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It has been suggested that the inside must be properly mirrored for the desired M/W resonance. The inside of that cone has to be conically flat. Dollars to donuts sez it ain't. Not if it is made of 1/8" thick copper. The inside may have been polished with Turtle Wax, but it has not been polished nor flattened to Hubble specs. The substrate is too thin. The exterior has a mill finish only. Was it formed over a wood mandrel? Who knows?
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No, it was not a suggestion. It is not based on words, or intuition. It follows from Maxwell's equations.
It is not based on looking at Wikipedia articles. It is not based on scouring the Internet looking at blogs.
It is based on looking at MIT Electrical Enginering course work material.
What was stated in
http://forum.nasaspaceflight.com/index.php?topic=29276.msg1273676#msg1273676It is based on this:
Q =( Length / skinDepthForResonantFrequency) / (1 + ( 2*Length / InnerDiameter ))
skinDepthForResonantFrequency = 1/Sqrt[Pi*ResonantFrequency*μ*σ]The statement was:
1) Both inner surface ends of the truncated cone must have been made out of copper. Otherwise the cavity would not have the correct boundary conditions to be a resonant cavity: it would be a waveguide. One wouldn't be able to have high Q and resonance if the inner surface of the ends wouldn't be copper.
2) The inner surface of the copper must have been pretty well polished, in order to get Q~50 000, given the calculated skin depths
3) There cannot be any significant irregularities on the inside surface of the truncated cone.
This follows from Maxwell's equations. If Shawyer reports for his demo Q=45000, then it must follow that either:
A) the inner surface of Shawyer's demonstration EM Drive must have been pretty well polished in order to obtain Q=45000,
without significant irregularities on its inside surface or
B) the reported Q=45000 is an incorrect reported value
Also observe that NASA Eagleworks did not report as high Q's as the Q=45000 reported by Shawyer for the demonstrator EM Drive. NASA Eagleworks reported Q's ranging from 7000 to 22000, which is significantly less (Q=7000 is 7 times less). Therefore, it must follow (from the solution to Maxwell's equations) that:
A) NASA Eagleworks truncated cone's inner surface was not as well polished and free of irregularities as Shawyer's demonstration EM Drive
or
B) the reported Q's are incorrect
John, you just cannot have a high Q with a poor, irregular surface on the inside, when the skin depth is a couple of micrometers or less. You don't need to exaggerate about Hubble specs or similar exaggeration not present in the statement that you are objecting to.
John, if there is no inner copper on the ends of the cavity (showing PCB board on the outside) then you cannot have a resonant cavity, so
the inner surface ends must have been made out of highly-conductive material like copper.
There is no way out of this:
reported Q's are giving us information about the inner surface and material of the cavities. If you claim that the inner surface of the ends was not made out of a highly conductive material like copper, then you are stating that the reported Q's are completely incorrect, if you state that the inner surface of the cavities was significantly irregular, then Q cannot reach 45000, and effectively you are stating that you think that the reported Q is incorrect.
Similarly regarding Shawyer's statement about Q's several orders of magnitude higher: the only way to obtain such Q's is to make the inner surface of the cavity out of superconducting material and have the cavity at temperatures where superconductivity can take place.