Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1803476 times)

Offline Rodal

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Did ever someone ask for the dimensions (for verification) personally?
 
yangjuan@nwpu.edu.cn

It isn't helpful to poke in the dark, IMHO

PS: I am not the one who want to do ;)

Several people have asked (Ref: NSF threads 1 and 2).  No answers have been reported.  Ever.

It has been reported Prof. Yang told a Scientific News reporter that "publicity about her EM Drive research is most unwelcome"
no answer?  >:( bad scientist :(

There is always hope.  Maybe SeeShells can contact her.

Online flux_capacitor

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Did ever someone ask for the dimensions (for verification) personally?
 
yangjuan@nwpu.edu.cn

It isn't helpful to poke in the dark, IMHO

PS: I am not the one who want to do ;)

Several people have asked (Ref: NSF threads 1 and 2).  No answers have been reported.  Ever.

It has been reported Prof. Yang told a Scientific News reporter that "publicity about her EM Drive research is most unwelcome"
no answer?  >:( bad scientist :(

She doesn't do what she wants, this is China. So take into account politics and human rights. Moreover NWPU is also a military school. So add geopolitics and defense purpose.

Offline X_RaY

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Did ever someone ask for the dimensions (for verification) personally?
 
yangjuan@nwpu.edu.cn

It isn't helpful to poke in the dark, IMHO

PS: I am not the one who want to do ;)

Several people have asked (Ref: NSF threads 1 and 2).  No answers have been reported.  Ever.

It has been reported Prof. Yang told a Scientific News reporter that "publicity about her EM Drive research is most unwelcome"
no answer?  >:( bad scientist :(

She doesn't do what she wants, this is China. So take into account politics and human rights. Moreover NWPU is also a military school. So add geopolitics and defense purpose.
Yes i've edit my post while you're typing ;)
« Last Edit: 08/02/2015 08:41 PM by X_RaY »

Offline SeeShells

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Did ever someone ask for the dimensions (for verification) personally?
 
yangjuan@nwpu.edu.cn

It isn't helpful to poke in the dark, IMHO

PS: I am not the one who want to do ;)

Several people have asked (Ref: NSF threads 1 and 2).  No answers have been reported.  Ever.

It has been reported Prof. Yang told a Scientific News reporter that "publicity about her EM Drive research is most unwelcome"
no answer?  >:( bad scientist :(

There is always hope.  Maybe SeeShells can contact her.
Nada nothing...digital silence from that end.

Online WarpTech

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...It makes perfect sense to me that when she calculated the stresses (and therefore the resonance of the electromagnetic fields) she was cognizant of the fact (obvious to anyone performing a FEA solution) that there is no such thing as a sharp cut-off frequency, and thus she was free to choose a smaller diameter for the small base...

Given that there is no sharp cut-off. If we have a frustum that is too small at the small end and too big at the big end. What determines the resonance? Is there any mode that would resonate without interacting with either end?
Todd


Offline X_RaY

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Did ever someone ask for the dimensions (for verification) personally?
 
yangjuan@nwpu.edu.cn

It isn't helpful to poke in the dark, IMHO

PS: I am not the one who want to do ;)

Several people have asked (Ref: NSF threads 1 and 2).  No answers have been reported.  Ever.

It has been reported Prof. Yang told a Scientific News reporter that "publicity about her EM Drive research is most unwelcome"
no answer?  >:( bad scientist :(

There is always hope.  Maybe SeeShells can contact her.
Nada nothing...digital silence from that end.
Interesting but not good, don't know why they publish the mail address...
We have to believe owen math i think.
I am curious about the results with your geometrie. :)
« Last Edit: 08/02/2015 09:10 PM by X_RaY »

Offline X_RaY

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...It makes perfect sense to me that when she calculated the stresses (and therefore the resonance of the electromagnetic fields) she was cognizant of the fact (obvious to anyone performing a FEA solution) that there is no such thing as a sharp cut-off frequency, and thus she was free to choose a smaller diameter for the small base...

Given that there is no sharp cut-off. If we have a frustum that is too small at the small end and too big at the big end. What determines the resonance? Is there any mode that would resonate without interacting with either end?
Todd
Did you notice Dr. Rodal's document? There is still resonance, the side walls do the job of the endplates (topologically) ....
Sorry, i'm sure you did :)
« Last Edit: 08/02/2015 09:07 PM by X_RaY »

Offline Rodal

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...It makes perfect sense to me that when she calculated the stresses (and therefore the resonance of the electromagnetic fields) she was cognizant of the fact (obvious to anyone performing a FEA solution) that there is no such thing as a sharp cut-off frequency, and thus she was free to choose a smaller diameter for the small base...

Given that there is no sharp cut-off. If we have a frustum that is too small at the small end and too big at the big end. What determines the resonance? Is there any mode that would resonate without interacting with either end?
Todd

Yes resonance definitely plays a role.  As explained in my post about the insectoid overlord.  Take a look at the Q formula.  In the numerator you have the integral over the volume of B square.  In the denominator you have the integral over the surface.  To maximize Q you want to maximize the numerator and minimize the denominator.
« Last Edit: 08/02/2015 09:52 PM by Rodal »

Offline SteveD

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weekly interactive particle
you can't go peaking under peoples clothes.

Sometimes poor spelling is an advantage  8)

Sorry, I was posting from a tablet late at night.  The "keyboard" doesn't always pick up every keystroke and then the auto-correct tries to be "helpful."

Offline seggybop

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Did those attempting to contact Yang do so in legit non-Google translated Chinese? If not, I can try sending a message that might be more intelligible / likely to be acknowledged. Or even if it's been attempted already, sending an additional request for info might not hurt.

Offline Rodal

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Did those attempting to contact Yang do so in legit non-Google translated Chinese? If not, I can try sending a message that might be more intelligible / likely to be acknowledged. Or even if it's been attempted already, sending an additional request for info might not hurt.
Sure, by all means.  Try asking her what are the dimensions of the EM Drive she tested to get the highest force and force/InputPower ever reported:

very simple question:

Big Base Diameter = m
Small Base Diameter = m
Length (measured perpendicular to the bases) = m

Online flux_capacitor

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@seggybop: Do you speak and read Chinese?
If so, can you translate in English the left-side column in the attached table?

Online flux_capacitor

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I don't trust Yang's drawings. I think they have incorrect proportions. So I don't trust results defined from a ratio in those drawings, including the half-cone angle.

For those reasons I tried to learn from Yang's 2010 paper how she calculates the dimensions of a resonating frustum from a chosen frequency and mode. In the following I summarize my understanding of the translation, and my attempt to find some dimensions.

METHOD

1. She starts from a cylinder waveguide.

2. She uses finite element method to calculate the distribution of EM fields in a cavity, for a chosen mode and near a chosen frequency. For example: TE012 around 2.45 GHz.

3. She sets a cylindrical diameter D and a cavity length L according to the mode she wants to use. This can be done according to the figure 3 in her 2010 paper. I add a modified version of that figure attached below, extended and with a grid added for precision. WARNING: If we want a half-cone angle that does not approaches 0 (cylinder) we must have Ds << D << Db

We get what I decided to call the YANG NUMBER Yn on the y axis.
Yn = (f × D)2 × 10-20
where f is the frequency in Hz, and D the cylindrical diameter in cm.

4. This cylindrical diameter D is also the "average diameter" of the frustum. It is NOT the diameter of the small or big end.

5. Set the the small end diameter Ds as the cylindrical waveguide cut-off diameter. So for TE012 at 2.45 GHz:
Ds = 14.92 cm

6. The big end diameter Db then follows from the average diameter D and the small diameter Ds.
Since
D = (Db + Ds)/2
Then
Db = 2×D - Ds

7. She performs again a finite element numerical simulation for the distribution of the EM field. And she repeats adjusting through small steps the small end Ds, big end Db, cavity length L, until she finds the correct resonance.
« Last Edit: 08/02/2015 11:11 PM by flux_capacitor »

Online flux_capacitor

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And here are my attempts to calculate some dimensions according to Yang's method set in my previous message; at first with a high cone angle, then fixing L = 24 cm from starts which gives the already noted low cone angle.

1ST EXAMPLE

Many possibilities to make a frustum according to these laws. At first I chose to set Db at twice the value of Ds, the later being the cut-off diameter. So:
Ds = 14.92 cm
Db = 29.84 cm

Hence the average diameter D is:
D = 22.38 cm

I calculate the Yang number Yn :
Yn = (f × D)2 × 10-20
Yn = 30-20 cm/s

With this value of Yn on the y axis, we found the corresponding value on the x axis following the TE012 straight line on the graph:
(D/L)2 = 2
Hence
L = 15.825 cm

In this case, half-cone angle = 25.2°

Playing with those numbers, I can't confirm this frustum resonates at TE012 and 2.45 GHz as I don't have access to finite element software.



2ND EXAMPLE WITH L = 24 CM

It is worth noting that when I start from elsewhere, fixing both the small end at cutoff diameter Ds = 14.92 cm and the cavity length L = 24 cm from start,
Then following the same process I finally get:
Yn = 18
Db = 19.71 cm
D = 17.317 cm
Hence as Db is not very different than Ds and the cavity length is quite long, it becomes almost a cylinder as noted before by Rodal.

But is it wrong? Yang's translated notes (typos corrected):

Quote from: Juan YANG
The mode TE012 which has smallest Large-End has the largest thrust, so has the highest quality factor and thrust. Mode TM011 thruster has the worst performance. As the Large-End of the cavity increases, the height of cavity reduce, cavity volume and wall surface area also reduced, leading to low quality factor and producing less thrust.

So she seems to confirm that a longer cavity with the big end as small as possible, thus with a very low cone-angle, the frustum being almost cylindrical, has a higher Q and higher thrust…
« Last Edit: 08/02/2015 11:26 PM by flux_capacitor »

Online flux_capacitor

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The last case you calculated has a cone half-angle of only 5.70 degrees: practically a cylinder.

Not only I don't trust, I think, based on calculations, that these geometries that are close to a cylinder will result in lower (if any thrust).  I find comfort with the fact that my calculations agree with Shaywer, who has used much larger cone angles and actually has been increasing the cone half-angle in his EM Drive.  His latest design is over 30 degrees as I recall.  NASA and everybody else has used much larger cone angles than 6 degrees as well.

The formulas of McCulloch, Shawyer and Notsosureofit all show that a cone half-angle of only 6 degrees is very ineffective.  The Meep runs post-processed with Wolfram Mathematica also show the poor performance of the 6 degree almost a cylinder geometry.   I much trust these formulas and the geometries used by Shawyer and NASA, and much more trust the drawings of Yang than any result from her 2010 publication hinting at an angle of 6 degrees.

I don't think that Yang obtained the highest thrust and thrust/InputPower using a cone with a half angle of only 6 degrees.

If SeeShells tests a cone at 6 degrees we will learn the truth from her test results...

Yang may have done a typo in her formula, but not in what she explains. And she clearly claims the smallest the big end and the longest the cavity, the higher the thrust. This perplexes me too.

This Chinese trips leads us to a dead-end for now. I agree we have to wait for Shell's experimental results.

Offline Rodal

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So she seems to confirm that a longer cavity with the big end as small as possible, thus with a very low cone-angle, the frustum being almost cylindrical, has a higher Q and higher thrust…

In the above message the lines in Yang's graph have been extrapolated to (D/L)^2 =2 for the case with half-cone angle = 25.2°

The maximum value in Yang's graph for (D/L)^2 is approximately 1.  Thus the extrapolation in the above message is at a range that is twice the displayed range.

It is usually not a good idea to extrapolate.   If extrapolation is warranted, the author (Yang) would have better served the readers by providing the equations.  Usually when plots are given like this the assumption is that interpolation is warranted within the displayed range, and that extrapolation is not warranted.


1)  It is dangerous to extrapolate because the behavior may be approximately linear in the range displayed in the graph but nonlinear outside the displayed range.  Yang plots these lines without displaying marks for the cases she calculated by Finite Element Analysis.  That is not good scholarship on Yang's part.  In this forum where I have performed fits for fitted data I have shown where the calculated numbers are by marking them with big circles.  Since Yang has not displayed the points she calculated we have no idea whether she calculated just two points and joined them with a line.  In other words, we don't know whether the behavior is nonlinear even within interpolation.  For a cylinder, the behavior is indeed describable by a square (D/L)^2 on the horizontal axis and a square (f D) on the y axis, as shown by the following equation if one multiplies both sides of the equation by R^2.



Not for a truncated cone.  Hence the displayed lines must be for approximately cylindrical geometries, the displayed lines are valid for cases where the frequency of a truncated cone can be calculated as the frequency of a cylinder having a diameter equal to the average of the big base and the small base diameters.

2) Yang plotted the mode shape lines, presumably in the range where she used them.  (D/L)^2 =2 is outside the range she used by a large margin: twice as much.  By convention, any case needing extrapolation is a case she did not consider.  Therefore it stands to reason that the case extrapolated (half-cone angle = 25.2°) is not a valid geometry for Yang's drive.


Note: in both of my analysis of Yang's geometry (the 6 degree case and the 15 degree case)  I interpolated within the ranges given by Yang.
« Last Edit: 08/03/2015 01:03 AM by Rodal »

Offline rfmwguy

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NSF-1701 update...the boring static thermal tests are near complete. Teardown today exposed arc point. It was bottom copper clad to a small solder peak on frustum screen. Shaved it off and put screen mesh across Db. Also added a heatsink to side of magnetron. Long story short, I will do one more thermal test just to be sure. Then comes the galinstan cups and electrodes.

I'm about 2 weeks from the first fulcrum test, which I will live stream. Let's get this party started...

Offline Rodal

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Another thing I learned from this Yang exercise:

Yang is NOT following Shawyer:

1) If Yang's geometry is the 6 degree geometry, Yang is following an almost cylindrical geometry in complete contradiction with Shawyer who has been increasing the cone angle (presently using cone half angle ~30 degrees for his superconducting design) and whose Design Factor formula gets better Design Factor for increasing difference between small and large diameter.  (Yang's geometry at 6 degrees has minimal difference between the diameters). Therefore Yang is ignoring Shawyer's prescriptions.

The following quotation from Yang is in complete contradiction to Shawyer, Yang is ignoring Shawyer's prescriptions:

Quote from: Juan YANG
The mode TE012 which has smallest Large-End has the largest thrust, so has the highest quality factor and thrust. Mode TM011 thruster has the worst performance. As the Large-End of the cavity increases, the height of cavity reduce, cavity volume and wall surface area also reduced, leading to low quality factor and producing less thrust.


2) If Yang's geometry is the 15 degree geometry (or higher cone half angle) then the diameter of the small base is below waveguide cut-off and therefore Yang is ignoring Shawyer's prescriptions.

Either way, it is clear that Yang is ignoring Shawyer's prescriptions, of one form or another. 
« Last Edit: 08/03/2015 12:58 AM by Rodal »

Offline SeeShells

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If you think that's it we have all together :)

SD=0.1492m
BD=0.200m
L=0.240m
f_res(TE012)=~2,4537GHz
angle=6,041deg


with SD 0.15m i get 2,4490GHz
angle=5,946deg

Thank you.  Confirmed:

1) There was no "booboo"

2) Your computer program agrees quite well with my computer program (once again).  TheTraveller's program  is only off by 2%, a difference which I consider to be an utterly negligible difference when we are talking about much larger differences here.  The calculations by TheTraveller are quite acceptable for engineering purposes.
I went over my pen and paper calculations again and it does work out. I feel better in a way.

Shell

Offline Silversheep2011

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Did those attempting to contact Yang do so in legit non-Google translated Chinese? If not, I can try sending a message that might be more intelligible / likely to be acknowledged. Or even if it's been attempted already, sending an additional request for info might not hurt.
from wikipedia
https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster

Chinese Northwestern Polytechnical University (NWPU)[edit]

The editor of Wired magazine who covered these experimental results reported that he received comments from the Chinese researchers stating "the publicity was very unwelcome, especially any suggestion that there might be a military application"[6] and that Yang told him that "she is not able to discuss her work until more results are published".[5]

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