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#2780 by Monomorphic on 27 May, 2016 12:35
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The assured almost no light gaps and near perfect circle...so mechanically, the thing was about as perfect as I could make it on a home project.
In addition to checking for light through cracks, I filled mine up with water and it didn't leak at all. -
#2781 by TheTraveller on 27 May, 2016 17:06
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Well, I could put an absorptive high-Q lumped-element filter with outrageous insertion loss in line with a frustrum and produce an extreme Q based on RL. Of course, the energy in the cavity, the EM momentum and radiation pressure would be practically zilch. As would any propulsive effect, unless somehow free energy is provoking annoyed quantum-vacuum fairies.
Pardon? Why would a cavity with a really good rtn loss dip, implying a really good resonance VSWR. not do a really good cavity energy fill when Rf at the peak rtn loss freq is applied?
There is no magic here. Fairly straightforward to convert S11 rtn loss dip peak to VSWR and to reflection coefficient or is there something I'm missing?
As to the comment on thrust being relied on quantum-vacuum fairies, well you are, IMO, correct. Roger's theory works very well and does describe all the thrust characteristics that many EmDrive builders, including myself, have measured.
Still waiting on a better EmDrive theory than Roger's that enables engineers to build working EmDrives. So far every build is based on Roger's work even if it does not state that. If the theory can't describe how to build the device and what it's operational characteristics are, then of what validity or use is it? -
#2782 by TheTraveller on 27 May, 2016 17:13
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...
Correct Zellerium. Besides that, recall what is the actual definition of Q, it is:
If we're going to start measuring quality like Mr. Shawyer, then yes I agree its 10 KHz and 244,000 Q. But as far as I can recall everyone else here has always measured quality from -3 dB below 0 which is how EW and NWPU measured theirs.
We would have definitely improved our quality by several orders of magnitude using this other technique.
How do RF component manufacturers typically measure it? There must be some industry standard...
which does not depend on arbitrary definitions of 3 db etc.
NASA obtained excellent agreement between COMSOL calculations of Q (calculated from the above formula based on the conductivity of copper, and the geometry) and compared to their convention on how to measure Q experimentally.
On the other hand, a "measured Q" of 244,000 for this copper frustum does not make sense with any calculation, particularly for a TM013 mode shape, which should be under 100,000 under the best of circumstances.
Unloaded Q can be directly measured. Just need to measure the time for forward power to climb from zero to 63% of max value as that is 1 TC of cavity fill time, from which unloaded Q can be directly obtained with NO need to measure bandwidth.
I gave up long ago using the low cost VNAs to do anything more than a quick method to search for resonant freq and to do rough antenna design, placement and orientation.
I now use the forward and reflected power feedback from my Rf amp to determine frustum resonance freq, based on lowest VSWR and forward power dropping to 50% the peak value to determine VSWR bandwidth.
BTW thrust bandwidth is very much smaller than VSWR or VNA bandwidth, which has been confirmed by another EmDrive builder as well as Roger. -
#2783 by TheTraveller on 27 May, 2016 17:20
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.../...
Didn't they have their amplifier in the vacuum chamber for this experiment? And didn't they say it was "dying"?
Yes the capacitors was problematic as far as I remember but this was fixed.
On the other hand, the power was adjustable.
... quote from Brady et al. 2014 report ...
None of the experiments covered in the 2014 Brady et al. report was actually in vacuum, although they were indeed in a vacuum chamber. The best "anomalous force/apparently spent power" ratio for TE012 with 2.6W was obtained at atmospheric pressure, and the comments about difficulty of getting a stable TE012 mode (that might explain the low absolute power and at least why it was not pursued) can't be linked to difficulties specific to vacuum, I think.
This asks also the question of what part (if any) of that good figure of merit ratio would subsist if it was tested in vacuum, all other things being equal at EagleWorks test stand, as with others modes the later communications by Paul March here at NSF indicated a very significant decrease in anomalous force per power when operated in vacuum conditions (for a very few shared plots actually), if I recall. Aside speculative hypothesis about the role of atmospheric pressure inside the vessel for a speculative real "propellantless thrust", the most natural interpretation for skeptics of such consequence is simply that vacuum removes one source (among others) of spurious coupling between tested device (and testing apparatus) and immediate surroundings : i.e. the role of atmospheric pressure in higher anomalous force magnitudes would to be found outside the vessel, convection etc... or between inside and outside in case of warm "jets" or other gas outbursts. More elaborate "pathological" conditions can also apply, for instance in vacuum less adsorbed water content in the nylon screws hence less bulk microwave induced heating of those. Mmm... melted nylon screws!
Those reports on anomalous measurements should come with a hundred pages of annexes or even just a link to scanned lab. notebook full of details... that would spare us months of discussions on interpretations (of what is a "reversal" for instance) and years of waiting the next report holding on silly hypothesis.
While not letting the cat out of the bag, several EmDrive builders, that have reported thrust, are building rotary test rigs to go to the next step beyond just achieving and measuring thrust. They are setting up the systems to measure and determine the CofM and CofE biggie questions.
Stay sharp, 2016 is going to be, as I stated earlier, a very interesting year. -
#2784 by TheTraveller on 27 May, 2016 18:01
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The assured almost no light gaps and near perfect circle...so mechanically, the thing was about as perfect as I could make it on a home project.
In addition to checking for light through cracks, I filled mine up with water and it didn't leak at all.
My 8mN frustum was gravity stacked as no flanges to bolt on the end plates. Is now away having big and small end flanges machined and silver soldered to the frustum side walls so it will look like the attached.
Flanges are increased to 5mm thick.
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#2785 by mwvp on 27 May, 2016 18:23
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Also there is a lot of good descriptions about Q measurement available at the net.
This for example:
http://www.engineering.olemiss.edu/~eedarko/experience/rfqmeas2b.pdf
http://forum.nasaspaceflight.com/index.php?topic=39214.msg1510595#msg1510595
Great primer, thanks for the links. If you can't make a two-port measurement, a single-port complex measurement could do. Had forgotten about seeing that several months back. -
#2786 by mwvp on 27 May, 2016 18:30
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Reality is I spent hours polishing and planing thick endplates to a flatness level manufacturing would not invest in. Also, sidewalls polished with precious few dents and dings on 1.2 mil copper. Got the best silver solder and thermal cured silver epoxy I could afford. Sneaked the frustum into my wifes stove for curing and was never caught.
...
Sounds outstanding, best wishes. Keep in mind, non food-grade or reagent chemicals, made on-the-cheap in less than state of the art conditions have been in some cases, and may be contaminated with nasty stuff, which can out-gas and may contaminate your dinner. I got a couple toaster ovens from the 2nd hand shops for my soldering and plastics.
Apologies for getting a bit cranky and factitious, I let some other issues spill over. Oops. -
#2787 by mwvp on 27 May, 2016 18:58
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Well, I could put an absorptive high-Q lumped-element filter with outrageous insertion loss in line with a frustrum and produce an extreme Q based on RL. Of course, the energy in the cavity, the EM momentum and radiation pressure would be practically zilch. As would any propulsive effect, unless somehow free energy is provoking annoyed quantum-vacuum fairies.
Pardon? Why would a cavity with a really good rtn loss dip, implying a really good resonance VSWR. not do a really good cavity energy fill when Rf at the peak rtn loss freq is applied?
There is no magic here. Fairly straightforward to convert S11 rtn loss dip peak to VSWR and to reflection coefficient or is there something I'm missing?
As you said, it implies, not proves the energy is actually in the frustrum making radiation pressure rather than being absorbed somewhere else; connectors, coax, coupler, et.
Besides, measuring the E or B field in the frustrum at several points is, IMHO, very useful, if not really necessary to prove, beyond doubt, that a traveling wave at Vg is in fact propagating from apex to base, and to measure the Doppler effect with acceleration.
A complex measurement with a VNA, rather than a scalar VSWR measure, would also better characterize the system....
Roger's theory works very well and does describe all the thrust characteristics that many EmDrive builders, including myself, have measured.
Still waiting on a better EmDrive theory than Roger's that enables engineers to build working EmDrives. So far every build is based on Roger's work even if it does not state that. If the theory can't describe how to build the device and what it's operational characteristics are, then of what validity or use is it?
I agree. I'm surprised at the skepticism towards aspects of Rogers theory, but it is understandable. It seems to me that without dissipation, energy will counter-propagate at Vg leading to no net momentum. But with dissipation, and even greater dissipation for the lower Doppler shifted sideband at the base, a traveling wave caries momentum from the apex to the base. No dissipation, no travelling wave, and no momentum imbalance or thrust.
Of course, this is not a closed system. I describe an open system as the frustrum radiates as heat the momentum that would otherwise cancel the forward thrust.
I think Shawyer well knows this, and is keeping it as part of his trade-secrets.
I am still working on demonstrating it. I spent a couple weeks watching near a hundred hours of UTEP Prof. Rumps' EM course videos and lecture notes, then finished about half of MITs Prof. Strang's linear algebra course so I really understand the mechanics of matrices and Eigenmode calculations for fdfm. Then a family member went in to the hospital a month ago, so I've been a bit distracted and set back.
I would have thought X-Ray or Dr. Rodal would have done this trivially or off-hand months ago but it seems conical resonators, especially with dissipation isn't a popular topic in the literature. -
#2788 by mwvp on 27 May, 2016 19:06
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Unloaded Q can be directly measured. Just need to measure the time for forward power to climb from zero to 63% of max value as that is 1 TC of cavity fill time, from which unloaded Q can be directly obtained with NO need to measure bandwidth.
LOL, but you are measuring the bandwidth when you measure the rise-time of the envelope.
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#2789 by TheTraveller on 27 May, 2016 19:13
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Unloaded Q can be directly measured. Just need to measure the time for forward power to climb from zero to 63% of max value as that is 1 TC of cavity fill time, from which unloaded Q can be directly obtained with NO need to measure bandwidth.
LOL, but you are measuring the bandwidth when you measure the rise-time of the envelope.
Yup but not by measuring some point on the side of a curve. Is not possible to get the 1 TC rise time measurement wrong. However hundreds of pages here are gone into how to measure or not the Q by using VNA S11 or S21 techniques. Total waste as Roger advised me and as I found out.
Doing forward power dropping to 50% (3dB) or the 1 TC rise time method works very well. As I stated earlier doing VNA measurements for more than resonance is a waste and I never do it anymore.
BTW the official SPR method is to attach a power meter via a sample port and attenuator. Then apply specified working power and tune freq for max power from the sample port, then retune for the side freq that give 50% power from the sample port.
Hard to fault that method. -
#2790 by Rodal on 27 May, 2016 19:14
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Well, I could put an absorptive high-Q lumped-element filter with outrageous insertion loss in line with a frustrum and produce an extreme Q based on RL. Of course, the energy in the cavity, the EM momentum and radiation pressure would be practically zilch. As would any propulsive effect, unless somehow free energy is provoking annoyed quantum-vacuum fairies.
Pardon? Why would a cavity with a really good rtn loss dip, implying a really good resonance VSWR. not do a really good cavity energy fill when Rf at the peak rtn loss freq is applied?
There is no magic here. Fairly straightforward to convert S11 rtn loss dip peak to VSWR and to reflection coefficient or is there something I'm missing?
As you said, it implies, not proves the energy is actually in the frustrum making radiation pressure rather than being absorbed somewhere else; connectors, coax, coupler, et.
Besides, measuring the E or B field in the frustrum at several points is, IMHO, very useful, if not really necessary to prove, beyond doubt, that a traveling wave at Vg is in fact propagating from apex to base, and to measure the Doppler effect with acceleration.
A complex measurement with a VNA, rather than a scalar VSWR measure, would also better characterize the system....
Roger's theory works very well and does describe all the thrust characteristics that many EmDrive builders, including myself, have measured.
Still waiting on a better EmDrive theory than Roger's that enables engineers to build working EmDrives. So far every build is based on Roger's work even if it does not state that. If the theory can't describe how to build the device and what it's operational characteristics are, then of what validity or use is it?
I agree. I surprised at the skepticism towards aspects of Rogers theory, but it is understandable. It seems to me that without dissipation, energy will counter-propagate at Vg leading to no net momentum. But with dissipation, and even greater dissipation for the lower Doppler shifted sideband at the base, a traveling wave caries momentum from the apex to the base. No dissipation, no travelling wave, and no momentum imbalance or thrust.
Of course, this is not a closed system. I describe an open system as the frustrum radiates as heat the momentum that would otherwise cancel the forward thrust.
I think Shawyer well knows this, and is keeping it as part of his trade-secrets.
I am still working on demonstrating it. I spent a couple weeks watching near a hundred hours of UTEP Prof. Rumps' EM course videos and lecture notes, then finished about half of MITs prof. Strange's linear algebra course so I really understand the mechanics of matrices and Eigenmode calculations for fdfm. Then a family member went in to the hospital a month ago, so I've been a bit distracted and set back.
I would have thought X-Ray or Dr. Rodal would have done this trivially or off-hand months ago but it seems conical resonators, especially with dissipation isn't a popular topic in the literature.
Concerning: "I surprised at the skepticism towards aspects of Rogers theory, but it is understandable"
I would appreciate further information as to why you are surprised, given these important facts:
Roger Shawyer is still insisting on an "explanation" that purports to use Maxwell's equations, and Special Relativity to explain self-acceleration of a closed cavity undergoing electromagnetic resonance. It is well known that (see for example any good text on Maxwell's equations, for example Jackson's) that
A) Maxwell's equations by themselves (without any additional statements) fully satisfy Lorentz invariance and Special Relativity. Hence there is no need whatsoever to add any Special Relativity statements to Maxwell's equations (doing so if consistent is superfluous and unnecessary, and if done inconsistently as done by Shawyer, it is incorrect). It does not make sense to try to make Maxwell's equations consistent with Special Relativity because they already are.
B) Maxwell's equations fully satisfy the equations of Conservation of Energy and Conservation of Momentum (without any additional statements). Therefore, it is not possible for a closed cavity to self-accelerate according to Maxwell's equations and Special Relativity. Since this is a well-known fact, people aware of these facts have rejected Shawyer's theory since his article in New Scientist in 2006, and a few have looked for other possible explanations of anomalous forces (for example Dr. White with his Quantum Vacuum theory, Dr. McCulloch based on the Unruh effect, and Dr. Woodward based on his Mach Effect theory, to name a few).
The courses from MIT that you have been listening to should make this (that Maxwell's equations fully satisfy Lorentz transformations and Special Relativity, and that Maxwell's equations fully satisfy Conservation of Momentum and Conservation of Energy) further clear.
I also would appreciate knowing what you are referring to in here "Dr. Rodal would have done this trivially or off-hand months ago" as I need clarification of what are you referring to that we should have done trivially months ago? When you write about an "open system", you mean a system open to what? How can the EM Drive satisfy Lorentz transformations and hence be frame-indifferent?
You may be interested in this derivation:
https://forum.nasaspaceflight.com/index.php?topic=39214.msg1526577#msg1526577
where I show a number of misconceptions regarding stresses, Poynting vector field and travelling waves for the EM Drive.
One of the misconceptions I address is something I discussed with you in the past: that one cannot readily obtain the radiation pressure using the Poynting vector (as usually done in introductory texts) in a resonant cavity. Also, that it is incorrect to discuss single travelling waves in a closed cavity (since a single propagating wave cannot satisfy the boundary conditions of the problem). And of course it is also incorrect to discuss plane electromagnetic waves inside a resonant cavity (they don't satisfy the B.C. either).
---------------
PS: When referring to MIT courses are you referring to Professor Gilbert Strang ? (spelling: instead of "Strange" ?). I took Graduate courses from Prof. Strang (MIT Mathematics Department) while I was at MIT. Great teacher
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#2791 by mwvp on 27 May, 2016 19:51
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Unloaded Q can be directly measured. Just need to measure the time for forward power to climb from zero to 63% of max value as that is 1 TC of cavity fill time, from which unloaded Q can be directly obtained with NO need to measure bandwidth.
LOL, but you are measuring the bandwidth when you measure the rise-time of the envelope.
Yup but not by measuring some point on the side of a curve. Is not possible to get the 1 TC rise time measurement wrong. However hundreds of pages here are gone into how to measure or not the Q by using VNA S11 or S21 techniques. Total waste as Roger advised me and as I found out.
Doing forward power dropping to 50% (3dB) or the 1 TC rise time method works very well. As I stated earlier doing VNA measurements for more than resonance is a waste and I never do it anymore.
BTW the official SPR method is to attach a power meter via a sample port and attenuator. Then apply specified working power and tune freq for max power from the sample port, then retune for the side freq that give 50% power from the sample port.
Hard to fault that method.
+1 for sample ports. The more, the merrier if you measure the phase relation between them as the frustrum accelerates and decelerates.
It sounds like the Official SPR Method is a scalar, two-port frequency domain measurement. Where as, you seem to describe a time-domain measurement of the RF envelope rise (or fall?) time. If the Q is 1000 @ 2 GHz, we're talking a few hundred nano-seconds, with nano-second resolution? Should be too difficult.
Unless its swept pretty slow, a high-Q multi-mode cavity could well produce junk. My experience using a spectrum analyzer on filters is when you sweep them too fast the curve becomes lob-sided. But I would expect anyone doing a build would relish playing around with the signal and video BW so that mistake wouldn't be made.
Looking at the frustrum, its multi-mode but the modes couldn't be better coupled, so its not like a weakly coupled multi-pole filter with a large group delay/ripple (Chebyshev), although being high-Q, and near cutoff, it would be steep on the low frequency end. I would have expected the sweeps to be somewhat lob-sided.
Some measurements are best made in the time domain, other the frequency domain. We swept cellular antennas in the frequency domain and did an inverse-Fourier to get the time domain back, with an expensive network analyzer rather than a cheap TDR because the transmissionlines and antennas were narrow-band. Being a high-Q filter, I wouldn't prefer an impulse analysis of the frustrum.
I don't want to come across as some sort of didactic stickler. A clever/skillful guy could would no doubt do well with a cheap grid-dip meter.
What I really want to see is the RF envelope of the modes in a frustrum, still and under acceleration and deceleration. That's as important to me as thrust measurements, especially to validate Shawyer's calculations. -
#2792 by TheTraveller on 27 May, 2016 19:52
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Hi Guys,
I have just signed a contract to deliver 7 x 0.1N EmDrive thrusters to a company you would all know of. NDA restricts further disclosure as you would appreciate. I will be able to post the rotary test data and video as I insisted it was a pre NDA promise.
Yes there are tests that are needed to complete but nothing that I'm not 100% confident to complete.
So exciting time for the rest of 2016.
Those that think the "Shawyer Effect" is not real, well time to sharpen your pencils or be left behind. -
#2793 by TheTraveller on 27 May, 2016 20:17
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Hi Guys,
Thanks Phil, we can allow commercial chat provided it's emdrive and comes with test data and video you can make public. If any of your project have NDA test data, its best not to acknowledge it. Look forward to some real data...lots of it should be hitting soon.
I have just signed a contract to deliver 7 x 0.1N EmDrive thrusters to a company you would all know of. NDA restricts further disclosure as you would appreciate. I will be able to post the rotary test data and video.
Yes there are tests that are needed to complete but nothing that I'm not 100% confident to complete.
So exciting time for the rest of 2016.
Those that think the "Shawyer Effect" is not real, well time to sharpen your pencils or be left behind.
Thanks Dave,
To my best ability I will continue to provide experimental feedback to how to design basic EmDrives, build them and test them based on what I have done, as example of how to use forward power rise time to determine cavity unloaded Q. Plus other stuff like thrust bandwidth is not VNA nor VSWR bandwidth as you know is totally new information and has been confirmed by Roger and another.
When the rotary high vac tests are completed, will upload the video and test data but I suspect there may be other such rotary test data released before I get there.
What I hope is this forum will switch from theory that claims the EmDrive can't work and all the experimental data is rubbish, to DIY EmDrive builders openly sharing data and the theory guys working to come up with some theory that is better than that of Roger and that is better at being used to design EmDrives.
So far no other theory, including Dr. Mike's, can be used to design and build EmDrives. Just maybe the theory guys here will stop saying it can't work and beaver down to develope a better theory that Roger has presented, because spending brain cpu cycles claiming it can't work is just wasted brain cpu cycles that are doing nothing to advance EmDrive understanding. -
#2794 by meberbs on 27 May, 2016 20:27
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...
You have an interesting definition of "works" considering that Shawyer's theory fails to even correctly predict the direction of the force, as I detailed here. That Feynman quote you keep posting applies to Shawyer's theory as well.
Roger's theory works very well and does describe all the thrust characteristics that many EmDrive builders, including myself, have measured.
Still waiting on a better EmDrive theory than Roger's that enables engineers to build working EmDrives. So far every build is based on Roger's work even if it does not state that. If the theory can't describe how to build the device and what it's operational characteristics are, then of what validity or use is it?
Standard use of Maxwell's electromagnetism has proven useful for predicting resonance and Q (though Q is less accurate due to sensitivity to real world imperfections). Most of the advice you have posted on how to achieve high Q is consistent with standard EM theory, although some has been specific tolerances without any analysis or experimental evidence provided for support. The main difference Shawyer has with standard EM is that the cavity won't resonate below the small end cutoff. I previously asked for an example where an experiment supports the "no resonance below small end cutoff" claim and you did not provide one.
Shawyer's theory does not make any claims about which resonance modes work best, and he has not provided validation that the modes he has excited really are the ones he claims. People have tried to use resonance modes to match his claims, for reasons such as repeating his experimental conditions, and assumptions that he may have unreleased experimental evidence of which modes are best.
You keep saying that Shawyer's theory is required to build EM drives, but I fail to see any aspect of his theory that is helping, and not already available from standard physics, or the "high Q is good" that several other theories also suggest. On the contrary, every time I look at his theory I find contradictions that make it useless for determining anything about how to setup an experiment. -
#2795 by mwvp on 27 May, 2016 20:34
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I'm surprised at the skepticism towards aspects of Rogers theory, but it is understandable. It seems to me that without dissipation, energy will counter-propagate at Vg leading to no net momentum. But with dissipation, and even greater dissipation for the lower Doppler shifted sideband at the base, a traveling wave caries momentum from the apex to the base. No dissipation, no travelling wave, and no momentum imbalance or thrust.
Of course, this is not a closed system. I describe an open system as the frustrum radiates as heat the momentum that would otherwise cancel the forward thrust.
I think Shawyer well knows this, and is keeping it as part of his trade-secrets.
I am still working on demonstrating it. I spent a couple weeks watching near a hundred hours of UTEP Prof. Rumps' EM course videos and lecture notes, then finished about half of MITs prof. Strange's linear algebra course so I really understand the mechanics of matrices and Eigenmode calculations for fdfm. Then a family member went in to the hospital a month ago, so I've been a bit distracted and set back.
I would have thought X-Ray or Dr. Rodal would have done this trivially or off-hand months ago but it seems conical resonators, especially with dissipation isn't a popular topic in the literature.
Concerning: "I surprised at the skepticism towards aspects of Rogers theory, but it is understandable"
I would appreciate further information as to why you are surprised, given these important facts:
1) Roger Shawyer is still insisting on an "explanation" that purports to use separate results from Maxwell's equations, and Special Relativity to explain self-acceleration of a closed cavity undergoing electromagnetic resonance. It is well known that (see for example any good text on Maxwell's equations, for example Jackson's) that
A) Maxwell's equations by themselves (without any additional statements) fully satisfy Lorentz invariance and Special Relativity. Hence there is no need whatsoever to add any Special Relativity statements to Maxwell's equations (doing so if consistent is superfluous and unnecessary, and if done inconsistently as done by Shawyer, it is incorrect). It does not make sense to try to make Maxwell's equations consistent with Special Relativity because they already are.
I don't agree with or like every aspect of Shawyer's conduct. However, I'll try being his apologist because I obviously, by my persistence here, demonstrate a more than casual interest. Although even if the EM Drive isn't what some of us expect, I have benefited greatly from the papers, links and discourse many such as yourself have provided.
Now then, I understood Shawyer's references to SR to apply to the fact that the speed of light is absolute. The space inside the frustrum with counter-propagating EM (standing wave) creates an absolute reference frame that will exert a force on the frustrum when it is accelerated +/-. In contrast to an acoustic cavityB) Maxwell's equations fully satisfy the equations of Conservation of Energy and Conservation of Momentum (without any additional statements). Therefore, it is not possible for a closed cavity to self-accelerate according to Maxwell's equations and Special Relativity. Since this is a well-known fact, people aware of these facts have rejected Shawyer's theory since his article in New Scientist in 2006, and a few have looked for other possible explanations of anomalous forces (for example Dr. White with his Quantum Vacuum theory, Dr. McCulloch based on the Unruh effect, and Dr. Woodward based on his Mach Effect theory, to name a few).
The courses from MIT that you have been listening to should make this (that Maxwell's equations fully satisfy Lorentz transformations and Special Relativity, and that Maxwell's equations fully satisfy Conservation of Momentum and Conservation of Energy) further clear.
Yes, and as I've claimed since around 11/15, the cavity isn't closed, its thermally open and is an-isotropically dissipating EM momentum as heat to create thrust. As I've said, I believe Shawyer has omitted this crucial fact.
Which of course justifies his critics objections. No apology from me for that.I also would appreciate knowing what you are referring to in here "Dr. Rodal would have done this trivially or off-hand months ago" as I need clarification of what are you referring to that we should have done trivially months ago?
Used Mathematica to plot a thrust-less standing wave in a dissipation-less frustrum, and a thrust-producing travelling wave in a frustrum with anisotropic dissipation.You may be interested in this derivation:
https://forum.nasaspaceflight.com/index.php?topic=39214.msg1526577#msg1526577
where I show a number of misconceptions regarding stresses, Poynting vector field and travelling waves for the EM Drive.
I'll have a look. Thanks.One of the misconceptions I address is something I discussed with you in the past: that one cannot readily obtain the radiation pressure using the Poynting vector (as usually done in introductory texts) in a resonant cavity. Also, that it is incorrect to discuss single travelling waves in a closed cavity (since a single propagating wave cannot satisfy the boundary conditions of the problem). And of course it is also incorrect to discuss plane electromagnetic waves inside a resonant cavity (they don't satisfy the B.C. either).
Ok, but could you expound on: "it is incorrect to discuss single travelling waves in a closed cavity (since a single propagating wave cannot satisfy the boundary conditions of the problem)."?
If you mean closed as in non-dissipative, OK. In my context of anisotropic dissipation and dispersion, I expect traveling waves.
I ought to go back to my studies and glacially-slow Octave one-dimensional FDTD.PS: When referring to MIT courses are you referring to Professor Gilbert Strang ? (spelling: instead of "Strange" ?). I took courses from Prof. Strang while I was at MIT (including courses on Finite Element Analysis theory, and Linear Algebra). Great teacher
Oops. I'll fix it. Indeed a great teacher. BTW, in one of the LinAl lectures, an executioner or death-like character in black with an ax or scythe saunters across the room. Do you know what was that about? Fraternity pledge perhaps? He had made some quip in an earlier lecture about life being short wrt to doing calculations that I vaguely remember. I don't know. Kinda bothers me
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#2796 by Rodal on 27 May, 2016 21:36
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On the contrary, the fact that the speed of light is an invariant is what prompted Einstein to create Special Relativity. Maxwell's equations (although created by Maxwell decades earlier) fully satisfy Lorentz invariance and Special Relativity. Shawyer goes out of his way to state that all he is using are Maxwell's equations and Special Relativity, both of which satisfy Lorentz transformations. Nowhere does Shawyer argue for an absolute frame of reference.
Now then, I understood Shawyer's references to SR to apply to the fact that the speed of light is absolute. The space inside the frustrum with counter-propagating EM (standing wave) creates an absolute reference frame that will exert a force on the frustrum when it is accelerated +/-. In contrast to an acoustic cavity
...
An absolute frame of reference is contradictory to Shawyer's explanation that he is using Special Relativity frame indifference.
When recently asked (in a series of excellent posts by GilbertDrive) what privileged frame of reference can he (Shawyer) possibly use to justify his introduction of a Kinetic Energy into an energy conservation, he was unable to answer the specific question (which is not surprising, as there is no road in space, and the EM Drive is supposed to have no exhaust that can be used as a reference).
Back in thread 1, hundreds of pages ago, it was decided to use a photon rocket as the standard of comparison, both in the thread (and also adopted in the EM Drive Experimental wiki when I put the table together and I was curating it). One of the reasons for this is that heat dissipation in space occurs as black body radiation (there cannot be thermal convection or conduction into space because it is a partial vacuum). Black body radiation is a form of photon radiation that is less efficient than a perfectly collimated photon rocket (due to unintentionally asymmetric waste heat radiation pressure). A good example of how inefficient such a form of propulsion is, is given by the Pioneer anomaly (the JPL study of black body radiation as being the cause of this very small anomaly). Hence one cannot justify the claims of EM Drive experimenters based on thermal dissipation, since EM Drive experimenters like Yang and Shawyer have claimed up to hundreds of thousands of times greater thrust/InputPower than the one of a perfectly collimated photon rocket.
...
Yes, and as I've claimed since around 11/15, the cavity isn't closed, its thermally open and is an-isotropically dissipating EM momentum as heat to create thrust. As I've said, I believe Shawyer has omitted this crucial fact.
...
Thus, it was explained in thread 1, that one cannot justify (based on thermal radiation) the EM Drive experimenter's extravagant claims for space propulsion....
This is explained in this post: https://forum.nasaspaceflight.com/index.php?topic=39214.msg1529920#msg1529920 including a number of gif's for visual understanding of the problem.
Ok, but could you expound on: "it is incorrect to discuss single travelling waves in a closed cavity (since a single propagating wave cannot satisfy the boundary conditions of the problem)."?
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In Physics, a possible solution to an equation is only valid if it satisfies the boundary conditions. Solutions that do not satisfy the boundary conditions are non-physical. -
#2797 by FattyLumpkin on 27 May, 2016 21:40
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Phil, can/would you disclose the amount of power required to produce the .1 Newton in 7 drives you will be delivering to XXXXXX company? And the mode? If not the specific mode can you disclose whether TE or TM? thanks, FL
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#2798 by Monomorphic on 27 May, 2016 22:35
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Got the spectrum analyser up and functioning. I plan on running the analyser during powered tests to not only confirm that RF is being generated, but that I am close to the resonant frequency (2.448Ghz). I mounted the spectrum analyser antenna on a tripod. And while I was replacing the magnetron, I snapped an image of the inside, with HDPE insert visible.
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#2799 by mwvp on 28 May, 2016 01:19
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On the contrary, the fact that the speed of light is an invariant is what prompted Einstein to create Special Relativity. Maxwell's equations (although created by Maxwell decades earlier) fully satisfy Lorentz invariance and Special Relativity. Shawyer goes out of his way to state that all he is using are Maxwell's equations and Special Relativity, both of which satisfy Lorentz transformations. Nowhere does Shawyer argue for an absolute frame of reference.
Now then, I understood Shawyer's references to SR to apply to the fact that the speed of light is absolute. The space inside the frustrum with counter-propagating EM (standing wave) creates an absolute reference frame that will exert a force on the frustrum when it is accelerated +/-. In contrast to an acoustic cavity
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An absolute frame of reference is contradictory to Shawyer's explanation that he is using Special Relativity frame indifference.
When recently asked (in a series of excellent posts by GilbertDrive) what privileged frame of reference can he (Shawyer) possibly use to justify his introduction of a Kinetic Energy into an energy conservation, he was unable to answer the specific question (which is not surprising, as there is no road in space, and the EM Drive is supposed to have no exhaust that can be used as a reference).
I've read there is a sort of privileged frame, and space, the vacuum itself is the road...
http://arxiv.org/pdf/0708.3519v4Quote"Consider that the vacuum medium is described by the vacuum states of
quantum fields and then its total momentum vanishes, it is reasonable for us to assume that
the vacuum medium as a whole is always resting with respect to all inertial observers. In
other words, the relative velocity between the vacuum medium and an arbitrary inertial
observer cannot be measured (i.e., it is an unobservable quantity), such that one can think it
always vanishes. On the other hand, consider that the velocity of light in vacuum is
invariant with respect to all inertial observers, and the eigenvalues of electron’s velocity
operator are equal to the velocity of light in vacuum, one can present the following
hypotheses: the velocity of light in vacuum ( 1 c = ) and the velocity of the vacuum medium
( ) are only two genuine velocities in our universe, they are invariant constants for all
inertial frames of reference; all other velocities are the apparent (or average) velocities of
massless fields moving in a zigzag manner. Such a zigzag motion, just as the
electromagnetic waves that are reflected back and forth by perfectly conducting walls as
they propagate along the length of a hollow waveguide, concerns two mutually orthogonal
0 u =
114D momentum components, i.e., a time-like 4D momentum (called the longitudinal
component) and a space-like 4D momentum (called the transverse component), respectively,
where the former corresponds to the usual 4D momentum of particles while the latter
contributes to the rest mass of particles."
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Yes, and as I've claimed since around 11/15, the cavity isn't closed, its thermally open and is an-isotropically dissipating EM momentum as heat to create thrust. As I've said, I believe Shawyer has omitted this crucial fact.
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Back in thread 1, hundreds of pages ago, it was decided to use a photon rocket as the standard of comparison, both in the thread (and also adopted in the EM Drive Experimental wiki when I put the table together and I was curating it). One of the reasons for this is that heat dissipation in space occurs as black body radiation (there cannot be thermal convection or conduction into space because it is a partial vacuum). It is trivial to show that black body radiation is a form of photon radiation that is less efficient than a perfectly collimated photon rocket (since photons participating in black body radiation are not high in the energy spectrum). A good example of how inefficient such a form of propulsion is, is given by the Pioneer anomaly (the JPL study of black body radiation as being the cause of this very small anomaly). Hence one cannot justify the claims of EM Drive experimenters based on thermal dissipation, since EM Drive experimenters like Yang and Shawyer have claimed up to hundreds of thousands of times greater thrust/InputPower than the one of a perfectly collimated photon rocket.
Thus, it was explained in thread 1, that one cannot justify (based on thermal radiation) the EM Drive experimenter's extravagant claims for space propulsion.
Correct. As I've explained a while back, its not the thermal radiation pressure of the dissipated EM microwave momentum at all. Lets just assume that is isotropic because the frustrum is in a metal sphere and be done with it.
Thrust is a result of unbalanced microwave EM momentum due to a preferentially dissipated lower sideband in an an-isotropically dispersive and dissipative cavity. A lower sideband created by Doppler spreading, resulting from nudging (accelerating) the frustrum into instability, imbalance.
The preferentially dissipated lower sideband that makes an otherwise standing wave into a traveling wave of unbalanced momentum which produces thrust.
And a preferentially Doppler down-shifted lower sideband at that, because the apex is tuned near cutoff and as the papers by Hawthorn I discussed before described, guide wavelengths are increased on the steep phase-slope in the high-dispersion apex by the Doppler effect.
It is much greater than a photon rocket, Q times, because radiation pressure for a reflector is twice that of an absorber. The frustrum tail end is preferentially absorbing Doppler down-shifted rocket-exhaust photons, which are expelled from the open-system as heat.
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This is explained in this post: https://forum.nasaspaceflight.com/index.php?topic=39214.msg1529920#msg1529920 including a number of gif's for visual understanding of the problem.
Ok, but could you expound on: "it is incorrect to discuss single travelling waves in a closed cavity (since a single propagating wave cannot satisfy the boundary conditions of the problem)."?
...
In Physics, a possible solution to an equation is only valid if it satisfies the boundary conditions. Solutions that do not satisfy the boundary conditions are non-physical.
Yes, very nice post. You, as do prof. Rumpf and most all others I've read consider either perfect transmission, or perfect reflection at a loss-less boundary. Lets do a simulation of an excited three-mode waveguide where the excitation matches the losses of a realistic metallic boundary. Lets just forget the real part of the metal dielectric constant, skin effect, evanescence and stuff and use just resistance. Then add some dispersion, and if we're really good, Doppler shift. And see if we get a standing wave, or traveling wave.
Perhaps I'm just naive in thinking it should be a relatively simple problem. FDTD isn't good for highly resonant structures, and frequency domain isn't much good for Doppler or time-domain changes.
