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#260 by aero on 16 Mar, 2016 03:21
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Dr. Rodal - I'm still wondering about ratio-ing Ag/CU * copper conductivity to obtain a valid Ag conductivity, but in the mean time, I have a new question for you, and all. meep is converging nicely now to positive Q values but they are still unreal. I just completed a run of the NSF-1701A model and meep calculated Q as 328,441. That's nice but it seems to me that it is about an order of magnitude to large.
Is it possible that you or DeltaMass misplaced a decimal point giving conductivity off by a factor of 10? I doubt that you did because in following the symbolic math you provided, I calculated the same number that you did. But we both started with the number for sigma, CU-sigmaSI 3.25E+8. Perhaps that should have been 10^+7 instead.
Does that seem reasonable? -
#261 by spupeng7 on 16 Mar, 2016 03:25
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http://www.bbc.co.uk/programmes/b0752f85
QuoteProject Greenglow - The Quest for Gravity Control
Horizon, 2015-2016
This is the story of an extraordinary scientific adventure - the attempt to control gravity. For centuries, the precise workings of gravity have confounded the greatest scientific minds - from Newton to Faraday and Einstein - and the idea of controlling gravity has been seen as little more than a fanciful dream. Yet in the mid 1990s, UK defence manufacturer BAE Systems began a ground-breaking project code-named 'Greenglow', which set about turning science fiction into reality. On the other side of the Atlantic, Nasa was simultaneously running its own Breakthrough Propulsion Physics Project. It was concerned with potential space applications of new physics, including concepts like 'faster-than-light travel' and 'warp drives'.
Looking into the past and projecting into the future, Horizon explores science's long-standing obsession with the idea of gravity control. It looks at recent breakthroughs in the search for loopholes in conventional physics and examines how the groundwork carried out by Project Greenglow has helped change our understanding of the universe. Gravity control may sound like science fiction, but the research that began with Project Greenglow is very much on-going, and the dream of flying cars and journeys to the stars no longer seems quite so distant.
The program segment will probably be geo blocked outside the UK. Do trust it will make the jump to open access YouTube.
THANKYOU PHIL
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#262 by spupeng7 on 16 Mar, 2016 03:32
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MHT1003NR3 arrived. It is a little smaller than I expected. This little 3-pin RF LDMOSFET transistor can output 250 watts @ 2.45Ghz with 32v DC!
Can't wait to see what difference a clean signal will make
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#263 by spupeng7 on 16 Mar, 2016 03:51
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Paul Kocyla in Aachen, Germany is beginning to test the 24 GHz emdrive on a rotary flotation pad. Unquantified force measurements, appears to be calibration tests:
Would appreciate somebody familiar with this testing program to clarify:
1) are the battery and the mini-EM-drive integrated together on the testing platform for the Kocyla test? DeltaMass and I had agreed that by far the best proposed test was TheTraveller's proposal to have a battery and the EM Drive on a rotary platform together (rather than having the power be fed from a stationary source to a moving EM Drive which has a big testing flaw: the center of energy-mass is outside the moving EM Drive, therefore measuring an acceleration in such a test is flawed since in space the source of power would need to be in the same spaceship as the EM Drive)
2) What is the present testing platform arrangement?
Dr Rodal,
very slowly I am working toward a similar experiment with the entire system under test being housed in a single closed container (not hermetically sealed).
The picture below shows the battery pack [light grey], power conditioning (dark grey), 60GHz resonator (brass) and frustum array (blue). Measuring just 15cm by 12cm x 7cm and weighing less than 600g. Hoping that some of these factors will compensate for lack of RF power capacity within frustum array.
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#264 by Star One on 16 Mar, 2016 08:51
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This is the Horizon episode on the BBC 23/03/16 featuring EM drive.
http://www.bbc.co.uk/programmes/b0752f85 -
#265 by TheTraveller on 16 Mar, 2016 10:01
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This is the Horizon episode on the BBC 23/03/16 featuring EM drive.
http://www.bbc.co.uk/programmes/b0752f85
Interesting statement:QuoteIt looks at recent breakthroughs in the search for loopholes in conventional physics
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#266 by RERT on 16 Mar, 2016 10:02
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This caught my eye on another forum where EM-drive was being discussed (off-topic):Quote
superconductors (even Type I) have a finite RF resistance and so don't produce infinite Q cavities. Ordinary conductors like Cu and Ag have their surface resistance continuously declining with temperature, extrapolated to 0 resistance at 0K. For *RF* purposes, just cold copper is approaching the performance of a Type 1 superconductor at the low temperatures that would be needed for Type I superconductivity. But, Cu and Ag have the advantage that they do not have a critical temperature where everything falls apart.
I don't know if this is true, but if it is it seems quite interesting.
R. -
#267 by TheTraveller on 16 Mar, 2016 10:15
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This caught my eye on another forum where EM-drive was being discussed (off-topic):
Quotesuperconductors (even Type I) have a finite RF resistance and so don't produce infinite Q cavities. Ordinary conductors like Cu and Ag have their surface resistance continuously declining with temperature, extrapolated to 0 resistance at 0K. For *RF* purposes, just cold copper is approaching the performance of a Type 1 superconductor at the low temperatures that would be needed for Type I superconductivity. But, Cu and Ag have the advantage that they do not have a critical temperature where everything falls apart.
I don't know if this is true, but if it is it seems quite interesting.
R.
When a copper coil is cooled by LN2, the resistance drops approx 8 times, which relates to a Q increase of approx 2.8x.
Don't believe the statement is correct. Also believe copper skin depth, at cryo temps & 2.45GHz excitation, flattens out. -
#268 by TheTraveller on 16 Mar, 2016 10:39
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Build UpDate,
Due to continuing issues with my prostate cancer, there has not been any work done on my test rig. Following discussions with Roger on the poor Q (some shared here), I have decided to stop working with the existing frustum build.
Working on a new build that will be machined & commercially polished to the very high standards Roger has set. This design will have spherical end plates and the side walls will be 6mm thick, with minimal 6mm thick end plates.
The end plates will be attached as Roger did in his Flight Thruster, so to allow differential pressure around the flange bolts to slightly alter the end plate to end plate alignment so to allow Q tuning with a torque wrench as happens in high Q accelerator cavities.
This will not be a cheap or quick build but as I have seen 8mNs of reaction, I have full confidence this build will deliver the min 20mN of reaction force (out of a theoretical 39mN) needed to take this to the independent measurement verification stage and then to release the data.
What I can say of this journey so far is a cheap & quick build MAY work somewhat if you are lucky. BUT to get consistent results that are close to those predicted, the build has to be to the quality levels Roger has shared.
Plus EmDrive DIYers really do need to read, fully understand & accept what is shared in the Test and Measurement paper:
http://www.emdrive.com/EmDriveForceMeasurement.pdf
Please study this photo. It is a gold mine. Especially the test setup. Note the spring. Then read the paper. As far as I know the prototype Flight Thruster was working and generating a reaction force. This is also the only known photo showing the Rf input connector and the mechanical arm on the left that allows the coupler to be adjusted inside the frustum. As Roger shared with me, every successful EmDrive build he knows of has some means to adjust the internal coupler to obtain optimal results.
I would add that both Dave & Shell are following the same pathway, ie:
Next Frustum Build Quality is a LOT higher than the 1st.
Newbie EmDrive builders please take note.
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#269 by rfmwguy on 16 Mar, 2016 11:20
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Stream of consciousness alert - in T6 posted about a paper talking about a supercharged sputtering magnetron in which particles jumped to a higher energy state.
Photon collisions creating mass require about 1 MeV of energy, far above a magnetrons power which I would guess is 1 KeV. (Edit - actually its around 12 microelectronvolts)
Have to find that paper to see the energy jump factor.
Still, if mass were be created, is it still a closed system and where does the mass go? Do the mass particles slam against the small end with more kinetic force or does CoM remain in effect as I would speculate. Have to study more when time permits.
https://en.m.wikipedia.org/wiki/Matter_creation -
#270 by Rodal on 16 Mar, 2016 11:24
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Build UpDate,
Alternatively, how about testing instead with your proposed setup having the battery and the EM-drive integrated together on the testing platform?
Due to continuing issues with my prostate cancer, there has not been any work done on my test rig. Following discussions with Roger on the poor Q (some shared here), I have decided to stop working with the existing frustum build.
Working on a new build that will be machined & commercially polished to the very high standards Roger has set. This design will have spherical end plates and the side walls will be 6mm thick, with minimal 6mm thick end plates.
The end plates will be attached as Roger did in his Flight Thruster, so to allow differential pressure around the flange bolts to slightly alter the end plate to end plate alignment so to allow Q tuning with a torque wrench as happens in high Q accelerator cavities.
This will not be a cheap or quick build but as I have seen 8mNs of reaction, I have full confidence this build will deliver the min 20mN of reaction force (out of a theoretical 39mN) needed to take this to the independent measurement verification stage and then to release the data.
...
Such a test would be by far the most convincing test to anyone. A number of people (including strong skeptics like DeltaMass) agreed that by far the best proposed test was your (TheTraveller's) proposal to have a battery and the EM Drive together (rather than having the power be fed from a stationary source to a moving EM Drive which has a big testing flaw: the center of energy-mass is outside the moving EM Drive, therefore measuring an acceleration in such a test is flawed since in space the source of power would need to be in the same spaceship as the EM Drive).
The flaw in all tests having the power source separate from a moving EM Drive is that the mass of a power source (for example the mass of a battery) must decrease as the electromagnetic field carries power away to the EM Drive. As the EM Drive acts like a resistor, it absorbs the power, and its mass must increase in the process. As the mass of the EM Drive increases with time, so the EM Drive must move in the opposite direction in order to conserve momentum. In this situation, the center of energy-mass never accelerates, it is just the EM Drive that must accelerate (a tiny amount) in order to conserve momentum. In a propulsion system where the power source and the EM Drive are integrated together its center of mass would not accelerate and would not be useful for propulsion in space. Thus, any test that has the power separate from a moving EM Drive is subject to this objection. Therefore the most convincing test is one where the EM Drive is powered by a battery, integrated in the same system.
(*)
Brito, Marini and Galian succeeded in nullifyng a Mach-Lorentz Thruster (MLT) by doing just that: integrating a battery together with the MLT together in a Cavendish type experiment. ("Null Findings on Electromagnetic Inertia Thruster Experiments using a Torsion Pendulum" 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference 2 - 5 August 2009 and Ricardo L. Marini and Eugenio S. Galian. "Torsion Pendulum Investigation of Electromagnetic Inertia Manipulation Thrusting", Journal of Propulsion and Power, Vol. 26, No. 6 (2010), pp. 1283-1290)
I hope that NASA is carrying on the proposed test with John Hopkins in a Cavendish type of pendulum (as proposed in their 2004 report "Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum, p. 21") with a battery supplying the power. Such a test would be the most convincing test to the scientific community.
___________
(*) When I have the time I will show this flaw analytically, with a post in the "Resonant Cavity Space-Propulsion: institutional experiments and theory " thread, showing the Poynting vectors and conservation of momentum
(**) This simple, conventional, increase in mass-energy of the EM Drive due to being powered by an RF feed is much simpler, and hence more plausible (using Occam's razor https://en.wikipedia.org/wiki/Occam%27s_razor
Among competing hypotheses, the one with the fewest assumptions should be selected.
) than the proposed "mass creation" being proposed elsewhere: https://forum.nasaspaceflight.com/index.php?topic=39772.msg1504407#msg1504407, or the also proposed "negative mass" explanation proposed elsewhere. -
#271 by TheTraveller on 16 Mar, 2016 11:42
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Alternatively, how about testing instead with your proposed setup having the battery and the EM-drive integrated together on the testing platform?...
As the next build is based on spherical end plates, the self contained rotary table testing will follow the quasi-static testing of this new generation frustum.
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#272 by Monomorphic on 16 Mar, 2016 12:29
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Photon collisions creating mass require about 1 MeV of energy, far above a magnetrons power which I would guess is 1 KeV.
At 2.45Ghz the quantum energy of a microwave photon is 10^-5 eV. I believe hard X-rays approach 1MeV. -
#273 by rfmwguy on 16 Mar, 2016 12:43
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Photon collisions creating mass require about 1 MeV of energy, far above a magnetrons power which I would guess is 1 KeV.
At 2.45Ghz the quantum energy of a microwave photon is 10^-5 eV. I believe hard X-rays approach 1MeV.
This sort of leaves this out as a possibility. If mass appears because of a photo collision, I would assume the resulting mass would travel in the direction of the photon with the highest energy. A large-diameter fired frustum would have photons colliding with the highest energy leaving the source (reflected photons having lower energy) meaning the newly found mass would travel away from the source(?) until it struck something...the small end or the sidewalls...that energy then being converted into kinetic energy/heat. Thus a loophole for CoE/M..."fresh" matter striking sidewalls or small diameter.
Oh well, the search continues...
(edit - Found the topic of the paper, still way too low of a potential energy..."In addition to increased number of ions, HiPIMS plasma generates ions with energies in the range of 50 eV to 100 eV (compared to only about 2 eV to 10 eV in conventional sputtering). ) - http://www.mantisdeposition.com/mantis/latest-technology/hipims.html -
#274 by Rodal on 16 Mar, 2016 13:28
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Dr. Rodal - I'm still wondering about ratio-ing Ag/CU * copper conductivity to obtain a valid Ag conductivity, but in the mean time, I have a new question for you, and all. meep is converging nicely now to positive Q values but they are still unreal. I just completed a run of the NSF-1701A model and meep calculated Q as 328,441. That's nice but it seems to me that it is about an order of magnitude to large.
Is it possible that you or DeltaMass misplaced a decimal point giving conductivity off by a factor of 10? I doubt that you did because in following the symbolic math you provided, I calculated the same number that you did. But we both started with the number for sigma, CU-sigmaSI 3.25E+8. Perhaps that should have been 10^+7 instead.
Does that seem reasonable?
As explained in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453093#msg1453093Quote from: Rodal
3.25E+8 was not the conductivity.
3.25E+8 is the number in SI units that corresponds to the expression used in Meep: it is not the conductivity, it is instead the imaginary part of the relative complex permittivity
Therefore 3.25E+8 corresponds instead to epsilon"/epsilon_o = 0.00288/epsilon_o
According to the exact solutions and to the COMSOL and FEKO runs, these copper cavities, for these dimensions ( ~0.3 m) can have theoretical Q's of 70,000 to 95,000.
So, a calculated Meep Q of 328,441 is about 3 to 4 times larger than what is supposed to be.
This factor of 3 to 4 may be due to the numerical method used in Meep to calculate Q's. If interested in studying this, I suggest to study the numerical convergence:
* Output Q's for the same problem, everything else being the same, with the mesh progressively refined such that the distance between nodes is cut by 1/2, (the purpose here being to study the behavior of the calculated Q vs space discretization):
Q for N number of nodes
Q for 2*N nodes
Q for 4*N nodes
Q for 8*N nodes
etc
==> Plot Q vs number of nodes
* Output Q's for the same problem with the same mesh, everything else being the same, with the deltaT of the central difference time discretization solution (the purpose here being to study the behavior of the calculated Q vs time discretization)
Q for deltaT = t
Q for deltaT = t/2
Q for deltaT = t/4
Q for deltaT = t/8
etc
==> Plot Q vs deltaT
* Output Q's for the same problem with the same mesh and same deltaT, everything else being the same, vs. the final termination time T (the purpose here being to study the behavior of the calculated Q vs the transient solution, as Q determined from too early a time maybe erroneous)
Q for T
Q for 2*T
Q for 4*T
Q for 8*T
etc
==> Plot Q vs final time T (fractions of a second)
_________________
Don't use the same discretization used in COMSOL Finite Element or FEKO Boundary Element methods: the finite difference scheme used in Meep (central difference method) requires a larger number of nodes to achieve similar convergence as COMSOL or FEKO or ANSYS. COMSOL or FEKO or ANSYS have higher rates of convergence because Finite Element methods and Boundary Element Methods are higher order and hence converge faster to a solution than the low order finite difference method used in Meep. For example, Finite Element Methods use polynomial interpolation functions between nodes and the Finite Element Method is based on a variational principle that ensures higher rate of convergence (for the same number of nodes) than the finite difference method.
The finite difference method implementation in Meep is optimized for solutions of optical frequency nonlinear problems, not for solution of microwave frequency linear problems.
Meep is efficient for optical frequency nonlinear problems. It may be inefficient (compared to FEKO or COMSOL) when applied to microwave frequency, linear problems that can be handled more optimally with methods like FEM or BEM.
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#275 by Rodal on 16 Mar, 2016 15:38
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For linear problems with well-behaved solutions, methods like Finite Element (FEM) and Boundary Element (BEM, also called "Method of Moments") are better than Finite Difference (FD) because the FEM uses polynomial interpolation between nodes and the BEM uses Green's functions. However the BEM entails fully populated matrices and the FEM entails matrices that are much more populated (with off-diagonal coupling terms) than the finite difference method. For nonlinear problems, finite difference is often more efficient because one must use high discretization anyway because the solution space may not be well-behaved: polynomial interpolation (specially high order polynomials) are not good for such problems. Ditto for Green's functions for nonlinear problems. Also for nonlinear problems one needs to use a Newton's method (or modified Newton's or Secant or BFGS etc.) that entail frequent computation of inverse of the solution matrix, therefore making the FEM or BEM much more inefficient than the finite difference method for such problems.
Just like it is good to have a collection of tools, because every problem is not best handled by a hammer, so it is with numerical methods. Meep is meant to be used for optical frequency problems, particularly able for nonlinear optical problems. -
#276 by Chrochne on 16 Mar, 2016 16:14
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This is the Horizon episode on the BBC 23/03/16 featuring EM drive.
http://www.bbc.co.uk/programmes/b0752f85
I must say EmDrive will probably hit news again.
Also the conversation here really started to get very interesting lately! Thanks in part of Monomorphic landing in this thread :-). There is also that paper from University of Helsinky. I think that it was Dr. Rodal that stated that there are many groups we do not know about that dig into the research of the EmDrive. I did not believe that. I am glad I was wrong.
It is also interesting to see the development of the Baby-Emdrive. I just do not fully understand that each report of the positive thrust is hit with the tsunami of pessimism.
Mod: Added the last sentence. -
#277 by aero on 16 Mar, 2016 16:22
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Well, Dr. Rodal, thank you for that extensive tutorial reply. While waiting, I went ahead and changed the number from 10^8 to 10^7 and as I suspected, it reduced the Q value calculated by meep by one order of magnitude. That is, meep calculated Q = 32,900 with all else being the same as had resulted in Q = 329,436 before. Resonant frequency was the same as before while energy in the fields was reduced. All that is as should be expected.
I do need to do a convergence study because I already know that, for this model, the calculated resonant frequency is higher with higher resolution. But that won't happen with this machine as I've noted previously. Not enough of either memory or cpu to double resolution more than once.
What meep does do and do well as is, is to calculate comparative values of Q for different cavities. This is a nice capability when the cavity differences are seemingly minor, such as antenna changes or minor shape modification to the same frustum. What I mean by that is, meep will calculate that this cavity modification increases or decreases the Q over it's previous value, and the percent change can be calculated even though the absolute magnitude of Q remains to be determined. -
#278 by Rodal on 16 Mar, 2016 16:35
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Well, Dr. Rodal, thank you for that extensive tutorial reply. While waiting, I went ahead and changed the number from 10^8 to 10^7 and as I suspected, it reduced the Q value calculated by meep by one order of magnitude. That is, meep calculated Q = 32,900 with all else being the same as had resulted in Q = 329,436 before. Resonant frequency was the same as before while energy in the fields was reduced. All that is as should be expected.
I do need to do a convergence study because I already know that, for this model, the calculated resonant frequency is higher with higher resolution. But that won't happen with this machine as I've noted previously. Not enough of either memory or cpu to double resolution more than once.
Yes, the fact that the Q is proportional to that number was expected. However, that does not ensure that the Q calculated according to a given scaling is correct.
Another idea to cope with your lack of computer time resources:
1) synchronize with Monomorphic, for Monomorphic to calculate the Q with FEKO for a given problem that is well specified: using a given geometry (thickness, diameters, length) and using pure copper as material input. Then run yourself with MEEP the same geometry: identical thickness, and other dimensions. Upon determining the Q from Meep, then proportionally scale the copper material input into Meep so that the Q agrees with the FEKO Q.
2) ask Monomorphic to run a completely different EM Drive geometry (different thickness, and dimensions as different as possible, for example run the mini-EM Drive from Tajmar or the Baby EM Drive from Aachen Germany). Then compare the FEKO Q with the Meep Q based on the scaling factor according to step #1 above. If they agree, you should feel somewhat comfortable about the calculated Q's
3) the comparisons above for steps 1 & 2 should be preferably made with a high order mode, for example TM212 because the Q is more sensitive to higher order modes. Using a low order mode like TE012 is not a good idea for this comparison because such low order modes are insensitive to the field variation in the cavity (such low order mode Q's are mostly dependent on the ratio of volume to surface area). -
#279 by Monomorphic on 16 Mar, 2016 16:54
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using a given geometry (thickness, diameters, length) and using pure copper as material input.
For my runs, I have been using pure copper at 0.1cm wall thickness. When running monopole sims, I'm a little uncertain what diameter to make the antenna. Shell showed me some images and took some measurements, and it looks like 0.5 to 0.7cm. The antenna is pinched at the end in magnetrons.
Both antenna design and placement are critical depending on the modes you want to excite.
I think i'm going to help illustrate this by running frequency sweeps (2 - 3Ghz) on the same frustum dimensions, but with a number of different antenna types and locations.
