-
#1380 by Rodal on 06 Jan, 2016 17:54
-
Hello Mr. Li. I have a quick question for you considering your experience with Lorentz testing. A conductive carbon-fiber tube of 53 inches length carries adjacent to it the 4 kVDC/480 mA anode voltage, ground and 3.3 VDC/10A filament current.
Finally, I share your current view about EMDrive recently read on reddit. I have got an interview about this matter and you can read it at (spanish) http://www.elespanol.com/ciencia/20151120/80741967_0.html.
Marco
That report wrote by Javier Yanes is by far the most comprehensive one among those that reported the October 31 Paul March NSF post. He cited our work and actually wrote to me for my opinions. None other reporters ever bothered to do that. Of course, Google can translate that web page into English,
https://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Fwww.elespanol.com%2Fciencia%2F20151120%2F80741967_0.html
Based on your previous testing, what would the horizontal and vertical Lorentz force be with the wires themselves then with close placement next to a carbon fiber rod?
This is the configuration that applies, per prior message from Li:
https://forum.nasaspaceflight.com/index.php?topic=39004.msg1470628#msg1470628
* rectangle parallel to the floor shows the electrical current path in the electrical wires
* a number of arrows going from North in the lower left hand corner to South in the upper right hand corner show the magnetic field
* the up and down bold arrows show the Lorentz force
Notice that the electrical path configuration needs to be in a HORIZONTAL plane (a plane parallel to the plane of the ground): for the Lorentz force to be such as to most effectively move the vertical balance ("teeter-totter").
Assuming that the teeter totter balance moves in a vertical plane perpendicular to the ground, the worst arrangement of the electrical wires (power-supply-grouding -> ground wire -> magnetron -> megnetron-filament-wires -> power-supply) would be if the wires are in a plane HORIZONTAL and parallel to the ground.Quotethe Lorentz force ... can also affect a see-saw. It all depends on how the current loop is positioned. Please refer to the attached pictures. The second one is when it will affect a see-saw. Remember that if you experiment with a magnetron, the current loop is: power-supply-grouding -> ground wire -> magnetron -> megnetron-filament-wires -> power-supply. This can be a big loop or a small loop, depending on how you position the wires.
I is the current in the wire
B is the magnetic field (indicated by a number of arrows going from North in the lower left hand corner to South in the upper right hand corner in Li's picture)
F is the Lorentz force (indicated by the up and down bold arrows in Li's picture)
https://en.wikipedia.org/wiki/Lorentz_force#Force_on_a_current-carrying_wire
So, if you must have an electrical path (power-supply-grouding -> ground wire -> magnetron -> megnetron-filament-wires -> power-supply) it better be in a VERTICAL PLANE, perpendicular to the floor and parallel to the plane of movement of the teeter-totter balance, to least affect the teeter-totter balance.
-
#1381 by Tellmeagain on 06 Jan, 2016 18:06
-
Hello Mr. Li. I have a quick question for you considering your experience with Lorentz testing. A conductive carbon-fiber tube of 53 inches length carries adjacent to it the 4 kVDC/480 mA anode voltage, ground and 3.3 VDC/10A filament current.
Based on your previous testing, what would the horizontal and vertical Lorentz force be with the wires themselves then with close placement next to a carbon fiber rod?
If the tube itself does not carry a current (please electrically isolate it from anything metal, including the ground wire the frustum and the magnetron; grounding of the rod can be done with single point grounding), then the Lorentz force is determined by the positioning of the ground wire and the two filament wires. If you can make sure the wires have good insulation, you can twist the ground wire together with the two filament wires to minimize the Lorentz force. I think if you do it right (if you show photos to me, I can tell) you can reach single digit micro Newtons or even sub micro Newtons. -
#1382 by rfmwguy on 06 Jan, 2016 18:12
-
Thanks Mr. Li, as I've said before, your test/paper is highly valuable as one of the only ones I could find that addressed possible error sources except for Dr Rodal.Hello Mr. Li. I have a quick question for you considering your experience with Lorentz testing. A conductive carbon-fiber tube of 53 inches length carries adjacent to it the 4 kVDC/480 mA anode voltage, ground and 3.3 VDC/10A filament current.
Based on your previous testing, what would the horizontal and vertical Lorentz force be with the wires themselves then with close placement next to a carbon fiber rod?
If the tube itself does not carry a current (please electrically isolate it from anything metal, including the ground wire the frustum and the magnetron; grounding of the rod can be done with single point grounding), then the Lorentz force is determined by the positioning of the ground wire and the two filament wires. If you can make sure the wires have good insulation, you can twist the ground wire together with the two filament wires to minimize the Lorentz force. I think if you do it right (if you show photos to me, I can tell) you can reach single digit micro Newtons or even sub micro Newtons.
I have better than a pic, here is a video of the test stand. I start out by talking about the new twisted power leads. I misspoke in the video and said the Clear wire for the filament was 500 kV rated, when in fact it is only 5 kV. Also the white cord twisted with it, has the 3 VDC and Ground TWISTED within its own insulation shroud. So to make it clear, there are 3 power leads. The clear and the white. The white has twisted & insulated wires within its own jacket. You should only need about 3 minutes of the start of this video I think. It was recorded on Sept 24th, 2015:
-
#1383 by Tellmeagain on 06 Jan, 2016 18:18
-
Notice electrical path configuration: for the Lorentz force to be such as to move the vertical balance ("teeter-totter"), the plane of the electrical path (power-supply-grouding -> ground wire -> magnetron -> megnetron-filament-wires -> power-supply) would need to be perpendicular to the plane (indicated by the down and up arrows) of movement of the teeter-totter
Keeping the circuit in the vertical plane will do the magic; but it is not easy to do so. Minimize the loop area is much easier. Twisting wires carrying currents of opposite directions can both minimize the loop area and cancel out much of the residue forces.
-
#1384 by Tellmeagain on 06 Jan, 2016 18:21
-
Thanks Mr. Li, as I've said before, your test/paper is highly valuable as one of the only ones I could find that addressed possible error sources except for Dr Rodal.
I have better than a pic, here is a video of the test stand. I start out by talking about the new twisted power leads. I misspoke in the video and said the Clear wire for the filament was 500 kV rated, when in fact it is only 5 kV. Also the white cord twisted with it, has the 3 VDC and Ground TWISTED within its own insulation shroud. So to make it clear, there are 3 power leads. The clear and the white. The white has twisted & insulated wires within its own jacket. You should only need about 3 minutes of the start of this video I think. It was recorded on Sept 24th, 2015:
Thank you for your compliments ! I will take a look tonight. (Not convenient now) -
#1385 by rfmwguy on 06 Jan, 2016 18:28
-
Thank you Mr. Li. There is only 1 small vertical drop of about 8 inches before it reaches the magnetron on the Frustum.Thanks Mr. Li, as I've said before, your test/paper is highly valuable as one of the only ones I could find that addressed possible error sources except for Dr Rodal.
I have better than a pic, here is a video of the test stand. I start out by talking about the new twisted power leads. I misspoke in the video and said the Clear wire for the filament was 500 kV rated, when in fact it is only 5 kV. Also the white cord twisted with it, has the 3 VDC and Ground TWISTED within its own insulation shroud. So to make it clear, there are 3 power leads. The clear and the white. The white has twisted & insulated wires within its own jacket. You should only need about 3 minutes of the start of this video I think. It was recorded on Sept 24th, 2015:
Thank you for your compliments ! I will take a look tonight. (Not convenient now) -
#1386 by SeeShells on 06 Jan, 2016 19:20
-
Notice electrical path configuration: for the Lorentz force to be such as to move the vertical balance ("teeter-totter"), the plane of the electrical path (power-supply-grouding -> ground wire -> magnetron -> megnetron-filament-wires -> power-supply) would need to be perpendicular to the plane (indicated by the down and up arrows) of movement of the teeter-totter
Keeping the circuit in the vertical plane will do the magic; but it is not easy to do so. Minimize the loop area is much easier. Twisting wires carrying currents of opposite directions can both minimize the loop area and cancel out much of the residue forces.
Top notch advice!
Shell -
#1387 by X_RaY on 06 Jan, 2016 19:54
-
That's why we are hereNotice electrical path configuration: for the Lorentz force to be such as to move the vertical balance ("teeter-totter"), the plane of the electrical path (power-supply-grouding -> ground wire -> magnetron -> megnetron-filament-wires -> power-supply) would need to be perpendicular to the plane (indicated by the down and up arrows) of movement of the teeter-totter
Keeping the circuit in the vertical plane will do the magic; but it is not easy to do so. Minimize the loop area is much easier. Twisting wires carrying currents of opposite directions can both minimize the loop area and cancel out much of the residue forces.
Top notch advice!
Shell
-
#1388 by RFPlumber on 06 Jan, 2016 19:55
-
Progress update. First light frustum mode testing.
Is there a possibility using this software to show how it looks in the complex plane (magnitude and phase or IQ)? It would be interesting because you could get a better feeling of what's wrong, either the resonance is huge overcoupled OR it's under coupled. Both possibilities could produce this tiny little peak in the magnitude plot.
...
I wish. Unfortunately the $240 scanning device ("Network Analyzer" ) is scalar only. This type of coupler has been researched and modelled though, and they say it typically requires those 2 loops to be up to twice the modelled diameter in order to provide the best match. Will need to tinker with sizes a little bit, and hopefully this will be enough.Progress update. First light frustum mode testing.....
Hi RfPlumber,
Could you please take a minute and explain your test setup and identify the black box?
Phil
Absolutely! The black box goes under the name "NWT-4000", it is a scalar "network analyzer". See my earlier post here http://forum.nasaspaceflight.com/index.php?topic=38577.msg1455540#msg1455540 with more description. The setup is just NA output into a directional coupler, the output of which then goes to the SMA frustum connector. The reflected power connector on the coupler goes back to NA input. The coupler used is -20 dBm, hence the default ~-20 dB line on the trace corresponding to reflected power being roughly 100% of forward.
That directional coupler appears to have a 0.8-0.9 dBm forward loss though, which is like 17%... So I am thinking the actual frustum powered test will need to go "blind" (that is, without any power monitoring) to avoid this power loss..Progress update. First light frustum mode testing.
...
Estimating Q factor for the 2.2 GHz mode. Comes at around 300 (see “Low-Q”). More frustration about how it would be useless to test with such a low Q even if I had power at this frequency.
...
One reason your Q is low is because of the huge seam where the cylinder joins the end plate. That you can see it clearly from this far away is bad news. This will kill any resonance.
Usually when making a cavity we used thick walls and tapped bolt holes. Then we secure with a pipe wrench and finally an air gun. Each hit on the air gun would make Q jump up. Thousands of Q is sensitive.
Please see this for reference
http://www.phys.aoyama.ac.jp/~w3-kitano/photo/cavity.jpg
This is very true, but apparently only for TM modes. And since the 2 modes I immediately noticed were both TM, this does explain the very low Q... But my understanding is that for TE modes the connection to end walls does not matter (SeeShells design has one of the 2 walls floating?), so hopefully the gaps will not be an impediment.
I certainly wouldn't mind to have a "real" cavity, but my gut feel is that it would cost on the order of $5K-$10K to make one, and... it would be rather heavy which is a killer for my pendulum-based test.
P.S. It would have been nice to be retired and being able to dedicate more time to this effort. Unfortunately I am not there yet.
-
#1389 by rfmwguy on 06 Jan, 2016 20:11
-
Well, have had some discussions with a local (musical instrument) brass-smith whose time is very limited. I am finding out all sorts of things about "seamless" frustum construction. Being stubborn enough to attempt things myself, I might do just that...borrow his shop late some night and learn a bit of the trade.
(snip)
I certainly wouldn't mind to have a "real" cavity, but my gut feel is that it would cost on the order of $5K-$10K to make one, and... it would be rather heavy which is a killer for my pendulum-based test.
(snip)
He says, compared to a tuba/baritone bell, this thing is a walk in the park...more later. -
#1390 by X_RaY on 06 Jan, 2016 20:17
-
To stay clear, for other than TE0np mode shapes there will be some current flow between end plate and side wall. TE01p is somewhat special in this context.Progress update. First light frustum mode testing.
Is there a possibility using this software to show how it looks in the complex plane (magnitude and phase or IQ)? It would be interesting because you could get a better feeling of what's wrong, either the resonance is huge overcoupled OR it's under coupled. Both possibilities could produce this tiny little peak in the magnitude plot.
...
I wish. Unfortunately the $240 scanning device ("Network Analyzer" ) is scalar only. This type of coupler has been researched and modelled though, and they say it typically requires those 2 loops to be up to twice the modelled diameter in order to provide the best match. Will need to tinker with sizes a little bit, and hopefully this will be enough.Progress update. First light frustum mode testing.....
Hi RfPlumber,
Could you please take a minute and explain your test setup and identify the black box?
Phil
Absolutely! The black box goes under the name "NWT-4000", it is a scalar "network analyzer". See my earlier post here http://forum.nasaspaceflight.com/index.php?topic=38577.msg1455540#msg1455540 with more description. The setup is just NA output into a directional coupler, the output of which then goes to the SMA frustum connector. The reflected power connector on the coupler goes back to NA input. The coupler used is -20 dBm, hence the default ~-20 dB line on the trace corresponding to reflected power being roughly 100% of forward.
That directional coupler appears to have a 0.8-0.9 dBm forward loss though, which is like 17%... So I am thinking the actual frustum powered test will need to go "blind" (that is, without any power monitoring) to avoid this power loss..Progress update. First light frustum mode testing.
...
Estimating Q factor for the 2.2 GHz mode. Comes at around 300 (see “Low-Q”). More frustration about how it would be useless to test with such a low Q even if I had power at this frequency.
...
One reason your Q is low is because of the huge seam where the cylinder joins the end plate. That you can see it clearly from this far away is bad news. This will kill any resonance.
Usually when making a cavity we used thick walls and tapped bolt holes. Then we secure with a pipe wrench and finally an air gun. Each hit on the air gun would make Q jump up. Thousands of Q is sensitive.
Please see this for reference
http://www.phys.aoyama.ac.jp/~w3-kitano/photo/cavity.jpg
This is very true, but apparently only for TM modes. And since the 2 modes I immediately noticed were both TM, this does explain the very low Q... But my understanding is that for TE modes the connection to end walls does not matter (SeeShells design has one of the 2 walls floating?), so hopefully the gaps will not be an impediment.
I certainly wouldn't mind to have a "real" cavity, but my gut feel is that it would cost on the order of $5K-$10K to make one, and... it would be rather heavy which is a killer for my pendulum-based test.
P.S. It would have been nice to be retired and being able to dedicate more time to this effort. Unfortunately I am not there yet.
It's not simply a question of TE or TM, it's a question of the mode shape at all.
Current flow between end plate and side wall is true for most TE and TM modes, therefore it is a good choice to get good galvanic contact if one focus on other than this special mode shape.
-
#1391 by Rodal on 06 Jan, 2016 22:13
-
My simplistic explanation of the phenomenon:
To summarize my previous notes in https://forum.nasaspaceflight.com/index.php?topic=39004.msg1470818#msg1470818 (I look forward to other's comments):
If, in the field equations
we keep in mind that the energy-momentum-tensor is composed of densities. (energy densities, energy flow density, strain density ) not absolute values.
and if we keep in mind that the classical expression for energy density of EM fields wem = 1/(8*pi)*( E˛ + B˛)
is only an approximation for fields much weaker than the critical Schwinger field limit.
In the more exact model (Euler-Heisenberg energy density): There are terms proportional to Eł, Bł and higher.
EH model is without doubt correct, it is experimentally verified in numerous experiments. (photon splitting in magnetic fields etc.)
Now at the smaller end surface there are: proportionally stronger fields but overproportionally (more than squared) larger energy densities -> overproportionally larger space-time curvature compared to the large end surface. As a result the frustrum could "fall" towards the smaller end.
1) An extremely strong electrostatic field can produce, out of the vacuum, real electron-positron pairs. However, the magnitude of the required field is astronomically large, much larger than the fields in the EM Drive experiments.
2) The virtual creation of electron-positron pairs results in a coupling of the electromagnetic field with itself: a so-called self-interaction. For extremely strong but slowly varying electromagnetic fields the self-interaction energy can be calculated as done by Euler (first with Kockler and then with Heissenberg), resulting in a nonlinear modification of Quantum Mechanics. (https://en.wikipedia.org/wiki/Euler%E2%80%93Heisenberg_Lagrangian)
3) Such nonlinear Quantum Mechanics (as described by Euler-Heissenberg) is associated with various Quantum Electro Dynamic phenomena:
a) (light with light) photon-photon scattering ( https://en.wikipedia.org/wiki/Two-photon_physics ) (first observed in 1997: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.79.1626)
b) "photon splitting" http://physics.aps.org/story/v10/st3 (first measured in strong magnetic field in 2002: Sh. Zh. Akhmadaliev et al, “ Experimental investigation of high-energy photon splitting in atomic fields”, Phys. Rev. Lett. 89, 061802 (2002) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.89.061802)
c) vacuum polarization (https://en.wikipedia.org/wiki/Vacuum_polarization ).Vacuum polarization referred to as the one loop contribution occurs with electron-positron pairs or with quarks. With electron-positron pairs it was first observed in the 1940s but also recently observed in 1997 using the TRISTAN particle accelerator in Japan. Experiment PVLAS ( http://pvlas.ts.infn.it/ ) is searching for vacuum polarization of laser beams crossing magnetic fields to detect effects from axion dark matter. No signal has been found and searches continue.
d) vacuum birefringence: as Maxwell's equations become nonlinear if the effect of virtual electron-positron pair creation is included, the vacuum, then behaves like a polarizable continuum, shown to exhibit the phenomenon of birefringence.: being studied by experiment OSQAR at CERN ( http://osqar.web.cern.ch/osqar/ )
e) effect on an external field of the modification of the vacuum electromagnetic field by parallel mirrors
4) Because of the extremely high electromagnetic field strengths required for the above-mentioned phenomena, Bialynicka-Birula wrote in 1970 that there was no prospect of observing them. Yet, light by light scattering was first observed in 1997 and "photon splitting" was first measured in strong magnetic field in 2002. Certainly, the field strengths required for these nonlinear Quantum Mechanics effects to be present are orders of magnitude greater than the electromagnetic field strengths present in EM Drive experiments. The physical effects at the level of the EM Drive electromagnetic field strengths of this nonlinear Quantum Mechanics are too small to be measurable. At the level of the EM Drive electromagnetic field strength, linear Quantum Mechanics should be quite applicable.
5) According to General Relativity, something interesting happens near the vertex of the EM Drive cone, as shown by Marco Frasca. Unfortunately none of the EM Drive researchers have tested geometries that are even close to the vertex of the cone. Instead they all have followed Shawyer's prescription forbidding them from having a small diameter of the truncated cone to be smaller than the cut-off frequency of a cylindrical waveguide having the same diameter. Therefore, I do not see how the nonlinear Quantum Mechanics of Euler-Heissenberg could be used to explain anomalous forces in the present EM Drive experiments.
-
#1392 by rfmwguy on 06 Jan, 2016 23:17
-
Dr rodal, I will speak to the conical shape in less than elegant but more of a hands-on type, which is where I am most experienced. If you look at the cavity as a coaxial transmission device with an air or vacuum dielectric, the fields flow along the transmission line until they encounter resistance.
In this case, an extreme mismatch of impedance caused by a narrowing cone. Rf fields beyond that point are there but highly attenuated...that's what a filter does, extreme return loss to inhibit rf...a bandpass filter.
I surmise a conical frustum would not allow energy past a certain diameter or cutoff...an I saw that exact thing recently.
Remember me using that baritone bell? I stuffed the narrow end with a. copper taped plug over foam. I moved the plug up and down to try and tune it...nothing. I took the plug out...no change on vna.
Granted, it was low power, but I observed no vna tuning effect in the small end of the bell. Big end? Yes, I hammered it slightly narrower and upped the resonance freq.
Given enough power and source isolation to reflected power, I believe you might be able to drive rf energy down to a point...that might be very interesting...my guess is power needed is multiple dozens of kW -
#1393 by Tellmeagain on 07 Jan, 2016 00:03
-
Thank you Mr. Li. There is only 1 small vertical drop of about 8 inches before it reaches the magnetron on the Frustum.
Hi rfmwguy, I watched your video. I think generally it is OK regarding Lorentz force. However, you'd better make the following changes, 1. Straight your lines so that red and green wires labeled in the first picture are arranged as in the second picture to minimize the loop area. 2. For safety's sake, you'd better let the two filament wires to go through one tube and let the ground line go through the other. This is because the voltage difference between the two filament wires is about a few volts, while the voltage difference between the filament wire and the ground wire is around 5000V. 3. You'd better move your microwave power supply away from the frustum. This is because the magnetron has magnets, which may interfere with the DC in your power supply and power supply wires. I do not know how big it is (maybe very small) but it does not hurt to make some extra effort. 4. I think it will be ideal if you can modify your seesaw into a torsion balance. But that is only my opinion. 5. If you have conductive beam, make sure the circuit does not contact the beam electrically at more than 1 point. Thanks!
-
#1394 by rfmwguy on 07 Jan, 2016 01:01
-
Well said Mr Li. I thank you for suggesting improvements for my next round of tests! This is good cooperation between people with a wide variety of experiences. Your experiment and paper shows you have serious interest is resolving any measurement errors and are willing to share! - DaveThank you Mr. Li. There is only 1 small vertical drop of about 8 inches before it reaches the magnetron on the Frustum.
Hi rfmwguy, I watched your video. I think generally it is OK regarding Lorentz force. However, you'd better make the following changes, 1. Straight your lines so that red and green wires labeled in the first picture are arranged as in the second picture to minimize the loop area. 2. For safety's sake, you'd better let the two filament wires to go through one tube and let the ground line go through the other. This is because the voltage difference between the two filament wires is about a few volts, while the voltage difference between the filament wire and the ground wire is around 5000V. 3. You'd better move your microwave power supply away from the frustum. This is because the magnetron has magnets, which may interfere with the DC in your power supply and power supply wires. I do not know how big it is (maybe very small) but it does not hurt to make some extra effort. 4. I think it will be ideal if you can modify your seesaw into a torsion balance. But that is only my opinion. 5. If you have conductive beam, make sure the circuit does not contact the beam electrically at more than 1 point. Thanks! -
#1395 by RFPlumber on 07 Jan, 2016 05:39
-
Ok, the dual loop coupler has been tuned, and the result appears to be good enough (S11 of approx. -15 dBm, that is, 97% of forward power should be going into the cavity). A few frequency scans attached for entertainment:
Loop_11mm – loops 11 mm in diameter, 22 mm apart. Visible improvement in S11 over the original -2 dBm ripple with 8 mm loops.
Loop_16mm - loops 16 mm in diameter, 32 mm apart. Appears over-coupled.
Loop_13mm_Qcalc - loops 13 mm in diameter, 26 mm apart. This is what I am going to use. Q factor calculated at -3dBm comes to about 3100.
Loop_13mm_WideScan – wider freq scan with the same 13 mm loops. Shows both TE012 and TE013, as well as some TM / mixed mode at #2 cursor (all modes are per COMSOL simulation).
It is likely possible to further improve matching at TE012 with a slightly different loop size, but it is hard to make those dual loop couplers with better than a couple of mm tolerance. So I will go with the 13mm one.
There is one last thing I will need to do before placing this frustum on the pendulum, and it is to verify that it can hold 30W of input RF at resonance for at least 20+ seconds (without expanding out of resonance). Once confirmed, it will then be tested. If there is any truth to that number of 450 mN/ kW per 100,000 of (unloaded) Q, this cavity should be producing 450 mN * (30W / 1000W) * (2 * 3000 Q / 100,000 Q) ~= 800 uN. This much force would be trivial to detect with the pendulum. I have my doubts that this will happen though, but we shall see…
-
#1396 by mwvp on 07 Jan, 2016 06:16
-
Happy New Year all!
Its disappointing the salient properties, dispersion and dissipation, are not examined while arcane physics involving the diminutive G constant is! I've found an interesting paper I'm slogging through:
http://arxiv.org/abs/1005.5467v1
Sorry for the haste & sparse notes, it seems apt to comment, such as it is.Quote"Doppler shifts may become large in a dispersive medium as the velocity of the Doppler shifting surface approaches the group velocity.
...
In vacuum, ng = 1, and n = 1, meaning that a .01% increase
in frequency leads to roughly a .01% decrease in wavelength. In a moderately slow
medium, ng might be 100 while n remains at approximately 1. In this case a .01%
increase in frequency leads to roughly a 1% decrease in wavelength. Thus, with no
change to the spatial resolution of an interferometer, its spectral resolution may be
enhanced 100-fold.
...
electric permittivity
and the magnetic permeability in the slow light medium are very close to their
vacuum values for fields near EIT resonance. Therefore the values of the squared
electric and magnetic fields remain continuous across the boundary even as the pulse
is compressed. The total field energy associated with the pulse then scales with the
group velocity. When that velocity is slowed, very little of the original pulse energy
remains in the field. Rather, it is coherently stored in the slow-light medium.
...
When the effects of dispersion are included, neither the Abraham nor the Minkowski
expression for electromagnetic momentum in a dielectric medium gives the correct
recoil momentum for absorbers or emitters of radiation. The total momentum den-
sity associated with a field in a dielectric medium has three contributions:
(i) the Abraham momentum density of the field,
(ii) the momentum density associated with the Abraham force, and
(iii) a momentum density arising from the dispersive part of the response of the medium to the field,"
Bradshaw is discussing atoms slowing light, not our context. What I find interesting is time-domain pulse compression/expansion, Q multiplication (spacial resolution) and doppler shift. He goes on to discuss the recoil momentum of a dielectric block. Since waveguide EM momentum isn't being stored in atomic polarization, where is it? I'll assume the near-field? (I'll have to dig up the papers on the mass of the near-field/evanescence, and a different impedance than space.) Much may be applicable and relevant.
Shawyer discusses the importance of tuning on the brink of cut-off, Q, and doppler shift as the mechanism of CoE/CoM (motor/generator mode), although with abysmally-sparse theory. This gets to the supporting theory.
Considering the physical frustrum anisotropy, doppler-shifting and the obvious anisotropy of dissipation in the EW frustrum as evidenced by the Comsol and IR plots, then inertial ratcheting under vibration/acceleration follows. Like the BAE photon rocket, except it's compact, and discriminates reverse-acceleration by creating friction against the vacuum and radiating the heat but with half the efficiency.
Surely it's possible to model the system, and develop a signal analysis protocol, in a dynamic (motion with doppler) context.
A toy frustrum, powered with milliwatts of RF might well exhibit negative inertial resistance (which would appear as microphonics), and inertial ratcheting appearing as harmonic distortion. Possibly parametric instability.
Another interesting find, Cavity Optomechanics: http://arxiv.org/abs/1303.0733
-
#1397 by TheTraveller on 07 Jan, 2016 06:34
-
JFYI, Attached are COMSOL simulations for the frustum (with coax coupling) I am going to build. It is now time for some sheet metal cutting and torch soldering... And then there will be the moment of truth.
D_big: 264 mm
D_small: 158 mm
L_center: 204 mm
TE012 freq: 2,323,xxx kHz COMSOL (vs. 2,402,xxx spreadsheet)
Hi RfPlumber,
Thanks for the data on your test setup and VERY LOW COST quasi VNA. Have ordered that unit as I have built a Forward & Reflected power monitor that should have almost zero insertion loss and should work well with that unit. If it works as expected, using it and this unit will make really low cost frustum resonance monitoring a reality. By low cost I mean like around $150.
Can you please confirm the frustum built length is 204 mm and not 240 mm?
Do you have a link for your 30W Rf amp and can the freq gen you have drive it enough power to obtain the 30Ws at output?
Based on the frustum length being 240 mm (TE012 resonance at 2.324 GHz), the prediction is 4mN at unloaded Q of 50k (25k loaded Q) and 30W Rf forward power.
BTW what is the bandwidth and loaded Q if you measure 3dB up from the max rtn loss dB point, instead of 3dB down from the reference level.
Roger's Force equation works from unloaded Q, being twice the loaded Q, measured 3dB up from the max rtn loss dB point on a S11 VNA scan. This is how you measure power bandwidth as the max power xfer level becomes 0dB and you measure the point where the power xfer is 3dB down from the peak power xfer dB level.
Not trying to trigger an argument here. Just stating how Roger's Force equation works and what Q measurement technique it is based on.
Good luck with your tests.
Phil
-
#1398 by MathewOrman on 07 Jan, 2016 13:22
-
Just like this:The physics of the EM drive is well defined but unfortunately it is not what the inventor claims.
Also the inventor's video demo on Youtube shows EM drive rotating in the opposite direction than what his theory claim.
The EmDrives moves / generates Force toward the small end, as it does in the video. -
#1399 by Rodal on 07 Jan, 2016 13:30
-
I recall that some time ago someone claimed that Shawyer stated that his experiments show no force unless some amount of forced external vibration was imparted in the experiments (or similar words to that effect). Going by memory, these are some of the messages I found by a rapid search:
Just like this:The physics of the EM drive is well defined but unfortunately it is not what the inventor claims.
Also the inventor's video demo on Youtube shows EM drive rotating in the opposite direction than what his theory claim.
The EmDrives moves / generates Force toward the small end, as it does in the video.
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409361#msg1409361
https://forum.nasaspaceflight.com/index.php?topic=37642.msg1397204#msg1397204
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1397386#msg1397386
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1397370#msg1397370
https://forum.nasaspaceflight.com/index.php?topic=37642.msg1401205#msg1401205
It was claimed that forced external vibration " enables switch from IDLE to MOTOR mode" of the EM Drive.
When asked what frequency and amplitude of vibration was "necessary", there was no reply that I recall. I have not heard discussion of this need to impose vibration recently.
What is the latest information in this regard?
Is the need for vibration still being claimed?
Has this claim for need of vibration been abandoned?
What is the view of people doing Do It Yourself experiments in regards to this claim for the need of vibrations?
Are they including forced vibration in their experiments?
If this claim has been abandoned, it would be good to put this matter to a close, for clarity purposes.
