...Experience I have gained from others says it is critical to be able to tune the Rf amp frequency to the highest Return Loss dB (lowest VSWR) from the cavity as otherwise little or no Force generation will happen.With respect, trying to play the EMDrive Poker Machine and hope a Rf gen frequency matches what the cavity needs is a good recipe to waste a lot of time and money.
Quote from: TheTraveller on 07/21/2015 05:07 am...Experience I have gained from others says it is critical to be able to tune the Rf amp frequency to the highest Return Loss dB (lowest VSWR) from the cavity as otherwise little or no Force generation will happen.With respect, trying to play the EMDrive Poker Machine and hope a Rf gen frequency matches what the cavity needs is a good recipe to waste a lot of time and money.I was going to correct you on your use of "Return Loss". I looked it up: https://en.wikipedia.org/wiki/Return_lossEveryone I've been around was doing it wrong; we tuned for "low" (as in big-negative) return loss. But wikipedia says that's backwards. Well, you can't believe everything you read there, now can you?Anyways, if you really want to tune to the center frequency of the cavity, put at tap on it, and put an amplifier between the very loosely coupled cavity output tap and the exciter loop. Then it's the tuning element of an oscillator, and will track the cavity. Not like you couldn't tune the cavity.However, it may be advantageous to to just above or below the point it may oscillate at to maximize effects. Something to consider.
What about the cavity effective Q with negative resistence added by the magnetron?
One can model the magnetron amplification by making the dipole antenna with negative loss material in Meep?
...If I might be pardoned for butting in, the simulations so far, while very important to familiarize with the software, don't inspire my confidence WRT utility.....Use the eigenvalue mode of interest to excite the cavity in the time-domain (meep) and see what it does when the cavity is accelerated. I believe meep can do this. I read a post on the meep mailing list where the Cerenkov effect was being modeled by moving the charge-source between runs. Why not the cavity? Something I hope to look into....
Quote from: Ricvil on 07/21/2015 10:10 amWhat about the cavity effective Q with negative resistence added by the magnetron?Depends what you mean by "effective". It's as you suspect, up to the point the magnetron saturates. You can increase the "effective" Q with either a 1 port negative resistance, or with a 2 port amplifier, if "effective" to you means having a high Q cavity for, say a filter or preselector on your radio and are not going to be saturating or running the magnetron at its maximum output.I've tested circuits active filters with positive feedback that show increased Q. The downside is higher noise, and the potential for instability as the Barkhausen stability criterion unity-gain is approached.But if "effective" for you is having the energy-equivalent of a magic-mass that exhibits asymmetrical inertia, or negative inertial impedance, then you want max energy, max mass, max magnetron output and the limiting factor for the max energy/effective cavity mass-energy is going to be the loss and dissipation of the cavity and max magnetron output. The effective Q drops as the magnetron saturates.So you go nowhere with this unless you're into filter-sharpening and don't care too much about stability, repeatability or noise.Quote from: Ricvil on 07/21/2015 10:10 amOne can model the magnetron amplification by making the dipole antenna with negative loss material in Meep?Lol. Now you have an unstable computer simulation
...My take on it, if it's for real, is that it behaves like an animation I saw on (the only?) youtube lecture by Woodward; a rocket with a spring and brick on back bouncing its way forward, sort of like a squid.Unlike the Woodward effect which relies on the charged capacitor having more inertia than an uncharged one, the "Shawyer Effect" I call a "Sagnac Ratchet"; the force in the forward, and impedance in the reverse directions are the result the frustrum's asymmetrical dispersion, group velocity, and sum/difference frequency filtering characteristics.Maybe Shawyer would have gotten a different response if he made it clear it was acting as a ratchet, so CoM wouldn't have been the issue.
Maybe Shawyer would have gotten a different response if he made it clear it was acting as a ratchet, so CoM wouldn't have been the issue.
Shawyer’s claim is that the photons bounce against the walls of the cavity, and in so doing exert a force on it. In this he is perfectly correct. He further claims, however, that the net force on the cavity is asymmetrical, without any photons leaving the cavity, and in this he is not correct. The centre of mass of a closed system can not accelerate (or resist gravity either, since that amounts to the same thing) as a result of interactions between the parts of the system. That has been understood theoretically since the time of Newton, and confirmed experimentally in thousands of contexts and probably billions of individual events.
Well, firstly Shawyer doesn’t actually share your belief that there is “a big new field yet to be discovered”, because he thinks his claims are a consequence of two old, established and respected theories: Maxwell’s theory of electromagnetism and Einstein’s theory of special relativity. He didn’t build his gizmo, measure this mysterious thrust, and then ask “What new science can explain this?” Rather, he invented the “drive” first on (he says) purely theoretical grounds, based on established theory.This is why I (and a few million other people) know with mathematical certainty that his theoretical claims are wrong. Maxwell and Einstein’s theories can be expressed mathematically, and it can be proven that they will always without exception respect the relativistic law of conservation of momentum. In other words, whatever Shawyer has measured in the lab, if he thinks he has deduced theoretically from Maxwell and Einstein some consequence that violates that law, he is making a statement about mathematics, and it is trivially easy to prove that it is wrong.Shawyer in fact insists that the claimed operation of his drive would not violate the law of conservation of momentum. Unfortunately for him, it’s even clearer that this is false. Before the drive is switched on, the momentum of the spacecraft in its rest frame is zero. If the drive is used for some time and then switched off, the momentum of the spacecraft in that same frame is now non-zero. The only way to make the “before” and “after” momenta equal is if there’s something else hanging around in the “after” scenario, such as photons emitted as exhaust. But Shawyer himself denies that there is any such exhaust (and even if there was, it would actually carry thousands of times too little momentum to balance his claimed effect). So he is claiming that zero equals something other than zero. I’m all for healthy scepticism against scientific orthodoxy, but that’s just farcical.Then we come to his experiments, which conveniently support an effect that Shawyer “predicted” with this garbled non-theory. Can you really think of no other explanations for small forces appearing in a machine with a big power supply and a cooling system, other than your suggestion of exotic new physics (which is not Shawyer’s own claim at all), or Shawyer’s suggestion that zero equals not zero?
...With respect to what Meep can or cannot do, Meep is an open source software program NOT meant to be used as a black box..."write your own function".
...excite the cavity in the time-domain (meep) and see what it does when the cavity is accelerated. I believe meep can do this.
the answer is that Meep, out of the box, canNOT show you any cavity acceleration whatsoever.Meep only solves Maxwell's equations. There are no mechanical equations in Meep, there are no equations there that will allow you to model any Newtonian acceleration...Writing a procedure to move the charge-source between runs to model the Cerenkov effect is trivial in comparison with re-writing Meep to allow modeling of cavity acceleration.
Quote from: mwvp on 07/21/2015 06:35 amMaybe Shawyer would have gotten a different response if he made it clear it was acting as a ratchet, so CoM wouldn't have been the issue.He did make it clear, see attached, just nobody cared to read and think. Much easier to join groupthink, bash the man and his invention.
A far less elegant, conclusive, but far faster executing hack (plan-B) is to integrate the fields, and derive a lumped impedance equivalent network to create a spice model from, then use a phase shifting component in spice to model the doppler shift. The forces on the frustrum would be derived from the voltage and currents in the equivalent network.
Quote from: mwvp on 07/21/2015 06:35 am...Maybe Shawyer would have gotten a different response if he made it clear it was acting as a ratchet, so CoM wouldn't have been the issue."asymmetrical dispersion, group velocity, and sum/difference frequency filtering characteristics"don't really get around the Conservation of Momentum issue in a frame-indifferent Universe.
...Maybe Shawyer would have gotten a different response if he made it clear it was acting as a ratchet, so CoM wouldn't have been the issue.
...Conservation of Momentum issues remain, and as often remarked by Frobnicat and deltaMass, even more disturbing issues related to conservation of energy are brought forth.
Quote from: TheTraveller on 07/21/2015 01:33 pmQuote from: mwvp on 07/21/2015 06:35 amMaybe Shawyer would have gotten a different response if he made it clear it was acting as a ratchet, so CoM wouldn't have been the issue.He did make it clear, see attached, just nobody cared to read and think. Much easier to join groupthink, bash the man and his invention.My advice to you is to cut down on your theoretical "thinking" and continue with building your experiment. This strategy maximises your chances of success.
But don't fling Eagleworks' 4N/kW rottting, dead, CoM-violating cat at Shawyer, because he does point out he believes his gadget looses power with acceleration and conforms with CoE and CoM. This adds to his credibility. Eagleworks credibility should be questioned for sighting such figures as they have without qualification.
An electrical reaction occurs between the EM wave and the reflector surfaces of the resonator, resulting in an input impedance change with acceleration. This is seen in the power curve in fig 10.
Quote from: mwvp on 07/21/2015 02:26 pmA far less elegant, conclusive, but far faster executing hack (plan-B) is to integrate the fields, and derive a lumped impedance equivalent network to create a spice model from, then use a phase shifting component in spice to model the doppler shift. The forces on the frustrum would be derived from the voltage and currents in the equivalent network.How did Doppler shift suddenly creep in to the discussion? What is the physics basis for that statement?
If it's about accelerating simulations, couldn't we theoretically try and make something like the SETI client and distribute prepared packages to those willing to donate CPU time to simulate a ton of EM drive configurations - even over longer periods of time and operation?
Right now, turning off the source after 0.013 microseconds would be much more informative than running Meep up to 1 microseconds and beyond.This is something that Todd asked many days ago: just turning off the source and seeing what happens.
...I've attached a movie file showing a Ez spatial slice just off of the input source for one source period at the end of the simulation (30 source periods), courtesy of Aero's ctl file). If we're looking for amplification / resonance ISTM that it takes a lot more than 30 time periods of duration to get there based on this E-field animation......
... this is a cartesian coordinate simulation tool, so the boundaries are stairsteps that are sub-grid fitted and the whole simulation is in a cartesian block as compared with a curvilinear fitted/transformed space - ugly IMO, but I'm not a CEM person......