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#1820 by RFPlumber on 17 Jan, 2016 05:08
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...I wish my alias would have been “RFProfessor” or at least “RFDoctor”…...
1) Due to your great contributions to this forum, you have been awarded, by acclamation, the title of RFProfessor (Honoris Causa) ages ago
2) Your choice of your alias "Plumber" is shared with very illustrious company: famous Physicist Leonard Susskind began working as a plumber at the age of 16, taking over from his father who had become ill:
https://en.wikipedia.org/wiki/Leonard_Susskind
The man who proved Steven Hawking wrong: Leonard Susskind
LOL
I am honored and humbled to accept this award
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#1821 by RFPlumber on 17 Jan, 2016 05:46
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Major RF Leak
I will appreciate any advice and hints.
As I was preparing for the main test event, I figured someone will certainly question those gaps in my frustum and whether there is enough (if any) RF energy left inside after all the leaks… So I first attached a small WiFI antenna to the power meter sensor and then another antenna - to the 10 mW output of my pre-amp , placed them ~2 m apart and measured the reference level. I then re-connected the pre-amp back, fired up the RF and checked the difference… Came to about 20 dB, ok, about 1W leaking, no big deal, let us cover all the gaps with adhesive copper foil and be done with it. Re-measured Q – it didn’t change, doesn’t matter… re-measured leak… it didn’t appear to change either… umm… I thought my little WiFi antennas may not be showing the real picture because they are likely tuned for exactly 2.4 GHz… and so I replaced them with just 6.5 cm (~1/2 lambda at 2.3 GHz) of copper wire… And this is where things got interesting…
I may be missing something, but everything appears to point that I have got myself a low-powered (thanks, God!) microwave weapon. All those 30W of RF power seem to be radiating out of the small frustum end! And this only happens at resonance frequency.
Facts:
1. Disconnect frustum, connect a 6.5 cm wire to the RF output. Fire 30W. Measure around -11 dBm at the other end (power meter sensor with the same wire antenna 2 m away). Measure reflected power – gives about 15 W, so roughly 15W must be transmitting.
2. Re-Connect and fire frustum. With the small end pointed towards the receiver, the power measurement is -5 dBm(!). This is 4x of Step 1. Granted, there is likely some directivity at play here, but this should still be huge.
3. Rotate frustum 90 degrees horizontally. Power at receive drops 10x (by about 10 dB). Rotate 90 degrees more so the big end is facing the receiver. Power drops about 10x more.
4. With the small end facing the receiver, bring and hold a large copper sheet in front of the small end – power reading drops 100x.
5. With the big end facing the receiver, bring and hold a large copper sheet in front of the _small_ end – power reading jumps up 100x! So the power is either reflecting off the copper sheet, or it is starting to come out of the bigger frustum end!
Isn’t this completely bizarre?! Electrical connection (at least a formal one) does exist between both end plates (FR4) and frustum body and even to the adhesive foil (must be through adhesive). Touching different frustum parts and trying to connect them together “by hand” sometimes results in smaller power readings, but the drop is no more than a few dB. Which makes me believe that replacing all that adhesive copper with a better solution will not change much.
How is this possible?? I am not even sure what to try next about it... Solder the small end to the main body for good? Replace the small end with copper sheet instead of FR4? Neither of these should even be related…
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#1822 by ThinkerX on 17 Jan, 2016 06:33
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Quote
I may be missing something, but everything appears to point that I have got myself a low-powered (thanks, God!) microwave weapon. All those 30W of RF power seem to be radiating out of the small frustum end! And this only happens at resonance frequency
Thank God you caught that before you microwaved something important - like you!
As to the rest, just speculation, but maybe your ends are not thick enough? Remembering the lengthy debates we had here about skin thickness.
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#1823 by Tellmeagain on 17 Jan, 2016 11:19
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Major RF Leak
I will appreciate any advice and hints.
No, your power detector does not detect power. It detects field amplitude. It reads right power only when it uses the right antenna.
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#1824 by DaCunha on 17 Jan, 2016 11:43
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I have kind of a general question:
Since now it is proven, that the dielectric insert is needed to get thrust it seems that Woodward effect and not
Alcubierre space-time warping is what constitutes the physical background of the thrust.
Am I right to conclude, that any spaceship with an EMthruster would be subject to
time dilatation and relativistic mass increase?
E.g. meaning that, while a trip to a different solar system with such a ship, given an EMThruster that can accelerate to some 0.999.. c in an acceptable short time, could take a couple of weeks in the ship coordinate system, it could take years in earth and target planet coordinate systems. -
#1825 by dustinthewind on 17 Jan, 2016 12:01
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Major RF Leak
I will appreciate any advice and hints.
...
Some ideas that popped out to me were if I had a thermal camera I might spray mist and look for hot droplets but only if your sure it wouldn't mess with the electronics. Another idea was to use a wax candle, if it put out enough heat, or possibly peanut butter painted on cardboard/paper and see if it would get glossy (hot) and indicate where it might be coming out of. A sheet of the material those thermometer strips (change color with heat) with a thin wet sheet slapped on the back of it, and stand it up in front of it and turn it on.
Other issues that come to mind are RF police (maybe this isn't an issue as Wifi is everywhere), and I think cataracts can be caused by microwave radiation as the eyeball can't radiate heat very well when the lens heats up. (Maybe other issues are more pressing, as I am not savvy about the biological dangers.) They all depend on the actual amount of radiation being transmitted.
I wonder about the electrical connectivity inside the frustum as opposed to outside, but have to wonder how you know it is in resonance or if the power isn't possibly being reflected to the magnetron and then outside? Could you possibly be picking up the magnetron (signal generator) itself at relatively lower powers? Or are you even using a magnetron as I don't see one that jumps out at me.
A non-likely thought was when currents that are out of phase with respect to a normal current interacting with light, they tend to project radiation in a single direction instead of reflecting light. (phased array) I don't think that should be possible with thick metal plates.
It's probably something simple.
Sorry, just a lot of random thoughts really. Wish you safety. -
#1826 by Rodal on 17 Jan, 2016 13:04
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I have kind of a general question:
Yes, according to Paul March, writing in these threads, he stated repeatedly that he sees the EM Drive "thrust" as due to Woodward's Mach Effect and to Dr. White's Quantum Vacuum formulation and that he sees these as "two sides of the same coin".
Since now it is proven, that the dielectric insert is needed to get thrust it seems that Woodward effect and not
Alcubierre space-time warping is what constitutes the physical background of the thrust.
Am I right to conclude, that any spaceship with an EMthruster would be subject to
time dilatation and relativistic mass increase?
E.g. meaning that, while a trip to a different solar system with such a ship, given an EMThruster that can accelerate to some 0.999.. c in an acceptable short time, could take a couple of weeks in the ship coordinate system, it could take years in earth and target planet coordinate systems.
Concerning time dilation, Prof. Woodward is firmly into General Relativity, and hence the time dilation aspects of Special Relativity fully apply to his formulation. Ditto for Dr. White's hypothesis. -
#1827 by DaCunha on 17 Jan, 2016 13:38
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I have kind of a general question:
Yes[...]
Since [...]
That is unfortunate... I had the hope that we could see a realization of Alcubierre metric within the EMThruster.
But well, it is no use complaining. It is like it is.
This will mean that there is and will be a limit of travelling distance. Although not a technical but a social one.
Since very long travel would mean you could get to other solar systems in weeks but thousands of years would have past when you come back to earth. So you will leave everyone and everything behind.
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#1828 by SeeShells on 17 Jan, 2016 13:57
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Major RF Leak
I will appreciate any advice and hints.
How is this possible?? I am not even sure what to try next about it... Solder the small end to the main body for good? Replace the small end with copper sheet instead of FR4? Neither of these should even be related…
Interesting.
Make a loop for your antenna to plot field strengths and directions radiating from your frustum or any other device. No more different than the MIB detecting bugs in a room, they use a loop to pinpoint any radiation. It might not be your frustum but a leak from your hardware that resides in the front of the small end.
Shell -
#1829 by Rodal on 17 Jan, 2016 14:05
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That Woodward's and White's formulations respect Relativity, including time dilation, does not, by itself, preclude the Alcubierre metric "warp drive". Rather, the Alcubierre "warp drive" problem is the need for "negative mass/energy", something that is not available (and hence considered by many physicists as a non-starter), and it has other important dificulties: https://en.wikipedia.org/wiki/Alcubierre_drive#Difficulties . The creator of the Alcubierre concept, Alcubierre himself is on record saying that the "Alcubierre drive" is not something that can be done:I have kind of a general question:
Yes[...]
Since [...]
That is unfortunate... I had the hope that we could see a realization of Alcubierre metric within the EMThruster.
But well, it is no use complaining. It is like it is.
This will mean that there is and will be a limit of travelling distance. Although not a technical but a social one.
Since very long travel would mean you could get to other solar systems in weeks but thousands of years would have past when you come back to earth. So you will leave everyone and everything behind.Quote from: Alcubierre"from my understanding there is no way it can be done, probably not for centuries if at all" https://twitter.com/malcubierre/status/362011821277839360
. On the other hand, concerning Dr. White's views on this, Dr. White seems to say that it is possible, pay particular attention to this question from a NASA Ames scientist:
"A question with no answer" (acknowledgment to NSF user "StrongGR", Dr. Marco Frasca)
Wikipedia (https://en.wikipedia.org/wiki/Alcubierre_drive#Experiments) states: <<In 2013, the Jet Propulsion Laboratory published results of a 19.6-second warp field from early Alcubierre-drive tests under vacuum conditions>> but it shows no reference to support this statement. The only such experiments I'm aware of are the ones by Dr. White's group at NASA Johnson Eagleworks Lab instead of at JPL (https://en.wikipedia.org/wiki/White%E2%80%93Juday_warp-field_interferometer#Results). -
#1830 by SeeShells on 17 Jan, 2016 14:05
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I have kind of a general question:
Yes[...]
Since [...]
That is unfortunate... I had the hope that we could see a realization of Alcubierre metric within the EMThruster.
But well, it is no use complaining. It is like it is.
This will mean that there is and will be a limit of travelling distance. Although not a technical but a social one.
Since very long travel would mean you could get to other solar systems in weeks but thousands of years would have past when you come back to earth. So you will leave everyone and everything behind.
Reading where Paul March said that the effects are coming from both sides of the same coin made sense.
An analogy. A strong wind blowing across still water will create waves and if the wind is strong enough and at the right speed you'll detach water droplets from the water making spray. The water droplets are like Dr. Whites Virtual Particles and the waves like the March effect. Both sides of the same coin. So you could say the EMDrive is like a tempest in a tea pot.
Shell -
#1831 by SeeShells on 17 Jan, 2016 14:32
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I have kind of a general question:
quote
Since now it is proven, that the dielectric insert is needed to get thrust it seems that Woodward effect and not
Alcubierre space-time warping is what constitutes the physical background of the thrust.
Am I right to conclude, that any spaceship with an EMthruster would be subject to
time dilatation and relativistic mass increase?
E.g. meaning that, while a trip to a different solar system with such a ship, given an EMThruster that can accelerate to some 0.999.. c in an acceptable short time, could take a couple of weeks in the ship coordinate system, it could take years in earth and target planet coordinate systems.
"Since now it is proven, that the dielectric insert is needed to get thrust it seems that Woodward effect and not
Alcubierre space-time warping is what constitutes the physical background of the thrust."
I don't think it has been proven that a dielectric insert is needed but. if one is used running TE012 mode where the energy of the E-fields is focused in the small ends of the frustum would be highly desirable.
On another site someone took my frustum dimensions with dual waveguides and simulated one cycle of 2.45 GHz into the cavity. What is interesting is meep and FEKO agree on the modes but where meep visualizes internals FEKO visualized the cavity walls.
So if a dielectric insert was a way to seed and amplify the effect it seems that a TE012 or another mode exciting the small end is the way to go.
Shell
https://drive.google.com/file/d/0B6juR48k_XoTc1Eya01XeG1SME0/view -
#1832 by Rodal on 17 Jan, 2016 14:38
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NASA's experiments conclusively showed NO thrust with TE012 without a dielectric insert: see https://forum.nasaspaceflight.com/index.php?topic=39214.msg1469685#msg1469685I have kind of a general question:
quote
Since now it is proven, that the dielectric insert is needed to get thrust it seems that Woodward effect and not
Alcubierre space-time warping is what constitutes the physical background of the thrust.
Am I right to conclude, that any spaceship with an EMthruster would be subject to
time dilatation and relativistic mass increase?
E.g. meaning that, while a trip to a different solar system with such a ship, given an EMThruster that can accelerate to some 0.999.. c in an acceptable short time, could take a couple of weeks in the ship coordinate system, it could take years in earth and target planet coordinate systems.
"Since now it is proven, that the dielectric insert is needed to get thrust it seems that Woodward effect and not
Alcubierre space-time warping is what constitutes the physical background of the thrust."
I don't think it has been proven that a dielectric insert is needed but. if one is used running TE012 mode where the energy of the E-fields is focused in the small ends of the frustum would be highly desirable.
On another site someone took my frustum dimensions with dual waveguides and simulated one cycle of 2.45 GHz into the cavity. What is interesting is meep and FEKO agree on the modes but where meep visualizes internals FEKO visualized the cavity walls.
So if a dielectric insert was a way to seed and amplify the effect it seems that a TE012 or another mode exciting the small end is the way to go.
Shell
https://drive.google.com/file/d/0B6juR48k_XoTc1Eya01XeG1SME0/view
This NASA test is very important because it was conducted with exactly the same mode shape claimed by Prof. Yang for her experiments claiming the largest force/PowerInput ever claimed for an EM Drive ( http://emdrive.wiki/Experimental_Results ). And Roger Shawyer has apparently used TE012 and TE013 mode shapes for his Demonstrator and Flight Thruster. So this NASA test is very relevant.
TheTraveller claims that the reason is that NASA's EM Drive small end was slightly below the cut-off condition for open waveguides. Since the EM Drive is a closed resonant cavity and we learned at school that such condition does not apply to closed resonant cavities, and since Shawyer has never published any experiments whatsoever supporting his strange claim for the cut-off condition, this explanation is not convincing. Furthermore, independent calculations show that the NASA test without dielectric should have had strong theoretical Q (79,000), that the cut-off condition is completely irrelevant for resonance of a closed cavity and even more important, the experimental evidence from NASA shows strong confirmation that the NASA test without dielectric was in resonance.
There is no reported test ever by NASA showing thrust for an EM Drive without a dielectric insert.
____________________
As to these FEKO simulations: https://drive.google.com/file/d/0B6juR48k_XoTOUZjTTdTeW14X0U/view
The electric field shows a higher mode distribution which appears inconsistent with the expectation of a TE01p mode. The mode shown by FEKO has m=1 instead of m=0.
Furthermore, since the FEKO simulation shows an electric field on the end plate, it must be a TM (transverse magnetic) rather than TE (transverse electric) mode, since the electric field on the end plates for a TE mode should be zero.
This appears to strongly contradict the expectation of a TE013 mode for Shell's fustrum. Instead FEKO shows TM11p mode, since it looks like TM11 on the end plate (perhaps TM112 ?) .
While the mode shape of the electric field on the end plate (TM11) appears well-formed, the electric field on the lateral conical walls modeled by FEKO appears malformed: not axisymmetric. This appears to be a consequence of the asymmetry imposed by the lateral waveguides that distort what would have otherwise been an axisymmetric mode shape. The fields on the lateral conical walls are difficult to compare to Meep simulations because there has been no "Meeper" to this date showing electromagnetic fields on the lateral conical walls because Meep models have used Cartesian coordinates and nobody has written code to transform the fields in Cartesian coordinate to transform them to the conical surface.
Picture of Electric Field from FEKO simulation attached below.
Acknowledgment to IslandPlaya, as to whom full credit for the FEKO simulation, including the attached image, belongs to
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#1833 by original_mds on 17 Jan, 2016 14:44
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Is there a list anywhere of expected milestones for those that are doing builds? E.g. approximate dates of "first light" for new systems or rebuilds. I know many of us are anxious to see more experimental data and are wondering if we should be thinking in terms of days, weeks, or months (hopefully not years
).
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#1834 by Rodal on 17 Jan, 2016 15:28
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Acknowledgment to IslandPlaya, as to whom full credit for the FEKO simulation, including the attached image, belongs
The FEKO simulation (https://drive.google.com/file/d/0B6juR48k_XoTOUZjTTdTeW14X0U/view) of Shell's experiment, with a 180 degree phase shift, shows a TM21p mode shape instead of TM11p with 0 degree phase shift. This higher order (quadrupole) transverse magnetic mode shape is similar (on the circular cross-section) as NASA's mode shape used for their experiments in vacuum (TM212 for NASA).
This mode shape is also inconsistent with the expectation of a TE013 mode shape.
The poles for this TM21p mode FEKO simulation are not equal in size (they should be completely equal in size for a well-formed axisymmetric TM21p mode shape). This maybe due to the asymmetry imposed by the dual waveguides: observe that the poles that align with the waveguides axis are smaller in size that the poles that are perpendicular to the waveguides axis.
The FEKO mode shape for this 180 degree phase shift on the lateral conical walls is not axisymmetric. This appears to be a consequence of the asymmetry imposed by the lateral waveguides that distort what would have otherwise been an axisymmetric mode shape.
_______
Can't comment more than that as I did not find out more information about what particular FEKO module simulation was used (is the FEKO Finite Difference in time and space being used? or is it the FEKO Boundary Element Method (which the author calls Method of Moments) ?, or is the FEKO Finite Element simulation being used. Many questions ...
_________
I also attach a picture of what the Electric Field quadrupole is supposed to look like for TM212 in a perfectly axisymmetric case
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#1835 by X_RaY on 17 Jan, 2016 15:46
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The FEKO simulation (https://drive.google.com/file/d/0B6juR48k_XoTOUZjTTdTeW14X0U/view) of Shell's experiment, with a 180 degree phase shift, shows a TM21p mode shape instead of TM11p with 0 degree phase shift. This higher order (quadrupole) transverse magnetic mode shape is similar (on the circular cross-section) as NASA's mode shape used for their experiments in vacuum (TM212 for NASA).
I saw this effect often for truncated conical cavities during simulations using EMPro. For a given phase it looks clear like a specific mode but a quarter or half period later it seems to be another mode shape.
This mode shape is also inconsistent with the expectation of a TE013 mode shape.
The FEKO mode shape on the circular cross-section for this 180 degree phase shift is not as well formed as the FEKO simulation for zero degree phase shift, as the poles are not equal in size (they should be completely equal in size for a well-formed TM21p mode shape). The FEKO mode shape for this 180 degree phase shift on the lateral conical walls is very malformed.
_______
Can't comment more than that as I did not find out more information about what particular FEKO module simulation was used (is the FEKO Finite Difference in time and space being used? or is it the FEKO Boundary Element Method (which the author calls Method of Moments) ?, or is the FEKO Finite Element simulation being used. Many questions ...
Nevertheless at the of the day you are right, its definitive no TE01 mode! -
#1836 by Rodal on 17 Jan, 2016 15:49
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Agreed, upon further thought I edited and added:The FEKO simulation (https://drive.google.com/file/d/0B6juR48k_XoTOUZjTTdTeW14X0U/view) of Shell's experiment, with a 180 degree phase shift, shows a TM21p mode shape instead of TM11p with 0 degree phase shift. This higher order (quadrupole) transverse magnetic mode shape is similar (on the circular cross-section) as NASA's mode shape used for their experiments in vacuum (TM212 for NASA).
I saw this effect often for truncated conical cavities during simulations using EMPro. For a given phase it looks clear like a specific mode but a quarter or half period later it seems to be another mode shape.
This mode shape is also inconsistent with the expectation of a TE013 mode shape.
The FEKO mode shape on the circular cross-section for this 180 degree phase shift is not as well formed as the FEKO simulation for zero degree phase shift, as the poles are not equal in size (they should be completely equal in size for a well-formed TM21p mode shape). The FEKO mode shape for this 180 degree phase shift on the lateral conical walls is very malformed.
_______
Can't comment more than that as I did not find out more information about what particular FEKO module simulation was used (is the FEKO Finite Difference in time and space being used? or is it the FEKO Boundary Element Method (which the author calls Method of Moments) ?, or is the FEKO Finite Element simulation being used. Many questions ...
Nevertheless at the of the day you are right, its definitive no TE01 mode!QuoteThe poles for this TM21p mode FEKO simulation are not equal in size (they should be completely equal in size for a well-formed axisymmetric TM21p mode shape). This maybe due to the asymmetry imposed by the dual waveguides: observe that the poles that align with the waveguides axis are smaller in size that the poles that are perpendicular to the waveguides axis.
The FEKO mode shape for this 180 degree phase shift on the lateral conical walls is not axisymmetric. This appears to be a consequence of the asymmetry imposed by the lateral waveguides that distort what would have otherwise been an axisymmetric mode shape. -
#1837 by Mulletron on 17 Jan, 2016 15:50
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…
This design addresses the shortcomings of the prior test in phasing the two incoming RF signals. I talked about this method very lightly about 6 months ago using two phase locked magnetrons, but I found way too many design hurdles to overcome using the direct injection method. One was the massive amount of excess heat from the magnetrons that would be strapped onto the cavity, swamping any measurements of thrust.
If the burning probe matchstick test failed because of design limitations (which it kind of did, got a large force displacement on the digital scales before it fried itself) I had plan number 2. And I'll present it here for the first time and invite comments.
Getting together pieces and parts to build, I've had to go surplus because it's not cheap. From the undocumented power on test results of the first one I know it's the way I need to go to assure a stable clean high power high Q mode control into my drive.
…
PS: RfPlumber this is why I hadn't answered your last question, simply I've gone beyond it and I'd welcome any inputs you or anyone may have.
I wish my alias would have been “RFProfessor” or at least “RFDoctor”… being what it is though here’s some feedback (I am not suggesting all these points need to be addressed, just something to think about):
1. This will likely cost on the order of $10K+ to build if using new parts.
2. I am not sure you need 2 separate phase shifters (assuming the splitter gives you the initial 180, I don’t know if it is the case though). Otherwise you do.
3. You still aren’t measuring no RF power anywhere… So you will be turning the knobs on those phase shifters looking for what exactly? For thrust?
4. I am assuming this will use an off-the-shelf magnetron to waveguide launcher?
5. What is the Q factor of your frustum? Sorry, I am repeating this, but it looks like magnetron frequency drift is on the order of a few MHz over the first few minutes of operation. Hence anything with Q over a couple thousand will be out of resonance very shortly.
Google for “magnetron phase stability”. The very first link:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwib6e-ulK_KAhUOyGMKHQagCxAQFggiMAA&url=https%3A%2F%2Fwww.ll.mit.edu%2Fmission%2Faviation%2Fpublications%2Fpublication-files%2Fatc-reports%2FLabitt_1977_ATC-74_WW-15318.pdf&usg=AFQjCNFpB3-SOv1pT9PHkLY5WYdUSS-Tvg
So it may not be the thermal frustum expansion which ruins the resonance mode, it may be the magnetron freq drift (or both). Without measuring anything how do you know it is out of resonance? (No thrust? )
6. Not immediately related to this RF plan, but why are you only worried about (and trying to prevent) frustum controlled thermal expansion in one direction? Its resonance frequency depends not just on its central length, but on both end diameters as well… So it will still be changing.
7. What power supply are you using for your magnetron? Is it really a true 1 kW+ 4KV DC monster?
Overall, my gut feel is that this is a bit of an overkill, but it will most likely achieve the task. What is the most expensive way of inducing a TE mode? This could be a winner.
Other thoughts:
Assuming there is indeed something special about magnetron in regard to producing new effects, it then seems that the more one is trying to bring magnetron & feed to that of the perfect pure RF source + ideal coupler, the less is the chance of seeing any new effects. If the effect is indeed specific to magnetron RF output, when the important differences to keep in mind appear to be these:
1. Frequency is not stable (A few kHz difference over a microsecond timeframe).
2. Frequency drift at start-up (A few MHz over the first few minutes).
3. Pulsed (~10-30 ms?) RF output if using microwave oven power supply. (The built-in 1 uF capacitor is not enough to deliver full DC power over the half-cycle of 60 Hz).
At this time only EW knows (or at least has a theory about) which of these are required to produce thrust. Unfortunately they are not sharing.
A few months ago Paul March mentioned the following:QuoteI think I may have verified today the need for large time rate of change of the resonant circuit phase changes as the RF amplifier driven 1,937.088 MHz, +/- ~25kHz sine wave oscillates back and forth through the resonance frequency of the frustum cavity.....
Continued in full at link below.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1366630#msg1366630
I'm not sure if this was later further verified to be an important feature.
This happened 6 months later:
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1434368#msg1434368
So we're aware that magnetrons are notorious for phase noise and this was thrown around as possibly being a useful feature, but to my knowledge, it hasn't been shown to be important since.
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#1838 by Rodal on 17 Jan, 2016 16:04
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I find the FEKO and COMSOL simulations much easier to digest than the Meep simulations because:
1) FEKO and COMSOL readily show the fields on the lateral conical walls. No Meeper has written code to transform the Cartesian coordinate fields to a conical surface hence Meepers up to now are completely unable to show the electromagnetic fields on the conical walls.
2) FEKO and COMSOL images always make explicit what electromagnetic field is being shown or what quantity is being shown (for example COMSOL can also show surface losses, etc.). Several times "Meepers" show images that do not state what is being shown (not stating whether it is an electric field or a magnetic field, or what component of the Cartesian field is being shown). This is particularly troublesome for Meep, because Meepers use solutions expressed in terms of a Cartesian planar geometry which is NOT the intrinsic geometry of the problem, as the intrinsic geometry of the problem is a conical surface.
3) FEKO and COMSOL always show the electromagnetic fields in SI units that one can relate to. Meep electromagnetic field images are frequently shown by Meepers without a conversion ribbon to ascertain the numerical magnitude of the electromagnetic fields and Meep uses dimensionless units that frequently are not converted to physical SI units by Meepers when they do display numerical fields, hence one can readily obtain a much better physical feel for FEKO and COMSOL simulations than for the images displayed by "Meepers".
4) A practical example of these advantages of COMSOL is exemplified by RFPlumber who was readily able to show surface losses for a simulation as well as the current produced by the magnetic field when users asked about such quantities.
5) COMSOL uses the Finite Element method, which is clearly superior to the Finite Difference Method. FEKO has many modules, including FEA, FDTD, and even the Boundary Element method which has great advantages for equations like Maxwell's equations that are linear in nature, because one can use Green's functions. However, it is not clear what FEKO module is being used. It appears that it may be the FDTD FEKO module. If that is the case, the FEKO module being used is using Finite Difference method, just like Meep.
6) It appears that the Meep solutions (and now the FEKO solutions being shown) are transient (travelling wave) solutions, while the COMSOL simulations being shown have been steady-state resonance (standing wave) solutions.
7) A big advantage of Meep used in academia and institutional and private R&D is that Meep is an open code, where users can write their own constitutive equations, etc., and standard Meep functions include the ability to model anisotropic and nonlinear material behavior, however these Meep functionalities have not yet been exploited in Meep models of the EM Drive. -
#1839 by Mulletron on 17 Jan, 2016 16:18
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I figure this may be of interest to @Rodal (you dig Finite element analysis) and @Notsosureofit (your hypothesis featuring an accelerated frame of reference).
http://people.clarkson.edu/~nanosci/jse/B/inpress/vaish.pdf
I will appreciate any advice and hints.
).