Author Topic: EM Drive Developments - related to space flight applications - Thread 4  (Read 638683 times)

Online Rodal

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This is a thread - Thread 4 in the series - focused on objective analysis of whether the EM Drive (a cavity resonating at microwave frequencies) reported "thrust force" is an experimental artifact or whether it is a real propulsion effect  that can be used for space applications, and if so, in discussing those possible space propulsion applications.

Objective skeptical inquiry is strongly welcome.   Disagreements should be expressed politely, concentrating on the technical, engineering and scientific aspects, instead of focusing on people.   As such, the use of experimental data, mathematics, physics, engineering, drawings, spreadsheets and computer simulations are strongly encouraged, while subjective wordy statements are discouraged. Peer-reviewed information from reputable journals is strongly encouraged.  Please acknowledge the authors and respect copyrights.


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Links to previous threads:

Thread 1:
http://forum.nasaspaceflight.com/index.php?topic=29276.0

Thread 2:
http://forum.nasaspaceflight.com/index.php?topic=36313.0

Thread 3:
http://forum.nasaspaceflight.com/index.php?topic=37642.0

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Entry level thread:
http://forum.nasaspaceflight.com/index.php?topic=37438.0

Baseline NSF Article:
http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/



This is the link to the EM Drive wiki that users are encouraged to contribute to, edit for accuracy, and build as a knowledge resource for the EM Drive:

http://emdrive.wiki




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Also, and it should go without saying, amateur experiments are discouraged unless you have gained educated and/or professional advice for safety reasons.


« Last Edit: 08/07/2015 07:08 PM by Rodal »

Offline tleach

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Ok, I made some additions, modifications and improvements to my .xls spreadsheet (see attached).

I've created an alternate version of McCulloch's 3D equation because, why not.  I substituted area for diameter and that allowed me to drop that 6 off the front.  The McCulloch 3D Modified equation is (I know it's messy):

((P*Q*L)/c)*((1/L+Pi*Br^2)-(1/L+Pi*Sr^2))

P = Power in Watts
Q = Q
L = Length
c = Speed of Light
Br = Radius of the Large End
Sr = Radius of the Small End
Pi = π

Anyway, the above modifications just felt more natural than McCulloch's original 3D derivation and it brought the Tajmar prediction back into line.

One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.  It works with Shawyer and with Juan.  The predictions hold up with the Cannae drive for some reason, but fall flat on their face with the NASA tested Brady drive.  Once again, all specifications have been stolen from McCulloch's blog (with the exceptions of my daydream, rfmwguy and TheTraveller).

My predicted thrust for rfmwguy's build works out to 226.00mN! 

McCulloch's unedited 3D equation (assuming I entered it into the spreadsheet correctly) works out a prediction of 157.70mN!

Can't wait!
« Last Edit: 08/07/2015 06:59 PM by tleach »
T. Thor Leach

Offline JasonAW3

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I have a thought for anyone doing this experiment, both in the open air and in a vacume chamber.

     I would be interested in seeing what the total mass of the complete experiment rig is before and during the actual experiment.  I fully expect there to be some "noise" in the measurement, but I think a short series of these experiments should be able to average out the real mass measurements.  I have a couple of theories as to what might be going on, depending on what the actual mass readings are compared to before and during the experiment.

      I don't want to really go into the theories as it may affect the results.
« Last Edit: 08/07/2015 06:45 PM by JasonAW3 »
My God!  It's full of universes!

Offline demofsky

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Thinking about the ongoing controversy regarding TheTraveller's and Shawyer's theory raises a question for me.  Please forgive if this has been addressed in one of the earlier threads.

If Shawyer's theory is wrong then is Cullen's eqn 15 also incorrect??  Eqn 15 seems to be the bedrock of the theory (the bible they punch :D).

I am trying to unpack the controversy a bit from the recent standard of "the physics/theory is wrong".

Edit: Clarification.
« Last Edit: 08/07/2015 06:55 PM by demofsky »

Offline TheTraveller

One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline rfmwguy

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One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.
Because, as we've tried to explain countless times, the Qs in Yang/Shell were grossly overstated. I think Thor is generous when he only divides it by 10.

Want proof? Look at Tajmar's Q, then look at yang/shawyers and tell me why there is a so much disparity. The disparity lies in yang/shawyers unfamiliarity with cavity Q measurement.
« Last Edit: 08/07/2015 07:16 PM by rfmwguy »

Offline tleach

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One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.

Obviously Q isn't Q if everybody's measuring it differently and getting different values.

But mostly, I noticed a trend and thought it was interesting.  There was so much controversy swirling around with the whole "how do you calculate Q" thing, and since Q is an integral part of the McCulloch equation I thought I'd play around with it a bit.
T. Thor Leach

Offline rfmwguy

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One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.

Obviously Q isn't Q if everybody's measuring it differently and getting different values.

But mostly, I noticed a trend and thought it was interesting.  There was so much controversy swirling around with the whole "how do you calculate Q" thing, and since Q is an integral part of the McCulloch equation I thought I'd play around with it a bit.
About the only way to resolve this Thor, is to do what you did, adjust reported Q to achieve the reported thrust, given the other parameters remain constant. Once you have static formulae, use Q as the variable to equate reported thrust. Nicely done...

Offline X_RaY

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I am sure many people know the Smith program. For all other here are the links.
Note the Icon/subprogram "circles".
Circles for Q, SWR and more are addable.
( Be careful while interpretating:  Q of the cavity it selves for example is one thing the coupling factor of the antenna another, both are important!)
It's a very helpful program for the toolbox and RF engineering. :)

http://www.fritz.dellsperger.net/smith.html
http://fritz.dellsperger.net/downloads/Help%20V3.10.pdf

My wine don't like it at the moment  >:( :-\ for windows it works fine
« Last Edit: 08/07/2015 08:05 PM by X_RaY »

Offline TheTraveller

One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.

Obviously Q isn't Q if everybody's measuring it differently and getting different values.

But mostly, I noticed a trend and thought it was interesting.  There was so much controversy swirling around with the whole "how do you calculate Q" thing, and since Q is an integral part of the McCulloch equation I thought I'd play around with it a bit.

In the experimental EMDrive world of Shawyer, Prof Yang, Eagleworks and Tajmar, unloaded Q is measured and reported as the 3dB down bandwidth from the max return loss dB divided into the resonant frequency.

As Tajmar reported in the attachment.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline tleach

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One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.

And beside, when you use your spreadsheet from May and plug in a Df of .0844 and a Q of 45,000 you know what the mN of thrust predicted is?  It's 253.4 mN.  You know what my prediction is with the adjusted Q?  It's 251.24 mN (and I used 3.14 for Pi).  I'd say that's pretty darn close, wouldn't you?  And with observed results as high as 214, I'd say we're both in the same ballpark.
« Last Edit: 08/07/2015 07:24 PM by tleach »
T. Thor Leach

Offline TheTraveller

One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.
Because, as we've tried to explain countless times, the Qs in Yang/Shell were grossly overstated. I think Thor is generous when he only divides it by 10.

Want proof? Look at Tajmar's Q, then look at yang/shawyers and tell me why there is a so much disparity. The disparity lies in yang/shawyers unfamiliarity with cavity Q measurement.

They all measure their unloaded Q the same way.

Measured resonant frequency at max return loss dB / bandwidth at 3dB down from the peak return loss dBs.

Examples from Eagleworks, Tajmar and Prof Yang. All using the same method to calc unloaded Q.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline rfmwguy

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One other interesting thing I found was that many of the extremely large Q frustums can be brought back into line with predicted values by simply dividing the provided Q value by 10.

Why would you do that?

The Demonstrator EMDrive has a stated Q of 45,000 and Df of 0.844.

The data is what it is.

Obviously Q isn't Q if everybody's measuring it differently and getting different values.

But mostly, I noticed a trend and thought it was interesting.  There was so much controversy swirling around with the whole "how do you calculate Q" thing, and since Q is an integral part of the McCulloch equation I thought I'd play around with it a bit.

In the experimental EMDrive world of Shawyer, Prof Yang, Eagleworks and Tajmar, unloaded Q is measured and reported as the 3dB down bandwidth from the max return loss dB divided into the resonant frequency.

As Tajmar reported in the attachment.
I will take the time to explain this one more time, Mr T. after that, either you are deliberately trying to confuse the issue or you simply cannot comprehend.

Q = Ctr freq of resonance/3dB bandwidth (total half power bandwidth). Return loss has no bearing on a Q measurement, it MUST be a 2 port measurement, otherwise it is a single-port device akin to an antenna, not a cavity. The calculations used in virtually all relative RF and Microwave circuits calculate Q in the same way, not what yang/shawyer invented.

http://docs.lumerical.com/en/diffractive_optics_cavity_q_calculation.html

"High Q cavities

Derivation of Q factor formula:

The quality factor (Q) is defined as (see image) where wr is the resonant frequency ( ωr=2π fR) and FWHM is the full width half max of the resonance intensity spectrum."

Offline tleach

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They all measure their unloaded Q the same way.

Measured resonant frequency at max return loss dB / bandwidth at 3dB down from the peak return loss dBs.

Examples from Eagleworks, Tajmar and Prof Yang. All using the same method to calc unloaded Q.

You are absolutely, 100% right.  I hereby defer to you in all future disagreements.  I apologize for my impertinence.  My spreadsheet is wrong and your spreadsheet is right.
T. Thor Leach

Offline TheTraveller

I will take the time to explain this one more time, Mr T. after that, either you are deliberately trying to confuse the issue or you simply cannot comprehend.

Q = Ctr freq of resonance/3dB bandwidth (total half power bandwidth). Return loss has no bearing on a Q measurement, it MUST be a 2 port measurement, otherwise it is a single-port device akin to an antenna, not a cavity. The calculations used in virtually all relative RF and Microwave circuits calculate Q in the same way, not what yang/shawyer invented.

http://docs.lumerical.com/en/diffractive_optics_cavity_q_calculation.html

"High Q cavities

Derivation of Q factor formula:

The quality factor (Q) is defined as (see image) where wr is the resonant frequency ( ωr=2π fR) and FWHM is the full width half max of the resonance intensity spectrum."

That may be how you would do it but it is not how Shawyer, Prof Yang, Eagleworks and Prof Tajmar measure their frustums unloaded Q as I just showed you.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

They all measure their unloaded Q the same way.

Measured resonant frequency at max return loss dB / bandwidth at 3dB down from the peak return loss dBs.

Examples from Eagleworks, Tajmar and Prof Yang. All using the same method to calc unloaded Q.

You are absolutely, 100% right.  I hereby defer to you in all future disagreements.  I apologize for my impertinence.  My spreadsheet is wrong and your spreadsheet is right.

It has nothing to do with me nor my spreadsheet.

I just showed you how Prof Yang, Eagleworks and Prof Tajmar measured their frustums unloaded Q. Note Prof Tajmar used an expert professor in uW engineering to measure his frustums unloaded Q by using the same 1 port S11 return loss method as used by Shawyer, Prof Yang and Eagleworks.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline sghill

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The testiness of this current discussion aside, I am genuinely interested in the reason why there is a difference between these two Q value viewpoints.
Bring the thunder Elon!

Offline TheTraveller

The calculations used in virtually all relative RF and Microwave circuits calculate Q in the same way, not what yang/shawyer invented.

An EMDrive cavity is not a standard cavity.

As I have shown you before, it is industry standard practice, maybe not yours, to use 1 port S11 return loss to measure unloaded cavity Q. You may disagree with the information on the slide but it is incorrect to say Shawyer and Prof Yang invented this method to measure unloaded Q.

As the slide clearly shows, to some it is the way to do the measurement.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

The testiness of this current discussion aside, I am genuinely interested in the reason why there is a difference between these two Q value viewpoints.

In the EMDrive world measuring unloaded Q via S11 return loss at the 3bd down bandwidth is how it is measured.

So say Shawyer, Prof Yang, Eagleworks and Prof Tajmar.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline WarpTech

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The testiness of this current discussion aside, I am genuinely interested in the reason why there is a difference between these two Q value viewpoints.

As far as I can gather, @TT is saying, "How they did it". @rfmwguy is saying "How it should've been done." and @tleach is saying "This is how it seems to fit McCulloch's formula."

Which BTW, McCulloch doesn't define how to measure Q. He simply redefines it as the number of bounces (reflections), in the time it takes the photon to decay to zero. So that's not even the same definition of the Q that is being kicked around here. @tleach was trying to bridge that gap.

What I conclude is, the experimenters may or may not be measuring it consistently using the same methodology, but in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.
Todd

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