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#280 by meberbs on 28 Apr, 2020 18:34
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P is polarization of the dielectric insert. The total force= - volume integral of (P . grad ) E, where the value is averaged (constant component of a square sine).
The units of that formula are therefore pressure, not force, and the fact that it does not make sense due to changing in 3 D space remains. This is also not the formula for force on a reflecting surface.
In the standing wave, E is approximately zero at the reflecting surface while getting larger some distance away from the reflecting surface. (and P is proportional to E)
Whether the E field is 0 at a surface is not something you can generalize, it depends on the mode.
Anyway, if you actually do the calculations, the net force is zero. This is an inherent result based on the electrodynamic equations. -
#281 by RotoSequence on 29 Apr, 2020 19:05
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P is polarization of the dielectric insert. The total force= - volume integral of (P . grad ) E, where the value is averaged (constant component of a square sine).
The units of that formula are therefore pressure, not force, and the fact that it does not make sense due to changing in 3 D space remains. This is also not the formula for force on a reflecting surface.
In the standing wave, E is approximately zero at the reflecting surface while getting larger some distance away from the reflecting surface. (and P is proportional to E)
Whether the E field is 0 at a surface is not something you can generalize, it depends on the mode.
Anyway, if you actually do the calculations, the net force is zero. This is an inherent result based on the electrodynamic equations.
Does this remain true if the fine structure constant is, instead, a variable? -
#282 by meberbs on 29 Apr, 2020 19:47
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Does this remain true if the fine structure constant is, instead, a variable?
Which part?
The bad units and incorrect concepts that I was replying to are independent of that.
If you mean the last statement about electrodynamics guaranteeing net 0 force from radiation stuck inside a closed cavity, that likely would remain true even in a variable fundamental constants theory thanks to Noether's theorem.
To be 100% sure, you would first need to define the specifics of the theory which is extremely difficult and confusing for that type of theory. Even if there somehow was a violation, you would need significant variation on the scale of the device. We know from experiments that any variations in fundamental constants would only be on astronomical scales. Physical materials certainly do not cause this, we would see it in countless experiments, so there is effectively no hope of controlling fundamental constants directly. -
#283 by tidux on 30 Apr, 2020 01:40
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I saw a couple of posts mentioning "what if negative mass exists", but we've seen a couple of universities create negative mass in the lab now.
https://www.rochester.edu/newscenter/vamivakas-microcavity-negative-mass-generate-lasers-290202/Quote
Most objects react in predictable ways when force is applied to them—unless they have “negative mass particles.” And then they react exactly opposite from what you would expect.
Now University of Rochester researchers have succeeded in creating negative mass particles in an atomically thin semiconductor, by causing it to interact with confined light in an optical microcavity.
This alone is “interesting and exciting from a physics perspective,” says Nick Vamivakas, an associate professor of quantum optics and quantum physics at Rochester’s Institute of Optics. “But it also turns out the device we’ve created presents a way to generate laser light with an incrementally small amount of power.”
The device, described in Nature Physics, consists of two mirrors that create an optical microcavity, which confines light at different colors of the spectrum depending on how the mirrors are spaced.
Researchers in Vamivakas’ lab, including co-lead authors Sajal Dhara (now with the Indian Institute of Technology) and PhD student Chitraleema Chakraborty, embedded an atomically thin molybdenum diselenide semiconductor in the microcavity.
The semiconductor was placed in such a way that its interaction with the confined light resulted in small particles from the semiconductor—called excitons—combining with photons from the confined light to form polaritons.
“By causing an exciton to give up some of its identity to a photon to create a polariton, we end up with an object that has a negative mass associated with it,” Vamivakas explains. “That’s kind of a mind-bending thing to think about, because if you try to push or pull it, it will go in the opposite direction from what your intuition would tell you.”
https://phys.org/news/2017-04-physicists-negative-mass.htmlQuoteTo create negative mass, the researchers applied a second set of lasers that kicked the atoms back and forth and changed the way they spin. Now when the rubidium rushes out fast enough, if behaves as if it has negative mass."Once you push, it accelerates backwards," said Forbes, who acted as a theorist analyzing the system. "It looks like the rubidium hits an invisible wall."
Possibly related to opposite-direction thrust results in some experiments? -
#284 by meberbs on 30 Apr, 2020 03:42
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I saw a couple of posts mentioning "what if negative mass exists", but we've seen a couple of universities create negative mass in the lab now.
No, those are analogue systems, they are not true negative mass. I am pretty sure this fact was already explained. (Possibly in another thread, since your post mentions nothing relevant to the thread title.)Possibly related to opposite-direction thrust results in some experiments?
No. -
#285 by demofsky on 07 May, 2020 03:05
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Interesting article in its own right but also points to potential error sources in EM drive experiments. That is, escaping micro jets of air could be further energized increasing thrust from the jet.
https://www.greencarcongress.com/2020/05/20200506-plasma.html -
#286 by demofsky on 07 May, 2020 06:20
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Another article with better apparatus diagram:
https://arstechnica.com/science/2020/05/microwave-thruster-makes-for-clean-burning-jet/ -
#287 by Monomorphic on 08 May, 2020 13:09
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New Emdrive group? This is interesting because I am also working on a contactless RF connection. It greatly simplifies the experiment since the RF source and amplifier do not need to be mounted to the torsional pendulum.
https://www.researchgate.net/publication/340428103_HIGH_POWER_TRANSMISSION_USING_CONTACTLESS_MICROWAVE_TRANSITION_ON_AN_EMDRIVE_SETUP
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#288 by Mark7777777 on 08 May, 2020 20:36
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New Emdrive group? This is interesting because I am also working on a contactless RF connection. It greatly simplifies the experiment since the RF source and amplifier do not need to be mounted to the torsional pendulum.
https://www.researchgate.net/publication/340428103_HIGH_POWER_TRANSMISSION_USING_CONTACTLESS_MICROWAVE_TRANSITION_ON_AN_EMDRIVE_SETUP
It didn't read it in detail but I wonder if they went ahead and powered it up for a cavity, and took any thrust measurements? -
#289 by Monomorphic on 09 May, 2020 00:29
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It didn't read it in detail but I wonder if they went ahead and powered it up for a cavity, and took any thrust measurements?
They powered it up (the contactless RF connection), but it was not attached to a cavity. -
#290 by TheTraveller on 09 May, 2020 02:23
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It didn't read it in detail but I wonder if they went ahead and powered it up for a cavity, and took any thrust measurements?
They powered it up (the contactless RF connection), but it was not attached to a cavity.
Hi Jamie,
Of course all here are aware Roger build & used a contactless RF coupler in his latest Flight Thruster paper.
http://www.emdrive.com/flighthrusterreportissue2.pdf
Do you know if they are they intending to test a Flight Thruster replica? -
#291 by meberbs on 09 May, 2020 05:37
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It is trivial to search that document and see that no form of the word "contact" or any word containg that word appears anywhere in it. Of course at this point no one should be surprised by you making untruthful statements.It didn't read it in detail but I wonder if they went ahead and powered it up for a cavity, and took any thrust measurements?
They powered it up (the contactless RF connection), but it was not attached to a cavity.
Hi Jamie,
Of course all here are aware Roger build & used a contactless RF coupler in his latest Flight Thruster paper.
http://www.emdrive.com/flighthrusterreportissue2.pdf
Do you know if they are they intending to test a Flight Thruster replica? -
#292 by Monomorphic on 09 May, 2020 12:57
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It is trivial to search that document and see that no form of the word "contact" or any word containg that word appears anywhere in it. Of course at this point no one should be surprised by you making untruthful statements.
Shawyer did use a contactless RF coupler. He refers to it as Free Waveguide Coupling in that document and I have circled it in the image below (as I recall, Shawyer wrote about how much it leaked RF elsewhere). However, he did not use a contactless coupler for the returned RF to meter, nor all the wires for sensing temperature (mode) of the cavity.
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#293 by Monomorphic on 09 May, 2020 14:49
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Wired article about Dr. Sonny White's move from NASA to Limitless Space Institute. The article talks about the Emdrive, and mentions Dr. Tajmar and Professor Woodward.
https://www.wired.com/story/nasas-emdrive-leader-has-a-new-interstellar-project/
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#294 by TheTraveller on 09 May, 2020 14:59
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It is trivial to search that document and see that no form of the word "contact" or any word containg that word appears anywhere in it. Of course at this point no one should be surprised by you making untruthful statements.It didn't read it in detail but I wonder if they went ahead and powered it up for a cavity, and took any thrust measurements?
They powered it up (the contactless RF connection), but it was not attached to a cavity.
Hi Jamie,
Of course all here are aware Roger build & used a contactless RF coupler in his latest Flight Thruster paper.
http://www.emdrive.com/flighthrusterreportissue2.pdf
Do you know if they are they intending to test a Flight Thruster replica?
As attached.
Different dog, same leg action.
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#295 by TheTraveller on 09 May, 2020 15:06
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Some info on Dr White.
https://www.wired.com/story/nasas-emdrive-leader-has-a-new-interstellar-project/ -
#296 by meberbs on 09 May, 2020 16:10
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Shawyer did use a contactless RF coupler. He refers to it as Free Waveguide Coupling in that document and I have circled it in the image below (as I recall, Shawyer wrote about how much it leaked RF elsewhere). However, he did not use a contactless coupler for the returned RF to meter, nor all the wires for sensing temperature (mode) of the cavity.
In that case I stand corrected on that, though a search seems to confirm that the phrase "free waveguide coupling" is not a common term, so I hope I can be forgiven for missing this. This really is the least of the issues with that setup as has been covered before. -
#297 by Monomorphic on 10 May, 2020 03:00
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Do you know if they are they intending to test a Flight Thruster replica?
I have no other information other than what is available in the link. From what I have read there, it appears they do not have a resonant cavity, but hope their contactless coupler design can help those that do. -
#298 by flux_capacitor on 13 May, 2020 00:38
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Thanks for the link of the preprint site. The paper is published and is available in open access at http://www.jpier.org/PIERL/pier.php?paper=19110504
One can read this sentence at the end:
"All the authors would like to thank both CNES (French National Centre for Space Studies) for its financial support for carrying out this research and AID (French Innovation and Defense Agency) for funding Hugo Peyre’s PhD."
As a doctor thesis in underway, I think more testing will be done and this paper may only be the beginning for that team. I wonder if they are collaborating with or have asked questions to Roger Shawyer.
They did not but they're about to do it (EDIT: they actually did some preliminary measurements, see my next post). In the References section at the end of the paper you linked to, there is a second paper from the same team on the same subject published in another journal of same mother journal Progress in Electromagnetic Research Letters (PIER Letters) also in February 2020:It didn't read it in detail but I wonder if they went ahead and powered it up for a cavity, and took any thrust measurements?
They powered it up (the contactless RF connection), but it was not attached to a cavity.
Sokoloff, J., O. Pascal, O. Pigaglio, N. Raveu, and H. Peyre, "Proposal of a handy setup for discriminating parasitic effects for the measurement of impulsive thrust from a microwave cavity", Progress In Electromagnetics Research C, Vol. 98, 269–281, 2020.
The whole setup is already characterized and the test campaign is about to begin. As the paper was published in January or February 2020 and was logically submitted before, it is very possible that such test campaign is already going on.
In this second papar there is the same sentence at the end in the Acknowledgment section.
Lead researcher appears to be Jérôme Sokoloff at the LAPLACE laboratory (LAboratoire PLAsma & Conversion d'Energie) of the University of Toulouse, France. Toulouse is also the home city of CNES (the French Space Agency), AIRBUS, ARIANEspace, One of US Hyperloop test bed, etc.
It's occurring in my home country. Will try to ask some appropriate contacts to try to learn a bit more about this, and will report here if public info is available. -
#299 by flux_capacitor on 13 May, 2020 11:25
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Quick summary of the French EmDrive (pre)testing in the second paper available at http://www.jpier.org/PIERC/pierc98/20.19090507.pdf:
They built their own EmDrive prototype:
Figure 3. Resonant microwave cavity and a HFSS simulation of its fundamental mode.
Note the cylindrical parts of constant cross-section at small end above the truncated part, and a screw to adjust the axial position of the small plate. The build quality seems quite good IMHO. I think it is CNC-machined in aluminum and polished.
Small end ⌀: 40 mm
Big end ⌀: 119.8 mm
Inner axial height: 63.85 mm
Weight of a cavity: ~ 1kg
Made to be resonant at 2.444 GHz (measured −20dB at f₀ = 2.4408GHz)
Measured Q-factor = 3550 (while sims expected around 6000)
The EM mode is TXxx (?)
In fact they made two identical cavities. They apparently took the small discrepancies into account:
Figure 4. Return loss of the two manufactured cavities.
They did not use a torsional pendulum but a commercially-available precision balance (XPE15002L from METTLER TOLEDO, able to weight masses from 2g to 15.1kg with an accuracy about 0.1mN) placed on a marble table encased in plexiglass to limit air currents displaced in the room. The setup can be powered by a microwave solid-state generator capable of 2.43–2.47GHz frequency range, and an output power up to 200 W. It looks like this:
Figure 5. Experimental setup picture.
They put the two units together upside-down in opposite directions, like this:
Figure 1. Diagram of the original configuration named "Shaker". (a) Downward thrust; (b) Upward thrust.
Detail on the pair of resonant cavities mounted over the balance:
Figure 6. Picture of the "shaker" setup placed on the balance.
There are graphs and protocol of the setup characterization, I let you dig in the paper for that.
I'll just copy-paste last section to explain where they are in this paper and what they want to test exactly:QuoteDISCUSSION
Regarding the measurement and analysis protocols, we opted, as White et al. did [1], for temporal measurements of the setup response combined with the strategy of reversing the cavity under test. Indeed, we have designed and used a so-called “shaker” configuration that preserves the same parasitic effects for both orientations of the cavity. It does not require any intervention on and around the cavities. This original configuration implies that the article under test consists of two cavities oriented in the opposite directions, which can be alternately fed via a switch. The whole constitutes a unique set placed on the balance. Processing in this way, the thermal effect of the cable can be subtracted by making the difference in the responses associated with the two orientations of the cavity. This difference could potentially show twice the level of the force. However, the performance of this method is limited due to the thermal effect of the cable which is not perfectly reproducible when subjected to power pulses (typically 200W). Therefore, a post-processing based on pulse averaging and the estimation of their standard deviation was performed in order to establish the uncertainty of the setup in this configuration.
Measurements made with our cavities did not reveal the presence of an EMDrive type force with an intensity greater than 0.5 mN, the estimated accuracy of the setup in this configuration. However, these apparently negative results must be balanced. Indeed, the credible force levels extracted from the literature, and projected with the power available on our setup, are around 0.2 mN, which is below our current accuracy. Moreover, the measuring setup we have realized is an affordable, handy, and versatile base for the detection of an EMDrive type force. It already allows the rapid study of different cavities with an accuracy below the milliNewton.
However I feel the last sentences are not really encouraging since I understood the predicted thrust, when mundane effects are subtracted, is about or below their current resolution accuracy. Do they plan to have a better balance or increase the power?