Thanks for taking the time to explain this. With the ends closed (as claimed by Shawyer) how can anything get out to result in acceleration of the closed truncated cone without violating conservation of momentum? (if so what gets out and how does it get out?). If nothing gets out, it appears that acceleration of the copper cone would imply a violation of CoM.Or are you considering that the use of choke joints ( https://en.wikipedia.org/wiki/Waveguide_flange#Choke_connection ) (hat tip R. L. for the references) may allow emission out of the frustum thus preserving conservation of momentum?
@SeeShell - Are you planning to use an antenna or a waveguide for cavity excitation? I had a thought about using a waveguide, and questions of course.First, I am thinking of a square cross section and short length, one end excited by a dipole antenna with a noisy (magnetron) source, and the other fixed to the cavity model at the specified center location. Questions:What would be viable dimensions for this waveguide model?What would be the attachment point of choiceWhat would be the injection angle of the wave guide relative to the cavity x, y, z coordinates?The last question is to point out that with a wave guide, the signal could be injected parallel to the lateral axis and perpendicular to the axis of rotation, but it need not be. The signal could also be injected toward the big or small base, nearly parallel with the axis of rotation, or it could be injected nearly tangentially to the circumference of the cavity, that is nearly perpendicular to a lateral axis. Or of course it could be injected at any combination of those directions. I hope all here understand this question. Mentally, I am using a fire hose model of the injected energy, but the direction of the injected wave will make a difference in the field patterns in the cavity. won't it?
did a search and did not find this... hope it was not posted yetQuoteAIAA Propulsion and Energy Forum and Exposition27–29 July 2015Hilton Orlando, Orlando, Florida...TUESDAY, JULY 28, 2015NFF-04. Future Flight Propulsion SystemsChair(s): Gregory Meholic (The Aerospace Corporation)Co-Chair(s): Heidi Fearn (California State University, Fullerton)2:30 PM - 5:30 PM; Lake Nona A...3:30 PM - 4:00 PMDesign and First Measurements of a Superconducting Gravity-Impulse-GeneratorIstvan Lörincz; Martin Tajmar4:00 PM - 4:30 PMReplication and Experimental Characterization of the Wallace Dynamic Force Field GeneratorMartin Tajmar4:30 PM - 5:00 PMNew Theoretical Results for the Mach Effect ThrusterHeidi Fearn5:00 PM - 5:30 PMDirect Thrust Measurements of an EMDrive and Evaluation of Possible Side-EffectsMartin TajmarI wonder if someone from this thread could attend the conference and if there is a following Q/A, even mention some of the experiments discussed here, ask questions, etc.
AIAA Propulsion and Energy Forum and Exposition27–29 July 2015Hilton Orlando, Orlando, Florida...TUESDAY, JULY 28, 2015NFF-04. Future Flight Propulsion SystemsChair(s): Gregory Meholic (The Aerospace Corporation)Co-Chair(s): Heidi Fearn (California State University, Fullerton)2:30 PM - 5:30 PM; Lake Nona A...3:30 PM - 4:00 PMDesign and First Measurements of a Superconducting Gravity-Impulse-GeneratorIstvan Lörincz; Martin Tajmar4:00 PM - 4:30 PMReplication and Experimental Characterization of the Wallace Dynamic Force Field GeneratorMartin Tajmar4:30 PM - 5:00 PMNew Theoretical Results for the Mach Effect ThrusterHeidi Fearn5:00 PM - 5:30 PMDirect Thrust Measurements of an EMDrive and Evaluation of Possible Side-EffectsMartin Tajmar
(...)but I'm going to add something else: I personally see no way that any physics simulation software, FEM, FDM, BEM, or anything else, will show any meaningful thrust on the device.And in fact, it's worse that that. If you did see thrust with meep, what is more likely:1) It has accurately predicted emdrive thrust from traditional physics.2) The simulation was wrong. I've done plenty of work with numerical methods and written enough FDM codes myself to know that you don't always get exactly what you expect. That's the nature of approximation, especially understanding how error can propagate from grid point to grid point or element to element.Maybe I have this wrong, but I've gotten the impression that some people feel that all this confusion can be solved with MEEP. If MEEP showed use something that we didn't already know, ie. a net thrust greater than a photon rocket, I wouldn't consider that a plus for the EMdrive. I would consider it a negative for MEEP.
Quote from: wallofwolfstreet on 07/04/2015 04:06 pm(...)but I'm going to add something else: I personally see no way that any physics simulation software, FEM, FDM, BEM, or anything else, will show any meaningful thrust on the device.And in fact, it's worse that that. If you did see thrust with meep, what is more likely:1) It has accurately predicted emdrive thrust from traditional physics.2) The simulation was wrong. I've done plenty of work with numerical methods and written enough FDM codes myself to know that you don't always get exactly what you expect. That's the nature of approximation, especially understanding how error can propagate from grid point to grid point or element to element.Maybe I have this wrong, but I've gotten the impression that some people feel that all this confusion can be solved with MEEP. If MEEP showed use something that we didn't already know, ie. a net thrust greater than a photon rocket, I wouldn't consider that a plus for the EMdrive. I would consider it a negative for MEEP. I do not recall anyone here claiming that a simulation (meep) can prove thrust. What it does do, however, is let us quickly test our intuition of how to correctly apply theory to predict the behavior of an EM field in the cavity. For example, it appears to be incorrect to assume a standing wave in the EM Drive.If the simulation predicts no thrust, then we have ruled out even more "what ifs" questioning whether there might still be a corner case that allows for thrust using conventional physics. And if it does suggest thrust, it will hopefully give us something more specific to test for in an experiment.
Quote from: aero on 07/04/2015 05:25 pm@SeeShell - I think the waveguide should just merge right into the small end and expand from there. You want the cutoff of the waveguide to be as close to the input frequency as possible, so that the waves move very slow through he waveguide and build up stored energy before entering the frustum, tapered part of the guide. Theoretically, there should be no major VSWR reflected back down the input waveguide because the waves will have expanded beyond the cut-off as soon as they enter the frustum section. Giving up that energy as thrust.Todd
@SeeShell -
...I do not recall anyone here claiming that a simulation (meep) can prove thrust. What it does do, however, is let us quickly test our intuition of how to correctly apply theory to predict the behavior of an EM field in the cavity. For example, it appears to be incorrect to assume a standing wave in the EM Drive.If the simulation predicts no thrust, then we have ruled out even more "what ifs" questioning whether there might still be a corner case that allows for thrust using conventional physics. And if it does suggest thrust, it will hopefully give us something more specific to test for in an experiment.
@Dr. Rodal - You wroteTo double check this all that is needed is to provide other circular cross-sections: I would favor one at the antenna location, another one close to it, within the same longitudinal wave-pattern, and another one in the next longitudinal wave pattern away from it towards the big base.Would you care to look at a csv file with x,y or x,z and tell which row (x dimension is rows, isn't it?) that contains the fields you want to see? I can then take slices of the y,z plane containing those rows. Slicing the cavity in the y,z plane, and uploading to Google drive is faster than doing same for the other two planes, so more slices will not be a big burden.
Quote from: Rodal on 07/04/2015 01:59 pmQuote from: deltaMass on 07/04/2015 06:46 amYou guys tickle me pink. It doesn't matter where you put the antenna if you are using Maxwell/Poynting to figure that out. That theory says that you get zero thrust. You're better off with a Hail Mary. It's logical.You have overstated your case. There is nothing in Maxwell's or Poynting's theory saying that one should get zero thrust out of anything. Actually, Maxwell was the first scientist to derive the equations predicting that electromagnetic radiation can produce stresses, and the stress-energy tensor carries his name to honor that achievement.Case in point: if there is a net Poynting vector due to energy that gets dissipated into heat asymetrically, there maybe asymmetric heat transfer (by convection and/or radiation) resulting in asymmetric forces: "thrust". That is fully consistent with Maxwell's and Poynting's equations as well as consistent with Newton's equations. A correct statement you could make is that you, personally, don't see a way that enough thrust/InputPower can result from an asymmetric microwave cavity that is in excess of a perfect photon rocket thrust/inputPower by several orders of magnitude, but that is not the statement you made. Quote from: Anson MountI'm an enemy of exposition. I feel there's no need to overstate. While saying "Maxwell predicts zero thrust" is an overstatement, I have to agree with deltamass here. I will also throw my hat into the ring by saying I don't personally see a way "that thrust/InputPower can result from an asymmetric microwave cavity that is in excess of a perfect photon rocket thrust/inputPower by several orders of magnitude", but I'm going to add something else: I personally see no way that any physics simulation software, FEM, FDM, BEM, or anything else, will show any meaningful thrust on the device.And in fact, it's worse that that. If you did see thrust with meep, what is more likely:1) It has accurately predicted emdrive thrust from traditional physics.2) The simulation was wrong. I've done plenty of work with numerical methods and written enough FDM codes myself to know that you don't always get exactly what you expect. That's the nature of approximation, especially understanding how error can propagate from grid point to grid point or element to element.Maybe I have this wrong, but I've gotten the impression that some people feel that all this confusion can be solved with MEEP. If MEEP showed use something that we didn't already know, ie. a net thrust greater than a photon rocket, I wouldn't consider that a plus for the EMdrive. I would consider it a negative for MEEP.
Quote from: deltaMass on 07/04/2015 06:46 amYou guys tickle me pink. It doesn't matter where you put the antenna if you are using Maxwell/Poynting to figure that out. That theory says that you get zero thrust. You're better off with a Hail Mary. It's logical.You have overstated your case. There is nothing in Maxwell's or Poynting's theory saying that one should get zero thrust out of anything. Actually, Maxwell was the first scientist to derive the equations predicting that electromagnetic radiation can produce stresses, and the stress-energy tensor carries his name to honor that achievement.Case in point: if there is a net Poynting vector due to energy that gets dissipated into heat asymetrically, there maybe asymmetric heat transfer (by convection and/or radiation) resulting in asymmetric forces: "thrust". That is fully consistent with Maxwell's and Poynting's equations as well as consistent with Newton's equations. A correct statement you could make is that you, personally, don't see a way that enough thrust/InputPower can result from an asymmetric microwave cavity that is in excess of a perfect photon rocket thrust/inputPower by several orders of magnitude, but that is not the statement you made. Quote from: Anson MountI'm an enemy of exposition. I feel there's no need to overstate.
You guys tickle me pink. It doesn't matter where you put the antenna if you are using Maxwell/Poynting to figure that out. That theory says that you get zero thrust. You're better off with a Hail Mary. It's logical.
I'm an enemy of exposition. I feel there's no need to overstate.
So... using standard physics in simulations will not give us any foundations to go on? Fact. The numerical simulations have been used for years, the're used in the designing of CERN, fiber optic communications, and in cad and in just about every aspect of numerical modeling in engineering and physics I can think of. They are not perfect but I remember getting my slide rule out and using cheaters to see the divisions better. Yes, they are not perfect but it is what we have other than our gray matter and a pencil and that sucks. Let's back up and regroup so I can feel better because I'm feeling pretty funky right now. I believe there is enough empirical data in such widely varying test beds and that this is just enough out of the noise of chance that there is something going on and it deserves further testing. Agreed? Maybe? Why are you here? Just a little hope? Ya, I knew it you really don't want us laying in the dirt to look at the stars. That's cool.We have worlds of ideology clashing into this thing. Standard Physics, you know ohms law, speed of light, gravity. wait...um gravity doesn't belong there, damn, we still are not sure how it works, so out it goes...poof. So we have Einstein's work, CoM, CoE Maxwell's and a beautiful host of other that fit perfectly into our standard model. What, they all don't, we still have questions? Poo.Ok I got it now I can fix this! What makes all these very nice and obeyed laws work so beautifully (well kinda)? Quantum MECHANICS QV QM QED PMS and lets just throw in a black hole so we can suck it all up so nothing matters. Sorry, it does matter, I was kidding. They all matter but they are like the kid under the stairs a little freaky with glowing eyes and they are so different than the standard model. But, but, but, they make the standard model work. Phew, now here we are trying to figure out how to go backwards from normal physics and a can of microwaves down to quantum world to make thrust, to make it go, to understand. You know it's not easy. Things will not click and work quite like they should and we need to be diligent and have hope.Is it worth it, you bet, will they be questions, yep. And every bit of it it worth it. So bring your doubting on and your questions and your blind faith and we'll do this, we'll kick this can.And a Happy 4th Of July to all that are celebrating it.Shell
I believe there is enough empirical data in such widely varying test beds and that this is just enough out of the noise of chance that there is something going on and it deserves further testing.
...The question of, "How does the momentum get out?", is a different answer. Obviously, it would have more thrust if the big end were open. Any momentum reflecting off the big end plate will negate the momentum gained in getting there. However, in a dissipative system, after each bounce the wave rotates the momentum a little more into the "x" direction, but loses energy due to dissipation of heat into the copper. That means that when it reaches the back wall, it has less momentum than it should have. The NET is not zero because something was lost along the way....
Quote from: WarpTech on 07/04/2015 05:27 pm...The question of, "How does the momentum get out?", is a different answer. Obviously, it would have more thrust if the big end were open. Any momentum reflecting off the big end plate will negate the momentum gained in getting there. However, in a dissipative system, after each bounce the wave rotates the momentum a little more into the "x" direction, but loses energy due to dissipation of heat into the copper. That means that when it reaches the back wall, it has less momentum than it should have. The NET is not zero because something was lost along the way....Sorry, please explain to the Newtonian guy in me : how a play of throwing and bouncing and catching balls within a free floating box could give any persistent deltaV to the box ? deltaX I see, but not deltaV at the end of the story (when the game stops). At one end of the box you have a source of energy, the energy flows in some arbitrary geometry and after long or short path ends absorbed asymmetrically by some inner walls. Some walls (patches) will have received more energy, some less. A source full of energy (loaded battery, or fresh radioisotopes generator) weighs more than when depleted. A hot wall patch weighs more than a cold one. All that has happened is a (tiny) displacement of the centre of mass within the box, following the displacement of conserved energy. A corresponding tiny deltaX in the opposite direction will be observed from the outside of the box, no deltaV between start and end of "discharge". That is, unless the inner walls bleed thermal IR outside, with photon rocket efficiency as an upper bound.Do you really say that the mechanism you propose here would allow a system fully enclosed in an ideal perfect thermal blanket to gain an ultimate deltaV, i.e. without bleeding any radiation having permanently (asymptotically after switch off) changed its velocity relative to its initial inertial rest frame, as good as the velocity acquired by a chemical thruster burst is still there indefinitely after power off of said thruster ?Not addressing the later hypothesis involving DC components, just this specific part quoted, as you seem to imply that it could be valid by itself and independently.
...First, does anyone know why the Formatting tools on here don't work anymore? I'm using Safari browser on a Mac. They used to work, but haven't worked for the past couple of weeks. ...
Quote from: aero on 07/03/2015 09:47 pm@Dr. Rodal - You wroteTo double check this all that is needed is to provide other circular cross-sections: I would favor one at the antenna location, another one close to it, within the same longitudinal wave-pattern, and another one in the next longitudinal wave pattern away from it towards the big base.Would you care to look at a csv file with x,y or x,z and tell which row (x dimension is rows, isn't it?) that contains the fields you want to see? I can then take slices of the y,z plane containing those rows. Slicing the cavity in the y,z plane, and uploading to Google drive is faster than doing same for the other two planes, so more slices will not be a big burden.I think that the best y-z plane (with normal x) cross-sections would be at the following two locations:A) 150 in the x direction from the left end, (the end nearest the big base)B) 209 in the x direction from the left end, (the end nearest the big base)These cross sections are located near the small end (the 209 location is located near the antenna).It appears that the matrix is not square in this case (wasn't it square before when it had half the number of entries in each direction?): the x direction has 247 entries while the y and the z directions have 264 entries. Is that in agreement with what you intended?This will be useful not only to double check the results, and see the circumferential distribution of the Power surface-density flux (the Poynting vector) at those locations
..."... throwing and bouncing and catching balls within a free floating box..." Is a linear equation of momentum. The momentum coming out of the waveguide is a non-linear equation, with a force exerted as 1/r^2. The momentum transferred by the wave is proportional to the phase velocity, not c. So there is more momentum exchange at the small end due to higher phase velocity, than there is at the big end. A photon rocket in free space is a linear equation. Inside a tapered wave guide, it is non-linear. It can't be explained in terms of billiard balls. The question you are asking is the one I am trying to resolve mathematically. My theory is not quite there yet....