I was one of a few people trying to guestimate the small diameter of Shawyer's Demo. Yes, it was done by eye, or using tools attempting to match the profile of the cavity, which was by eye. For the error in small diameter you should fine a corresponding error in height as the taper is easy to match and the big diameter is given. These estimates were made before we had looked into the design factor so that approach wasn't considered. Neither did we have a good handle on cut-off or guide frequency. Time marches on, and you have somewhat better information now.I suggest you go with the design factor calculation and adjust the height accordingly using the taper and the large and small diameters to calculate height. That is, of course if the numbers you derive will fit within the cavity as illustrated by the photographs. That is a simple sanity check. Others may have different and better justified opinions.

Asymmetry 101.Throw a ball in the +x direction, perfect reflection from the front wall to hit the rear wall and be absorbed.Throw: -p to floor through feetBounce: +2p to front wallAbsorb: -p to rear wallSum of momenta = 0Conclusion: asymmetry doesn't make floobie dust.

This is a 3D model of the "Shawyer Demo". I built it as close as I can figure that it has to be and examining the several photographs that have been shared here. The dimensions are from published values.rfFrequency=2.45*10^9;cavityLength=0.345;bigDiameter=0.28;smallDiameter= 0.128853power = 421 to 1200Q = 45000(measured force = 102.30 milliNewtons only reported for 421 watts, 243 milliNewtons/kW )measured ForcePerPowerInput = 80 to 243Force/PowerInput of a Photon Rocket =0.003337measured ForcePerPowerInput to the one of a photon rocket =23,980 to 72,830While this is a crude SketchUp model if anyone wants the model I'm happy to share it.

can someone explain in normal people terms were is the recoil going from turning on the microwave?shouldn't the metal box push on the microwave just as much as the microwave pushes on the metal box?also, it gets really hot... could the recoil just be delayed?

A 160 mm diameter experimental thruster, operating at 2.45 GHz was designed and built. (see fig 6) The design factor, calculated from as-built measurements of the thruster geometrywas 0.497. An unloaded Q of 5,900 was measured. [/b].

Quote from: snow on 05/20/2015 09:19 AMcan someone explain in normal people terms were is the recoil going from turning on the microwave?shouldn't the metal box push on the microwave just as much as the microwave pushes on the metal box?also, it gets really hot... could the recoil just be delayed?Shawyer's explanation is that the waves bounce back and forth across the device.The speed of the waves depends upon the shape of the container (the container is acting as a wave-guide, which reduces the propagation speed to be less than C). Shawyer asserts that the momentum change is thereby asymmetric, due to the differing effective impact speeds. Note that the wider physics community do not agree with this analysis, although I do not understand the details.However, there are other theories, in particular Dr.White at NASA thinks that the EM fields from the standing waves are interacting with quantum 'virtual particles', effectively pushing off these. There are problems to do with special relativity and conservation of energy that would seem to make this unlikely unless you go and revive some very old theories of the aether and absolute reference frames, which are very marginal (special relativity has been well tested and aether theories abandoned as unproductive).Another theory that allows breaking of local conservation of momentum and which _is consistent with observations is Woodward 'Mach' effects. These relate to accelerating bodies which are changing in internal energy levels. The momentum is effectively transferred to all other bodies in the universe, at the speed of light. Attempts to produce or measure Mach effects have thus far failed, but there are reasonable theoretic reasons to believe they might be possible (they help to explain inertia and provide a preferred reference frame which special relativity lacks). I don't think anyone is explaining the EM drive in terms of this, however.

I have recalculated the small diameter, for Shawyer's EXPERIMENTAL THRUSTER using Shawyer's paper http://www.emdrive.com/IAC-08-C4-4-7.pdf, see page 6, where Shawyer states Quote from: ShawyerA 160 mm diameter experimental thruster, operating at 2.45 GHz was designed and built. (see fig 6) The design factor, calculated from as-built measurements of the thruster geometrywas 0.497. An unloaded Q of 5,900 was measured. [/b]. (Unfortunately, Shawyer does not provide the small diameter or the cavity length in his paper)I have used this information bigDiameter = 0.16 m;f = 2.45*10^9 Hz;cst = 1.7062895542683174; cM = 299705000 m/s (speed of light in air);Design Factor = 0.497, and inverted the equation for the Design Factor (see: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1374110#msg1374110 ) to obtain the following correct dimension:small diameter = 0.1025 m SHAWYER's EXPERIMENTAL THRUSTER(obtained from the Design Factor, bigDiameter and frequency provided by Shawyer)

Ha, that table was from you - "Here is a comparison of reported measurements for EM Drives and for the latest report by Fearn, Zachar, Woodward & Wanser."

Notice that while our original interpretation of Shawyer's Design Factor took into account all vital dimensions: the small diameter, the big diameter and the cavity length (from which the truncated cone angle can be obtained), the latest interpretation of Shawyer's Design Factor, completely ignores the cavity length. This interpretation of the Design Factor, worked out with TheTraveller shows that Shawyer calculates the thrust force on an EM Drive to be completely independent of the cavity length: it doesn't make a difference whether the cavity has zero length or whether the cavity has a length of 50,000 light years from here to the nearest magnetar. It doesn't make a difference whether the truncated cone has a cone angle approaching zero (like a cylinder) or the truncated cone has a cone angle of 45 degrees. While such a Design Factor, and hence such a formula for thrust force, that completely ignores the cavity length does not make physical sense to me, we have reproduced it, because if that is the formula that Shawyer used (however questionable it may be), that is the formula we need to unlock the geometrical dimension of the small diameter that Shawyer has not directly, explicitly provided. Please note that Shawyer has not provided the length of the cavity either, which is consistent with his formula that ignores the cavity length. Therefore, notice that Shawyer's cavity lengths are being estimated and so anyone using them is forewarned to use them at their own peril.

...It is not correct to state Shawyer ignores the length. He has stated many times that the applied Rf must cause frustum length resonance. Without this resonance there will be little thrust.I understand you focus on the equations but maybe spend some time reading his words as per the attached. Has he described how to calc the end plate separation versus external Rf to obtain resonance? No he has not. Is that a crime? No it is not. SPR is in business to make money and giving away all their "Secret Squirrel Secret Sauce" may not be in their best interest. If Shawyer does not fully disclose, that is his right and you have NO right to call him out for doing so.

Quote from: TheTraveller on 05/20/2015 12:50 PM...It is not correct to state Shawyer ignores the length. He has stated many times that the applied Rf must cause frustum length resonance. Without this resonance there will be little thrust.I understand you focus on the equations but maybe spend some time reading his words as per the attached. Has he described how to calc the end plate separation versus external Rf to obtain resonance? No he has not. Is that a crime? No it is not. SPR is in business to make money and giving away all their "Secret Squirrel Secret Sauce" may not be in their best interest. If Shawyer does not fully disclose, that is his right and you have NO right to call him out for doing so.Sir, I referred exclusively to Shawyer's mathematical equations, and the fact that the geometrical dimensions of the experiments where not reported in his papers. It is expected that the geometrical dimensions should be disclosed in experimental papers, and it is pro forma in peer-review to argue mathematical equations in papers.Sir, this thread is not a thread to deal with personalities, and much less is a thread to defend the business interests of personalities.Please try to adopt an objective, and skeptical attitude in analyzing the EM Drive technical subject and try not to personalize it.