@Paul March,It is kind of important to my results if you could confirm that the Teflon Rubber gaskets are installed as illustrated in the attached model. Click on the image, it will expand so you can see detail - but of course it is mostly black so use the sliders to move around to find a corner. Right now, I am using a 12.5 mm coaxial dipole antenna at the inner face of the dielectric disk. I know you used a loop of some sort. How much do you think this difference matters considering that I am running a digital model?It is also important that I correctly model the width of the Teflon Rubber gasket filled gap. You wrote that the gasket was .064." Was that after installed, or did you compress it when you tightened down the retaining ring. If so, what would you estimate the actual distance is, between the copper cone and copper base plate, as installed? I know that sounds like a nonsense question, but my simulation shows thrust force is dramatically sensitive to just a small changes in the gap width. I'd like for my model to be as close as is possible to your Copper Kettle thruster. My final question (I hope) re. the gasket is, "Do you know what the dielectric constant is for the actual Teflon Rubber that you used?" (Did your supplier document it, perhaps.) I find values ranging from 2.1 to 2.5 and while force is not very sensitive to this value, it does have an effect.And while I'm at it, I read that the vacuum chamber is 30 inches by 36 inches, diameter by length. Is that inside or outside dimensions?
Quote from: Mulletron on 02/15/2015 07:48 amQuote from: Star-Drive on 02/15/2015 04:17 amFolks:In the meantime, lets ask why 60 watts of relatively harmonic free sine-wave RF power at the 1,937.118 MHz AKA the TM212 resonant frequency in this copper frustum cavity, can only generate a paltry ~60uN, whereas the Chinese claimed to have produce 160,000uN using just ~150 watts of 2,450 MHz RF signals from a magnetron? The magnetron RF signal source that is anything but a pure sine-wave generator, that instead has a modulated FM bandwidth of at least +/-30 MHz that is also concurrently amplitude modulated (AM) with thermal electron noise. Taking a critical look at this question, and knowing that the spectral shape of a magnetron looks like (see below) compared to a CW spike. It seems evident that a CW spike isn't the best waveform to use if you want to maximize thrust. Dollars to donuts says the Chinese are making full use of the available bandwidth of their resonant cavity by using that noisy magnetron. Magnetrons have lots of phase noise too. You can't easily use them on phased array radars because of that for example. ...I agree with Mulletron that the answer to Paul March's question is that it is much more effective to have a distributed power spectral density than the power concentrated at a single frequency spike. When the natural frequency changes in an unpredictable manner, it is much more effective to have a distributed power spectral density of excitation (it is the power spectral density ( http://en.wikipedia.org/wiki/Spectral_density#Power_spectral_density ) over the spectrum of changing natural frequencies that matters). The reason for this is that (as has been verified by Prof. Juan Yang in China by inserting thermocouples at different places in the EM Drive) the EM Drive is subjected to a very non-uniform temperature distribution, with the temperature increasing with time, that results in significant non-uniform thermal expansion of the EM Drive, and therefore the natural frequencies must shift with temperature (and therefore shift with time as the temperature changes with time) as the EM Drive expands non-uniformly with time. Therefore, having the power concentrated at a single frequency spike (NASA) is bound to be non-efficient as the resonant frequency changes with time, the EM Drive is going to move out of resonance even if one happens to excite it at the correct frequency to start with. The COMSOL calculations do not provide the natural frequency to enough precision within the extremely narrow bandwidth of a high Q resonance (the higher the Q, the narrower the resonant bandwidth) for NASA to know exactly the natural frequency for a given mode shape. More importantly, the COMSOL calculations do not provide the information needed for NASA to know how to shift the frequency with time, as the EM Drive thermally expands non-uniformly to stay at peak resonance.This is evident from the very low Q's reported by NASA (7K to 22K) compared with the Chinese, who report a Q=117K : Quote from: Juan Yangthe resonant frequency and quality factor of the independent microwave resonator system are 2.44895 GHz and 117495.08 respectivelyCompare this with NASA's reported Q:Mode Frequency (MHz) Quality Factor, Q Input Power (W) Mean Thrust (μN) Medium Efficiency(uN/W)TE012 1880.4 22000 2.6 55.4 Air 21TM2112 1932.6 7320 16.9 91.2 Air 5TM2112 1936.7 18100 16.7 50.1 Air 3TM212 1937.115 6726 50 66 Vacuum 1NASA's reported Q for the vacuum experiment is a meager Q = 6726, which is 17 times smaller than the Chinese reported Q = 117495.Also note that the most efficient mode reported by NASA Eagleworks is the Transverse Electric mode which gave a Mean Thrust of 55 uN with only 2.6 Watts.The Chinese also report that they used the Transverse Electric modeInstead, NASA Eagleworks has been running most of the experiments in the Brady report in the Transverse Magnetic mode, and the vacuum experiment also in the Transverse Magnetic mode, which NASA's own data (see above) shows to be the most inefficient mode.Why is NASA running the vacuum experiment in the most inefficient mode (Transverse Magnetic) rather than the most efficient mode (Transverse Electric) ? Because they report difficulties in tuning the EM Drive under the Transverse Electric mode.Quote from: Brady et.al page 17Prior to the TM211 evaluations, COMSOL® analysis indicated that the TE012 was an effective thrust generation mode for the tapered cavity thruster being evaluated, so this mode was explored early in the evaluation process. Figure 22 shows a test run at the TE012 mode with an operating frequency of 1880.4 MHz. The measured quality factor was ~22,000, with a COMSOL prediction of 21,817. The measured power applied to the test article was measured to be 2.6 watts, and the (net) measured thrust was 55.4 micronewtons. With an input power of 2.6 watts, correcting for the quality factor, the predicted thrust is 50 micronewtons. However, since the TE012 mode had numerous other RF modes in very close proximity, it was impractical to repeatedly operate the system in this mode, so the decision was made to evaluate the TM211 modes instead.Why does NASA have difficulties running the EM Drive in the more efficient mode (the Transverse Electric mode) ? Because the most efficient mode results in greater shifting of its natural frequency with time. Hence I agree with Mulletron that instead of having the power concentrated at a frequency, for a problem where we know that the natural frequency of the EM Drive changes with time in a difficult to calculate and predict (with enough precision) manner, the best solution is to have the power distributed over a wider spectrum of frequencies, as done by Prof. Juan Yang in China.
Quote from: Star-Drive on 02/15/2015 04:17 amFolks:In the meantime, lets ask why 60 watts of relatively harmonic free sine-wave RF power at the 1,937.118 MHz AKA the TM212 resonant frequency in this copper frustum cavity, can only generate a paltry ~60uN, whereas the Chinese claimed to have produce 160,000uN using just ~150 watts of 2,450 MHz RF signals from a magnetron? The magnetron RF signal source that is anything but a pure sine-wave generator, that instead has a modulated FM bandwidth of at least +/-30 MHz that is also concurrently amplitude modulated (AM) with thermal electron noise. Taking a critical look at this question, and knowing that the spectral shape of a magnetron looks like (see below) compared to a CW spike. It seems evident that a CW spike isn't the best waveform to use if you want to maximize thrust. Dollars to donuts says the Chinese are making full use of the available bandwidth of their resonant cavity by using that noisy magnetron. Magnetrons have lots of phase noise too. You can't easily use them on phased array radars because of that for example. ...
Folks:In the meantime, lets ask why 60 watts of relatively harmonic free sine-wave RF power at the 1,937.118 MHz AKA the TM212 resonant frequency in this copper frustum cavity, can only generate a paltry ~60uN, whereas the Chinese claimed to have produce 160,000uN using just ~150 watts of 2,450 MHz RF signals from a magnetron? The magnetron RF signal source that is anything but a pure sine-wave generator, that instead has a modulated FM bandwidth of at least +/-30 MHz that is also concurrently amplitude modulated (AM) with thermal electron noise.
the resonant frequency and quality factor of the independent microwave resonator system are 2.44895 GHz and 117495.08 respectively
Prior to the TM211 evaluations, COMSOL® analysis indicated that the TE012 was an effective thrust generation mode for the tapered cavity thruster being evaluated, so this mode was explored early in the evaluation process. Figure 22 shows a test run at the TE012 mode with an operating frequency of 1880.4 MHz. The measured quality factor was ~22,000, with a COMSOL prediction of 21,817. The measured power applied to the test article was measured to be 2.6 watts, and the (net) measured thrust was 55.4 micronewtons. With an input power of 2.6 watts, correcting for the quality factor, the predicted thrust is 50 micronewtons. However, since the TE012 mode had numerous other RF modes in very close proximity, it was impractical to repeatedly operate the system in this mode, so the decision was made to evaluate the TM211 modes instead.
Quote from: Star-Drive on 02/15/2015 04:17 amFolks:In the meantime, lets ask why 60 watts of relatively harmonic free sine-wave RF power at the 1,937.118 MHz AKA the TM212 resonant frequency in this copper frustum cavity, can only generate a paltry ~60uN, whereas the Chinese claimed to have produce 160,000uN using just ~150 watts of 2,450 MHz RF signals from a magnetron? The magnetron RF signal source that is anything but a pure sine-wave generator, that instead has a modulated FM bandwidth of at least +/-30 MHz that is also concurrently amplitude modulated (AM) with thermal electron noise. Taking a critical look at this question, and knowing that the spectral shape of a magnetron looks like (see below) compared to a CW spike. It seems evident that a CW spike isn't the best waveform to use if you want to maximize thrust. Dollars to donuts says the Chinese are making full use of the available bandwidth of their resonant cavity by using that noisy magnetron. Magnetrons have lots of phase noise too. You can't easily use them on phased array radars because of that for example. Now to put this idea to test, Q: What is the bandwidth of the resonant cavity and what is the 90 percent power bandwidth of the signal you are driving it with? What kind of sig gen are you using? Can it do FM? Can you do any advanced waveforms like a PSK waveform? Do you have a way to produce wideband noise or a spread spectrum carrier for your testing? Can you do any waveforms like at the bottom?Also during researching other possible theories which could explain Emdrive we found ample literature stating that molecules acquire a kinetic momentum during the switching of the magnetic field as a result of its interaction with the vacuum field. If correct, that may well be a very significant lead. So that raises the question, how does one increase the switching rate? What about phase shifting? http://en.wikipedia.org/wiki/Phase-shift_keyingPhase shifting seems important. https://www.viasat.com/files/assets/web/datasheets/EBEM_MD-1366_043_web.pdfOne of these driving your amp would be helpful. They go up to 2ghz.
...Dr. Rodal:You seem to ask a lot of "why" questions that could be better answered by getting yourself in the lab ...
... the main reason that we went with the lower-Q TM modes was because they consistently produced higher thrust levels for a given input power than the TE modes. ...
BTW, thanks much for the pointer to the 2014 Chinese report. Is there an English translation of same out in public yet? Also, in the 2013 Chinese report that had been translated into English, see attached, you will find that their large hundreds of milli-Newton thrust results were obtained with a loaded quality factor of just ~1,530 at 2.45 GHz, see figure 13 in their 2013 report. We think that is because that like any ac electric induction motor, this device has to load down its input energy/power source as it is generating thrusting work. Which brings up another point. That being all the calculated Q-Factors given in the Chinese papers, unless otherwise stated, is the very idealized unloaded Q-factors that implies that no energy is being extracted from the resonant cavity. We must keep that fact in mind as well...Best, Paul M.
BTW, thanks much for the pointer to the 2014 Chinese report. Is there an English translation of same out in public yet?
Quote from: aero on 02/15/2015 05:08 am@Paul March,It is kind of important to my results if you could confirm that ... snip ...
@Paul March,It is kind of important to my results if you could confirm that ... snip ...
Aero:"It is kind of important to my results if you could confirm that the Teflon Rubber gaskets are installed as illustrated in the attached model."I think what you are talking about is the initial pressure seal design for our aluminum frustum cavity that later went to a silicone O-ring and metal to metal compression shorting pad just inside the O-ring for both the large and small OD ends of the frustum. The Eagleworks copper frustum is not a gas sealed unit, so all it has for its large and small OD end-cap interfaces are copper metal to copper metal interface with #6-32 brass cap-screws, nuts and bronze internal star lock washers spaced an average of 1.0" apart on the frustum's 0.50" wide copper flanges. As to the average air gap between these copper flanges due to their out of plane irregularities, (These copper flanges are only 0.040" thick.), my guess is that it can be no larger than 0.002" midway between the cap-screws.
"Right now, I am using a 12.5 mm coaxial dipole antenna at the inner face of the dielectric disk. I know you used a loop of some sort. How much do you think this difference matters considering that I am running a digital model?"I've used various OD magnetic loops made from #20 AWG copper magnet wire soldered to SMA bulkhead connector that is mounted on the copper frustum's conical side wall, 15% of the of frustum Z-axis height from the large OD end of the frustum cavity, see attached picture. Currently we are using a 14.0mm OD loop antenna for our TM212 work at 1,937.118 MHz work.
"And while I'm at it, I read that the vacuum chamber is 30 inches by 36 inches, diameter by length. Is that inside or outside dimensions?"The Eagleworks vacuum chamber interior dimensions are as noted except the distance front aluminum door to the rear domed portion of the 304L stainless steel spun end cap is ~38.0", see attached Kurt J. Lesker drawing. However, Our vacuum door is hinged on the right side of the chamber as viewed from the door end.
FYI for no good reason, here what I get w/o dielectric Mode Frequency (MHz) Quality Factor, Q Input Power (W) Mean Thrust (μN) Calc TE012 1880.4 22000 2.6 55.4 16.9TM212 1932.6 7320 16.9 91.2 60.5TM212 1936.7 18100 16.7 50.1 146.9TM212 1937.115 6726 50 66 163.3How much of the table do we have for the Chinese ?
It looks from this drawing (see below) that the axial length of the Juan Yang truncated cone is significantly shorter than the small diameter, and therefore the Juan Yang truncated cone is significantly different from the one tested at NASA Eagleworks and Shawyer's Demo and Experimental truncated cones.
I wonder what kind of cash it costs to get some quality time with an additive/subtractive hybrid manufacturing 3D Printer/5 axis mills like the Lasertech series by DMG MORI, seen here fabricating a turbine housing:These kinds of printers are capable of working with a variety of materials, including aluminum, steel alloys, inconel, titanium, etc. I suspect hybrid manufacturing of an Inconel cavity or other alloy could be the easiest, least expensive way of acquiring high precision resonance cavities with relatively consistent operational characteristics, but I have no idea how much it costs to work with these sorts of machines.
...The question as to whether the EM Drive could be coupling to the Axion background came up on a different forum. I am dubious, and thought it would be useful to post why. A recent review of axions as CDM: http://www.pnas.org/.../2015/01/07/1308788112.full.pdf ...
Quote from: Star-Drive on 02/15/2015 03:36 pm... the main reason that we went with the lower-Q TM modes was because they consistently produced higher thrust levels for a given input power than the TE modes. ...The data reported by NASA Eagleworks contradicts that TM modes produce higher thrust levels than TE modes for a given input power:Mode Frequency (MHz) Quality Factor, Q Input Power (W) Mean Thrust (μN) Medium Efficiency(uN/W)TE012 1880.4 22000 2.6 55.4 Air 21TM2112 1932.6 7320 16.9 91.2 Air 5TM2112 1936.7 18100 16.7 50.1 Air 3TM212 1937.115 6726 50 66 Vacuum 1Apparently, the emphasis should be on the use of the word "consistently" either as that a) the reported Brady et.al. data for TE012 was inconsistent, in which case the Mean Thrust was not 55.4 uN as reported by Brady et.al. but apparently there is other unreported data that NASA has, giving significantly lower values of the thrust (and accordingly the reported Mean by Brady et.al. was not the true Mean of the TE012 experiments with the dielectric at NASA)orb) my interpretation of the Brady et.al.'s statement that NASA Eagleworks had trouble staying tuned at the natural frequency near 1880.4 MHz Quote from: Brady et.al page 17Prior to the TM211 evaluations, COMSOL® analysis indicated that the TE012 was an effective thrust generation mode for the tapered cavity thruster being evaluated, so this mode was explored early in the evaluation process. Figure 22 shows a test run at the TE012 mode with an operating frequency of 1880.4 MHz. The measured quality factor was ~22,000, with a COMSOL prediction of 21,817. The measured power applied to the test article was measured to be 2.6 watts, and the (net) measured thrust was 55.4 micronewtons. With an input power of 2.6 watts, correcting for the quality factor, the predicted thrust is 50 micronewtons. However, since the TE012 mode had numerous other RF modes in very close proximity, it was impractical to repeatedly operate the system in this mode, so the decision was made to evaluate the TM211 modes instead.
Just direct search1308788112.full.pdf