Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2101466 times)

Online Rodal

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Could the thermal thrust theory be tested by insulating the device with some sort of thermal blanket, such as Mylar?
Thermal instability results from the electromagnetic fields heating the interior surfaces of the (big diameter) copper surface.  Since the small diameter surface is shielded by the HD PE dielectric polymer, what gets heated is the big diameter interior surface (and, by thermal conduction, the exterior surface as well, as shown in the IR measurement, attached below).  I understand that the IR measurement was done from the outside, with the IR camera looking at the composite polymer surface of the circuit board surface they had on the exterior of the big diameter flat end.  Since this composite polymer has much lower thermal conductivity and much lower thermal diffusivity than copper, please take into account that these IR measurements represent a temperature and temperature gradients significantly lower than those present on the inner (copper) surface of the big diameter flat end.  In other words, the composite polymer circuit board surface being measured with the IR camera acts like an insulating surface concealing the higher temperature of the inner copper surface.


In my report I proposed that one way to eliminate thermal instabiltity of thin copper sheets is to use copper thick enough to eliminate a thermal instability. 

Quoting my report:

Quote from: Dr. J. Rodal
I have shown that a thermo-mechanical effect (thermal buckling of the base of the truncated cone) can account for some of the "anomalous" results reported by NASA's Brady et.al.  I have shown that the buckling time is under 1 second for copper thicknesses under 0.84 mm (33 thousands of an inch) and just 2.6 watt power input.  I have shown that the buckling temperature increase required is of the order of 1 deg C or less.  I have shown that thermal buckling can produce a sudden output response.

I have shown that the calculated buckling forces agree with the measured force (55.4 microNewtons).  The buckling force is a very strong function of plate thickness (to the fourth power), to prevent thermal buckling from occurring it suffices to have a thicker copper sheet (1/8 inch or thicker would completely prevent this thermal buckling under these input powers).

This thermal buckling effect does not depend at all on air as a conducting medium; it will take place in a complete vacuum as well
(Bold added for emphasis)

Now that NASA is using a higher input power (50 watts) than in the Brady et.al. report, it appears that using a 1/4  inch thick (0.25 inches) copper plate for flat ends would prevent this thermal instability, and hence eliminate this artifact from consideration.

« Last Edit: 02/11/2015 12:15 PM by Rodal »

Offline Star-Drive

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Could the thermal thrust theory be tested by insulating the device with some sort of thermal blanket, such as Mylar?
Thermal instability results from the electromagnetic fields heating the interior surfaces of the (big diameter) copper surface.  Since the small diameter surface is shielded by the HD PE dielectric polymer, what gets heated is the big diameter interior surface (and, by thermal conduction, the exterior surface as well, as shown in the IR measurement, attached below).  I understand that the IR measurement was done from the outside, with the IR camera looking at the composite polymer surface of the circuit board surface they had on the exterior of the big diameter surface.  Since this composite polymer has much lower thermal conductivity and much lower thermal diffusivity than copper, please take into account that these IR measurements represent a temperature and temperature gradients significantly lower than those present on the inner (copper) surface of the big diameter flat end.


In my report I proposed that one way to eliminate thermal instabiltity of thin copper sheets is to use copper thick enough to eliminate a thermal instability. 

Quoting my report:

Quote from: Dr. J. Rodal
I have shown that a thermo-mechanical effect (thermal buckling of the base of the truncated cone) can account for some of the "anomalous" results reported by NASA's Brady et.al.  I have shown that the buckling time is under 1 second for copper thicknesses under 0.84 mm (33 thousands of an inch) and just 2.6 watt power input.  I have shown that the buckling temperature increase required is of the order of 1 deg C or less.  I have shown that thermal buckling can produce a sudden output response.

I have shown that the calculated buckling forces agree with the measured force (55.4 microNewtons).  The buckling force is a very strong function of plate thickness (to the fourth power), to prevent thermal buckling from occurring it suffices to have a thicker copper sheet (1/8 inch or thicker would completely prevent this thermal buckling under these input powers).

This thermal buckling effect does not depend at all on air as a conducting medium; it will take place in a complete vacuum as well
(Bold added for emphasis)

Now that NASA is using a higher input power (50 watts) than in the Brady et.al. report, it appears that using a 1/4  inch thick (0.25 inches) copper plate for flat ends would prevent this thermal instability, and hence eliminate this artifact from consideration.



Please note that what was used for the both the large and small endplates in the Eagleworks copper frustum was 0.063 inch thick FR4 printed circuit board with 1.0 oz copper, (~35 microns thick of Cu epoxied to the FR4 fiberglass), facing the interior of the cavity.

Question: How long does this copper buckling effect last for a 50W run before the frustum test article relaxes back to the torque pendulum's at rest position?  Just as a note, we've already tried re-enforcing the frustum endplates with angle aluminum mounted on their outside surfaces and we didn't notice any marked change in its thrust response.

Next item is back to thermal expansion issues.  Granted that the PE has ~10X the thermal expansion per degree C than copper does, but the PE only seeing ~0.1C rise in part of its volume during a 50W run, whereas the copper frustum endures up to a ~15C rise over its 9.0 inch length, so the copper expansion still dominates.

Next, measureable thrust was not observed when the PE or Teflon discs were removed from the copper frustum while in air with up to 30W of RF using our Mini-Circuit RF amp.  As to why the vacuum test were observing less thrust than in air tests. please note the difference in the RF amps there were driving each test series.  The 30W Mini-Circuit Class-A RF amp was used for the in-air series reported in the 2014 JPC paper, whereas a 100W EMPower Class-A/B RF amplifier was used in the vacuum tests to date.   So how could a less powerful RF amp produce more thrust than a more powerful one?  Now think about what the driven magnitude of the time rate of change of the energy in the vacuum state might bring to this question...

Got to run...

Best, Paul M.
Star-Drive

Online Rodal

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...  Just as a note, we've already tried re-enforcing the frustum endplates with angle aluminum mounted on their outside surfaces and we didn't notice any marked change in its thrust response.
...
This was expected not to make any significant difference.

As I wrote in my report:

Quote from: Dr. J. Rodal
Cotterell and Parkes (based on Cotterell's Ph.D. thesis at the University of Cambridge) correctly point out that the distribution of the heat flux "is not significant in the problem" of thermal buckling of a circular plate, whether the heating takes place uniformly over the whole circular plate or is concentrated in a central region.  Cotterell chose a distribution with a heatedDiameterRatio =1/0.3=3.333 instead of the heatedDiameterRatio=1 analyzed by Noda et.al.  The fact that the exact distribution is not significant for the deltaT that will produce buckling or for the buckling displacement follows from equilibrium: the membrane stress (=E*alpha*deltaT) force resultant (the integral of the membrane stress through the thickness) is reacted at the simply supported edges (that constrain the in-plane displacement).  The membrane force resultant is uniform and it is equal in the polar radial and angular (azimuthal) directions.  If only a central area is heated, the membrane stress is still equilibrated throughout.  If the plate has uniform thickness and isotropic material properties, the strain in the non heated area prior to buckling is the same as in the heated area.

See:

Cotterell, B., and Parkes, E. W.,  Thermal Buckling of Circular Plates, (United Kingdom's) Aeronautical Research Council, Ministry Of Aviation, Reports and Memoranda No. 3245, September, 1960



QUESTION: Why did you use a glass-fiber-reinforced polymer printed circuit board as the end plate ? << 0.063 inch thick FR4 printed circuit board with 1.0 oz copper, (~35 microns thick of Cu epoxied to the FR4 fiberglass)>>

1) The IR measurement was done from the outside, with the IR camera looking at the composite polymer surface of the circuit board surface they had on the exterior of the big diameter flat end.  Since this composite polymer has much lower thermal conductivity and much lower thermal diffusivity than copper, please take into account that these IR measurements represent a temperature and temperature gradients significantly lower than those present on the inner (copper) surface of the big diameter flat end.  In other words, the composite polymer circuit board surface being measured with the IR camera acts like an insulating surface concealing the higher temperature of the inner copper surface. Moreover, due to very low thermal diffusivity of the  glass-fiber-reinforced polymer printed circuit board, measurement of its exterior surface presents a considerable time delay of the interior temperature vs. time profile (as it takes time for the heat to conduct through the thickness of the very low diffusivity  of the  glass-fiber-reinforced polymer printed circuit board).


2) The modulus of elasticity of the glass-fiber-reinforced polymer printed circuit board is much lower than the modulus of elasticity of the copper.  The glass-fiber-reinforced polymer printed circuit board has orders of magnitude lower thermal conductivity and thermal diffusivity than the copper. (Comparison noted below).

3) Why not get rid of the fiber-reinforced-polymer printed circuit board and just simply use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration ?

As to your questions, I would need some time to give them the analytical consideration they deserve and to calculate, rather than give you an impulsive, reflexive, answer that may be incorrect.



NOTE:  FR-4 is a composite material made with woven fiberglass cloth embedded in an epoxy resin (polymer) matrix.  The in-plane Young's modulus of FR4 is 3.0×10^6 psi , about six times smaller than Copper's Young modulus of 17.0×10^6 psi.  The modulus of elasticity in the thickness direction is much lower, practically as low as the modulus of elasticity of epoxy.    FR4's coefficient of thermal expansion - x-axis   1.4×10^(−5) 1/K, Coefficient of thermal expansion - z-axis   7.0×10^(−5) 1/K

The thermal conductivity is a tiny  0.29 W/m·K in the thickness direction, due to the low thermal conductivity of the epoxy resin.  Copper has a thermal conductivity of 401  W/m·K, that is 1400 times higher than the thermal conductivity of FR4
« Last Edit: 02/11/2015 02:22 PM by Rodal »

Online Rodal

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...measureable thrust was not observed when the PE or Teflon discs were removed from the copper frustum while in air with up to 30W of RF using our Mini-Circuit RF amp. ...

1) This was done at a significantly higher frequency than the tests that showed a force measurement (done at 1880.4 MHz to 1936.7 MHz).  Therefore it is not a rigorously valid comparison, particularly since the test done at the frequency of 1936.7 showed a significantly lower performance (Force/PowerInput) than the test done at 1880.4 MHz , and we have no IR imaging of the ends for these tests.

Frequency( MHz)       Thrust (uN)   Power (W)   Thrust/PowerInput
1880.4                     55.4                 2.6         21
1936.7                     50.1               16.7           3
2168                         0 (?)              30              0

1a) It should also have been done at the same frequency.

1b) IR camera temperature imaging of the flat end should have been done for the above cases to ascertain exactly what mode shape took place in each case, in order to better understand the very significant decrease in Thrust/PowerInput from 21 @ 1880.4 MHz , to 3 @1936.7 MHz, to 0 @2168 MHz , and the reported difficulties in reproducing the test at 1880.4 MHz.


Quote from: page 18 of http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
We performed some very early evaluations without the dielectric resonator (TE012 mode at 2168 MHz, with power levels up to ~30 watts) and measured no significant net thrust.

2) Even if done at the same frequency, removing the dielectric polymer and observing much less or no force thrust is not a conclusive way to eliminate thermal instability because removing the dielectric polymer removes its effective shielding of the small diameter flat end of the frustum, which will therefore get heated up and also be subjected to thermal instability, producing a buckling force in the opposite direction than the buckling force from the instability on the big diameter end .

3) The effective way to remove thermal instability as an artifact is to get rid of the fiber-reinforced-epoxy boards at the flat ends and instead use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration
« Last Edit: 02/11/2015 03:38 PM by Rodal »

Offline aero

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3) The effective way to remove thermal instability as an artifact is to get rid of the fiber-reinforced-epoxy boards at the flat ends and instead use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration

No - Don't do that. Step back and look at the issue. We have a situation where we are reasonably certain (assuming a real effect) that something is either:

1 - Tunnelling through the copper end plates or,
2 - Going around the copper end plates,  (via the QV).

In the first case, a quarter inch thick end plate would eliminate tunnelling and eliminate the thrust.
In the second case, who knows, except that logically a thick end plate would shield the thrust effect.

Of course the thick end plate would eliminate thermal effects but it would be a situation of "Throwing out the baby with the bath water."

I personally hold to the "Tunnelling through" concept via evanescent waves, to which point I intend to start posting information next.

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Online Rodal

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3) The effective way to remove thermal instability as an artifact is to get rid of the fiber-reinforced-epoxy boards at the flat ends and instead use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration

No - Don't do that. Step back and look at the issue. We have a situation where we are reasonably certain (assuming a real effect) that something is either:

1 - Tunnelling through the copper end plates or,
2 - Going around the copper end plates,  (via the QV).

In the first case, a quarter inch thick end plate would eliminate tunnelling and eliminate the thrust.
In the second case, who knows, except that logically a thick end plate would shield the thrust effect.

Of course the thick end plate would eliminate thermal effects but it would be a situation of "Throwing out the baby with the bath water."

I personally hold to the "Tunnelling through" concept via evanescent waves, to which point I intend to start posting information next.
Not doing a test that would eliminate thermal instability as a variable because of...assuming that a "Tunnelling through" conjecture may also be eliminated?

The R&D approach is to fearlessly perform many tests to eliminate possible artifacts and alternative explanations and to confirm and reproduce valid tests, not to conduct only a few tests that agree with an assumed theory.
« Last Edit: 02/11/2015 04:58 PM by Rodal »

Online Mulletron

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Quoting @Star-Drive
Quote
As to why the vacuum test were observing less thrust than in air tests. please note the difference in the RF amps there were driving each test series.  The 30W Mini-Circuit Class-A RF amp was used for the in-air series reported in the 2014 JPC paper, whereas a 100W EMPower Class-A/B RF amplifier was used in the vacuum tests to date. So how could a less powerful RF amp produce more thrust than a more powerful one?

This tells me that the presence of an air/PE interface is an important feature and could be exploited to great effect ala Casimir-Lifshitz repulsion attraction. The different permittivity of these two is what's important. I mean, you get thrust with the PE dielectric inserted, you get more with air and PE inserted and none with just air, though I bet you'd get thrust under high power with just air like Shawyer does. The presence of air is clearly doing something good.

If these Emdrives are using the QV to achieve propulsion, we need to use what Casimir, Polder and Lifshitz have taught us and think like them. We can't think like Goddard on this one as we're not shooting anything out the back end. I know this sounds far out but the literature supporting all this is deep and wide and supported by direct observation. Much of this was covered in thread 1. A wide sample of this research is below, basically to show this research is real and to back up my claims. The key thing to really figure out is how these tiny forces are amplified and rectified within a resonant cavity, and only hints (http://www.tuwien.ac.at/en/news/news_detail/article/8908/) of this kind of research have been found so far. It all seems to boil down to confinement. None of the above would make an Emdrive want to thrust and move through space, the final bit is what we uncovered in thread 1 concerning casimir forces with different geometries. We uncovered the casimir force is positive and repulsive inside spheres, corners and cones, unlike parallel plates where it is negative and attractive.

http://www.pnas.org/content/111/29/10485.full possible lead to how the cavity boosts casimir forces
http://en.wikipedia.org/wiki/Dielectric_gas stuff better than air
http://arxiv.org/abs/1004.5243 interesting stuff about PTFE repulsion
http://cnls.lanl.gov/casimir/PresentationsSF/Repulsive_force09.pdf
http://arxiv.org/ftp/quant-ph/papers/0109/0109134.pdf
http://www.nature.com/news/2009/090107/full/news.2009.4.html
http://blogs.discovermagazine.com/80beats/2009/01/08/to-levitate-nano-objects-researchers-exploit-a-force-of-quantum-repulsion/#.VNt5NCzzlah
http://adsabs.harvard.edu/abs/2009Natur.457..170M
http://arxiv.org/abs/1202.6415v2
http://www.newscientist.com/article/dn16374-repulsive-quantum-effect-finally-measured.html#.VNt5Gyzzlai
http://www.nature.com/nature/journal/v457/n7226/abs/nature07610.html
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.045430

Casimir geometry stuff:
http://merlin.fic.uni.lodz.pl/concepts/2005_3_4/2005_3_4_137.pdf
http://arxiv.org/pdf/1306.4370v1.pdf
http://scholar.lib.vt.edu/theses/available/etd-04272004-200428/unrestricted/casimir-effect.pdf
https://aphyr.com/media/pwl-2014-casimir.pdf
https://aphyr.com/media/comps.pdf


Edit: Figured it out, it's attractive between the PE and copper. Really stupid mistake.
« Last Edit: 02/23/2015 05:34 AM by Mulletron »
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Online Rodal

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... None of the above would make an Emdrive want to thrust and move through space, the final bit is what we uncovered in thread 1 concerning casimir forces with different geometries. We uncovered the casimir force is positive and repulsive inside spheres, corners and cones, unlike parallel plates where it is negative and attractive.
....

Substitute below copper 1, air 3, PE 2.

Thanks for supplying this picture analogy as it greatly helps to understand what is being proposed.

Please help me understand the proposed analogy: 

EM Drive copper                              => substitute for egg-shaped object 1 in picture below,
Dielectric HD PE inside the EM Drive => substitute for object 2 in picture below,
Air inside the EM Drive                     => substitute for fluid 3 in picture below,



the egg-shaped object 1 is free to move like an object in a rigid body motion as it is being repelled by object 2.  However, in the EM Drive, the big diameter flat end (object "1") is rigidly attached (by the curved walls of the truncated cone) to the dielectric HD PE (object "2")



 so that while in the picture object 1 can be repelled and move away with a rigid body motion, in the EM Drive the big diameter plate is rigidly attached to the rest of the EM Drive, which is rigidly attached to the dielectric (object "2").  Moreover, the dielectric is inside the EM Drive. So it appears that, even if there would be a repulsive force between the dielectric and the big diameter end, this could not result in a rigid body motion of the EM Drive anymore than a spacecraft cannot move because an astronaut pushes inside it against one of its walls, or because an astronaut inside the spacecraft throws balls at one of its walls or because an astronaut uses a magnet inside the spacecraft to repel another magnet (with the same magnetic pole) that is attached to an internal wall.  They (the spacecraft, the astronaut and the balls and the magnets) are all part of a closed system.  The dielectric HD PE is inside of the EM Drive, hence it is in a closed system.  While on the picture, the egg-shaped object 1 is free to move with rigid body motion as it is being repelled by object 2.
« Last Edit: 02/11/2015 06:13 PM by Rodal »

Offline JPLeRouzic

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...
I accidentally stumbled upon this report:
https://hal.archives-ouvertes.fr/hal-00551421v1/document
Like they say on amazon, if you have been interested in this article, you might want to look at this one:
http://arxiv.org/abs/1411.2107


Offline aero

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3) The effective way to remove thermal instability as an artifact is to get rid of the fiber-reinforced-epoxy boards at the flat ends and instead use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration

No - Don't do that. Step back and look at the issue. We have a situation where we are reasonably certain (assuming a real effect) that something is either:

1 - Tunnelling through the copper end plates or,
2 - Going around the copper end plates,  (via the QV).

In the first case, a quarter inch thick end plate would eliminate tunnelling and eliminate the thrust.
In the second case, who knows, except that logically a thick end plate would shield the thrust effect.

Of course the thick end plate would eliminate thermal effects but it would be a situation of "Throwing out the baby with the bath water."

I personally hold to the "Tunnelling through" concept via evanescent waves, to which point I intend to start posting information next.
Not doing a test that would eliminate thermal instability as a variable because of...assuming that a "Tunnelling through" conjecture may also be eliminated?

The R&D approach is to fearlessly perform many tests to eliminate possible artifacts and alternative explanations and to confirm and reproduce valid tests, not to conduct only a few tests that agree with an assumed theory.

I agree in principle, but in the real world, such tests are designed very carefully to avoid adversely effecting the device under test. Once we develop sufficient knowledge of the cause of the thrust effect that we are certain that the thin end plates are not a key component causing or contributing to the thrust effect, then will be the time to eliminate possible thermal effects using heavy metal as you propose. Until that time, an equally effective test to eliminate thermal effects is to simply turn off the RF power. That's silly, but until we know that thin end plates are not essential, major modification of the cavity entails a great risk of generating false data and is not logical. 
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Offline aero

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First an obligatory cite.
Data provided in this and any following posts has been generated by Meep : A flexible free-software package for electromagnetic simulations, developed at MIT under  Grants from the National Science Foundation, contracts from the Army Research Office, and DARPA monitored contracts from the Office of Naval Research. For detailed description of Meep, see -
http://web.ics.purdue.edu/~pbermel/pdf/Farjadpour09.pdf

Now that that is handled, I have modeled the "Copper Kettle" EM cavity using dimensions provided by Paul March, "Star Drive," on February 7, 2015 here on NSF. Using Meep's built-in function, calculate force/flux external to the cavity excited by a magnetic source at the inside face of the dielectric. I obtain a force of ~ 0.25 mu-N/Watt. This compares to about 1 mu-N/Watt measured experimentally.

You may ask, "Why the big discrepancy?"  While Meep is sufficiently robust to deal with the EM thruster cavity, it was not designed to operate efficiently at those frequency/geometry conditions. More significantly, Meep was designed to measure relative differences in effects rather than absolute values but most importantly, no one knows exactly what it is that should be measured so in seeking an effect it was necessary to make approximations as to how the effect could be generated.

I believe that the EM thruster force results from evanescent waves tunneling through the thin copper end plates or minute gaps in the cavity joins of the end plates thereby exchanging momentum with the cavity and the decelerating photons of the evanescent waves. (to be explained.) Because I do not have access to computational resources required to model thin (35 micron) end surfaces, nor do I have a Meep compatible model valid for copper at 2 GHz, I used thicker "Perfect Metal" to model the cavity geometry. But, because perfect metal is impervious to radiation at all frequencies, I added small gaps at various places around the cavity, mainly in places where gaps could be expected, at the joins between the conic section and the end plates. The detected force changes and is strongly dependent on the placement of the gap.

I have attached a generated drawing of the cavity model used, showing placement of the gaps. This is the placement for which the 0.25 mu-N/Watt force/power was detected, though the gap, at 1.4 mm, is 10 times larger than actually used. That's to make it visible.

Edited to reformat.
« Last Edit: 02/11/2015 06:57 PM by aero »
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Online Mulletron

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@Rodal, the point is to illustrate a positive repulsive attractive force wrt the rest of the vacuum (the universe) in which the Emdrive resides. So if you have a positive vacuum pressure in proximity to a negative vacuum pressure, aligned fore to aft, what do you suppose would happen next? I'd bet something is compelled to move, especially when more energy is pumped into the system as RF. The point is not whether or not the copper/PE can move because they are rigidly attached. Get it? Don't forget about the QV, in which the Emdrive is supposedly getting momentum from, eg an open system.

In the ball example, the ball levitates in order to conserve momentum, which is brought on by symmetries in the laws of physics, after the ball hovers everything is balanced. In the emdrive case there is an asymmetry which enables continuous momentum transfer to the dielectric and the air but the amounts are not equal, and on the front side of the dielectric against the copper is the area of repulsion attraction. It can't move because the PE disc is attached, which doesn't seem to matter to me really. Just the positive region seems important. I barely get it too. It is hard to put all these concepts into perspective.

About half the time when I think this through, the darn thing thrusts backwards. What I need to figure out is how to describe two different unbalances in radiation pressure across the cavity at the same time.
1. Unbalanced Casimir pressure 2. The Shawyer unbalanced radiation pressure.

The best thing they could do is get Dr. Peter Milonni on the horn and ask him for help.

Edit: Figured it out, it's attractive. Hence why I couldn't figure out which way the thrust should go. Stupid mistake.
« Last Edit: 02/23/2015 05:14 AM by Mulletron »
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Online Rodal

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...

I have attached a generated drawing of the cavity model used, showing placement of the
gaps. This is the placement for which the 0.25 mu-N/Watt force/power was detected,
though the gap, at 1.4 mm, is 10 times larger than actually used. That's to make it visible.

MEEP is a finite-difference solver that divides space and time into a regular grid to solve the time evolution of Maxwell’s equations.  A solution of Maxwell's equations in a closed-system (the EM Drive) cannot produce a force that will make it accelerate as a rigid body through space.  Otherwise that would imply that solutions of Maxwell's equations in closed-systems allow breaking conservation of momentum.  Conservation of momentum is one of the main principles in Physics, not violated both in Quantum Mechanics and in General Relativity. 

MEEP calculates the optical force using Maxwell's stress tensor.  The optical force should be reacted within the closed-system of the EM Drive so that the center of mass of the EM Drive should have a zero net force.

Besides Maxwell's equations, and the EM Drive and its internals (the dielectric inside it, etc.), what else have you included in your model and how was it included?
« Last Edit: 02/11/2015 07:14 PM by Rodal »

Offline aero

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I'm not sure that I understand what you are asking for, but you may be interested in looking at the fields generated, both internal and external to the cavity. The first drawing shows a fully enclosed cavity, the second shows a cavity with gaps of 140 microns placed as illustrated in the previous drawing. Both cavities are driven by a magnetic source at the inside face of the dielectric disk, at 1.937115E+009 GHz. Also, both images are at the completion of the 32-nd half period of the drive frequency.

Look closely at the second image. Note the standing waves on both end plates and the RF energy looping from one end to the other, outside the cavity. And also, please read this paper, in particular page 15-16 but the complete paper is pertinent. http://wwwsis.lnf.infn.it/pub/INFN-FM-00-04.pdf
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I'm not sure that I understand what you are asking for, but you may be interested in looking at the fields generated, both internal and external to the cavity. The first drawing shows a fully enclosed cavity, the second shows a cavity with gaps of 140 microns placed as illustrated in the previous drawing. Both cavities are driven by a magnetic source at the inside face of the dielectric disk, at 1.937115E+009 GHz. Also, both images are at the completion of the 32-nd half period of the drive frequency.

Look closely at the second image. Note the standing waves on both end plates and the RF energy looping from one end to the other, outside the cavity. And also, please read this paper, in particular page 15-16 but the complete paper is pertinent. http://wwwsis.lnf.infn.it/pub/INFN-FM-00-04.pdf

It looks to me that you have performed a similar analysis as Prof. Juan Yang in China and Fetta in the US, who solved Maxwell's equations in an EM Drive and also obtained resulting forces, because they did not model the EM Drive as a deformable body.  They just solved Maxwell's equations and obtained a force from Maxwell's Stress Tensor.

It seems to me that you just used MEEP to solve Maxwell's equations.  MEEP considers the EM Drive as a rigid body (you did not input the modulus of elasticity or thermal expansion coefficient or the electro- and magnetorestrictive material constants into the computer code). In the real world the EM Drive deforms due to the electromagnetic field.

This deformation of the EM Drive is quite real, it is because of this deformation that NASA Eagleworks (and others) have trouble keeping the EM Drive in resonance.

As a real body deforms when it is subject to an electromagnetic field you have to include electro- and magnetorestrictive forces in your analysis to model the real-world, in order to satisfy conservation of momentum.  When one does that, the mechanical force on the center of mass of the EM Drive will turn out to be exactly zero, to satisfy conservation of momentum.

To properly do this, you would need a multi-physics computer code (to include the deformation of the EM Drive) like ANSYS, or COMSOL.  (By the way my understanding of the COMSOL analysis done for NASA is that they included the COMSOL programs for Maxwell's equation and heat conduction, but that they did not (?) calculate the coupled deformation of the EM Drive either).



For the closed EM Drive to move through space you would need to, for example, to radiate Unruh radiation (as in Dr. McCulloch's theory), or couple to a frame-dependent (?) Quantum Vacuum (as per Dr. White's theory, etc.), or to have electromagnetic coupling with gravity, or some other form of coupling to an external field, or a Woodward Mach-Effect.  Just solving Maxwell's equations in a closed system won't do it.
« Last Edit: 02/11/2015 08:05 PM by Rodal »

Offline SleeperService

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Maybe of interest?

New method to generate high-power microwaves...
http://phys.org/news/2015-02-high-power-microwave.html

Some interesting tidbits how they did the modelling in the abstract...
http://link.springer.com/article/10.1140%2Fepjd%2Fe2014-50798-5

Full paper is paywalled however  :(

Offline aero

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I'm not sure that I understand what you are asking for, but you may be interested in looking at the fields generated, both internal and external to the cavity. The first drawing shows a fully enclosed cavity, the second shows a cavity with gaps of 140 microns placed as illustrated in the previous drawing. Both cavities are driven by a magnetic source at the inside face of the dielectric disk, at 1.937115E+009 GHz. Also, both images are at the completion of the 32-nd half period of the drive frequency.

Look closely at the second image. Note the standing waves on both end plates and the RF energy looping from one end to the other, outside the cavity. And also, please read this paper, in particular page 15-16 but the complete paper is pertinent. http://wwwsis.lnf.infn.it/pub/INFN-FM-00-04.pdf

It looks to me that you have performed a similar analysis as Prof. Juan Yang in China and Fetta in the US, who solved Maxwell's equations in an EM Drive and also obtained resulting forces, because they did not model the EM Drive as a deformable body.  They just solved Maxwell's equations and obtained a force from Maxwell's Stress Tensor.

It seems to me that you just used MEEP to solve Maxwell's equations.  MEEP considers the EM Drive as a rigid body (you did not input the modulus of elasticity or thermal expansion coefficient or the electro- and magnetorestrictive material constants into the computer code). In the real world the EM Drive deforms due to the electromagnetic field.

This deformation of the EM Drive is quite real, it is because of this deformation that NASA Eagleworks (and others) have trouble keeping the EM Drive in resonance.

As a real body deforms when it is subject to an electromagnetic field you have to include electro- and magnetorestrictive forces in your analysis to model the real-world, in order to satisfy conservation of momentum.  When one does that, the mechanical force on the center of mass of the EM Drive will turn out to be exactly zero, to satisfy conservation of momentum.

To properly do this, you would need a multi-physics computer code (to include the deformation of the EM Drive) like ANSYS, or COMSOL.  (By the way my understanding of the COMSOL analysis done for NASA is that they included the COMSOL programs for Maxwell's equation and heat conduction, but that they did not (?) calculate the coupled deformation of the EM Drive either).




While you are correct in your assumption that Meep treats the cavity as a rigid body, it is incorrect to assume that this data is similar to Prof. Yang's data. Professor Yang calculated forces on the interior of the cavity. Meep has calculated forces in the axial coordinate direction exterior to the cavity. As you must know, evanescent waves are a solution to Maxwell's equations and the forces generated and obtained by integration of the Poynting vector are also represented by solutions to Maxwell's equations. You may wish to take the time to study the paper which I referenced. Perhaps you can tell me where the error in that paper is.

Edit add: The paper develops a mathematical formula giving the superluminal velocity of evanescent waves in a waveguide at low GHz frequencies. It further formulated the problem to calculate that velocity and gives very summary results of a Mathematica solution to that problem.

And I too, doubt the validity of Prof. Yang's and Shawyer's theories.

Oh, and just for clarity, I have measured the forces outside the fully enclosed cavity shown first above. The forces are identically zero for the fully enclosed cavity as has been proven mathematically time and again.
« Last Edit: 02/11/2015 08:03 PM by aero »
Retired, working interesting problems

Online Mulletron

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If I could find direct evidence for a giant casimir effect in a resonant cavity, we'd be all set. I suspect it exists but I gotta find proof. Here's the full paper (at the bottom) about confining vacuum fluctuations to transmission lines that was in the news. http://www.tuwien.ac.at/en/news/news_detail/article/8908/

http://www.pnas.org/content/111/29/10485.full
Challenge your preconceptions, or they will challenge you. - Velik

Online Mulletron

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From a space flight application perspective what is the TRL of the EM Drive?

Here is the list:

TRL 1.    Basic principles observed and reported
TRL 2.    Technology concept and/or application formulated
TRL 3.    Analytical & experimental critical function and/or characteristic proof-of-concept
TRL 4.    Component and/or breadboard validation in laboratory environment
TRL 5.    Component and/or breadboard validation in relevant environment
TRL 6.    System/subsystem model or prototype demonstration in a relevant environment (ground or space)
TRL 7.    System prototype demonstration in a space environment
TRL 8.    Actual system completed and "Flight qualified" through test and demonstration (ground or space)
TRL 9.    Actual system "Flight proven" through successful mission operations

I haven't seen enough experimental data to be able to say what TRL level the EM-Drive would have.   The EM tether has been deployed in orbit so therefore it must have a TRL level of at least 7. 

Edison started with a theory of how an electric light could be built that many thought was impossible.   It was thought to be impossible not because the physics was believed to be wrong but because so many others had tried and failed.

I'd say barely a 2.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Notsosureofit

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Maybe of interest?

Some interesting tidbits how they did the modelling in the abstract...
http://link.springer.com/article/10.1140%2Fepjd%2Fe2014-50798-5

Full paper is paywalled however  :(

This looks worth pursuing. (at least from the dispersion viewpoint)

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