### Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1876031 times)

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1920 on: 06/17/2015 01:18 PM »
...
Circular cavity.

Internal longitudinal axis.

No dielectric.

2.45 GHz exicitation.

For internal dimensions as follows:

End Plate internal big diameter= 11.01 inches
End Plate internal small diameter= 6.25 inches

My exact solution for the truncated cone gives, for mode shape TE013:

Length (inches)   Natural Frequency TE013 (GHz)   Maximum Relative Amplitude

9.00                  2.566                                         0.15
10.00                2.440                                         0.30
10.75                2.363                                         0.38
« Last Edit: 06/17/2015 01:23 PM by Rodal »

#### rfmwguy

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1921 on: 06/17/2015 01:29 PM »
...
Circular cavity.

Internal longitudinal axis.

No dielectric.

2.45 GHz exicitation.

For internal dimensions as follows:

End Plate internal big diameter= 11.01 inches
End Plate internal small diameter= 6.25 inches

My exact solution for the truncated cone gives, for mode shape TE013:

Length (inches)   Natural Frequency TE013 (GHz)   Maximum Relative Amplitude

9.00                  2.566                                         0.15
10.00                2.440                                         0.30
10.75                2.363                                         0.38

Thanks, so excitation freq of 2.45, what is your suggestion for length?

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1922 on: 06/17/2015 01:50 PM »
...
Circular cavity.

Internal longitudinal axis.

No dielectric.

2.45 GHz exicitation.

For internal dimensions as follows:

End Plate internal big diameter= 11.01 inches
End Plate internal small diameter= 6.25 inches

My exact solution for the truncated cone gives, for mode shape TE013:

Length (inches)   Natural Frequency TE013 (GHz)   Maximum Relative Amplitude

9.00                  2.566                                         0.15
10.00                2.440                                         0.30
10.75                2.363                                         0.38

Thanks, so excitation freq of 2.45, what is your suggestion for length?

My exact solution calculates that a length of 9.91 inches gives a natural frequency of 2.45 GHz for mode TE013

Length (inches)   Natural Frequency TE013 (GHz)   Maximum Relative Amplitude

9.00                  2.566                                         0.15
9.91                  2.450                                         0.21
10.00                2.440                                         0.30
10.75                2.363                                         0.38

But note:

1) The relative maximum amplitude for mode TE013 undergoes a nonlinear transition just about this length dimension on its way to more than double in intensity (with respect to its intensity at 9 inches).  The amplitude of TE013 considerably increases at lengths closer to 11 inches (and correspondingly lower natural frequency).

2) I am in the process of writing a paper about this interesting behavior, that only happens with cones (it is not present in cylindrical cavities).  It has to do with geometrical attenuation (and perhaps related to evanescent waves).  The relative amplitude of TE013 is very dependent on length.

3) If you can excite at lower frequencies it would be better for example to make the cone 10.75 inches long and excite it at a lower frequency around 2.36 GHz. If you can only excite at 2.45 GHz then make it around 9.91 inches.

4) Do not place too much confidence on the difference between these dimensions (between 9.91 inches and 10 inches, for example) as a lot depends on the accuracy of the internal dimensions of your final cone: circular runout, concentricity, longitudinal runout, and the participation of other modes nearby (which would need a spectrum analysis).  @Mulletron reported some time ago that he could move the natural frequency just by putting pressure on the cone with his hands.  A small deformation of the cone moves the natural frequency.
« Last Edit: 06/17/2015 01:57 PM by Rodal »

#### ElizabethGreene

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1923 on: 06/17/2015 02:04 PM »
In an resonator, light is trapped as standing waves of oscillating Electrical and Magnetic fields moving back and forth in the resonator.  Those fields have to move at the speed of light.  If a non-optical magnetic or electrical charge is introduced a short distance from an antinode....

1. Is there a force generated on the point of charge?
2. If the point is mechanically coupled to the resonator, does it push against the light to move the resonator?
3. If 2, understanding that light's electrical and magnetic fields propagate more slowly within materials as a function of the dielectric constant/index of refraction, could this explain why the dielectric blocks make a difference in some resonators?
4. If 2, could specific mechanical configurations induce an out-of-phase charge on the small plate causing force to be exerted in that direction?

<expletive insomnia>

Elizabeth

(Based on a completely undocumented, single, poorly controlled and grossly underinstrumented experiment, I no longer accept radiation pressure as an explanation for the Emdrive's thrust.  I'll write about it when I rerun it with more rigor.)

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1924 on: 06/17/2015 02:10 PM »
In an resonator, light is trapped as standing waves of oscillating Electrical and Magnetic fields moving back and forth in the resonator.  Those fields have to move at the speed of light.  If a non-optical magnetic or electrical charge is introduced a short distance from an antinode....

1. Is there a force generated on the point of charge?
2. If the point is mechanically coupled to the resonator, does it push against the light to move the resonator?
3. If 2, understanding that light's electrical and magnetic fields propagate more slowly within materials as a function of the dielectric constant/index of refraction, could this explain why the dielectric blocks make a difference in some resonators?
4. If 2, could specific mechanical configurations induce an out-of-phase charge on the small plate causing force to be exerted in that direction?

<expletive insomnia>

Elizabeth

(Based on a completely undocumented, single, poorly controlled and grossly underinstrumented experiment, I no longer accept radiation pressure as an explanation for the Emdrive's thrust.  I'll write about it when I rerun it with more rigor.)

Your mentioning of a point charge immediately catches my attention, because:

1) This is the section of Prof. Yang's paper where she discusses charge particles inside the EM Drive cavity:

Pages 4 and 5 of http://www.emdrive.com/NWPU2010translation.pdf

"Applying Method of Reference 2 to Effectively Calculating Performance of Microwave Radiation Thruster"
Yang Juan,Yang Le,Zhu Yu,Ma Nan
Journal of Northwestern Polytechnical University Vol 28 No 6 Dec 2010

Section 2 Electrodynamics theory of the microwave thrust without propellant

<<If the microwave electromagnetic field consists of charge particles, due to the electromagnetic force, the charge particles can travel within the electromagnetic field, so the charge particles can acquire energy and momentum from the electromagnetic field. This indicates that electromagnetic field have energy and momentum. Charge particle energy and momentum fulfil the following
relationship:
Dgp/dt=pE+JB dwp/dt=J.E (3)
Where J is current density of the moving particles, from the equation of Maxwell, the following is obtained:
V.(ExH)=-J.E-d/dt(1/2E.D+1/2H.B) (4)
where S=ExH represents the flux density vector of electromagnetic field or Poynting vector, wf=1/2E.D+1/2H.B represents the density of electromagnetic.
D/dt(wp+wf)+V.S=0
∫S.nds=-d/dt∫(wp+wf)dv=0 (5)
so
∫ wpdv+∫ wfdv=const (6)
Differentiate the Poynting vector and consider the Maxwell equation, the following equation can be derived:
D/dt(uoeo+gp)=-V
((1/2eoE2 +1/2 uoH2
)I-eoEE-uoHH) (7)
Because gp is the density of the charge particles, compare the term, uoeoS=uoeoExH , in the equation above, it represents the density of momentum of the electromagnetic field gf. The right hand side of the above equation can be define as the momentum flux density tensor of electromagnetic field
Ф=1/2(eoE2+uoH2
)I=eoEE+uoHH (8)
Introducing a new symbol T=- Ф, used for the tension tensor of electromagnetic field per unit area, this is first proposed by Maxwell, so it is also called Maxwell tension tensor. Integrating Equation 6 to:
D/dt∫ (gf+gp)dV=∫ n.TdS (9)
compare with the classical conservation of momentumdG/dt=F , the right hand side of Equation 9 represents the electromagnetic force produced by the electromagnetic tensor acting on the surface V, regardless whether charge particles are presented within the volume, the surface electromagnetic force can change the momentum within the volume V.>>

2) A NASA engineer at NASA Goddard (Joseph Knuble) has written about the possible influence of charged ions inside the microwave cavity.

These are his messages about Corona Discharge, etc.:

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1371195#msg1371195

http://forum.nasaspaceflight.com/index.php?topic=37438.msg1367778#msg1367778

http://forum.nasaspaceflight.com/index.php?topic=37438.msg1367727#msg1367727

http://forum.nasaspaceflight.com/index.php?topic=37438.msg1367683#msg1367683

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1367676#msg1367676

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1367663#msg1367663

3) The fact that microwave ovens can producing ionization (plasma) is evident to anyone that owns a home cooking microwave oven

« Last Edit: 06/17/2015 02:13 PM by Rodal »

#### rfmwguy

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1925 on: 06/17/2015 02:12 PM »
...
Circular cavity.

Internal longitudinal axis.

No dielectric.

2.45 GHz exicitation.

For internal dimensions as follows:

End Plate internal big diameter= 11.01 inches
End Plate internal small diameter= 6.25 inches

My exact solution for the truncated cone gives, for mode shape TE013:

Length (inches)   Natural Frequency TE013 (GHz)   Maximum Relative Amplitude

9.00                  2.566                                         0.15
10.00                2.440                                         0.30
10.75                2.363                                         0.38

Thanks, so excitation freq of 2.45, what is your suggestion for length?

My exact solution calculates that a length of 9.91 inches gives a natural frequency of 2.45 GHz for mode TE013

Length (inches)   Natural Frequency TE013 (GHz)   Maximum Relative Amplitude

9.00                  2.566                                         0.15
9.91                  2.450                                         0.21
10.00                2.440                                         0.30
10.75                2.363                                         0.38

But note:

1) The relative maximum amplitude for mode TE013 undergoes a nonlinear transition just about this length dimension on its way to more than double in intensity (with respect to its intensity at 9 inches).  The amplitude of TE013 stabilizes at a larger amplitude at lengths closer to 11 inches (and correspondingly lower natural frequency).

2) I am in the process of writing a paper about this interesting behavior, that only happens with cones (it is not present in cylindrical cavities).  It has to do with geometrical attenuation (and perhaps related to evanescent waves).

3) If you can excite at lower frequencies it would be better for example to make the cone 10.75 inches long and excite it at a lower frequency around 2.36 GHz. If you can only excite at 2.45 GHz then make it around 9.91 inches.

4) Do not place too much confidence on the difference between these dimensions as a lot depends on the accuracy of the internal dimensions of your final cone: circular runout, concentricity, longitudinal runout, and the participation of other modes nearby (which would need a spectrum analysis).

Thanks doc,

Spectrum analysis will not be a problem, as well as precise power measurement...am still friendly with my old company: http://bird-technologies.com

You and others are welcome to connect with me (real names only) on linkedin:

<edit correct url>

Note, in the last 7 years, I've been in semi-retirement mode and a high degree of multi-tasking (wife calls it adhd)
« Last Edit: 06/17/2015 02:23 PM by rfmwguy »

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1926 on: 06/17/2015 02:23 PM »
...
Thanks doc,

Spectrum analysis will not be a problem, as well as precise power measurement...am still friendly with my old company: http://bird-technologies.com

You and others are welcome to connect with me (real names only) on linkedin: https://www.linkedin.com/pub/a-david-distler/8/814/578

Note, in the last 7 years, I've been in semi-retirement mode and a high degree of multi-tasking (wife calls it adhd)

I was referring also to the issue that there are a lot of mode shapes bunched next to each other, and that it is not practical to have a cavity resonate such that only one mode gets excited, but in general many mode shapes are excited with different degrees of participation in the response.  To model the degree of participation of different modes one has to conduct a Spectrum Analysis of the response spectra (which to my knowledge nobody has yet reported for the EM Drive -- the NASA COMSOL FEA reported analyses are eigenvalue analysis instead of spectra response analyses-).

« Last Edit: 06/17/2015 02:41 PM by Rodal »

#### rfmwguy

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1927 on: 06/17/2015 02:35 PM »
...

I was referring also to the issue that there are a lot of mode shapes bunched next to each other, and that it is not practical to have a cavity resonate such that only one mode gets excited, but in general many mode shapes are excited with different degrees of participation in the response.  To model the degree of participation of different modes one has to conduct a Spectrum Analysis of the response spectra (which to my knowledge nobody has yet reported for the EM Drive -- the NASA COMSOL FEA reported analyses are eigenvalue analysis instead of spectra response analyses-

In my previous world, spectrum analysis was wide and narrow bandwidth FFT around ctr freq for spurious emmissions, mainly due to IMD distortion often caused by magnetic or dissimilar metals in the transmission line and radiator.

Perhaps we are speaking different languages...Spectra Response analysis is different, no?

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1928 on: 06/17/2015 02:40 PM »
...

I was referring also to the issue that there are a lot of mode shapes bunched next to each other, and that it is not practical to have a cavity resonate such that only one mode gets excited, but in general many mode shapes are excited with different degrees of participation in the response.  To model the degree of participation of different modes one has to conduct a Spectrum Analysis of the response spectra (which to my knowledge nobody has yet reported for the EM Drive -- the NASA COMSOL FEA reported analyses are eigenvalue analysis instead of spectra response analyses-

In my previous world, spectrum analysis was wide and narrow bandwidth FFT around ctr freq for spurious emmissions, mainly due to IMD distortion often caused by magnetic or dissimilar metals in the transmission line and radiator.

Perhaps we are speaking different languages...Spectra Response analysis is different, no?
Yes, you are referring to hardware spectral analysis and I was referring to modeling analysis of the spectral response using software to make a prediction of the actual mode participation of different modes
« Last Edit: 06/17/2015 02:40 PM by Rodal »

#### sghill

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1929 on: 06/17/2015 02:43 PM »
... now I understand that the stored current may be DC and the associated magnetic field, stored in the small end of the frustum and caused by the time-asymmetry of the evanescent wave's near-field induction effects. Along the walls of the frustum, the gauge potential has a divergence, offset by a change in the refractive index. This divergent field can escape and away we go!

What is the best way to measure (or model) this field that's escaping the frustum and correlate it to measured thrust?

And how would the "DC" EMDrive be setup so as not to use microwaves?
Bring the thunder Elon!

#### rfmwguy

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1930 on: 06/17/2015 02:49 PM »
...

I was referring also to the issue that there are a lot of mode shapes bunched next to each other, and that it is not practical to have a cavity resonate such that only one mode gets excited, but in general many mode shapes are excited with different degrees of participation in the response.  To model the degree of participation of different modes one has to conduct a Spectrum Analysis of the response spectra (which to my knowledge nobody has yet reported for the EM Drive -- the NASA COMSOL FEA reported analyses are eigenvalue analysis instead of spectra response analyses-
...
Perhaps we are speaking different languages...Spectra Response analysis is different, no?
Yes, you are referring to hardware spectral analysis and I was referring to modeling analysis of the spectral response using software to make a prediction of the actual mode participation of different modes

Got it. Best I can do is a thermal image, not sure if 8W will be enough to generate much heat however. I am considering a test I read about on this thread somewhere in which a "fog" seemed to have been attracted along magnetic lines of influence.

BTW like the IUPUI 50s pic.
« Last Edit: 06/17/2015 02:56 PM by rfmwguy »

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1931 on: 06/17/2015 03:08 PM »
....If you can only excite at 2.45 GHz then make it around 9.91 inches....

With a length of 251.72mm (9.91") you should get the following modes to resonate at 2.45GHz

1) TE013
2) TE114
3) TM014
4) TM113

Which one you will excite depends on antenna placement position, antenna design and orientation.

At least Dr Rodal and I agree the standard EW frustum

Frustum big diameter    m   0.2794000
Frustum small diameter   m   0.1588000
Frustum centre length   m   0.2286000
External Rf                   Hz   2,450,000,000

will not resonate at 2.45GHz.

Which does call Iulian's results into question. Just maybe his magnetron output frequency distribution was wide enough to get a weak resonance or maybe all we saw was the effect of rapidly heated microwaved moisture in the air.
« Last Edit: 06/17/2015 03:11 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

#### kml

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1932 on: 06/17/2015 03:11 PM »

So you decide. Go with the SPR calc methods or go chasing SnowFlakes.

Testing different design methods and models should be strongly encouraged.   We still don't know how this effect works.     We will only get a better understanding of this through a diversity of experiments that test different aspects and designs.    Attempting to scale up the existing design would be helpful too, but certainly not the only thing.

- My 10kg x 1mg scale is on it's way!

- I was able to cut the 4"x4" alumina plate to fit within the waveguide using a diamond blade on an 11k rpm angle grinder.    Alumina really does laugh at any tool without diamond in it.    The system's Q was still ~1600 after inserting the alumina but it did lower the resonant frequency by by 30MHz (without adjusting the z dimension).   I am going to test with the existing flat face on the alumina plate first, though that should have 25% reflectivity.   After those tests I will cut some grooves to attempt to reduce reflection.  I also have some larger alumina plates on the way that can be cut to completely fill the waveguide aperture.

- SrTiO3 powder has been ordered, though that will need to be compressed and sintered to be most effective.

- I ordered a 30W power amp kit from Down East Microwave which will triple my existing power level without adding too much weight.   I want to keep the entire apparatus including battery within the 10kg scale capacity.  It is currently at ~6kg not including the additional PA and battery.

- I'm going to do initial tests with the current Q ~ 1600, then attempt to increase Q for further tests.   The sample ports is pulling out 10% of the input power so reconfiguring that should be an easy way to increase Q.   Having that high take off does make it easy to tune with just a meter since I don't have a spectrum analyzer yet.

The Scale is scheduled to arrive Thursday so I should have some data by this weekend.
« Last Edit: 06/17/2015 03:20 PM by kml »

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1933 on: 06/17/2015 03:19 PM »
...

I was referring also to the issue that there are a lot of mode shapes bunched next to each other, and that it is not practical to have a cavity resonate such that only one mode gets excited, but in general many mode shapes are excited with different degrees of participation in the response.  To model the degree of participation of different modes one has to conduct a Spectrum Analysis of the response spectra (which to my knowledge nobody has yet reported for the EM Drive -- the NASA COMSOL FEA reported analyses are eigenvalue analysis instead of spectra response analyses-

In my previous world, spectrum analysis was wide and narrow bandwidth FFT around ctr freq for spurious emmissions, mainly due to IMD distortion often caused by magnetic or dissimilar metals in the transmission line and radiator.

Perhaps we are speaking different languages...Spectra Response analysis is different, no?
A magnetron, for example, emits photons at different frequencies, as well as producing modulation (frequency, amplitude and phase modulation).  This results in feeding a complex spectrum to the truncated cone.
The truncated cone response will contain different modes shapes with different participation.  (This is also a function of RF feed placement and choice of RF feed, of course).

I spent a short amount of time looking for images for electromagnetic spectral analysis: I could not readily find spectrum analyses (modelled with software) for a magnetron exciting a cavity: it looks that it is not usual for Electrical Engineer researchers to conduct such analysis (*), but it is very usual for example to model earthquakes acceleration, (for obvious reasons, as an earthquake contains a rich spectrum),or to model the response of a bridge,or to model the response of a rocket to a vibration spectrum, for example coming from a chemical propulsion rocket engine, here is earthquake spectrum response analysis;

To model the response of the EM Drive, a spectral analysis would also be needed.

_____
(*) It is noteworthy that the Finite Element method was developed at MIT and other places during and after WWII to model aircraft aeroelastic response and that it was only used by Electrical Engineers to solve Maxwell's equations decades later.  The Finite Difference method, though was used prior to WWII and continues to be used to this date (in MEEP for example) to solve Maxwell's equations.
« Last Edit: 06/17/2015 03:31 PM by Rodal »

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1934 on: 06/17/2015 03:35 PM »
....If you can only excite at 2.45 GHz then make it around 9.91 inches....

With a length of 251.72mm (9.91") you should get the following modes to resonate at 2.45GHz

1) TE013
2) TE114
3) TM014
4) TM113

Which one you will excite depends on antenna placement position, antenna design and orientation.

At least Dr Rodal and I agree the standard EW frustum

Frustum big diameter    m   0.2794000
Frustum small diameter   m   0.1588000
Frustum centre length   m   0.2286000
External Rf                   Hz   2,450,000,000

will not resonate at 2.45GHz.

Which does call Iulian's results into question. Just maybe his magnetron output frequency distribution was wide enough to get a weak resonance or maybe all we saw was the effect of rapidly heated microwaved moisture in the air.

Sorry, I don't agree with the word "will not resonate" in absolute terms.  You probably mean "will not resonate at the highest Q".  There is always a spectral response of resonance, which will contains peaks with different amplitude at different frequencies.

The natural frequencies at which maximum Q occurs changes with  temperature, as the EM Drive heats up and the EM Drive expands, for example.

In the case of the EM Drive, we have the separate issues of at what frequencies maximum Q occurs, and at what frequencies maximum acceleration response occurs (if the EM Drive "acceleration" is not an artifact) -at a given input power-.
« Last Edit: 06/17/2015 03:54 PM by Rodal »

#### SeeShells

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1935 on: 06/17/2015 03:41 PM »
...

I was referring also to the issue that there are a lot of mode shapes bunched next to each other, and that it is not practical to have a cavity resonate such that only one mode gets excited, but in general many mode shapes are excited with different degrees of participation in the response.  To model the degree of participation of different modes one has to conduct a Spectrum Analysis of the response spectra (which to my knowledge nobody has yet reported for the EM Drive -- the NASA COMSOL FEA reported analyses are eigenvalue analysis instead of spectra response analyses-

In my previous world, spectrum analysis was wide and narrow bandwidth FFT around ctr freq for spurious emmissions, mainly due to IMD distortion often caused by magnetic or dissimilar metals in the transmission line and radiator.

Perhaps we are speaking different languages...Spectra Response analysis is different, no?
A magnetron, for example, emits photons at different frequencies, as well as producing modulation (frequency, amplitude and phase modulation).  This results in feeding a complex spectrum to the truncated cone.
The truncated cone response will contain different modes shapes with different participation.  (This is also a function of RF feed placement and choice of RF feed, of course).

I spent a short amount of time looking for images for electromagnetic spectral analysis: I could not readily find spectrum analyses (modelled with software) for a magnetron exciting a cavity: it looks that it is not usual for Electrical Engineer researchers to conduct such analysis (*), but it is very usual for example to model earthquakes acceleration, (for obvious reasons, as an earthquake contains a rich spectrum),or to model the response of a bridge,or to model the response of a rocket to a vibration spectrum, for example coming from a chemical propulsion rocket engine, here is earthquake spectrum response analysis;

To model the response of the EM Drive, a spectral analysis would also be needed.

_____
(*) It is noteworthy that the Finite Element method was developed at MIT and other places during and after WWII to model aircraft aeroelastic response and that it was only used by Electrical Engineers to solve Maxwell's equations decades later.  The Finite Difference method, though was used prior to WWII and continues to be used to this date (in MEEP for example) to solve Maxwell's equations.

This help I don't have time to read it as I've got to leave. but...

#### rfmwguy

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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1936 on: 06/17/2015 03:47 PM »
....If you can only excite at 2.45 GHz then make it around 9.91 inches....

With a length of 251.72mm (9.91") you should get the following modes to resonate at 2.45GHz

1) TE013
2) TE114
3) TM014
4) TM113

Which one you will excite depends on antenna placement position, antenna design and orientation.

At least Dr Rodal and I agree the standard EW frustum

Frustum big diameter    m   0.2794000
Frustum small diameter   m   0.1588000
Frustum centre length   m   0.2286000
External Rf                   Hz   2,450,000,000

will not resonate at 2.45GHz.

Which does call Iulian's results into question. Just maybe his magnetron output frequency distribution was wide enough to get a weak resonance or maybe all we saw was the effect of rapidly heated microwaved moisture in the air.

9.91L it is then...thanks. I do have the ability to phase modulate the signal, but that experimentation will be for later. The variables I will use are the insertion points and antenna.

Playing it safe, I will go with midway side and simple omdirectional monopole. Was then going to adjust polarity 90 degrees. Afterwards, pick a new insertion point 15% towards small end and then large end, both polarities.

If null results, will move to collinear rather than monopole; basically increase gain (ERP) withing the frustum. This method doesn't need a tuning stub as the source is 50 ohm and so is the semirigid cable and antenna design.

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1937 on: 06/17/2015 03:58 PM »
....If you can only excite at 2.45 GHz then make it around 9.91 inches....

With a length of 251.72mm (9.91") you should get the following modes to resonate at 2.45GHz

1) TE013
2) TE114
3) TM014
4) TM113

Which one you will excite depends on antenna placement position, antenna design and orientation.

At least Dr Rodal and I agree the standard EW frustum

Frustum big diameter    m   0.2794000
Frustum small diameter   m   0.1588000
Frustum centre length   m   0.2286000
External Rf                   Hz   2,450,000,000

will not resonate at 2.45GHz.

Which does call Iulian's results into question. Just maybe his magnetron output frequency distribution was wide enough to get a weak resonance or maybe all we saw was the effect of rapidly heated microwaved moisture in the air.

Sorry, I don't agree with the word "will not resonate" in absolute terms.  You probably mean "will not resonate at a high Q".  There is always a spectral response of resonance, which will contains peaks with different amplitude at different frequencies.

The natural frequencies at which maximum Q occurs changes with  temperature, as the EM Drive heats up and the EM Drive expands, for example.

In the case of the EM Drive, we have the separate issues of at what frequencies maximum Q occurs, and at what frequencies maximum acceleration response occurs (if the EM Drive "acceleration" is not an artifact) -at a given input power-.

We are talking about EM Drives that deliver significant thrust and not SnowFlake thrust. At 2.45GHz there is no mode that will generate significant thrust using the EW frustum. In other words, exiting the EW frustum at 2.45GHz to look for thrust is a waste of time and resources.

If you make it a bit longer then things get interesting.

I suspect this is what Shawyer did with the Demonstrator as while the neck is a constant diameter section, it can expand the length beyond the point where the frustum taper stops and tune it to a longer effective electrical frustum length than the distance between the taper start and end points.

Is clear Shawyer knew what he was doing and why when he built the constant diameter section and the small end plate tuning system. Anyone who replicated that frustum and installed a end plate where the small end taper finished will never get it working at 2.45GHz as you need the extra length resonance provided by the constant diameter section having the sliding end plate about 1/2 way down.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

#### TheTraveller

##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1938 on: 06/17/2015 04:07 PM »
....If you can only excite at 2.45 GHz then make it around 9.91 inches....

With a length of 251.72mm (9.91") you should get the following modes to resonate at 2.45GHz

1) TE013
2) TE114
3) TM014
4) TM113

Which one you will excite depends on antenna placement position, antenna design and orientation.

At least Dr Rodal and I agree the standard EW frustum

Frustum big diameter    m   0.2794000
Frustum small diameter   m   0.1588000
Frustum centre length   m   0.2286000
External Rf                   Hz   2,450,000,000

will not resonate at 2.45GHz.

Which does call Iulian's results into question. Just maybe his magnetron output frequency distribution was wide enough to get a weak resonance or maybe all we saw was the effect of rapidly heated microwaved moisture in the air.

9.91L it is then...thanks. I do have the ability to phase modulate the signal, but that experimentation will be for later. The variables I will use are the insertion points and antenna.

Playing it safe, I will go with midway side and simple omdirectional monopole. Was then going to adjust polarity 90 degrees. Afterwards, pick a new insertion point 15% towards small end and then large end, both polarities.

If null results, will move to collinear rather than monopole; basically increase gain (ERP) withing the frustum. This method doesn't need a tuning stub as the source is 50 ohm and so is the semirigid cable and antenna design.

My understanding is you need to insert the antenna at the internal diameter point where the effective guide wavelength is equal to the actual guide wavelength and the antenna should be a 1/4 wave stub at the effective guide wavelength.

In my EMDrive Calc, the lower left chart shows a red vertical line where that condition is satisfied.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

#### Rodal

• Senior Member
• Posts: 5895
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##### Re: EM Drive Developments - related to space flight applications - Thread 3
« Reply #1939 on: 06/17/2015 04:28 PM »
...
This help I don't have time to read it as I've got to leave. but...
Thank you, I attach a copy of the full paper in case you want to use it for your Research purposes

<<Conclusion
Thus, the introduction of an external coupling channel
between cavities of a relativistic magnetron provides
an additional effective tool for controlling the oscillatory
processes in this device. At an optimum adjustment
of the coupling channel, a strong interaction between
oscillatory subsystems of the coupled cavities
evidently ensures a deeper stabilization of primary
processes in the magnetron, which are related to the
formation of an electron flow in the oscillating electromagnetic
field. The proposed external coupling
provides a strong selective mechanism of keeping
preset phase relationships in the system, which increases
the modal and spectral stability of radiation.
This ensures stable operation of the magnetron with a