Quote from: WarpTech on 08/07/2015 11:36 pmQuote from: frobnicat on 08/07/2015 10:41 pmNot coming from the RF world, I wonder why this whole discussion about Q can't settle on Q=2*π*energy_stored/energy_dissipated_per_cycle as a standard. Out of curiosity, isn't it possible to switch off a RF source fast enough (a few cycles) and get this Q value by observing only the time constant of the decay of amplitude with a minimally invasive probe ?BTW, not wanting to sound insistent but there is no answer to my questions about the relation of Q and "losses per round trip" (in the context of a linear resonant set up). If I am making a mistake by thinking "number of bounces" when hearing Q, then I'm not the only one : Think of it like the number of times a photon bounces inside a mirrored cavity. A clarification might be useful.My conjecture on this would be that, a small cone angle will cause more bounces and a higher Q. However, my feeling is that as the wave propagates from the small end to the big end, it is reflecting off the side walls. Each reflection off the side walls imparts a tiny bit of momentum to the frustum. So the more bounces off the side walls (not the end plates) will produce more thrust. This means that a slower group velocity, bouncing over a longer period of time, would give higher thrust. This leads to the idea that the frustum should be shaped more like a trombone with a long throat. But... none of the theories so far support this idea, but none have tried either.ToddTodd, but the axial force component due to the side walls equals Sin[theta]*SideWallForce, where theta is the cone half-angle. For theta = 0 ( a cylinder) the axial component due to the SideWallForce is Sin[0]*SideWallForce=0, it is zero no matter how large is the SideWallForce. For small theta, the SideWallForce axial component is very low. So, even if one grants you that the SideWallForce may be larger for small cone angle, the axial component is small. Comments?
Quote from: frobnicat on 08/07/2015 10:41 pmNot coming from the RF world, I wonder why this whole discussion about Q can't settle on Q=2*π*energy_stored/energy_dissipated_per_cycle as a standard. Out of curiosity, isn't it possible to switch off a RF source fast enough (a few cycles) and get this Q value by observing only the time constant of the decay of amplitude with a minimally invasive probe ?BTW, not wanting to sound insistent but there is no answer to my questions about the relation of Q and "losses per round trip" (in the context of a linear resonant set up). If I am making a mistake by thinking "number of bounces" when hearing Q, then I'm not the only one : Think of it like the number of times a photon bounces inside a mirrored cavity. A clarification might be useful.My conjecture on this would be that, a small cone angle will cause more bounces and a higher Q. However, my feeling is that as the wave propagates from the small end to the big end, it is reflecting off the side walls. Each reflection off the side walls imparts a tiny bit of momentum to the frustum. So the more bounces off the side walls (not the end plates) will produce more thrust. This means that a slower group velocity, bouncing over a longer period of time, would give higher thrust. This leads to the idea that the frustum should be shaped more like a trombone with a long throat. But... none of the theories so far support this idea, but none have tried either.Todd
Not coming from the RF world, I wonder why this whole discussion about Q can't settle on Q=2*π*energy_stored/energy_dissipated_per_cycle as a standard. Out of curiosity, isn't it possible to switch off a RF source fast enough (a few cycles) and get this Q value by observing only the time constant of the decay of amplitude with a minimally invasive probe ?BTW, not wanting to sound insistent but there is no answer to my questions about the relation of Q and "losses per round trip" (in the context of a linear resonant set up). If I am making a mistake by thinking "number of bounces" when hearing Q, then I'm not the only one : Think of it like the number of times a photon bounces inside a mirrored cavity. A clarification might be useful.
http://www.ustream.tv/channel/em-drive-experimentI am live on chat now at this address. You will need to create a free ustream account to post chat messages to me.There is about a 30 second delay, be patient.It is now 8:09 PM EST, I will keep it live and start about 8:20 PM to give people a chance to get there.There will be some ustream sponsored commercials, be patient...its free streaming.Chat with you in about 8 minutes.
Quote from: rfmwguy on 08/08/2015 12:12 amhttp://www.ustream.tv/channel/em-drive-experimentI am live on chat now at this address. You will need to create a free ustream account to post chat messages to me.There is about a 30 second delay, be patient.It is now 8:09 PM EST, I will keep it live and start about 8:20 PM to give people a chance to get there.There will be some ustream sponsored commercials, be patient...its free streaming.Chat with you in about 8 minutes.YOU ROCK! Couldn't login for whatever reason. But no questions.Shell
Thinking about the ongoing controversy regarding TheTraveller's and Shawyer's theory raises a question for me. Please forgive if this has been addressed in one of the earlier threads.If Shawyer's theory is wrong then is Cullen's eqn 15 also incorrect?? Eqn 15 seems to be the bedrock of the theory (the bible they punch ).I am trying to unpack the controversy a bit from the recent standard of "the physics/theory is wrong".
Quote from: demofsky on 08/07/2015 06:49 pmThinking about the ongoing controversy regarding TheTraveller's and Shawyer's theory raises a question for me. Please forgive if this has been addressed in one of the earlier threads.If Shawyer's theory is wrong then is Cullen's eqn 15 also incorrect?? Eqn 15 seems to be the bedrock of the theory (the bible they punch ).I am trying to unpack the controversy a bit from the recent standard of "the physics/theory is wrong".Cullen is discussing a constant cross section wave guide the resonator that Shawyer is trying to analyze is a more complicated shape so Cullen's equation may or may not be applicable. There is probably something wrong with Shawyer's equation 7 since it ignores forces on the side walls. There are proofs in EM theory that show that EM waves will produces a time averaged net 0 force for any shape cavity, and any result that contradicts this either has incorrect math, or an assumption inconsistent with Maxwell's equations i.e. new physics.If you are looking for a specific part of Shawyer's paper that is wrong, just after equation 7, he applies the special relativity velocity addition formula. This formula is used to transform the velocity of something measured in one reference frame to the velocity that object would appear to have in another reference frame. Shawyer applies it to a random equation that he had rearranged to have a subtraction of velocities. He is not transforming reference frames, so applying the formula there is nonsense.When he calculates the forces on the 2 plates separately for a waveguide moving at a different velocity, he is using the equation in the right context, but fails to account for the fact that he has to transform all of the variables into the moving reference frame. Some quantities that change are the cavity length, resonance frequency, injected frequency, and the energy stored in the waves. His claims of thrust reversing at a high fraction of the speed of light are a symptom of this misapplication of special relativity.The fact that his paper's conclusions are completely wrong is sufficiently obvious to most experts that they don't even bother looking for what his specific mistakes are. The experimental results from multiple labs are another story, and those results are the only reason the EM drive is not completely dismissed.
Quote from: TheTraveller on 08/07/2015 07:59 pmQuote from: WarpTech on 08/07/2015 07:55 pmbut in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.ToddSo Dr. Ray Kwok is also wrong?I see nothing incorrect about what Dr. Kwok said. He said "Resonators". An antenna is a resonator and so is a cavity. One is an open system, the other is a closed system. The preferred methods are different at a "National Standards" level, according to @rfmwguy. While I agree 100% that the experimenters to date have consistently used the S11 method, that does not mean it is the "standard" way to do it. You are arguing that "In the EM Drive world" this is how it's done. Perhaps this is true, but is no less true that this is NOT the "standard" way to do it. Stop arguing about it and accept that fact please. You're driving everyone bonkers with your obstinance and defense of obvious incongruences. I do not follow others. I make mistakes, try to understand learn from them and forge my own path and from what I've seen, that is how most of us here operate.Todd
Quote from: WarpTech on 08/07/2015 07:55 pmbut in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.ToddSo Dr. Ray Kwok is also wrong?
but in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.Todd
Quote from: sghill on 08/07/2015 07:46 pmThe testiness of this current discussion aside, I am genuinely interested in the reason why there is a difference between these two Q value viewpoints.As far as I can gather, @TT is saying, "How they did it". @rfmwguy is saying "How it should've been done." and @tleach is saying "This is how it seems to fit McCulloch's formula." Which BTW, McCulloch doesn't define how to measure Q. He simply redefines it as the number of bounces (reflections), in the time it takes the photon to decay to zero. So that's not even the same definition of the Q that is being kicked around here. @tleach was trying to bridge that gap.What I conclude is, the experimenters may or may not be measuring it consistently using the same methodology, but in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.Todd
The testiness of this current discussion aside, I am genuinely interested in the reason why there is a difference between these two Q value viewpoints.
SPR has declined my license request.Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.Oh well at least I tried to do the right thing.
Quote from: TheTraveller on 08/08/2015 06:17 amSPR has declined my license request.Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.Oh well at least I tried to do the right thing.As a practical matter will this affect you much? Just trying to understand the implications of this. Thanks!
Quote from: demofsky on 08/08/2015 06:20 amQuote from: TheTraveller on 08/08/2015 06:17 amSPR has declined my license request.Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.Oh well at least I tried to do the right thing.As a practical matter will this affect you much? Just trying to understand the implications of this. Thanks!Should have very little effect.Was just trying to do the right thing by Shawyer / SPR and not be called out for ripping off the IP.Told Shawyer I'll still give him / SPR 25% of any gross profit made.
Wouldn't you agree, that the waves have the highest momentum when the cone angle is smallest and k*r is the largest?
It is only the reflection at the big end that opposes this force. Anything that can be done to minimize the "z" component of this reflection, will add to the thrust.Todd