Obviously the right hand of Eq. (8) is the EM force exerted on the EM field boundary of the limited closed volume
@FattyLumpkinThis is the best Cannae like design I could get out of FEKO LITE till now. Would need a full version to come close to Monomorphic´s sims. https://forum.nasaspaceflight.com/index.php?topic=39772.msg1530441#msg1530441
Quote from: X_RaY on 06/13/2016 08:17 pm@FattyLumpkinThis is the best Cannae like design I could get out of FEKO LITE till now. Would need a full version to come close to Monomorphic´s sims. https://forum.nasaspaceflight.com/index.php?topic=39772.msg1530441#msg1530441Great work!1) Have you also tried to model the Cannae device with EM Pro, for which you do not have the limitations of FEKO Light?2) When you used EM Pro in the previous pages for other calculations, did you use the Finite Element module of EM Pro or the finite difference module of EM Pro?
Further to this issue about Boundary Conditions, Jackson has an excellent discussion in his masterpiece Classical Electrodynamics, 3rd Edition, pages 352 to 356 (ISBN-10: 047130932X; ISBN-13: 978-0471309321). Pay special attention to the graph on page 355, Fig. 8.2 "Fields near the surface of a good, but not perfect conductor". For a good but not perfect conductor, for example copper as used in the EM Drive, and as modeled in Meep with the Drude equation model, a very tiny magnitude electric field parallel to the surface will be present, as well as a very tiny magnetic field perpendicular to the surface. The electric field parallel to the surface is inversely proportional to the square root of the conductivity:This solution exhibits the expected rapid exponential decay (skin depth), and Pi/4 phase difference. For a good conductor, the fields inside the metal conductor are parallel to the surface and propagate normal to it, with magnitudes that depend only on the tangential magnetic field parallel to the surface, that exists just outside the surface of the metal conductor.As shown in the graphs in Jackson's book, and as one can readily calculate these fields are practically zero, insignificant for copper, due to its very high conductivity. Therefore it is not a surprise that Meep does not show a significant difference in the fields calculated using the perfect conductor model vs. the Drude model. The main influence of the finite conductivity Drude model is to allow the calculation of a finite Q (instead of an infinite Q). But again, the boundary condition is such that the electric field parallel to the surface and the magnetic field perpendicular to the surface must be practically zero at the surface, due to the very high conductivity of copper. This is particularly so for the experiments of EM Drive where experimenters seek a high Q, which is tantamount to practically zero fields for these variables. It is completely inconsistent for EM Drive experimenters to advocate a high Q (Shawyer even claiming to research superconducting EM Drives) and not realize that these boundary conditions are such that these fields must be practically zero at the surface of the good conductor.NOTE: for those not having ready access to Jackson's monograph, the following discussion by a professor at Duke University is also good: https://www.phy.duke.edu/~rgb/Class/phy319/phy319/node59.html
Quote from: FattyLumpkin on 09/05/2016 11:47 pmI hope there is no confusion re the various projects going on at Cannae...as folks know I've been conducting a study of them1) for the cubesat, they say they are orbiting it at less than 150 miles...not kilometers. Mr. Feta told me there would be no super-cooling of this device. I'm left to conclude that the cooling of their thruster will be passive and that the thruster will be kept in shadow at all times...So they are using miles instead of kilometers to specify an orbit?150*1.60934=241So their orbit is really 241 km ?That makes a difference ! ThanksI calculated with 150 km. (I recall pointing this out weeks ago, when they first announced, that instead of using customary SI units, Cannae is using Miles, oh well )Just like the probe that crashed on Mars years ago (different units !) Will recalculate with 150 miles tomorrow (Is it US Miles )US Survey mile = International mile =1.60934 kmNautical mile = 1.852 kmRoman mile = 1.481 kmChinese mile = 0.5 km
I hope there is no confusion re the various projects going on at Cannae...as folks know I've been conducting a study of them1) for the cubesat, they say they are orbiting it at less than 150 miles...not kilometers. Mr. Feta told me there would be no super-cooling of this device. I'm left to conclude that the cooling of their thruster will be passive and that the thruster will be kept in shadow at all times...
British mathematician Desmond King-Hele of the Royal Aircraft Establishment predicted in 1973 that Skylab would de-orbit and crash to earth in 1979, sooner than NASA's forecast, because of increased solar activity. Greater-than-expected solar activity heated the outer layers of Earth's atmosphere and increased drag on Skylab.
Our thruster configuration for the cubesat mission with Theseus is anticipated to require less than 1.5 U volume and will use less than 10 watts of power to perform station keeping thrusting.
I know I sound like a broken record, but I would really like to know how they plan to separate out thrust effects from the high variability of atmospheric density at those altitudes.
Atmospheric drag on the sat is measurable, but it cannot be ameliorated by always keeping the sat solar array parallel to the orbital velocity vector
The satellite must rotate about its own axis about once every 90 minutes to keep the array pointed at the sun. This rotation will continue in Earth's shadow....
Quote from: Rodal on 11/08/2016 02:22 pmQuote from: X_RaY on 11/08/2016 02:20 pmIs there anyone who has study a half-sphere shaped resonator regarding the emdrive?In contrast to a parabolic one (where the focal depth for rays much shorter than the size of the structure itself was equal to the point where the baseplate was present).http://forum.nasaspaceflight.com/index.php?topic=39214.msg1607020#msg1607020 Now I did an FEA with the half-sphere shape. What I found is a massive fieldstrength, much higher than I ever have observed in the sims before. The Q should be very high.1) What is the numerical analysis package you are using ? (FEKO, etc.) 2) What numerical technique are you using to solve the equations? (Finite Element Method?, Boundary Element Method?, Finite Difference Method Space Domain?)?3) What is the type of solution method? A) Is it an eigensolution to the eigenvalue problem where there is no antenna in the model? B) Or a steady state solution using an antenna and a spectral method to obtain a solution? C) Or a transient solution using an antenna and a Finite Difference Time Domain to obtain a solution?D) If you used an antenna, with a spectral steady-state solution or a transient Finite-Difference-Time-Domain solution, what was the type of antenna and where was it located?4) What are the boundary conditions that you use in the model? Are you assuming a perfect conductor?If not, how are you modeling an imperfect conductor like copper?5) How is the quality factor (Q) calculated?6) How are eddy currents calculated in the model?Thanks1. FEKO 2. MOM & FEM3. ? A. No, no eigenvalue calculation, magnetic Dipole (30mm above the flat plate at the central axis)B. FEM C. No FDTD4.First time the boundary was defined to be PEC. Couldn't believe this numbers, therefore I used Copper, thickness 1mm for the second run (see diagrams).Field pics are from the PEC-run.5.No till now the Q is not calculated. My statement was due to the fieldstrength. 6. Good question, It's a internal calculation of FEKO, don't know their code
Quote from: X_RaY on 11/08/2016 02:20 pmIs there anyone who has study a half-sphere shaped resonator regarding the emdrive?In contrast to a parabolic one (where the focal depth for rays much shorter than the size of the structure itself was equal to the point where the baseplate was present).http://forum.nasaspaceflight.com/index.php?topic=39214.msg1607020#msg1607020 Now I did an FEA with the half-sphere shape. What I found is a massive fieldstrength, much higher than I ever have observed in the sims before. The Q should be very high.1) What is the numerical analysis package you are using ? (FEKO, etc.) 2) What numerical technique are you using to solve the equations? (Finite Element Method?, Boundary Element Method?, Finite Difference Method Space Domain?)?3) What is the type of solution method? A) Is it an eigensolution to the eigenvalue problem where there is no antenna in the model? B) Or a steady state solution using an antenna and a spectral method to obtain a solution? C) Or a transient solution using an antenna and a Finite Difference Time Domain to obtain a solution?D) If you used an antenna, with a spectral steady-state solution or a transient Finite-Difference-Time-Domain solution, what was the type of antenna and where was it located?4) What are the boundary conditions that you use in the model? Are you assuming a perfect conductor?If not, how are you modeling an imperfect conductor like copper?5) How is the quality factor (Q) calculated?6) How are eddy currents calculated in the model?Thanks
Is there anyone who has study a half-sphere shaped resonator regarding the emdrive?In contrast to a parabolic one (where the focal depth for rays much shorter than the size of the structure itself was equal to the point where the baseplate was present).http://forum.nasaspaceflight.com/index.php?topic=39214.msg1607020#msg1607020 Now I did an FEA with the half-sphere shape. What I found is a massive fieldstrength, much higher than I ever have observed in the sims before. The Q should be very high.
The White et al. 2016 paper (the leaked, non-peer reviewed version, which still can be downloaded from http://www.nextbigfuture.com/2016/11/new-nasa-emdrive-paper-shows-force-of.html):I haven't read a lot of discussion of the paper yet. Some remarks can be made, though, and questions asked. It looks like a solid piece of work, greatly admirable engineering work and clear discussion. We don't know from when this version is (the pdf I downloaded doesn't give a creation date, only 26 Aug 2016 as modification date). It doesn't look like two years of work to me (but probably they could not work full-time on it). I am a bit disappointed that they don't show results of other dielectric inserts (what they probably did).A few issues and questions:- I wonder whether switching direction in their way, with the whole RF stuff (amplifier etc) attached to the large endplate, is the best to do. As they write, they had retuning problems when using a 'split configuration mode'. But if you use a flexible cable, it should be possible to turn only the cavity by 180 degrees and leave the RF stuff at the same position and orientation.- Do I see a saturation effect around 60 W? See Figs. 13, 15 and 19. It does not seem to be so much work to perform, say, 100 measurements. Then they could have shown with statistics that there is a difference in force between the 60 W and the 80 W input, or not. Now that is not clear (their premise is probably that there SHOULD be a linear dependence on power: dangerous).- I am still a bit worried about the liquid metal contacts they use to supply the DC power to the torsion balance (many amps!). It is not likely that these will give rise to the signals they observe, but I haven't seen a test of their influence on the measurement.Maybe more later,Peter.
"According to Woodward, who saw a copy of the paper shortly after it had been accepted for peer review, the main difference between the accepted copy and the leaked early release is that the latter has way more theory trying to explain the results. Supposedly the AIAA would only accept the paper if White and his colleagues ditched the quantum vacuum theory and just published the results of their research without trying to explain it."http://motherboard.vice.com/read/the-fact-and-fiction-of-the-nasa-emdrive-paper-leak