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#1020
by
Bob Woods
on 07 May, 2019 18:49
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Way back in the EM Drive stone age, around 2015, RFMWGUY ran his test on a teeter-totter setup with his frustum small end up and small end down in tests.
That's right! I had forgotten that. Weren't there thermal issues also involved?
Dave's frustum was not a sealed unit, it was shaped using wire mesh. I think part of that was to reduce ballooning and because it was easier/cheaper for him to fabricate. Nevertheless, the solid end-plates in a vertical orientation would still present a possible convection trapping sail. He did use liquid metal contacts, but I think they didn't work too well due to surface resistance and that fact it was a teeter-totter setup.
It WAS exciting to see the videos, and a whole lot of people around the world tuned in.
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#1021
by
PotomacNeuron
on 08 May, 2019 02:54
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Dave's frustum was not a sealed unit, it was shaped using wire mesh. I think part of that was to reduce ballooning and because it was easier/cheaper for him to fabricate. Nevertheless, the solid end-plates in a vertical orientation would still present a possible convection trapping sail. He did use liquid metal contacts, but I think they didn't work too well due to surface resistance and that fact it was a teeter-totter setup.
It WAS exciting to see the videos, and a whole lot of people around the world tuned in.
He later abandoned liquid metal contacts. His final results were without liquid metal contacts.
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#1022
by
RERT
on 08 May, 2019 10:48
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...Again, it sounds like the gist of your "hypothesis" is to point the cone up or down, expecting a different result, because... well, because you think that space is not isotropic on the Earth's surface.
...Space is isotropic.
Well, no, it isn't. There is a gravity field, which picks out a particular direction. In order to think this might affect the EMdrive results, you have to postulate a hitherto unknown interaction between the EM fields and gravity, which I did. In that case the anisotropy due to gravity might matter, and therefore the direction of measurement.
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#1023
by
JohnFornaro
on 08 May, 2019 12:49
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... you have to postulate a hitherto unknown interaction between the EM fields and gravity...
Thank you and have a nice day.
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#1024
by
dustinthewind
on 08 May, 2019 13:14
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Way back in the EM Drive stone age, around 2015, RFMWGUY ran his test on a teeter-totter setup with his frustum small end up and small end down in tests.
That's right! I had forgotten that. Weren't there thermal issues also involved?
Thermal ballooning would always cause a rise so it was supposed that flipping the frustum over one could get the offset and that would be thrust.
Other problems pointed out I think we're thermal expansion of cables and support arms. Thermal convection if one side of the frustum were hotter than the other side. This might have been possible because electric fields on one side were generally larger at the small end where as the larger end had more surface area. I suggested putting it in a bubble to keep it from having an open system to trap air flow so momentum should remain zero. I think there were some other suggestions.
Ultimately improving the thrust to significant levels could have solved a lot of issues if thrust was there.
One thought was that the dielectric insert in the EM drive was replicating a mach effect via some response of the material to the electric fields. I think they were supposing this would be a 2f response of the material to the 1f electric signal in the cavity.
The top half is an illustration of the relationship between driving frequency and fibre response frequency for an electrostrictive material, showing the characteristic frequency-doubling effect that can distinguish electrostriction from other forms of electromechanical transduction, such as piezoelectricity
The frequencies would have been much higher at microwave frequencies. Not sure the material could have responded that quickly at those frequencies.The em cavity would be the anchor and the dielectric would be the accelerated mass.
f being frequency. Mixing the frequencies in the proper phase creates asymmetric acceleration on the material.
https://forum.nasaspaceflight.com/index.php?topic=42978.msg1806976#msg1806976
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#1025
by
meberbs
on 09 May, 2019 05:46
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In order to think this might affect the EMdrive results, you have to postulate a hitherto unknown interaction between the EM fields and gravity, which I did.
You have yet to provide an actually falsifiable hypothesis.
"There might be some unknown relationship between EM fields and gravity" does not meet that condition. Even if you did come up with a version that has enough specifics to be falsifiable, you still haven't even attempted to answer the question you have been asked repeatedly which is: What logical reason do you have to propose such a relationship? So far the only reason implied by your posts is pure wishful thinking on your part which is not a good reason for anyone to spend time investigating what would certainly end up being a dead end.
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#1026
by
meberbs
on 09 May, 2019 06:05
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One thought was that the dielectric insert in the EM drive was replicating a mach effect via some response of the material to the electric fields. I think they were supposing this would be a 2f response of the material to the 1f electric signal in the cavity.
No, harmonics are a thing that comes up in non-linear media, not linear media like dielectrics.
And as I stated in the Woodward thread, your graphs are not based on anything physical, so they don't show "asymmetric acceleration" because they are not graphs of acceleration. Even if they were, there is still an equal up slope for every down slope, and if you average over a period, you would get a result of exactly 0, so the graphs are not even as asymmetric as you think, so there is not a plausible way to get from them to "asymmetric acceleration" anyway.
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#1027
by
JohnFornaro
on 09 May, 2019 11:43
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So far the only reason implied by your posts is pure wishful thinking on your part which is not a good reason for anyone to spend time investigating what would certainly end up being a dead end.
Well, at least we tried.
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#1028
by
RERT
on 09 May, 2019 13:13
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You have yet to provide an actually falsifiable hypothesis.
..."There might be some unknown relationship between EM fields and gravity" does not meet that condition.
...What logical reason do you have to propose such a relationship?
The falsifiable hypothesis is implicitly that is you measure an EMdrive pointing up or down, you might measure different thrust to if it is pointing in a horizontal direction. It is hard to think of anything more directly falsifiable.
A postulate of 'some unknown relationship with gravity' is not sufficient for much, but it is sufficient to indicate that orientation of the EMdrive *might* be significant. Details are not always necessary.
As regards logical reasons to propose this, if EMdrive works it breaks physical laws. If it operates at all, some as yet unknown or unexpected interaction with gravity is one of the most incremental proposals one can make.
I said earlier that I think this is a tiny hole in the null data for the EMdrive, and I stand by that. Note the adjective.
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#1029
by
meberbs
on 09 May, 2019 13:55
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The falsifiable hypothesis is implicitly that is you measure an EMdrive pointing up or down, you might measure different thrust to if it is pointing in a horizontal direction. It is hard to think of anything more directly falsifiable.
No, it is completely unfalsifiable because it does not even involve numbers. No matter what measurements are done, it would always be unfalsifiable, because it could always be said "but maybe the force is smaller than the measurement sensitivity" or "maybe it was the wrong mode shape to trigger the magic interaction." Your statements are about as unfalsifiable as they get.
A postulate of 'some unknown relationship with gravity' is not sufficient for much, but it is sufficient to indicate that orientation of the EMdrive *might* be significant. Details are not always necessary.
No, it is not sufficient for anything. We are talking about science here, details are absolutely necessary.
As regards logical reasons to propose this, if EMdrive works it breaks physical laws. If it operates at all, some as yet unknown or unexpected interaction with gravity is one of the most incremental proposals one can make.
It has effectively been shown that the emDrive does not work. It does not matter how "incremental" your proposal is, there is always a next assumption someone can make up to send others down a wild goose chase. What you have provided here does not constitute a "logical reason." The reasoning you provided here equally works for "maybe it needs to be in no more than a lunar gravity field equivalent" "maybe it needs higher order mode shapes" "maybe it only works with higher/lower frequencies than have been tested" "maybe it needs to be an asymmetric hourglass shape" etc.
For a while I have been poking at statements like this, because because this is the trap pseudoscience concepts always get stuck in. With poor definitions and lack of logical reasons for an effect to exist, there is always another "what-if" and it is even worse when the person proposing them is not even willing to put their money where their mouth is.
I said earlier that I think this is a tiny hole in the null data for the EMdrive, and I stand by that. Note the adjective.
Nope, your adjective is wrong, the hole you are pointing to is either infinite in size (inherent to it not being falsifiable) or nonexistent (due to the fact that it is simply unscientific due to its unfalsifiability, and should be ignored.)
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#1030
by
dustinthewind
on 10 May, 2019 06:59
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One thought was that the dielectric insert in the EM drive was replicating a mach effect via some response of the material to the electric fields. I think they were supposing this would be a 2f response of the material to the 1f electric signal in the cavity.
No, harmonics are a thing that comes up in non-linear media, not linear media like dielectrics.
And as I stated in the Woodward thread, your graphs are not based on anything physical, so they don't show "asymmetric acceleration" because they are not graphs of acceleration. Even if they were, there is still an equal up slope for every down slope, and if you average over a period, you would get a result of exactly 0, so the graphs are not even as asymmetric as you think, so there is not a plausible way to get from them to "asymmetric acceleration" anyway.
Well its been a long time but I thought Dr Rodal thought one of the materials they used had an electrostrictive response. Looking it up. Here is something.
...Regarding electrostriction and gravitation, the Mach Effect theory of Woodward and Fearn is based on the theory of gravitation of Hoyle and Narlikar, or actually just based on general relavitivity plus advanced waves, where electrostriction is used in present experiments to give a 2 omega excitation in addition to the excitation at frequency omega that can be provided by a piezoelectric effect or independently by other means. In the case of the EM Drive, one could conceive of an excitation at frequency omega of the electromagnetic fields and a separate excitation at 2 omega resulting from the electrostriction effect in the HDPE or PTFE polymer insert, or just the electrostiction in the copper material skin depth.
...Yes, the energy density, and the Maxwell stress, and the Poynting vector are all oscillating at 2 omega where omega is the frequency of the electromagnetic fields. The E field at omega produces an electrostrictive strain (and hence an elastic stress) on the HDPE or the PTFE also at frequency 2 omega.
Both the electromagnetic forces (Maxwell stress and Poynting vector) and the electrostrictive forces are all acting at the same frequency 2 omega.
The electrostrictive force is out of phase with the electromagnetic force (due to tan delta) a very small amount (delta), which does give a small effect
Tan delta
PTFE ("Teflon") 0.00028 @ 3 GHz
HDPE 0.00031 @ 3 GHz
So delta is only 0.016 degrees (1/62 of a degree), 0.018% of 90 degrees...
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#1031
by
RERT
on 10 May, 2019 09:37
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Meberbs -
I've never sent anybody on a wild goose chase. I think the right response to this is that if someone was already committed to starting a test campaign for an EMdrive in a vacuum chamber, they should consider measuring on three axes just to be very thorough. That's the nature of the tiny hole.
I suspect the pushback I'm getting on this is due to the judgement, which I share, that there is a low probability of this idea leading to anything. But nonetheless it is a correct idea, especially in the context of the title of the forum 'New Physics for Space Technology'.
I don't propose to respond to your other comments, though I disagree with most: I accept that constant addition of bells/whistles to keep a theory alive is generally negative. However, the impact of what I said in para 1 above is not great.
I'm done on this.
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#1032
by
Ricvil
on 10 May, 2019 09:53
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One thought was that the dielectric insert in the EM drive was replicating a mach effect via some response of the material to the electric fields. I think they were supposing this would be a 2f response of the material to the 1f electric signal in the cavity.
No, harmonics are a thing that comes up in non-linear media, not linear media like dielectrics.
And as I stated in the Woodward thread, your graphs are not based on anything physical, so they don't show "asymmetric acceleration" because they are not graphs of acceleration. Even if they were, there is still an equal up slope for every down slope, and if you average over a period, you would get a result of exactly 0, so the graphs are not even as asymmetric as you think, so there is not a plausible way to get from them to "asymmetric acceleration" anyway.
Well its been a long time but I thought Dr Rodal thought one of the materials they used had an electrostrictive response. Looking it up. Here is something.
...Regarding electrostriction and gravitation, the Mach Effect theory of Woodward and Fearn is based on the theory of gravitation of Hoyle and Narlikar, or actually just based on general relavitivity plus advanced waves, where electrostriction is used in present experiments to give a 2 omega excitation in addition to the excitation at frequency omega that can be provided by a piezoelectric effect or independently by other means. In the case of the EM Drive, one could conceive of an excitation at frequency omega of the electromagnetic fields and a separate excitation at 2 omega resulting from the electrostriction effect in the HDPE or PTFE polymer insert, or just the electrostiction in the copper material skin depth.
...Yes, the energy density, and the Maxwell stress, and the Poynting vector are all oscillating at 2 omega where omega is the frequency of the electromagnetic fields. The E field at omega produces an electrostrictive strain (and hence an elastic stress) on the HDPE or the PTFE also at frequency 2 omega.
Both the electromagnetic forces (Maxwell stress and Poynting vector) and the electrostrictive forces are all acting at the same frequency 2 omega.
The electrostrictive force is out of phase with the electromagnetic force (due to tan delta) a very small amount (delta), which does give a small effect
Tan delta
PTFE ("Teflon") 0.00028 @ 3 GHz
HDPE 0.00031 @ 3 GHz
So delta is only 0.016 degrees (1/62 of a degree), 0.018% of 90 degrees...
At some point, aero was oriented to use rubber teflon gaskets.
I think it has a nonlinear Kerr response.
Then fractal patterns appears on the simulations.
And...no one want to proceed with "noisy" simulations.
End of history.
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#1033
by
vi4apaev
on 10 May, 2019 10:49
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#1034
by
TheTraveller
on 11 May, 2019 07:48
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Enjoyed lunch and a long discussion with Roger Shawyer in London. Next day a repeat session with Mike McCulloch.
Roger is presenting a new EmDrive paper at IAC 2019
EMDRIVE THRUST/LOAD CHARACTERISTICS. THEORY, EXPERIMENTAL RESULTS AND A MOON MISSION.
https://iafastro.directory/iac/paper/id/48783/summary/Slide 11 forward has some of the information, which is based on very recent testing of the recovered Flight Thruster.
http://www.emdrive.com/shrivenhampresentation2019.pdfOther exciting news is in the works as per the statement in the abstract:
With the technology now maturing, it is time for EmDrive to come out of the shadows
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#1035
by
RonM
on 11 May, 2019 17:47
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TheTraveller posted on 8 June 2018:
It will be interesting reading the comments after everybody sees the KISS thruster going round and round on the KISS rotary test rig.
Until then no more comments on theory from me. Time now to get ready to fabricate the frustum. Lots of photos will be posted of the process.
Frustum fab is currently on hold awaiting the delivery of the Silver Epoxy and the 2 Cu sheets.
Next in the delivery Q is the miniVNA tiny+ that is needed to tune the coupler.
Then need the delivery of the 100W Rf amp and 22650 Lithium Ion rechargeable batteries and battery holders.
After which the demo system can be put together and it gets interesting.
It Is Time For The EmDrive To Come Out Of The Shadows and For EmDrive DIYers To Stop Wasting Time and Money On Builds and Test Rigs That WILL NOT Generate Significate Force
https://forum.nasaspaceflight.com/index.php?topic=42978.msg1829061#msg1829061Whatever happened to the KISS thruster? We're still waiting for the photos and posts of the progress you promised.
You've promised this KISS thruster for years and have never delivered. My guess is either you never built it or it didn't work. Prove me wrong with a video of your KISS thruster in action and show the test data.
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#1036
by
TheTraveller
on 12 May, 2019 08:35
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Whatever happened to the KISS thruster? We're still waiting for the photos and posts of the progress you promised.
You've promised this KISS thruster for years and have never delivered. My guess is either you never built it or it didn't work. Prove me wrong with a video of your KISS thruster in action and show the test data.
Hi RonM,
Understand your frustration, which I share. Building EmDrives is not simple, easy, quick nor low cost no matter what the approach. I was wrong to believe it could be done. Please accept my apology for not delivering what I tried to achieve. Current plans are to demo the commercial thruster we are working on once we have orbital test data and have done a commercial release.
I can share that Roger never made a dual flat end plate cavity. Every cavity he ever made, to my knowledge, had some form of shaped end plates. Which says the EW cavity and all those that followed are not good designs due to the massive phase distortion of the travelling waves introduced by flat end plates. It appears that FEKO is not good at modelling what happens inside a cavity where the travelling waves reflect between the end plates 10,000s of times and path length variations generate large phase alterations that effectively destroy the standing waves FEKO models.
Additionally the interior surface needs to be mirror like, with no dips, pits, peaks, scratches, etc. This is so highly critical a requirement as to dominate the need for very low phase distortion in the travelling wave end plate reflections. Antioxidation surface coating are bad news. Our cavity needs to operate at LEO vacuum levels and be filled with a noble gas during storage and transport to stop Cu oxidation. None of this is easy, nor low cost. So no KISS thruster.
Solid data is coming as are commercial products.
Plus Roger told me his IAC 2019 paper will share new test data, plus photos of his test rig.
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#1037
by
meberbs
on 12 May, 2019 15:07
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Understand your frustration, which I share. Building EmDrives is not simple, easy, quick nor low cost no matter what the approach. I was wrong to believe it could be done. Please accept my apology for not delivering what I tried to achieve. Current plans are to demo the commercial thruster we are working on once we have orbital test data and have done a commercial release.
Since you have for the countless time not provided pictures, it can only be concluded that you did not in fact bother actually building anything. An orbital demo is pointless, just being able to counteract drag in LEO means enough force to measure on the ground with good setups like other experimenters have used. The uncertainties involved in drag calculations in space means that without forces that should easily be demonstrable on the ground you won't prove anything in space.
I can share that Roger never made a dual flat end plate cavity. Every cavity he ever made, to my knowledge, had some form of shaped end plates.
See attached picture from Shawyer's website. Your statement is so blatantly false it is absurd. Shawyer would have had to actively lie to people that he originally advised on the design of the emdrive for your statement to be true, even if your statement was not contradicted by actual pictures.
It appears that FEKO is not good at modelling what happens inside a cavity where the travelling waves reflect between the end plates 10,000s of times and path length variations generate large phase alterations that effectively destroy the standing waves FEKO models.
As usual, you have yet to provide a single example of a case where FEKO and other tools fail to accurately describe what happens in a cavity. Models have accurately predicted resonance frequencies, mode shapes, and Q factors for every cavity that has been tested to date to within the mechanical tolerance of the builds. You have been repeatedly asked to provide a single example where such models fail and have not done so.
Additionally the interior surface needs to be mirror like, with no dips, pits, peaks, scratches, etc. This is so highly critical a requirement as to dominate the need for very low phase distortion in the travelling wave end plate reflections. Antioxidation surface coating are bad news. Our cavity needs to operate at LEO vacuum levels and be filled with a noble gas during storage and transport to stop Cu oxidation. None of this is easy, nor low cost. So no KISS thruster.
Nonsense. While oxidation can have some small impact on the reflectivity, experimenters have demonstrated more than sufficient performance for the conductivity needs based on any criteria provided to date. You are exaggerating the sensitivity of the low RF frequencies used in experiments to minor imperfections. RF performance would not be significantly affected by anything short of gross mishandling.
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#1038
by
oyzw
on 13 May, 2019 09:17
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I think the shape of resonant electromagnetic field directly affects the thrust size and direction, which is a very sensitive factor. At the same time, I think the conical cavity of TE01X is not enough to form a significant difference in electromagnetic field gradient, and the cavity design is misguided.
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#1039
by
oyzw
on 13 May, 2019 09:25
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Mr. Jamie used two Chambers to carry out the thrust test, where I made the cavity shift response only 1/10, compared to his cavity. At the same time, he also tested the method of increasing horizontal damping, and found no obvious differences. I think that my pleural shape has changed, greatly changing the original electromagnetic field, and the thrust has been greatly reduced.