This old dog has to be dealt with. There isn't much left besides this:Thermal instability technical paper from Rodal:http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293349#msg1293349
I have a question about how the thrust is usually measured. Is it a pendulum? if so, could a physical cavity deformation simply move the barycenter? that could be mistaken as thrust.Far from being an expert, I am still enjoying the thread
What I don't understand still is how that thermal buckling could appear as a sustained false thrust signature over 30-45 second runs, instead of just a quick impulse. Is it because the CG moved or something?
Quote from: Giovanni DS on 02/12/2015 08:18 pmI have a question about how the thrust is usually measured. Is it a pendulum? if so, could a physical cavity deformation simply move the barycenter? that could be mistaken as thrust.Far from being an expert, I am still enjoying the thread It is a horizontal torsional pendulum, with the torsional axis of rotation in the vertical direction (call it "z"), paralel to the direction of the force of gravity and hence perpendicular to the floor. The EM Drive's force produces a rotation around that vertical axis "z", such that the motion of the EM Drive occurs mainly in the x-y plane parallel to the floor, perpendicular to "z". There is a small amount of coupling between the rotations around z, rotation around x and rotation around y due to the moments of inertia. I wrote a program in Mathematica taking into account the nonlinear coupled equations of motion, thinking that the forces could be an artifact due to nonlinear coupling of the equations of motion but I after comparing with the data I rejected that possibility.
Quote from: Mulletron on 02/12/2015 08:10 pmThis old dog has to be dealt with. There isn't much left besides this:Thermal instability technical paper from Rodal:http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293349#msg1293349Agreed, all that NASA Eagleworks has to do to eliminate this artifact is:...get rid of the fiber-reinforced-polymer printed circuit board and just simply use a 1/4 inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from considerationhttp://forum.nasaspaceflight.com/index.php?topic=36313.msg1329239#msg1329239http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329424#msg1329424
For a perfectly cylindrical resonator we have a simple exact solution (see: http://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity ) all that one needs to do is to compare the frequency calculated by MEEP for a cylindrical cavity with the exact solution.
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 1.937115E+009 Hz. This would compare directly to the situation presented yesterday, except the dielectric has been removed.I note that by watching the development of the fields from the first half-period, the cavity resonance does not seem to be as strong. That is, the fields drift with time. The strong blue point moves.
Quote from: aero on 02/12/2015 09:01 pmAttached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 1.937115E+009 Hz. This would compare directly to the situation presented yesterday, except the dielectric has been removed.I note that by watching the development of the fields from the first half-period, the cavity resonance does not seem to be as strong. That is, the fields drift with time. The strong blue point moves.You calculated a force with the dielectric in the cavity, what force do you calculate without the dielectric?How does the force compare?
I accidentally stumbled upon this report:https://hal.archives-ouvertes.fr/hal-00551421v1/documentI'm still trying to find which reference it was where any of this implied non-reciprocity.
Magneto-electric directional anisotropy can be induced in all media, including centrosymmetricones. It was first predicted by G. E. Stedman and coworkers [11] and observed for the first time ina crystal by G. L. J. A. Rikken and coworkers [12]. This non-reciprocal effect is supposed to be independent on light polarization.
Quote from: Mulletron on 02/10/2015 11:06 pmI accidentally stumbled upon this report:https://hal.archives-ouvertes.fr/hal-00551421v1/documentI'm still trying to find which reference it was where any of this implied non-reciprocity.It does imply non-reciprocity:http://arxiv.org/pdf/1101.1174v1.pdfSection 2.1.QuoteMagneto-electric directional anisotropy can be induced in all media, including centrosymmetricones. It was first predicted by G. E. Stedman and coworkers [11] and observed for the first time ina crystal by G. L. J. A. Rikken and coworkers [12]. This non-reciprocal effect is supposed to be independent on light polarization.I'm sure any optics expert would tell me, well duh!
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 2.168E+009Hz. In this case, dielectric has been removed and the drive frequency has been increased. Increased drive frequency means that the actual simulated time is less than in the previous cases because the period is shorter.