The Philtec datasheets describe the RC type distance sensors (RC90, etc) as having 2 adjacent bundles of fibers. The distance sensor used by Eagle Labs is a D63. For a Philtec sensor with 2 bundles of fibers the change in output voltage due to an angular change is dependent on the orientation of the sensor.
Whether the small negative slope in the thrust waveform after RF power is applied is from a change in CM causing a tilt in the mirror or is actually a displacement is impossible to determine emperically.
However it is there - along with the anomalous thrust signature, the magnetic interaction at 5.6 A., and the calibration waveforms from the capacitor. Maybe what looks like a thermally induced drift is just random movement.
In the Aug. AIAA paper one of the thrust waveforms (shown below) has an unusual shape. It is bracketed by 300 V. calibration pulses on the capacitor. The calibration pulses have some overshoot/undershoot and ringing that are the typical response of an underdamped system to step responses. This response is determined by the time constant and damping of the apparatus and should not change whatever the driving function is. For example if a fly bumped into the TP and imparted the same momentum as the capacitor with its 300V did, the response should be virtually identical. So why is the response from the RF being switched on and then off (anomalous thrust) so different?
Yes this fig. 22 chart (TE012, 2.6W, 55.4µN reported) is unusual, not time stamped, no vertical scale indications, cal. pulses at 300V 60.1µN instead of the usual 200V 29.1µN (note the non relative proportionality), and very smooth rises and falls for thrust pulses compared to cal. pulses. The overshoot and undershoot would be the same for responses to step rises and falls. The most likely explanation for the lack of ringing for the thrust pulse compared to cal. pulses is that the thrust case the driving function would not be steplike. That particular chart was discussed in thread 1 : http://forum.nasaspaceflight.com/index.php?topic=29276.msg1280094#msg1280094. And even for more "ringing" thrusts responses (more consistent with cal. pulses, like in fig.19) there is still not enough ringing to be explained by a pure step thrust. See bottom pic. in this link to have an idea of what might be the shape of the driving function to explain that. My recollection is that all this semi-quantitative reasoning on relative ringing overshoots hasn't reached general consensus.
FYIJust to get a feel for dielectrics I tried the straight cylinder with a uniform dielectric variation from end to end.Using the same simpleminded approximation as the tapered cylinder gives:del f = ( f/(2*c^2)) * (c1^2-c2^2)T = (h*f/(2*L*c^2)) * (c1^2-c2^2)NT = (P*Q/(4*pi*L*f*c^2)) * (c1^2-c2^2)Which is a lot simpler than I might have expected. Perhaps the approximation is too simple or it represents a special case with " uniform dielectric variation from end to end " rather than a straight conical insert.In any case, it seems to be telling me to look for the proper integral form to be doing these.
Well, this isn't going to work for a step function the way it is. We need to find the integral representation along the axis to be able to do that. This is only a close (?) approx for the uniform variation.L may go down but f goes up.......c is the only thing that varies here (no step)Might try a fourier expansion next. Have to think about that.....ADDED: Can you generate f^4 for the step function? Hard to do by hand on Post-it Notes !
An intriguing possibility for further increasing themagnitude of the force is slow-light enhancement,since the force increases as 1/vg for fixed input power.20We note that the electrostatic force due totrapped or induced charges in Si waveguides is esti-mated to be at least an order of magnitude smallerthan the optically induced force. The Casimir–Lifshitz force is even smaller. Optical evanescent ...
That is a good thread BTW. Those guys are harsh and I like it. I value reading outside opinions because I don't want to get caught up in my own little bubble and lose insight, like I did for a large part of thread 1.
I came across an interesting bit of information while doing background reading on evanescent wave forces.QuoteAn intriguing possibility for further increasing themagnitude of the force is slow-light enhancement,since the force increases as 1/vg for fixed input power.20We note that the electrostatic force due totrapped or induced charges in Si waveguides is esti-mated to be at least an order of magnitude smallerthan the optically induced force. The Casimir–Lifshitz force is even smaller. Optical evanescent ...Quoting from this document:http://math.mit.edu/~stevenj/papers/PovinelliLo05.pdf
We've been laser-focused on materials with greater dielectric constants, but what about materials with similar dielectric constants, like fused quartz? Will the EM drives behave differently?
@ RODALJust got a minute but from your p expression;If L1/c1 = L2/c2del f = (1/2*f)*((c1*c2)/(L1*L2))*b^2*((1/dD1^2)-(1/dD2^2))might be a solution ??Got to check the thinking later.Night !
Quote from: RotoSequence on 03/09/2015 11:07 pmWe've been laser-focused on materials with greater dielectric constants, but what about materials with similar dielectric constants, like fused quartz? Will the EM drives behave differently?If Paul March discussed testing with dielectric materials other than Teflon and HD PE, I don't recall. It would be interesting if Paul could comment (or if Paul already discussed this, if somebody could bring the experimental results to our attention).I understand that Roger Shawyer tested non-polymer materials as dielectrics, but the specific results and the dimensions and material properties of the dielectrics tested were not disclosed (again, if anyone has more specific details, please bring them to our attention).