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#800
by
SleeperService
on 18 Feb, 2015 16:03
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I think we're getting on a tangent. But here's your answer.
http://www.radartutorial.eu/03.linetheory/tl11.en.html
Not really, with respect.
You can't have a small probe like you link and expect it to optimise on a freq. sweep for resonance. The resonance shapes are much too complex (Like Star Drive presented.) Do you see what I mean, or am I being dumb?
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#801
by
Rodal
on 18 Feb, 2015 16:04
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A feedback circuit would be required in order to keep the VCO on the resonant frequency. If such a feedback is possible then a simple MCU could be programmed to do that using an ADC as output, it would not be a PLL anyway but more similar to an FLL.
Where does the feedback signal come from?
This is the problem 
I do understand controls and realtime systems but microwaves and resonant cavities are not my field. How do you know it is resonating?
In theory the thrust could be your feedback, you tune the VCO in order to maximize that.
This is a really a good point for a number of reasons. Not least of which is the fact that NASA reports that thrust is
not proportional to resonance Q. Some of the experiments show greater thrust at a lower Q.
If these experimental results are
statistically significant(?) then using thrust as feedback, rather than insisting on Q resonance, is the way to go:
Mode Frequency (MHz) Quality Factor, Q Input Power (W) Mean Thrust (μN) Pressure
TE012 1880.4 22000 2.6 55.4 Ambient
TM212 1932.6 7320 16.9 91.2 Ambient
TM212 1936.7 18100 16.7 50.1 Ambient
TM212 1937.115 6726 50 66 Vacuum
notice that
TM212 1932.6 7320 16.9 91.2
produces practically twice the thrust of
TM212 1936.7 18100 16.7 50.1
which has more than twice the Q at practically the same Input Power and frequency
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#802
by
SleeperService
on 18 Feb, 2015 16:11
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Higher thrust at lower Q seems to hint at heating/other reasons unfortunately...
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#803
by
Rodal
on 18 Feb, 2015 16:13
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Higher thrust at lower Q seems to hint at heating/other reasons unfortunately...
I agree, but still, using thrust as feedback is superior to relying on resonance at this stage of knowledge.
If thrust is proportional to Q, as expected by a number of theoretical formulas (Shawyer, McCulloch and NotSoSureOfIt) it does not make a difference whether to use thrust or resonance as feedback, while if thrust is not proportional to Q, then feedback based on thrust is superior, because of course, what one is after is space propulsion by the EM Drive and not just an EM Drive resonating in space.
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#804
by
SleeperService
on 18 Feb, 2015 16:20
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Dr. Rodal,
What do you think about the false maxima that we could get in the thrust of the EM Drive?
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#805
by
Rodal
on 18 Feb, 2015 16:26
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Dr. Rodal,
What do you think about the false maxima that we could get in the thrust of the EM Drive?
Need you to elaborate further: false because...it is a local maximum and not the true maxima...false because of error...false because of lag...
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#806
by
SleeperService
on 18 Feb, 2015 16:29
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Dr. Rodal,
What do you think about the false maxima that we could get in the thrust of the EM Drive?
Need you to elaborate further: false because...it is a local maximum and not the true maxima...false because of error...false because of lag...
Indeed! We need to get the computing resources together to help us...
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#807
by
Mulletron
on 18 Feb, 2015 16:30
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Thrust is not only proportionate to Q. Evidence suggests that thrust depends on the complex interplay of Q, mode shape and field density, and dielectric location wrt mode topology.
For unloaded magnetron fed cavities, thrust depends on Q. This is because it is resonant at many modes at once.
If Eagleworks wants to improve the performance of their emdrive, get more VCXOs and run them into a combiner, then to the amp.
Or brute force it with a magnetron or noise source.
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#808
by
SleeperService
on 18 Feb, 2015 16:38
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What hope do we have then?!?!
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#809
by
SleeperService
on 18 Feb, 2015 16:43
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Another question which I had...
I can see into my microwave thru a mesh that is < 1/2 the uWave frq.
Why are we considering RF energy leaking out with tiny gaps?
Does this happen?
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#810
by
Giovanni DS
on 18 Feb, 2015 16:46
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About false maxima, it could work like a spectrum analyzer: perform a wide frequency sweep on an initial window, find the maximum (more than one peak could be present) and restrict the window around that, then repeat. When the signal is diminishing then the window could be enlarged and a new sweep performed.
I am sure a good algorithm could be found for this problem.
Thrush measurement problem is that the loop would be probably slow, the sweeps could take time.
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#811
by
Flyby
on 18 Feb, 2015 17:23
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Not really my expertise field, but can somebody tell me if the volumetric resonance patterns are static or dynamic?
iow, does the combination of internal frustrum shape and wavelength(s) cause the resonance pattern to shift left or right (Is that the "reverse" ppl were talking about?), or does it stay immobile (static) once the interference patterns are established ??
I understand that the shape and aspect of the resonance pattern is very very sensitive and can easily change aspect (and direction?) caused by the slightest change (either wavelength or geometry of the frustrum).
As some of you talked about dielectric materials possibly improving performance, I suppose a force could be generated from the high intensity microwave resonance spots colliding with the frustrum? Am I correct on this assumption?
If that is the case, and looking at it from a distance, shouldn't we speak of a "magnetic pulse engine" as the high-intesity magnetic fields slam into frustrum wall, pushing it forward ?
or.. am i talking completely BS here?
Just trying to understand while feeling very much out of comfort zone...
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#812
by
SleeperService
on 18 Feb, 2015 17:35
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Not really my expertise field, but can somebody tell me if the volumetric resonance patterns are static or dynamic?
iow, does the combination of internal frustrum shape and wavelength(s) cause the resonance pattern to shift left or right (Is that the "reverse" ppl were talking about?), or does it stay immobile (static) once the interference patterns are established ??
I understand that the shape and aspect of the resonance pattern is very very sensitive and can easily change aspect (and direction?) caused by the slightest change (either wavelength or geometry of the frustrum).
As some of you talked about dielectric materials possibly improving performance, I suppose a force could be generated from the high intensity microwave resonance spots colliding with the frustrum? Am I correct on this assumption?
If that is the case, and looking at it from a distance, shouldn't we speak of a "magnetic pulse engine" as the high-intesity magnetic fields slam into frustrum wall, pushing it forward ?
or.. am i talking completely BS here?
Just trying to understand while feeling very much out of comfort zone...
As far as I know the resonant freq. is very sensitive to the cavity properties.
Thermal buckling would change this a lot...
Basically you are correct...
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#813
by
Mulletron
on 18 Feb, 2015 17:57
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Strong H field at dielectric disc. Just like theory suggests.
we have found that the chiral molecule acquires a kinetic
momentum during the switching of the external magnetic field as a result of its
interaction with the vacuum field. On the other hand we have shown that, as a
result of the conservation of the total momentum K, there exists a transfer of linear
momentum from the vacuum field to the molecule.
http://arxiv.org/pdf/1404.5990v1.pdfhttp://arxiv.org/abs/1304.6767http://ptp.oxfordjournals.org/content/119/3/351.full.pdfBut it isn't JUST chiral molecules, as I've shown experimental evidence of the observation of magneto-electric non-reciprocity in molecular nitrogen gas.
https://hal.archives-ouvertes.fr/hal-00551421v1/documenthttp://arxiv.org/abs/1101.0712 Which means that air confined to a resonant cavity falls into their magneto-electric metric too. Any condition which creates an anisotropic electromagnetic vacuum environment works.
Which explains why unloaded cavities tested by the Chinese and Shawyer work too.
This implies that a magneto-electric directionally anisotropic electromagnetic environment also absolutely implies an anisotropic vacuum environment, as the authors suggest is true and aim to measure.
Moreover, the same effect is expected in quantum vacuum.
Only I found evidence last night that the vacuum anisotropy experiment has already been done in the 80s.
http://heart-c704.uibk.ac.at/LV/Quantenoptik/Kapitel_8/Jhe_etal_PRL_58_666_%281987%29.pdfThis Emdrive operates exactly as I have suggested and existing theory supports. I've beat this dead horse enough.
Edit: Put Shen in there.
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#814
by
tchernik
on 18 Feb, 2015 18:59
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Strong H field at dielectric disc. Just like theory suggests.
we have found that the chiral molecule acquires a kinetic
momentum during the switching of the external magnetic field as a result of its
interaction with the vacuum field. On the other hand we have shown that, as a
result of the conservation of the total momentum K, there exists a transfer of linear
momentum from the vacuum field to the molecule.
http://arxiv.org/pdf/1404.5990v1.pdf
http://arxiv.org/abs/1304.6767
But it isn't JUST chiral molecules, as I've shown experimental evidence of the observation of magneto-electric non-reciprocity in molecular nitrogen gas.
https://hal.archives-ouvertes.fr/hal-00551421v1/document
http://arxiv.org/abs/1101.0712
Which means that air confined to a resonant cavity falls into their magneto-electric metric too. Any condition which creates a chiral electromagnetic vacuum environment works.
Which explains why unloaded cavities tested by the Chinese and Shawyer work too.
This implies that a magneto-electric directionally anisotropic electromagnetic environment also absolutely implies an anisotropic vacuum environment, as the authors suggest is true and aim to measure.
Moreover, the same effect is expected in quantum vacuum.
Only I found evidence last night that the vacuum anisotropy experiment has already been done in the 80s.
http://heart-c704.uibk.ac.at/LV/Quantenoptik/Kapitel_8/Jhe_etal_PRL_58_666_%281987%29.pdf
This Emdrive operates exactly as I have suggested and existing theory supports. I've beat this dead horse enough.
Wow. Those are quite remarkable papers. It seems like a very likely cause for the thrust, with previous published results availing it.
I wonder why the research wasn't pursued to its logical conclusion (a thruster). Maybe the researchers didn't believe they could get usable forces?
Also, does this mean the Emdrive actually works better with air inside the cavity? it may be so, just not for the reason everyone is afraid of. The QV may actually impinge momentum onto the air molecules contained by the thruster.
Edit:
I just noticed the research is fairly new (except the link from the 80s). So that could explain why the experiments haven't resulted in setups with forces perceptible in the macroscopic scale.
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#815
by
Flyby
on 18 Feb, 2015 19:09
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huh... you really don't make it easy for me , don't you?
I either have to wrestle through an english translation (bad bad idea) or i need to look up and understand scientific explanation of the english scientific concepts/words you guys are using...
As my last science courses date of 30 years ago...It's not that obvious to brush up my - old and outdated - knowledge of science in a foreign language, but hey, never stepped aside for a bit of a challenge....
Thanks to this very topic, I'm offering myself a crash course in electromagnetic (micro)waves, simply by trying to look up the words and terminology and attempting to understand what you guys are talking about...
glad there is Wikipedia to assist me in these dark moments when I stare at these topics like a rabbit in a lightbox... blink.. blink.. fascinating... blink ..blink...
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#816
by
Rodal
on 18 Feb, 2015 19:35
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Folks:
While you all talk about various ways to accomplish the E&M simulations of these frustum cavities, I thought you might like to take a look at the COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity driven with a ~16mm OD loop antenna located 15% up the side wall of the frustum from the large OD end of the cavity.
BTW, the EMPower amplifiers were delivered to the Lab yesterday and I'll be calibrating the power metering for one that was installed yesterday on the torque pendulum.
Best, Paul M,
Paul, I just calculated the natural frequency for mode TE012 without the dielectric,
from the exact solution to the truncated cone, based on the geometry you provided us recently:
Large OD : 11.00 " (0.2794m)
Small OD: 6.25" (0.1588 m)
Length : 9.00 " (0.2286m)
and I obtained:
EXACT SOLUTION TE012: 2.20244 GHzF.Davies/NASA/COMSOL TE012: 2.1794 GHz
Difference from COMSOL F.E.A.: (2.1794/2.20244 - 1)*100 = -1.05%
I am extremely impressed with the accuracy obtained by Frank Davies NASA/JSC/EP5 using COMSOL (
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=796287 ): only 1% difference from the exact solution for this mode TE012.
The fact that the COMSOL solution gives a little lower frequency makes perfect sense because the Finite Element solution converges from below (a finer mesh would result in a higher frequency, to reach the exact solution takes in the limit an infinite number of finite elements).
For TE011:EXACT SOLUTION TE011: 1.78972 GHzF.Davies/NASA/COMSOL TE011: 1.77048 GHz
Difference from COMSOL F.E.A.: (1.77048/1.78972 - 1)*100 = -1.08%
_____
Note:
1) found some errors on Greg Egan's formulas affecting higher modes but his posted example results are OK, and his methodology is impecable
2) I am working on an exact solution for the truncated cone
with the dielectric
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#817
by
Notsosureofit
on 18 Feb, 2015 19:50
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@ RODAL
Can you generate a dispersion relation from the exact solution ?
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#818
by
Rodal
on 18 Feb, 2015 19:53
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@ RODAL
Can you generate a dispersion relation from the exact solution ?
(Almost) anything is possible
if I get the time This work done whenever I take a break from $$$ paying work
It continues to snow over here
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#819
by
Rodal
on 18 Feb, 2015 20:02
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This clapping dedicated to Paul March, Dr. White and the NASA Eagleworks team for being the first EM Drive International team to realize that it was important to calculate the mode shapes of the EM Drive, and to Frank Davies NASA/JSC/EP5 for his excellent Finite Element Analysis using COMSOL, only 1% away from the exact solution for modes TE011 and TE012:
I do understand controls and realtime systems but microwaves and resonant cavities are not my field. How do you know it is resonating?