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#700
by
SeeShells
on 24 Dec, 2015 17:02
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...
Thanks for the link. Coming into the discussion around the 5th of November, I missed a lot.
My comments on the warm ends and cool side wall was more about the cool walls and her ceramics. Not so much surprise... I think her frustum walls are 1/4" copper while the ends are thinner and bonded to ceramic disks. (Assuming the epoxy was JB Weld.., from the pic, but I think she just called it magic...paste?)
I have had a ceramic coffee cup that when heated in a microwave would get so hot you could not touch it by anything other than the handle, while another ceramic cup would just be warm to touch. Coffee in both at or above boiling... Coffee in the hot cup and the cup itself, would cool down very quickly.., while the other would remain hot longer.
When Shell gets the frustum back in working order and starts generating data, it would be important to know just what the thermal conductivity of her ceramic end plates are, when evaluating thermal data.
do we know what particular ceramic material Shell used?
Aluminum nitride and silicon carbide thermal conductivity is not that bad (about 1/2 that of copper), they are used in applications that emit heat. Zirconia's thermal conductivity is significantly lower than metals (about 1/20 that of copper), hence used for kiln walls, for example.
Also what matters for the EM Drive is the thermal diffusivity, rather than the thermal conductivity alone, because of the transient nature of the problem, hence the mass density of the ceramic is also important.
I don't remember her mentioning specifics, but then I only really read through thread 5 rather quickly. Gave up on the shear volume of the past threads, so what I know from the past is sketchy and based on very limited searches.
From the pictures it does look maybe 3/4 to an inch thick???
Bottom 3.17mm plate is 2.5mm thick of Alumina Ceramic, the top plate is 10mm. Bonded .032" .80mm O2 Free Copper.
The next frustum I'm using curved endplates and will be bonding two layers of carbon fiber to it ~ 6-10mm , First layer will be a highly thermally conductive mix and the second for strength. It's critical to keep the endplates from warping from the high energy modes.
I'll still be using the Quartz rod through the center, polished on both ends and mirrored on one for Laser Interferometer testing through the center of the Quartz rod so I can measure any time displacements.
Still will be using the tune chamber on the top but not as long and the one I have.
Merry Christmas ALL!
Shell
There are several people here that have more knowledge in doing a Laser Interferometer testing than me. I'll need to ask, could I only mirror one half of one end to measure a pulse going down and back and just through to see if the directional travel times differ?
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#701
by
Rodal
on 24 Dec, 2015 17:12
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...
Bottom 3.17mm plate is 2.5mm thick of Alumina Ceramic, the top plate is 10mm. Bonded .032" .80mm O2 Free Copper.
...
The thermal conductivity of Alumina (Aluminum Oxide) ceramic ranges from 12 to 39 W/m K) (SI units) compared to copper's 385.0 W/(m K) so, it is about 1/10 to 1/30 that of copper.
I understand from this that the thin Alumina ceramic was used only on the small end plate of the frustum of a cone. (The big end plate is copper)
The Alumina was only 2.5mm thick (1/10th of an inch, thin layer of Alumina).
When performing an Infrared Thermal Camera measurement, appropriate conversion of the image will have to be accommodated for the different emissivity of copper, as compared to Alumina, to properly interpret the surface temperaturesADDED==> This means that perhaps Shell could show two thermal camera images, one with the emmissivity of copper and one set for the emissivity of Alumina <===
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#702
by
OnlyMe
on 24 Dec, 2015 17:13
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.....
From the pictures it does look maybe 3/4 to an inch thick???
I guess that proves I still have a vivid imagination!
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#703
by
SeeShells
on 24 Dec, 2015 17:15
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.....
From the pictures it does look maybe 3/4 to an inch thick???
I guess that proves I still have a vivid imagination!
I bet you still believe in Santa.
I do.
Shell
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#704
by
Rodal
on 24 Dec, 2015 18:14
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OK - I have pushed meep as far as I can on my computer (Win 8, 8GB RAM, 1TB HD, 3Ghz quad core i7). Taking aero's CE3 file for SeeShells' device, I have updated the resolution from 250 to 275. This runs with 1 thread (in VirtualBox Ubuntu) using 85% of 6GB of RAM (maxing my computer RAM without thrashing the HD).
Have you tried using mpirun and multiple threads? I found using 3 out of 4 cores on my 6GB 2.1 GHz machine I cut resonance analysis run time about in half.
My goodness we are so lucky to have at out beckoned call these machines with gigabytes of ram and terabytes of storage. The very first computer system I did engineering work on was the Philco Ford 1000 with 32k of iron core memory and a asynchronous clock.
http://ed-thelen.org/comp-hist/BRL64-0224.jpg
Times have changed, software has changed and it's allowing us to help answer a very interesting problem.
I have a question that's bothering me. I have a calculated Q somewhere around 20-80 k in a TE013 mode and it can show mode movement or it can not according to meep. How long is that mode stable for? What can cause it to decay? How does the decay resemble the build during a increase of Q? Is it a mirrored operation? Does it depend on the power supply of a switching dirty maggie or will it just sit there with a high energy mode. Do ghost modes in a cavity influence the decays and growths in the frustum?
It seems to me that the rise of the mode and Q is governed and shaped more by the RF injection and then the cavity influences the decays more than the RF feed.
Dr. Rodal mentioned this several threads back and its stayed with me causing me to wonder why would a Q buildup in mode mirror the decay I can see where the frustum would be a huge factor in this. To me it's a question that hasn't been addressed, maybe it has and I missed it.
Would love to hear thoughts on this.
Good day away from building and just kind of nesting and thinking.
Shell
Shell, the knowledge base at present cannot answer your questions.., unless all observed thrust is explained by thermal effects and or systemic error.
Which means, if there is thrust clearly above systemic error and thermal effects, it will require something more than the current interpretation of the available knowledge base to answer your questions...
Right now you are our best hope for some clean data, which then may begin to lead somewhere.., that answers to your questions can be found.
I found it very interesting that your frustum walls were cool and the endplates warm....
On the idea that there may be some GR effect involved... Any alteration in Gravity, which is GR.., should be easy to test by attaching an accelerometer to both end plates and turning the thing on. If any distortion in spacetime (gravitation) occurs, it will show up on one or both accelerometers, even if the thing were bolted solid to the floor. Don't you have a raspberry something? that would work for that?, at least as a start. Or would it require something new?
<<found it very interesting that your frustum walls were cool and the endplates warm....>>
One simple interpretation of this, is that the experiment by Shell excited a Transverse Magnetic (TM) mode, as such a mode would result mostly in induction heating of the end plates (due to the transverse magnetic field induction heating the end plates). Purely a thermal effect resulting from classical electromagnetism, as one would expect from a microwave excitation of a cavity. Nothing esoteric.
This was confirmed by Paul March who provided a) thermal camera images and b) finite-element calculations showing the temperature distribution in the frustum of a cone for the transverse magnetic mode.
In more detail:
1) NASA's Finite Element analysis (using COMSOL) -in NASA's experimental case involving the mode shape for the frustum of a cone that is similar to TM212 in a cylindrical cavity
2) NASA's infrared thermal camera -that confirmed the mode shape for the frustum of a cone that is similar to TM212 in a cylindrical cavity
3) See the complete thermal analysis report by NASA, as a PDF attachment if you click this: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=634723
Conclusions:
COMSOL Predictions of Surface thermal losses shows very good agreement with Thermal IR data
• Surface heat distribution follows surface magnetic field distribution and not electric field distribution
• Thermal IR data is consistent with predictions using a single resonant mode (TM212)
PS: Induction heating of the small end in NASA's analysis is affected by the fact that the small end in NASA's experiment contains a polymer dielectric, while in Shell's experiment there is no polymer dielectric at the small end. Analysis without a polymer dielectric (that I conducted with an exact solution, using Mathematica) shows induction heating of both ends.
A number of people have posted their own graphical output of Meep fields. I showed my own analysis of such Meep files, using Mathematica for post-processing the data, in previous threads, and gave my viewpoint on how such data should be analyzed and viewed.
Rather than engage in unproductive arguments, with subjective views about what fields are best to analyze and how best to view them to understand what is going on, let's be practical (*):
Here is a practical suggestion on Meep runs that Meep users can conduct
Is your Meep model a realistic model of reality?
Can you use Meep's graphical output to interpret what is going on?
Let's verify it and then use it to make a prediction1) Verify (using Meep) the thermal camera measurements of NASA for their geometry, giving TM212 (
assuming that the thermal profile is due to induction heating). Take a look at NASA's report on how the COMSOL analysis of the magnetic field looks like. Compare that with Meep.
2) Run Shell's geometry to predict what the thermal camera should measure when viewing her experiment. (
assuming that the thermal profile is due to induction heating)
For example: does your Meep model predict mode TE013 ? Then show us what the thermal profile should look like, according to the Meep analysis of Shell's experiment (
assuming that the thermal profile is due to induction heating)
_____
(*) With my own R&D staff, the first thing that I would ask people engaged in numerical modeling is to show verification of their analysis vs. simple cases having exact solutions, and then vs. more complicated experimental data.
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#705
by
X_RaY
on 24 Dec, 2015 18:19
-
...
Thanks for the link. Coming into the discussion around the 5th of November, I missed a lot.
My comments on the warm ends and cool side wall was more about the cool walls and her ceramics. Not so much surprise... I think her frustum walls are 1/4" copper while the ends are thinner and bonded to ceramic disks. (Assuming the epoxy was JB Weld.., from the pic, but I think she just called it magic...paste?)
I have had a ceramic coffee cup that when heated in a microwave would get so hot you could not touch it by anything other than the handle, while another ceramic cup would just be warm to touch. Coffee in both at or above boiling... Coffee in the hot cup and the cup itself, would cool down very quickly.., while the other would remain hot longer.
When Shell gets the frustum back in working order and starts generating data, it would be important to know just what the thermal conductivity of her ceramic end plates are, when evaluating thermal data.
do we know what particular ceramic material Shell used?
Aluminum nitride and silicon carbide thermal conductivity is not that bad (about 1/2 that of copper), they are used in applications that emit heat. Zirconia's thermal conductivity is significantly lower than metals (about 1/20 that of copper), hence used for kiln walls, for example.
Also what matters for the EM Drive is the thermal diffusivity, rather than the thermal conductivity alone, because of the transient nature of the problem, hence the mass density of the ceramic is also important.
I don't remember her mentioning specifics, but then I only really read through thread 5 rather quickly. Gave up on the shear volume of the past threads, so what I know from the past is sketchy and based on very limited searches.
From the pictures it does look maybe 3/4 to an inch thick???
Bottom 3.17mm plate is 2.5mm thick of Alumina Ceramic, the top plate is 10mm. Bonded .032" .80mm O2 Free Copper.
The next frustum I'm using curved endplates and will be bonding two layers of carbon fiber to it ~ 6-10mm , First layer will be a highly thermally conductive mix and the second for strength. It's critical to keep the endplates from warping from the high energy modes.
I'll still be using the Quartz rod through the center, polished on both ends and mirrored on one for Laser Interferometer testing through the center of the Quartz rod so I can measure any time displacements.
Still will be using the tune chamber on the top but not as long and the one I have.
Merry Christmas ALL!
Shell
There are several people here that have more knowledge in doing a Laser Interferometer testing than me. I'll need to ask, could I only mirror one half of one end to measure a pulse going down and back and just through to see if the directional travel times differ?
Carbon Fiber reinforced Plastic (CFRP) have a much lower conductivity than full metal and therefore higher Ohmic losses. The resin matrix material also have a tang-delta. Carbon Fiber at the inner surfave of the cavity will decrease the Q!
I have a lot of experience with this point and many experimental data.
The first plot shows a conical metallic cavity where the small end plate is made of CFRP(large fiber density), the second the same resonator but with a copper plate at the small end. These are real measurement data, not FEM simulations.
The coupling is not optimal but is shows the difference. Resonant mode is TE011.
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#706
by
rfmwguy
on 24 Dec, 2015 18:42
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Appreciate your thoughts tellmeagain on the link to the other forum but it quickly devolved into useless commentary for rfplumber. I removed the link. Once holiday travels are over I'm sure many here can belp.
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#707
by
not_a_physicist
on 24 Dec, 2015 19:37
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Progress update on my pendulum-based test. While I cannot yet report on whether EmDrive is producing thrust or not (congrats to Shell!), I can at least report that a 50 Ohm dummy RF load is definitely not producing any 
. This is a good solid start; rumor has it that the only thing one needs to change now in order to obtain thrust is to use a frustum-shaped cavity instead of a dummy load… We shall see.
...
That is an impressive build! Could you post the CSVs you've generated so far, if you've saved them? It would be nice to have a little program read in a run and say "this data set shows non-zero thrust with probability X"
before there is any actual frustum data to overfit to, and I'd like to take a stab at that.
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#708
by
lmbfan
on 24 Dec, 2015 19:53
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Dr. Rodal:
I'm pretty sure SeeShell's large end plate is also copper backed ceramic (see update #4 images on her gofundme page).
X_RaY:
I'm also pretty sure Shell's bonding a thin layer of copper to the carbon fiber. The copper will be precisely shaped while the carbon fiber is for strength and thermal stability.
SeeShell:
Congratulations on your results! When your data gets here it will be just like Christmas all over again!
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#709
by
SeeShells
on 24 Dec, 2015 19:57
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OK - I have pushed meep as far as I can on my computer (Win 8, 8GB RAM, 1TB HD, 3Ghz quad core i7). Taking aero's CE3 file for SeeShells' device, I have updated the resolution from 250 to 275. This runs with 1 thread (in VirtualBox Ubuntu) using 85% of 6GB of RAM (maxing my computer RAM without thrashing the HD).
Have you tried using mpirun and multiple threads? I found using 3 out of 4 cores on my 6GB 2.1 GHz machine I cut resonance analysis run time about in half.
My goodness we are so lucky to have at out beckoned call these machines with gigabytes of ram and terabytes of storage. The very first computer system I did engineering work on was the Philco Ford 1000 with 32k of iron core memory and a asynchronous clock.
http://ed-thelen.org/comp-hist/BRL64-0224.jpg
Times have changed, software has changed and it's allowing us to help answer a very interesting problem.
I have a question that's bothering me. I have a calculated Q somewhere around 20-80 k in a TE013 mode and it can show mode movement or it can not according to meep. How long is that mode stable for? What can cause it to decay? How does the decay resemble the build during a increase of Q? Is it a mirrored operation? Does it depend on the power supply of a switching dirty maggie or will it just sit there with a high energy mode. Do ghost modes in a cavity influence the decays and growths in the frustum?
It seems to me that the rise of the mode and Q is governed and shaped more by the RF injection and then the cavity influences the decays more than the RF feed.
Dr. Rodal mentioned this several threads back and its stayed with me causing me to wonder why would a Q buildup in mode mirror the decay I can see where the frustum would be a huge factor in this. To me it's a question that hasn't been addressed, maybe it has and I missed it.
Would love to hear thoughts on this.
Good day away from building and just kind of nesting and thinking.
Shell
Shell, the knowledge base at present cannot answer your questions.., unless all observed thrust is explained by thermal effects and or systemic error.
Which means, if there is thrust clearly above systemic error and thermal effects, it will require something more than the current interpretation of the available knowledge base to answer your questions...
Right now you are our best hope for some clean data, which then may begin to lead somewhere.., that answers to your questions can be found.
I found it very interesting that your frustum walls were cool and the endplates warm....
On the idea that there may be some GR effect involved... Any alteration in Gravity, which is GR.., should be easy to test by attaching an accelerometer to both end plates and turning the thing on. If any distortion in spacetime (gravitation) occurs, it will show up on one or both accelerometers, even if the thing were bolted solid to the floor. Don't you have a raspberry something? that would work for that?, at least as a start. Or would it require something new?
<<found it very interesting that your frustum walls were cool and the endplates warm....>>
One simple interpretation of this, is that the experiment by Shell excited a Transverse Magnetic (TM) mode, as such a mode would result mostly in induction heating of the end plates (due to the transverse magnetic field induction heating the end plates). Purely a thermal effect resulting from classical electromagnetism, as one would expect from a microwave excitation of a cavity. Nothing esoteric.
This was confirmed by Paul March who provided a) thermal camera images and b) finite-element calculations showing the temperature distribution in the frustum of a cone for the transverse magnetic mode.
In more detail:
1) NASA's Finite Element analysis (using COMSOL) -in NASA's experimental case involving the mode shape for the frustum of a cone that is similar to TM212 in a cylindrical cavity
2) NASA's infrared thermal camera -that confirmed the mode shape for the frustum of a cone that is similar to TM212 in a cylindrical cavity
3) See the complete thermal analysis report by NASA, as a PDF attachment if you click this: http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=634723
Conclusions:
COMSOL Predictions of Surface thermal losses shows very good agreement with Thermal IR data
• Surface heat distribution follows surface magnetic field distribution and not electric field distribution
• Thermal IR data is consistent with predictions using a single resonant mode (TM212)
PS: Induction heating of the small end in NASA's analysis is affected by the fact that the small end in NASA's experiment contains a polymer dielectric, while in Shell's experiment there is no polymer dielectric at the small end. Analysis without a polymer dielectric (that I conducted with an exact solution, using Mathematica) shows induction heating of both ends.
A number of people have posted their own graphical output of Meep fields. I showed my own analysis of such Meep files, using Mathematica for post-processing the data, in previous threads, and gave my viewpoint on how such data should be analyzed and viewed.
Rather than engage in unproductive arguments, with subjective views about what fields are best to analyze and how best to view them to understand what is going on, let's be practical (*):
Here is a practical suggestion on Meep runs that Meep users can conduct
Is your Meep model a realistic model of reality?
Can you use Meep's graphical output to interpret what is going on?
Let's verify it and then use it to make a prediction
1) Verify (using Meep) the thermal camera measurements of NASA for their geometry, giving TM212 (assuming that the thermal profile is due to induction heating). Take a look at NASA's report on how the COMSOL analysis of the magnetic field looks like. Compare that with Meep.
2) Run Shell's geometry to predict what the thermal camera should measure when viewing her experiment. (assuming that the thermal profile is due to induction heating)
For example: does your Meep model predict mode TE013 ? Then show us what the thermal profile should look like, according to the Meep analysis (assuming that the thermal profile is due to induction heating)
_____
(*) With my own R&D staff, the first thing that I would ask people engaged in numerical modeling is to show verification of their analysis vs. simple cases having exact solutions, and then vs. more complicated experimental data.
One step further analyzing the whole pre-run test and the hardware in it. Plus, I love throwing something else into the evaluation pot to think about.
At the start of the test I was running low power and would not expect too much heat for the few runs I did. At the end I did a high power run, I lost the antenna(s) in the attached waveguide, then the Magnetron>coax waveguide. I shut it down.
The waveguides into the frustum are located vertically into the large end 180 from each other. The antennas were 1/4 WL simple copper wire located in the waveguides.
For the antenna to catastrophically fail at higher power it meant the VSWR was getting higher in the waveguide itself. That caused excess heat to form in the frustum waveguide cavities and that heat showed up on the bottom of the frustum being warm.
I honestly believe I was was running a TE013, from meep, from TT's spreadsheet and even my own calculations.
Although the only way for sure to tell is thermally by a camera. The next series I'll have my cameras in and will be videoing the Thermal camera screen, the laser scale, the digital scales and recording the video in the laptop screen. We then will be able to define the mode, the accompanying thermal signatures and beam deflections.
The antenna decaying into a mismatched RF matchstick makes the current evaluation of why the bottom area of the frustum was warm along with the heated waveguide from the matchstick antenna and using that thermal signature just by me handling it and then trying to define what mode I was running somewhat mute.
It will be best to wait until the first runs with full data attached.
Shell
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#710
by
X_RaY
on 24 Dec, 2015 20:10
-
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#711
by
ThereIWas3
on 24 Dec, 2015 20:36
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The waveguides into the frustum are located vertically into the large end 180 from each other. The antennas were 1/4 WL simple copper wire located in the waveguides.
When you say "vertically", is that with the frustrum lying on its side, so the feedlines come through the side walls at right angles to the wall? And how far from the large end? Or are they entering
through the large end? I which case, how far from the centerline?
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#712
by
SeeShells
on 24 Dec, 2015 20:52
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The waveguides into the frustum are located vertically into the large end 180 from each other. The antennas were 1/4 WL simple copper wire located in the waveguides.
When you say "vertically", is that with the frustrum lying on its side, so the feedlines come through the side walls at right angles to the wall? And how far from the large end? Or are they entering through the large end? I which case, how far from the centerline?
The RF is phased to match in the center of the frustum ~3wl.
What the waveguides see is the frustum as a "load dump" as the Q increases past and through it's peak to collapse, the frustum acts as a RF load dump or also called simply a load. By creating a slightly mismatched phasing in the waveguides I can force a dump at a defined time into the frustum. Then letting the shape of the frustum do what it does best and related to its shape. That's to create a pulsed push or force or call it what you want, in plain talk it allows the frustum shape to do what it does best in dumping it's high energy in a focused way.
Lasers do the same thing but in this case I can force it, I can tune it to happen just when it needs to.
Make sense?
Shell
added: In other words I'm controlling the decays of the high energy Q instead of single waveguides or antennas into the frustum which can cause rotational modes even through one cycle.
Or I can set the phasing between the two anywhere and also tune the cavity lengths. Makes for a lot of testing but I think the data we'll gain is worth it.
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#713
by
zen-in
on 24 Dec, 2015 22:29
-
...
Merry Christmas ALL!
Shell
There are several people here that have more knowledge in doing a Laser Interferometer testing than me. I'll need to ask, could I only mirror one half of one end to measure a pulse going down and back and just through to see if the directional travel times differ?
There are several ways of setting up an interferometer. You would need a visible light beamsplitter. The HP 10702A beamsplitters are ideal for this and can be found on eBay for < $200. Wikipedia has a good page on interferometry methods and the manual for HP's beamsplitter has a lot of tips. One problem I see is that interferometers are typically mounted on optical benches or some other rigid surface. Alignment is very touchy. If the detector, mirrors and beamsplitter plane are not aligned well the interference pattern at the detector will have too many fringes in it to be useful. White's setup had just one fringe, although his conclusions from that exercise are pure speculation.
https://en.wikipedia.org/wiki/Interferometryhttp://www.ebay.com/itm/HP-Agilent-10702A-Optical-Linear-Inferometer-Cube-with-10703A-Retroreflector-/181947496021?hash=item2a5cea7655:g:~qEAAOSwAKxWaeSgThere are a lot of very mundane things that will produce a big change in a well aligned interferometer's output: trucks outside, temperature changes, movement of the quartz rod, etc, etc. All you would see is interference fringes. Getting to the point where the fringes are not moving is very difficult and requires a very stable optical system. A change in length of one of the optical paths of 300 nM will make the fringe move. If the alignment is not spot on the detector will be looking at multiple fringes moving by.
When I was building FTIR spectrometers, based on a michelson interferometer, we would let them run overnight to get stability data. There was too much vibration during the day and it would take a few hours for everything to stabilize. The most stable interferometer I tested in 1979 had < 40 nM movement wrt the white light peak over 12 Hrs. It was donated to Peter Griffiths as a result of a bet the company founder made with Peter. It was flown on the Kuiper Airborne Observatory a year or two later.
http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471194042.html
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#714
by
SeeShells
on 24 Dec, 2015 23:14
-
...
Merry Christmas ALL!
Shell
There are several people here that have more knowledge in doing a Laser Interferometer testing than me. I'll need to ask, could I only mirror one half of one end to measure a pulse going down and back and just through to see if the directional travel times differ?
There are several ways of setting up an interferometer. You would need a visible light beamsplitter. The HP 10702A beamsplitters are ideal for this and can be found on eBay for < $200. Wikipedia has a good page on interferometry methods and the manual for HP's beamsplitter has a lot of tips. One problem I see is that interferometers are typically mounted on optical benches or some other rigid surface. Alignment is very touchy. If the detector, mirrors and beamsplitter plane are not aligned well the interference pattern at the detector will have too many fringes in it to be useful. White's setup had just one fringe, although his conclusions from that exercise are pure speculation.
https://en.wikipedia.org/wiki/Interferometry
http://www.ebay.com/itm/HP-Agilent-10702A-Optical-Linear-Inferometer-Cube-with-10703A-Retroreflector-/181947496021?hash=item2a5cea7655:g:~qEAAOSwAKxWaeSg
There are a lot of very mundane things that will produce a big change in a well aligned interferometer's output: trucks outside, temperature changes, movement of the quartz rod, etc, etc. All you would see is interference fringes. Getting to the point where the fringes are not moving is very difficult and requires a very stable optical system. A change in length of one of the optical paths of 300 nM will make the fringe move. If the alignment is not spot on the detector will be looking at multiple fringes moving by.
When I was building FTIR spectrometers, based on a michelson interferometer, we would let them run overnight to get stability data. There was too much vibration during the day and it would take a few hours for everything to stabilize. The most stable interferometer I tested in 1979 had < 40 nM movement wrt the white light peak over 12 Hrs. It was donated to Peter Griffiths as a result of a bet the company founder made with Peter. It was flown on the Kuiper Airborne Observatory a year or two later.
http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471194042.html
Good information! Thanks, I suspected as much.
I've a patent on a composite tunable fluid filled anti-vibration table called a VMP (Variable Mass Platform) that could be tuned to dampen vibrations in a given area. I'd have to build one again to get the damping like I'd need. I think I'll start planning to do another one.
I still have a nice piece of 1/2" thick 1/4-20 holed aluminum plate I could use for the top. The DUT could be enclosed and temperature controlled.
It's been over 10 years since I was in this and things change, I had to ask and you got me some great info.
Happy Holidays!
Shell
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#715
by
RFPlumber
on 24 Dec, 2015 23:20
-
Progress update on my pendulum-based test. While I cannot yet report on whether EmDrive is producing thrust or not (congrats to Shell!), I can at least report that a 50 Ohm dummy RF load is definitely not producing any . This is a good solid start; rumor has it that the only thing one needs to change now in order to obtain thrust is to use a frustum-shaped cavity instead of a dummy load… We shall see.
...
That is an impressive build! Could you post the CSVs you've generated so far, if you've saved them? It would be nice to have a little program read in a run and say "this data set shows non-zero thrust with probability X" before there is any actual frustum data to overfit to, and I'd like to take a stab at that.
Thank you. CSVs for 2 test runs attached. Ch1 is pendulum position (the value is in Volts, scale is 1V = 1000 um). Ch2 is High-Voltage on command (0 to 5 V change), Ch3 is RF on command (0 to 5 V change). Each run also includes 3 CSV files for Ch1 min, max and mid-point as-detected. Have fun!
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#716
by
SeeShells
on 24 Dec, 2015 23:44
-
Progress update on my pendulum-based test. While I cannot yet report on whether EmDrive is producing thrust or not (congrats to Shell!), I can at least report that a 50 Ohm dummy RF load is definitely not producing any . This is a good solid start; rumor has it that the only thing one needs to change now in order to obtain thrust is to use a frustum-shaped cavity instead of a dummy load… We shall see.
...
That is an impressive build! Could you post the CSVs you've generated so far, if you've saved them? It would be nice to have a little program read in a run and say "this data set shows non-zero thrust with probability X" before there is any actual frustum data to overfit to, and I'd like to take a stab at that.
Thank you. CSVs for 2 test runs attached. Ch1 is pendulum position (the value is in Volts, scale is 1V = 1000 um). Ch2 is High-Voltage on command (0 to 5 V change), Ch3 is RF on command (0 to 5 V change). Each run also includes 3 CSV files for Ch1 min, max and mid-point as-detected. Have fun!
Very nice work RFPlumber, very well done. Your name says it all.
Happy Holidays
Shell
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#717
by
ThereIWas3
on 25 Dec, 2015 02:55
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SeeShells, thank you for providing the detailed drawing. I was not aware that you were feeding it from the large end, and with short ante-chamber waveguides. I was able to quickly change my meep model to put the antennas in the centers of where your waveguides intersect the frustrum, and that got resonance patterns (all 18 of them) that look exactly like the patterns with the antennas at the small end, but with all the polarities reversed. Exchange blues with reds. I guess that is not surprising. The computed Q was a little less, 86,969 instead of 96,228.
Putting in the ante-chambers will take me a bit longer, but with your blueprint I can get right to it. For a while I thought that matching the slope of the frustrum wall with the waveguide would be a problem but then I remembered that, in meep, the order in which you specify objects matters, and later objects "cut through" earlier objects. So all I have to do is define the waveguide metal first as simple rectangular blocks, then the frustrum metal, then the frustrum air, then the waveguide air. The conical "frustrum air object" will cleanly cut off the end of the waveguide metal block protruding into the frustrum, and then the "waveguide air object" will punch a rectangular hole through the metal frustrum wall.
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#718
by
SeeShells
on 25 Dec, 2015 04:32
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SeeShells, thank you for providing the detailed drawing. I was not aware that you were feeding it from the large end, and with short ante-chamber waveguides. I was able to quickly change my meep model to put the antennas in the centers of where your waveguides intersect the frustrum, and that got resonance patterns (all 18 of them) that look exactly like the patterns with the antennas at the small end, but with all the polarities reversed. Exchange blues with reds. I guess that is not surprising. The computed Q was a little less, 86,969 instead of 96,228.
Putting in the ante-chambers will take me a bit longer, but with your blueprint I can get right to it. For a while I thought that matching the slope of the frustrum wall with the waveguide would be a problem but then I remembered that, in meep, the order in which you specify objects matters, and later objects "cut through" earlier objects. So all I have to do is define the waveguide metal first as simple rectangular blocks, then the frustrum metal, then the frustrum air, then the waveguide air. The conical "frustrum air object" will cleanly cut off the end of the waveguide metal block protruding into the frustrum, and then the "waveguide air object" will punch a rectangular hole through the metal frustrum wall.
Very welcome, I want to thank you for your time doing and learning meep and running this frustum.
When you get this simulation running well in meep, I'm going to ask
you and aero to do a run that will be the same dimensions, but the frustum will be arranged in a little different way. It will be my final attempt at generating the last TE mode. I had planned for three.
Long day and I'm bushed so have a nice Christmas.
Shell
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#719
by
Ryan900
on 25 Dec, 2015 04:44
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euh.. didn't I suggest that shape about 10 months ago and got spanked for that ? 
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1334659#msg1334659
But taking the opportunity here to discuss shapes and their consequences...
Would one of the readers here , that is skilled in programming, be able to create a program/routine that can calculate how many rays bounce in a forward direction (small end plate) and how many rays go backward towards the large end plate?
I might be wrong, but let's say for 10k bounces, I have a hunch that due to the shape of a frustum you'll get more forward bounces then backwards.
I get this idea from observing that the angle of indices of the frustum side walls, in the small plate direction, is more often steeper then in the other direction. But.. i could be wrong...hard to tell
Doing it 10000 times by hand doesn't seem like a good solution to verify this thesis... so.. any one care to help?
I assumed that the ray traveled in exactly a straight line and the ray bounced off at exactly its angle of impact. I modeled the system in 2D because I assumed the motion of the 3D ray has no impact on the number of up vs down rays in the system.
Source code is attached in Python. It is lightly commented.
Result: The number of up and down rays are pretty much the same. The values stay close to 50% up 50% down for every arrangement of A, B, and C I've tried. I have not created a program to optimize the two equations to find the largest disparity between up/down rays for a specified N but I have a strong feeling that the program will output a flat line located at the base of the parabola. The result doesn't really imply much but at least may help dispel some confusion regarding bouncing lines in a closed system.
Example:
y=x^2 and y=.5x (Forgot to record the cap line's height)
N=125 | Up=61 | Down=64
N=25,000 | Up=12,491 | Down=12,509
N=1,000,000 | Up=500,041 | Down=499,959
. This is a good solid start; rumor has it that the only thing one needs to change now in order to obtain thrust is to use a frustum-shaped cavity instead of a dummy load… We shall see.
