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#3360
by
Bob Woods
on 26 May, 2018 06:32
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Nice to see discussion and data flowing again.
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#3361
by
zen-in
on 26 May, 2018 17:26
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.......
A -55dB rtn loss from the S11 VNA scan represents a VSWR of 1.004:1 which is an impossible real world result.
Yet it is there.
One explication is it was caused by coupler self resonance, which ignores cavity eddy current losses.
BTW a -25dB S11 rtn loss is an excellent real world result, VSWR 1.2:1, when dealing with a high Q EmDrive.
Maybe ask Jamie what S11 rtn loss his cavity generates?
The VNA measured a S11 = -55dB so you can't say it is not a real world result. If instead there was a high quality dummy load S11 would be just as low, but over a wide range of frequencies. That would be another real world result. The cavity just happens to be resonant at 1866 MHz and just about all the RF power is dissipated inside the cavity with very little being reflected. I see nothing unusual about that. We are barking up the wrong tree.
There are inconsistencies with the geomagnetic field interaction and other magnetic theories that explain the thrust. Twisted power cables should cancel out any magnetic effects. Even parallel conductors will do that quite well. No attempt has been made yet to determine an optimum orientation of the experiment for the magnetic interaction. If the whole apparatus was rotated there should be nulls and peaks. This may be difficult to do but the fact remains there is not enough variability in the thrust to support a magnetic cause. Mumetal is a wonderful material but is over-rated as a magnetic shield. It's OK if you want to shield a Gaussmeter probe during calibration but for the purposes of isolating an EM-drive from the geomagnetic field it just won't work.
I still believe the "thrust" is a thermal effect. Reading the paper by Martin Tajmar et al I see a very faithful replication of the work done by White et al at Eagle Works Lab at JSC. The German team used a capacitor device for calibrating the force. The thrust waveform when it is energized has a fast risetime and the appearance of an under-damped step response (ringing, etc) for a first order driving force. That is what is expected. However when the power is applied the trust wave form has a rounded and slower rise-time. Immediately after the power is switched off the thrust drops with the shape of a decaying exponential waveform. Those are the characteristic shapes of a second order step response. I saw the same characteristics in the thrust waveforms that the Eagle Works tests produced. Both are due to thermal effects. Any EM-drive thrust due to RF being bottled up in a particular shaped cavity should have the characteristics of a first order step response, like the capacitive device.
Below is a section of one of the JSC EM-drive thrust waveform (Green) fitted to the temperature graph of an incandescent light bulb (Blue) after power on. The time scales and vertical scales are different. Both are exponential waveforms. The latest experiments from Germany are similar. I believe the EM-drive thrust is a thermal artifact.
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#3362
by
TomH
on 27 May, 2018 04:03
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5-22-18 Nat Geo Article re. EM drive testing @ Technische Universität Dresden, Germany
Simplistic summary: physicists theorize that the thrust that
was measured is a product of an interaction between Earth's magnetic field and power cables within the mechanism.
https://news.nationalgeographic.com/2018/05/nasa-emdrive-impossible-physics-independent-tests-magnetic-space-science/?utm_source=quora&utm_medium=referral(My own comment): If true, this would render moot most deep space use and limit productive research to travel within magnetic fields. Perhaps it might be effective at continual reboost for ISS. I suppose it might hold potential as a good way to power a space junk sweeper as it moves from target to target. Perhaps gravity assists at Jupiter and Saturn could be augmented with such a device. Or maybe interaction with the sun's magnetic field following a gravity assist from an inner planet.
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#3363
by
oyzw
on 27 May, 2018 07:42
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Tajmor教授的这个腔体不具备Q50000的能力，他的腔体最高理论值在TE011下，但是S11不可能达到-55。而且它的天线形态无法激发TE模态，TM模态不可能有如此高的Q值和如此低的回波损耗。他的射频工程构建存在严重错误。另外，腔体信号系统并非闭环系统，没有腔体信号提取端口，不能实现腔体谐振频率的实时追踪，杨涓教授的系统能够实现完美匹配和模态锁定。我的观点是否有道理呢？
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#3364
by
X_RaY
on 27 May, 2018 08:44
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#3365
by
oyzw
on 27 May, 2018 08:47
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我赞同您的观点，在射频工程技术上保罗教授和杨涓教授的设计更加专业
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#3366
by
X_RaY
on 27 May, 2018 08:58
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我赞同您的观点，在射频工程技术上保罗教授和杨涓教授的设计更加专业
I really hope the google translater works well...
I agree with your point of view. Prof. Paul and Prof. Yang Jie are more professional in radio frequency engineering.
I haven't made any statement about who has better skills in RF engineering. On the contrary, I would never make such statements without knowing the people and their abilities personally.
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#3367
by
Mark7777777
on 27 May, 2018 11:11
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#3368
by
TheTraveller
on 27 May, 2018 14:51
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Copper flower pots rule?
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#3369
by
Bob Woods
on 27 May, 2018 15:49
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Tajmor教授的这个腔体不具备Q50000的能力，他的腔体最高理论值在TE011下，但是S11不可能达到-55。而且它的天线形态无法激发TE模态，TM模态不可能有如此高的Q值和如此低的回波损耗。他的射频工程构建存在严重错误。另外，腔体信号系统并非闭环系统，没有腔体信号提取端口，不能实现腔体谐振频率的实时追踪，杨涓教授的系统能够实现完美匹配和模态锁定。我的观点是否有道理呢？
Google:
Professor Tajmor's cavity does not have the capability of Q50000. His cavity has the highest theoretical value under TE011, but S11 cannot reach -55. Moreover, its antenna shape cannot excite the TE mode, and the TM mode cannot have such a high Q value and such a low return loss. His RF engineering has serious errors. In addition, the cavity signal system is not a closed-loop system, and there is no cavity signal extraction port, so real-time tracking of cavity resonance frequency cannot be realized. Prof. Yang Xi's system can achieve perfect matching and modal locking. Does my opinion make sense?
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#3370
by
Monomorphic
on 27 May, 2018 16:02
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Professor Tajmor's cavity does not have the capability of Q50000. His cavity has the highest theoretical value under TE011, but S11 cannot reach -55. Moreover, its antenna shape cannot excite the TE mode, and the TM mode cannot have such a high Q value and such a low return loss. His RF engineering has serious errors. In addition, the cavity signal system is not a closed-loop system, and there is no cavity signal extraction port, so real-time tracking of cavity resonance frequency cannot be realized. Prof. Yang Xi's system can achieve perfect matching and modal locking. Does my opinion make sense?
It can't be TE011 as that mode is over 100Mhz away. The closest possibility is TE212, at 15Mhz away, but that is still a stretch. I noticed in the presentation, when asked by Rodal what mode they thought they were exciting, they said TM212. But TM212 is located at 2.45Ghz, which is 570 Mhz away! I will give them the benefit of the doubt that they misspoke and meant TE212, but it just goes to show that they haven't put a lot of thought into what mode, if any, they are exciting.
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#3371
by
PotomacNeuron
on 27 May, 2018 16:13
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Tajmor教授的这个腔体不具备Q50000的能力，他的腔体最高理论值在TE011下，但是S11不可能达到-55。而且它的天线形态无法激发TE模态，TM模态不可能有如此高的Q值和如此低的回波损耗。他的射频工程构建存在严重错误。另外，腔体信号系统并非闭环系统，没有腔体信号提取端口，不能实现腔体谐振频率的实时追踪，杨涓教授的系统能够实现完美匹配和模态锁定。我的观点是否有道理呢？
Google:
Professor Tajmor's cavity does not have the capability of Q50000. His cavity has the highest theoretical value under TE011, but S11 cannot reach -55. Moreover, its antenna shape cannot excite the TE mode, and the TM mode cannot have such a high Q value and such a low return loss. His RF engineering has serious errors. In addition, the cavity signal system is not a closed-loop system, and there is no cavity signal extraction port, so real-time tracking of cavity resonance frequency cannot be realized. Prof. Yang Xi's system can achieve perfect matching and modal locking. Does my opinion make sense?
I approve this message.
AI is now amazing. Such an excellent translation is not possible just a year ago. But it now surpasses my translation. I guess "translator" as a profession will be among early victims of AI.
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#3372
by
Monomorphic
on 27 May, 2018 16:31
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To put it into perspective how much being off by 15Mhz means, simulations showed TE013 at 2.4042Ghz for my 3D printed frustum. When assembled, TE013 was found right on the money at 2.40465Ghz. After aligning the small end parallel by using the screw adjusters to tighten down on the copper gasket, TE013 ended up at 2.40765Ghz. That is a difference of 3Mhz for ~2 mm of adjustments.
For TE212 to be 15Mhz off, Tajmar's frustum dimensions would need to be off by up to ~1cm.
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#3373
by
X_RaY
on 27 May, 2018 20:52
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5-22-18 Nat Geo Article re. EM drive testing @ Technische Universität Dresden, Germany
Simplistic summary: physicists theorize that the thrust that was measured is a product of an interaction between Earth's magnetic field and power cables within the mechanism.
https://news.nationalgeographic.com/2018/05/nasa-emdrive-impossible-physics-independent-tests-magnetic-space-science/?utm_source=quora&utm_medium=referral
(My own comment): If true, this would render moot most deep space use and limit productive research to travel within magnetic fields. Perhaps it might be effective at continual reboost for ISS. I suppose it might hold potential as a good way to power a space junk sweeper as it moves from target to target. Perhaps gravity assists at Jupiter and Saturn could be augmented with such a device. Or maybe interaction with the sun's magnetic field following a gravity assist from an inner planet.
If that's the case can a galaxy's magnetic field be used?
https://public.nrao.edu/news/galaxy-magnetic-field/
Not really. The field strength of a DC-magnetic field decreases with the third power with the distance from its
source**. The galactic magnetic field is rather weak. Therefore, the movement of even a strong neodymium magnet in free space is usually determined by its mass and impulse. The rather weak magnetic component acting on such a magnetized body is only of very low order.
**Yes of course i know due to Maxwell the magnetic field is free of sources. It is a rather verbal problem here, i hope it's clear what i meant.
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#3374
by
Monomorphic
on 27 May, 2018 21:34
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Not really. The field strength of a DC-magnetic field decreases with the third power with the distance from its source. The galactic magnetic field is rather weak. Therefore, the movement of even a strong neodymium magnet in free space is usually determined by its mass and impulse. The rather weak magnetic component acting on such a magnetized body is only of very low order.
Tajmar claims this is a compass-like effect. A compass only works because of the central bearing and the electromagnetic fields imparting angular momentum on to the pendulum as they align it with the geomagnetic field. This would not be thrust, but more of a false positive thrust signal.
It is worth pointing out that last we saw Shawyer was testing using a linear air bearing. As far as I know, he has never used a torsional pendulum. So the question becomes, is a linear air bearing vulnerable to false positive thrust using Lorentz forces?
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#3375
by
X_RaY
on 27 May, 2018 21:42
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Not really. The field strength of a DC-magnetic field decreases with the third power with the distance from its source. The galactic magnetic field is rather weak. Therefore, the movement of even a strong neodymium magnet in free space is usually determined by its mass and impulse. The rather weak magnetic component acting on such a magnetized body is only of very low order.
Tajmar claims this is a compass-like effect. A compass only works because of the central bearing and the electromagnetic fields imparting angular momentum on to pendulum as they align with the geomagnetic field. This would not be thrust, but more of a false positive thrust signal.
It is worth pointing out that last we saw Shawyer was testing using a linear air bearing. As far as I know, he has never used a torsional pendulum. So the question becomes, is a linear air bearing vulnerable to false positive thrust using Lorentz forces?
Why not? It depends on the sensitivity of the apparatus, the strength of the inducted magnetic force and the vectors of both the earth (surrounding) magnetic field and the one generated by his system.
Did we saw results from him with respect to different directions against the earth magnetic field using the linear bearing based drive? Can' remember this.
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#3376
by
Monomorphic
on 27 May, 2018 21:49
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Why not? It depends on the sensitivity of the apparatus, the strength of the inducted magnetic force and the vectors of both the earth magnetic (surrounding) magnetic field and the one generated by his system.
I agree. The Lorentz forces could push off the linear air bearing depending on how the bearing is oriented with the geomagnetic field. So perhaps what is needed is a low-friction table like an air hockey table. Build a self-contained engine and have it perform maneuvers on the table.
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#3377
by
Augmentor
on 28 May, 2018 01:27
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Monomorphic
An isolation transformer as in the original experiment by Woodward is needed.
Then making sure shielded cables, not just twisted pair, and in critical areas, more isolation. As necessary Triax cable but then we are talking real money.
Better PC board design/build efforts to reduce EMC and EMI. Notably guard traces and again, isolation transformers for power, and for signals, optical isolation.
IMHO Tajmar wanted to shakedown his test equipment but only did a shakedown of the community and world by publishing unclear results.
When writing one has to write so as NOT to be misunderstood. Apparently, this paper is a work of art more than science and english.
Martin will continue the hunt and gets bonus points for attempting both emDrive and MEGA testing.
There is still the matter of physics in the case of the emDrive...
Is the emDrive simply a variation on the theme of Mach effects?
David
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#3378
by
Bob Woods
on 28 May, 2018 03:39
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Why not? It depends on the sensitivity of the apparatus, the strength of the inducted magnetic force and the vectors of both the earth magnetic (surrounding) magnetic field and the one generated by his system.
I agree. The Lorentz forces could push off the linear air bearing depending on how the bearing is oriented with the geomagnetic field. So perhaps what is needed is a low-friction table like an air hockey table. Build a self-contained engine and have it perform maneuvers on the table.
I volunteer to pilot the apparatus. If it can move my big butt we're halfway to Proxima...
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#3379
by
flux_capacitor
on 28 May, 2018 16:40
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Monomorphic
An isolation transformer as in the original experiment by Woodward is needed.
About this isolation transformer: Tajmar did NOT use it. Woodward said in his mailing list a couple of days ago:
I should also mention that you may have heard that Martin Tajmar recently got results that disproved the reality of Mach effects. Be not fooled. Martin did not get any such results. Among other things, Martin did not employ an isolation/stepup transformer we sent him in the power circuit he used. I neglected to tell him that the transformer was an essential part of the circuit (as I did George and Nembo). This is addressed in the attached PPT file. Martin's presentation in Sevilla was not intended to give definitive results on anything. It was intended to inform the audience about the state of the art nature of his lab at TU Dresden. Martin has returned the demo device as agreed. But he will soon be getting a replacement, with transformer, to test on his balance.
https://forum.nasaspaceflight.com/index.php?topic=42978.msg1825112#msg1825112
