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What I was referring to is how in most of your graphs, after you turn your test article off, the graph shows a rising force acting in the opposite direction to the force you got when the device was turned on.



edit: to clarify, this:





Quote from: Star-Drive

We found that this slope change after the test article and RF amplifer were turned on for 10-to-20 seconds was apprently due to IR radiation from the amplifier's heatsink that is mounted on the back side of the torque penlulum on an 8" square platform was affecting the top C-flex bearing more than the lower one. We tried aluminum shielding the top bearing assembly from the heatsink IR source and managed to reverse the metioned thermal slope in the thrust plots, but after shielding the bottom one we could reduce it but still coundn't completely get rid of this thremal drift artifact. Currently we are just living with it.



Thanks for clarification.The near systematic downward slope after power-on runs on the present Eagleworks setup reported charts have been explained by Paul March in "Thread 1" as being due to heating of flexure bearings by the rf amplifier radiator (situated on the pendulum arm assembly, just behind those flexure bearings). From this post Then later in present thread, after reporting (as seen on later pictures of setup) some mitigation of the problem (IR insulation) Paul March made mention (don't have the link at hand) of heating of same flexure bearings by return currents from pendulum arm (rotating assembly) to ground (fixed assembly).In both cases, what would appear as increasing thrust "in the opposite direction" would be in factas the flexure bearings heat. The fact that the effect lasts (and increases) for long after power off would be due to thermal inertia and lag of thermal conduction between hot source and flexure bearings. That makes sense for IR heating from RF amp radiators, IMO less with return currents as they would directly bulk heat the supporting spring steel...Later on, my understanding is that team at Eagleworks was trying to explain those slopes still as thermal, but rather from expansion of test articles parts, and not exclusively as flexure bearings rest position drifts (not clear if this is still considered by them an important component or not). Also it is not clear if they are only considering that as "recoil effects" ( apparent thrust from m d²position/dt² of some part during thermal transients). Or if they are thinking hard about or heard my petition that, since the horizontal pendulum is not strictly horizontal after all (or rather, that the rotation axis is not strictly vertical),that the centre of mass of rotating assembly is not on said rotation axis (contrary to a Cavendish balance by construction), then there is a "direct drive" (not second order) between position of centre of mass and rest equilibrium of balance, ie. vertical_scale_on_charts(t)=arm_displacement(t)= lambda*position_centre_of_mass(t) + mu*thrust(t)with lambda still to be determined (because inconsistencies in reported parameters/results makes it a 1 order of magnitude unknown).The absence of second order derivative wrt time of CoMs position influence makes possible for a slowly moving CoM to induce a sustained (and even increasing) vertical measure on charts. I have not heard back of my remark that, given the inclination of axis toward the rear part of the experiment (as seen from front of vacuum chamber)the position of rotating assembly's CoM behind the axis, the orientation of said influence is contrary to what appears on the published slides when considering only recoil effects : a displacement to the left of some part of the test article (relative to fixation on pendulum arm) would induce a corresponding proportional shift in position to the left of pendulum arms front part (where displacement is measured). This is of course only valid within the given information (tilted toward back + rotating assembly CoM behind axis) collected so far.More problematic than those long lasting slow drifts in rest position after power on/off, is the fact that there seem to exist a continuum of situations in between slowly evolving charts (in response to excitation steps) and steep responses that serve as proof of real thrusts on the argument of their steepness (sorry for the poor wording). For instance, the rise and decay of the chart below (obtained in vacuum) show a very different time constant to reach and leave the "thrust" plateau than with the electrostatic calibration pulses with their clean square force(t) profile. The smoothed rise could be explained by change of tuning (effective received power) of the cavity, needing a "warm-up". But the smoothed decay is really a showdown. Off is off, there is no "warm-down" time to speak of for EM radiation to disappear (on the order of µs, given size and Q factor), and no electromagnetic/quantum theory could explain such a delay unless the vacuum is as heavy and viscous as oil or water. This lag in the decay, most visible in this particular chart, was already noticed by other contributors (sorry, can't remember).