Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2165788 times)

Offline Mulletron

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I'm thinking an xU cubesat with a big battery. Spin stabilized even at 50 micro newtons we would see positive results within an hour, tracked from the ground.
I hoped to be experimental about this.
Experiment trumps theory every time.
With what we have, lets have an experiment in zero-g
http://cannae.com/2-uncategorised/48-cubesat
Challenge your preconceptions, or they will challenge you. - Velik

Offline SleeperService

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Someone have a word with Elon.... He must know a thing or two... The Cannae stuff seems like a scam...

Offline Mulletron

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Someone have a word with Elon.... He must know a thing or two... The Cannae stuff seems like a scam...

Why?
Challenge your preconceptions, or they will challenge you. - Velik

Offline SleeperService

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Put it this way.
We are trying to determine whether or not we can get thrust out of microwave energy.
Endless discussions...
NASA Eagleworks.
I agree!! But we need an experiment to prove these things.
In Zero-g we trust!


Offline Mulletron

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Given that thrust follows the dielectric and can be controlled at will; it is clear that this is no artifact.
« Last Edit: 02/15/2015 01:12 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline SleeperService

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Cool. Elon should be all over this then...

Offline ThinkerX

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Ok...we are under direct mandate here from Chris to keep this thread geared towards 'space based applications.'

With that in mind perhaps its time to revamp the 'Mulletron Mission to Saturn' and combine that with the vacuum test results? 

Yes, the vacuum tests are not as great as hoped for, but they are a place to start from, and multiple improvements / ways of boosting this devices efficiency have been suggested.   So maybe a 'Mulletron Mission' using the unmodified vacuum test info, and a second based on...'reasonable best guess' improvements?

Also, with all the images on the web, there must be one out there that captures the essence of the Mulletron craft.

Offline Cinder

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Cool. Elon should be all over this then...

Probably not while it's still this early in TRL.  There's not much to lose in waiting for what seem to be imminent new empirical data.
The pork must flow.

Offline Notsosureofit

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Given that thrust follows the dielectric and can be controlled at will; it is clear that this is no artifact.

Being that I just probably wasted the entire evening trying to find a way to incorporate the dielectric into the tapered cavity calculation on scribble sheets, you just stimulated the thought that one only needs a cylindrical cavity plus dielectric to get an asymmetric dispersion relation which should be relatively easy to calculate.  (he says while nodding off)

Offline SleeperService

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Elon should employ Rodal, Mullertron, NotSureOfIt et al to examine anomalous thrust.
To not do so would be bad business.

Offline RotoSequence

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Elon should employ Rodal, Mullertron, NotSureOfIt et al to examine anomalous thrust.
To not do so would be bad business.

Elon's already weighed in on the subject:

Quote from: Elon Musk
‏@elonmusk
If u saw @TheSimpsons and wonder why @SpaceX doesn't use an electric rocket to reach orbit, it is cuz that is impossible

« Last Edit: 02/15/2015 02:16 AM by RotoSequence »

Offline SleeperService

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And whatever you may call it.. The jury is out on if it is impossible...

Offline M_Puckett

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The fact that it has reverse too pretty much clinches it. That speaks volumes.




So you really can put the silly thing into reverse?  Don't tell Dodgers.

Offline Star-Drive

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Folks:

When we can replicate the Chinese 1.0 Newton/kWe demonstrated performance levels that they reported in their 2012 and 2013 tests reports, see attached example from same, perhaps that will be the time to go to the power brokers to see what deal can be had in developing this technology into what it could become. 

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.  IMO maximizing the time rate of change of the E&M energy spectra working in the resonant cavity, along with the optimization of the TBD process that converts this time varying energy density into a unidirectional force pointed in just one controllable direction will hand us the keys to the solar system and beyond. 

BTW, I have no doubt now that this quantum vacuum derived propulsion system will be able to meet and ultimately surpass my conjectured WarpStar-I concept vehicle performance that I wrote about in my STAIF-2007 paper based on Woodward's Mach Lorentz Thrusters (MLT) of the day.  A vehicle that could go from the surface of the Earth to the surface of the Moon with a crew of two and six passengers with luggage in under four hours and then return to the surface of the Earth in another 4 hours with the same payload using just one load of H2/O2 fuel cell derived electrical power assuming 500-to-1,000 N/kWe efficiency MLTs or Q-Thrusters.  And yes, I know that's a mighty big leap from the 1.0uN/Watt we currently have demonstrated at the Eagleworks Lab, but if Dr. White's QVF/MHD conjecture is anywhere close to reality, it will be doable, at least in the long term.

Best, Paul M.

 
« Last Edit: 02/15/2015 04:18 AM by Star-Drive »
Star-Drive

Offline aero

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@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?
« Last Edit: 02/15/2015 06:07 AM by aero »
Retired, working interesting problems

Offline Mulletron

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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. 


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_keying

Phase shifting seems important.
https://www.viasat.com/files/assets/web/datasheets/EBEM_MD-1366_043_web.pdf
One of these driving your amp would be helpful. They go up to 2ghz.





« Last Edit: 02/15/2015 10:12 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Star One

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When the time comes do you think there will be any difficulty in getting papers on this published?

Offline Rodal

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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. 


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 Yang
the resonant frequency and quality factor of the independent microwave resonator system are 2.44895 GHz and 117495.08 respectively

Compare 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           21
TM2112  1932.6                 7320                       16.9                91.2                   Air             5
TM2112  1936.7               18100                       16.7                50.1                   Air             3
TM212    1937.115             6726                       50                   66                      Vacuum      1

NASA'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 mode



Instead, 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 17
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.

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.

« Last Edit: 02/15/2015 02:48 PM by Rodal »

Offline Rodal

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As discussed in these previous posts:

http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293800#msg1293800


http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293809#msg1293809

Resonance experiment on a microwave resonator system
Shi Feng Yang Juan Tang Ming-Jie Luo Li-Tao Wang Yu-Quan
(College of Astronautics, Northwestern Polytechnic University, Xi’an 710072, China)
Acta Phys. Sinica Vol. 63, No. 15 (2014)
(Attached below as the last attachment)


Quote
Abstract
A microwave resonator system is made, which has a tapered resonant cavity, a microwave source, and a transmission device. Because of the electromagnetic pressure gradient on the tapered resonant cavity, a net electromagnetic force along the axis of the cavity may be observed, which is needed to verify experimentally the use of the independent microwave resonator system. It is also needed to keep the independent microwave resonator system in resonating state, which is the important procedure to demonstrate the possibility of net electromagnetic force. Thus, a low-signal resonating experiment on the tapered resonant cavity combined with resonating parts is completed to accurately find out the resonant frequency of 2.45 GHz and to analyze the influence of temperature on the resonant state. Experimental result shows that the resonant frequency and quality factor of the independent microwave resonator system are 2.44895 GHz and 117495.08 respectively. When the temperature of the tapered resonant cavity wall rises, the resonant frequency will be decreased and the quality factor changed separately.

Notice that China's Prof. Juan Yang shows the force "F" directed towards the small base of the truncated cone. The same end (the small end) that gets heated up the most and gets heated much faster in the Chinese experiment: the small end..   

Notice that the increase of temperature vs. time (31 deg C = 56 deg F increase in 40 seconds) of this truncated cone is much higher than the increase in temperature reported by NASA (this is expected because the Chinese run their experiment with higher input power than NASA), because they run their experiment in Transverse Electric rather than Transverse Magnetic mode,  and because the Chinese measured the temperature at the correct location: on the inside of the EM Drive with thermocouples, while NASA reports the temperature measured by an IR camera on the outside surface of FR4 fiber-reinforced epoxy, which has very low thermal diffusivity and hence masks the true inner temperature.

The Chinese report that they run their experiment in Transverse Electric (TE) modes.

The Chinese paper also repeatedly states that

Quote
"the electromagnetic field intensity calculated in the vicinity of the axis is larger, therefore the center of the small end has a higher thermal energy, thus heating quickly,"

....

"we measured the cavity surface surface temperature at different locations as shown in Figure 11 with a thermocouple.   [Fig. 11, which I attach below shows the positions of the thermocouples noted as "1" to "6"] Temperature measurements at different points vs.  time, are shown in FIG 12 [Fig 12 which I attach below shows the temperature vs time at the 6 different thermocouple locations]. The temperature at the center of small end [thermocouple #1] first began rising rapidly."

Notice that the temperature of the small end (thermocouple #1) rises much more than the temperature of the big end (thermocouple #6).

Notice that the rise of the temperature vs time at the center of the small end is nonlinear (the upper temperature curve) while the temperature measured at the other locations show fairly linear behavior.


Clearly, there is a large temperature difference between the small end (thermocouple #1) and the large end (thermocouple #6)

Maximum temperature is reached at the center of the small end.

The heating profile is completely different from the one shown by Egan. 
« Last Edit: 02/15/2015 03:29 PM by Rodal »

Offline Notsosureofit

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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                        16.9
TM212  1932.6                   7320                  16.9                      91.2                        60.5
TM212  1936.7                 18100                  16.7                      50.1                       146.9
TM212  1937.115               6726                  50                         66                          163.3

How much of the table do we have for the Chinese ?

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