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#3120 by Flyby on 22 Nov, 2016 21:15
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I was about to say that TT only reacted upon my post, but you've already noticed, i see......I believe it unfair to insist on a ridged mathematical definition of words like "complex" when the discussion moves back and forth between mathematical models and practical engineering....
If you look back at what TheTraveller was responding to, was this:...For me it is clear the the mean difficulty of building an EMdrive (or even establishing that the effect is real) lays in the very fact it is a "complex system"
https://en.wikipedia.org/wiki/Complex_system
If you look at the characteristics of complex systems you'll see that many of those have been brought up on this forum.
...
Which cites precisely the same article that I cited ( http://forum.nasaspaceflight.com/index.php?topic=40959.msg1612417#msg1612417 ).
It is fair then to use the definition of complex system in the cited article, which is what I did.
Which is the definition of complex system, as understood in Physics, Mathematics, Biology, Aerospace Engineering, Mechanical Engineering, Electrical Engineering, etc..
While excessive rigor may lead to rigor mortis, lack of sufficient rigor (the definition in the cited article) may lead to confusion
. Hopefully we may reach a happy medium steering away from either end
If by "complex" it is meant mysterious as in "we have no agreed model as to why something apparently non-complex as a copper cavity may self-accelerate" then we agree
By times , this forum is really intimidating for people (like me) that do not have a professional scientific education. I can no longer count the times I've deleted posts before even posting them, mainly due to the personal question what I could possibly add to a discussion ?
Compared to people like you, Dr Rodal, or Todd Desiato, Notsosureofit or so many others inhere, I realize more then enough how much I'm lagging on indepth knowledge...
yet.. the EMdrive subject has captivated my interest, so i can't help wondering and researching about it, leaning on the solid but basic science training i had, many years ago.
I do realize that I'm hindered by not speaking the "scientific/mathematical language", need to get a point or an observation across...It is a handicap...
what I mean with "complex" is that there are a considerable number (yet to define list) of parameters that make up the EMdrive effect. These parameters interact in such a complex matter that it becomes very hard to identify what parameter(s) contribute to an observable result.
One of the things I started thinking and researching about is what reflection actually is. What happens when an EMwave hits a copper lattice ? As Todd identified some pages ago, the question WHY keeps haunting me...
with the limited knowledge i have, it is impossible for me to identify if I'm right or wrong, but here is a first observation of mine :
Remembering my classes in optics I always considered the amount of reflection being a linear relation to the incident angle. However , a few months ago (while working on a 3d rendering fresnel material) I realized that a reflected wave has not a linear relation to the "cos" of the incident angle, but behave slightly differently the bigger the angle between surface normal and ray gets...
The material is copper, the frequency is not correct because I could not find an exact match. I choose this one because it illustrates the point I would like to make very well. We all know the real world effect when looking at a metal surface at a very shallow angle : the reflections are getting intenser....
Going back to the frustum, knowing that waves going back and forth between both end plates to create standing waves, I can't help noticing that for waves going from small to big end the angle of incidence to the normal is larger then for waves coming from the other side. If the reflected ray was truly linear, that difference would be compensated by (surface big end - surface small end)/2. Everything cancels out, net result is zero...
However, the relation of angle and reflectance is NOT linear, which means, if i get that correct, that for waves going from small to big end have a higher degree of reflectance...
More over, these graphs change appearance with shifting frequency. so any small change in frequency changes the non linear look of the graph...
So my question to those who know more then me : what is the relation between reflectance and momentum ?
Because, if momentum is in a linear relation to the reflectance, that on it self is not linear, it would mean that momentum is not linear to the cos of the incidence angle....
At 90°, the momentum should be 0, no?
This is one of the (unanswered) questions to why i consider this a "complex system". If momentum changes in a non linear way, depending on the "incidence angle" and on "frequency change" then it is damn hard to track the exact values...
Well, as I have no reputation to defend and no honor to fight for, I thought I might get some flak instead and position me in the line of fire...
I've probably made a wrong assumption somewhere, but my question is genuine and honest.
edit:
Corrected image on reflectance, as our current assumptions require a constant reflection. It is the incident angle that changes the values.
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#3121 by CraigPichach on 22 Nov, 2016 21:19
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Paul March,
In one of your EagleWorks slides you had a proposal to use an L-3 communications industrial magnetron to perform a 100kW test into a frustum. Based on this actually talked to L-3 communications industrial magnetron division and was surprised they had no idea what I was talking about but were interested in the magnetron application. I sent them various information pertaining to the EM Drive/Q-Thruster i.e. firing the RF at resonance freq in a copper frustum. They indicated they had a pre-existing test set up that could easily do 930MHz, 100kW and could even do >1MW micropulses with solenoid, waveguide launcher and isolator (waterload to absorb RF energy) and sent various pictures/diagrams. Concept was to attach a "thruster" after the isolator but aim to have an impedance match / Z-match choke hole with a Faraday cage around the whole thing. We came up with the idea of firing a water cooled thruster into the ground and seeing if we could make the scale weight increase. Frequency had to be 930MHz, various COMSOL runs were done at 930MHz, it has been a while but I believe the first run was going to be TM010. L-3 was to send me dimensions (I used the Travellers spreadsheet to come up with some rough dimensions to confirm) but then they stopped emailing me after sending pictures, but not dimensions of the COMSOL runs. Do you know if NASA is now working with them to do the test (often asked them to talk to EW if possible)? I don't want to bug L-3 but sad that after all that excitement it seemed to come to a halt (had some local fab shops interested in doing the copper frustrum and paying for the experiment, was going to have my younger brother do this as his final electrical engineering project). Don't care either way, but I feel that we had a great experiment lined up and would love to know if anyone is still pushing this!?? I was going to put some coin into using local fab shops to come up with the frustrum and cooling mechanism and rent that setup. Yes the experience was not going to be in a vacuum but the hope was that we could generate some data above experimental measurement error tolerances. Regardless, just want to see if happen (and know what happens!). -
#3122 by Monomorphic on 22 Nov, 2016 21:23
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The contours on the small end are clearly not fine enough, the contours are not even uniformly symmetric around the axis of axysymmetry.
One must be very careful with these numerical solutions, particularly when using "automatic meshing".
These FEKO results shown for TM212 are not as good as the COMSOL FEA analysis done at NASA.
I do not think that COMSOL is all that great either (I particularly dislike the fact that COMSOL does not appear to have a theoretical manual, it just has users manuals), it is not on the same class as ABAQUS or ADINA.
These meshes are too coarse, the contour boundaries are not smooth, being polygonal, and showing some artifacts, particularly when looking at details of the solution... The higher the m, n and p, the finer mesh one needs.
The asymmetry in the small end is because I have modeled and am simulating the 13.5mm loop antenna along the side wall. Adding it to the simulation decreases volume thereby increasing the resonant frequency so that what COMSOL returned at 1.9371Ghz will be different from what FEKO returns. I expect perfect resonance is a little higher than 1.9371Ghz in FEKO as the antenna is taken into consideration. I do not believe NASA modeled the antenna in its COMSOL simulations. If I switched to a generic waveguide excitation, the resonant patterns would perfectly match. In this way, modeling the antenna shape, size, and location along with the frustum is a more accurate representation of the system than just using a waveguide excitation centered on one of the endplates. -
#3123 by Rodal on 22 Nov, 2016 21:33
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......questions to why i consider this a "complex system". If momentum changes in a non linear way, depending on the "incidence angle" and on "frequency change" then it is damn hard to track the exact values...
OK, yes complex in that sense, there are yet unresolved aspects about this for example the Abraham/Minkowski paradox: https://en.wikipedia.org/wiki/Abraham%E2%80%93Minkowski_controversy. Regardless of my opinion about this controversy, the fact that this is still a controversy where different scientists still disagree, shows the complexity of electromagnetic waves, photons and material interaction. Copper is not a dielectric, which is the focus of this controversy, but the issue of precisely the nature of the electromagnetic momentum within the skin depth of copper (or the London penetration depth in a superconductor) is complex (in that sense ).
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#3124 by Star-Drive on 22 Nov, 2016 21:48
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To cut to the chase:
However there IS still a real impulse force being generated in these in-vacuum runs that is riding on all the thermally induced TP cg shifts.
How do we know any of this? Why should we trust any of the thrust numbers in the paper?
as58:
Short answer, you don't have to believe anything we reported. However if you look at the body of evidence accumulating from all sources including the first EW AIAA paper and the EW Dec 2014 in-vacuum testing I reported here at NSF.com during the spring of 2015, I think most folks would consider that there is a lot of smoke surrounding this phenomenon. And where there is smoke, hopefully their is a fire to engineer. My next goal is to build another 2.45 GHz copper frustum EM-drive, but this time with spherical endcaps and much better drive antenna frequency tuning controls to see if I can evoke the EM-drive fire in a much more convincing way than we have to date. What do you plan to do?
Best, Paul M. -
#3125 by Star-Drive on 22 Nov, 2016 22:09
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Paul March,
In one of your EagleWorks slides you had a proposal to use an L-3 communications industrial magnetron to perform a 100kW test into a frustum. Based on this actually talked to L-3 communications industrial magnetron division and was surprised they had no idea what I was talking about but were interested in the magnetron application. I sent them various information pertaining to the EM Drive/Q-Thruster i.e. firing the RF at resonance freq in a copper frustum. They indicated they had a pre-existing test set up that could easily do 930MHz, 100kW and could even do >1MW micropulses with solenoid, waveguide launcher and isolator (waterload to absorb RF energy) and sent various pictures/diagrams. Concept was to attach a "thruster" after the isolator but aim to have an impedance match / Z-match choke hole with a Faraday cage around the whole thing. We came up with the idea of firing a water cooled thruster into the ground and seeing if we could make the scale weight increase. Frequency had to be 930MHz, various COMSOL runs were done at 930MHz, it has been a while but I believe the first run was going to be TM010. L-3 was to send me dimensions (I used the Travellers spreadsheet to come up with some rough dimensions to confirm) but then they stopped emailing me after sending pictures, but not dimensions of the COMSOL runs. Do you know if NASA is now working with them to do the test (often asked them to talk to EW if possible)? I don't want to bug L-3 but sad that after all that excitement it seemed to come to a halt (had some local fab shops interested in doing the copper frustrum and paying for the experiment, was going to have my younger brother do this as his final electrical engineering project). Don't care either way, but I feel that we had a great experiment lined up and would love to know if anyone is still pushing this!?? I was going to put some coin into using local fab shops to come up with the frustrum and cooling mechanism and rent that setup. Yes the experience was not going to be in a vacuum but the hope was that we could generate some data above experimental measurement error tolerances. Regardless, just want to see if happen (and know what happens!).
Craig:
I'm impressed! However if L-3 Com approached Dr.. White about this 100kW Q-Thruster topic, he never told me about it. However I hope you are right in that someone has picked up this 100kW ball that could have produced over a 1,200 Newtons running at its TM010, 929 MHz resonance mode of the EW copper frustum while pumping in 100kW of RF power. Provided of course IF Sonny's QV conjecture was fully encapsulated in Dr. White's 2015 COMSOL/QV Plasma code simulations, see below, and IF it is based in reality, which is still TBD.
BTW, the time steps along the x-axis in these COMSOL/QV-Plasma code Copper Frustum thruster simulations is in picoseconds or 1x10^-12 seconds.
Best, Paul M.
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#3126 by as58 on 22 Nov, 2016 22:20
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as58:
Short answer, you don't have to believe anything we reported. However if you look at he body of evidence accumulating from all sources including the first EW AIAA paper and the EW Dec 2014 in-vacuum testing I reported here at NSF.com during the spring of 2015, I think most folks would consider that there is a lot of smoke surrounding this phenomenon. And where there is smoke, hopefully their is a fire to engineer. My next goal is to build another 2.45 GHz copper frustum EM-drive, but this time with spherical endcaps and much better drive antenna frequency tuning controls to see if I can evoke the EM-drive fire in a much more convincing way that we have to date. What do you plan to do?
Best, Paul M.
To clarify a possible misunderstanding, I'm not suggesting that you a misreporting what you have seen. What I am saying is that I do not think that the presented experimental data shows evidence of thrust. I find the characterisation of measurements badly lacking so that it is not possible to separate thermal effects from any possible thrust.
As to what I'm planning to do: Nothing much, I'll wait for more results. -
#3127 by rq3 on 22 Nov, 2016 22:29
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...
Now, that's a fine mesh
The mesh of the vacuum on the slot side was specified to be inside>length based>7 mm (arbitrarily chosen) and the slot side cavity was surface>length based > 7 mm (also arbitrary) which resulted in ~225,000 tetrahedra.
...
How long does it take for this model to run ? Took my 32 cores ~10 min
zellerium, just a quick time out to note that the effort you have put into all of this is just phenomenal. Thank you! -
#3128 by rq3 on 22 Nov, 2016 22:39
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Yeah, not looking good to me either. I don't see any model of how it "blurred the impulsive response of this test article in time", nor any empirical indication. What I see is that the response time for all of the calibration pulses is very consistently ~4 seconds at multiple positions of the pendulum, both before and after heating, including in the null test where the pendulum was still highly displaced by the thermal effects when they applied the second calibration pulse.
All:
This will be my last post of the day. The EW Integrated Copper Frustum Test Article (ICFTA) had metallic and plastic components with competing and non-linear thermal expansions and contractions when heated, see previous posted slides on this topic, that when driving the torque pendulum's center of gravity shifts, blurred the impulsive response of this test article in time, dependent on the magnitude of the impulsive force. For me, it is fully explained in the text of the JPP report, so please go back and read it this section again until it hopefully makes sense to you.
Best, Paul M.
JPP means the Journal of Propulsion and Power, right? I do not think the discussion is satisfactory. In particular, why does the measurement device respond so much faster to calibration impulses? And if there are significant non-linearities, how can you justify you measurement protocol, which (as far as I understand) _assumes_ linear superposition of thrust and thermal signal?
EW is not alone in observing there is a time for the force to build up.
Roger also observed it with both the Experimental and Demonstrator EmDrives as attached.
I believe it has to do with the operational best point of the EmDrive being slightly off and the EmDrive pulling the natural resonant freq to be a better match to that of the applied Rf.
Sort of how a slightly off freq magnetron will be pulled into a freq lock with a resonant load that has a higher Q than that of the magnetron even though the high Q load has a different resonant freq to the magnetron. Give them time and they will work it out and lock to each other.
May also be related to the force bandwidth being much narrower than the rtn loss bandwidth.
Point is that EmDrives do generate force but please do not think of that force as being like any force you have ever experienced before. It has very different characterists.
So YES EmDrives can SOMETIME be slow to generate their force as evident by both EW's data and by Roger's data. Here again EW confirm what Roger measured way back in 2002 and 2006.
Phil:
Your above explanation does cover some of what is going on in the slower than expected build up in the force profile for these fall 2015 in-vacuum EW Lab data runs, but IMO not all. First off through 20/20 hindsight it became apparent we picked the worst possible way from a thermal interaction viewpoint to integrate the PLL box and RF amp & its ~5kg heat-sink with the copper frustum. We would have been much better off to have mounted the RF amp and heat-sink at right angles to the frustum's Z-axis thrust axis so their thermally driven expansions and contractions did not interact with the torque pendulum in the very detrimental way they did where we ran them for this fall 2015 test series. My bad! If I had followed the right angle mounting approach the force plots would be much more prompt as was shown in figure 12 in the EW Journal of Propulsion and Power report where the RF amp and heat-sink were used as the torque pendulum's counter mass at the other end of the TP and were their major thermal expansion axis was mounted at right angles to the frustum's thrust axis.
BTW, the EW torque pendulum (TP) was always balanced with one end slightly down relative to the other end, so that it would have a gravity gradient induced preference to home on a zero force point. Otherwise the TP's long-term zero-thrust baseline drift wandered all over the place in a chaotic manner that made repetitive testing near impossible. This TP baseline homing when combined with the center of gravity shifts induced in the TP by my bad integration design choice for the ICFTA is another reason why these in-vacuum force plots look so ugly. However there IS still a real impulse force being generated in these in-vacuum runs that is riding on all the thermally induced TP zero-thrust cg-baseline shifts. Next time around though with the use of spherical endcaps in the frustums, we shouldn't have to worry so much about these thermal issues if we can match or better your TE013 ~8-milli-Newton thruster performance.
Best, and get well soonest.
Paul M.
Paul,
What I do know is even with my 8,000 Q frustum, if the freq was off even a few kHz, the frustum would sit there and "fart around" maybe generating a force or maybe not.
That was when I mapped the force bandwidth and found it was very much narrower than the rtn loss bandwidth.
It was also why I developed the technique to tune for min reflected power at low power, a watt or so, then step it up to 10 watts and recheck lowest reflected power and then quickly kick the power to 100 watts and recheck again. Each time trying to do the tuning check in less than 10 sec. Then let everything cool down and do another quick check, another cool down and do the money shot for weight change on the scale.
I found that not doing this process could still generate a weight change on the scale but not immediately. However if I did the tuning correctly, force generation seemed to be immediate.
Which says that even though all I had was the digital readout on my scale, I could still see a not properly tuned EmDrive struggle to generate Force.
Which I believe fits with what EW saw and what Roger saw. Static force generation may not be immediate but the EmDrive may still be able to lock onto a not perfect tune and still generate Force but not immediately.
So, once again, you need a force locked loop, not a phase locked loop (and NOT the frequency locked loop you are currently chasing). The difference is a fairly trivial modification to the "magic happens inside" box you have shown ad nauseum in your "schematics". -
#3129 by ARW on 22 Nov, 2016 22:49
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Could someone tell me approximate cost of proper high powered build so the tests could be done even in high power(kilowatt) range. Reason I'm asking this is because I may have possibility to financially back the build.
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#3130 by Flyby on 22 Nov, 2016 22:50
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I'm asking for more insight on the relation between momentum and reflectance, because it would have profound implications :......questions to why i consider this a "complex system". If momentum changes in a non linear way, depending on the "incidence angle" and on "frequency change" then it is damn hard to track the exact values...
OK, yes complex in that sense, there are yet unresolved aspects about this for example the Abraham/Minkowski paradox: https://en.wikipedia.org/wiki/Abraham%E2%80%93Minkowski_controversy. Regardless of my opinion about this controversy, the fact that this is still a controversy where different scientists still disagree, shows the complexity of electromagnetic waves, photons and material interaction. Copper is not a dielectric, which is the focus of this controversy, but the issue of precisely the nature of the electromagnetic momentum within the skin depth of copper (or the London penetration depth in a superconductor) is complex (in that sense ).
If i may simplify the situation a bit to explain what was perhaps a bit too poorly elaborated :
I recall the discussions about the tennis balls bouncing back and forth in a huge frustum space station.
As long you consider the reflectance of the walls to be uniform in every direction, it is only the angle of incidence that will determine the size of the momentum. And in the end, when you add up all bounces, the final sum of all forces will be zero. That much I understood...
But I see a problem if the reflectance of the walls would vary according the direction you throw the balls. It would mean that for the direction (small end > big end) the transfer of momentum/force would be smaller then what the angle of incidence would predict.
So, it puzzles me on how the relation is then, between the reflectance and the momentum transfer ? -
#3131 by M.LeBel on 22 Nov, 2016 22:56
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EW is not alone in observing there is a time for the force to build up.
Roger also observed it with both the Experimental and Demonstrator EmDrives as attached.
I believe it has to do with the operational best point of the EmDrive being slightly off and the EmDrive pulling the natural resonant freq to be a better match to that of the applied Rf.......
...... So YES EmDrives can SOMETIME be slow to generate their force as evident by both EW's data and by Roger's data. Here again EW confirm what Roger measured way back in 2002 and 2006.
IMO, and as previously discussed, everything we have a grasp on is made of these quantum vacuum fluctuations (qvf); B field, E field, em waves, matter etc. So, we are already playing a lot with these qvf but not in the best of ways.
So, one possible explanation, to the slow build up of the force (above) may indicate/suggest a proper polarization or sorting build-up and accumulation of these qvf... forming the required causal structure, i.e. a time rate differential across some portion of the test article..
Food for thought ... -
#3132 by rfmwguy on 22 Nov, 2016 23:09
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Could someone tell me approximate cost of proper high powered build so the tests could be done even in high power(kilowatt) range. Reason I'm asking this is because I may have possibility to financially back the build.
$10,000 us give or take. And this is doing most mechanical work yourself. High precision build and test could multiply 10 fold. This is not a cheap endeavor...I know personally. -
#3133 by HMXHMX on 23 Nov, 2016 00:32
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Could someone tell me approximate cost of proper high powered build so the tests could be done even in high power(kilowatt) range. Reason I'm asking this is because I may have possibility to financially back the build.
$10,000 us give or take. And this is doing most mechanical work yourself. High precision build and test could multiply 10 fold. This is not a cheap endeavor...I know personally.
SSI would also be interested in contributing towards an ultra-high-power build (i.e., multi kilowatt), provided it was competently and safely executed. PM me. -
#3134 by zellerium on 23 Nov, 2016 00:38
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Thank you for your kind words, but my effort pales in comparison to several of the contributors on this forum who we are all greatly thankful for
zellerium, just a quick time out to note that the effort you have put into all of this is just phenomenal. Thank you! Could someone tell me approximate cost of proper high powered build so the tests could be done even in high power(kilowatt) range. Reason I'm asking this is because I may have possibility to financially back the build.
Well if you go "proper" enough, you don't want the high power. Meaning, if you put it on a satellite you couldn't afford the mass for a high power experiment unless you convince some one like Space Systems Loral to weave your experiment into their Comms Sat.
Lets say we can send a 10 kg 6U like Cannae into LEO for 545,000.
If we go for a rotational demonstration, meaning our EM Drive is on the end of our 6U and thrusting perpendicularly, and we get .4 N/kW at a .1 meter offset from the CG, our angular acceleration would be
alpha = tau/I = .04 Nm/(m0/12(w^2+d^2)) = 1/3 rad/s^2
if we get 600 seconds of constant acceleration then we could get up to ~1/2 rotation per second!
(assuming a constant mass distribution, and no outside perturbations)
That seems a little too good to be true, maybe I goofed or we're being generous with the N/kW...
OR maybe 1 kW is completely unnecessary and we should opt for less power.
I don't think I've ever seen a 1 kW amp under 5 kg but I haven't seen that many...
We'll assume 20% mass for batteries and 20% for structure which only leaves us 6 kg. Assuming we can get an amp under 3 kg leaves us 2 kg for the frustum/waveguides/electronic frequency tracking etc and then we've got 1 kg left for thermal and accessories.
So a 6U sounds a bit cramped, but definitely possible if we lower the power. And we could get it there for 545k.
I don't know how long it would take to design and build, maybe 1-2 years? My guess on parts would be 400-500k, labor maybe 300k...
So I think I could do it for ~1.5 Million USD. Anyone want to fund me?
On second thought, I think we'd be better off using the money for a higher power ground test. Spend a few hundred thousand on a MW amp, beam it via antenna to a robust little frustum surrounded by a sealed container full of phase change materials to keep it from melting... At least that way we get to keep the amp when we're finished. -
#3135 by Rodal on 23 Nov, 2016 00:53
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Convergence to the correct solution of Maxwell's equation is not guaranteed even for a very fine mesh.The contours on the small end are clearly not fine enough, the contours are not even uniformly symmetric around the axis of axysymmetry.
One must be very careful with these numerical solutions, particularly when using "automatic meshing".
These FEKO results shown for TM212 are not as good as the COMSOL FEA analysis done at NASA.
I do not think that COMSOL is all that great either (I particularly dislike the fact that COMSOL does not appear to have a theoretical manual, it just has users manuals), it is not on the same class as ABAQUS or ADINA.
These meshes are too coarse, the contour boundaries are not smooth, being polygonal, and showing some artifacts, particularly when looking at details of the solution... The higher the m, n and p, the finer mesh one needs.
The asymmetry in the small end is because I have modeled and am simulating the 13.5mm loop antenna along the side wall. Adding it to the simulation decreases volume thereby increasing the resonant frequency so that what COMSOL returned at 1.9371Ghz will be different from what FEKO returns. I expect perfect resonance is a little higher than 1.9371Ghz in FEKO as the antenna is taken into consideration. I do not believe NASA modeled the antenna in its COMSOL simulations. If I switched to a generic waveguide excitation, the resonant patterns would perfectly match. In this way, modeling the antenna shape, size, and location along with the frustum is a more accurate representation of the system than just using a waveguide excitation centered on one of the endplates.
Actually the Neumann Boundary Conditions themselves depend on the gradient of the function and the gradient is very sensitive to the coarseness of the mesh. There are also distortion issues with finite meshes and other issues, too long to write about...
Modeling an asymmetrically placed antenna demands a finer mesh. The greater the gradients in your problem, the finer mesh you need.
The way to assess convergence is ... by performing a convergence study. If you perform a convergence study you have to multiply the number of nodes in each dimension by a multiple factor.
A single finite mesh cannot be used, in any case, to asses that the mesh is fine enough. Three points define a parabola, 2 define a line, and with one point...we have no convergence information. -
#3136 by rq3 on 23 Nov, 2016 01:00
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I'm asking for more insight on the relation between momentum and reflectance, because it would have profound implications :......questions to why i consider this a "complex system". If momentum changes in a non linear way, depending on the "incidence angle" and on "frequency change" then it is damn hard to track the exact values...
OK, yes complex in that sense, there are yet unresolved aspects about this for example the Abraham/Minkowski paradox: https://en.wikipedia.org/wiki/Abraham%E2%80%93Minkowski_controversy. Regardless of my opinion about this controversy, the fact that this is still a controversy where different scientists still disagree, shows the complexity of electromagnetic waves, photons and material interaction. Copper is not a dielectric, which is the focus of this controversy, but the issue of precisely the nature of the electromagnetic momentum within the skin depth of copper (or the London penetration depth in a superconductor) is complex (in that sense ).
If i may simplify the situation a bit to explain what was perhaps a bit too poorly elaborated :
I recall the discussions about the tennis balls bouncing back and forth in a huge frustum space station.
As long you consider the reflectance of the walls to be uniform in every direction, it is only the angle of incidence that will determine the size of the momentum. And in the end, when you add up all bounces, the final sum of all forces will be zero. That much I understood...
But I see a problem if the reflectance of the walls would vary according the direction you throw the balls. It would mean that for the direction (small end > big end) the transfer of momentum/force would be smaller then what the angle of incidence would predict.
So, it puzzles me on how the relation is then, between the reflectance and the momentum transfer ?
To put it simply, physics as we know it requires a force to THROW THE BALL! If you're in a funnel shaped copper cavity headed towards the moon, and you throw a tennis ball towards the moon, you and your cavity are accelerated away from the moon due to the energy required to THROW THE BALL. The tennis ball can then hit a steel plate, a mattress, or glance off the walls. It doesn't matter. When all of the energy has dissipated and the ball has come to rest, the net result is zero gain in momentum. At the most basic level, this is the fundamental issue with the Emdrive, and the issue every one here is trying to explain.
EDIT: Of course, an Emdrive is constantly stuffing more and more tennis balls into your copper cavity, and insisting that you throw them in a collimated fashion so that as one tennis ball is leaving your hand, the last one you threw is just exactly bouncing off the wall of your choice (hence all of the discussion about modes and Q). The more tennis balls you can deal with, the greater the Q. The end result is the same. You're going nowhere at a great rate, surrounded by tennis balls. Unless, of course, current physics is incomplete. And I'm sure it is
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#3137 by SeeShells on 23 Nov, 2016 01:03
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Or like me build several drives, two labs and three test stands and now I'm building a third EM and vibration isolated lab. It adds up. I'm about to double the +20k I already have into this already as this next phase will run around 20k with me doing most of the grunt work, insulating, wiring, even roofing and pouring the cement. While this is nowhere to a bare bone minimal entry 500K budget this deserves to start up I hope it can provide solid data and a good DYI lab and test bed for some of the drives I have planned.Could someone tell me approximate cost of proper high powered build so the tests could be done even in high power(kilowatt) range. Reason I'm asking this is because I may have possibility to financially back the build.
$10,000 us give or take. And this is doing most mechanical work yourself. High precision build and test could multiply 10 fold. This is not a cheap endeavor...I know personally.
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#3138 by rfmwguy on 23 Nov, 2016 01:18
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Yep, I figured about $10K but I outsourced nothing and had the tools to do metalworking. My test stand was very simple and biggest expense was Lds. Software was basic and I/o to laptop was as I could afford. However, the best lessons learned come from making due with minimal resources.
Or like me build several drives, two labs and three test stands and now I'm building a third EM and vibration isolated lab. It adds up. I'm about to double the +20k I already have into this already as this next phase will run around 20k with me doing most of the grunt work, insulating, wiring, even roofing and pouring the cement. While this is nowhere to a bare bone minimal entry 500K budget this deserves to start up I hope it can provide solid data and a good DYI lab and test bed for some of the drives I have planned.Could someone tell me approximate cost of proper high powered build so the tests could be done even in high power(kilowatt) range. Reason I'm asking this is because I may have possibility to financially back the build.
$10,000 us give or take. And this is doing most mechanical work yourself. High precision build and test could multiply 10 fold. This is not a cheap endeavor...I know personally.
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#3139 by WarpTech on 23 Nov, 2016 01:28
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EW is not alone in observing there is a time for the force to build up.
Roger also observed it with both the Experimental and Demonstrator EmDrives as attached.
I believe it has to do with the operational best point of the EmDrive being slightly off and the EmDrive pulling the natural resonant freq to be a better match to that of the applied Rf.......
...... So YES EmDrives can SOMETIME be slow to generate their force as evident by both EW's data and by Roger's data. Here again EW confirm what Roger measured way back in 2002 and 2006.
IMO, and as previously discussed, everything we have a grasp on is made of these quantum vacuum fluctuations (qvf); B field, E field, em waves, matter etc. So, we are already playing a lot with these qvf but not in the best of ways.
So, one possible explanation, to the slow build up of the force (above) may indicate/suggest a proper polarization or sorting build-up and accumulation of these qvf... forming the required causal structure, i.e. a time rate differential across some portion of the test article..
Food for thought ...
Here's a more practical idea. My theory says that the thrust is due to asymmetrical power dissipation (losses) and dispersion. Perhaps it takes a while for the metal to heat up. Resistance increases with temperature, creating higher losses and there may be a threshold where the asymmetry is finally enough to produce a measurable effect. I have not seen any results for a fully superconducting EmDrive.
From what I know about the QV, 99.999% of the energy is in the bandwidth STARTING at 10^22 Hz and going up from there. This is why I do not see MiHsC as a viable theory, nor do I see Dr. Whites QV model as a viable option. The modes that are not allowed in the frustum are "negligible" in comparison to the vacuum energy density starting at 10^22 Hz and up, where matter is transparent and the asymmetry results in Gravity. The EmDrive is operating 13 orders of magnitude lower frequency. So to me, the QV is out of the picture.
. Hopefully we may reach a happy medium steering away from either end 