Please correct me if I'm wrong, but from what I understand (not being trained in university physics), meberbs thinks the photon force on all the walls of the cavity theoretically cancel each other out.Assuming I'm summarising meberbs correctly, do other people agree with that? And if not, why not?
After finishing up on another experiment yesterday, I was able to mount the new laser cavity and laser assembly to the thrust balance. The experiment weighs in at 550 grams, and since one has to add an equal counterweight to the other side, that brings the total added mass to 1100 grams! Adding the mass of the aluminum arm, damping, and other parts, the total mass of the torsional pendulum is ~1450 grams. That is 3.2 lbs. Each of the flexure bearings has a load capacity of 3.6 lbs (1630 g). Since there are two of them, that comes to 7.2 lbs (3260 g). So I am very near half the load capacity of the bearings. With the added mass, the moment of inertia increased substantially. Damping had to be increased quite a bit to compensate. All this increases the period of the balance. So when it was ~7 seconds, it will be probably double that, if not more. I adjusted the damping today, but forgot to measure the oscillation period. We will see what that is when I run a few calibration pulses later. The procedure for testing will be to make all major adjustments and changes to the laser cavity on the work bench, and then when that is complete, move the cavity assembly to the torsional pendulum and simply connect the two wires. Then make any last minute adjustments on the pendulum and then ~2W powered tests.
Is the purpose of this experiment to test a visible light version of the EM drive concept using lasers? Yes. Are you looking for thrust? Yes.And is it not required that one uses a spherical wave source, not lasers? Not according to McCulloch. And if you are looking for thrust (I don't know) Are you not concerned about leaks since your cavity is not closed?It was shown previously in simulations that the laser can bounce an arbitrarily large number times using special arrangements of mirrors. However, after 30 - 40 bounces, most of the laser energy is lost because the mirrors are not perfect. The hope is that an anomalous effect can be detected within the first 30 - 40 bounces if the laser energy is high enough.
Quote from: Mark7777777 on 06/21/2020 03:01 amPlease correct me if I'm wrong, but from what I understand (not being trained in university physics), meberbs thinks the photon force on all the walls of the cavity theoretically cancel each other out.Assuming I'm summarising meberbs correctly, do other people agree with that? And if not, why not?Not speaking for meberbs, but in general, this is correct for a completely enclosed cavity. (If you're missing a wall such that your beam can ultimately escape, then what you've constructed is a photon rocket. Monomorphic's build is currently closer to the latter, but it's still quite early. Give him time.)That said, the nature of the cancelling forces could probably use some clarification as I'm seeing a lot of thought experiments that are mixing transient effects with steady state effects; which is a great way to arrive at a non-physical conclusion.The main issue is that a phrases such as "the photon transfers momentum to the cavity" are actually very ill-defined because an incident photon cannot interact with the entire cavity all at once. At best, it can only interact with a handfull of atoms at a time. These initial interactions will eventually propagate to the rest of the cavity structure, but that takes time. Specifically, those propagations travel at about the speed of sound through the cavity material; compared to a reflecting photon that travels at the speed of light. This effectively means that a photon will bounce back and forth hundreds of thousands of times before the "impact" of any one bounce reaches the other side of the cavity. Thus, due to the drastic difference in propagation velocities, even the very first photon entering and bouncing aroundthe cavity ultimately results in a force outward, not forward.The red shift / blue shift tug of war is not due to translational movement of the cavity as a whole, but instead due to expansion vs compresson of the cavity walls due to internal photonic pressure. The outward pressure due to a photons initial reflections cause the cavity to expand slighty, placing the whole system in tension; not unlike an (infinitessimally) inflated balloon. Soon, the photon is no longer energetic enough to maintain that outward pressure, and the cavity contracts; transferring energy back to the reflecting photon. In the real world, there are many other kinds of energy loss that will eventually completely consume a photon. But if we continually replace lost photons with new ones such that the internal photonic pressure is maintained, then the system will settle to an equilibrium where, on average, reflecting photons impart no momentum to the cavity walls.
If that's the case I'm not sure about photon acceleration though. Mike says that velocity won't cause a horizon, but rather only acceleration. I thought photons reached the speed of light instantly so there is no acceleration in them. And therefore the laser beam just goes bouncing around the cavity at a constant velocity (c), but with no acceleration.
Quote from: crow_kraehe on 07/07/2020 09:33 pmIs the purpose of this experiment to test a visible light version of the EM drive concept using lasers? Yes. Are you looking for thrust? Yes.And is it not required that one uses a spherical wave source, not lasers? Not according to McCulloch. And if you are looking for thrust (I don't know) Are you not concerned about leaks since your cavity is not closed?It was shown previously in simulations that the laser can bounce an arbitrarily large number times using special arrangements of mirrors. However, after 30 - 40 bounces, most of the laser energy is lost because the mirrors are not perfect. The hope is that an anomalous effect can be detected within the first 30 - 40 bounces if the laser energy is high enough.
Quote from: Bob Woods on 07/09/2020 03:05 amIs this the same BAE Corp that partnered with Shawyer?I do not know.
Is this the same BAE Corp that partnered with Shawyer?
Are you in contact with Mike McCulloch? Or, are you in contact with Tajmar who is actually is testing McCulloch's concept?
Quote from: Bob012345 on 07/08/2020 08:24 pmAre you in contact with Mike McCulloch? Or, are you in contact with Tajmar who is actually is testing McCulloch's concept? I am in contact with McCulloch and Tajmar on this matter. McCulloch was kind enough to estimate for me the thrust he would expect, which is 0.1 uN at 2 watts. Tajmar was already aware of the experiment from seeing it here when I emailed him about it. He said he was looking forward to the results.