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#140 by Rodal on 14 Dec, 2015 14:32
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It is known that
1) the impedance of an antenna in a cavity is significantly different from the impedance of an antenna located in free space. The analysis of antennas in a cavity involves: Green functions, problematic integration of logarithmic singularities, and Galerkin solution methods; and hence more difficult to analyze.
2) it is simpler to couple waveguides by using one or more apertures in the common wall than by coupling waveguides by means of a probe or by means of a loop antenna, or a combination of the two.
3) the theory of coupling waveguides by small apertures was developed by Nobel Prize winner Hans Bethe (his patent: https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US2519734.pdf and his video discussing joining MIT's Radiation Laboratory: http://www.webofstories.com/play/hans.bethe/86;jsessionid=04D1B0A62DF1EE041BBB172D5420BB82 on propagation in waveguides ). The theory is more amenable than the theory of coupling with probes or loops, which entail Galerkin solutions, for example.
4) a number of Meep simulation runs discussed in previous threads show the complications engendered by using a dipole antenna excitation (mainly excitation of very unsymmetric modes and malformed modes) to excite TM modes and even worse for loops trying to excite TE modes (which Meep has shown to be very difficult to excite using loops).
5) Meep simulation runs discussed in previous threads were successful in exciting TE modes by coupling of symmetrically placed waveguides (while Meep excitation of well-formed symmetric TE modes in the frustum of a cone cavity was NOT feasible using loops).
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons (the cavity excitation is much more difficult to analyze with them), as opposed to coupling through symmetrically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(I am not sympathetic with Shawyer and Yang's "theories", but I don't understand the apparent divergence between Shawyer and Yang's predilection for TE modes vis-a-vis the DIY discussion regarding magnetrons or dipoles or loops which are difficult to analyze and therefore will result in more difficult to predict excitation mode shape of the cavity). Yang (who claims the highest thrust force per input power) has been using coupling through waveguides and Shawyer in his latest papers has also been suggesting coupling through waveguides.
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#141 by rfmwguy on 14 Dec, 2015 14:42
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Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmetrically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
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#142 by ThereIWas3 on 14 Dec, 2015 15:21
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I also wonder about the efficacy of trying to inject linearly polarized energy into a cavity that has a circular cross section. That may make sense in a rectangular waveguide, but not a frustrum. Squirting RF in from the sides would seem to me to excite all sorts of wierd patterns within the cavity as well. Did any of the loop excitation attempts put the plane of the loop parallel to the end-plates?
Dipoles are easy to describe in meep, but I would be eager to see what people have come up with for meep models of waveguide injection. Especially since that is what Shawyer used.
Frustrum geometry would make calculation of the impedance very "interesting".
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#143 by Rodal on 14 Dec, 2015 15:34
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... Did any of the loop excitation attempts put the plane of the loop parallel to the end-plates?...
Yes (Meep runs were conducted with the loop parallel to the end-plates, at different locations) -
#144 by rfmwguy on 14 Dec, 2015 15:40
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I also wonder about the efficacy of trying to inject linearly polarized energy into a cavity that has a circular cross section. That may make sense in a rectangular waveguide, but not a frustrum. Squirting RF in from the sides would seem to me to excite all sorts of wierd patterns within the cavity as well. Did any of the loop excitation attempts put the plane of the loop parallel to the end-plates?
Yes, EW did this...pardon the repeat of an old pic:
Dipoles are easy to describe in meep, but I would be eager to see what people have come up with for meep models of waveguide injection. Especially since that is what Shawyer used.
Frustrum geometry would make calculation of the impedance very "interesting".
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=38577.0;attach=1080448 -
#145 by Rodal on 14 Dec, 2015 15:52
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I also wonder about the efficacy of trying to inject linearly polarized energy into a cavity that has a circular cross section. That may make sense in a rectangular waveguide, but not a frustrum. Squirting RF in from the sides would seem to me to excite all sorts of wierd patterns within the cavity as well. ...
A bad example that illustrates that problem is Tajmar's experiments at TU Dresden under advice from Shawyer (according to Tajmar's paper), coupling to their small EM Drive with a waveguide with a very large opening (relative to the size of the EM Drive), and furthermore coupling asymmetrically through only one side. This may have resulted in side forces measured in Tajmar's experiments.
The successful Meep simulation runs were performed using two waveguides coupling symmetrically from opposite sides of the EM Drive, as suggested by Shell. -
#146 by oliverio on 14 Dec, 2015 16:08
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Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmetrically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
I'm throwing my featherlike weight in with your argument that mode generation may indeed not be the most important thing-- at least, stable singular mode generation. I don't have a lot of experience with electromagnetism but I have a decent amount with acoustics; generally, the thing you want out of an acoustic system is high Q, so-to-speak, and resonance is one way to achieve that, but even a high-Q and high-resonance approach will not make for a proper-sounding acoustic system. Much of that is in the details of how the energy in resonance is directed by its container, and if the EMDrive effect thus observed is real, it seems more like that kind of a situation (i.e. "where and what shape should we put the sound-holes on this violin to guarantee stable tones and loud volume?" There is not going to be one vibrational mode generated in a violin, its resonance changes quite tangibly depending on the tone being played, but a nice violin will always play a bright tone with the proper undertones and overtones, which is the combination we want, not necessarily just power reflection and a certain resonance pattern.) -
#147 by rfmwguy on 14 Dec, 2015 16:35
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Good points, Doc and Shell are a step ahead of me regarding why the emdrive has results over the years. Its a bit into the theoretical realm with pointing vectors and the like...for me, it was a brute force thing, an attempt to match impedance and get a resonance set up...sort of an EM "ringing" without knowing what mode forms up.
Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmetrically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
I'm throwing my featherlike weight in with your argument that mode generation may indeed not be the most important thing-- at least, stable singular mode generation. I don't have a lot of experience with electromagnetism but I have a decent amount with acoustics; generally, the thing you want out of an acoustic system is high Q, so-to-speak, and resonance is one way to achieve that, but even a high-Q and high-resonance approach will not make for a proper-sounding acoustic system. Much of that is in the details of how the energy in resonance is directed by its container, and if the EMDrive effect thus observed is real, it seems more like that kind of a situation (i.e. "where and what shape should we put the sound-holes on this violin to guarantee stable tones and loud volume?" There is not going to be one vibrational mode generated in a violin, its resonance changes quite tangibly depending on the tone being played, but a nice violin will always play a bright tone with the proper undertones and overtones, which is the combination we want, not necessarily just power reflection and a certain resonance pattern.)
Acoustic analysis is related. Parts of a speaker enclosure as well as parts of a musical instrument itself starts complex resonance patterns...you are absolutely correct. Doc and shell might be closing in on something with the modeling. If their thoughts are correct, it will be a great step towards upscaling the effect. We hope... -
#148 by Chrochne on 14 Dec, 2015 16:36
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Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmerically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
I'm throwing my featherlike weight in with your argument that mode generation may indeed not be the most important thing-- at least, stable singular mode generation. I don't have a lot of experience with electromagnetism but I have a decent amount with acoustics; generally, the thing you want out of an acoustic system is high Q, so-to-speak, and resonance is one way to achieve that, but even a high-Q and high-resonance approach will not make for a proper-sounding acoustic system. Much of that is in the details of how the energy in resonance is directed by its container, and if the EMDrive effect thus observed is real, it seems more like that kind of a situation (i.e. "where and what shape should we put the sound-holes on this violin to guarantee stable tones and loud volume?" There is not going to be one vibrational mode generated in a violin, its resonance changes quite tangibly depending on the tone being played, but a nice violin will always play a bright tone with the proper undertones and overtones, which is the combination we want, not necessarily just power reflection and a certain resonance pattern.)
Basicaly what you say is that we may need a musician and a scientist that understand music waves and instrument manufacture and also understands all kinds of waves in science to try to understand the emdrive. However, we know from EW tests that they observed thrust in vacuum as well. Still interesting idea
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#149 by rfmwguy on 14 Dec, 2015 17:00
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That's one of the key differences between sound and RF. Sound is a vibration of a medium, such as air. RF only needs a vacuum. Any other medium can attenuate the RF, moist air, liquids, buildings etc.,
Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmerically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
I'm throwing my featherlike weight in with your argument that mode generation may indeed not be the most important thing-- at least, stable singular mode generation. I don't have a lot of experience with electromagnetism but I have a decent amount with acoustics; generally, the thing you want out of an acoustic system is high Q, so-to-speak, and resonance is one way to achieve that, but even a high-Q and high-resonance approach will not make for a proper-sounding acoustic system. Much of that is in the details of how the energy in resonance is directed by its container, and if the EMDrive effect thus observed is real, it seems more like that kind of a situation (i.e. "where and what shape should we put the sound-holes on this violin to guarantee stable tones and loud volume?" There is not going to be one vibrational mode generated in a violin, its resonance changes quite tangibly depending on the tone being played, but a nice violin will always play a bright tone with the proper undertones and overtones, which is the combination we want, not necessarily just power reflection and a certain resonance pattern.)
Basicaly what you say is that we may need a musician and a scientist that understand music waves and instrument manufacture and also understands all kinds of waves in science to try to understand the emdrive. However, we know from EW tests that they observed thrust in vacuum as well. Still interesting idea
Now, the big questions is what does the vacuum consist of to be able to be a "perfect" medium for electromagnetic waves? Aether or empty? Now, that gets a lot of discussions started. -
#150 by SeeShells on 14 Dec, 2015 17:17
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Also in this image look at the mode generation. https://drive.google.com/file/d/0B1XizxEfB23tYVNDalhQel9tZ3c/view
If we put an antenna 1/4 from the top or bottom the cavity natural resonance mode generation will not be at the same place as the antenna and cause inter-modal actions decreasing the Q as they build and collapse.
It makes sense to place the antenna center frustum parallel to the bottom in this mode TE013 and for other modes you need to know the mode pattern to properly place if your going to use a dipole.
This way you're adding to the Q not causing a degradation.
Make sense?
Shell
I wanted to point out that this image is of the group B-field and not the E-field because the maximum touches the metal walls. This paper here: http://cas.web.cern.ch/cas/Denmark-2010/Lectures/Wolski-2.pdf page 25 they point out that at the metal walls E_tangent=0 and but B_tan doesn't have to be zero. The group electric maximum of light inside the cavity should be at the magnetic nodes which look to be at about 1/4 wavelength (or the empty spots between the magnetic fields).
The antenna then does work against this electric field to store energy in the cavity. I think at mid cavity it might do negative work when trying to inject a signal and store energy in the current in the antenna instead of the cavity. Hopefully I am not too far off here.
P.S. I think it is supposed to be desirable to have the shape of the antenna in the shape of the current flow desired to be generated. Transverse electric/TE being a loop or loops parallel to the plate and TM being vertically orientated loops. This appears to be TM.
I guess your antenna looks about right but I am not sure what it should look like in 3 dimensions. Also to match the magnetic field the current would have to be going in at the same time on both antenna ends unlike in the animated video of the antenna.
One of my fav songs Dustinthewind... I would agree with you but to see what is really happening you need to look at the frustum in X,Y and Z slices and tell me how many modes of operation do you see. https://drive.google.com/drive/folders/0B1XizxEfB23tbVYwc1Nsa29yZlk
I think it's a good time to quickly summarize some of what we have done in the last 6 months inserting RF energy into the frustum.
Loops and antennas inside if the frustum can be problematic in the placing, we have seen it with meep and some real world tests. Even if you consider magnetron direct injection it's a 1/4 wave snub antenna into the bottom or top or sides. What your asking the asymmetrical cavity to do is act as the launcher and produce high energy, high Q modes.
TE modes which have shown by some evidence to produce the greatest thrusts are hard to produce with a single dipole, snub or even a loop antenna. I believe this is one reason the Chinese, Shawyer, NASA EagleWorks, Tajmar have elected to go to a waveguide insertion. Late this summer after hundreds of hours of aero and others running simulations and Dr. Rodal offering his unparalleled expertise it became clear that the placement of antennas was problematic to sustain a good Q and a non-interactive decaying modes within the frustum.
Dipoles when placed 1/4 WL, parallel to the endplates will tend to want to excite a TM mode and if the cavity for the frequency was designed for a TE mode for the frequency you could get 2+ interacting modes TEs and TMs or a combination of both. Now this depends on the cavity dimensions (look at Davies's mode chart and this is for just one base size and one set length) and incoming frequency and where the resonate modes cross paths.
https://drive.google.com/drive/folders/0B1XizxEfB23tbVYwc1Nsa29yZlk was done with a 30MHz bandwidth and even then you can see multi mode generations in the frustum. The interesting thin is when aero reduced the bandwidth ~200 hz the Q dropped to very little and the energy inside of the frustum was quite small. For some reason and I'm still looking into the why the extra modes when driven by a relatively non-interfering waveguide into the frustum increased the Q several orders of magnitude.
I wished I knew what Davies used for his modeling of the resonate wavechart. Then we could match the best preforming frustums (at this time it's waveguide insertion) to the different sizes. One thing I gleaned from looking at the chart is the frustum being injected with a 2.45GHz (top yellow oval Band Width oval) and how many modes interacted. Interesting to note here why did Davies only plot out and label the TE modes?
Need another cup of coffee and will write more later.
Shell
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#151 by Rodal on 14 Dec, 2015 17:19
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That's one of the key differences between sound and RF. Sound is a vibration of a medium, such as air. RF only needs a vacuum. Any other medium can attenuate the RF, moist air, liquids, buildings etc.,
Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmerically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
I'm throwing my featherlike weight in with your argument that mode generation may indeed not be the most important thing-- at least, stable singular mode generation. I don't have a lot of experience with electromagnetism but I have a decent amount with acoustics; generally, the thing you want out of an acoustic system is high Q, so-to-speak, and resonance is one way to achieve that, but even a high-Q and high-resonance approach will not make for a proper-sounding acoustic system. Much of that is in the details of how the energy in resonance is directed by its container, and if the EMDrive effect thus observed is real, it seems more like that kind of a situation (i.e. "where and what shape should we put the sound-holes on this violin to guarantee stable tones and loud volume?" There is not going to be one vibrational mode generated in a violin, its resonance changes quite tangibly depending on the tone being played, but a nice violin will always play a bright tone with the proper undertones and overtones, which is the combination we want, not necessarily just power reflection and a certain resonance pattern.)
Basicaly what you say is that we may need a musician and a scientist that understand music waves and instrument manufacture and also understands all kinds of waves in science to try to understand the emdrive. However, we know from EW tests that they observed thrust in vacuum as well. Still interesting idea
Now, the big questions is what does the vacuum consist of to be able to be a "perfect" medium for electromagnetic waves? Aether or empty? Now, that gets a lot of discussions started.
Well, we may start by someone giving an example of a completely closed acoustic cavity that can experience self-acceleration (as claimed for the EM Drive). I don't know of any such case. Acoustic tapered cavities don't experience self acceleration, one can show that the momentum in such a completely enclosed cavity is self-cancelling.
The trombone and other wind instruments selected as examples in previous discussions are akin to open waveguides, not to completely closed cavities.
Ditto for a loudspeaker: you will not be able to to hear a loudspeaker located inside a completely enclosed cavity that does not let any air in and out of the enclosure, if you are outside the enclosure. -
#152 by Flyby on 14 Dec, 2015 17:20
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Somewhat related to the waveguide topic...
As I was trying to figure out the schematics of the tubing and plumbing on Shawyer's rotating rig, I noticed the waveguide feeding the frustum has either a strange extension to it, or enters the frustum at a different spot i first thought...
My initial thought was that the waveguide fed into the frustum at the top.... now I'm not so sure anymore.
and what are those shiny connectors doing on the black waveguide just above the frustum (pic1)?
also, notice the strange brass knobs at the bottom of pic2, on/in the waveguide. They make me think of Yang's adjusting screws....
any thoughts on all that???
Both pictures show a slightly different version. I suspect the rig of pic1 is a further evolution of the one we see in pic2, because it has additional plumbing and cooling radiators.
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#153 by Rodal on 14 Dec, 2015 17:32
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...
I wished I knew what Davies used for his modeling of the resonate wavechart. Then we could match the best preforming frustums (at this time it's waveguide insertion) to the different sizes. One thing I gleaned from looking at the chart is the frustum being injected with a 2.45GHz (top yellow oval Band Width oval) and how many modes interacted. Interesting to note here why did Davies only plot out and label the TE modes?
Need another cup of coffee and will write more later.
Shell
I think that Frank Davis' analysis (at NASA, using COMSOL Finite Element analysis) is an eigenvalue analysis, it is not a transient response analysis due to a particular excitation (*). No excitation of any kind is modeled in an eigenvalue analysis. As such, the eigenvalue analysis just gives the eigenvalues at which resonance occurs.
Think, for example, of the resonance of a string (clamped at both ends). One can perform an eigenvalue analysis (for a given length of the string, knowing its modulus of elasticity and its density, and the cross-sectional area of the string) which will give the resonant response of the string. Such eigenvalue analysis for the resonant response of the string tells you just that: the eigenvalues at which resonance can occur.
It does not say what will happen if you play the string instrument by plucking the string at a particular place with a particular excitation. To know that one has to perform a force-response analysis (either using mode analysis for linear problems or using a transient response analysis for general problems).
__________
(*) The Meep analyses run by aero have been transient response analyses. -
#154 by SeeShells on 14 Dec, 2015 17:32
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CLIPPED down...It is known that
Much better said than what I rambled on about but the same conclusions can be drawn.
(I am not sympathetic with Shawyer and Yang's "theories", but I don't understand the apparent divergence between Shawyer and Yang's predilection for TE modes vis-a-vis the DIY discussion regarding magnetrons or dipoles or loops which are difficult to analyze and therefore will result in more difficult to predict excitation mode shape of the cavity). Yang (who claims the highest thrust force per input power) has been using coupling through waveguides and Shawyer in his latest papers has also been suggesting coupling through waveguides.
Well said Dr. Rodal, well said.
Shell -
#155 by oliverio on 14 Dec, 2015 17:34
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That's one of the key differences between sound and RF. Sound is a vibration of a medium, such as air. RF only needs a vacuum. Any other medium can attenuate the RF, moist air, liquids, buildings etc.,
Cost probably, Doc. Also the rectangular slot(s) are side-injected meaning a new frustum would have to be made if injection point needed to be changed. Hole plugging would be...uhhhh...not cool.
(...)
Therefore, why is there so much emphasis on dipoles and direct excitation via magnetrons, which are much more difficult to analyze, as opposed to coupling through symmerically placed waveguides which are easier to analyze and more successful in producing the TE modes that have been promoted by Shawyer and Yang ?
(...)
This is coming from an experimenter who didn't spend much time trying to design with a specific mode in mind...mainly because I'm not yet convinced any mode is better than another. It very well MAY be, it wasn't in my game plan to fire off one mode or another.
Part of the process we're going thru is to play around with different techniques and see which one launches thru the roof
I'm throwing my featherlike weight in with your argument that mode generation may indeed not be the most important thing-- at least, stable singular mode generation. I don't have a lot of experience with electromagnetism but I have a decent amount with acoustics; generally, the thing you want out of an acoustic system is high Q, so-to-speak, and resonance is one way to achieve that, but even a high-Q and high-resonance approach will not make for a proper-sounding acoustic system. Much of that is in the details of how the energy in resonance is directed by its container, and if the EMDrive effect thus observed is real, it seems more like that kind of a situation (i.e. "where and what shape should we put the sound-holes on this violin to guarantee stable tones and loud volume?" There is not going to be one vibrational mode generated in a violin, its resonance changes quite tangibly depending on the tone being played, but a nice violin will always play a bright tone with the proper undertones and overtones, which is the combination we want, not necessarily just power reflection and a certain resonance pattern.)
Basicaly what you say is that we may need a musician and a scientist that understand music waves and instrument manufacture and also understands all kinds of waves in science to try to understand the emdrive. However, we know from EW tests that they observed thrust in vacuum as well. Still interesting idea
Now, the big questions is what does the vacuum consist of to be able to be a "perfect" medium for electromagnetic waves? Aether or empty? Now, that gets a lot of discussions started.
Well, we may start by someone giving an example of a completely closed acoustic cavity that can experience self-acceleration (as claimed for the EM Drive). I don't know of any such case. Acoustic tapered cavities don't experience self acceleration, one can show that the momentum in such a completely enclosed cavity is self-cancelling.
The trombone and other wind instruments selected as examples in previous discussions are akin to open waveguides, not to completely closed cavities.
Ditto for a loudspeaker: you will not be able to to hear a loudspeaker located inside a completely enclosed cavity that does not let any air in and out of the enclosure, if you are outside the enclosure.
On the contrary, my fine doctor friend, I think I can point out a clear example that is unfortunately just a bit too close to some hackneyed theories that have been thrown about on this thread, but I'll suggest it anyway.
Say that you took a very light cavity of resonant wood, and enclose within it an acoustic speaker; this cavity is shaped like a very short, wide rectangle, but perhaps with one sideplate shorter than the other sideplate. (A rectangular frustrum?) Place this object against a surface.
I contend that due to doppler shift, given the right dimensions, one side of the rectangle will clearly vibrate at a higher frequency as is the case when one hears a loud noise in an enclosed room (it sounds higher pitched than if you had been in a larger room). I contend as well that this object would slide across a surface with the right frictional coefficient, with an orientation dependent upon the rectangular frustrum's orientation, the pitch, and mode excited within.
Correct me on the thought experiment but I'm pretty sure that is all within the confines of well-understood physics (it's a vibrational motor, right? An oscillator or something is what I seem to recall the terminology being.) Is it not the case that this might work as a vague analogue (read: very vague, for I am not trying to say that the vibrational friction of an EMDrive propels it anywhere) for the way that an EMDrive might "push" against space without propelling itself? -
#156 by Rodal on 14 Dec, 2015 17:40
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The motion on a frictional surface is well-understood (through both experiments, theoretical and numerical analysis). It is due to stick-slip friction and the nonlinear characteristic of the frictional law (multilinear if you want, including the fact that the slding frictional coefficient is usually smaller than the static friction coefficient) .
In this case what is proposed for the EM Drive (by Shawyer and others) is that it can result in self-acceleration in space without the influence of any fields or outside forces. (No friction between the EM Drive spaceship and the vacuum).
Do you know of any self-enclosed acoustic cavity that can experience self-acceleration in space, without the influence of any fields or outside forces ? -
#157 by SeeShells on 14 Dec, 2015 17:49
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That says it very clear to me. The only thing that is in a frustum cavity that also is on the outside is Spacetime. If we are to assume that nothing can get out to produce thrust it has to be something that permeates inside of the frustum fro the outside. That's the QV of space, that is even present in a black hole, nothing escapes QV and Spacetime. The question is simple how do we interact with it inside of this can of microwaves? The answer is the tough part.
Shell
added: I once said give me a hole and I'll give you thrust but I've finally settled on that this is truly a enclosed frame and there is no hole. It is the one thing that permeates through the drive and that is the QV of spacetime. I can see why Dr. White is pushing his theories of the production of Virtual Particles from the device but that has several things in it's theory that have come under question (better people than me at QED theories). I'm left with the stinging question of why has EagleWorks seen a time differential in their laser inferometer test and even in the hackaday mini drive seems to show something weird.
Shell
Corrected missspellings sorry someone chatting at me and a cat on my keyboard saying love me, way to much input for good output. -
#158 by ThereIWas3 on 14 Dec, 2015 18:24
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added: I once said give me a hole and I'll give you thrust but I've finally settled on that this is truly a enclosed frame and there is no hole.
There is no hole in the 3 dimensions you can see. Perhaps the hole is where you are not looking? Gee, I hope this does not involve m-branes. All we need is string-theorists getting involved.
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#159 by oliverio on 14 Dec, 2015 18:28
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Yes. I think you and the rest of us are all on to some part of the theory but there's no way that we're going to actually solve the problem without more experimental results (nudge nudge hint hint [I kid, take your time ;p]).
If I had a stronger background in the required maths I would be trying to do some work figuring out some of the more burning questions, but I have to content myself with armchair analytics for now. Personally I think Bohmian mechanics could mathematically model an EMDrive just fine, but in that regard I really lack on the background maths, but without the maths, I am content to say that I think you're barking up the right tree.
