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#100
by
Monomorphic
on 12 Mar, 2016 07:15
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First, how would you inject light into the frustum? I imagine that would require a hole in one of the end plates which would reduce the Q.
I've only found a few ways to inject laser light into a frustum-shaped optical cavity and have the beam remain stable as it bounces between end-plates. One of the methods requires the side walls.
The best method, of course, would be to generate the photons in the frustum itself - by filling the frustum with a gain medium, such as CO2 and N2, or HeNe, and attaching a cathode and anode. Though I'm not sure how well high voltage electrical discharges work in mirrored cavities!
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#101
by
TheTraveller
on 12 Mar, 2016 12:29
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Phil, I don't know where you get your "mirror coating would need to be 10x skin depth thickness", or "Rf penetrates 5x skin depth". Skin depth is an engineering convenience, and nothing else, based on 1/e, ( inverse natural logarithm) of energy depletion of an electromagnetic wave in a conductor. In other words, the wave rapidly depletes within the conductor to the point that its field strength becomes effectively negligable.
http://daycounter.com/Calculators/SkinEffect/Skin-Effect-Calculator.phtmlSkin depth is defined as the distance below the surface where the current density has fallen to 1/e or 37% of its value at the surface.
To get close to 100% reduction in current density below the surface density requires 5x skin depth and not the ~37% at 1x skin depth penetration.
In engineering terms this 1st ~37% drop is referred to as a 1 TC decline and to get full effect requires 5x. As it is for cavity fill and discharge time as it is for cap and inductors as it is for skin depth penetration.
Then assuming errors in the surface smoothness and possible surface pits, needs 10x to make an old engineers gut sleep well at night.
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#102
by
TheTraveller
on 12 Mar, 2016 12:31
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P.S. Hanging around as I am very curious to see how the next experimenter is going about convincing herself/himself and others that the observed force is not the result of hot air. 
Careful there. Your bias is starting to show.
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#103
by
TheTraveller
on 12 Mar, 2016 13:09
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Here is a simple excel calculator to show how many reflections will occur from each end plate, depending on unloaded cavity Q 5 TC time, Rf freq and number of 1/2 resonant waves in the cavity.
Example attached shows that for a TXXX3 resonant mode at 2.45 GHZ with a unloaded cavity Q of 86.2k, there would be 45,731 reflection from each end plate, for every cycle of Rf input, until the Rf energy is totally thermalised or converted into an externally usable force over 27.998usec. Which is a good life time for 1 cycle of 2.45GHz input Rf energy.
45,731 reflections from each end plate is a lot to keep perfectly aligned and for them to not walk off to a wider separation point. Of course the end plate alignment also affects cavity Q as it affects wall losses.
At least now we have a way to calc how many reflection will occur from each end plate if we get the cavity built perfect to 10x skin depth accuracy or better.
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#104
by
Monomorphic
on 12 Mar, 2016 14:05
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SORRY I meant the height! 17.67cm
Okay thanks. I was wondering why is was so short! Looks like you have TE311, albeit not as strong as the TE311 I was able to locate by simulating large numbers of frustum dimensions.
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#105
by
X_RaY
on 12 Mar, 2016 15:13
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#106
by
Monomorphic
on 12 Mar, 2016 17:24
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X-RaY, out of curiosity, does your spreadsheet indicate that TE211 is possible with a frustum length of ~18cm? End-plate radius can be arbitrary. I've been trying to find larger dimensions that resonate at that mode, as the one I found was only ~12cm in length.
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#107
by
SteveD
on 12 Mar, 2016 17:39
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Here is a simple excel calculator to show how many reflections will occur from each end plate, depending on unloaded cavity Q 5 TC time, Rf freq and number of 1/2 resonant waves in the cavity.
Example attached shows that for a TXXX3 resonant mode at 2.45 GHZ with a unloaded cavity Q of 86.2k, there would be 45,731 reflection from each end plate, for every cycle of Rf input, until the Rf energy is totally thermalised or converted into an externally usable force over 27.998usec. Which is a good life time for 1 cycle of 2.45GHz input Rf energy.
45,731 reflections from each end plate is a lot to keep perfectly aligned and for them to not walk off to a wider separation point. Of course the end plate alignment also affects cavity Q as it affects wall losses.
At least now we have a way to calc how many reflection will occur from each end plate if we get the cavity built perfect to 10x skin depth accuracy or better.
Urm, I don't suppose anybody can hack a simulator to check this to see if bounces off the sidewalls cause one endplate to undergo more bounces than the other. While CoM says it shouldn't matter, it would be nice to have the data to make sure nothing odd is going on.
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#108
by
X_RaY
on 12 Mar, 2016 17:52
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X-RaY, out of curiosity, does your spreadsheet indicate that TE211 is possible with a frustum length of ~18cm? End-plate radius can be arbitrary. I've been trying to find larger dimensions that resonate at that mode, as the one I found was only ~12cm in length.
TE211@≈2.45GHz
Small Diameter=99mm
Big Diameter=149mm
Center Length=180mm
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#109
by
aero
on 12 Mar, 2016 19:35
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@ Dr. Rodal,
You may have already explained this but I can't rely on memory.
It is difficult to find Drude model parameters for metals and I am looking for Silver. Plus, data that I do find is not guaranteed to compare to DeltaMass's detailed derivation for copper.
Is it fair to simply multiply CU conductivity I'm using from DeltaMass by the ratio silver-conductivity divided by copper-conductivity where I use silver and copper conductivities from a published source?
My source gives conductivities, Ag = 62.1 and CU = 58.5
aero
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#110
by
Rodal
on 12 Mar, 2016 20:55
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@ Dr. Rodal,
You may have already explained this but I can't rely on memory.
It is difficult to find Drude model parameters for metals and I am looking for Silver. Plus, data that I do find is not guaranteed to compare to DeltaMass's detailed derivation for copper.
Is it fair to simply multiply CU conductivity I'm using from DeltaMass by the ratio silver-conductivity divided by copper-conductivity where I use silver and copper conductivities from a published source?
My source gives conductivities, Ag = 62.1 and CU = 58.5
aero
Please refresh my mind
A) (preferably) by linking to my messages where I provided the Meep input for copper (I can't find them) or
B) otherwise by giving me the actual Meep input you use for copper properties
Thanks
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#111
by
SeeShells
on 12 Mar, 2016 21:24
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@ Dr. Rodal,
You may have already explained this but I can't rely on memory.
It is difficult to find Drude model parameters for metals and I am looking for Silver. Plus, data that I do find is not guaranteed to compare to DeltaMass's detailed derivation for copper.
Is it fair to simply multiply CU conductivity I'm using from DeltaMass by the ratio silver-conductivity divided by copper-conductivity where I use silver and copper conductivities from a published source?
My source gives conductivities, Ag = 62.1 and CU = 58.5
aero
Please refresh my mind
A) (preferably) by linking to my messages where I provided the Meep input for copper (I can't find them) or
B) otherwise by giving me the actual Meep input you use for copper properties
Thanks
This what you're looking for?
https://forum.nasaspaceflight.com/index.php?topic=38577.msg1451836#msg1451836Scroll down for more info.
Back to building.
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#112
by
aero
on 12 Mar, 2016 23:04
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@ Dr. Rodal,
You may have already explained this but I can't rely on memory.
It is difficult to find Drude model parameters for metals and I am looking for Silver. Plus, data that I do find is not guaranteed to compare to DeltaMass's detailed derivation for copper.
Is it fair to simply multiply CU conductivity I'm using from DeltaMass by the ratio silver-conductivity divided by copper-conductivity where I use silver and copper conductivities from a published source?
My source gives conductivities, Ag = 62.1 and CU = 58.5
aero
Please refresh my mind
A) (preferably) by linking to my messages where I provided the Meep input for copper (I can't find them) or
B) otherwise by giving me the actual Meep input you use for copper properties
Thanks
I have these:
Rodal's explaination of how to ratio conductivity.
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453093#msg1453093 or better -
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316 and one following
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#113
by
rfmwguy
on 13 Mar, 2016 00:40
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Optical polishing almost done. Before and after pics of small endplate of NSF-1701A
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#114
by
aero
on 13 Mar, 2016 00:47
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Hmm - Before and after? or after and before
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#115
by
rfmwguy
on 13 Mar, 2016 01:35
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After and before...from top to bottom
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#116
by
SeeShells
on 13 Mar, 2016 01:49
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Optical polishing almost done. Before and after pics of small endplate of NSF-1701A
Very nice work!!!
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#117
by
zen-in
on 13 Mar, 2016 03:01
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Optical polishing almost done. Before and after pics of small endplate of NSF-1701A
Nice polishing job. You can use it as a faux bronze age mirror. I did something similar a few weeks ago. The brass disk (before and after) is the cover plate for a diesel engine water pump. Instead of buying a replacement I machined it flat then polished it. Later I found 2 new cover plates in a locker.
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#118
by
CW
on 13 Mar, 2016 07:27
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I can see 4 atoms sticking out of the surface. Will it be precise enough to cause the Shawyer effect?
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#119
by
TheTraveller
on 13 Mar, 2016 12:05
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http://www.bbc.co.uk/programmes/b0752f85Project Greenglow - The Quest for Gravity Control
Horizon, 2015-2016
This is the story of an extraordinary scientific adventure - the attempt to control gravity. For centuries, the precise workings of gravity have confounded the greatest scientific minds - from Newton to Faraday and Einstein - and the idea of controlling gravity has been seen as little more than a fanciful dream. Yet in the mid 1990s, UK defence manufacturer BAE Systems began a ground-breaking project code-named 'Greenglow', which set about turning science fiction into reality. On the other side of the Atlantic, Nasa was simultaneously running its own Breakthrough Propulsion Physics Project. It was concerned with potential space applications of new physics, including concepts like 'faster-than-light travel' and 'warp drives'.
Looking into the past and projecting into the future, Horizon explores science's long-standing obsession with the idea of gravity control. It looks at recent breakthroughs in the search for loopholes in conventional physics and examines how the groundwork carried out by Project Greenglow has helped change our understanding of the universe. Gravity control may sound like science fiction, but the research that began with Project Greenglow is very much on-going, and the dream of flying cars and journeys to the stars no longer seems quite so distant.
The program segment will probably be geo blocked outside the UK. Do trust it will make the jump to open access YouTube.
