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#2260 by meberbs on 03 Feb, 2017 03:34
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But we do not even know if the emDrive produces a force, and we certainly do not know that it is due to artificial gravity if it works. Pretending to know something that we don't, simply will make things worse.QuoteNot within the dimensions of a 2.45 GHz frustum but. The point I am attempting to make (not clearly enough) is that it would make as much sense to describe emdrive thrust as 'artificial gravity' as it would to describe it as an anomalous force.
Disagree - There is to much in a name. Anomalous Force allows for ambiguity, it is ambiguous. Artificial gravity is very specific and rules out every other theory. At our current state of knowledge, Anomalous Force wins, hands down.
If it rules out every theory other than General Relativity then that is indeed my intent. Is our ambition limited to ambiguity... can we not even commit ourselves to what we know to be true.
Also, artificial gravity would imply that inside the frustum, you wouldn't feel an acceleration, when external viewers see the frustum accelerate. This is not generally true for the broader term "anomalous force." -
#2261 by aero on 03 Feb, 2017 04:03
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But we do not even know if the emDrive produces a force, and we certainly do not know that it is due to artificial gravity if it works. Pretending to know something that we don't, simply will make things worse.QuoteNot within the dimensions of a 2.45 GHz frustum but. The point I am attempting to make (not clearly enough) is that it would make as much sense to describe emdrive thrust as 'artificial gravity' as it would to describe it as an anomalous force.
Disagree - There is to much in a name. Anomalous Force allows for ambiguity, it is ambiguous. Artificial gravity is very specific and rules out every other theory. At our current state of knowledge, Anomalous Force wins, hands down.
If it rules out every theory other than General Relativity then that is indeed my intent. Is our ambition limited to ambiguity... can we not even commit ourselves to what we know to be true.
Also, artificial gravity would imply that inside the frustum, you wouldn't feel an acceleration, when external viewers see the frustum accelerate. This is not generally true for the broader term "anomalous force."
The time to nail down what "we" know comes after we actually know it, and that will take a few or many peer reviewed papers with only insufficient objections to the conclusion there-in. Have we seen even one such paper naming artificial gravity as the the cause of a well accepted EM drive"anomalous force?" -
#2262 by zen-in on 03 Feb, 2017 05:14
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Do hope Jamie does see good force generation via following the path least trodden. Dave also tried this with his wire mesh thruster and then built a conventional solid copper thruster.
Pushing the build envelope is good as long as it is understood that going "off piste" is not a guarantee of a good experience.
My build is solid copper end-plates, the only difference is the use of EMI copper shielding foil on the sidewalls. This is the same EMI copper foil used by RF antenna experts to build patch antennas and the like.
I don't think it's fair to compare it to Dave's wire mesh build as 1. that build was not exhaustively simulated and verified by others. 2. the antenna was not impedance matched to the cavity. 3. Dave was using a magnetron, not a solid-state RF source. 4. I'm using TE013 mode, a mode recommended by Shawyer.
I would assume that the Copper tape is used to trim the dimensions of a patch antenna. One way to test its suitability for sealing a cavity is to cut 1/2" section of braid from some coax and then bridge the gap with conductive Copper tape. If the return loss is the same as it was before the braid was cut the tape is good. You can try it with a 50 Ohm termination, a short and an open circuit at the other end. I have used conductive tape to fix a broken coax successfully (2.1 GHz for a TDRSS uplink), but I burned the glue off first and soldered it in place. I guess that doesn't count. -
#2263 by Monomorphic on 03 Feb, 2017 12:58
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I would assume that the Copper tape is used to trim the dimensions of a patch antenna. One way to test its suitability for sealing a cavity is to cut 1/2" section of braid from some coax and then bridge the gap with conductive Copper tape. If the return loss is the same as it was before the braid was cut the tape is good. You can try it with a 50 Ohm termination, a short and an open circuit at the other end. I have used conductive tape to fix a broken coax successfully (2.1 GHz for a TDRSS uplink), but I burned the glue off first and soldered it in place. I guess that doesn't count.
The eddy currents your VNA will generate are probably in the microamps. So the voltage drop across the conductive adhesive will be very small. But as input power increases, the eddy currents will increase and voltage drop across the conductive adhesive may increase, increasing per cycle losses very significantly and the Q may drop.
The specs for the EMI shielding copper foil say >85dB shielding for 2Ghz and I used two layers. As for the eddy currents, those are their strongest on the small end-plate, which is solid copper sheet. At the power I will be running tests, maximum currents of 45A/m (7.5W/cm2) are expected on the sidewalls.
I also checked the resistance of a cardboard backed test piece I made (cardboard can't be used because it crinkles when bent - best to use plastic sheet) vs a solid piece of copper sheet. Saw little to no difference. Whether that changes as power is ramped up is to be seen. And I'm always open to replacing the sidewalls with machined copper, budget permitting.
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#2264 by TheTraveller on 03 Feb, 2017 13:51
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Whether that changes as power is ramped up is to be seen. And I'm always open to replacing the sidewalls with machined copper, budget permitting.
Jamie,
Looks good. The -53dB rtn loss is very good. Better than any I achieved. Did you measure the Ql with that rnt loss?
What are the as built & measured dimensions to say 0.1mm & latest resonant freq?
Have tried all the major copper foil tape with conductive adhesive manufacturers for data on the high freq characterists of the adhesive. Nothing. My concern is at some input power level there may be arching between the edges of the copper foil and the foil layer under it as at 2.45GHz the adhesive conductivity may be very seriously reduced causing the foil strips to act as if each were insulated from each other.
Is there any way to make your test rig capable of free rotation? I believe it is time to move beyond static force tests and onto the real deal. Free acceleration of mass.
Achieve at least 1 rev, while continually accelerating all the time and the all the planets & moons of our solar system are ours to explore, including landing on Europa! -
#2265 by Monomorphic on 03 Feb, 2017 14:20
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Looks good. The -53dB rtn loss is very good. Better than any I achieved. Did you measure the Ql with that rnt loss?
What are the as built & measured dimensions to say 0.1mm & latest resonant freq?
Is there any way to make your test rig capable of free rotation? I believe it is time to move beyond static force tests and onto the real deal. Free acceleration of mass.
I didn't measure the Q at -53dB. I was working on the mechanism that raises and lowers the antenna so I didn't save the trace. I did take a screen cap of it though. If I can duplicate that I will measure Q.
Big_D=29.9cm
Height=24cm
Small_D=17.8cm
Resonant frequency: 2.4525Ghz
The test rig does freely rotate. The only obstacle is the laser displacement sensor (LDS), but that is on an arm that can be rotated out of the way. The LDS has a sensor range of ~1.5cm, if the arm moves more than that, I can move the LDS and let it rotate. To allow it to rotate a full 360 would require expanding the side walls of the draft enclosure so it is equal to the width - which is something I have planned for the future.
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#2266 by rfmwguy on 03 Feb, 2017 14:41
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I had technical difficulties at the time but finally figured out how to live stream on youtube. If you have a "brass set" you can live stream your first fire-up. I wanted to be the first to do this, but my wifi just couldn't handle the BW.Looks good. The -53dB rtn loss is very good. Better than any I achieved. Did you measure the Ql with that rnt loss?
What are the as built & measured dimensions to say 0.1mm & latest resonant freq?
Is there any way to make your test rig capable of free rotation? I believe it is time to move beyond static force tests and onto the real deal. Free acceleration of mass.
I didn't measure the Q at -53dB. I was working on the mechanism that raises and lowers the antenna so I didn't save the trace. I did take a screen cap of it though. If I can duplicate that I will measure Q.
Big_D=29.9cm
Height=24cm
Small_D=17.8cm
Resonant frequency: 2.4525Ghz
The test rig does freely rotate. The only obstacle is the laser displacement sensor (LDS), but that is on an arm that can be rotated out of the way. The LDS has a sensor range of ~1.5cm, if the arm moves more than that, I can move the LDS and let it rotate. To allow it to rotate a full 360 would require expanding the side walls of the draft enclosure so it is equal to the width - which is something I have planned for the future. -
#2267 by TheTraveller on 03 Feb, 2017 15:29
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Looks good. The -53dB rtn loss is very good. Better than any I achieved. Did you measure the Ql with that rnt loss?
What are the as built & measured dimensions to say 0.1mm & latest resonant freq?
Is there any way to make your test rig capable of free rotation? I believe it is time to move beyond static force tests and onto the real deal. Free acceleration of mass.
I didn't measure the Q at -53dB. I was working on the mechanism that raises and lowers the antenna so I didn't save the trace. I did take a screen cap of it though. If I can duplicate that I will measure Q.
Big_D=29.9cm
Height=24cm
Small_D=17.8cm
Resonant frequency: 2.4525Ghz
The test rig does freely rotate. The only obstacle is the laser displacement sensor (LDS), but that is on an arm that can be rotated out of the way. The LDS has a sensor range of ~1.5cm, if the arm moves more than that, I can move the LDS and let it rotate. To allow it to rotate a full 360 would require expanding the side walls of the draft enclosure so it is equal to the width - which is something I have planned for the future.
Jamie,
Thanks for the data. Will do a bit of work with it.
As the DIY community advances in the control of the Rf freq to obtain max force generating, that is way above the past several Snow Flake (30uN each) force, the next logical step is to built rotary test rigs, that have calculated and measured Moment of Inertia and Radius as from that the force that generates measured acceleration can be calculated.
You will find the latest spreadsheet has a calculator for estimating rotational force generation vs angular acceleration and time to a target RPM. Using that calculator makes it easier to deal with and calculate the force that achieves a measured rate of acceleration and RPM rate. -
#2268 by WhatAFeynDay on 03 Feb, 2017 16:49
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the next logical step is to built rotary test rigs
What's stopping you?Quote from: TheTravellerYou will find the latest spreadsheet has a calculator for estimating rotational force generation vs angular acceleration and time to a target RPM. Using that calculator makes it easier to deal with and calculate the force that achieves a measured rate of acceleration and RPM rate.
Why should anyone resort to such a complicated measurement system when a purpose-built torsional system and test stand is ready to go? All your spreadsheet system of calculating forces would serve to do is further obfuscate and muddy the results. ALthough I'm starting to see that's perhaps exactly what you want.
It's really coming off like Rossi trying to explain energy production with steam output. -
#2269 by Notsosureofit on 03 Feb, 2017 17:03
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This looks interesting from the Wikipedia refs...
arXiv:1502.08020v2
Exact correspondence between Renyi entropy flows and physical flows
Mohammad H. Ansari, Yuli V. Nazarov
(Submitted on 27 Feb 2015 (v1), last revised 29 May 2015 (this version, v2))
We present a universal relation between the flow of a Renyi entropy and the full counting statistics of energy transfers. We prove the exact relation for a flow to a system in thermal equilibrium that is weakly coupled to an arbitrary time-dependent and non-equilibrium system. The exact correspondence, given by this relation, provides a simple protocol to quantify the flows of Shannon and Renyi entropies from the measurements of energy transfer statistics.
Have to work through it...
The example (in the paper you point out) about THE SIMPLEST QUANTUM HEAT ENGINE is neat.
The example of A DRIVEN HARMONIC OSCILLATOR COUPLED TO HEAT BATHS shows the entropy flow only depends on the probe and harmonic oscillator temperatures and completely insensitive to external driving force
For a first look at the right bracket of eq. 22 with the cavity considered as the harmonic oscillator and the universe as the probe reservoir.
Starting with the effective "cavity radiation temperature at the frequency of interest" from the Rayleigh-Jeans formula (where hf << kT, about a factor of 200 for the cosmic background) we get:
T' = [P Q^2 / (V f^4)]*[c^3 / (16 pi^2 k)] (in degrees Kelvin)
Estimating P ~ 10^3(W), Q ~ 10^3, V ~ 10^-2(m^3), f ~ 2.5(GHz) gives T ~ 3.96*10^19 degrees Kelvin
to compare with the cosmic background at 2.725 K. (~160 GHz)
We can see that the contribution of the cavity radiation temperature to the right hand term of eq. 22 is negligible.
** Of course, this is hardly a complete picture as the entropy change of interest is that between the inertial and accelerated frame descriptions of the cavity.
* Note that P appears not as an external driving force, but as part of the calculation of the number of photons in the cavity.
One way to read this is that even a completely isolated oscillator will have some interaction (lifetime?) wrt the universe.
EDIT: ..when I learn how to add that is !
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#2270 by Monomorphic on 03 Feb, 2017 18:05
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More work on the electronics. Added the primary RF battery to the beam. Also added a USB hub as that was needed to run the spectrum analyser, signal generator, and multi-sensor simultaneously. I need two more very short usb cables and will look for those at Fry's tomorrow. Cable management is important!
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#2271 by Rodal on 03 Feb, 2017 18:23
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This looks interesting from the Wikipedia refs...
arXiv:1502.08020v2
Exact correspondence between Renyi entropy flows and physical flows
Mohammad H. Ansari, Yuli V. Nazarov
(Submitted on 27 Feb 2015 (v1), last revised 29 May 2015 (this version, v2))
We present a universal relation between the flow of a Renyi entropy and the full counting statistics of energy transfers. We prove the exact relation for a flow to a system in thermal equilibrium that is weakly coupled to an arbitrary time-dependent and non-equilibrium system. The exact correspondence, given by this relation, provides a simple protocol to quantify the flows of Shannon and Renyi entropies from the measurements of energy transfer statistics.
Have to work through it...
The example (in the paper you point out) about THE SIMPLEST QUANTUM HEAT ENGINE is neat.
The example of A DRIVEN HARMONIC OSCILLATOR COUPLED TO HEAT BATHS shows the entropy flow only depends on the probe and harmonic oscillator temperatures and completely insensitive to external driving force
For a first look at the right bracket of eq. 22 with the cavity considered as the harmonic oscillator and the universe as the probe reservoir.
Starting with the effective "cavity radiation temperature at the frequency of interest" from the Rayleigh-Jeans formula (where hf << kT, about a factor of 200 for the cosmic background) we get:
T' = [P Q^2 / (V f^4)]*[c^3 / (16 pi^2 k)] (in degrees Kelvin)
Estimating P ~ 10^3(W), Q ~ 10^3, V ~ 10^-2(m^3), f ~ 2.5(GHz) gives T ~ 2.6*10^21 degrees Kelvin
to compare with the cosmic background at 2.725 K. (~160 GHz)
We can see that the contribution of the cavity radiation temperature to the right hand term of eq. 22 is negligible.
** Of course, this is hardly a complete picture as the entropy change of interest is that between the inertial and accelerated frame descriptions of the cavity.
* Note that P appears not as an external driving force, but as part of the calculation of the number of photons in the cavity.
One way to read this is that even a completely isolated oscillator will have some interaction (lifetime?) wrt the universe.
T' = [P Q^2 / (V f^4)]*[c^3 / (16 pi^2 k)] =
with
P ~ 10^3(J/s),
Q ~ 10^3,
V ~ 10^(-2)(m^3),
f ~ 2.5*10^9 1/s
c= 299 792 458 m/s
k=1.38064852Ś10^(−23) J/⋅K
Units are correct
but I get a temperature two orders of magnitude smaller than your T ~ 2.6*10^21 degrees Kelvin, as I get:
T~3.16*10^(19) degrees Kelvin
hence 1/T = 3.16083*10^(-20)/K
Therefore the contribution of the EM Drive radiation temperature is completely negligible, by 19 orders of magnitude, compared to the cosmic background
1/ 2.725 K = 0.366972/K
since omegao is a common factor:
EM Drive contribution <<< cosmic background
3.16083*10^(-20)/K <<< 0.366972/K -
#2272 by TheTraveller on 03 Feb, 2017 18:52
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the next logical step is to built rotary test rigs
What's stopping you?Quote from: TheTravellerYou will find the latest spreadsheet has a calculator for estimating rotational force generation vs angular acceleration and time to a target RPM. Using that calculator makes it easier to deal with and calculate the force that achieves a measured rate of acceleration and RPM rate.
Why should anyone resort to such a complicated measurement system when a purpose-built torsional system and test stand is ready to go? All your spreadsheet system of calculating forces would serve to do is further obfuscate and muddy the results. ALthough I'm starting to see that's perhaps exactly what you want.
It's really coming off like Rossi trying to explain energy production with steam output.
Surely you jest?
A accelerative test rig will beat a static test rig any day. Will be using an overhead video that records the increasing angular velocity vs time from the video frames. Simple then to calc the accelerative force that is generated from the velocity change.
As per my test rig, this has been posted before but it seems you missed it.
I'm currently working on the prototype automatic freq tracker that will also work from an acceleration sensor to tune for max acceleration once the initial tune for lowest reflected power has been achieved and acceleration has started.
You seem to be very tightly focused as the only posts you make are on this forum and only about my build.
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#2273 by WhatAFeynDay on 03 Feb, 2017 19:07
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You seem to be very tightly focused as the only posts you make are on this forum and only about my build.
You're correct that I am tightly focused on your comments, but there's a reason for that. No other person who is currently participating in this forum has had their claims of successful thrust from a resonating propellantless frustrum included in the work product of research which my tax dollars helped to fund. I no longer cared about your claims until Paul March decided to include them in his presentations concerning experiments performed by Eagleworks.
I would rephrase your statement to more correctly characterize my posts. My posts to you are about your LACK of a build, in spite of your numerous statements to the contrary. What's very telling to me is that all you've ever needed to do to shut me up is post one single, solitary picture; something which takes other builders mere minutes to accomplish. -
#2274 by Rodal on 03 Feb, 2017 19:58
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I'm currently working on the prototype automatic freq tracker that will also work from an acceleration sensor to tune for max acceleration once the initial tune for lowest reflected power has been achieved and acceleration has started.
What accelerometer are you using? I have the PhidgetSpatial Precision 3/3/3 High Resolution multi-sensor already incorporated into the torsional pendulum and fully functional. I've been working on modifying some of Phidget's example code to interface the accelerometer with the signal generator.
http://www.phidgets.com/products.php?category=5&product_id=1044_0
I rapidly speed read through the brochures and this http://www.phidgets.com/docs/Accelerometer_Primer
and I could not find anywhere a statement saying what kind of sensor is this accelerometer based on.
Do you know what type of sensor it uses to measure acceleration?
https://en.wikipedia.org/wiki/Accelerometer#Types_of_accelerometer -
#2275 by Monomorphic on 03 Feb, 2017 20:15
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Do you know what type of sensor it uses to measure acceleration?
I can't seem to find a spec sheet with the accelerometer chip listed. It's a flat piece of silicone according to the description, if that helps. Here are the stats:
Acceleration Measurement Max ± 2 g
Acceleration Measurement Resolution 76.3 μg (748 um/s2)
Acceleration Bandwidth 497 Hz
Accelerometer White Noise σ 280 μg
Accelerometer Minimum Drift σ 40.6 μg
Accelerometer Optimal Averaging Period 398 s -
#2276 by Rodal on 03 Feb, 2017 20:25
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It would be nice to know what type of sensor it uses to measure acceleration to better understand its capabilities, but in any case, the specs tell you that it can measure from zero to at most 497 Hz in the best of cases, and watch out, that that is usually only valid as long as you operate far away from a natural frequency of your mechanical system so that damping forces are negligible.Do you know what type of sensor it uses to measure acceleration?
I can't seem to find a spec sheet with the accelerometer chip listed. It's a flat piece of silicone according to the description, if that helps. Here are the stats:
Acceleration Measurement Max ± 2 g
Acceleration Measurement Resolution 76.3 μg (748 um/s2)
Acceleration Bandwidth 497 Hz
Accelerometer White Noise σ 280 μg
Accelerometer Minimum Drift σ 40.6 μg
Accelerometer Optimal Averaging Period 398 s
If in doubt you can always check its measurement/calibrate it for your system -
#2277 by Monomorphic on 03 Feb, 2017 21:58
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Update on Paul K's hackaday baby emdrive:
New board ready for testing
The last board showed some power leak. The expected power could not be reached. It even degraded to 40mW - bad. Now I made a new board with better connectors and more careful routing which is ready for testing in Dresden.
It is prepared for the highly sensitive scale and can deliver more than 200mW with 24GHz at 85°C (after cable- and connector lossed), so we should not get thermal issues this time. The ALU-Plate will be also fixed to the scale for better heat dissipation.The cavity is new (blogged about it before). It shows two clean resonance peaks at which we will test for thrust.
Sweeps will also be made in case there are some other phenomena which may occur beside the two resonance frequencies.
For an eventual integration into a satellite, the board can find and track the resonance peaks automatically.
IŽll make a 360° video of the test preparation in Dresden (if allowed).
https://hackaday.io/project/5596-emdrivesatellite/log/52756-new-board-ready-for-testing
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#2278 by TheTraveller on 03 Feb, 2017 23:13
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Update on Paul K's hackaday baby emdrive:
New board ready for testing
The last board showed some power leak. The expected power could not be reached. It even degraded to 40mW - bad. Now I made a new board with better connectors and more careful routing which is ready for testing in Dresden.
It is prepared for the highly sensitive scale and can deliver more than 200mW with 24GHz at 85°C (after cable- and connector lossed), so we should not get thermal issues this time. The ALU-Plate will be also fixed to the scale for better heat dissipation.The cavity is new (blogged about it before). It shows two clean resonance peaks at which we will test for thrust.
Sweeps will also be made in case there are some other phenomena which may occur beside the two resonance frequencies.
For an eventual integration into a satellite, the board can find and track the resonance peaks automatically.
IŽll make a 360° video of the test preparation in Dresden (if allowed).
https://hackaday.io/project/5596-emdrivesatellite/log/52756-new-board-ready-for-testing
Paul K,
Nice work. For sure auto freq tracking is the way to go. With the 2 ports, I assume the freq tracker is using feedback from a 2nd port or is it based on reflected power.
Best of luck with Dr Tajmar and the testing.
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#2279 by Rodal on 03 Feb, 2017 23:28
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Update on Paul K's hackaday baby emdrive:
Here I formally prove that the thrust force per input power (for all three EM-Drive theories) scales like the square root of any geometrical dimension, for constant resistivity and magnetic permeability of the interior wall of the cavity and for constant geometrical ratios, constant medium properties and for the same mode shape. To maximize the thrust per input power, according to all three theories the most efficient EM-Drive would be as large as possible, this being due to the fact that the quality of factor of resonance Q (all else being equal) scales like the square root of the geometrical dimensions. Small cavity EM-Drives (all else being equal) are predicted to have smaller quality of resonance Q and therefore smaller thrust force/input power.
New board ready for testing
The last board showed some power leak. The expected power could not be reached. It even degraded to 40mW - bad. Now I made a new board with better connectors and more careful routing which is ready for testing in Dresden.
It is prepared for the highly sensitive scale and can deliver more than 200mW with 24GHz at 85°C (after cable- and connector lossed), so we should not get thermal issues this time. The ALU-Plate will be also fixed to the scale for better heat dissipation.The cavity is new (blogged about it before). It shows two clean resonance peaks at which we will test for thrust.
Sweeps will also be made in case there are some other phenomena which may occur beside the two resonance frequencies.
For an eventual integration into a satellite, the board can find and track the resonance peaks automatically.
IŽll make a 360° video of the test preparation in Dresden (if allowed).
https://hackaday.io/project/5596-emdrivesatellite/log/52756-new-board-ready-for-testing
Paper with proof can be downloaded from here:
https://www.researchgate.net/project/Assessing-the-EM-Drive-claims
