Could the thermal thrust theory be tested by insulating the device with some sort of thermal blanket, such as Mylar?
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
Quote from: RotoSequence on 02/11/2015 02:28 amCould 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. RodalI 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.
... 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. ...
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.
...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. ...
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.
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
Quote3) 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.
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?
... 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.
...I accidentally stumbled upon this report:https://hal.archives-ouvertes.fr/hal-00551421v1/document
Quote from: aero on 02/11/2015 04:12 pmQuote3) 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 have attached a generated drawing of the cavity model used, showing placement of thegaps. 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.
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
Quote from: aero on 02/11/2015 07:13 pmI'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.pdfIt 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).
From a space flight application perspective what is the TRL of the EM Drive?Here is the list:TRL 1. Basic principles observed and reportedTRL 2. Technology concept and/or application formulatedTRL 3. Analytical & experimental critical function and/or characteristic proof-of-conceptTRL 4. Component and/or breadboard validation in laboratory environmentTRL 5. Component and/or breadboard validation in relevant environmentTRL 6. System/subsystem model or prototype demonstration in a relevant environment (ground or space)TRL 7. System prototype demonstration in a space environmentTRL 8. Actual system completed and "Flight qualified" through test and demonstration (ground or space)TRL 9. Actual system "Flight proven" through successful mission operationsI 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.
Maybe of interest?Some interesting tidbits how they did the modelling in the abstract...http://link.springer.com/article/10.1140%2Fepjd%2Fe2014-50798-5Full paper is paywalled however