-
#2440 by TheTraveller on 15 May, 2016 16:39
-
Interesting new comment from Dr. Mike McCulloch on his EmDrive theory:
https://twitter.com/memcculloch/status/731774299380568064?s=01
Both Mike & Roger talk about the thrust being produced by larger EmWave momentum / mass at the big end and smaller EmWave monentum / mass at the small end with the EmDrive thrust being the result of gained momentum from the lost EmWave momentum / mass differential between the big & small ends.
-
#2441 by FattyLumpkin on 15 May, 2016 16:43
-
Monomorphic, were there any qualitative changes using concave and convex spherical caps on you wedge design. If you could post a side by side...thanks FL
-
#2442 by X_RaY on 15 May, 2016 16:44
-
For this mode yesFirst short try with the alternate geometry. Note the high E-field strength in the upper corner. Should be TE1..something.
High field strength in the upper corner is true for a few different modes while for other the fields remains almost zero in this section.
I still get cuttoff effects at 2.445 - 2.45Ghz when extending wedge to a point.
-
#2443 by Rodal on 15 May, 2016 16:50
-
-
#2444 by Rodal on 15 May, 2016 16:54
-
Interesting new comment from Dr. Mike McCulloch on his EmDrive theory:
https://twitter.com/memcculloch/status/731774299380568064?s=01
Both Mike & Roger talk about the thrust being produced by larger EmWave momentum / mass at the big end and smaller EmWave monentum / mass at the small end with the EmDrive thrust being the result of gained momentum from the lost EmWave momentum / mass differential between the big & small ends.
http://physicsfromtheedge.blogspot.com/2015/06/crit-of-shawyers-emdrive-theory.html -
#2445 by SeeShells on 15 May, 2016 17:10
-
Perforated walls? I said non-perforated walls, we are in agreement.
Very nice X)_ray. I like this thought. Maybe I should revisit the thinking in testing the extended split cone I did last year without the perforated walls? We didn't have FEKO then and were struggling to get even meep running.First short try with the alternate geometry. Note the high E-field strength in the upper corner. Should be TE1..something.
Very interesting !
We see that
1) The cavity still resonates? (what is the Q ?
)
2) the electromagnetic fields stop somewhere near/beyond the cut-off for an open waveguide
3) if you don't continue the taper to the apex, the energy density stops short of the small end
4) if you continue the taper to the apex, you all of a sudden get a concentration at the apex, at the apex (vertex) singularity that was examined by StrongGR (Marco Frasca) in his paper !
Dr. Rodal, the word should be "Fascinating"...
Back to work.
Shell
Added: The Q shouldn't be as interesting as the energy in the tiny captured mode.
The cone with a vertex is of interest because of what Dr. Marco Frasca (StrongGR) found in his paper: the general relativity effect takes place at the apex of the cone as a singularity (the effect increases as the vertex is approached).
It would be interesting to test on that account.
From an energy density point of view, the volume around the vertex is small, and there is a significant gap empty of energy density between the apex and the rest of the energy density where there is a bigger volume. So this is more a matter of intensity of the electromagnetic field. If the electric field gets very high there you may get electric breakdown of the air in that vicinity.
If comparing, tests may need to compare with similar materials and wall design: if the other tests do not have perforated walls, it may be better to compare without a perforated wall...
Hmmm I've thought about it before, to slide a plug in the tiny small end opening and of course seal it from microwave leaking, maybe a tunable dielectric extruded High-density polyethylene hexagon 1" shaft.
Right now it will be put on the to do list and I have a load of other work to get done first. -
#2446 by meberbs on 15 May, 2016 17:41
-
I was about to post how I assumed that the "higher inertial mass" near the large end in Dr. McCulloch's theory must be meant in a way that the total momentum in the photons is reduced when the mass increases.* This post from him confirms he understands the direction issue with Shawyer's theory, so he isn't likely to be making the same mistake, and comparisons of his McCulloch's increased mass to Shawyer's increased momentum are wrong.Interesting new comment from Dr. Mike McCulloch on his EmDrive theory:
https://twitter.com/memcculloch/status/731774299380568064?s=01
Both Mike & Roger talk about the thrust being produced by larger EmWave momentum / mass at the big end and smaller EmWave monentum / mass at the small end with the EmDrive thrust being the result of gained momentum from the lost EmWave momentum / mass differential between the big & small ends.
http://physicsfromtheedge.blogspot.com/2015/06/crit-of-shawyers-emdrive-theory.html
* I don't understand how inertial mass even makes sense when talking about photons, but McCulloch's theory has room with new physics, general relativity, and interactions between photons and other radiation that can presumably carry momentum away from the cavity. My limited understanding is that the increase in mass comes with transfer of momentum to Unruh waves, so that the momentum decreases despite the increase in mass. I could be off base, and there are other consistent interpretations I can think of. -
#2447 by VAXHeadroom on 15 May, 2016 17:51
-
I didn't take it to a point, but I did do a run a while back where I tapered the small end in both directions.
WOW. I really want to see what the magnetic fields look like in that.
That's it. I'm just going to have to buckle down and learn how to model geometries in MEEP...
-
#2448 by Rodal on 15 May, 2016 18:05
-
I was about to post how I assumed that the "higher inertial mass" near the large end in Dr. McCulloch's theory must be meant in a way that the total momentum in the photons is reduced when the mass increases.* This post from him confirms he understands the direction issue with Shawyer's theory, so he isn't likely to be making the same mistake, and comparisons of his McCulloch's increased mass to Shawyer's increased momentum are wrong.Interesting new comment from Dr. Mike McCulloch on his EmDrive theory:
https://twitter.com/memcculloch/status/731774299380568064?s=01
Both Mike & Roger talk about the thrust being produced by larger EmWave momentum / mass at the big end and smaller EmWave monentum / mass at the small end with the EmDrive thrust being the result of gained momentum from the lost EmWave momentum / mass differential between the big & small ends.
http://physicsfromtheedge.blogspot.com/2015/06/crit-of-shawyers-emdrive-theory.html
* I don't understand how inertial mass even makes sense when talking about photons, but McCulloch's theory has room with new physics, general relativity, and interactions between photons and other radiation that can presumably carry momentum away from the cavity. My limited understanding is that the increase in mass comes with transfer of momentum to Unruh waves, so that the momentum decreases despite the increase in mass. I could be off base, and there are other consistent interpretations I can think of.
In general relativity, gravity affects anything with momentum and energy. Photons do not have a rest-mass, but they do have momentum, and energy--and they are thus effected by gravity (photons cannot leave a black hole and their path in space is affected by the geodesics imposed by a massive object like the Sun).
TheTraveller posted McCulloch's twitter post (https://twitter.com/memcculloch/status/731774299380568064?s=01) with the diagram, but McCulloch's explanation is here: http://physicsfromtheedge.blogspot.com/2016/05/clearer-explanation-of-mihsc-emdrive.html
McCulloch writesQuoteIn the emdrive the magnetron puts microwaves into the cavity. MiHsC allows more Unruh waves (greater photon inertial mass) at the wide end, so as new microwave energy is put into the cavity its centre of mass is continually being shifted by MiHsC towards the wide end (see diagram). To conserve momentum the cavity has to move the other way towards the narrow end.
We can shift the emphasis from inertial mass of photons to their momentum and energy:
One could re-write this as that as new microwave energy is fed into the cavity the center of energy-momentum(energy and momentum are tied together in general relativity) is continually being shifted towards the big end, and to conserve momentum the cavity has to move the other way towards the narrow end. (*)
As to why the center of energy should be continually being shifted to the big end (greater photon momentum and photon energy at the wide end increasing continuously),(don't the cavity walls impose a closed system?)(**), and whether this can be due to Unruh waves (a quantum effect), I will leave that to McCulloch to explain
But clearly McCulloch thinks that for this to happen it requires that the notion of vacuum depends on the path of the observer through spacetime (the Unruh effect) which goes against Shawyer's explanation that "basic phsyics" of Newton, Maxwell and Special Relativity is all you need to explain the EM Drive.
___________
(*) If one is prepared to accept this, one must ask how long can this continue to go for, and whether there are diminishing returns to the effect: can the number of photons increase indefinitely inside the EM Drive cavity while indefinitely shifting the center of energy towards the big end? Or does this effect decay with time and run into a limit? Typical EM Drive tests showing force vs time (like NASA) have been run only for seconds, not hours at a time, and much less the days that it would require for the extrapolated trips to Mars etc. One would expect to be some limit related to the volume of an EM Drive: yet another reason arguing that "bigger is better" and that many small EM Drives would be a bad design, were this to be true...
(**) This again argues against using a power cord from a stationary source to conduct testing, as the center of energy in such a system is not in the moving platform and why conducting tests with batteries in the moving platform is a much better test for space flight applications, because you don't get to have a power cord from a stationary source for a spacecraft. -
#2449 by masterharper1082 on 15 May, 2016 18:34
-
It may be of value to significantly increase the cell density near the tip of the cone, to reduce the chance of the observed energy density being due to a numerical artifact.
For this mode yesFirst short try with the alternate geometry. Note the high E-field strength in the upper corner. Should be TE1..something.
High field strength in the upper corner is true for a few different modes while for other the fields remains almost zero in this section.
I still get cuttoff effects at 2.445 - 2.45Ghz when extending wedge to a point.
Sent from my SM-T710 using Tapatalk
-
#2450 by rfmwguy on 15 May, 2016 18:42
-
If I'm understanding prof mike's theory, I have a couple of questions...thinking of photonic radiation, is photon energy input exceeding the rate of dissipation? Is it possible new energy input never reaches disappation rate? Is the equilibrium of this energy resulting in motion because of CoM? Since this theory is pure momentum based, isn't the only way to ever validate the theory is with exactly what we are doing...torsion or balance beam? What other possible test to be conducted to test this theory?
-
#2451 by X_RaY on 15 May, 2016 19:30
-
After mesh refinement the high field strength remains in this area.
It may be of value to significantly increase the cell density near the tip of the cone, to reduce the chance of the observed energy density being due to a numerical artifact.
For this mode yesFirst short try with the alternate geometry. Note the high E-field strength in the upper corner. Should be TE1..something.
High field strength in the upper corner is true for a few different modes while for other the fields remains almost zero in this section.
I still get cuttoff effects at 2.445 - 2.45Ghz when extending wedge to a point.
Sent from my SM-T710 using Tapatalk
-
#2452 by Monomorphic on 15 May, 2016 20:16
-
After mesh refinement the high field strength remains in this area.
What are the dimensions on your geometry?
2 - 3Ghz 100 step sweep of the pointed wedge. I think I am seeing something similar to what X_Ray is seeing at 2.394Ghz (i'm using different dimensions).
I also ran a detailed sweep of that range, 2.3935Ghz - 2.3945Ghz. As far as off-centered modes go, that's about the best i've seen.
-
#2453 by X_RaY on 15 May, 2016 20:26
-
You are in a much better position since you have the full version fo feko. Thanks for spending the time for verification. Looks very niceAfter mesh refinement the high field strength remains in this area.
What are the dimensions on your geometry?
2 - 3Ghz 100 step sweep of the pointed wedge. I think I am seeing something similar to what X_Ray is seeing at 2.394Ghz (i'm using different dimensions).
snip..
I also ran a detailed sweep of that range, 2.3935Ghz - 2.3945Ghz. As far as off-centered modes go, that's about the best i've seen.
-
#2454 by Monomorphic on 15 May, 2016 20:33
-
Thanks for spending the time for verification. Looks very nice
Looks like our dims differ by only 5mm. But our electric dipole is in a different location and orientation. I always inject halfway up along the angled sidewalls.
Looks like you're still using a perfect conductor for the medium. I use copper at 0.05mm thickness.
NOTE: my units are in cm.
-
#2455 by X_RaY on 15 May, 2016 20:39
-
Yes I picked the dimensions of the square base you show yesterdayThanks for spending the time for verification. Looks very nice
Looks like our dims differ by only 5mm. But our electric dipole is in a different location and orientation. I always inject halfway up along the angled sidewalls.
Looks like you're still using a perfect conductor for the medium. I use copper at 0.05mm thickness.
Dipole coordinates are more or less random but the direction is not!
I focused to the E field into "b" direction because of the presence of the related modes in the upper corner are much more likely.
-
#2456 by Rodal on 15 May, 2016 20:56
-
After mesh refinement the high field strength remains in this area.
What are the dimensions on your geometry?
2 - 3Ghz 100 step sweep of the pointed wedge. I think I am seeing something similar to what X_Ray is seeing at 2.394Ghz (i'm using different dimensions).
I also ran a detailed sweep of that range, 2.3935Ghz - 2.3945Ghz. As far as off-centered modes go, that's about the best i've seen.
Wow
This is fascinating. Great job ! -
#2457 by rfmwguy on 15 May, 2016 21:22
-
So, I thought I would sweep the frustum BEFORE soldering closed...yeah I know, its not a good idea. So, looks like center is around 2.474 GHz, higher than the model, but within mag range. Return Loss 43dB which is outstanding without solder. If I measure Q from 3dB off best RL, it would be crazy high. Not going to go there yet, things will change after it gets soldered. Bottom line, almost ready to button up...
-
#2458 by Monomorphic on 15 May, 2016 21:45
-
Dipole coordinates are more or less random but the direction is not!
I focused to the E field into "b" direction because of the presence of the related modes in the upper corner are much more likely.
I oriented the electric dipole like yours, except injected midway up as before. I have never seen e-field strength this high (7500kV/m) without using a perfect conductor.
I'm positive there's a single node mode and am looking for it now.
-
#2459 by rq3 on 15 May, 2016 21:56
-
So, I thought I would sweep the frustum BEFORE soldering closed...yeah I know, its not a good idea. So, looks like center is around 2.474 GHz, higher than the model, but within mag range. Return Loss 43dB which is outstanding without solder. If I measure Q from 3dB off best RL, it would be crazy high. Not going to go there yet, things will change after it gets soldered. Bottom line, almost ready to button up...
You folks are all re-inventing resonant cavity filters. A return loss of 43 db is OK, but not great, and the Q should be well over 100,000 for a good design, even with a basic plated aluminum cavity. Again, once more. You can design a filter for an expected signal, or you can TUNE THE SOURCE for an expected Q. You folks seems to be slowly re-learning basic microwave engineering, and I'm glad to see that there is more talk of making the source track resonance, rather than trying to micro-machine a cavity to resonate with a crap source like a magnetron.
EW references to 20 Newtons per Kilowatt give me hope, but I'm not holding my breath because I don't want to turn blue.
EDIT: The s-parameter measurements you all make are only as good as the source and receiver you have on hand. Cheap USB instruments are severly limited in performance (simple physics). Phase noise, AM/PM conversion, lack of phase information ALL contribute to lack of useful information. Again, s-parameters are impedance specific, by definition. If the system is not normalized to a particular (generally 50 ohm) impedance, the results are useless. I have seen NO attempt by ANYONE on this forum to normalize their impedance. Any reference to injected power levels, or S-Parameters, are therefore worthless.
Note: A magnetron is most definitely NOT a 50 ohm source, nor is a microwave oven a 50 ohm load. The take away is that an Em drive cavity is not a 50 ohm load, and should never be modeled as such.
)
