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#2520 by oyzw on 01 Nov, 2017 02:29
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An update on Jakub and his EmDrive builder team in Poland.
Jamie, Roger and myself are now working with Jakub to ensure his test data is as rock solid as it can be as we know the reception it will receive.
He has done vertical testing and horizontal testing. Vertical testing exhibits strong thrust that gives a result in agreement with the SPR thrust equation. Horizontal testing shows very little thrust.
Further testing is being arranged.
For those wishing to run the resonance numbers, here are the, as manufactured, internal cavity dimensions plus a few images of the test setup and schematic, which is based on the system Jamie has developed and is using the same 30W Rf amp.
Additionally Jakub uses a wireless data link, as can be seen in the horizontal test setup image.
Can add the test rig seems to be very stable and capable of sub 10uN force resolution. It uses 2 ceramic bearings on the centre bar of the balance beam.
Comments most welcome.
Hello. How much vertical thrust has been achieved? -
#2521 by RotoSequence on 01 Nov, 2017 04:48
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It's a little strange how people working on these experiments are following the same patterns of behavior. Initial efforts are clearly visible, they get to the domain of being ready to actually test something... ...and then they quietly fade away. Every single builder has stopped reporting in after measuring an ambiguous signal - if they don't cease before reporting any test data at all. This has happened far too many times for the past few years now. What's going on, guys?
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#2522 by Peter Lauwer on 01 Nov, 2017 11:14
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It's a little strange how people working on these experiments are following the same patterns of behavior. Initial efforts are clearly visible, they get to the domain of being ready to actually test something... ...and then they quietly fade away. Every single builder has stopped reporting in after measuring an ambiguous signal - if they don't cease before reporting any test data at all. This has happened far too many times for the past few years now. What's going on, guys?
Indeed, that 'they quietly fade away' is not a good sign. I would say it is because making the microwave system work is difficult enough, but setting up a good experiment to measure the forces reliably and doing clever measurements and report about them in a clear way, is even harder.
I probably fall into the category 'if they don't cease before reporting any test data at all'. I 'only have to put the parts in the attached picture together on the torsion balance'. It takes a lot of measurements to know the system well, though. Still problems with measuring the delivered power to the resonant cavity in a reliable way, and a dozen other questions to answer before it is useful to put it on the torsion balance. If only I had a few weeks to work full-time on it...
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#2523 by Peter Lauwer on 01 Nov, 2017 11:26
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I guess this quote from Collins and Pinch also applies to the EmDrive work:
'Reporting an experimental result is itself not enough to give credibility to an unusual claim. If such a claim is to be taken sufficiently seriously for other scientists even to try to refute it then it must be presented very clearly and with great ingenuity.'
H. Collins & T. Pinch, The Golem, Cambridge Univ. Press; 2 ed. (March 30, 2012).
[in pdf: http://cstpr.colorado.edu/students/envs_5110/collins_the_golem.pdf] -
#2524 by Monomorphic on 01 Nov, 2017 12:31
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Indeed, that 'they quietly fade away' is not a good sign. I would say it is because making the microwave system work is difficult enough, but setting up a good experiment to measure the forces reliably and doing clever measurements and report about them in a clear way, is even harder.
I work on it until i'm frustrated and sick of it, then I usually take a break for a couple of weeks. Other pauses are that I don't have the time because of other projects or vacation.
I'm dealing with two issues right now before I can continue: more natural convection and an antenna self-resonating problem.
Adding the insulation to the draft enclosure greatly reduced the natural convection. But as the on-board electrical components begin to heat up, they cause natural convection of ~3uN after about 15 minutes. So most recently I've added a hefty heatsink to the on-board computer and moved it to the top of the torsional pendulum beam rather than attached to the side. I also want to add a better heatsink to the RF amplifier - perhaps even use the same phase change wax NASA is using. I also need to wrap all the aluminum below and to the sides of the pendulum arm with insulation, which I will probably do today.
In the image below I have the cavity removed so I can work on the antenna. Roger Shawyer thinks my antenna design, which the Polish group is also using, is self-resonating at a certain frequency rather than exciting the cavity. This makes a lot of sense as Jakub and I are both showing the same ~2.409Ghz -40dB return loss. This is highly unlikely since we have very different geometric dimensions. This was unlucky for me as the spherical end-plate frustum is designed to resonate at 2.405Ghz with mode TE013. As that may be too close to the resonate frequency of the antenna, it looks like I will need a different antenna. The antenna should still work in the flat end-plate frustum as that cavity was designed to resonate at 2.45Ghz. My simulations of Jakub's cavity show TE012 at 2.369Ghz, so he is going to try that next instead of 2.404Ghz - though it looks like the small end is a little below cut-off (second image below).
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#2525 by Peter Lauwer on 01 Nov, 2017 12:58
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Indeed, that 'they quietly fade away' is not a good sign. I would say it is because making the microwave system work is difficult enough, but setting up a good experiment to measure the forces reliably and doing clever measurements and report about them in a clear way, is even harder.
I work on it until i'm frustrated and sick of it, then I usually take a break for a couple of weeks. Other pauses are that I don't have the time because of other projects or vacation.
...
I didn't had you in mind when I wrote that, Jamie! I know it usually take a couple of weeks before one has something new to report.
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#2526 by SeeShells on 01 Nov, 2017 14:58
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I've had to take a break from working on the lab and drive because of health issues. I so wanted to finish my testing and reporting on it. I'm on the mend and will resume in the near future. I don't want chat about my health issues on this forum, it's not the place.
It has been very frustrating for me to step back for a while when so close.
My Very Best,
ShellIt's a little strange how people working on these experiments are following the same patterns of behavior. Initial efforts are clearly visible, they get to the domain of being ready to actually test something... ...and then they quietly fade away. Every single builder has stopped reporting in after measuring an ambiguous signal - if they don't cease before reporting any test data at all. This has happened far too many times for the past few years now. What's going on, guys?
Indeed, that 'they quietly fade away' is not a good sign. I would say it is because making the microwave system work is difficult enough, but setting up a good experiment to measure the forces reliably and doing clever measurements and report about them in a clear way, is even harder.
I probably fall into the category 'if they don't cease before reporting any test data at all'. I 'only have to put the parts in the attached picture together on the torsion balance'. It takes a lot of measurements to know the system well, though. Still problems with measuring the delivered power to the resonant cavity in a reliable way, and a dozen other questions to answer before it is useful to put it on the torsion balance. If only I had a few weeks to work full-time on it... -
#2527 by aero on 01 Nov, 2017 16:36
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Welcome back, Shell!
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#2528 by aero on 01 Nov, 2017 17:03
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Do we have any measured temperature data from the surface of an operating EM drive frustum? One with corresponding thrust estimates? I would like to see the actual temperature rise during operation if possible.
I know those thrust measurements are rare, and I'm not asking about the temperature of the enclosure, rather, I am asking about the temperature rise in the copper that can be attributed to RF energy loss from the frustum. A thermal video perhaps? Further, a complete map of the surface temperature from an operating frustum would be truly useful. I know that there is a rough data point in the peer-reviewed EW paper. Unfortunately, it doesn't show the end temperatures, and it is from after the conclusion of the run as I understand it. -
#2529 by SeeShells on 01 Nov, 2017 18:00
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Welcome back, Shell!
Bless your heart Aero... Thanks.
My Very Best,
Shell -
#2530 by ThinkerX on 02 Nov, 2017 01:22
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I've had to take a break from working on the lab and drive because of health issues. I so wanted to finish my testing and reporting on it. I'm on the mend and will resume in the near future. I don't want chat about my health issues on this forum, it's not the place.
It has been very frustrating for me to step back for a while when so close.
My Very Best,
ShellIt's a little strange how people working on these experiments are following the same patterns of behavior. Initial efforts are clearly visible, they get to the domain of being ready to actually test something... ...and then they quietly fade away. Every single builder has stopped reporting in after measuring an ambiguous signal - if they don't cease before reporting any test data at all. This has happened far too many times for the past few years now. What's going on, guys?
Indeed, that 'they quietly fade away' is not a good sign. I would say it is because making the microwave system work is difficult enough, but setting up a good experiment to measure the forces reliably and doing clever measurements and report about them in a clear way, is even harder.
I probably fall into the category 'if they don't cease before reporting any test data at all'. I 'only have to put the parts in the attached picture together on the torsion balance'. It takes a lot of measurements to know the system well, though. Still problems with measuring the delivered power to the resonant cavity in a reliable way, and a dozen other questions to answer before it is useful to put it on the torsion balance. If only I had a few weeks to work full-time on it...
Welcome back!
I hope your health improves soon.
Do you intend to report your results here or elsewhere? Perhaps have Doctor Rodal do a paper?
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#2531 by chongma on 02 Nov, 2017 06:48
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Do we have any measured temperature data from the surface of an operating EM drive frustum? One with corresponding thrust estimates? I would like to see the actual temperature rise during operation if possible.
Both rfmwguy and monomorphic took temperature readings from their frustums during operation. I am sure monomorphic will take some readings during his next tests if you have a good idea for how to use the data -
#2532 by ThatOtherGuy on 02 Nov, 2017 07:25
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I work on it until i'm frustrated and sick of it, then I usually take a break for a couple of weeks. Other pauses are that I don't have the time because of other projects or vacation.
Jamie, life always comes first and then, by the way, taking a break and "unplugging" ourselves is often useful to reorganize ideas and find solutions; in my experience, solutions come to mind when you aren't thinking at a problem 
Adding the insulation to the draft enclosure greatly reduced the natural convection. But as the on-board electrical components begin to heat up, they cause natural convection of ~3uN after about 15 minutes. So most recently I've added a hefty heatsink to the on-board computer and moved it to the top of the torsional pendulum beam rather than attached to the side. I also want to add a better heatsink to the RF amplifier - perhaps even use the same phase change wax NASA is using. I also need to wrap all the aluminum below and to the sides of the pendulum arm with insulation, which I will probably do today.
How long it takes before the rig gets back to normal temperature ? Also, did you consider adding "something" (just thinking loud) to the rig to help cooling down faster after each test run ? I mean fans of whatever to be used after the test run (so that they won't introduce noise) which would help bringing down the temperature at faster rate ?
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#2533 by ThatOtherGuy on 02 Nov, 2017 07:28
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Do we have any measured temperature data from the surface of an operating EM drive frustum? One with corresponding thrust estimates? I would like to see the actual temperature rise during operation if possible.
I know those thrust measurements are rare, and I'm not asking about the temperature of the enclosure, rather, I am asking about the temperature rise in the copper that can be attributed to RF energy loss from the frustum. A thermal video perhaps? Further, a complete map of the surface temperature from an operating frustum would be truly useful. I know that there is a rough data point in the peer-reviewed EW paper. Unfortunately, it doesn't show the end temperatures, and it is from after the conclusion of the run as I understand it.
If my brain serves me, Jamie (monomorphic) posted some pics of his rig taken using a thermal camera; I can't find them right now, but if you look at Jamie's posts you may find them easily, I think
[edit]
Ok, found the messages, but they weren't related to full runs but to "tap tests" with powered on devices, here we go
https://forum.nasaspaceflight.com/index.php?topic=41732.msg1651022#msg1651022
https://forum.nasaspaceflight.com/index.php?topic=41732.msg1652413#msg1652413
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#2534 by Monomorphic on 02 Nov, 2017 11:17
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If my brain serves me, Jamie (monomorphic) posted some pics of his rig taken using a thermal camera; I can't find them right now, but if you look at Jamie's posts you may find them easily, I think
[edit]
Ok, found the messages, but they weren't related to full runs but to "tap tests" with powered on devices, here we go
https://forum.nasaspaceflight.com/index.php?topic=41732.msg1651022#msg1651022
https://forum.nasaspaceflight.com/index.php?topic=41732.msg1652413#msg1652413
Those are old thermal images. These are more recent with the new equipment, but still shows the CPU mounted to the side, which was moved to the top.
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#2535 by Star-Drive on 02 Nov, 2017 13:02
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Do we have any measured temperature data from the surface of an operating EM drive frustum? One with corresponding thrust estimates? I would like to see the actual temperature rise during operation if possible.
I know those thrust measurements are rare, and I'm not asking about the temperature of the enclosure, rather, I am asking about the temperature rise in the copper that can be attributed to RF energy loss from the frustum. A thermal video perhaps? Further, a complete map of the surface temperature from an operating frustum would be truly useful. I know that there is a rough data point in the peer-reviewed EW paper. Unfortunately, it doesn't show the end temperatures, and it is from after the conclusion of the run as I understand it.
Aero:
I published experimental thermal temp rise data for the Eagleworks TM212 frustum in this forum back in the spring of 2015. See attached samples from same. Is that the kind of data you are looking for or something else?
Best, Paul M.
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#2536 by SeeShells on 02 Nov, 2017 13:22
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Thanks.I've had to take a break from working on the lab and drive because of health issues. I so wanted to finish my testing and reporting on it. I'm on the mend and will resume in the near future. I don't want chat about my health issues on this forum, it's not the place.
It has been very frustrating for me to step back for a while when so close.
My Very Best,
ShellIt's a little strange how people working on these experiments are following the same patterns of behavior. Initial efforts are clearly visible, they get to the domain of being ready to actually test something... ...and then they quietly fade away. Every single builder has stopped reporting in after measuring an ambiguous signal - if they don't cease before reporting any test data at all. This has happened far too many times for the past few years now. What's going on, guys?
Indeed, that 'they quietly fade away' is not a good sign. I would say it is because making the microwave system work is difficult enough, but setting up a good experiment to measure the forces reliably and doing clever measurements and report about them in a clear way, is even harder.
I probably fall into the category 'if they don't cease before reporting any test data at all'. I 'only have to put the parts in the attached picture together on the torsion balance'. It takes a lot of measurements to know the system well, though. Still problems with measuring the delivered power to the resonant cavity in a reliable way, and a dozen other questions to answer before it is useful to put it on the torsion balance. If only I had a few weeks to work full-time on it...
Welcome back!
I hope your health improves soon.
Do you intend to report your results here or elsewhere? Perhaps have Doctor Rodal do a paper?
I'll do my paper and report here, as I've always intended. As far as Dr. Rodal, I can't speak for him.
My Very Best,
Shell -
#2537 by ThatOtherGuy on 02 Nov, 2017 13:49
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If my brain serves me, Jamie (monomorphic) posted some pics of his rig taken using a thermal camera; I can't find them right now, but if you look at Jamie's posts you may find them easily, I think
[edit]
Ok, found the messages, but they weren't related to full runs but to "tap tests" with powered on devices, here we go
https://forum.nasaspaceflight.com/index.php?topic=41732.msg1651022#msg1651022
https://forum.nasaspaceflight.com/index.php?topic=41732.msg1652413#msg1652413
Those are old thermal images. These are more recent with the new equipment, but still shows the CPU mounted to the side, which was moved to the top.
I suppose the pics are referred to an "unpowered" (cavity) test, since neither the cavity nor the dummy load show heat signatures
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#2538 by aero on 02 Nov, 2017 20:57
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Do we have any measured temperature data from the surface of an operating EM drive frustum? One with corresponding thrust estimates? I would like to see the actual temperature rise during operation if possible.
I know those thrust measurements are rare, and I'm not asking about the temperature of the enclosure, rather, I am asking about the temperature rise in the copper that can be attributed to RF energy loss from the frustum. A thermal video perhaps? Further, a complete map of the surface temperature from an operating frustum would be truly useful. I know that there is a rough data point in the peer-reviewed EW paper. Unfortunately, it doesn't show the end temperatures, and it is from after the conclusion of the run as I understand it.
Aero:
I published experimental thermal temp rise data for the Eagleworks TM212 frustum in this forum back in the spring of 2015. See attached samples from same. Is that the kind of data you are looking for or something else?
Best, Paul M.
Yes, Thanks, Paul.
It is likely not enough for detailed calculations. (I forgot to ask about the quality factor, was it on the order of 7000 for these runs?) That's OK because I'm not sure how to run the calculations anyway. But it is enough to illustrate the thought and question that I want to ask about.
The thing is, the frustum is warmer at the big end than the small end so RF energy is being dissipated preferentially at the big end. Inside the frustum, doesn't that mean that the reflection coefficient is lower at the big end than the small end? If I'm reading the images right, the big end temperature rise is 6.6 K while the small end temperature is effectively unchanged. I will assume from this that the reflection coefficient at the small end is near enough to one as to make no difference while at the large end something on the order of 100 watts is being dissipated.
Now, I know that there are many ways to cause the reflection coefficient to differ end to end, one way is to use different end materials for example. Another way is to highly buff one end only. But that is not the case with this data. It seems to me from the temperature data, that another way to make the reflection coefficient differ is to operate one end of the frustum near the cut-off frequency.
The reflection coefficient is a wave phenomenon. Proceeding with the thought and using Q = energy stored/energy lost per second gives Q = power stored/power lost, so power stored = Q * power lost. With Q = 7000 and drive power (power lost) = 100W, power stored = a big number. 0.7 MW. If the reflection coefficient at the small end = 1, then the reflection coefficient at the big end seems to equal (power stored - power lost)/power stored which is (1 - 1/Q), or in this case 0.99986.
Taking a step further out on the limb, using radiation pressure, P = Ef/c (Ef is radiation intensity) and for a perfectly reflected wave, P = 2*Ef/c and introducing the reflection coefficient, Γ, calculate the internal pressures on the ends of the frustum as:
Pressure Force, P = 2 *Γ *Ef/c . I have arbitrarily introduced the reflection coefficient as it seems right to me.
But I must take another step. Ef is defined as radiation intensity, in units of N/m^2 and I have E on the ends of the frustum. I'm guessing that the frustum end diameters are: inside big dia. = 0.25552668 ; inside small dia. = 0.15875 from my meep control file for the Brady cavity. Those numbers give A_be = 0.0513 and A_se = 0.0198 m^2. This gives
big end intensity, Ef_be = 1.37E+7 and
small end intensity, Ef_se = 3.54 E+7
Factoring these parameters into the pressure force equation and using differential pressure, delta P = P_se - P_be gives
delta P = 2 * ( Ef_se - Γ * Ef_be)/c . This is now in units of N/m^2 though and I need total. Maybe the best shot is simply to use total stored energy and not factor areas into then back out of the equation and call it Thrust.
Thrust = 2 * 0.7E+6* (1 - Γ ) / c
This number calculates to 0.667 micro-N. That is different than 83.6 micro-Newtons from Paul's temperature image data.
Lots of problems here. It gives the wrong answer by 2 orders of magnitude. That could be due to miss treatment of the areas of the two ends, or perhaps the Q value is wrong, or maybe the experimental force number is not the right data point to use, or maybe the temperatures were measured too long after power-off allowing too much heat to be conducted away/lost from the ends which would give the wrong ratio of reflection coefficients. Or maybe there is nothing to it at all. Lots of models can easily fit one data point. Still, I would like some input from the forum.
I found some related stuff here - https://arxiv.org/pdf/0807.1310.pdf -
#2539 by Mulletron on 02 Nov, 2017 23:28
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Interesting discussion starting at around 19:11. It's about cone geodesics. A straight line on the surface of the cone looks curved to us but not to something on the cone. A good intuition builder I suppose if one wants to think about things this way.
