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#1620
by
rfmwguy
on 26 Apr, 2016 00:49
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{snip}
The magnetic fields in the EM Drive are at microwave frequencies. In your case, using a magnetron this frequency is around 2.45 GHz +/- 2GHz.
{snip}
Is that +/- 2GHz right? It is very big.
Below is a realtime spec an video of a magnetron I was experimenting with. It is not +/-2 GHz, more like +/- 0.1 GHz, don't recall the settings, think I mentioned them in the video.
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#1621
by
1
on 26 Apr, 2016 01:06
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...Where this seems to be heading (in my lay-person theoretical musings) is this...Magnetic fields (B H) will extend outside the emdrive as they are not inhibited by the copper. ...
Dave,
The magnetic fields in the EM Drive are at microwave frequencies. In your case, using a magnetron this frequency is around 2.45 GHz +/- 2GHz.
Why do you think that the magnetic fields in a microwave cavity like the EM Drive will extend outside the EM Drive?
Why do you think that they are not inhibited by copper 1 mm thick or thicker?
What happened to the concept of skin depth, where the skin depth at these frequencies is only about 1 micrometer?
A brief (hopefully helpful) layman's expansion on this: Faraday's law requires* a changing magnetic field to induce an EMF of some kind which, for most situations, manifests as an electric field. This, of course, is quite vulnerable to all the of normal effects which quickly reduce E field strength to zero within a conductor. Even though the copper normally ignores** magnetic fields, the coupling of electric energy into magnetic and vice versa allows the copper to attenuate the combined fields quite effectively. And, of course, the faster the fields change (read: the higher the frequency in question), the more quickly a magnetic field becomes vulnerable, so to speak. Cavity frequencies at ~2.4 Ghz should be quite well contained.
That said, this still might be another variable to lock out. Apologies if it's been discussed in detail before. The cavity will keep most everything in, but it won't block low frequency or static magnetic fields. This would mean that the cavity could not be considered a closed, self contained environment in the presence of any such field. The Earths magnetic field is always an obvious suspect for anomalous forces, so I wonder if any of the setups tested so far were build with explicit magnetic shielding or if they simply relied on the copper to filter outside noise 'good enough'. Normal metals wont cut it in this case; perhaps one of the fine builders on here could run their experiment "naked" and then perhaps again surrounded by a layer of something like mu-metal and see if there's a difference? Wouldn't surprise me if the EW guys ran theirs in a magnetically shielded chamber but I worry about the results from our homebuilders. Apologies again if this was discussed 4 threads ago and I'm just behind the times.
*Faradays' law doesn't actually
require anything per se, as Faraday discovered it rather than predicted it, but you all get the idea.
**For approximate values of 'ignore'
edit: clarity.
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#1622
by
Rodal
on 26 Apr, 2016 01:23
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...Where this seems to be heading (in my lay-person theoretical musings) is this...Magnetic fields (B H) will extend outside the emdrive as they are not inhibited by the copper. ...
Dave,
The magnetic fields in the EM Drive are at microwave frequencies. In your case, using a magnetron this frequency is around 2.45 GHz +/- 2GHz.
Why do you think that the magnetic fields in a microwave cavity like the EM Drive will extend outside the EM Drive?
Why do you think that they are not inhibited by copper 1 mm thick or thicker?
What happened to the concept of skin depth, where the skin depth at these frequencies is only about 1 micrometer?
A brief (hopefully helpful) layman's expansion on this: Faraday's law requires* a changing magnetic field to induce an EMF of some kind which, for most situations, manifests as an electric field. This, of course, is quite vulnerable to all the of normal effects which quickly reduce E field strength to zero within a conductor. Even though the copper normally ignores** magnetic fields, the coupling of electric energy into magnetic and vice versa allows the copper to attenuate the combined fields quite effectively. And, of course, the faster the fields change (read: the higher the frequency in question), the more quickly a magnetic field becomes vulnerable, so to speak. Cavity frequencies at ~2.4 Ghz should be quite well contained.
That said, this still might be another variable to lock out. Apologies if it's been discussed in detail before. The cavity will keep most everything in, but it won't quite keep everything out. The Earths magnetic field is always an obvious suspect for anomalous forces, so I wonder if any of the setups tested so far were build with explicit magnetic shielding or if they simply relied on the copper to filter outside noise 'good enough'. Normal metals wont cut it in this case; perhaps one of the fine builders on here could run their experiment "naked" and then perhaps again surrounded by a layer of something like mu-metal and see if there's a difference? Wouldn't surprise me if the EW guys ran theirs in a magnetically shielded chamber but I worry about the results from our homebuilders. Apologies again if this was discussed 4 threads ago and I'm just behind the times.
*Faradays' law doesn't actually require anything per se, as Faraday discovered it rather than predicted it, but you all get the idea.
**For approximate values of 'ignore'
YES:
1) There is absolutely NO significant magnetic field at 2 GHz escaping the EM Drive with a copper thickness of 1 mm, unless there are significant open gaps between the copper sheets. The magnetic field decays exponentially through the copper and the skin depth is only 1 micrometer at 2.45 GHz.
At a thickness of 1 mm you have an exponential decay 1,000 times that, one can calculate how small is that: there is no way that the equipment used by Dave can measure such a small trace amount, unless he has a significant open gap in the construction.
2) If Dave measured a magnetic field outside the EM Drive, and this is not an artifact, it maybe due to a 60 Hz AC component from the magnetron
or from a permanent magnet. It is not a 2 GHz magnetic field, unless he has a gap through which the electromagnetic field is escaping, in which case he has a safety problem, as the microwave field is dangerous, particularly to the human brain (monkeys have died in experiments with about 100 watts of microwave power).
3) You are absolutely right that the Earth's magnetic field can penetrate the 1mm thick copper EM Drive. Any static or very low frequency magnetic field can penetrate the 1 mm copper thickness. Such static or low frequency magnetic fields are difficult to shield.
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#1623
by
1
on 26 Apr, 2016 02:04
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OK, let's be clear:
[good stuff]
Completely agreed on all points. My previous post is meant to support yours; I just needed a bit of preface to lead into the question of possible internal magneto-static interactions. Wouldn't surprise me if there were a higher order term in play that we would have normally binomial expansion-ed into oblivion.
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#1624
by
rfmwguy
on 26 Apr, 2016 02:24
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The approximate 100 gauss H field extended out to about 7 feet. It looked like a 60 cycle pulsed field from a standard kitchen microwave, unmodified. RF leakage was relatively small. H field was steady state near keypad when powered off. Suspect that was ring magnets of magnetron. There is non-microwave magnetic fields escaping the rf shielded microwave cabinet when powered on. Quite high actually. While H field is debated, some say more than 3 gauss can effect those with high sensitivity. Microwave radiation leak was minimal. I was able to get an alarm on a leak detector but had to place it against door seam, so rf wise, the thing is good. I suspect the new frustum will be leak free. I'll test with a spec an, leak detector and the trifield which has relative rf signal strength. Thanks for the inputs to all. Tomorrow the cone gets soldered...will be out of touch most of the day except for breaks.
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#1625
by
Rodal
on 26 Apr, 2016 02:29
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The approximate 100 gauss H field extended out to about 7 feet. It looked like a 60 cycle pulsed field from a standard kitchen microwave, unmodified. RF leakage was relatively small. H field was steady state near keypad when powered off. Suspect that was ring magnets of magnetron. There is non-microwave magnetic fields escaping the rf shielded microwave cabinet when powered on. Quite high actually. While H field is debated, some say more than 3 gauss can effect those with high sensitivity. Microwave radiation leak was minimal. I was able to get an alarm on a leak detector but had to place it against door seam, so rf wise, the thing is good. I suspect the new frustum will be leak free. I'll test with a spec an, leak detector and the trifield which has relative rf signal strength. Thanks for the inputs to all. Tomorrow the cone gets soldered...will be out of touch most of the day except for breaks.
I made a video of H field leakage outside the aluminum and stainless steel kitchen microwave which one would think is well shielded from the factory...not.
{video]
I am assuming copper will also pulse radiate (rotate?) the H field. The difficulty is separating out the 60 hz pulse from any rotating "spokes" which I already alluded to. I'll simply have a ~10% relative meter accuracy and not capable of analyzing any overall fields beyond a few points. I am far from CE/EMC lab capabilities. There are 2 permanent ring magnets that are part of the magnetron assembly.
There will not be H or B field at 2 GHz escaping through 1 mm copper., not pulsing outside, not radiating outside, nothing outside at 2 GHz (unless you have gaps through which the microwave field is escaping, which is a safety hazard).
The magnetic field from any permanent magnet or 60 Hz magnetic field component will escape through the 1 mm copper, but I fail to see how will that explain any anomalous force from the EM Drive, other than as an experimental artifact, is that what you are implying ?.
Are you implying that the EM Drive experimental "anomalous force" measured by Shawyer and Yang using magnetrons maybe experimental artifacts by the permanent magnet from the magnetron, interacting with the Earth's magnetic field ? Or from the 60 Hz magnetic field escaping?
If that is what you are implying, yes, I agree, that is definitely a possibility, just like the Lorentz cable forces discussed by Mr. Li.
You definitely cannot fulfill the claims of EM Drive researchers like Shawyer, Yang, etc. by having a permanent magnet inside a truncated cone cavity or a 60 Hz magnetic field escaping a truncated cone copper cavity with 1 mm thick walls in outer space.
There are much better ways to have propulsion by using a planet's magnetic field:
https://en.wikipedia.org/wiki/Electrodynamic_tether
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#1626
by
rfmwguy
on 26 Apr, 2016 03:19
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Best way to describe what I'm doing is working on eliminating classical reasons for the force I observed. Nothing at a quantum level; E and H field investigation, lorentz force elimination. Mr Li demonstrated lorentz force, his guidance will hopefully keep me on the right pace...he estimated I had very little with my first tests. The ring magnets and magnetron are outside the frustum. Any fields, pulsed or rotating will be a direct result of the contained em radiation generating H fields that escape the frustum. This will be likely 60 hz, perhaps quite complex if spokes or rotation occurs as in the sputtering papers I've been researching. It is too early to make a claim on the emdrive effect being related to H field interaction with the earths natural magnetic field. I've chosen to stick with eliminating classical explanations first then move on to something more exotic. Feel comfortable lorentz is not the cause, whether the induced H field characteristics are, I'm not certain yet. Can say that the shape of the magnetic field is probably similar to the frustum shape. If it is rotating, you have the potential of a magnetic "auger". Therefore, the positioning of the emdrive relative to N S E and W will be quite interesting to record. I noticed Aachen had reduced force in a reverse direction...earth magnetic field interaction? Don't know...yet.
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#1627
by
demofsky
on 26 Apr, 2016 07:04
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#1628
by
SeeShells
on 26 Apr, 2016 07:38
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#1629
by
Monomorphic
on 26 Apr, 2016 12:15
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#1630
by
rfmwguy
on 26 Apr, 2016 12:23
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Thanks guys, for 8 bucks, why not try? Just placed my order for the 4x6 inch sheet. May not be fast enough to resolve any rotation, but certainly worth a shot.
Tell you one thing that crossed my mind, rotating H fields are nothing new. Everybody has an electric motor or generator somewhere. However, rotating H fields with no rotating mass? Not so much. If you look at the magnetron cross section, its a ring of rotating electrons. Guess its possible the em injection from the radome might be as well. Then couple that with the funnel shape of the frustum which naturally would rotate fluid and perhaps ions and electrons during deposition or self sputtering. Very speculative for sure, but interesting enough to keep my working theory alive.
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#1631
by
Rodal
on 26 Apr, 2016 13:01
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Thanks guys, for 8 bucks, why not try? Just placed my order for the 4x6 inch sheet. May not be fast enough to resolve any rotation, but certainly worth a shot.
Tell you one thing that crossed my mind, rotating H fields are nothing new. Everybody has an electric motor or generator somewhere. However, rotating H fields with no rotating mass? Not so much. If you look at the magnetron cross section, its a ring of rotating electrons. Guess its possible the em injection from the radome might be as well. Then couple that with the funnel shape of the frustum which naturally would rotate fluid and perhaps ions and electrons during deposition or self sputtering. Very speculative for sure, but interesting enough to keep my working theory alive.
This is testable:1) If this would be so, how would the anomalous force in EM Drives that don't use a magnetron be justified. It is not just that NASA did not use a magnetron, but that I understand TheTraveller as stating that Shawyer no longer uses a magnetron. (Shawyer did not use a magnetron for Boeing's Flight Thruster ?).
2) If the frustum of a cone shape would work as a funnel shape to rotate fluid into a screw,
shapes that are not rotationally axisymmetric, like the new wedge shape being championed by Shawyer would not (make a funnel out of the wedge shape and see what happens to the fluid), so Shawyer's new wedge shape should be a dud:
1) Frustum of a cone
2) "Wedge" or "truncated prism with rectangular bases"
Looking forward to Monomorphic's test with the standard truncated cone shape and the wedge shape to compare to see whether the wedge shape is indeed a dud.
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#1632
by
rfmwguy
on 26 Apr, 2016 13:12
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Very true, a non magnetic pulsed source may have no rotating H field component at injection point. I might be induced by the frustum depending on injection point and type of antenna or radome. Still a lot of questions and testing before any ah-ha proclaimations of a supercharged Lorentz auger
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#1633
by
Monomorphic
on 26 Apr, 2016 13:16
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I'll start work on cutting the pieces for the wedge today. I'm hoping to incorporate a waveguide this time, instead of direct insertion of the magnetron.
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#1634
by
Eusa
on 26 Apr, 2016 13:23
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In my understanding the thrust could be the effect of alerted gravity field (not of em-momentum) and the point would be a standing wave not the difference in area between small and large plates. That's why the plate must be spherical reflector.
Wondering if anyone has built that kind of chamber...?
I'm busy with big building projects, I cannot begin to craft the g-drive of my own. Honestly, I'm very suspicious that nonpropellant thrust is a genuine phenomenon. Still, if new tests can prove that acceleration is obvious, I'm in.
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#1635
by
Eusa
on 26 Apr, 2016 13:27
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I'll start work on cutting the pieces for the wedge today. I'm hoping to incorporate a waveguide this time, instead of direct insertion of the magnetron.
Would it be hard to make cylinder-slice-formed top and bottom plates with common curvature center?
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#1636
by
OttO
on 26 Apr, 2016 13:34
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#1637
by
Rodal
on 26 Apr, 2016 13:43
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In my understanding the thrust could be the effect of alerted gravity field (not of em-momentum) and the point would be a standing wave not the difference in area between small and large plates. That's why the plate must be spherical reflector.
Wondering if anyone has built that kind of chamber...?
I'm busy with big building projects, I cannot begin to craft the g-drive of my own. Honestly, I'm very suspicious that nonpropellant thrust is a genuine phenomenon. Still, if new tests can prove that acceleration is obvious, I'm in.
Tajmar's experiments at TU Dresden are claimed to have been performed with a truncated cone having spherical ends, per advice of Shawyer.
Tajmar's experiments resulted in one of the lowest force/InputPower claimed by any EM Drive experimenter up to date: 0.0286 mN/kW under partial vacuum in a torsional pendulum. That is barely 8.5 times greater than the force/InputPower of a perfectly collimated photon rocket. They claimed 0.1636 mN/kW in a teeter-totter under ambient pressure. That is only 49 times the force/InputPower of a perfectly collimated photon rocket, compared to Prof. Yang using flat-ended EM Drive claiming 320,000 times the force/InputPower of a perfectly collimated photon rocket.
Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects
M. Tajmar and G. Fiedler
Institute of Aerospace Engineering, Technische Universität Dresden, 01062 Dresden, Germany
http://bit.ly/1XVP8yfOur final tapered cavity design had an internal top radius of 38.5 mm, a bottom radius of 54.1 mm and a height of 68.6 mm
___________________
Also, I seem to recall that TT may have stated (based on
attributed personal communications) that Shawyer's Flight Thruster may have had spherical ends. Unfortunately this is difficult to independently verify as Shawyer's reports do not give all the geometrical dimensions for any of his tests (the reader being condemned to having to estimate geometrical dimensions from photographs, drawings or from his Design Factor calculation).
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#1638
by
Monomorphic
on 26 Apr, 2016 13:47
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#1639
by
Rodal
on 26 Apr, 2016 13:49
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