Quote from: Rodal on 04/06/2015 12:38 amModeling a plane wave striking an absorbing surface is a different problem than modeling the standing waves in a resonating cavity like the EM Drive.I was referring to images like these ones, that you posted some time ago:The electromagnetic fields in that image don't look like the electromagnetic fields in the EM Drive, indicating that there was something wrong with your model of the EM Drive. Since electromagnetic forces are due to the electromagnetic fields, if one doesn't get the electromagnetic fields correctly, then it stands to reason that the calculations of electromagnetic forces in the EM Drive cannot be correct either.Wasn't that particular simulation modeling the EM Drive without openings, which in turn showed us how important the openings are to the overall operation of the drive (at least in the simulation)?
Modeling a plane wave striking an absorbing surface is a different problem than modeling the standing waves in a resonating cavity like the EM Drive.I was referring to images like these ones, that you posted some time ago:The electromagnetic fields in that image don't look like the electromagnetic fields in the EM Drive, indicating that there was something wrong with your model of the EM Drive. Since electromagnetic forces are due to the electromagnetic fields, if one doesn't get the electromagnetic fields correctly, then it stands to reason that the calculations of electromagnetic forces in the EM Drive cannot be correct either.
Quote from: sghill on 04/06/2015 12:50 pmQuote from: Rodal on 04/06/2015 12:38 amModeling a plane wave striking an absorbing surface is a different problem than modeling the standing waves in a resonating cavity like the EM Drive.I was referring to images like these ones, that you posted some time ago:The electromagnetic fields in that image don't look like the electromagnetic fields in the EM Drive, indicating that there was something wrong with your model of the EM Drive. Since electromagnetic forces are due to the electromagnetic fields, if one doesn't get the electromagnetic fields correctly, then it stands to reason that the calculations of electromagnetic forces in the EM Drive cannot be correct either.Wasn't that particular simulation modeling the EM Drive without openings, which in turn showed us how important the openings are to the overall operation of the drive (at least in the simulation)?If a numerical model cannot get the electromagnetic fields correctly for the EM Drive in that simpler case, one cannot derive from such a model valid conclusions on the importance of "the openings are to the overall operation of the drive" or to the validity of forces that are based on derivatives of the fields.One should not extrapolate that a two-dimensional (2D) model of the EM Drive that ignores its circular cross-section and three-dimensional field effects can be used to show valid conclusions on the importance of "the openings are to the overall operation of the drive" of the physical three-dimensional (3D) EM Drive.A flat 2D model like this one, completely ignores for example the main electromagnetic field in the TM (transverse magnetic) 212 mode presently being tested by NASA Eagleworks. The transverse magnetic field occurs out of the plane shown in the figure, in the azimuthal direction and it has 2 full wave patterns in that circumferential direction. None of this is being modeled by this 2D Finite Difference simulation.
What QuantumG said. I'm sorry for being part of the digression. Let's focus on the EmDrive and its space-related flight applications.
Wouldn't argon be a better fuel for large EM drives, like for transfers to Mars with a lot of tonnage of equipment? Say an in space only craft that would transfer cargo to Mars flyby, let the cargo have a chemical powered craft that would land equipment and the EM craft flys back to Earth say to L1 OR L2 to pick up more cargo? Xenon is rare in comparison to argon. If the craft were large enough, it could refuel at L1 with argon plus pick up or return a Mars cargo lander. If the transfer time was fast enough, humans could also be transferred. All that being said, with todays technology, how large would the solar panels be to say transfer 100 tons of cargo to and from Mars? Would it be better to go chemical all the way?
I would prefer to have solutions in 3D myself, but I'm not going to get them with this computer system, the meep EM thruster cavity model is to large. Its not only long run times, but also memory requirements and even hard disk storage. I had one run bomb out because I ran out of disk space while writing the output files at the end of the run
Quote from: Star-Drive on 04/06/2015 12:25 pmAces High:The hot fusion candidates you mentioned all have one major problem. That being that except for D-T fusion, no hot fusion scheme to date has ever demonstrated breakeven let alone enough energy gain over its input to make it a viable aerospace fusion reactor candidate. (I believe that the UK D-T fusion reactor may have reached breakeven for a few minute run, but Lord, look at the neutron flux it generates, which is ~70% of a pure fission reactor for a given output power, a pure fission reactor that can be much smaller and lighter than any tokomak reactor can ever be.) And after seeing what happened during the poly-well fusion reactor saga, I have great doubts as to the claims by any of the current crop of alternate fusion reactor concepts, L-M's optimistic claims about their fusion reactor design concept not withstanding. Best, Paul M.You're mentioning the Joint European Torus (JET) tokamak. But there are other possible paths for controlled fusion other than tokamaks. Besides Polywell and Lockheed-Martin reactors you've just cited, maybe another scheme could reach breakeven "soon" among the aneutronic p-B11 Dense Plasma Focus fusion from LPP, the (also aneutronic) Colliding Beam Fusion Reactor from Tri Alpha Energy, the colliding FRC Fusion Engine from Helion Energy, the MTF compressor from General Fusion, the MagLIF z-pinch from Sandia National Labs… None of them are based on tokamaks. Whatever, finding an appropriate energy source for the spaceship before proving the EmDrive does work is an interesting thought experiment (and perhaps mandatory for management) but it is a bit putting the cart before the horse in my opinion.
Aces High:The hot fusion candidates you mentioned all have one major problem. That being that except for D-T fusion, no hot fusion scheme to date has ever demonstrated breakeven let alone enough energy gain over its input to make it a viable aerospace fusion reactor candidate. (I believe that the UK D-T fusion reactor may have reached breakeven for a few minute run, but Lord, look at the neutron flux it generates, which is ~70% of a pure fission reactor for a given output power, a pure fission reactor that can be much smaller and lighter than any tokomak reactor can ever be.) And after seeing what happened during the poly-well fusion reactor saga, I have great doubts as to the claims by any of the current crop of alternate fusion reactor concepts, L-M's optimistic claims about their fusion reactor design concept not withstanding. Best, Paul M.
@Rodal -Are you telling me that an effect that shows in 2D may not show in 3D, or that an effect that exists in 3D may not show in 2D? Or both? I would prefer to have solutions in 3D myself, but I'm not going to get them with this computer system, the meep EM thruster cavity model is to large. Its not only long run times, but also memory requirements and even hard disk storage. I had one run bomb out because I ran out of disk space while writing the output files at the end of the run.I am forced to operate on the hope and expectation that I will be able to confirm an effect that shows in 2D by making a 3D run targeted to that effect. If I can't do that, then I can't, but I certainly can not explore the parameter space by making 3D runs.
Does anyone actually believe that if we had a working EmDrive with the predicted thrust capabilities that we would have a problem finding power for it? ....So from where I am standing, power will not be an issue if the EmDrive is proven to deliver usable thrust. We as a species will find a way.
Quote from: birchoff on 04/06/2015 04:59 pmDoes anyone actually believe that if we had a working EmDrive with the predicted thrust capabilities that we would have a problem finding power for it? ....So from where I am standing, power will not be an issue if the EmDrive is proven to deliver usable thrust. We as a species will find a way.I fully agree. Fretting about the energy source is a bit too much at this stage, when conclusively proving the existence of the phenomenon has yet to happen.If this becomes a proven scientific fact, with a few more conclusive replications, finding a power source for it is just an engineering problem. That is, one based on the application of already known scientific and technical principles. We know nukes work and we have them, we know fuel cells work and we have them, the same as solar photovoltaics, etc. Gee, if Emdrives are proven to work as H. White and Paul M. expect, we would be soon putting gasoil engines/generators to power them, and this for replacing turbofans/propellers for flying in the low atmosphere!
Quote from: aero on 04/06/2015 04:42 pmI would prefer to have solutions in 3D myself, but I'm not going to get them with this computer system, the meep EM thruster cavity model is to large. Its not only long run times, but also memory requirements and even hard disk storage. I had one run bomb out because I ran out of disk space while writing the output files at the end of the runI'm familiar with these 2D vs 3D issues and I agree 3D is necessary.I or others here with access to more substantial hardware can probably run said simulations for you, provided you can package up the software for us.
Quote from: tchernik on 04/06/2015 06:04 pmQuote from: birchoff on 04/06/2015 04:59 pmDoes anyone actually believe that if we had a working EmDrive with the predicted thrust capabilities that we would have a problem finding power for it? ....So from where I am standing, power will not be an issue if the EmDrive is proven to deliver usable thrust. We as a species will find a way.I fully agree. Fretting about the energy source is a bit too much at this stage, when conclusively proving the existence of the phenomenon has yet to happen.If this becomes a proven scientific fact, with a few more conclusive replications, finding a power source for it is just an engineering problem. That is, one based on the application of already known scientific and technical principles. We know nukes work and we have them, we know fuel cells work and we have them, the same as solar photovoltaics, etc. Gee, if Emdrives are proven to work as H. White and Paul M. expect, we would be soon putting gasoil engines/generators to power them, and this for replacing turbofans/propellers for flying in the low atmosphere!I believe because of their extremely contentious nature & reputation to the majority in the scientific community it's not just a case of showing EM drives work but producing a rock solid case for why they work. Unfortunately there has been so many other claims of a similar nature that have been made over the years that have proved to be nonsense that it has severely muddied the waters leaving things such as the EM drive with incredibly high hurdles to clear before anyone gives them the time of day.
One thing that has mystified me about this whole business is it not the fact that this effect has been known about for a number of years so why is it only in recent years that people have started looking into it?
When doing EM simulations you can model the transient propagation of radiation as it interacts with your model, which can be valuable to see exactly how it reflects and interacts with various features (like a groove, slit, etc). In this case you model an incoming pulse, composed of many frequencies.Another common simulation is to do a frequency domain simulation in which you compute the steady state solution of inputting a single frequency into the model. But you have to be careful in how you interpret these results, because they are non intuitive, e.g. they don't show the propagation of radiation.I know you can perform both types of simulation using COMSOL and CST.I have a few questions that perhaps the emdrive experts here can answer. Why don't we use much smaller cavities? I believe they would be easier to machine, and experimentally work with. This would require scaling the wavelength, but what is the problem with that?
Given the figures the predicted thrust that paul march provided us. Anyone mind educating this lay person on how a single EmDrive thruster would perform vs our current rockets.