Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1873433 times)

Offline Notsosureofit

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Mmmm....shouldn't Q be a function of the delay loss ?

Offline Rodal

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Folks - this is a contribution to theory, not replication. It demonstrates a solution to Maxwell's equations in a theoretical infinite two-dimensional cavity which describes a net total Lorentz force on the conductors. There are some reasons why this might be an academic curiosity, but it may be of interest....
The theory does not seem to address conservation of linear momentum (if I missed it, please let me know).

The center of mass of a closed system can not accelerate as a result of internal interactions between the parts of the system.

Interactions between internal parts of the EM Drive system are described that apparently will produce an internal asymmetric force.  However, conservation of momentum precludes any such unbalanced force on the center of mass and thus preclude acceleration of the center of mass solely on this basis.

In Mechanics of Solid and Fluid Continuum, many solutions for phsyical problems can be posited, however, if any such solution does not satisfy the equations of equilibrium, then any such solution cannot be a physical solution to the problem.  The equations of equilibrium (in this case, conservation of momentum) needs to be addressed.
« Last Edit: 07/23/2015 11:49 AM by Rodal »

Offline RERT

ref my post above, and why I bothered.

The lack of consideration of electron inertia has always bugged me. We are looking for a very small effect, and the fact there are small effects sitting around being ignored doesn't make much sense. It isn't obvious to me how to model this realistically without going to a numerical model. I decided that would take me forever, hence the above.

Second, the explanation in terms of radiation pressure in a shaped cavity has always struck me as mince.

Thirdly, there is at least scope to no lose heart. The paper I referred to aeons ago by Tuval and Yahalom (2013) points out that it is straightforward physics that a system of self-interacting moving charges and currents need not have a zero net force. Conservation of momentum only means that momentum has to be carried away in the EM field, which is what happens in my example.

Fourth, note that the 10^-13 delay time I used comes from a simple model giving a time characteristic of

t = 3 (m/e)*(sigma/rho)

where m is electron mass, e charge, sigma conductivity, and rho conduction electron charge density. I then plugged in the values for copper, and got around 7*10^-14.

The model is probably tendentious, but it is highly likely that different materials will have different characteristic times. This invites experimentation with using materials to make the frustrum asymmetric, as well as geometry. In other words, by using different materials at each end - though beware that if there is any reality in what I say there is scope for putting them the wrong way round!

R.

Offline RERT

Dr. Rodal -

The plane waves off to left and right carry off momentum. The delay causes the conducting barriers to carry
an induced current, and they radiate in both directions.

Notsureofit -

Yes, I'm sure there should be a relationship between Q and wall losses, but I will have to think some more about that.

R.

Offline Rodal

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I'm curious as to why the capable engineers at EagleWorks are finding Q-values around 5,000 to 6,000, and yet around here there's a lot of talk about Q-values ten times higher?

Because EW is using real world materials with analog sources, not discretized sources and idealized copper that doesn't seem to heat or suffer significant losses of any sort. Perhaps, just guessing here, perhaps if the node granularity was less than the skin depth of the copper, we could see more realistic skin effects. But its not so we can't.

Examination of the equations used to calculate Q reveal that the higher Q's being discussed cannot be due to NASA Eagleworks using real world materials, (instead of "unreal materials" being used in the Q calculations)

On the contrary:

1) Examination of the equation used to calculate Q



shows that the material properties have the least influence on the calculated Q.  The material properties are known, they can be accurately quantified and it is trivial to show that the difference between copper, bronze and brass cannot result in calculated Q's to differ by a factor 10, from 5,000 to 50,000, and much less to differ by the calculated values.  See what is the functional dependence of Q on  resistivity



(it is a very weak dependence: it depends on the square root of the material properties)

and then see this table:  http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/

To produce a change in Q of a factor of 10, the resistivity ρ would have to differ by a factor of 100.  Not possible.  To produce a change in Q of a factor 1,000, the resistivity ρ would have to differ by a factor of 1,000,000.  Completely impossible.

The permeability of free space μo is a constant.  The relativity permeability μr of copper is very slightly less than 1.  Copper's relative permeability is not going to differ by a large factor.

2) The expression being used to calculate Q is a very different expression than the expression used to measure Q



.  One needs to look at what is being calculated as Q (and what variables affect the calculated result) as opposed to what is measured as Q.

3) Homonyms are words that are both spelled and pronounced the same, but have different meanings.  If one assumes that they have the same meaning, one will end up in confusion.  If we want to understand the difference, we have to understand how Q is being calculated and how it is being measured. Then it becomes clear.

4) Neither what is measured as Q nor what is calculated as Q may correspond to what one thinks Q represents. Not just using calculated Q, but using measured Q may lead to misinterpretation of what is going on, if one doesn't carefully go through the equations.
« Last Edit: 07/23/2015 07:37 PM by Rodal »

Offline Rodal

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Dr. Rodal -

The plane waves off to left and right carry off momentum. The delay causes the conducting barriers to carry
an induced current, and they radiate in both directions.

...

Thanks for the reply.  I'm interested on whether you could elaborate further as to how the electromagnetic waves escape the "Faraday cage" of the copper cavity.  The electromagnetic fields are inside the cavity.  At the copper surface one usually assumes a boundary condition that the tangential Electric Field will always be zero on a metal like copper.  How do electromagnetic waves get out ?  How does momentum get carried to the outside of the cavity ?

If it is posited that momentum is carried off by black body radiation from the metal to the exterior environment (it would have to radiate more in the big base than the small base and the lateral surface axial component), a calculation shows that the black body radiation cannot account for the forces and accelerations being claimed by the EM Drive researchers.  The momentum carried by black body radiation is several orders of magnitude smaller than what is claimed.
« Last Edit: 07/23/2015 01:55 PM by Rodal »

Offline Tron

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Ignore this if it's already posted, but you may want to have a look at this paper:

http://arxiv.org/pdf/1302.2537v1.pdf

"Newton’s Third Law in the Framework of Special Relativity"

The conclusions are pretty juicy, I quote part of them:

"We have shown in this paper that in general Newton’s third law is not compatible with the principles of special relativity and the total force on a two current loop system is not zero"

Then discusses how to get constant (reactionless!) force using two wires of conducting material, one with constant direct current and the other carefully modulated, if I understand the paper well enough,.

Offline rfmwguy

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Regarding using wire mesh,

A wire mesh waveguide is described in https://www.jlab.org/ir/MITSeries/V9.PDF pg 287 with a loss of .4db/m, compared to (typical?) .02db/m. Only ~10%. However, wouldn't one have to multiply that by the expected number of reverberations the wave will traverse? My math on factorials or series is a bit rusty.

$120 for a roll of copper looks pricey compared to the $15 aluminum next to it. Perhaps it can be copper plated? Pretty simple to copper plate.

Another paper on how to hack a magnetron, to work as an amplifier, CW and very (relatively) narrow bandwidth, and use magnetic solenoid tuning:
http://n5dux.com/ham/files/pdf/The%20Magnetron-A%20Low%20Noise%20Long%20Life%20Amplifier.pdf
Nice links. wire mesh intrigued me for several reasons that Doc has summarized. Another one may be the angle of reflection, or better yet, scattering of radiation. Assuming outward vector forces are striking frustum side walls.

Offline SeeShells

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...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out.

Check it again, they are there now.
I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero.  The stress at the big base is a central point stress from the antenna.  Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically lower amplitude.

QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?

Most important: QUESTION2: did Meep give you a Q value for this case ?

Thanks
He emailed me saying the Q was something like 57,000+ but was worried about the antenna position, I said run it if you want but I was still doing research into the antenna and had questions out to ppl who had 40 years + in this field. It's not one I would want to make.

Shell
Friendly reminder that Qs over 10K are probably impractical to consider because of the extremely narrow bandwidth; subject to wide variation of resonant freq caused by thermal/mechanical stresses. You could wind up chasing resonance around, especially with a magnetron. I'm with doc on this, high q is not a prerequisite imho.

Design and testing thoughts during this first cup of coffee.....

I couldn't agree more on the Q. To me Q is like a slippery fish, you squeeze it tighter and pop away it goes. Plus running your frequency in a narrow bandwidth you just might be leaving out ghost modes and evanescent waves that are having an effect in generation of thrust. I want to catch this fish.

I've been keeping my eye (ebay and some of my old friends in the industry) on power supplies in the semiconductor industry that are used for magnetron sputtering for metal deposition, they are high power and have the controls to vary their output from duty cycle to frequency and bandwidth and power.

I have a AC rheostat that I was thinking about putting on the current magnetron heater I'm using to drop the voltage lowering the output power and narrowing the bandwidth of the magnetron. I have about 3 volts to work with so it will be touchy. Thoughts here?

You see where I'm going here? The magnetron can be a key in focusing what wave actions are causing the thrust. If I can control the input to the Cavity through the magnetron I can set up a low to medium power test getting stable thrust. Then by varying bandwidth, frequency, duty cycles and even modulate using FM or AM, sweeping the signal across the tune point even varying the Q actions of the cavity and monitoring the thrust. This is another reason I selected the beam to measure. When I "tune" in the maximum thrust I can then set the beam to a acceleration mode to monitor a real world acceleration thrust.

This active mode of the fulcrum beam could be used to test out the theory of motor/generator mode of RS. Small linear springs can be used top and bottom of the beam arm I'd I keep the same cupped dual knife edge (A slight V shape where the carbon fiber tube (CFT) sits in, it keeps it from rolling off).  Or and I like this better, suspend the CFT with SS wires @ a 45 degree angle on the center point and drop a arm with a small weight on with a pointer to a scale under the CFT and monitor it's movement, I could calibrate the divisions with weights on the end of the CFT.

Thanks for the Ghost mode and Cavity Mesh measurements to read last night.

Shell

Offline Rodal

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I think I've lost track of all the DIYers now. Let's see:
1. TheTraveller
2. SeeShells
3. rfmwguy
4. Mulletron (?)
5. klm(?)

Is this on the wiki?
Is the wiki link not supposed to be at the top of the page btw? - can't find it.

Concerning, this, what do people think about reporting NULL results of experimenters ? .

So far we have put in the wiki the information about the Aachen Baby EM Drive guys results as being Null, as hard as they try they are clearly Null, so far (and they have tried different measurements).

However we have not reported as Null the partial results of others (with a question mark on the list).

Should we post those partial null results as NULL in the Wiki experimental results table http://emdrive.wiki/Experimental_Results ?

And how should we report the results of rfmwguy and SeeShells and others if they are initially reported as NULL ?

Should we put those results as Null in the the wiki or wait some amount of time (what amount of time ? ) until they perform further experiments and analysis ?
(and if they are initially positive, do we report them right away as positive or do we wait a period of time ?)
« Last Edit: 07/23/2015 03:01 PM by Rodal »

Online RonM

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I think I've lost track of all the DIYers now. Let's see:
1. TheTraveller
2. SeeShells
3. rfmwguy
4. Mulletron (?)
5. klm(?)

Is this on the wiki?
Is the wiki link not supposed to be at the top of the page btw? - can't find it.

Concerning, this, what do people think about reporting NULL results of experimenters ? .

So far we have put in the wiki the information about the Aachen Baby EM Drive guys results as being Null, as hard as they try they are clearly Null, so far (and they have tried different measurements).

However we have not reported as Null the partial results of others (with a question mark on the list).

Should we post those partial null results as NULL in the Wiki experimental results table http://emdrive.wiki/Experimental_Results ?

I think it would be useful to list partial results as they come in, whether they are null or not. Perhaps in a second table to distinguish ongoing experimental series from completed experiments.

Usually, I think it would be best to wait until an experiment is complete before reporting results, but considering the activity of this thread, there is a daily interest in the latest news. And it could help the DIY experimenters by continuing the conversation on designing and running their experiments.

There should be some caveat about the preliminary results being, well, preliminary.

Offline rfmwguy

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I think I've lost track of all the DIYers now. Let's see:
1. TheTraveller
2. SeeShells
3. rfmwguy
4. Mulletron (?)
5. klm(?)

Is this on the wiki?
Is the wiki link not supposed to be at the top of the page btw? - can't find it.

Concerning, this, what do people think about reporting NULL results of experimenters ? .

So far we have put in the wiki the information about the Aachen Baby EM Drive guys results as being Null, as hard as they try they are clearly Null, so far (and they have tried different measurements).

However we have not reported as Null the partial results of others (with a question mark on the list).

Should we post those partial null results as NULL in the Wiki experimental results table http://emdrive.wiki/Experimental_Results ?

And how should we report the results of rfmwguy and SeeShells and others if they are initially reported as NULL ?

Should we put those results as Null in the the wiki or wait some amount of time (what amount of time ? ) until they perform further experiments and analysis ?
(and if they are initially positive, do we report them right away as positive or do we wait a period of time ?)
100% recommend Null results...thats valuable alongside other test data. I'd post it as soon as someone reported it. Guess refutiation is as interesting to me as other data when I study the configuration they were using.

Aachen? Yes, I'd plug it in as Null for Design #1. Note there were a couple of Test Method changes, perhaps Design #1, test methods #1, #2, etc. (hope I said this clearly)

I'd also suggest Design naming, like NSF-1701, not change to NSF-1701A unless a significant mechanical or electrical change was made. Think each DIYer can give you the heads-up on that.




Offline SeeShells

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Regarding using wire mesh,

A wire mesh waveguide is described in https://www.jlab.org/ir/MITSeries/V9.PDF pg 287 with a loss of .4db/m, compared to (typical?) .02db/m. Only ~10%. However, wouldn't one have to multiply that by the expected number of reverberations the wave will traverse? My math on factorials or series is a bit rusty.

$120 for a roll of copper looks pricey compared to the $15 aluminum next to it. Perhaps it can be copper plated? Pretty simple to copper plate.

Another paper on how to hack a magnetron, to work as an amplifier, CW and very (relatively) narrow bandwidth, and use magnetic solenoid tuning:
http://n5dux.com/ham/files/pdf/The%20Magnetron-A%20Low%20Noise%20Long%20Life%20Amplifier.pdf
Nice links. wire mesh intrigued me for several reasons that Doc has summarized. Another one may be the angle of reflection, or better yet, scattering of radiation. Assuming outward vector forces are striking frustum side walls.

I found that article months ago and couldn't locate it again, nice, you may have just made my day!

I've found it interesting and keep coming back to the red flags in the tests.
Air pressure=thrust vs Vacuum=small thrust
This is the 800 pound gorilla sitting in the middle of the lab and nobody wants to poke it. :D

I picked the Perforated copper sheets (not *wire mesh* it's not as good in making a resonating cavity) for a couple reasons and not all listed here, because the boundary conditions of the incident reflected wave actions are not quite the same across a hole boundary as they are from solid copper surface. (we also can see the pretty lights inside). I think I can poke this gorrilla through the holes. I think there are some loopholes in Maxwell's theories that can be taken advantage of.

I'll fill this thought out later as I have some more goodies to pick up for the test bed in town. See ya'll in a couple hours.

Shell

Offline SeeShells

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I think I've lost track of all the DIYers now. Let's see:
1. TheTraveller
2. SeeShells
3. rfmwguy
4. Mulletron (?)
5. klm(?)

Is this on the wiki?
Is the wiki link not supposed to be at the top of the page btw? - can't find it.

Concerning, this, what do people think about reporting NULL results of experimenters ? .

So far we have put in the wiki the information about the Aachen Baby EM Drive guys results as being Null, as hard as they try they are clearly Null, so far (and they have tried different measurements).

However we have not reported as Null the partial results of others (with a question mark on the list).

Should we post those partial null results as NULL in the Wiki experimental results table http://emdrive.wiki/Experimental_Results ?

And how should we report the results of rfmwguy and SeeShells and others if they are initially reported as NULL ?

Should we put those results as Null in the the wiki or wait some amount of time (what amount of time ? ) until they perform further experiments and analysis ?
(and if they are initially positive, do we report them right away as positive or do we wait a period of time ?)
Preliminary or static tests can be listed in the chart, if reported. It categorizes them not as a fully functioning test to achieve thrust.

Offline Ricvil

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Ignore this if it's already posted, but you may want to have a look at this paper:

http://arxiv.org/pdf/1302.2537v1.pdf

"Newton’s Third Law in the Framework of Special Relativity"

The conclusions are pretty juicy, I quote part of them:

"We have shown in this paper that in general Newton’s third law is not compatible with the principles of special relativity and the total force on a two current loop system is not zero"

Then discusses how to get constant (reactionless!) force using two wires of conducting material, one with constant direct current and the other carefully modulated, if I understand the paper well enough,.

It is just a directional "two loop" antenna. The net force becomes from non isotropic asymmetrical radiaton pattern of the antenna.

Offline frobnicat

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Ignore this if it's already posted, but you may want to have a look at this paper:

http://arxiv.org/pdf/1302.2537v1.pdf

"Newton’s Third Law in the Framework of Special Relativity"

The conclusions are pretty juicy, I quote part of them:

"We have shown in this paper that in general Newton’s third law is not compatible with the principles of special relativity and the total force on a two current loop system is not zero"

Then discusses how to get constant (reactionless!) force using two wires of conducting material, one with constant direct current and the other carefully modulated, if I understand the paper well enough,.

It is just a directional "two loop" antenna. The net force becomes from non isotropic asymmetrical radiaton pattern of the antenna.

This was discussed in thread 2, thing is for a "propulsive effect" of constant thrust it relies on a non stationary ever increasing current :
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1350655#msg1350655


Offline dumbo

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This was discussed in thread 2, thing is for a "propulsive effect" of constant thrust it relies on a non stationary ever increasing current :
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1350655#msg1350655

They also have a more recent paper called "Relativistic Engine Based on a Permanent Magnet" (from July 13, 2015). The link is: http://lib-arxiv-008.serverfarm.cornell.edu/pdf/1507.02897v1.pdf

Offline Rodal

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I thought I would chime in with questions for the AIAA conference. I am going to be attending the event, so I will be able to report back to you guys about what happens, other questions that were asked, etc.
Let me know of a couple of definite questions that anyone would want me to ask during the Q and A,
AIAA Propulsion and Energy Forum and Exposition
Hilton Orlando, Orlando, Florida...
TUESDAY, JULY 28, 2015  NFF-04. Future Flight Propulsion Systems  ...5:00 PM - 5:30 PM
Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects Martin Tajmar

Suggested questions to Prof. Tajmar arranged in order of importance:


Q1. What is the explanation for the very low Q (only 50) in your EM Drive experiments?.  Shawyer has reported Q=45,000 for his Demonstrator at your same tested frequency of 2.45 GHz. Is it because you did not use the usual waveguide isolator and 3-stub tuner between the magnetron and test article?

Has Prof. Tajmar's team grossly over-coupled the RF input to the EM Drive copper truncated cone?  Over-coupling is a matter of putting a larger resistive load on the resonant cavity by shunting more of the source load onto the cavity. Over-coupling can give  an "equivalent" bandwidth which includes more than one mode.

Was Tajmar trying to match it w/ ~ 50 MHz  ? How wide was the high filament current magnetron bandwidth?.

_____________________________________________________

Q2. why your experiments show approximately 60% different thrust force measurements when the EM Drive was physically rotated 180 degrees from the "forward" thrust tests to the "reverse" thrust tests?  Shouldn't the thrust be the same regardless of space orientation?  Is this orientation-dependence indicative of an experimental artifact or a dependence on an external field ?

_____________________________________________________


Q3. Does Prof. Tajmar think that the reason why Shawyer and Yang claimed much higher thrust (over 1,000 to 10,000 times greater force/InputPower than what Tajmar measured) is because Shawyer and Yang reported tests at ambient pressure (unlike Prof. Tajmar who has performed his tests in a vacuum), and Shawyer and Yang just reported thermal convection artifacts? If, not a nullification due to Shawyer and Yang not performing tests in vacuum, what does Prof. Tajmar think that the huge difference (1,000 to 10,000 times) is due to ?

_____________________________________________________

Q4:  What does Prof. Tajmar think about the "motor", "generator" conjecture of Shawyer?: that the EM Drive will not register a significant acceleration unless motivated to do so by vibrations of unspecified magnitude and frequency to produce initial acceleration in the direction pointing from the big base to the small base.  Does Prof. Tajmar think that the reason why he measured much lower thrust is because he didn't vibrate the EM Drive to provide such initial condition?
« Last Edit: 07/23/2015 05:51 PM by Rodal »

Offline deltaMass

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Ignore this if it's already posted, but you may want to have a look at this paper:

http://arxiv.org/pdf/1302.2537v1.pdf

"Newton’s Third Law in the Framework of Special Relativity"

The conclusions are pretty juicy, I quote part of them:

"We have shown in this paper that in general Newton’s third law is not compatible with the principles of special relativity and the total force on a two current loop system is not zero"

Then discusses how to get constant (reactionless!) force using two wires of conducting material, one with constant direct current and the other carefully modulated, if I understand the paper well enough,.
Another photon rocket, I think
http://www.talk-polywell.org/bb/viewtopic.php?f=10&t=5940&start=15#p120645
At least that's a peer-reviewed version.
I'll take a closer look nonetheless.

Offline aero

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Because EW is using real world materials with analog sources, not discretized sources and idealized copper that doesn't seem to heat or suffer significant losses of any sort. Perhaps, just guessing here, perhaps if the node granularity was less than the skin depth of the copper, we could see more realistic skin effects. But its not so we can't.

I'm currently running some tests using MIT's starcluster to automate a cluster of meep servers. Using a higher resolution setting in meep of course is much slower, but I think it may allow for more parallelism. If that proves to be true, higher resolutions could be run at a more feasible speed at the expense of using a more costly cluster of servers. Would that be helpful to you folks?

Yes it would.

My point of Node granularity being less than skin depth is simply that with the current resolution, node granularity, being about 1.2 mm, is about 1000 times larger than skin depth, and it is within the skin where the losses must occur. This is true for both the sides and the ends. As Dr. Rodal posted, Q is inversely proportional to losses but running at the current resolution meep cannot "sample" the skin depth so losses there don't exist in the numerical model. Hence the only "known" source of losses is ignored --> very high Q.

I addressed this issue late last year on the meep-discuss mailing list and got two responses.

First response, can meep use a high resolution for the geometry of the skin while low resolution in the rest of the lattice where 10 nodes per wavelength is adequate? The response was no, meep doesn't do that but perhaps I should use a commercial software as some do have that capability, or alternatively as the source code is available, I am welcome to write my own functions.

Second response, which we may now have the talent to address here was,

"Fictitious materials can be used in place of the metal skin, materials designed to have a gross response like copper except that the response occurs over a much greater skin depth more suitable to the resolution at which the model runs."

I still have no idea how to design such a material (a Drude model of some sort) but it would be straight forward to increase the thickness of the cavity material in the model, within reason, to accommodate such a fictitious material.
Retired, working interesting problems

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