Quote from: zellerium on 05/13/2015 05:20 pmQuote from: zen-in on 05/13/2015 04:55 pmThere was a lot of discussion about the EW measurement methods on pages 62 - 70 of this thread. The actual displacement of the TP when RF power is applied is very miniscule. The illustration below shows a calibration pulse next to the distance measurement scale. The end of the TP has moved just 1 micrometer. Earlier in this thread I did a rough calculation of a laser - mirror displacement measurement setup based on this small displacement:A problem with this experiment is the extremely small displacements that indicate a thrust. A displacement of 4 micrometers has the TP beam move through just 1.7 arcSec. of rotation. If a laser beam was reflected off the LDS moving mirror and someone was 1 km away they would see the reflected dot move just a few mm. The LDS is just as sensitive to angular changes of the mirror. An experiment of this type requires repeatable, consistent results with a signal level far above what is currently seen to provide proof of this proposed theory of its operation.Is that displacement assuming we will get EW's thrust values? If we use a microwave oven magnetron putting out 1 kW I hope we get much higher thrust values than EW who used only 17 ~ 50 W. I see your concern, but without a low thrust torsion pendulum it seems near impossible to measure 20~100 micoNewtons Cavendish pendulum.
Quote from: zen-in on 05/13/2015 04:55 pmThere was a lot of discussion about the EW measurement methods on pages 62 - 70 of this thread. The actual displacement of the TP when RF power is applied is very miniscule. The illustration below shows a calibration pulse next to the distance measurement scale. The end of the TP has moved just 1 micrometer. Earlier in this thread I did a rough calculation of a laser - mirror displacement measurement setup based on this small displacement:A problem with this experiment is the extremely small displacements that indicate a thrust. A displacement of 4 micrometers has the TP beam move through just 1.7 arcSec. of rotation. If a laser beam was reflected off the LDS moving mirror and someone was 1 km away they would see the reflected dot move just a few mm. The LDS is just as sensitive to angular changes of the mirror. An experiment of this type requires repeatable, consistent results with a signal level far above what is currently seen to provide proof of this proposed theory of its operation.Is that displacement assuming we will get EW's thrust values? If we use a microwave oven magnetron putting out 1 kW I hope we get much higher thrust values than EW who used only 17 ~ 50 W. I see your concern, but without a low thrust torsion pendulum it seems near impossible to measure 20~100 micoNewtons
There was a lot of discussion about the EW measurement methods on pages 62 - 70 of this thread. The actual displacement of the TP when RF power is applied is very miniscule. The illustration below shows a calibration pulse next to the distance measurement scale. The end of the TP has moved just 1 micrometer. Earlier in this thread I did a rough calculation of a laser - mirror displacement measurement setup based on this small displacement:A problem with this experiment is the extremely small displacements that indicate a thrust. A displacement of 4 micrometers has the TP beam move through just 1.7 arcSec. of rotation. If a laser beam was reflected off the LDS moving mirror and someone was 1 km away they would see the reflected dot move just a few mm. The LDS is just as sensitive to angular changes of the mirror. An experiment of this type requires repeatable, consistent results with a signal level far above what is currently seen to provide proof of this proposed theory of its operation.
Quote from: TheTraveller on 05/13/2015 08:28 amEmail received from Roger Shawyer in regard to a question to verify if Dr. Rodal's Df excel equation is correct.Shawyer also cautions, very strongly, on the dangers of working with high power microwave systems.I obtained the following expression for the frequency at which my interpretation of Shawyer's Design Factor blows up.frequencySingularity =cMedium* Sqrt[ (4 cavityLength^2 - bigDiameter smallDiameter)] /(2*cavityLength*Sqrt[bigDiameter*smallDiameter] )This can be simplified as follows:Defining:cutOffWavelength = 2* cavityLength (this was assumed, and built-in in my equation, other expressions for cutOffWavelength can be used alternatively)geometricAverageDiameter = Sqrt[bigDiameter*smallDiameter]thenfrequencySingularity = cMedium* Sqrt[ (cutOffWavelength^2 - geometricAverageDiameter^2)]) /(cutOffWavelength * geometricAverageDiameter)
Email received from Roger Shawyer in regard to a question to verify if Dr. Rodal's Df excel equation is correct.Shawyer also cautions, very strongly, on the dangers of working with high power microwave systems.
Quote from: TheTraveller on 05/13/2015 06:05 pm...Question? What if cavity length is not the biggest cavity dimension? Should not the biggest cavity dimension be used, as I have read in the microwave waveguide theory stuff I'm researching?Roughly correct (the diameter and the length have different factors), would you like me to give you an equation for the Design Factor in that case?
...Question? What if cavity length is not the biggest cavity dimension? Should not the biggest cavity dimension be used, as I have read in the microwave waveguide theory stuff I'm researching?
...Mmm, yes, for having "probed" that specific aspect of the pendulum system used at EagleWorks, their design is quite stiff : produces small deviation wrt forces. The forces are small and this relatively high stiffness (due to flexure bearings as pivots) doesn't help. Rambling again : the exact apparent stiffness (in µN/µm at end of arm) at EW is a poorly characterised aspect of the experiments, taking the calibration pulses as a reliable starting point gives between 9µN/µm to 40µN/µm across the various released charts, and all are in contradiction with both flexure bearings ratings and harmonic oscillation period (when visible, on underdamped plots). Appears the measures on the vertical scale of plots show much higher stiffness than it should be (too low displacement readings ?).Anyway, there is no reason not to go with a much lower stiffness system, or no stiffness at all (no position restoring force) and record mm or cm displacements (linear or angular) as thrust accelerates the mass (as in Shawyer).
Quote from: TheTraveller on 05/13/2015 06:05 pmQuestion? What if cavity length is not the biggest cavity dimension? Should not the biggest cavity dimension be used, as I have read in the microwave waveguide theory stuff I'm researching?And weren't there earlier murmurings that a domed end-plate should be used on the large end of the frustum instead of a flat-plate? Wouldn't you need to measure length to the center of the dome, and not the edge?
Question? What if cavity length is not the biggest cavity dimension? Should not the biggest cavity dimension be used, as I have read in the microwave waveguide theory stuff I'm researching?
I don't dispute the need for a low thrust torsion pendulum. I'm just stating that a reflected laser beam can't provide the required resolution. The measurement sensor EW used could measure small displacements with more precision than a reflected laser beam. Microwave Oven magnetrons are hazardous and potentially lethal devices when removed from an oven. For FCC compliance and safety reasons it should be enclosed by a 6-side Faraday cage with a power interlock. Even that may not be enough to satisfy the FCC if interference is reported.
Quote from: TheTraveller on 05/13/2015 06:22 pmQuote from: sghill on 05/13/2015 06:15 pmAnd weren't there earlier murmurings that a domed end-plate should be used on the large end of the frustum instead of a flat-plate? Wouldn't you need to measure length to the center of the dome, and not the edge?From what I can see, Shawyer assumes the end plates are spherical and the length between them, measured relative to a line from the vertex of the cone are the same at all points.Which means cavities with flat end plates will not achieve the calculated Df nor have a narrow resonant frequency band not have in phase end plate reflections. Is why if you desire to have a high Q cavity, curved end plates are required.Which is what will happen with my Flight Thruster replication, which will have a variable frequency Rf generator to hunt for and find the best operational frequency.Thank you for the response.I guess that anecdotally lends credence to my previously-stated suspicion (from God-knows how many months back ) that the bottom ring on this thruster is a painted rubber gasket that acts as a footer for the domed bottom-plate it is protecting (even though the visible top plate is flat). The cracked paint on it is a dead-giveaway that it's a spongy material like rubber or silicon- perfect for a footer.
Quote from: sghill on 05/13/2015 06:15 pmAnd weren't there earlier murmurings that a domed end-plate should be used on the large end of the frustum instead of a flat-plate? Wouldn't you need to measure length to the center of the dome, and not the edge?From what I can see, Shawyer assumes the end plates are spherical and the length between them, measured relative to a line from the vertex of the cone are the same at all points.Which means cavities with flat end plates will not achieve the calculated Df nor have a narrow resonant frequency band not have in phase end plate reflections. Is why if you desire to have a high Q cavity, curved end plates are required.Which is what will happen with my Flight Thruster replication, which will have a variable frequency Rf generator to hunt for and find the best operational frequency.
And weren't there earlier murmurings that a domed end-plate should be used on the large end of the frustum instead of a flat-plate? Wouldn't you need to measure length to the center of the dome, and not the edge?
Today i did the first test with the Emdrive (microwave oven magnetron and cooper frustum) The setup (magnetron and frusum) was suspended in a pendulum. I applied power for 40 Seconds with no visible thrust. Tomorrow will will try again with the magnetron on the small side. You have any suggestion for what should be the distance from the small side?After this i will adjust the power to the filament of magnetron and the frequency.To fine adjust the frequency i thought i can put 2 coils over the magnetron magnets to modify the magnetic field.My website;http://www.masinaelectrica.com/emdrive-independent-test/
As an added bonus, sticking with the dimensions provided by Eagleworks allows folks to use their COMSOL plots. While this cavity design might not be the optimal shape/size for max thrust, Paul March has provided potential replicators with an arsenal of very useful data on this thread applicable to those particular dimensions. Quality useful info like this:http://forum.nasaspaceflight.com/index.php?topic=36313.msg1327467#msg1327467http://forum.nasaspaceflight.com/index.php?topic=36313.msg1333246#msg1333246
Quote from: Mulletron on 05/13/2015 07:10 pmAs an added bonus, sticking with the dimensions provided by Eagleworks allows folks to use their COMSOL plots. While this cavity design might not be the optimal shape/size for max thrust, Paul March has provided potential replicators with an arsenal of very useful data on this thread applicable to those particular dimensions. Quality useful info like this:http://forum.nasaspaceflight.com/index.php?topic=36313.msg1327467#msg1327467http://forum.nasaspaceflight.com/index.php?topic=36313.msg1333246#msg1333246As I understand it, your cavity is same as that one? Correct?Did you find the same 2,445GHz cavity resonance as Paul did? If not what resonance frequency did you find?
Quote from: zen-in on 05/13/2015 05:36 pmIt seems that the phase modulation has led to an increased efficiency, so I have been considering splitting the coax signal to two different ports on the frustum for equal power signals at different phases. However this is a recent idea I have yet to research and would only be something we try after the simple setup.Yes, great idea! Do you think it's a good idea to see if you can also provide phase shifting on the second injected signal?I'm still working out this but the preliminary scan into the papers forwarded by Rodal it looks very good but other verification is needed as my math is rusty and my eraser is getting worn. http://forum.nasaspaceflight.com/index.php?topic=36313.msg1373661#msg1373661This from this paper recently brought up by Todd (hat tip to WarpTech), which confirms the validity of SeeShells suggestion:http://www.radioeng.cz/fulltexts/2011/11_02_472_478.pdfAttenuation in Rectangular Waveguides with Finite Conductivity WallsKim Ho YEAP, Choy Yoong THAM, Ghassan YASSIN, Kee Choon YEONGRADIOENGINEERING, VOL. 20, NO. 2, JUNE 2011Quote from: Kim Ho YEAP, Choy Yoong THAM, Ghassan YASSIN, Kee Choon YEONGAn important consequence of thiswork is the demonstration that the loss computed for degeneratemodes propagating simultaneously is not simplyadditive. In other words, the combined loss of two co-existingmodes is higher than adding the losses of two modespropagating independently. This can be explained by themode coupling effects, which is significant when the phaseconstants of two propagating modes are different yet veryclose.
It seems that the phase modulation has led to an increased efficiency, so I have been considering splitting the coax signal to two different ports on the frustum for equal power signals at different phases. However this is a recent idea I have yet to research and would only be something we try after the simple setup.
Quote from: Iulian Berca on 05/13/2015 07:07 pmToday i did the first test with the Emdrive (microwave oven magnetron and cooper frustum) The setup (magnetron and frusum) was suspended in a pendulum. I applied power for 40 Seconds with no visible thrust. Tomorrow will will try again with the magnetron on the small side. You have any suggestion for what should be the distance from the small side?After this i will adjust the power to the filament of magnetron and the frequency.To fine adjust the frequency i thought i can put 2 coils over the magnetron magnets to modify the magnetic field.My website;http://www.masinaelectrica.com/emdrive-independent-test/You could modify the cavity so that it's resonant frequency can be adjusted. I don't know how easy it would be for you to do this but you could add an interior plate on the small end that can be moved. A couple of copper tubes soldered to the outside of the small end would act as guides for plastic rods connected to the interior plate. Then just move the plate a little bit at a time between tests. Eventually you will reach a resonance point. BTW how hot does the cavity get? It doesn't seem like the magnetron is overheating at all. Maybe it is operating at a low power.