Quote from: TheTraveller on 08/01/2015 04:07 am... She never mentions a dielectric. So it seems no dielectric was used by Prof Yang.Wrong. Yang explicitly mentions a dielectric in her original 2010 paper in Chinese.Perhaps you did not read this post: http://forum.nasaspaceflight.com/index.php?topic=37642.msg1411922#msg1411922, so I will make these points again one by one, and be more direct this time as to where you make mistakes:1) The equation you posted for Q is wrong, it is not the equation that Yang used. The equation you posted for Q does not make any sense. It never appears in Yang's original 2010 paper in Chinese.2) You posted an equation for Q that instead came from a very bad translation in Shawyer's website instead of coming from her original 2010 paper in Chinese. 3) The original paper in Chinese by Yang has the correct equation for Q.4) In the original paper in Chinese by Yang she uses tnδ and instead of tnd. tnδ means tangent delta (loss tangent) which is the material property for a dielectric loss, which reduces the Q. 5) In the original 2010 paper in Chinese by Yang she explicitly writes: "dielectric losses" instead of the badly translated "electric losses" that appears in the bad translationI don't know whether Yang did use or did not use dielectrics in any of her experiments, but what is undeniable from reading her 2010 paper in Chinese is that she clearly mentions dielectric losses explicitly and furthermore she goes further: she uses an equation for Q that takes into account dielectric losses. Why would Yang use an equation for Q that takes into account dielectric losses if she never used dielectrics or planned to use dielectric inserts?
... She never mentions a dielectric. So it seems no dielectric was used by Prof Yang.
This is the statement:腔体内充填的电介质损耗in:Applying Method of Reference 2 to Effectively Calculating Performance of Microwave Radiation ThrusterYang Juan,Yang Le,Zhu Yu,Ma NanJournal of Northwestern Polytechnical University, Dec. 2010, V01.28 No.6, page 810___________________________________PS: I'm glad that the NSF forum accepts Chinese characters! That makes this answer simple. Awesome.
Quote from: SeeShells on 07/29/2015 11:42 pmQuote from: deltaMass on 07/29/2015 11:32 pmIf I knew that...I'd have better answers!And if we knew more we would have a GUT down pat. I had a friend ask me today if it was even worth it, you know exploring the solar system because we had probes sent to all the planets and not much more needed to be done. The money could be spent here on earth feeding the hungry masses. I sent him this.http://www.space.com/30074-trillion-dollar-asteroid-2011-uw158-earth-flyby.html
Quote from: deltaMass on 07/29/2015 11:32 pmIf I knew that...I'd have better answers!And if we knew more we would have a GUT down pat.
If I knew that...I'd have better answers!
Quote from: WarpTech on 08/01/2015 05:42 amQuote from: deltaMass on 08/01/2015 05:14 amQuote from: WarpTech on 08/01/2015 04:44 amQuote from: Silversheep2011 on 08/01/2015 03:37 amrfmwguy.I'm thinking replace the magnetron [see attachment below looks the same] with a RF transistor as used herehttp://www.zdnet.com/article/freescales-radio-frequency-oven-the-end-of-the-microwave/maybe it runs with less heat loss?and runs cleaner r.f. waveshttp://www.freescale.com/webapp/video_vault/videoSummary.sp?code=RF-SAGE-VIDEO see 2.37They still require a heat sink. 3.7 deg. C/Watt is a lot of heat. These are also only good for about 200 to 400 mW per transistor, if you've got a good heat sink. If you want to get back up to 400W, you will need to parallel about a dozen of them on a well designed PC board, that is thermally conductive to the heatsink. At these frequencies, I have no idea how you would do that, or what proper design criteria are necessary for a microwave amplifier of sufficient power. ToddI take issue with your use of the arithmetic division operator.Nick picking again... oC/W. Not that - that you say you need "about a dozen" 400 mW transistors to get 400 Watts.
Quote from: deltaMass on 08/01/2015 05:14 amQuote from: WarpTech on 08/01/2015 04:44 amQuote from: Silversheep2011 on 08/01/2015 03:37 amrfmwguy.I'm thinking replace the magnetron [see attachment below looks the same] with a RF transistor as used herehttp://www.zdnet.com/article/freescales-radio-frequency-oven-the-end-of-the-microwave/maybe it runs with less heat loss?and runs cleaner r.f. waveshttp://www.freescale.com/webapp/video_vault/videoSummary.sp?code=RF-SAGE-VIDEO see 2.37They still require a heat sink. 3.7 deg. C/Watt is a lot of heat. These are also only good for about 200 to 400 mW per transistor, if you've got a good heat sink. If you want to get back up to 400W, you will need to parallel about a dozen of them on a well designed PC board, that is thermally conductive to the heatsink. At these frequencies, I have no idea how you would do that, or what proper design criteria are necessary for a microwave amplifier of sufficient power. ToddI take issue with your use of the arithmetic division operator.Nick picking again... oC/W.
Quote from: WarpTech on 08/01/2015 04:44 amQuote from: Silversheep2011 on 08/01/2015 03:37 amrfmwguy.I'm thinking replace the magnetron [see attachment below looks the same] with a RF transistor as used herehttp://www.zdnet.com/article/freescales-radio-frequency-oven-the-end-of-the-microwave/maybe it runs with less heat loss?and runs cleaner r.f. waveshttp://www.freescale.com/webapp/video_vault/videoSummary.sp?code=RF-SAGE-VIDEO see 2.37They still require a heat sink. 3.7 deg. C/Watt is a lot of heat. These are also only good for about 200 to 400 mW per transistor, if you've got a good heat sink. If you want to get back up to 400W, you will need to parallel about a dozen of them on a well designed PC board, that is thermally conductive to the heatsink. At these frequencies, I have no idea how you would do that, or what proper design criteria are necessary for a microwave amplifier of sufficient power. ToddI take issue with your use of the arithmetic division operator.
Quote from: Silversheep2011 on 08/01/2015 03:37 amrfmwguy.I'm thinking replace the magnetron [see attachment below looks the same] with a RF transistor as used herehttp://www.zdnet.com/article/freescales-radio-frequency-oven-the-end-of-the-microwave/maybe it runs with less heat loss?and runs cleaner r.f. waveshttp://www.freescale.com/webapp/video_vault/videoSummary.sp?code=RF-SAGE-VIDEO see 2.37They still require a heat sink. 3.7 deg. C/Watt is a lot of heat. These are also only good for about 200 to 400 mW per transistor, if you've got a good heat sink. If you want to get back up to 400W, you will need to parallel about a dozen of them on a well designed PC board, that is thermally conductive to the heatsink. At these frequencies, I have no idea how you would do that, or what proper design criteria are necessary for a microwave amplifier of sufficient power. Todd
rfmwguy.I'm thinking replace the magnetron [see attachment below looks the same] with a RF transistor as used herehttp://www.zdnet.com/article/freescales-radio-frequency-oven-the-end-of-the-microwave/maybe it runs with less heat loss?and runs cleaner r.f. waveshttp://www.freescale.com/webapp/video_vault/videoSummary.sp?code=RF-SAGE-VIDEO see 2.37
@SeeShells and @Rodal,The data you are referring to was something I generated after reading a post/paper by Dr. Rodal in which he discussed extending the Brady frustum, using the same big end diameter and the same taper angle, but extending until the small end diameter equalled 25% of the big end diameter. The views posted are for the start of the cavity, power on until some cycles later. We remarked at the time about the changing range of the signal causing color changes, but no one realized that I had discovered the first step in inventing the "flashy light thingee" used by the Men in Black.I have used time today to re-run that model generating what has become rather standard upload data, both csv files and png views, here: https://drive.google.com/folderview?id=0B1XizxEfB23tfkZVbi1MY2RQZmVkeEVHUmVfQkc3UEdlVkdOVXZENmFYbmg4czJUd1lqcDg&usp=sharingRead the data request file, where I blamed Rodal for asking for the data. I copied some data from my meep run log into the file giving basic cavity and run information. I did not use run logs back in mid June but it is the same model so today's run log data should be the same as was ran back in June. I don't recall where the 2.14 GHz center drive frequency number came from, perhaps it was Harminv.In any case, I hope this data tells us something, and Dr. Rodal, the complete set of 14 time slice csv files are there so you now have the data to calculate stresses. I'd be interested in seeing the result. Looks to me like zero force on the small end, but appearances can be deceiving.
@rfmwguy since it appears you can't run continuously for a prolonged period without reaching a critical heat regime, what's the plan?Are you going to implement a cooling system so you can run continuously, or used a reduced power level that involves the magnetron cycling off and on? If the later, how would you untangle the ramp-up, ramp-down seen in previous experiments from the magnetron cycles? It would see, to be difficult under those circumstances to have a very clean relationship between system on/off and measured thrust.
Quote from: rfmwguy on 08/01/2015 02:09 amQuote from: deltaMass on 08/01/2015 02:01 amAfter seeing that vid I'm adding another artifact candidate - steam jet.I agree, that's why I want to do a lot of thermal testing of hotspots. The machine screw head was way hotter than surrounding metal. I suspect some rf leakage between copper clad end plates. Simple fix I'll mess with over the weekend. Thermal issues need to be addressed well ahead of torsion or balance testing imho.Use a heatsink that has radial fins, so orientation doesn't matter. As it is now, the fins are in the wrong direction. The fins are flat with the openings on the sides. The opening should be up and down, so convention will cool it, pulling cool air in from the bottom. The airflow is blocked. Granted, this will never work in a vacuum chamber without liquid cooling or a very large mass to dump heat into.Todd
Quote from: deltaMass on 08/01/2015 02:01 amAfter seeing that vid I'm adding another artifact candidate - steam jet.I agree, that's why I want to do a lot of thermal testing of hotspots. The machine screw head was way hotter than surrounding metal. I suspect some rf leakage between copper clad end plates. Simple fix I'll mess with over the weekend. Thermal issues need to be addressed well ahead of torsion or balance testing imho.
After seeing that vid I'm adding another artifact candidate - steam jet.
Just a random thought @rfmwguy.I know you don't want to blow air over the fins, but would you be able to calibrate the force balance if you used your wife's vacuum sweeper hose to suck air across them? Maybe a longer hose so it exhausted outside? Maybe an inlet of some sort to channel the moving air to minimize stray air currents?Maybe a liquid cooling loop. The lag in the temperature readings after turn-off seemed to indicate that the center of the magnetron got much hotter than the fins where you were measuring temperature.
Actually I got the impression from the vid that the heat capacity of the magnetron is quite low - it lost heat very rapidly after turn off. Oddly perhaps, the same could not be said of the frustum. Or perhaps these observations are due to vid editing messing with the observed timeline?
Doing impedance matchingAll frustums need to be impedance matched to the Rf source. Doesn't matter if the Rf source is Magnetron or Rf amp.Typical way to do that is with a 2 or 3 stub tuner.Here is the 3 stub coax tuner I will be using between my Rf amp and the frustum.Waveguide mounted 2 and 3 stub tuners are also available. Of course to use them your magnetron needs to couple Rf energy to the frustum via a waveguide. I have no idea how to impedance match a direct coupled magnetron and frustum. Anybody know how to do this? As far as I can find out, only Iulian used a direct couple and his data is highly questionable. Shawyer in his 1st Experimental EMDrive, 2nd Demonstrator EMDrive and Tajmar's EMDrive used a waveguide between the frustum and the magnetron. I know in the Demonstrator waveguide there was a 2 stub impedance matching setup. I assume there was that capability in the Experimental and Tajmar EMDrives.So DIY EMDrive builders you need to design in a way to tune the impedance match between your frustum and the Rf source.
{snip}
The main thing I'd like to know about Yang is whether anybody can verify her experimental data at her facility. Neutral parties, I mean.
Quote from: aero on 08/01/2015 12:29 am@SeeShells and @Rodal,The data you are referring to was something I generated after reading a post/paper by Dr. Rodal in which he discussed extending the Brady frustum, using the same big end diameter and the same taper angle, but extending until the small end diameter equalled 25% of the big end diameter. The views posted are for the start of the cavity, power on until some cycles later. We remarked at the time about the changing range of the signal causing color changes, but no one realized that I had discovered the first step in inventing the "flashy light thingee" used by the Men in Black.I have used time today to re-run that model generating what has become rather standard upload data, both csv files and png views, here: https://drive.google.com/folderview?id=0B1XizxEfB23tfkZVbi1MY2RQZmVkeEVHUmVfQkc3UEdlVkdOVXZENmFYbmg4czJUd1lqcDg&usp=sharingRead the data request file, where I blamed Rodal for asking for the data. I copied some data from my meep run log into the file giving basic cavity and run information. I did not use run logs back in mid June but it is the same model so today's run log data should be the same as was ran back in June. I don't recall where the 2.14 GHz center drive frequency number came from, perhaps it was Harminv.In any case, I hope this data tells us something, and Dr. Rodal, the complete set of 14 time slice csv files are there so you now have the data to calculate stresses. I'd be interested in seeing the result. Looks to me like zero force on the small end, but appearances can be deceiving.A short heads up on this run (NASA Brady et.al. geometry extended to near the apex of the cone):1) Non-symmetric placement of antenna, very offset from middle2) Amplitude of response is very low: not a good resonance. It shows fractal numerical artifacts due to very low amplitude.3) Forces at both ends are very low. Force at small end close to zero. Stress distribution at big end very low and very asymmetric.Suggestion: may need to run again, at an excitation frequency for which we know (from other calculations) that there is a good resonant response and with an antenna located on the axis axi-symmetry. If run again, it may be better to do it based on Yang/Shell geometry extended to near the apex of the cone, to model the geometry she intends to test.