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#1280 by frobnicat on 07 Mar, 2015 23:20
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Follow-up on the respective contribution to the signal of changes delta_alpha vs delta_d knowing that at a distance D from a pivot delta_d = D delta_alpha. Taking the model D170 (much more sensitive to angle) with a huge bias angle of starting Alpha=5° as a worst case, from my previous post delta_measure=-2*cst2*Alpha*delta_alpha and cst2 = .1128 is in good agreement with documentation. Provided that the calibration to the gain was done according to the procedure described in Philtec docs (check that the peak is 5V) at this bias angle of 5°, the relative lower reflectance due to angle would be compensated by the gain. At 5° (for D170) this is a relative gain of 5/2.17=2.30. Not clear if all is scaled 2.30 times by this compensating calibration including the cst2 factor... have to think about it. Let's say it is, cst2 is now .1128*2.30=.26.
We now have an effect for angle delta_measure(volts)=-2*cst2*Alpha*delta_alpha=+or-2.6*delta_alpha (in degrees, +or- depending on Alpha being -5° or +5°)
For same delta_alpha in degrees, at distance D from pivot the displacement is delta_d = D delta_alpha*pi/180. The sensitivity of D63 at nominal distance is -2.7 mV/µm=2700V/m : delta_measure(volts)=2700*delta_d=47 D delta_alpha. At D=13.88'' (~.35m) around Z that gives delta_measure(volts)=16.6 delta_alpha. At D=1'' around X (?) delta_measure(volts)=1.2 delta_alpha.
Ahem, relatively inconclusive, I expected a clear bound of an order of magnitude or more, but the blue values of the effect of linear displacement alone are not that higher than the red value of the effect of rotation. Note however that would be with a highly angle sensitive D170 angle dependence values, inclined at a worst bias angle of 5°.
Unless anyone has courage to check those laborious calculations and find a blunder, I would consider the case settled : A reasonably well perpendicular (within a few °) D63 that measures tangential movements of a beam at 1'' or more from a pivot will be mostly sensitive to the linear displacement and not to the angular deviation linked to such linear displacement.
This doesn't preclude a few ° angle deviation from perpendicularity between calibration phase and usage to make the D63 work at a less than optimal absolute distance to target, nearer to the peak, at decreased linear sensitivity : we should really concentrate on the vertical scale immediate contradictions (in µm/µN) with calibration pulses of 29.1µN giving readings between 1µm to 5µm displacements instead of the expected 32.3µm from the flexure bearings alone. I'm waiting for Star-Drive comment on that.
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#1281 by zen-in on 08 Mar, 2015 04:09
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The Philtec datasheets describe the RC type distance sensors (RC90, etc) as having 2 adjacent bundles of fibers. The distance sensor used by Eagle Labs is a D63. For a Philtec sensor with 2 bundles of fibers the change in output voltage due to an angular change is dependent on the orientation of the sensor.
Whether the small negative slope in the thrust waveform after RF power is applied is from a change in CM causing a tilt in the mirror or is actually a displacement is impossible to determine emperically. However it is there - along with the anomalous thrust signature, the magnetic interaction at 5.6 A., and the calibration waveforms from the capacitor. Maybe what looks like a thermally induced drift is just random movement.
In the Aug. AIAA paper one of the thrust waveforms (shown below) has an unusual shape. It is bracketed by 300 V. calibration pulses on the capacitor. The calibration pulses have some overshoot/undershoot and ringing that are the typical response of an underdamped system to step responses. This response is determined by the time constant and damping of the apparatus and should not change whatever the driving function is. For example if a fly bumped into the TP and imparted the same momentum as the capacitor with its 300V did, the response should be virtually identical. So why is the response from the RF being switched on and then off (anomalous thrust) so different?
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#1282 by frobnicat on 08 Mar, 2015 10:00
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The Philtec datasheets describe the RC type distance sensors (RC90, etc) as having 2 adjacent bundles of fibers. The distance sensor used by Eagle Labs is a D63. For a Philtec sensor with 2 bundles of fibers the change in output voltage due to an angular change is dependent on the orientation of the sensor.
So ? Are you suggesting the D type should be replaced by a RC type ? The D type that is used now at Eagleworks shows no such dependence on angular change relative to some preferred axis since (from this documentation) ...D model probes with one round fiberoptic bundle... We don't know the details but "round" implies the bundle is rotationally symmetric around its axis.QuoteWhether the small negative slope in the thrust waveform after RF power is applied is from a change in CM causing a tilt in the mirror or is actually a displacement is impossible to determine emperically.
You don't acknowledge the fact that at distance D from a pivot there is a mechanical link between tangential displacement delta_d and "tilt" delta_alpha as per delta_d=D*delta_alpha ? To explain a tilt you would have to explain a tangential displacement as well, unless D=0 or very small (less than 1''). Do you see a reason why, due to a CoM position change, the mirror would tilt around a pivot less that 1'' from its centre ? See attached drawing. Given the mechanical relation between delta_alpha and delta_d, my 2 previous posts show that for D>1'' and a D63 at less than 5° the delta_d aspect is very likely dominant over the delta_alpha impact on measures.QuoteHowever it is there - along with the anomalous thrust signature, the magnetic interaction at 5.6 A., and the calibration waveforms from the capacitor. Maybe what looks like a thermally induced drift is just random movement.
It was acknowledged as thermally induced drift by Paul March, one time (in thread 1) as a change in equilibrium rest position due to heating of flexure bearings by IR radiations, another one (in thread 2) as a change of CoM linked to a continued expansion of test article even after power was stopped (when commenting about the orientations of consequences of buckling). Anyway, it appears too systematic to be just "random movement".QuoteIn the Aug. AIAA paper one of the thrust waveforms (shown below) has an unusual shape. It is bracketed by 300 V. calibration pulses on the capacitor. The calibration pulses have some overshoot/undershoot and ringing that are the typical response of an underdamped system to step responses. This response is determined by the time constant and damping of the apparatus and should not change whatever the driving function is. For example if a fly bumped into the TP and imparted the same momentum as the capacitor with its 300V did, the response should be virtually identical. So why is the response from the RF being switched on and then off (anomalous thrust) so different?
Yes this fig. 22 chart (TE012, 2.6W, 55.4µN reported) is unusual, not time stamped, no vertical scale indications, cal. pulses at 300V 60.1µN instead of the usual 200V 29.1µN (note the non relative proportionality), and very smooth rises and falls for thrust pulses compared to cal. pulses. The overshoot and undershoot would be the same for responses to step rises and falls. The most likely explanation for the lack of ringing for the thrust pulse compared to cal. pulses is that the thrust case the driving function would not be steplike. That particular chart was discussed in thread 1 : http://forum.nasaspaceflight.com/index.php?topic=29276.msg1280094#msg1280094. And even for more "ringing" thrusts responses (more consistent with cal. pulses, like in fig.19) there is still not enough ringing to be explained by a pure step thrust. See bottom pic. in this link to have an idea of what might be the shape of the driving function to explain that. My recollection is that all this semi-quantitative reasoning on relative ringing overshoots hasn't reached general consensus.
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#1283 by zen-in on 08 Mar, 2015 17:02
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Yes this fig. 22 chart (TE012, 2.6W, 55.4µN reported) is unusual, not time stamped, no vertical scale indications, cal. pulses at 300V 60.1µN instead of the usual 200V 29.1µN (note the non relative proportionality), and very smooth rises and falls for thrust pulses compared to cal. pulses. The overshoot and undershoot would be the same for responses to step rises and falls. The most likely explanation for the lack of ringing for the thrust pulse compared to cal. pulses is that the thrust case the driving function would not be steplike. That particular chart was discussed in thread 1 : http://forum.nasaspaceflight.com/index.php?topic=29276.msg1280094#msg1280094. And even for more "ringing" thrusts responses (more consistent with cal. pulses, like in fig.19) there is still not enough ringing to be explained by a pure step thrust. See bottom pic. in this link to have an idea of what might be the shape of the driving function to explain that. My recollection is that all this semi-quantitative reasoning on relative ringing overshoots hasn't reached general consensus.
The driving function consists of step functions. The RF is switched on with a predetermined power level and after a few seconds is switched off. For the emdrive to exhibit a different response to the RF step function compared to the capacitive calibration step function there would have to be some energy storage/release mechanism beyond just having a high Q. And for different RF frequencies this appears to change because the response waveforms are different. The first waveform does show a step-like response initially, but without as much ringing. Then there is a ramp function. It looks like there there are a couple of things happening there. Other thrust waveforms have more similarity to the shape of the step response from the capacitor at different voltages, but are less damped.
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#1284 by Notsosureofit on 08 Mar, 2015 20:55
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FYI
Just to get a feel for dielectrics I tried the straight cylinder with a uniform dielectric variation from end to end.
Using the same simpleminded approximation as the tapered cylinder gives:
del f = ( f/(2*c^2)) * (c1^2-c2^2)
T = (h*f/(2*L*c^2)) * (c1^2-c2^2)
NT = (P*Q/(4*pi*L*f*c^2)) * (c1^2-c2^2)
Which is a lot simpler than I might have expected. Perhaps the approximation is too simple or it represents a special case with " uniform dielectric variation from end to end " rather than a straight conical insert.
In any case, it seems to be telling me to look for the proper integral form to be doing these.
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#1285 by Rodal on 08 Mar, 2015 22:08
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FYI
Just to get a feel for dielectrics I tried the straight cylinder with a uniform dielectric variation from end to end.
Using the same simpleminded approximation as the tapered cylinder gives:
del f = ( f/(2*c^2)) * (c1^2-c2^2)
T = (h*f/(2*L*c^2)) * (c1^2-c2^2)
NT = (P*Q/(4*pi*L*f*c^2)) * (c1^2-c2^2)
Which is a lot simpler than I might have expected. Perhaps the approximation is too simple or it represents a special case with " uniform dielectric variation from end to end " rather than a straight conical insert.
In any case, it seems to be telling me to look for the proper integral form to be doing these.
where, presumably,
c1 = c/Sqrt[relativeElectricPermittivity1*relativeMagneticPermeability1]
and
c2 = c/Sqrt[relativeElectricPermittivity2*relativeMagneticPermeability2]
therefore:
NT = (P*Q/(4*pi*L*f)) * ((1/(relativeElectricPermittivity1*relativeMagneticPermeability1))-(1/(relativeElectricPermittivity2*relativeMagneticPermeability2)))
for dielectrics such that
relativeMagneticPermeability1 = relativeMagneticPermeability2 =1
this simplifies further to:
NT = (P*Q/(4*pi*L*f)) * ((1/(relativeElectricPermittivity1))-(1/(relativeElectricPermittivity2)))
For example, for a cavity containing two coupled sections, one empty with vacuum and the other one with HD PE with relativeElectricPermittivity2 = 2.3
one gets
NT = (P*Q/(4*pi*L*f)) *(1 - (1/2.3))
= (P*Q/(L*f)) *0.04498
which goes to infinity for L->0....
Mmmm, how could that be ?
What happened to the expression (L1/c1 -L2/c2) appearing in the solution of the cylindrical cavity with coupled dielectrics? How did L1 and L2 disapear ?
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#1286 by Notsosureofit on 08 Mar, 2015 23:12
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Well, this isn't going to work for a step function the way it is. We need to find the integral representation along the axis to be able to do that. This is only a close (?) approx for the uniform variation.
L may go down but f goes up.......
c is the only thing that varies here (no step)
Might try a fourier expansion next. Have to think about that.....
ADDED: Can you generate f^4 for the step function? Hard to do by hand on Post-it Notes ! -
#1287 by Rodal on 09 Mar, 2015 00:21
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Well, this isn't going to work for a step function the way it is. We need to find the integral representation along the axis to be able to do that. This is only a close (?) approx for the uniform variation.
L may go down but f goes up.......
c is the only thing that varies here (no step)
Might try a fourier expansion next. Have to think about that.....
ADDED: Can you generate f^4 for the step function? Hard to do by hand on Post-it Notes !
Not sure what you mean.
A fourier expansion of some function in terms of frequency as a parameter? What function of frequency?
Or, expand (the expression for the frequency of a cylindrical cavity containing two dielectrics) in terms of a Fourier expansion up to the fourth term. A Fourier expansion of the frequency in terms of what parameter?
Or, would you like me to express "p" as a function of frequency ? (this can be done: it is a closed-form expression)
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#1288 by Mulletron on 09 Mar, 2015 08:44
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http://ind-tech.com/wp-content/uploads/2014/11/Investment-Memorandum-final.pdf
Guess this didn't work out. It is about 10 years old. There is useful information to be gained from the names and claims made in this document.
On a separate note, in my continuing effort to find pre-existing science to explain the "anomalous thrust" I am surprised that I never uttered the words "cavity optomechanics" until today. This is a much narrower focus than "cavity QED"...which is the framework I am trying to place the "QV momentum transfer" mechanism into. Lots of interesting reading in that very narrow field of study.
I'll post some work related to "cavity optomechanics" in further posts.
I'm not on here to write my own theory of how these thrusters might work; just dig up existing theory. I believe there is plenty of existing science around to do that. I just don't see the point of trying to write new equations which try to fit the data (bouncing around well understood photons is old news * and alone doesn't make thrusters move), when what is really called for is an existing mechanism of action that makes sense. Kinda like this guy said: http://forums.sufficientvelocity.com/posts/2867270/
That is a good thread BTW. Those guys are harsh and I like it. I value reading outside opinions because I don't want to get caught up in my own little bubble and lose insight, like I did for a large part of thread 1.
I believe that a theory explaining Emdrive doesn't require any new science; just application of existing science. When I place myself in the shoes of some physicist out there, and try to view things from that perspective, the last thing I would want to read is some "theory in a bottle" that fully explains Emdrive. I'd rather see established concepts put forth by many experts in their own fields, that can be applied toward an experiment.
I fully believe that marrying cavity optomechanics, with the vacuum momentum mechanisms dug up, and the insight gained from the performance metrics of different mode shapes (experiment matched model and model agreed to calcs done here), and the experimental work at Eagleworks (who is an unconnected 3rd party to the inventors) is enough to warrant further explorations of Emdrive.
To sum all that up, we don't need to invent a new wheel here. There's plenty of wheel parts laying around to build a nice shiny new one that does new things.
It cost me a few hundred bucks to gather the materials to put together a simple test, that is nothing for a lab with an actual science budget. If I'm willing to risk some cash (less than the cost of a new smart phone) trying to answer a question, what is holding up the pros out there?
What is it going to take to get a school or a lab to make or break this silly copper kettle thruster already?
I'm not willing to pass up an opportunity to test something which could go on to be the key to unlocking Humanity's Manifest Destiny; however unlikely. Neither should anyone else with the resources to do the same.
At least Boeing had a look and turned him down, so kudos for that. I haven't seen a clear reason why (they probably already had one,
). The reason is probably buried by an NDA. (If anyone has insight into the Boeing part of this, please provide.)
BZ to Eagleworks for looking, where work is ongoing.
I still can't believe how Shawyer had to go to China to further his efforts.
Okay so for those naysayers out there who think Emdrive is total baloney and there is no science to explain it and that it must violate conservation of momentum, therefore the experiments are all flawed........those arguments are now invalid until proven otherwise.
*Disclaimer: The work being done here with calculating mode shapes, simulation and application thereof is new and very valuable.
Edit:
In contrast to my old somewhat naive interpretation of the physics behind Emdrive (mostly in thread 1 playing around with inertia), I see no evidence which suggests any modification of old physics is required, nor is any new physics.
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#1289 by Notsosureofit on 09 Mar, 2015 15:39
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COFFEE BREAK:
Let me back up a bit.
My initial question was:
In General Relativity (GR), if an RF cavity subject to an accelerating frame of reference (AFR) displays asymmetric frequency dispersion, will an asymmetric RF cavity which exhibits wavelength dispersion generate an accelerating frame of reference ?
The two "simple" approximations, "tapered cylindrical cavity" and "cylindrical cavity w/ uniformly varying dielectric" can be evaluated at the end plates because the difference can be viewed as the result of an integration along the asymmetric axis.
When the cavity is much more complicated, as in the L1,c1 plus L2,c2 case, for which we have an exact frequency solution thanks to a super effort by RODAL, an evaluation just at the end plates is no longer valid. The internal details must now be included in the integrated function.
How to generate the required function along the asymmetric axis is my current concern. A guess might be something like dF(r,theta,z)/dz, which might be represented by a Fourier series expansion in z ?? -
#1290 by Rodal on 09 Mar, 2015 16:07
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EXACT, CLOSED-FORM SOLUTION FOR A CYLINDRICAL CAVITY ELECTROMAGNETIC RESONATOR CONTAINING TWO COUPLED ADJOINING DIELECTRICS FILLING THE CAVITY
Continuing from http://forum.nasaspaceflight.com/index.php?topic=36313.msg1342159#msg1342159
Here I post both
a) the expression for “p” (mode shape quantum number for longitudinal direction) in terms of a given frequency fmnp, where m, n, p are quantum mode shape numbers such that: "m" is the number corresponding to the circumferential-polar-direction, "n" is the number corresponding to the radial--polar-direction and "p" is the number corresponding to the axial-polar-direction.
and
b) the expression for frequency fmnp in terms of a given “p”
where symbols are defined as follows:
L1 = dielectricLength1
L2 = dielectricLength2
and where L1 + L2 = length where "length" is the total internal length of the cylindrical cavity, such that:
L1 = length - L2; (dielectricLength1 = length - dielectricLength2;)
and where we define the following dimensionless ratios:
dD1 = diameter/L1; (dDielectric1 = diameter/dielectricLength1;)
dD2 = diameter/L2; (dDielectric2 = diameter/dielectricLength2;)
The dimensionless quantity "b" is defined as follows:
b := If[modetype == "TM", xbesselzeros[[m + 1, n]]/Pi, If[modetype == "TE", xprimebesselzeros[[m + 1, n]]/Pi]]
where Pi=3.14159265359...
and where Xmn=xbesselzeros[[m+1,n]] (the zeros of the Bessel function)
xbesselzeros = {{2.40483, 5.52008, 8.65373, 11.7915, 14.9309}, {3.83171, 7.01559,
10.1735, 13.3237, 16.4706}, {5.13562, 8.41724, 11.6198, 14.796,
17.9598}, {6.38016, 9.76102, 13.0152, 16.2235, 19.4094}, {7.58834,
11.0647, 14.3725, 17.616, 20.8269}, {8.77148, 12.3386, 15.7002,
18.9801, 22.2178}, {9.93611, 13.5893, 17.0038, 20.3208,
23.5861}, {11.0864, 14.8213, 18.2876, 21.6415, 24.9349}, {12.2251,
16.0378, 19.5545, 22.9452, 26.2668}, {13.3543, 17.2412, 20.807,
24.2339, 27.5837}, {14.4755, 18.4335, 22.047, 25.5095, 28.8874}}
and where X'mn=xprimebesselzeros [[m+1,n]] (the zeros of the derivative of the Bessel function)
xprimebesselzeros = {{3.83171, 7.01559, 10.1735, 13.3237, 16.4706}, {1.84118, 5.33144,
8.53632, 11.706, 14.8636}, {3.05424, 6.70613, 9.96947, 13.1704,
16.3475}, {4.20119, 8.01524, 11.3459, 14.5858, 17.7887}, {5.31755,
9.2824, 12.6819, 15.9641, 19.196}, {6.41562, 10.5199, 13.9872,
17.3128, 20.5755}, {7.50127, 11.7349, 15.2682, 18.6374,
21.9317}, {8.57784, 12.9324, 16.5294, 19.9419, 23.2681}, {9.64742,
14.1155, 17.774, 21.2291, 24.5872}, {10.7114, 15.2867, 19.0046,
22.5014, 25.8913}, {11.7709, 16.4479, 20.223, 23.7607, 27.182}}
For example, for mode TE01, b= xprimebesselzeros[[1,1]]/Pi= 3.83171 / Pi = 3.83171 / 3.14159
NUMERICAL EXAMPLE: we take the case used by @aero, containing a dielectric2 of HD PE material with dielectric constant (relative electric permitivity) = 2.3, and a dielectric1 being the empty portion of the cavity, under vacuum:
diameter = 0.08278945 meter;
length = 0.1224489 meter;
dielectricLength2 = 0.027282494103102 meter;
cMedium1 = cVacuum; cVacuum = 299792458 meter/second;
cMedium2 = cVacuum/Sqrt[2.3] ; (relative electric permittivity=2.3;relative magnetic permeability=1)
Results:
modetype = "TE"; m = 1; n = 1; p = 1; root1 = 2.26774 GHz
modetype = "TE"; m = 1; n = 1; p = 2; root1 = 2.93557 GHz
modetype = "TM"; m = 0; n = 1; p = 2; root1= 3.37114 GHz
For this case, root1 is real, there is no need to consider root2. A number of modes are cut-off, for example modes TE011 and TM011 are cut-off
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#1291 by Mulletron on 09 Mar, 2015 17:06
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Well I called in my old buddies from school to help out. I hope they answer the call. Those men are bonafide geniuses.
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#1292 by aero on 09 Mar, 2015 17:20
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I came across an interesting bit of information while doing background reading on evanescent wave forces.Quote
An intriguing possibility for further increasing the
magnitude of the force is slow-light enhancement,
since the force increases as 1/vg for fixed input power.20
We note that the electrostatic force due to
trapped or induced charges in Si waveguides is esti-
mated to be at least an order of magnitude smaller
than the optically induced force. The Casimir–
Lifshitz force is even smaller. Optical evanescent ...
Quoting from this document:
http://math.mit.edu/~stevenj/papers/PovinelliLo05.pdf -
#1293 by Cinder on 09 Mar, 2015 21:34
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That is a good thread BTW. Those guys are harsh and I like it. I value reading outside opinions because I don't want to get caught up in my own little bubble and lose insight, like I did for a large part of thread 1.
Not up to NSF standards, so hopefully if some of them decide to contribute they won't get this thread locked like thread #1. -
#1294 by Rodal on 09 Mar, 2015 22:37
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I came across an interesting bit of information while doing background reading on evanescent wave forces.
QuoteAn intriguing possibility for further increasing the
magnitude of the force is slow-light enhancement,
since the force increases as 1/vg for fixed input power.20
We note that the electrostatic force due to
trapped or induced charges in Si waveguides is esti-
mated to be at least an order of magnitude smaller
than the optically induced force. The Casimir–
Lifshitz force is even smaller. Optical evanescent ...
Quoting from this document:
http://math.mit.edu/~stevenj/papers/PovinelliLo05.pdf
Highly conjugated polymers with giant electronic orbitals make these materials electroactive yet very stable. The paper below shows a mode of electronic polarizability a giant nomadic polarization, making these organic polymers among the most polarizable materials ever encountered. They claim that one can tailor giant orbital polymers to produce pure and highly stable super-dielectrics with high dielectric constants, from 6 to 100,000.
One more thing for Paul March and others to try...
http://link.springer.com/article/10.1007%2FBF02659632
This is a PhD Thesis (2011) from the University of California on the engineering design of conjugated polymers for organic electronics
http://escholarship.org/uc/item/58c3184d#page-3
This is an article on Super Dielectrics made from inexpensive materials, unfortunately their super-dielectric properties occur at very low frequencies (<10^(−2) Hz))
http://arxiv.org/ftp/arxiv/papers/1403/1403.6862.pdf
http://www.mdpi.com/1996-1944/7/12/8197/pdf
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#1295 by RotoSequence on 09 Mar, 2015 23:07
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We've been laser-focused on materials with greater dielectric constants, but what about materials with similar dielectric constants, like fused quartz? Will the EM drives behave differently?
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#1296 by Rodal on 09 Mar, 2015 23:32
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We've been laser-focused on materials with greater dielectric constants, but what about materials with similar dielectric constants, like fused quartz? Will the EM drives behave differently?
If Paul March discussed testing with dielectric materials other than Teflon and HD PE, I don't recall. It would be interesting if Paul could comment (or if Paul already discussed this, if somebody could bring the experimental results to our attention).
I understand that Roger Shawyer tested non-polymer materials as dielectrics, but the specific results and the dimensions and material properties of the dielectrics tested were not disclosed (again, if anyone has more specific details, please bring them to our attention). -
#1297 by Notsosureofit on 10 Mar, 2015 01:29
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@ RODAL
Just got a minute but from your p expression;
If L1/c1 = L2/c2
del f = (1/2*f)*((c1*c2)/(L1*L2))*b^2*((1/dD1^2)-(1/dD2^2))
might be a solution ??
Got to check the thinking later.
Night !
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#1298 by Rodal on 10 Mar, 2015 01:42
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@ RODAL
Just got a minute but from your p expression;
If L1/c1 = L2/c2
del f = (1/2*f)*((c1*c2)/(L1*L2))*b^2*((1/dD1^2)-(1/dD2^2))
might be a solution ??
Got to check the thinking later.
Night !
I find your previous expression
del f = ( f/(2*c^2)) * (c1^2-c2^2)
more physically appealing, since it goes to zero for equal dielectric constants, regardless or their dielectric length,
while on the other hand
del f = (1/2*f)*((c1*c2)/(L1*L2))*b^2*((1/dD1^2)-(1/dD2^2))
goes to zero for equal dielectric lengths, regardless of their dielectric constants. -
#1299 by Star-Drive on 10 Mar, 2015 03:18
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We've been laser-focused on materials with greater dielectric constants, but what about materials with similar dielectric constants, like fused quartz? Will the EM drives behave differently?
If Paul March discussed testing with dielectric materials other than Teflon and HD PE, I don't recall. It would be interesting if Paul could comment (or if Paul already discussed this, if somebody could bring the experimental results to our attention).
I understand that Roger Shawyer tested non-polymer materials as dielectrics, but the specific results and the dimensions and material properties of the dielectrics tested were not disclosed (again, if anyone has more specific details, please bring them to our attention).
Dr. Rodal:
We've only tried polyethylene, Teflon, neoprene rubber and aluminum oxide discs so far, with PE and PTFE being the most productive. However what dielectric if any will prove to be optimal in generating the most thrust in these EM-Drive like thrusters is really dependent on what physics is really driving their operation. So far the dielectrics with the largest electrostrictive coefficient combined with a largest Q-factor appear to be the winners. This implies to me that fused quartz may be a good candidate, since it has a large Q-factor with moderate electrostrictive coefficient and piezoelectric responses.
BTW, these dielectrics may prove to be the E&M/gravity field to mechanical converters needed to generate thrust. On the other hand if Shawyer and the Chinese are right in their statements that they used no dielectrics in their tens to hundreds of milli-Newton thrusters, then these dielectrics may just be means of amplifying the underlying effects that are generated just by the action of the E&M fields on the copper or silver atoms in the walls of the frustum resonant cavity. Remember that though copper and silver only have a real permittivity of 1.0, in temporal space they have a complex permittivity of greater than 100. and this is the parameter that drives E to B-field phase shifting over very small distances at microwave frequencies, (~2 microns deep at 2.0 GHz). I.e. these metallic atoms can undergo very large cyclic accelerations around their crystal lattice positions as the E&M wave fronts are dissipated in them.
). The reason is probably buried by an NDA. (If anyone has insight into the Boeing part of this, please provide.)