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#2040 by Rodal on 08 Oct, 2017 21:48
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The hypothesis put forward by the paper in question (which I don't support ... but for discussion's sake) proposes that the energy density location is critical for what they propose, not the electric field.Thank you
!
Would you mind trying different curves? e.g. top different from bottom or both the same but deeper... and the like ?
And with the bell shape please.Thank you
!
Would you mind trying different curves? e.g. top different from bottom or both the same but deeper... and the like ?
The Division Bell
So, it would be more clarifying for modelers to show contour plots of the total energy density, rather than showing contour plots of the electric field. (There are also magnetic fields involved) -
#2041 by WarpTech on 08 Oct, 2017 22:52
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First S11 measurements on the new frustum cavity.
I performed some first measurements on a frustum-shaped cavity I recently made (picture), with the Windfreak Technology SynthNV signal source/scalar network analyzer + a directional coupler.
As coupling loop I have made one according to Zhang et al., 2013 [1], see the attached picture (it is not easy, soldering a small wire to a 1-mm thick copper sheet. I needed my 300 W soldering iron to do that and it is rather clumsy). The remaining plastic cover has been removed from the copper plate, of course.
The results are not bad, I would say. Please see the attached example, two adjacent peaks at ~3036 MHz and ~3073 MHz.
The frustum (inner) dimensions are: BD = 202.0(5) mm, SD = 122.0(5) mm, h = 165(1) mm. Copper plate thickness: Big endplate and side wall = 0.5 mm, small endplate = 1 mm.
Coupling loop parameters: 1-mm wire, r = 11.0(5) mm, w = 14.0(5) mm, theta = ~45° (see the artcle by Zhang et al.).
More later.
Peter
[1] H. Zhang et al., Research on Novel Loop Antenna in Microwave Cavity Measurement of Permittivity, Int. J. of Information and Electronics Eng., Vol. 3, No. 4, July 2013, pp. 396-398.
A cheap torch lighter should cleanup that solder blob nicely.
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#2042 by TheTraveller on 08 Oct, 2017 23:21
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First S11 measurements on the new frustum cavity.
I performed some first measurements on a frustum-shaped cavity I recently made (picture), with the Windfreak Technology SynthNV signal source/scalar network analyzer + a directional coupler.
As coupling loop I have made one according to Zhang et al., 2013 [1], see the attached picture (it is not easy, soldering a small wire to a 1-mm thick copper sheet. I needed my 300 W soldering iron to do that and it is rather clumsy). The remaining plastic cover has been removed from the copper plate, of course.
The results are not bad, I would say. Please see the attached example, two adjacent peaks at ~3036 MHz and ~3073 MHz.
The frustum (inner) dimensions are: BD = 202.0(5) mm, SD = 122.0(5) mm, h = 165(1) mm. Copper plate thickness: Big endplate and side wall = 0.5 mm, small endplate = 1 mm.
Coupling loop parameters: 1-mm wire, r = 11.0(5) mm, w = 14.0(5) mm, theta = ~45° (see the artcle by Zhang et al.).
More later.
Peter
[1] H. Zhang et al., Research on Novel Loop Antenna in Microwave Cavity Measurement of Permittivity, Int. J. of Information and Electronics Eng., Vol. 3, No. 4, July 2013, pp. 396-398.
A cheap torch lighter should cleanup that solder blob nicely.
Better still, drill holes through the end plate and solder them on the outer surface. -
#2043 by Peter Lauwer on 08 Oct, 2017 23:23
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Better still, drill holes through the end plate and solder them on the outer surface.
Uhh, yes, that is a lot better. Also fixes the location a lot better. Thanks! -
#2044 by TheTraveller on 08 Oct, 2017 23:28
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Frustum resonance measurements
In my previous posting [https://forum.nasaspaceflight.com/index.php?topic=42978.msg1733603#msg1733603] I described the frustum and coupling loop.
During the measurements I discovered that using 0.5 mm copper sheet for the big diameter endplate was not such a good idea (though in doing so, I managed to keep the total weight below 1 kg). I first measured with the cavity in vertical position and discovered that it is very sensitive to putting some pressure on it, the endplate deforms easily and resonance peaks shift by the order of 1 MHz.
I then put the frustum in horizontal position (picture) and remeasured some resonances. Some of them I tabulate below, with estimated Q-values (determined from the -3 dB width):
3036.5 MHz Q = ~14k
3037.7 MHz Q = ~15k
3679.7 MHz Q = ~16k
The TE013 mode should be at ~3600 MHz for these dimensions.
I found that one very pronounced peak around 3490 MHz was not visible now (see picture Frustum1_3490MHz peak_no pressure.jpg). But, by putting some pressure on the big endplate, it appears again (see Frustum1_3490MHz peak_WITH pressure.jpg). This mode seems to be very sensitive to the right dimensions:
3489.15 MHz Q = ~10k Who can identify these modes?
I think about soldering a nut in the center of the big endplate and with a bridge etc. I can then use it to tune. Maybe pulling is better, as the big endplate gets a bit spherical then.
In the coming weeks, I hope to check these results with a professional network analyzer (VNA).
Hi Peter,
Those Qls look better. I get a max Qu of approx 45k, then derated by 25% to 34k and then assuming good coupler match, Ql = 17k.
BTW judging from the pictures, your side wall sheet is very shiny & smooth. Good sheet choice. BTW 1mm is the thinnest I would use for the flat end plates. Prefer 2mm. -
#2045 by sanman on 08 Oct, 2017 23:46
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From http://www.krynaglobal.com/product/eprop.html :
Hi - why is it important that reflection not occur? On the page you linked to, reflection results in delayed sound, and less pure musical notes. But in an EMdrive, reflection causes what? A less precise EM waveform?
Based on the Pilot Wave theory, is the goal to have as sharply defined an EM waveform as possible, biased in the direction of travel?
(Or as Dr Rodal said, "energy density". So what is an idealized energy density supposed to look like?)That trumpet shape looks like an Euler spiral in 3D. Parts of the curve are used to control jerk. It would be interesting to see how this relates from another perspective about how these shapes effect group velocity, acceleration, and jerk. I've been trying figure out how these two shapes (current EMdrive vs this shape) effect the jerking motion of a partial standing wave. I was thinking that an infinite jerk might be better to have than a linear change. I'm still undecided.
http://dynref.engr.illinois.edu/avt.html
https://en.m.wikipedia.org/wiki/Euler_spiral
http://iopscience.iop.org/article/10.1088/0143-0807/37/6/065008
https://en.wikipedia.org/wiki/Euler_spiral#Integrated_opticsQuoteIntegrated optics[edit]
Bends with continuously varying radius of curvature following the Euler spiral are also used to reduce losses in photonic integrated circuits, either in singlemode waveguides, to smoothen the abrupt change of curvature and coupling to radiation modes, or in multimode waveguides, in order to suppress coupling to higher order modes and ensure effective singlemode operation. A pioneering and very elegant application of the Euler spiral to waveguides had been made as early as 1957, with a hollow metal waveguide for microwaves. There the idea was to exploit the fact that a straight metal waveguide can be physically bent to naturally take a gradual bend shape resembling an Euler spiral.
So the curvature diffracts rather than reflects EM? And this diffraction... minimizes momentum transfer? So the idea is to maximize reflection at the big end, to maximize momentum transfer in the direction of travel - and meanwhile to minimize reflection and momentum transfer in the opposing direction.
Never knew that diffraction changes the nature of momentum transfer - didn't think that was possible. -
#2046 by spupeng7 on 09 Oct, 2017 01:36
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Bob,
Then your comments on "weight" were what you intended. Unfortunately they are a meaningless portion of your comment, not adding anything of import.
Bob,sanman,
Is that correct? When you say weight I assume you mean mass. Mass captured in a gravitational field does not gain additional mass merely as a result of the gravitational field itself, does it? Isn't more an increase in the density of the material, rather than gaining of additional mass?
gravity and inertia are inextricably linked by the principle of equivalence and by their common dependence upon the depth of the gravitational field within which their mechanism acts. By this I mean that gravitational and inertial mass are phenomena whose weight varies with depth into the gravitational field.
Isn't the accretion of mass more due to acceleration at relativistic speeds, or boson interactions enabling energy conversion to mass?
mass is conserved. Weight is dependent upon the local acceleration due to gravity, non?
Back 47 years ago as a college freshman, my physics professor was adamant: "Don't talk about weight. It's meaningless except when you step on a scale. Physics is all about mass, not weight."
with a known mass and that set of scales you can measure your local gravitational field. The point is that for both gravity and inertia, their F = ma reaction to an applied force varies with the strength of the local gravitational field from an external perspective. Your college prof. was free to limit his conceptual set but he would have advised you better to think on how the mechanism inertia occurs. -
#2047 by Mark7777777 on 09 Oct, 2017 02:56
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From http://www.krynaglobal.com/product/eprop.html :
Hi - why is it important that reflection not occur? On the page you linked to, reflection results in delayed sound, and less pure musical notes. But in an EMdrive, reflection causes what? A less precise EM waveform?
Based on the Pilot Wave theory, is the goal to have as sharply defined an EM waveform as possible, biased in the direction of travel?
(Or as Dr Rodal said, "energy density". So what is an idealized energy density supposed to look like?)That trumpet shape looks like an Euler spiral in 3D. Parts of the curve are used to control jerk. It would be interesting to see how this relates from another perspective about how these shapes effect group velocity, acceleration, and jerk. I've been trying figure out how these two shapes (current EMdrive vs this shape) effect the jerking motion of a partial standing wave. I was thinking that an infinite jerk might be better to have than a linear change. I'm still undecided.
http://dynref.engr.illinois.edu/avt.html
https://en.m.wikipedia.org/wiki/Euler_spiral
http://iopscience.iop.org/article/10.1088/0143-0807/37/6/065008
https://en.wikipedia.org/wiki/Euler_spiral#Integrated_opticsQuoteIntegrated optics[edit]
Bends with continuously varying radius of curvature following the Euler spiral are also used to reduce losses in photonic integrated circuits, either in singlemode waveguides, to smoothen the abrupt change of curvature and coupling to radiation modes, or in multimode waveguides, in order to suppress coupling to higher order modes and ensure effective singlemode operation. A pioneering and very elegant application of the Euler spiral to waveguides had been made as early as 1957, with a hollow metal waveguide for microwaves. There the idea was to exploit the fact that a straight metal waveguide can be physically bent to naturally take a gradual bend shape resembling an Euler spiral.
So the curvature diffracts rather than reflects EM? And this diffraction... minimizes momentum transfer? So the idea is to maximize reflection at the big end, to maximize momentum transfer in the direction of travel - and meanwhile to minimize reflection and momentum transfer in the opposing direction.
Never knew that diffraction changes the nature of momentum transfer - didn't think that was possible.
Hi - apologies but you might need a physicist to answer that question. I am an accountant who knows how to cut and paste
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#2048 by sanman on 09 Oct, 2017 06:08
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Hi - apologies but you might need a physicist to answer that question. I am an accountant who knows how to cut and paste
That's okay, I'm just a programmer who only knows how to wonder aloud
Since this Euler curve does diffraction instead of reflection, I'm just wondering why diffraction is better than reflection in this context.
The Wikipedia article says that it avoids "coupling with higher modes" - is this akin to reducing turbulence and promoting uniform laminar flow? -
#2049 by ThatOtherGuy on 09 Oct, 2017 07:02
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Thank you
!
Would you mind trying different curves? e.g. top different from bottom or both the same but deeper... and the like ?
And with the bell shape please.Thank you
!
Would you mind trying different curves? e.g. top different from bottom or both the same but deeper... and the like ?
The Division Bell
Thank you again, just a last request (if and when you'll have time), referring to this
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=42978.0;attach=1451657;image
could you try keeping the bottom (large plate) curve as is and changing the small plate one (e.g. start flat and increase the curvature in some steps) ?
[edit]
As for the sides shape, check out this http://vixra.org/pdf/1706.0283v1.pdf (fig. 3.2, page 11)
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#2050 by sanman on 09 Oct, 2017 08:34
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Sorry to be asking dumb questions again - but how are these plots indicative of any propulsive capability?
When I see the shaded zones inside the frustrum area, they seem to show concentrations of electric field strength - the reddish areas seem to be stronger than the bluish-greenish areas - but why is electric field strength indicative of propulsive capability?
And why do these resonant cavities have to be pumped with microwaves in particular? What's so special about microwaves? Why not UV-light instead, for example? Is it because the wavelength of microwaves makes them more convenient to work with?
Does the actual size of the frustrum matter, or just its ratios? -
#2051 by Peter Lauwer on 09 Oct, 2017 09:58
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...
3036.5 MHz Q = ~14k
3037.7 MHz Q = ~15k
3679.7 MHz Q = ~16k
Hi Peter,
Those Qls look better. I get a max Qu of approx 45k, then derated by 25% to 34k and then assuming good coupler match, Ql = 17k.
BTW judging from the pictures, your side wall sheet is very shiny & smooth. Good sheet choice. BTW 1mm is the thinnest I would use for the flat end plates. Prefer 2mm.
Hi Phil,
Indeed, the 0.5 mm endplate easily deforms. I will probably use 1 mm for the endplates of the next cavities. For the sidewall 0.5 is OK. -
#2052 by RonM on 09 Oct, 2017 13:18
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Sorry to be asking dumb questions again - but how are these plots indicative of any propulsive capability?
When I see the shaded zones inside the frustrum area, they seem to show concentrations of electric field strength - the reddish areas seem to be stronger than the bluish-greenish areas - but why is electric field strength indicative of propulsive capability?
Not a dumb question. If the EM drive produces thrust, it's a reasonable assumption it has a correlation to field strength. Without an accepted working theory, individuals are checking many possibilities.
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#2053 by Peter Lauwer on 09 Oct, 2017 13:44
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...
BTW judging from the pictures, your side wall sheet is very shiny & smooth. Good sheet choice.
If I have to make thermograms in order to be sure what mode is excited, I have to paint the outside of the cavity.
Bt it is probably also possible to use watercolour paint, so I can wash it off later.
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#2054 by tleach on 09 Oct, 2017 13:47
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From the article:
QuoteIf a pilot wave does explain the thrust behind the device, then it could also lead to a way to make the propulsion system even more powerful in future, and it's as simple as tweaking the shape.
"We have seen that the effect could be enhanced using a different shape for the frustum," said Castro. "In fact a trumpet exponential form is expected to increase the thrust."
What the heck is a trumpet exponential form? What does it look like?
Would it be where the frustum walls curve inward, like near the mouth of a trumpet?
Technically, the mouth of a trumpet is called the "bell" - an ironically appropriate name - and one with a better ring to it than "frustum".
Heh - so even a propellantless rocket still needs a bell, huh? Especially when it uses non-local hidden variables to satisfy Bell's theorem?
Hey Monomorphic, TheTraveler, or whoever - is it possible to run this shape through your analytical software and produce a graphical render from it?
Ha! Looks like my never completed "Riker Drive" may not have been as daft an idea as I thought!
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1438638#msg1438638 -
#2055 by kamill85 on 09 Oct, 2017 14:19
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On the subject of bells, "The Nazi-Bell" anyone?
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#2056 by LowerAtmosphere on 09 Oct, 2017 15:19
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Anybody have some hypotheses regarding hybrid modes or any new research regarding different waveforms to share? TM modes degenerating asymptotically into a TE mode might be worthwhile to investigate. It would be possible to achieve this either through modulating the input or using meta-materials with scattering. https://www.nature.com/nnano/journal/v12/n7/full/nnano.2017.50.html
Both could be at adjacent nearby resonant frequencies meaning the entire bandwidth between the two could be pumped in since we now know that intermediary waveforms will be attenuated or stored at the boundaries. Testing the transition and oscillation between poloidal E and toroidal E orientations would be interesting. It could be the interaction between modes which causes the effect after all... I was reading this paper randomly https://arxiv.org/pdf/physics/0307035.pdf when it struck me that perhaps we are oversimplifying by treating the wall as a uniform transmission medium, when it could be that it quasi-ionizes and forms discrete layers. If so there could be more mode mixing and further misalignment of toroidal vs poloidal E fields. Not only that, but it could even be possible that this charge separated layered ionization requires a threshold energy only reached in a certain part of the cavity, therefore creating a gradient with variable reflection coefficient along the wall! It could even be ionized by oxidation!
------------------------------
Here's some quick answers Sanman:Sorry to be asking dumb questions again - but how are these plots indicative of any propulsive capability?
Rhetorical hopefully?QuoteWhen I see the shaded zones inside the frustrum area, they seem to show concentrations of electric field strength - the reddish areas seem to be stronger than the bluish-greenish areas - but why is electric field strength indicative of propulsive capability?
It's related to Q and is critical for surpassing threshold levels in gravitational gradient/time lag based theories. The B component has been neglected slightly during the research, mainly because (opinion) TM has been less promising than TE. A popular explanation for this has to do with the direction in which you would want electron and ion pressure to equalize (small to big end), though there is an unresolved question as to whether TM is truly worse than TE. If new TM results equal those of TE then we know that the interaction of the B component with the endplates is the same as that of the E component.QuoteAnd why do these resonant cavities have to be pumped with microwaves in particular? What's so special about microwaves? Why not UV-light instead, for example? Is it because the wavelength of microwaves makes them more convenient to work with?
Microwaves have multiple unique and useful resonant freqs which are located nearby on the bandwidth. Microwave cavities are a useful size and magnetrons are common. Also, they have tolerable wall skin depths allowing for feasible DIY builds.QuoteDoes the actual size of the frustrum matter, or just its ratios?
Put roughly: everything is dependent on ratios of 1/2 waves. Of course the size matters.
FYI: here are two cutoff related papers surrounding the EM Drive and two educational sources regarding more general questions about resonating waveguides.
http://whites.sdsmt.edu/classes/ee481/notes/481Lecture10.pdf
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#2057 by Bob012345 on 09 Oct, 2017 16:56
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The hypothesis put forward by the paper in question (which I don't support ... but for discussion's sake) proposes that the energy density location is critical for what they propose, not the electric field.Thank you
!
Would you mind trying different curves? e.g. top different from bottom or both the same but deeper... and the like ?
And with the bell shape please.Thank you
!
Would you mind trying different curves? e.g. top different from bottom or both the same but deeper... and the like ?
The Division Bell
So, it would be more clarifying for modelers to show contour plots of the total energy density, rather than showing contour plots of the electric field. (There are also magnetic fields involved)
Also, short comments as to the significance of the plots would be most helpful. Thanks.
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#2058 by X_RaY on 09 Oct, 2017 18:22
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This is just bogus.
Of course reflection take place, either at the endplate, or if the throat is much smaller than the cutoff condition of a cylindrical waveguide --> at the sidewall!
Once again in the case of the EM-Drive we are talking about wavelengths of the order of the cavity structure itself.
The calculation example below clearly indicates standing waves. If there would be no reflection how can it be that a standing wave occurs?
Note the pdf file with an extended analysis done by Dr.Rodal in 2015.
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#2059 by Mulletron on 09 Oct, 2017 19:57
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This is just bogus. Of course reflection take place, either at the endplate, or if the throat is much smaller than the cutoff condition of a cylindrical waveguide --> at the sidewall!
Once again in the case of the EM-Drive we are talking about wavelengths of the order of the cavity structure itself.
The calculation example below clearly indicates standing waves. If there would be no reflection how can it be that a standing wave occurs?
Note the pdf file with an extended analysis done by Dr.Rodal in 2015.
There's clearly reflections. That doesn't mean that the reflections are equal from both ends.
!
Bt it is probably also possible to use watercolour paint, so I can wash it off later. 
Of course reflection take place, either at the endplate, or if the throat is much smaller than the cutoff condition of a cylindrical waveguide --> at the sidewall!