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#280 by rfmwguy on 17 Dec, 2015 15:15
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Good ideas, but a spectrum spike of RF would show when the power was locked into a stable output...think this would do it. The Schlieren vid could have a small window on the same screen showing the spectrum...I would do a simple screen record of both videos simultaneously...Doc,
Yes, a video would both have a timer and contain audio to denote mag on (xformer hum).
Also, I could imbed a spectrum analyzer display in the corner to show freq locking, which would probably be a better indication of start.
Plume temp would be hard to measure with my IR thermometer...can get a case temp or sync a thermal vid.
Accurately synchronizing the Schlieren movie to the turning on and off the magnetron is the big issue...
Maybe readers can point out what would be the most accurate synchronization between a movie and actual timing of the Magnetron turning ON and OFF...
It seems to me that the best way would be to have a signal showing the magnetron going ON and OFF in the movie itself (this would eliminate any errors due to the movie marching in time at a different, or non-monotonic rate than an external accurate clock).
Tap a current sensor off the magnetron's electronic feed circuit and either turn a light on or just put an ammeter in the video. This would show when there's actually power going to the magnetron. -
#281 by Rodal on 17 Dec, 2015 15:35
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Doc,
Yes, a video would both have a timer and contain audio to denote mag on (xformer hum).
Also, I could imbed a spectrum analyzer display in the corner to show freq locking, which would probably be a better indication of start.
Plume temp would be hard to measure with my IR thermometer...can get a case temp or sync a thermal vid.
Accurately synchronizing the Schlieren movie to the turning on and off the magnetron is the big issue...
Maybe readers can point out what would be the most accurate synchronization between a movie and actual timing of the Magnetron turning ON and OFF...
It seems to me that the best way would be to have a signal showing the magnetron going ON and OFF in the movie itself (this would eliminate any errors due to the movie marching in time at a different, or non-monotonic rate than an external accurate clock).
Tap a current sensor off the magnetron's electronic feed circuit and either turn a light on or just put an ammeter in the video. This would show when there's actually power going to the magnetron.
Is the proposal thatQuoteThe Schlieren vid could have a small window on the same screen showing the spectrum
just as concurrently synchronized as showing the ammeter in one and the same same Schlieren video? or does windowing of separate videos (one video for the spectrum and another video for the Shlieren optical view) introduce synchronization issues between the windowed videos?
(Separate window processes on a computer do not necessarily run concurrently, so is just a practical issue of whether the timing differences (and their accumulated effect) between the windows are or are not negligible for the experimental purposes) -
#282 by rfmwguy on 17 Dec, 2015 15:40
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Current would be OK, but the mag does not necessarily "lock" until it comes up to temp and stabilizes. This is why I proposed a spec an spike to show its lock mode rather than a current sampling. Anytime the RF peaks, it would show lock and it would be synchronized with the Schlieren video...simply overlaid on top and a screen recorder would make the combined video.
Sooo, Schlieren video runs on laptop, overlaid with a small spec analyzer display (also running in real time). Screen record video captures both in real time...make sense? -
#283 by rfmwguy on 17 Dec, 2015 15:52
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OK, Doc, CEJ posted this on T5 and I forgot about it:
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1441327;topicseen#msg1441327
http://people.csail.mit.edu/tfxue/proj/fluidflow/
You're an MIT guy...give me your thoughts about their software! -
#284 by Rodal on 17 Dec, 2015 16:02
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OK, Doc, CEJ posted this on T5 and I forgot about it:
The author was in the Electrical Engineering Department Course Vi, and just concludes
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1441327;topicseen#msg1441327
http://people.csail.mit.edu/tfxue/proj/fluidflow/
You're an MIT guy...give me your thoughts about their software!Quoteprovide promising evidence that refractive fluids can be analyzed in natural settings, which can make fluid flow measurement cheaper and more accessible
So, I trust that it is indeed "promising" which is what the author concludes.
The next step would be to verify whether these new algorithms and method have been embraced by the Fluid Mechanics community (in the Aeronautics and Astronautics Course XVI and Mechanical Engineering Course II departments at MIT) or by the academic fluid mechanics community in general that have been using other methods. Everything in science and engineering is a question of independent duplication of experiments and peer review to verify how robust and precise are such cheaper techniques.
Of course Schleiren optical methods have been embraced by the Fluid Mechanics community for a century. -
#285 by rfmwguy on 17 Dec, 2015 16:11
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So Doc, can I count on you to take the next step?OK, Doc, CEJ posted this on T5 and I forgot about it:
The author was in the Electrical Engineering Department Course Vi, and just concludes
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1441327;topicseen#msg1441327
http://people.csail.mit.edu/tfxue/proj/fluidflow/
You're an MIT guy...give me your thoughts about their software!Quoteprovide promising evidence that refractive fluids can be analyzed in natural settings, which can make fluid flow measurement cheaper and more accessible
So, I trust that it is indeed "promising" which is what the author concludes.
The next step would be to verify whether these new algorithms and method have been embraced by the Fluid Mechanics community (in the Aeronautics and Astronautics Course XVI and Mechanical Engineering Course II departments at MIT) or by the academic fluid mechanics community in general. Everything in science and engineering is a question of independent duplication of experiments and peer review to verify how robust and precise are such cheaper techniques.
Of course Schleiren optical methods have been embraced by the Fluid Mechanics community for a century.
I'll volunteer to get the gear and do the test IF you think its worthwhile.
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#286 by jmossman on 17 Dec, 2015 16:20
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Current would be OK, but the mag does not necessarily "lock" until it comes up to temp and stabilizes. This is why I proposed a spec an spike to show its lock mode rather than a current sampling. Anytime the RF peaks, it would show lock and it would be synchronized with the Schlieren video...simply overlaid on top and a screen recorder would make the combined video.
Sooo, Schlieren video runs on laptop, overlaid with a small spec analyzer display (also running in real time). Screen record video captures both in real time...make sense?
RF peaks would help determine if a "lock" correlates with any measured anomalies. However, I think having a "Magnetron On/Off" visual indicator would also be useful (using just "hum" from audio creates another unknown variable; if visual indicator and "hum" have a constant time offset, that would also be useful to know).
Being able to compare, whether a "lock" or "Magnetron On/Off" provides the stronger correlation with any measured anomalies, could be a hugely important data point.
EDIT: typo correction -
#287 by Rodal on 17 Dec, 2015 16:23
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So Doc, can I count on you to take the next step?OK, Doc, CEJ posted this on T5 and I forgot about it:
The author was in the Electrical Engineering Department Course Vi, and just concludes
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1441327;topicseen#msg1441327
http://people.csail.mit.edu/tfxue/proj/fluidflow/
You're an MIT guy...give me your thoughts about their software!Quoteprovide promising evidence that refractive fluids can be analyzed in natural settings, which can make fluid flow measurement cheaper and more accessible
So, I trust that it is indeed "promising" which is what the author concludes.
The next step would be to verify whether these new algorithms and method have been embraced by the Fluid Mechanics community (in the Aeronautics and Astronautics Course XVI and Mechanical Engineering Course II departments at MIT) or by the academic fluid mechanics community in general. Everything in science and engineering is a question of independent duplication of experiments and peer review to verify how robust and precise are such cheaper techniques.
Of course Schleiren optical methods have been embraced by the Fluid Mechanics community for a century. I'll volunteer to get the gear and do the test IF you think its worthwhile.
The solution involves a mathematical inversion.
The mathematical problem of inverting random refracted dynamic distortions is difficult, particularly when the objects in the field of view are moving as it is the case in fluid dynamics.
Whenever you invert a mathematical expression you encounter issues. Elementary examples are inversion of the square function (resulting in the square root which has two possible values for a given value of input). In this case the algorithms imply numerical inversion of matrices that may be ill-conditioned under a-priori unknown conditions
Can't give you a good answer as far as how robust this technique is, and can't volunteer the time to explore it. sorry. The author (who spent a considerable amount of time on it) writes that the technique is promising.
On the other hand if you go with Schlerein photography you would be using a technique that is known to be robust and does not have mathematical inversion issues.
It may be easier to use an infrared thermometer to measure the temperature of a turkey, but when cooking a Thanksgiving or Christmas dinner I rather use the old well-known technique of inserting a thermometer inside the turkey as it eliminates the problem of thermal conduction (the temperature inside the turkey is different from the surface temperature) and it eliminates the calibration of unknwon emissivity of the turkey exterior surface. -
#288 by lmbfan on 17 Dec, 2015 17:13
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Just FYI, there exists OpenFOAM, a computational fluid dynamics (CFD) suite, which appears to be fairly mature. I don't know enough about CFD to comment on whether or not OpenFOAM has the requisite solvers for modeling whichever thermal effects are present in/around a frustum.
http://openfoam.org/
https://en.wikipedia.org/wiki/OpenFOAM
Existing solvers:
http://openfoam.org/features/standard-solvers.php
I would be willing to create IGES, STEP, or STL (or a limited number of other, less common formats) files of frustums and/or experimental setups. I the software I use has the capability to "develop" solids for finite element analysis (FEA) and export it as ANSYS PREP7, and so therefore I may be able to help with that (if that is even necessary for CFD). Caveat - I have never "developed" a model for FEA analysis. -
#289 by rq3 on 17 Dec, 2015 17:34
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Good ideas, but a spectrum spike of RF would show when the power was locked into a stable output...think this would do it. The Schlieren vid could have a small window on the same screen showing the spectrum...I would do a simple screen record of both videos simultaneously...
[/quote]
Shlieren systems are pretty straightforward if you decide to go ahead with this. Having built a few, a
couple of suggestions:
1) You'll need a reasonably collimated light source, like an old slide projector
2) Rather than use the ubiquitous knife edges, try a pair of ronchi rulings. MUCH easier to align, larger test area, and immensely larger contrast ratio.
3) For a large test area, Fresnel lenses are cheap and useable. The image will suffer, but it will be viewable.
Also a few thoughts on thermal issues.
1) IF the frustum is reasonable rigid, hermetically sealed, and auto-tuned to the drive RF, it won't show any balloon effect from heating. The interior gas will pressurize as it gets hotter, but the gas MASS won't change. Pulling a vacuum on a waveguide (frustum) as others have suggested is begging for interior arcing.
2) If the frustum were placed inside a cylindrical "chimney" that travels with it, one would think that the heat plume would be identical with the "big end up", or the "big end down". For the same number of dissipated watts, the air flow should be identical regardless of frustum vertical orientation. The delta would be...thrust? -
#290 by OnlyMe on 17 Dec, 2015 17:44
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....
Shlieren systems are pretty straightforward if you decide to go ahead with this. Having built a few, a
couple of suggestions:
1) You'll need a reasonably collimated light source, like an old slide projector
2) Rather than use the ubiquitous knife edges, try a pair of ronchi rulings. MUCH easier to align, larger test area, and immensely larger contrast ratio.
3) For a large test area, Fresnel lenses are cheap and useable. The image will suffer, but it will be viewable.
Also a few thoughts on thermal issues.
1) IF the frustum is reasonable rigid, hermetically sealed, and auto-tuned to the drive RF, it won't show any balloon effect from heating. The interior gas will pressurize as it gets hotter, but the gas MASS won't change. Pulling a vacuum on a waveguide (frustum) as others have suggested is begging for interior arcing.
2) If the frustum were placed inside a cylindrical "chimney" that travels with it, one would think that the heat plume would be identical with the "big end up", or the "big end down". For the same number of dissipated watts, the air flow should be identical regardless of frustum vertical orientation. The delta would be...thrust?
Is the arcing mentioned at #1 above dependent on vacuum quality? Ultimately the thing would need to function in vacuum. -
#291 by robus on 17 Dec, 2015 17:48
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A small plea from the peanut gallery.
With all due respect, is it possible to limit discussion of tests and results to those that are actively participating in the forum? Given how vaguely the tests have been described by Shawyer and Yang it seems fruitless to continue to debate their results?
EW, Shell, rfmwguy, et al are all actively engaging (as they can) and thus answers about approaches, artifacts etc are readily available. But I, for one, don't see the point of reading the tea leaves of those other tests? Extraordinary results require extraordinary evidence and that is definitely in short supply from them. Why do we continue to debate their tests and results?
Am I missing something? -
#292 by rq3 on 17 Dec, 2015 17:50
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....
Shlieren systems are pretty straightforward if you decide to go ahead with this. Having built a few, a
couple of suggestions:
1) You'll need a reasonably collimated light source, like an old slide projector
2) Rather than use the ubiquitous knife edges, try a pair of ronchi rulings. MUCH easier to align, larger test area, and immensely larger contrast ratio.
3) For a large test area, Fresnel lenses are cheap and useable. The image will suffer, but it will be viewable.
Also a few thoughts on thermal issues.
1) IF the frustum is reasonable rigid, hermetically sealed, and auto-tuned to the drive RF, it won't show any balloon effect from heating. The interior gas will pressurize as it gets hotter, but the gas MASS won't change. Pulling a vacuum on a waveguide (frustum) as others have suggested is begging for interior arcing.
2) If the frustum were placed inside a cylindrical "chimney" that travels with it, one would think that the heat plume would be identical with the "big end up", or the "big end down". For the same number of dissipated watts, the air flow should be identical regardless of frustum vertical orientation. The delta would be...thrust?
Is the arcing mentioned at #1 above dependent on vacuum quality? Ultimately the thing would need to function in vacuum.
If you're referring to a potential Emdrive is space, vacuum external to the wavequide is not relevant. Only vacuum within the wavequide counts. High power wavequide systems are often internally pressurized with dry gas. -
#293 by OnlyMe on 17 Dec, 2015 17:54
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....
Shlieren systems are pretty straightforward if you decide to go ahead with this. Having built a few, a
couple of suggestions:
1) You'll need a reasonably collimated light source, like an old slide projector
2) Rather than use the ubiquitous knife edges, try a pair of ronchi rulings. MUCH easier to align, larger test area, and immensely larger contrast ratio.
3) For a large test area, Fresnel lenses are cheap and useable. The image will suffer, but it will be viewable.
Also a few thoughts on thermal issues.
1) IF the frustum is reasonable rigid, hermetically sealed, and auto-tuned to the drive RF, it won't show any balloon effect from heating. The interior gas will pressurize as it gets hotter, but the gas MASS won't change. Pulling a vacuum on a waveguide (frustum) as others have suggested is begging for interior arcing.
2) If the frustum were placed inside a cylindrical "chimney" that travels with it, one would think that the heat plume would be identical with the "big end up", or the "big end down". For the same number of dissipated watts, the air flow should be identical regardless of frustum vertical orientation. The delta would be...thrust?
Is the arcing mentioned at #1 above dependent on vacuum quality? Ultimately the thing would need to function in vacuum.
If you're referring to a potential Emdrive is space, vacuum external to the wavequide is not relevant. Only vacuum within the wavequide counts. High power wavequide systems are often internally pressurized with dry gas.
With a sealed frustum such as it appears Shell has, how difficult would it be to do just that then pressurize with a dry gas, or would simple pressurization be enough at this point.., and practical?
PS. Didn't Paul March earlier mention that due to leaks their frustum did equalize in vacuum? -
#294 by rq3 on 17 Dec, 2015 17:59
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....
Shlieren systems are pretty straightforward if you decide to go ahead with this. Having built a few, a
couple of suggestions:
1) You'll need a reasonably collimated light source, like an old slide projector
2) Rather than use the ubiquitous knife edges, try a pair of ronchi rulings. MUCH easier to align, larger test area, and immensely larger contrast ratio.
3) For a large test area, Fresnel lenses are cheap and useable. The image will suffer, but it will be viewable.
Also a few thoughts on thermal issues.
1) IF the frustum is reasonable rigid, hermetically sealed, and auto-tuned to the drive RF, it won't show any balloon effect from heating. The interior gas will pressurize as it gets hotter, but the gas MASS won't change. Pulling a vacuum on a waveguide (frustum) as others have suggested is begging for interior arcing.
2) If the frustum were placed inside a cylindrical "chimney" that travels with it, one would think that the heat plume would be identical with the "big end up", or the "big end down". For the same number of dissipated watts, the air flow should be identical regardless of frustum vertical orientation. The delta would be...thrust?
Is the arcing mentioned at #1 above dependent on vacuum quality? Ultimately the thing would need to function in vacuum.
If you're referring to a potential Emdrive is space, vacuum external to the wavequide is not relevant. Only vacuum within the wavequide counts. High power wavequide systems are often internally pressurized with dry gas.
With a sealed frustum such as it appears Shell has, how difficult would it be to do just that then pressurize with a dry gas, or would simple pressurization be enough at this point.., and practical?
PS. Didn't Paul March earlier mention that due to leaks their frustum did equalize in vacuum?
From what I understand, Shell's frustum is not gas tight, and I think she has enough on her plate without introducing hermetic sealing and pressurization. But, given that it's Shell, you never know! -
#295 by OnlyMe on 17 Dec, 2015 18:04
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....
From what I understand, Shell's frustum is not gas tight.
Shell, would have to confirm but,
From her pictures, it appears that once she has tuned, i.e. Adjusted with the micrometer, the bottom might also be sealable. The top is already sealed which would only leave sealing penetration points for waveguides, antennas and the venting line. -
#296 by Rodal on 17 Dec, 2015 18:11
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A small plea from the peanut gallery.
With all due respect, is it possible to limit discussion of tests and results to those that are actively participating in the forum? Given how vaguely the tests have been described by Shawyer and Yang it seems fruitless to continue to debate their results?
EW, Shell, rfmwguy, et al are all actively engaging (as they can) and thus answers about approaches, artifacts etc are readily available. But I, for one, don't see the point of reading the tea leaves of those other tests? Extraordinary results require extraordinary evidence and that is definitely in short supply from them. Why do we continue to debate their tests and results?
Am I missing something?
Yes, you are missing a lot if you limit your reading in this forum to just EW, RFMWGUY and Shell's testing/proposed testing.
The limited discussion that you propose has not been the purpose of these threads, starting from EM Drive thread 1 . For limited discussions of the EM Drive you can access other forums.
To see what you are missing by limiting the discussion, it is advisable to read threads 1 through 5. For a discussion of what this thread's discussion is about, please see the introduction to this thread:
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1455930#msg1455930
There are myriads of examples that show the relevance of discussion of Yang's and Shawyer's tests, but just to mention a recent post, please refer to the recent discussion pointing out the fallacy of assuming that measured forces will scale linearly with input power:
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1458920#msg1458920
showing the strong nonlinearity of Yang's results. There is something to be learned from each published report.
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#297 by robus on 17 Dec, 2015 18:21
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Yes, you are missing a lot if you limit discussion in this forum to just EW, RFMWGUY and Shell's testing/proposed testing.
The limited discussion that you propose has not been the purpose of these threads, starting from EM Drive thread 1 .
To see what you are missing by limiting the discussion, it is advisable to read threads 1 through 5, and the introduction to this thread:
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1455930#msg1455930
No problem, I've been a long time lurker. It just seems like their tests and results have been argued to death and seem to generate a lot of heat and they're not participating to shed light on some of the murkier parts.
But I'm certainly in no position to argue against your judgement! Forgive the intrusion and please carry on
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#298 by aero on 17 Dec, 2015 18:28
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Earlier there was a point made about buoyancy lift from the heated frustum. I did some calculations in an attempt to characterize buoyancy for Shell's EM drive configuration, (frustum, tuning cylinder, and two wave guides) since I do have the needed dimensional data in my meep model.
I calculate the volume to be less than 4.490367E-02 m3. Less than because the wave guides are cut at an angle by the frustum but I simply used the length of the long side. So there are two small wedges that are each counted twice.
So I found standard atmosphere data in the engineering toolbox and calculated the air density at constant volume and pressure using the Ideal gas law. I used the calculator here:
http://www.ajdesigner.com/idealgas/ideal_gas_law_density.php#ajscroll
I did this calculation at both standard temperature and 100 degrees C above standard. That is pretty hot, the temperature of boiling water. Oh, out of deference for Shells' high altitude in the mountains, I used 2000 meter data from the standard atmosphere.
With the above, I calculated buoyancy force = 0.1181471225 newtons, that's 118 mn and certainly not something that can be neglected. If someone is up to the task of checking my numbers, I'm sure it would be appreciated.
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#299 by Rodal on 17 Dec, 2015 18:29
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Observe time dependent transient thermal convection from a cup of coffee. Transient pulsing and spiking bursts from the cup of coffee have nothing to do with the coffee being turned ON and OFF (the coffee cup in this video is not being turned on and off), but they are due to the fluid dynamics (periodic vortex shedding due to natural thermal convection) of the problem. You can imagine how complicated the problem would be if the cup of coffee would be on a burner that would be periodically turned ON and OFF as well, as the turning ON and OFF of the burner would interact with the transient fluid dynamics (vortex shedding) of natural convection.
Imagine the cup of coffee being RFMWGUY's magnetron sitting on top of his EM Drive !!!!
I'll volunteer to get the gear and do the test IF you think its worthwhile.
