Kurt,I wish I knew the type of interface to use. I am not an expert in microwave components, but I'm researching as time permits. Also, at 2.4503 GHz, it's going to be pretty large. Did you calculate the wave velocity for that mode? Todd

ZelleriumMay I suggest using a curved mirror as it results in greater relational movement of the laser dot. You may find them in some hardware shops? or some womens makeup departments according to my daughter.At a minimum you will need two strings, one for front, one for rear of the unit. This will minimise sideways /rotational translation which would mask effects. Keep each string separate and attach each to the roof.If you still get sideways torque/momentum due to induced mechanical events derived from the switching on/off of the magnetron etc then you may require 4 strings, one on each "corner" of the unit.

Quote from: Rodal on 05/10/2015 12:21 AMQuote from: deltaMass on 05/10/2015 12:14 AM....Really and truly, this experiment cries out for a space test.There are several people that think the same way (that it cries out for a space test), while there are several other ones that think it would be premature. Since you made a powerful argument for the energy paradox, it would be useful if you could list all the reasons (and what and how should be tested) why a space test should be the next step, as a powerful argument in that direction may help to push the ball rolling...upwards I am happy that you found my position on the energy paradox powerful. But speaking of premature, some further mulling and reading - ongoing - tells me that there may well be a third possibility for the behaviour of the thrust over time. If this "third thrust scenario" turns out to be the correct one, then the EmDrive may not be useful for any kind of propulsion, and would at best remain as an interesting test framework for various physics variants.A third thrust scenarioAgain we assume that the measured thrust is actual. We note its two characteristics:a) It is measured as a static force.b) It remains constant as long as input power is applied to this static configuration.'a)' implies that we can only theorise as to its dynamic behaviour - i.e. when the EmDrive moves over time.I take together two further pieces of information:1. Shawyer's video of the moving EmDrive2. Mike McCulloch's MiHsC theory of operation.Now of course, there are a variety of interpretations possible for both of these. For example, that the video is flawed because all the angular momentum is being supplied by imperfections in the air bearing. Or that Mike's theory is nonsense because it violates GR. And so forth. So here I have to decide what to assume so as to justify this 3rd scenario. So here I choose:1. The vid shows that an impulse is produced which results in a real and constant momentum of the EmDrive.2. The theory predicts the same thing - constant forward EmDrive momentum.And so this third thrust scenario is this:As soon as the EmDrive is free to move, a definite and constant momentum is established and its thrust falls to zero. So far, so good. But given this third thrust scenario is the correct one, what then is expected to happen when we switch off the power?

Quote from: deltaMass on 05/10/2015 12:14 AM....Really and truly, this experiment cries out for a space test.There are several people that think the same way (that it cries out for a space test), while there are several other ones that think it would be premature. Since you made a powerful argument for the energy paradox, it would be useful if you could list all the reasons (and what and how should be tested) why a space test should be the next step, as a powerful argument in that direction may help to push the ball rolling...upwards

....Really and truly, this experiment cries out for a space test.

Yes. It is not a propellant-less thruster anymore.

Quote from: LasJayhawk on 05/09/2015 09:06 PMI keep looking at this and thinking it's not right.It looks to symmetrical.COMSOL's website says the RF module can do far field calculations, and the antenna placement would appear to put at least part of the frustum in the near field. It looks by eyeball that the software is only looking at the far field being reflecting off the small end of the frustum.Or am I missing something?This COMSOL Finite Element Analysis solution is a numerical solution of Maxwell's differential equations, taking into account the boundary conditions, including the losses responsible for the finite Q. What you are looking at is the steady state of the electromagnetic fields.The steady state electromagnetic field solution are standing waves. Although the initial condition is not symmetrical, due to travelling waves, this is a very-short-lived transient, as the solution soon reaches a (practically) symmetric steady state. This has been shown by @aero with a very interesting movie based on a 2D solution of the truncated cone as a flat trapezium using MEEP which is a Finite Difference code (free from MIT alumni) that performs the full transient solution. It was neat to see how the (practically) symmetric steady state was soon reached starting from an unsymmetric initial condition.Furthermore, as pointed out by RotoSequence, the steady state solution for the magnetic field and a COMSOL thermal analysis was corroborated by temperature measurements using an infrared thermal camera, which verifies that the heating is due to induction heating from the magnetic field.I obtained an exact solution for the symmetric steady state (which of course does not take into account the initial unsymmetric transient) and it fully verifies NASA's COMSOL FEA steady state solution for the electromagnetic field: the natural frequency is within 1% of the exact solution and the mode shapes are extremely close (I posted the exact solution comparison some time ago).If one is interested in near-field far-field, transient, fully complex solution (including initial travelling waves morphing into standing waves, as well as evanescent waves) then one has to resort to a time-marching solution as with MEEP finite difference approach or a [FEA in space/FD in time] solution that imposes a finite element discretization in space and a finite difference time discretization. (Such a transient, 3D solution containing evanescent waves is extremely time consuming.)

I keep looking at this and thinking it's not right.It looks to symmetrical.COMSOL's website says the RF module can do far field calculations, and the antenna placement would appear to put at least part of the frustum in the near field. It looks by eyeball that the software is only looking at the far field being reflecting off the small end of the frustum.Or am I missing something?

Quote from: deltaMass on 05/09/2015 10:09 PMAnd while on the subject of simulation: Guido Fetta of Cannae tells me that his COMSOL(?unsure) sim predicts a nonzero net Lorentz force for his device. Now, we all learned that no closed system of currents can produce such a net force. There's a paradox. He insists that there are no significant cumulative rounding errors.Anyone have insight into this?There cannot be a paradox.Let's remember that the COMSOL FEA solution is the steady state solution showing the spatial distribution of the field. Remember that the steady state solution of Maxwell's differential equations can be accomplished by separation of variables. The harmonic (time varying) part of the field is assumed. So, for example, the Magnetic Field shown on the COMSOL output is the spatial distribution of the magnetic field. Now, what is shown as a maximum and what is shown as a minimum is arbitrary, since depending at what time one arbitrarily chooses to display the magnetic field, as the magnetic field varies with time like a harmonic function.Similarly, the Poynting vector is a harmonic function of time, and this is, as you point out, well known in the literature, with a frequency which is twice the frequency of the magnetic and the electric field.Although the spatial distribution of the Poynting vector is non-zero at arbitrary points in time, over a whole cycle the Poynting vector (and the Lorentz force) for a cavity sums up to exactly zero, just like the mean of the magnetic and electric fields is also zero. COMSOL is an excellent package.The Poynting vector solution of Maxwell's equations points towards the Big Base half of the time, and points towards the Small Base half of the time.COMSOL will not tell that to the analyst obtaining a steady solution where the harmonic function of time is implicit. It is recommended that COMSOL and any other FEA packages (ANSYS MultiPhysics, etc., ABAQUS, ADINA, NASTRAN) should be run by experienced FEA analysts, to prevent errors. (Ditto for FD, control volume , and any other numerical packages).

And while on the subject of simulation: Guido Fetta of Cannae tells me that his COMSOL(?unsure) sim predicts a nonzero net Lorentz force for his device. Now, we all learned that no closed system of currents can produce such a net force. There's a paradox. He insists that there are no significant cumulative rounding errors.Anyone have insight into this?

It is my understanding, from what Paul March wrote, that the main controlling parameter in determining the thrust generation performance of the EM-Drive is the rate of phase modulation of the RF signal that is injected into the resonant cavity. This requires an FM modulated signal of around 100 kHz deviation that dithers back and forth around the resonant cavity's resonant frequency as fast as possible.

COMSOL is an excellent package.

Update on the replication attempt.I have succeeded in making a safe stable balance (finally), but I am still absolutely bombing in my attempts to get power to the balance. The slip ring approach has its faults and I'm going to have to find some sort of flexible power pickup or abandon the whole slip ring idea altogether. If I stick with this approach, I'll never get anywhere near the sensitivity of Cavendish.If I go to flying a battery and use DC-DC converters (http://www.amazon.com/dp/B00JUFJ1GA?psc=1) to power the electronics, any future of high power testing using this setup will be dashed. As I know, engineering is a bunch of tradeoffs. https://goo.gl/Q3jGN1

Update on the replication attempt.I have succeeded in making a safe stable balance (finally), but I am still absolutely bombing in my attempts to get power to the balance. The slip ring approach has its faults and I'm going to have to find some sort of flexible power pickup or abandon the whole slip ring idea altogether. If I stick with this approach, I'll never get anywhere near the sensitivity of Cavendish.If I go to flying a battery and use DC-DC converters (http://www.amazon.com/dp/B00JUFJ1GA?psc=1) to power the electronics, any future of high power testing using this setup will be dashed. Not to mention I'll have to go to a much stronger torsion wire or a Dyneema braid (as opposed to the solid Dyneema line I'm using now) to hold everything up. As I know, engineering is a bunch of tradeoffs. https://goo.gl/Q3jGN1Useful references I found:http://www.alta-space.com/uploads/file/publications/feep/049-dAgostino.pdfhttp://photonicassociates.com/ISBEP4-2.pdf

Quote from: KittyMoo on 05/10/2015 07:19 AMYes. It is not a propellant-less thruster anymore.Capacitors and batteries lose mass when they are discharged.

Quote from: rgreen on 05/02/2015 03:28 PMFollowing on what jknuble said about the multipactor-like effect as a possible cause of thrust. http://en.wikipedia.org/wiki/Multipactor_effect I can't help but wonder about what's going on with the copper surface of the frustum. A quick back of the envelope (well, python) calculation shows that there's certainly enough energy in these devices to somehow atomize a small amount of copper , and propel them with enough momentum to produce a small amount of thrust. For example, a 30 watt emdrive where 0.001% of the energy went towards atomization and 1% went toward addtional momentum of the particles... You'd have a device with 91uN thrust, propelling 1.4ng of copper a second at 65500m/s.I can think of 3 ways to debunk this. 1) perhaps that amount of particles going that fast would be noticeable with the naked eye, so this isn't really a valid explanation. 2) stick a detector behind the thruster (are they ionized?). 3) SEM of the surface compared to scraps from the same batch of copper not used in the thrustum.Just how would we get a net-thrust from a closed cavity with atomization. Even if atoms are being ioniozed inside the cavity I don't see how that could result in a net thrust. Atomization results in immediate thrust but then that creates impact on the other side of the cavity canceling out the propulsion.

Following on what jknuble said about the multipactor-like effect as a possible cause of thrust. http://en.wikipedia.org/wiki/Multipactor_effect I can't help but wonder about what's going on with the copper surface of the frustum. A quick back of the envelope (well, python) calculation shows that there's certainly enough energy in these devices to somehow atomize a small amount of copper , and propel them with enough momentum to produce a small amount of thrust. For example, a 30 watt emdrive where 0.001% of the energy went towards atomization and 1% went toward addtional momentum of the particles... You'd have a device with 91uN thrust, propelling 1.4ng of copper a second at 65500m/s.I can think of 3 ways to debunk this. 1) perhaps that amount of particles going that fast would be noticeable with the naked eye, so this isn't really a valid explanation. 2) stick a detector behind the thruster (are they ionized?). 3) SEM of the surface compared to scraps from the same batch of copper not used in the thrustum.

Quote from: WarpTech on 05/10/2015 07:32 AMQuote from: KittyMoo on 05/10/2015 07:19 AMYes. It is not a propellant-less thruster anymore.Capacitors and batteries lose mass when they are discharged.Capacitors can have interesting aspects213310.pdf

Quote from: Mulletron on 05/10/2015 11:57 AM...There must be some way of coupling the RF power to the cavity using feed horns or near-field antennas. That would eliminate the need to weigh down the balance with a PA, batteries or achive a workable cummutator. There may not be much gain at the frequency of interest but all you want to do is to transmit a fraction of the power. Maybe 2 identical collinear dipoles would work. The recieve dipole, mounted on the outside of the cavity, would connect to the internal loop used to drive the cavity. If you have access to a network analyzer you could optimize the match and maximize the return loss.

...

Not a single thing I built defied the laws of physics or the formulas of the trade. . . Maxwell, Ohms law, etc. If something didn't work for some weird reason, it still followed the basic laws and formulas when it ended up.It doesn't really matter to me what is happening inside of the EM Chamber it must follow the principals of physics and conservation of energy and momentum is one of them. If I have a Air Tank pressurized with 200psi of air and a audio speaker inside that can blast at 100 watts any frequency range no matter what mixture of sound or what mixture of harmonics I crank, the tank will not move, but put a hole in one end and stand back. The second law of thermodynamics states that the entropy of an isolated system never decreases and the EM Chamber is an isolated enclosed system, we think. If we are getting thrust that, thrust must be acting outside the chamber in some form. This is why I asked the simple question if smoke was used in the tests, it wasn't to detect thermal air currents but to see if it was moving away from any thrust from the EM Chamber. Smoke is small .5 to 2 um and might be be directly effected. If not then look for other forms of accelerated energy, providing thrust emanating out of the EM Chamber.

the utility of COMSOL in figuring out this problem is limited as COMSOL is considering the standing wave and isn't considering the traveling wave. It gives no consideration to what is happening over extended time (over multiple full cycles) or to what is happening to a resonant cavity under dynamic operation, for example while under acceleration. COMSOL provides no insight as to what is happening when the resonant cavity is being excited by FM or other sources of phase noise.

the standing wave is constructed by the addition, in phase, of a continuous travelling wave. This travelling wave results in the forces that are produced on the end plates which are orthogonal to the group velocity vector of the wave. In a cavity with the correct radius spherical end plates there is no force on the side walls due to the travelling wave, because the walls are parallel to the group velocity vector

The forces produced by travelling waves in a waveguide were first investigated theoretically and experimentally by Prof. Alex Cullen back in the 1950s. His analysis is as true today as it was when he first did the work

.. There is a very neat quantum mechanical reason that such a container is not truly closed. Even in an infinite potential well, the wave function can extend outside the walls of the well, leading to effects such as tunneling. Another great example of the wavefunction extending beyond barriers that appears to be somewhat related to the possible effect seen here is the Aharanov Bohm effect: http://en.wikipedia.org/wiki/Aharonov%E2%80%93Bohm_effect. This is due to the wavefunction of a particle outside of a container extending past the barrier of the container and interacting with the EM field on the inside of the container....