Any resemblance with existing or future device(s) is purely coincidental.Made with MEEP. Does not use the correct frequencies, material, etc. but looks cute.
Quote from: frobnicat on 05/13/2015 06:02 pm...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).What measured force at NASA Eagleworks would be high enough to give confidence in the force, in your opinion?Or there would still be a problem in your opinion with higher measured forces and higher measured displacements, as long as the stiffness remains in that range?For example would a measured force of 200 µN and a measured displacement of 20 µm giving 10 µN/µm stiffness still lack confidence in your opinion ?(200 µN is twice the minimum of NASA Glenn's threshold force 100 µN stipulated for measuring the EM Drive)
...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).
It appears to be different to Dr. Rodal's Df equation as there are no references, that I know of, to cavity length and focuses on the wavelengths (Lambda g1 & Lambda g2) at the 2 end plates.
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.
An 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.
Quote from: TheTravellerIt appears to be different to Dr. Rodal's Df equation as there are no references, that I know of, to cavity length and focuses on the wavelengths (Lambda g1 & Lambda g2) at the 2 end plates.How's that again? There is only one wavelength in the cavity - that of the RF.
Quote from: deltaMass on 05/13/2015 11:47 pmQuote from: TheTravellerIt appears to be different to Dr. Rodal's Df equation as there are no references, that I know of, to cavity length and focuses on the wavelengths (Lambda g1 & Lambda g2) at the 2 end plates.How's that again? There is only one wavelength in the cavity - that of the RF.Cavity wavelength varies depending on the cavity dimensions.http://www.microwaves101.com/encyclopedias/waveguide-mathematics
Quote from: TheTraveller on 05/13/2015 11:53 pmQuote from: deltaMass on 05/13/2015 11:47 pmQuote from: TheTravellerIt appears to be different to Dr. Rodal's Df equation as there are no references, that I know of, to cavity length and focuses on the wavelengths (Lambda g1 & Lambda g2) at the 2 end plates.How's that again? There is only one wavelength in the cavity - that of the RF.Cavity wavelength varies depending on the cavity dimensions.http://www.microwaves101.com/encyclopedias/waveguide-mathematicsIndeed. The increasing confinement of a narrowing waveguide (convergent) produces a widening wavelength and a decrease of the group velocity. Conversely, a widening waveguide (divergent) produces a narrowing wavelength and an increase of the group velocity.
Quote from: TheTraveller on 05/14/2015 12:01 amQuote from: flux_capacitor on 05/13/2015 11:56 pmQuote from: TheTraveller on 05/13/2015 11:53 pmQuote from: deltaMass on 05/13/2015 11:47 pmQuote from: TheTravellerIt appears to be different to Dr. Rodal's Df equation as there are no references, that I know of, to cavity length and focuses on the wavelengths (Lambda g1 & Lambda g2) at the 2 end plates.How's that again? There is only one wavelength in the cavity - that of the RF.Cavity wavelength varies depending on the cavity dimensions.http://www.microwaves101.com/encyclopedias/waveguide-mathematicsIndeed. The increasing confinement of a narrowing waveguide (convergent) produces a widening wavelength and a decrease of the group velocity. Conversely, a widening waveguide (divergent) produces a narrowing wavelength and an increase of the group velocity.The different wavelengths at the big & small ends, due to the different diameters, are what drives Shawyers Df equation.In fact they are what cause the end plate force differentials that drive the EM Drive.Notice that the expression you have posted above, as defined by Shawyer blows up (goes to infinity) for the denominator going to zero. This occurs for lambda0 = Sqrt[lambdag1*lambdag2]or equivalentlycutOffWavelength = Sqrt[lambdag1*lambdag2]same condition I have above in my message. _________________________________________Disclaimer: I don't agree with the description above (since Shawyer's uses a lot of unstated engineering approximations whose validity neither he or anyone else has proven) . I would instead write: according to Shawyer "they are what cause the end plate force differentials that drive the EM Drive."
Quote from: flux_capacitor on 05/13/2015 11:56 pmQuote from: TheTraveller on 05/13/2015 11:53 pmQuote from: deltaMass on 05/13/2015 11:47 pmQuote from: TheTravellerIt appears to be different to Dr. Rodal's Df equation as there are no references, that I know of, to cavity length and focuses on the wavelengths (Lambda g1 & Lambda g2) at the 2 end plates.How's that again? There is only one wavelength in the cavity - that of the RF.Cavity wavelength varies depending on the cavity dimensions.http://www.microwaves101.com/encyclopedias/waveguide-mathematicsIndeed. The increasing confinement of a narrowing waveguide (convergent) produces a widening wavelength and a decrease of the group velocity. Conversely, a widening waveguide (divergent) produces a narrowing wavelength and an increase of the group velocity.The different wavelengths at the big & small ends, due to the different diameters, are what drives Shawyers Df equation.In fact they are what cause the end plate force differentials that drive the EM Drive.
...Will ask Shawyer how SPR calculates big and small end wavelengths Lambda g1 and g2. If he shares that info, then we will have eliminated one unknown. I dislike guessing and dislike even more to reinvent the wheel especially when it involves making actual hardware. Playing mind games or with excel is different. There we can play a bit. But building hardware is serious business. I will do what ever is necessary to reduce uncertainty about operational parameters before the cavity build starts.
Quote from: TheTraveller on 05/14/2015 12:30 am...Will ask Shawyer how SPR calculates big and small end wavelengths Lambda g1 and g2. If he shares that info, then we will have eliminated one unknown. I dislike guessing and dislike even more to reinvent the wheel especially when it involves making actual hardware. Playing mind games or with excel is different. There we can play a bit. But building hardware is serious business. I will do what ever is necessary to reduce uncertainty about operational parameters before the cavity build starts.Writing technical papers is just as much serious business. I also dislike guessing. Readers shouldn't have to guess what an author means when the author submits a "theory paper."If you have to ask Shawyer how he defined something in his papers is admitting that in your view his papers are insufficiently clear for you. One thing for sure: Shawyer never stated in his papers how he defines the cut-off frequency. If the cut-off frequency is to be based on the truncated cone cut-off frequency (and not an approximation) one then has to run a a numerical solution (an eigenvalue problem) to obtain the cut-off frequency.That's a small part of the reason why the engineering/scientific community has issues with his "theory paper". The biggest part is that he makes a large range of assumptions that are not clearly stated and are not clearly supported (certainly his reference to Cullen's paper does not support his Design Factor).
Doesn't that mean that it blows up for a cylindrical cavity? Yes. And for what other conditions does it blow up? Lambda02 = Lambdag1 * Lambdag2 : I forget which one is the big end but it blows up wheneverLambdag-small = Lambda02/Lambdag-bigI agree that the papers would be far more enlightening if the likelihood of such an occurrence were explained. And so would this forum for that matter.
First people are saying that the big end has a smaller lambda than the small end, and then other people say the opposite. Can't be bothered assembling the quotes.In any case, if lambda1 < lambda2 (whichever ends they represent), I am still asking if the following is truelambda1 <= lambda0 <= lambda2