that the signal is null:


https://hackaday.io/project/5596-em-drive/log/19695-torsion-test-4-inversed

Doc, what is your educated guess as to null results? Input power? Scaling errors? Non-scaleable?
There was an excellent post a few pages ago where somebody calculated the predicted thrust force for Baby EM Drive and it came out to be less than 1 microNewton, (from what I recall).

The poster has asked others to run similar calculations using other formulas (McCulloch?, Notsosureofit?, Shawyer?) but I have not seen anybody else attempting such prediction.

So, so far it looks like the predicted force, even when considering a Q of ~10,000 to ~20,000 is extremely small.  Furthermore the researchers have not (to my knowledge) even measured resonance Q, so they don't know whether they are operating at resonance or not.

The response of the Baby EM Drive always looked to be drowned by noise to me (and I do a lot of my work in the area of extracting signals from noise).  The best signal they got IMHO was from the magnetic levitation experiment and they have abandoned that test.  This latest test (#4) definitely looks like a null test IMHO.
« Last Edit: 06/18/2015 01:55 PM by Rodal »

Offline TheTraveller

More null data from the Baby EM Drive.  They increased the damping by further immersion in water (why don't they use oil instead ?).   The researchers admit that it is difficult to extract a meaningful signal from these data, as the noise from the data gets damped, it is evident that the signal is null:


https://hackaday.io/project/5596-em-drive/log/19695-torsion-test-4-inversed

Assuming a Q of 10,000 and Rf power at 0.1W, my SS shows 4.9uN or 0.0005gf. SnowFlake is 6x more at 0.003g.
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Online Rodal

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I am grateful to Costella for pointing out that not only does Shawyer not understand Newton's laws (or if he does, is unable to communicate them clearly), but also seems incapable of correctly drawing force vectors at the sidewall. This in Shawyer's mind gave a finite net thrust, based purely on the summation of his incorrect reflected force vectors over the complete surface of the frustum. A childish error unworthy of even a junior reliability engineer, one might say?

Are you seriously considering Roger Shawyer predicted the forces produced by his EmDrive using… arrows on a drawing, instead of equations?

Do we even know the history of Shawyer's theory vs. experimentation?

Without knowing better, I'm left wondering if some of his more egregious misapplications of Newton's laws were attempts to align his theory with experimental results.  The two most obvious are:

1. In his Theory Paper he claims that there is a greater radiation pressure (times Q) on the interior face of the large end of the frustum than on the small end.  He does not mention the direction of acceleration, leaving everyone to understand that the EmDrive should accelerate large end first.  But in his IAC-08 paper he adds, "Note that to maintain the principle of the conservation of momentum, the acceleration of the waveguide due to thrust is opposite to the actual thrust direction."  This is a bizarre statement, as his thrust is a net force on the frustum itself, not on any exhaust propellant.  Did he initially expect the EmDrive to accelerate large end first, and only mis-invoked Newton's third law of motion (where's the second body?) after initial experimental evidence suggested that it would accelerate small end first.  (V 9.4 of his Theory Paper is dated 2006, but it is possible that he addressed direction of acceleration earlier but never got around to rolling it into his Theory Paper.)

2. In his Measurement Paper he claims that when an EmDrive is "at rest, no force can be measured."(Pg. 2)  As has been pointed out in this forum, some displacement is necessary to measure any force, via compression of a load cell, for instance, but with a constant application of force the system is at rest following that initial displacement.  Shawyer explicitly states that such a measurement will not work for the EmDrive.  "Because the thruster is at rest, no force will be measured on the load cell."(Pg. 3)  He goes on to say:
Quote from: Measurement Paper, Pg. 3
A number of methods have been used in the UK, the US and China to measure the forces produced by an EmDrive thruster.  In each successful case, the EmDrive force data has been superimposed on an increasing or decreasing background force, generated by the test equipment itself.

Indeed, in the UK when the background force changes were eliminated, in an effort to improve force measurement resolution, no EmDrive force was measured.  This was clearly a result of attempting to measure the forces on a fully static thruster, where T and R cancel each other.
This sounds as if he initially expected to receive better results from a less noisy test rig, but when he ran his refined experiment he measured no force, and instead of concluding that his earlier measurements were artifacts of the more noisy rig, he expanded on his "T vs. R opposing forces generated by the same body" ideas to explain away the results.

It would be interesting to hear Shaywer describe how his theory evolved as a result of his experimentation.

~Kirk

This is an excellent description of Shawyer's reports, much better than what I could have written. 

Add to this that Prof. Yang, as shown in the following paper (hat tip to @Flux Capacitor):

Yang, Juan; Wang, Yu-Quan; Ma, Yan-Jie; Li, Peng-Fei; Yang, Le; Wang, Yang; He, Guo-Qiang (May 2013). "Prediction and experimental measurement of the electromagnetic thrust generated by a microwave thruster system" (PDF). Chinese Physics B (IOP Publishing) 22 (5): 050301. doi:10.1088/1674-1056/22/5/050301

explicitly, clearly writes that the thrust force is  directed towards the small end, instead of Shawyer's statement that the thrust force is directed towards the big end (Shawyer posits an internal thrust force in the opposite direction than the acceleration of the EM Drive).

So, how can some people state that Prof. Yang has been following Shawyer's prescriptions? (when Prof.Yang herself abandons Shaywer's statement that thrust force of the EM Drive is towards the big end, while it accelerates towards the small end?)

To my knowledge, Shawyer is the only person that maintains that the thrust force on the EM Drive is in the opposite direction than its acceleration.  No wonder his latest paper in his blog attempts to address this once again, as apparently many of his readers have asked him to explain what he means.
« Last Edit: 06/18/2015 02:10 PM by Rodal »

Offline TheTraveller

Please stop diverting away from my question.

What is YOUR TE013 resonance frequency for the 2 sets of dimensions I provided?

(Correct me if I'm wrong here)

TheTraveller, you're being a bit thick. He is saying that unless Shawyer has experimentally verified what mode he was in by taking measurements or making observations to PROVE that specific mode was in effect, that he is simply (and inaccurately) making a postulation as to what mode he BELIEVES that it is operating in, when in reality he does NOT know. Rodal is arguing that the wrong mode is being used to explain how it works, not that your work does not accurately approximate the resonant frequency and design factor etc of his devices... The formula you use coincides very well with Shawyer's own formula to calculate it, which is impressive, and we thank you for that... Yes, you are able to predict the appropriate resonant frequency that Shawyer also uses for his device, but it still doesn't prove his declaration of what mode it's operating in is an accurate statement. That mode is important to Shawyer because that's the one he uses to explain his data with inaccurate theory about open cylindrical waveguides and other things that fly in the face of common sense understanding and mathematical application regarding the system under experimentation.

I sent Shawyer the 3 internal Flight Thruster dimensions I had derived and asked for the resonance frequency:

Frustum big diameter    m   0.2314000
Frustum small diameter   m   0.1257000
Frustum centre length   m   0.1386000
Spherical end plates

He sent back 3.9003GHz.

When I plugged that data into my SS I see the mode is TE013, which is what he told me SPR used.

When I ask Dr Rodal the same question all I get is hand waving, which tells me his solution does not produce 3.9003GHz at any mode.

We know the Flight Thruster external big end overall width is 256mm and overall height 154mm, Q 50,000 and excitation frequency 3.85GHz. We also have his experimental data of power versus thrust.

I really do not care what mode it is operating in as long as I get thrust. However the spreadsheet I use, which is based on how SPR does the calc, shows me the mode as TE013 based on equivalent guide wavelength at TE01 mode and 3 x 1/2 guide wavelengths fitting between the end plates.

I would also point out that Dr, Rodals nice images are all using spherical end plates and very few builders are going that pathway. Would love to see Dr. Rodal's images and resonance data for frustums with flat end plates.
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Online Rodal

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Please stop diverting away from my question.

What is YOUR TE013 resonance frequency for the 2 sets of dimensions I provided?

(Correct me if I'm wrong here)

TheTraveller, you're being a bit thick. He is saying that unless Shawyer has experimentally verified what mode he was in by taking measurements or making observations to PROVE that specific mode was in effect, that he is simply (and inaccurately) making a postulation as to what mode he BELIEVES that it is operating in, when in reality he does NOT know. Rodal is arguing that the wrong mode is being used to explain how it works, not that your work does not accurately approximate the resonant frequency and design factor etc of his devices... The formula you use coincides very well with Shawyer's own formula to calculate it, which is impressive, and we thank you for that... Yes, you are able to predict the appropriate resonant frequency that Shawyer also uses for his device, but it still doesn't prove his declaration of what mode it's operating in is an accurate statement. That mode is important to Shawyer because that's the one he uses to explain his data with inaccurate theory about open cylindrical waveguides and other things that fly in the face of common sense understanding and mathematical application regarding the system under experimentation.

I sent Shawyer the 3 internal Flight Thruster dimensions I had derived and asked for the resonance frequency:

Frustum big diameter    m   0.2314000
Frustum small diameter   m   0.1257000
Frustum centre length   m   0.1386000
Spherical end plates

He sent back 3.9003GHz.

When I plugged that data into my SS I see the mode is TE013, which is what he told me SPR used.

When I ask Dr Rodal the same question all I get is hand waving, which tells me his solution does not produce 3.9003GHz at any mode.

We know the Flight Thruster external big end overall width is 256mm and overall height 154mm, Q 50,000 and excitation frequency 3.85GHz. We also have his experimental data of power versus thrust.

I really do not care what mode it is operating in as long as I get thrust. However the spreadsheet I use, which is based on how SPR does the calc, shows me the mode as TE013 based on equivalent guide wavelength at TE01 mode and 3 x 1/2 guide wavelengths fitting between the end plates.

I would also point out that Dr, Rodals nice images are all using spherical end plates and very few builders are going that pathway. Would love to see Dr. Rodal's images and resonance data for frustums with flat end plates.

It is interesting to get confirmation, that after all:

I really do not care what mode it is operating in as long as I get thrust 

The only researcher that I know that has explicitly shown an equation relating thrust to mode  shapes is @Notsosureofit.  I have not seen anything by Shawyer explicitly relating thrust to mode shape.

It is trivial to calculate the difference in arc length between the spherical ends and flat ends for these truncated cones.  The difference in arc length between the spherical ends and flat ends for NASA's truncated cone is only 1% (one per cent), while for Shawyer's Flight Thruster is 2%.

To accurately model the effect of flat ends one has to use numerical methods like MEEP's (Finite Difference Method) or COMSOL FEA (Finite Element Analysis).  The ad-hoc spreadsheet method used by TheTraveller/ Shawyer does not satisfy the boundary conditions of the problem and definitely cannot accurately account for these effects.  The exact solution I am using, exactly satisfies all boundary conditions for a truncated cone with spherical ends.

This can be seen in the MEEP and in the COMSOL analysis: as the field conforms to a spherical wave field inside the truncated cone and accommodates the flat boundary condition of the flat ends only at the very end (like a boundary layer effect).  This effect is very small for the NASA truncated cone, as shown by the excellent comparison between COMSOL's FEA analysis by NASA and by the exact solution for the only mode shape that has been experimentally confirmed up to now: TM212.
« Last Edit: 06/18/2015 02:51 PM by Rodal »

Offline space_britannia

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Apologies if this has already been raised, but this paper on propulsion of a graphene sponge by electron ejection (excited by a laser) has been doing the rounds: http://nextbigfuture.com/2015/05/graphene-sponge-can-absorb-light-and.html

Have any attempts been made to measure an electron plume from the EmDrive? Are the devices building up a charge?

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Apologies if this has already been raised, but this paper on propulsion of a graphene sponge by electron ejection (excited by a laser) has been doing the rounds: http://nextbigfuture.com/2015/05/graphene-sponge-can-absorb-light-and.html

Have any attempts been made to measure an electron plume from the EmDrive? Are the devices building up a charge?

Concerning charge, see this : http://forum.nasaspaceflight.com/index.php?topic=37642.msg1390599#msg1390599

Offline TheTraveller

It is interesting to get confirmation, that after all:

I have said that many times. Guess you don't read what I post.

Now to ask again, can you obtain resonance at 3.9003GHz, using any mode, for the quoted dimensions? If not what is the closest frequency and mode? Please no hand waving or excuses. just post what your method produces?
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It is interesting to get confirmation, that after all:

I have said that many times. Guess you don't read what I post.

Now to ask again, can you obtain resonance at 3.9003GHz, using any mode, for the quoted dimensions? If not what is the closest frequency and mode? Please no hand waving or excuses. just post what your method produces?

I had posted my results for the Flight Thruster (I think it was in Thread 2 when you first started calculating frequencies for it) for an excitation frequency of 3.85 GHz (which is the frequency reported by Shawyer in his publications).  That's the frequency we have in the EM Drive wiki for the flight thruster:  http://emdrive.wiki/Experimental_Results

I still don't understand why you are now insisting on looking at an excitation frequency of 3.9003 GHz, when Shawyer has written in his publications that the excitation frequency is 3.85 GHz.  What is the need to re-run calculations for 3.9003 GHz ? Why is that accuracy in frequency needed -down to 5 digits precision-?
In what publication of Shawyer does he ever say that the excitation frequency of the Flight Thruster was 3.9003GHz? What difference does it make? I thought you were not going to conduct experiments at that high frequency and that you were going to do it at 2.45 GHz (because, as I recall, the expense for the hardware needed to run at the Flight Thruster frequencies)...

The exercise looks all the more pointless to me when Shawyer has never published that the frequency was 3.9003 GHz, Shawyer never verified the mode shape and you yourself state that you don't care what the mode shape is, and moreover you stated that you were not planning to do your experiment at that high a frequency.
« Last Edit: 06/18/2015 02:59 PM by Rodal »

Offline TheTraveller

It is interesting to get confirmation, that after all:

I have said that many times. Guess you don't read what I post.

Now to ask again, can you obtain resonance at 3.9003GHz, using any mode, for the quoted dimensions? If not what is the closest frequency and mode? Please no hand waving or excuses. just post what your method produces?

I had posted my results for the Flight Thruster (I think it was in Thread 2 when you first started calculating frequencies for it) for an excitation frequency of 3.85 GHz (which is the frequency reported by Shawyer in his publications).

I still don't understand why you are now insisting on looking at an excitation frequency of 3.9003 GHz, when Shawyer has written in his publications that the excitation frequency is 3.85 GHz.  What is the need to re-run calculations for 3.9003 GHz ? Why is that accuracy in frequency needed -down to 5 digits precision-?
In what publication of Shawyer does he ever say that the excitation frequency of the Flight Thruster was 3.9003GHz? What difference does it make? I thought you were not going to conduct experiments at that high frequency and that you were going to do it at 2.45 GHz...

We have now 6 locked down data points from SPR: Small dia, Big dia, Length, Df, resonant frequency & mode. There is no other set of those data provided by SPR. They are unique.

If your method is accurate and you used the dimensions I sent to Shawyer (which is not what you used before), you should get the same 3.9003GHz he got using my supplied dimensions. What do you get?
« Last Edit: 06/18/2015 03:01 PM by TheTraveller »
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    ... snip ...   
    ... snip...

@aero

Is that the electromagnetic field that MEEP 3D predicts for the Flight Thruster?
yes
Quote


The field variation in the azimuthal (circumferential) direction "m" looks definitely like having a value of m=1 instead of the value of m=0 for TE013 (m=0,n=1,p=3).

See this chart:



 It doesn't look like the mode shape TE013 that TheTraveller says that Shawyer believes the Flight Thruster should have experienced, based on Shawyer's calculations.  Unfortunately I understand that Shawyer did not perform any experimental verification of what the actual mode shape actually was, so it doesn't look like we can ever be sure what mode shape the Flight Thruster actually experienced. 

The only researcher that has experimentally verified a mode shape, to my knowledge, has been Paul March at NASA, who experimentally verified mode shape TM212 for NASA's truncated cone cavity.




... snip...

Regarding lack of response on dimensions for the Flight Thruster, yes these are the dimensions that I recall were given by TheTraveller at some point in time (I lost track whether these are the latest or why would they have changed):

Cavity Length (m)   big diameter (m)   small diameter (m)

0.1386                     0.2314                    0.1257

Congratulations on making such great progress with MEEP where you can now run 3D models.

Additionally, there is the issue of what the excitation RF frequency was.  In Shaywer's publications, Shawyer gives 3.85 GHz for the Flight Thruster, but in that quotation TheTraveller is saying that External Rf was instead 3.90 GHz?

What excitation frequency did you use for your MEEP 3 D analysis ? (3.85 GHz or 3.90 GHz ?)

How much computer time do these MEEP 3D runs take ?

Are you running them on the same computer that you were using to run the MEEP 2D models ?
(set! fsi 3.87295489E+009)                     ; Drive frequency

Not a lot of CPU time at all. Two to 5 minutes, depending on noise BW.
  I've given up on trying to model thin copper, the walls of this model are 1/4 inch thick so the model will run at much lower resolution. I also changed the meep scale factor, scaling the cavity to about 1x1, and have totally eliminated any volume external to the cavity. That works when looking at cavity internal field patterns but will need to add the volume back in if I look at anything outside the cavity. That will slow it back down.

Yes, its the same machine.

There's also the question of where the antenna should be located and should it be excited by Ez (currently) or by Hy components?
« Last Edit: 06/18/2015 03:19 PM by aero »
Retired, working interesting problems

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