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#980 by aceshigh on 23 Feb, 2015 03:50
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What are the reports coming from China? I guess I missed the links
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#981 by Star-Drive on 23 Feb, 2015 04:04
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Dr. Rodal:
Thanks for the concern over my employment, but everyone is replaceable to one degree or another. And there are at least two federal civil servants involved with the Eagleworks Lab that will carry on, albeit a bit more slowly, if I have to find other activities to fill my golden years. Activities like finishing my home lab that has been on hold since going back to work at the NASA/JSC/Eagleworks Lab for the last four years helping mature Dr. White's QVF vision. What will be, will be. Now back to trying to understand how these EM-Drives might actually work...
Best, Paul M. -
#982 by Rodal on 23 Feb, 2015 14:58
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Dr. Rodal:
Thanks for the concern over my employment, but everyone is replaceable to one degree or another. And there are at least two federal civil servants involved with the Eagleworks Lab that will carry on, albeit a bit more slowly, if I have to find other activities to fill my golden years. Activities like finishing my home lab that has been on hold since going back to work at the NASA/JSC/Eagleworks Lab for the last four years helping mature Dr. White's QVF vision. What will be, will be. Now back to trying to understand how these EM-Drives might actually work...
Best, Paul M.
"Experience without theory is blind, but theory without experience is mere intellectual play."
Immanuel Kant -
#983 by lasoi on 23 Feb, 2015 15:12
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It's almost as though the NASA establishment is reluctant to put too many resources into it for fear of looking bad if it doesn't pan out. You hope that isn't the case. If it doesn't pan out it doesn't pan out. But you don't have to be a rocket scientist to see the potential if it does happen to work. I've read that NASA doesn't or can't accept crowdfunding, which is a shame if true- and a bit odd since its entire budget is basically crowd funding through tax revenues.
By the looks of things, there will be another "sputnik" moment--but this time it will be the Chinese not the Russians, and the EM Drive not the satellite. As much as I'd like to see the US stay out ahead on this one, if the new sputnik-EM Drive-China moment needs to happen to revive the support of the US government and spur a corresponding rise in NASA's budget, then let's hope it happens, and soon.
Well if the reports from China are true, if we don't roll out something impressive soon, they already beat us to the punch.
http://www.economist.com/node/11791539 -
#984 by MikeMcCulloch on 23 Feb, 2015 15:21
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Dear excellent NSF forum. This is just to say (for those who don't know) that I've suggested a specific new model for inertia that predicts galaxy rotation without dark matter (it is called MiHsC) and I recently compared its predictions with the 9 EmDrive results with 'some' (not perfect) success. You can see the results by looking at the Table here:
http://physicsfromtheedge.blogspot.co.uk/2015/02/mihsc-vs-emdrive-data-3d.html
I've also published a paper summarising this comparison (slightly out of date now) here
http://www.ptep-online.com/index_files/2015/PP-40-15.PDF
I'd encourage those with other interesting explanations of the EmDrive to make a similar comparison between predictions and data, so we can compare using the facts. If you have any more data points to add, or if you disagree with the numbers in my Table, please let me know. -
#985 by Rodal on 23 Feb, 2015 15:47
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Dear excellent NSF forum. This is just to say (for those who don't know) that I've suggested a specific new model for inertia that predicts galaxy rotation without dark matter (it is called MiHsC) and I recently compared its predictions with the 9 EmDrive results with 'some' (not perfect) success. You can see the results by looking at the Table here:
Yes, as (arguably) the greatest Mathematician/Physicist in recent times (John Von Neumann) wrote:
http://physicsfromtheedge.blogspot.co.uk/2015/02/mihsc-vs-emdrive-data-3d.html
I've also published a paper summarising this comparison (slightly out of date now) here
http://www.ptep-online.com/index_files/2015/PP-40-15.PDF
I'd encourage those with other interesting explanations of the EmDrive to make a similar comparison between predictions and data, so we can compare using the facts. If you have any more data points to add, or if you disagree with the numbers in my Table, please let me know.Quote from: John Von NeumannThe sciences do not try to explain, they hardly even try to interpret, they mainly make models. By a model is meant a mathematical construct which, with the addition of certain verbal interpretations, describes observed phenomena. The justification of such a mathematical construct is solely and precisely that it is expected to work.
Papers with theories that can't predict anything, according to Von Neumann, are not science, because science is all about mathematical models that precisely describe the observed phenomena.
However people may find rigorous fault with any of them, presently there are only three publicly disclosed mathematical formulations that predict a given magnitude of thrust for the EM Drive: Shawyer's, McCulloch's and Dr. Notsosureofit's.
The formulation by Dr. Notsosureofit is the only one known to incorporate the electromagnetic mode shapes of operation.
Here is the formulation of Dr. "Notsosureofit" and a table of results.@ RODAL
Arrgh, Mondays !
Looked over my bleary weekend, noticed I was using diameters AGAIN !
Mode Frequency (MHz) Quality Factor, Q Input Power (W) Mean Thrust (μN) Calculated w/o
dielectric
TE012 1880.4 22000 2.6 55.4 10.8
TM212 1932.6 7320 16.9 91.2 38.5
TM212 1936.7 18100 16.7 50.1 93.5
TM212 1937.115 6726 50 66 104.0
Anyway, shows it pays to rewrite everything in the same place !
....
Great !
In order to understand the above, (please correct me if I am wrong), you used in your formula the actual frequency and mode shapes that took place in the EM Drive experiment with the dielectric so in that sense you did calculate with the dielectric in a very restricted sense.
FYI
Cleanup and de-typo of the take on applying the Equivalence Principle.
The proposition that dispersion caused by an accelerating frame of reference implied an accelerating frame of reference caused by a dispersive cavity resonator. (to 1st order using massless, perfectly conducting cavity, no dielectric)
Starting with the expressions for the frequency of a cylindrical RF cavity:
f = (c/(2*Pi))*((X/R)^2+((p*Pi)/L)^2)^.5
For TM modes, X = X[sub m,n] = the n-th zero of the m-th Bessel function.
[1,1]=3.83, [0,1]=2.40, [0,2]=5.52 [1,2]=7.02, [2,1]=5.14, [2,2]=8.42, [1,3]=10.17, etc.
and for TE modes, X = X'[sub m,n] = the n-th zero of the derivative of the m-th Bessel function.
[0,1]=3.83, [1,1]=1.84, [2,1]=3.05, [0,2]=7.02, [1,2]=5.33, [1,3]=8.54, [0,3]=10.17, [2,2]=6.71, etc.
Rotate the dispersion relation of the cavity into Doppler frame to get the Doppler shifts, that is to say, look at the dispersion curve intersections of constant wave number instead of constant frequency.
df = (1/(2*f))*(c/(2*Pi))^2*X^2*((1/Rs^2)-(1/Rb^2))
and from there the expression for the acceleration g from:
g = (c^2/L)*(df/f) such that:
g = (c^2/(2*L*f^2))*(c/(2*Pi))^2*X^2*((1/Rs^2)-(1/Rb^2))
Using the "weight" of the photon in the accelerated frame from:
"W" = (h*f/c^2)*g => "W" = T = (h/L)*df
gives thrust per photon:
T = (h/(2*L*f))*(c/(2*pi))^2*X^2*((1/Rs^2)-(1/Rb^2))
If the number of photons is (P/hf)*(Q/2*pi) then:
NT = P*Q*(1/(4*pi*L*f^3))*(c/(2*pi))^2*X^2*((1/Rs^2)-(1/Rb^2))
This does fit (as far as I've gotten) the concept of a self-accelerating Dirac wavepacket (which does conserve momentum).
Slow goin', thanks for your patience.
Excellent! Thank you for posting the complete equations.
One suggestion: In the expression NT = P*Q*(1/(4*pi*L*f^3))*(c/(2*pi))^2*X^2*((1/Rs^2)-(1/Rb^2))
the speed of light in vacuum "c" appears in the numerator without being divided by the SquareRoot of the relative electric permittivity and relative magnetic permeability.
Since the relative electric permittivity of the dielectric is 2.3, this would decrease the values in the table by a factor of Sqrt[2.3]=1.52 if the whole cavity would be occupied by the dielectric. Granted that only a portion of the truncated cone contains the dielectric, which will decrease the dividing factor, but any amount will reduce the effective value of c in the medium, giving lower thrust and hence values closer to the experimental measurements.
For example, very roughly, assuming that 1/3 of the longitudinal length is occupied by the dielectric, and using the average as a medium with those average properties, Sqrt[(2.3*1/3)+1*(2/3)]=1.20, the thrust values would be reduced by a factor of 1.20, so for the most important test (the one in recently performed in vacuum, -the other experimental values may have been affected by thermal convection effects in the air and are therefore less reliable-), instead of 104 μN you would get 87 μN, which better compares with the experimental value of 66 μN. -
#986 by Rodal on 23 Feb, 2015 20:53
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This thread has resulted in great synergy between NSF contributors and Paul March at NASA, and I wanted to take this opportunity to name a partial list of accomplishments and thank everybody that has contributed -including a few humble persons who privately asked me not to list their numerous valuable contributions -(please forgive me if I am missing important contributions, tell me what I missed, or if you disagree, what I should correct):
Consideration was made of whether the experimental measurements of thrust force were the result of an artifact. Dr. Rodal, one of the contributors, solved the nonlinear, fully coupled system of differential equations (including magnetic damping) of an inverted torque pendulum with Mathematica to examine whether parasitic modes or nonlinear dynamics could be involved. Chaotic motion and strange attractors were also examined. Comparison with the experimental results showed that none of these nonlinear dynamics effects were involved in the experimental measurements at NASA Eagleworks, and therefore a nonlinear dynamics cause was eliminated. Dr. Rodal (in the US) also conducted Power Spectral Density and Autocorrelation analysis of NASA's experimental data and worked with another contributor, @frobnicat, (in France) to examine the dynamics of the experimental response. They concluded that indeed NASA's experimental measurements exhibited the expected response of NASA's torque pendulum as excited by an initial thrust force impulse followed by a thrust force response during the 30 to 40 sec length of the experiments. Dr. Rodal analyzed possible thermal instability (thermal buckling of the flat ends) as a cause for the measured thrust and reported this at NSF and at ResearchGate (https://www.researchgate.net/publication/268804028_NASA%27S_MICROWAVE_PROPELLANT-LESS_THRUSTER_ANOMALOUS_RESULTS_CONSIDERATION_OF_A_THERMO-MECHANICAL_EFFECT). A thermo-mechanical effect (thermal buckling) is shown that occurs in less than 1 second (for the copper thickness employed for the microwave cavity), with a temperature increase of a degree C or less and that results in forces of the same magnitude as reportedly measured by NASA. Moreover, this thermal instability produces forces in the same direction as measured, and it will occur in a vacuum (since the heating can be due either to induction heating from the axial magnetic field in a TE mode or resistive heating due to the axial electric field in a TM mode). However, this effect can only explain the initial impulsive force and cannot explain the longer 30 to 40 second measured force. Thus the thrust force measured for up to 40 second is not nullified by this explanation either.
Thermal expansion effect as posited by a team from Oak Ridge National Labs for another propellant-less set of experiments was also eliminated as a possible source by the NSF contributors because it would result in forces in the complete opposite direction as the forces measured by NASA.
One of the participants in the NSF forum is Dr. McCulloch (an academic from the UK), who independently developed a tentative theoretical explanation for the EM Drive: assuming that photons have inertial mass, which is caused by Unruh radiation, whose wavelengths must fit inside the EM Drive cone, more Unruh waves fit in at the wide end of the EM Drive, so photons traveling along the axis would always gain mass going towards the wide end and lose it going the other way. This is equivalent to expelling mass towards the wide end, so the EM Drive must move towards its narrow end to conserve momentum. This agrees with the (forward) direction of movement of the EM Drive in reported NASA experiments. Dr. McCulloch derived a simple formula to predict the thrust force and published his theory in the journal Progress in Physics (http://www.ptep-online.com/index_files/2015/PP-40-15.PDF). In his blog and published paper he acknowledges the help from NSF participants (@aero, and @Fornaro) in estimating the geometrical dimensions of the EM Drives tested in the US, UK, and China.
Another participant in the NSF forum, @Notsosureofit (Ph.D. Physics) developed and posted an analysis of the EM Drive thrust considering an accelerating frame of reference caused by a dispersive cavity resonator and obtained a formula to predict the thrust of the EM Drive that takes into account the electromagnetic mode shape of the EM Drive (unlike the formulas of McCulloch and Shawyer that do not explicitly include mode shape information).
@frobnicat and Dr. Rodal conducted statistical analyses of the experimental data. @frobnicat wrote a computer program that included hundreds of possible combinations of the experimental parameters (such as power input, frequency, Q (quality factor of resonance), geometrical dimensions, etc.) to the first few powers. Interestingly the best fitting formulas were similar to the theoretically derived formula by Notsosureofit and also McCulloch's formula.
Astrophysicist TMEubanks examined whether the EM Drive could be coupling to the (Dark Matter) Axion background. He concluded that this is very unlikely (by up to 20 orders of magnitude) due to the findings of the Axion Dark-Matter experiment, looking for yoctowatts (10^-24) of RF power in the 2 - 20 micro-eV range, precisely the range of the EM Drive, by tuning the cavity's resonant frequency to the axion mass. There is simply no way that the Drive is coupling to the axion background - the ADMX would see a whopping signal.
Dr. Rodal obtained an exact solution for the electromagnetic modes in a cavity with similar geometry as the NASA's EM Drive using Mathematica and the theory of spherical waves developed by the Russian/American scientist Schelnukoff. The resulting equations are very similar to the ones posted by Greg Egan (http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html) . Dr. Rodal calculated the natural frequency for electromagnetic modes tested in the EM Drive, from this exact solution, to compare with the NASA predictions by Frank Davies NASA/JSC/EP5 using Finite Element Analysis with the computer code COMSOL. The exact solution results calculated by Dr. Rodal at the NSF forum are only 1% different from the NASA calculations using COMSOL. This confirms the validity of NASA's COMSOL analysis, and that the finite element mesh used was fine enough to result in predicted frequencies that are less than 1% from the exact solution, hence confidence can be had on those calculations. The validity of NASA's COMSOL calculations has been simultaneously confirmed by experimental comparison with the IR thermal camera image produced for mode shape TM212.
NSF member @aero is using MIT's Finite Difference computer code MEEP to calculate the force produced by evanescent waves escaping from the EM Drive and interacting with the stainless steel vacuum chamber. This work is in progress.
Despite considerable effort at NSF to dismiss the reported thrust as an artifact the EM Drive results have yet to be falsified. After consistent reports of thrust measurements from EM Drive experiments in the US, UK, and China, at thrust levels several thousand times in excess of a photon rocket, and now under hard vacuum conditions, the question of where the thrust is coming from deserves serious inquiry. -
#987 by aero on 23 Feb, 2015 22:52
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@Rodal - You get 3 "atta boys" for that post.
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#988 by Flyby on 23 Feb, 2015 23:02
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Nice to have such an overview.
It helps to understand the sometimes overwhelming flood of information and the often complex and difficult to understand discussion points.
A sincere thanks for that, Dr. Rodal...(and all other contributors ofc) -
#989 by aero on 23 Feb, 2015 23:04
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Since Dr. March told us about the broken bolt holding the dielectric disks together, meep has been concerned with how such breaks might effect the forces detected in the simulation. The attached curves show the detected forces with broken dielectric compared to a nominal case.
All three graphs include the nominal case (labeled "Rim gap") where the dielectric is intact but the gap in metal/metal contact between the cone body and the copper end plate varies. Due to computer issues, this gap is much larger than any gap that occurs in the real hardware so the Force/Power shown are only relative to each other, not close in magnitude to the real device.
In all cases the gap varies over a fraction of the thruster height, from 0.003 to 0.01 times height. In the runs made with gaps in the dielectric, "Rim gap" was set equal to 0.004, hence if computer resolution would allow the dielectric gap to go to zero, one would expect the curve to reach the value of approximately -0.0752378657. As is evident, the curves are far from converging to this value.
The first case, the nylon bolt is loose so the gap is between the two dielectric disks. This curve is labeled "Broken Bolt."
The second case, the dielectric is intact but has came loose from the copper end plate. This curve is labeled "Gap at CU face."
The third case is not very meaningful but interesting none-the-less. This curve is labeled "Break=rim gap" and was made in error, with the two dielectric disks separated by an amount equal to the gap in the metal to metal contact of the cone body and the end plate. Both gaps varied from 0.003 to 0.01 times the thruster height. I include it here with the thought that sometimes accidents tell us more than successful plans, though I don't know what this accident is saying.
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#990 by sanman on 23 Feb, 2015 23:09
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This stuff is all an interesting thought exercise, but there's no way it's a Sputnik moment when bulk of the physics community are scoffing at it. Just as with the Hafnium controversy, it would be nice to see the mainstream physics community roped in to at least do an authoritative disproof on it, rather than leaving things to linger on under imagination and speculation.
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#991 by Notsosureofit on 23 Feb, 2015 23:45
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The hafnium controversy never had any replication ..... somewhat different puzzle from either "cold fusion" or EMDrive.
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#992 by Mulletron on 24 Feb, 2015 00:00
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This stuff is all an interesting thought exercise, but there's no way it's a Sputnik moment when bulk of the physics community are scoffing at it. Just as with the Hafnium controversy, it would be nice to see the mainstream physics community roped in to at least do an authoritative disproof on it, rather than leaving things to linger on under imagination and speculation.
Indeed, the goal of many of us on here was/is to try and explain away the reports of thrust from Emdrive, and if we could not, find a more plausible explanation for the thrust, and try to convince others to at least attempt a replication.
To date, Emdrive has yet to be falsified, a few plausible models have been suggested.....the final goal is yet to be accomplished. -
#993 by Stormbringer on 24 Feb, 2015 00:43
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I thought somewhere Dr March had said that GRS's balance sensitivity required an improvement of the thrust signal by 100 percent in order to get successful replication. Did I get that right? I cannot find it now and I have been looking back through the thread for 20 minutes or more. -Anyway; with a deadline of EOM, march; does that mean there is an improved test article about to or in the process of undergoing additional testing at Eagleworks? and can someone link to where that fact (GRS sensitivity limits incapable of detecting current thrust signal level) was posted for reference?
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#994 by Mulletron on 24 Feb, 2015 00:45
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http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326608#msg1326608
Looks like they're almost there. -
#995 by Stormbringer on 24 Feb, 2015 00:46
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#996 by Notsosureofit on 24 Feb, 2015 01:22
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Anyway, still thinking about a possible experiment in vacuum using:
https://www.dropbox.com/s/cmxyj7re8rrb6dh/IMAG0361.jpg?dl=0
to make a stack chamber like:
https://www.dropbox.com/s/wf8wv226h8138n1/IMAG0360.jpg?dl=0
but on an isolation stand.
The idea would be to then balance a tapered oscillator (Gunn Diode ?) cavity and a battery pack w/ a remote photo-switch on a beam held by a suspension fiber and monitor the rotation. I'm thinking one could get some sensitivity multiplication by switching the cavity on and off in time w/ the oscillation frequency of the assembly (easy to do w/ a digital camera) and see if the oscillation amplitude increases w/ time.
Anyone want to try a sensitivity calculation ? Comments ?
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#997 by Rodal on 24 Feb, 2015 01:48
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Anyway, still thinking about a possible experiment in vacuum using:
Do you have this report by Brito, Marini and Gallian, using a Cavendish balance, batteries for power input, oil damping, counterweight and laser measurements ? http://enu.kz/repository/2009/AIAA-2009-5070.pdf
https://www.dropbox.com/s/cmxyj7re8rrb6dh/IMAG0361.jpg?dl=0
to make a stack chamber like:
https://www.dropbox.com/s/wf8wv226h8138n1/IMAG0360.jpg?dl=0
but on an isolation stand.
The idea would be to then balance a tapered oscillator (Gunn Diode ?) cavity and a battery pack w/ a remote photo-switch on a beam held by a suspension fiber and monitor the rotation. I'm thinking one could get some sensitivity multiplication by switching the cavity on and off in time w/ the oscillation frequency of the assembly (easy to do w/ a digital camera) and see if the oscillation amplitude increases w/ time.
Anyone want to try a sensitivity calculation ? Comments ? -
#998 by Lee Jay on 24 Feb, 2015 01:51
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I've tried to do searches of multiple types, and have read a few dozen posts, but I still can't answer what seems to be a very simple question, so I'm going to ask.
Has anyone verified that this isn't turning itself into some type of amplified photonic thruster? -
#999 by Rodal on 24 Feb, 2015 01:56
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.....
The idea would be to then balance a tapered oscillator (Gunn Diode ?) cavity
Disassembled radar speed gun. The grey assembly attached to the end of the copper-colored horn antenna is the Gunn diode oscillator which generates the microwaves.
From Wikipedia http://en.wikipedia.org/wiki/Gunn_diode
