Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1802821 times)

Offline SeeShells

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From the intro in the abstract paper:

How can Tajmar says:
Quote
After developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventor
and then measure:
Quote
Due to a low Q factor of <50

Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?

Take a look at my prior posts (the ones were I suggested questions for Dr. Bagelbytes to ask).  I think that there was gross overcoupling.

Perhaps intentional to the magnetron's bandwidth.
The Q is a major question mark why so low and you might be right on the coupling or placement of insertion, but still no air filled cavity in vacuum and we still see the major difference in vacuum and air.
Shell


Offline birchoff

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From the intro in the abstract paper:

How can Tajmar says:
Quote
After developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventor
and then measure:
Quote
Due to a low Q factor of <50

Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?

Take a look at my prior posts (the ones were I suggested questions for Dr. Bagelbytes to ask).  I think that there was gross overcoupling.

Perhaps intentional to the magnetron's bandwidth.

Not sure if it was overcoupling. But the magnetron only outputted 2.4ghz. They would have needed something that outputed 3Ghz to get a higher Q

Offline Blaine

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What is overcoupling?
Weird Science!

Offline Prunesquallor

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Tajmar Experimental results

Cavity Length(m) = 0.0686
Big Diameter(m) = 0.0541
Small Diameter(m) = 0.0385

Ugh... This thruster is teeny.  Like half a shot glass.

Edit: corrected cut
« Last Edit: 07/25/2015 10:41 PM by Prunesquallor »
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Offline flux_capacitor

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The Q is a major question mark why so low and you might be right on the coupling or placement of insertion, but still no air filled cavity in vacuum and we still see the major difference in vacuum and air.
Shell

Yes, to approximately summarize the difference between ambient air and a hard vacuum in Tajmar's experiment, the force in a vacuum was about ten times less than in air, at half the Q.
« Last Edit: 07/25/2015 10:40 PM by flux_capacitor »

Offline deltaMass

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With such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.

Offline WarpTech

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I appreciate the help. Now i understand the issue. However, wouldn't a ray-vector approach show the same behavior without the need for spherical harmonics?

Below is what Zeng & Fan wrote for impedances. Impedance is basically u0*velocity. The TE mode is the phase velocity, the TM mode is the group velocity. How do we plot this as a function of kr?  I can't interpret something I don't understand and this just looks like gibberish to me, without some way to plot it out and visualize it. Sorry, I'm an engineer not a mathematician.
Todd

I think they are Henkel spherical functions.  I could plot it with Mathematica but I have some $$$ work to do.  Didn't Zeng and Fan have some plots of impedance in their paper?

Ha! Too much going on in my house and head right now. I almost missed it. Thank you! :)  And there's our answer! Look at TM01 mode graph. Since they normalized to Z0, (Eta), then c=1. This graph clearly shows that the group velocity for small kr is faster than light. Likewise, the TE11 mode gives the phase velocity as slower than light for small kr.

Given the thrust to power ratio F/P = 1/v_phase. Then for small kr, there is an enormous thrust for very little power!
Thanks Doc! That helped. No need to do the math, perturbations or the plots, it's all right here. I pulled apart their impedance equation as best I could and found that 1/kr = c*cos(theta)/wz, which is the same 1/wz dependence I have in the cylindrical equation. Also, the derivative of the Hankel function is in the same place as the gradient dw/dz in my cylindrical equation. So the cylindrical equation is a good way to visualize it, IMO. Zeng and Fan give the exact solution, which for small kr and large kr, is in agreement with the cylindrical equation. What my equation is missing are the resonant peaks and valleys in the impedance, but the 1st approximation of the curve has the correct dependence for small and large kr. Woo hoo!
Todd

Offline aero

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@Dr. Rodal

The new big and small end lateral antenna csv files are up and I have removed the previous version. This time they are in two folders so you won't get them mixed up. Naming convention is the same as my most recent previous data set uploaded, with only the base name changed, as you will see.

Each folder contains a Meep Data Request file to describe the run. Ask me for the information that I forgot to add.

https://drive.google.com/folderview?id=0B1XizxEfB23tfkF0Z184NHRtd0ViN28tNzRDY3JzSVc0WFBTOGZmSFZMcUpWLWJfcDRfZEU&usp=sharing

aero
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Offline RonM

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

space time is only flat where there is no gravity.  This is why light follows a curved path in the presence of a gravitational well.  http://www.math.brown.edu/~banchoff/STG/ma8/papers/dstanke/Project/curved_space.html

If you can artificially engineer a gravitational well of sorts, "maybe not exactly gravity but mimic it at a specific frequency", then you might be able to effectively curve space and time/energy at that particular wavelength.
Spacetime is curved in the presence of gravity but all measurements up to now is that space itself (not spacetime) is Euclidean flat.   RonM's statement was that space is (Euclidean) flat.  He is correct.


Experimental data from various, independent sources (WMAP, BOOMERanG and Planck for example) confirm that the universe is flat with only a 0.4% margin of error.

https://en.wikipedia.org/wiki/Shape_of_the_universe#Curvature_of_Universe


This is an important distinction.

Spacetime should not be confused with space.

Does the 0.4% margin of error in space being Euclidean flat leave enough room for a General Relativity explanation of EM drive thrust?

Offline demofsky

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From the intro in the abstract paper:

How can Tajmar says:
Quote
After developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventor
and then measure:
Quote
Due to a low Q factor of <50

Why was the Q so desperately low? What could possibly have gone wrong with all those experts onboard and Dresden leading-edge technologies?

Take a look at my prior posts (the ones were I suggested questions for Dr. Bagelbytes to ask).  I think that there was gross overcoupling.

Perhaps intentional to the magnetron's bandwidth.

Not sure if it was overcoupling. But the magnetron only outputted 2.4ghz. They would have needed something that outputed 3Ghz to get a higher Q

Also, the waveguide was almost as big as the fustrum!  Based on what has been discussed in these threads I am shocked they get a result at all! 

The following image is From "Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects  M. Tajmar and G. Fiedler"

51st AIAA/SAE/ASEE Joint Propulsion Conference

http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

Edit:  Added attribution.
« Last Edit: 07/26/2015 11:21 PM by demofsky »

Offline demofsky

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And here is the COMOSOL plot.

The following image is From "Direct Thrust Measurements of an EM Drive and Evaluation of Possible Side-Effects  M. Tajmar and G. Fiedler"

51st AIAA/SAE/ASEE Joint Propulsion Conference

http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

Edit:  Added attribution.
« Last Edit: 07/26/2015 11:22 PM by demofsky »

Offline birchoff

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With such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.

What do you mean by the aparatus not being self contained?

Online Rodal

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And here is the COMOSOL plot.

That shows it!

They went for the lowest mode !

That explains the small dimensions: they are necessary to excite the lowest fundamental mode at 2.45 GHz

Makes perfect sense.  Lowest modes have higher output.  This is what NASA was going to do also with the magnetron: excite the lowest mode (remember how they were going to segment the present truncated cone to do that).

It never made sense to me to go for TE013, TM212 or TM114 or TM113

The higher the mode the lower the amplitude
« Last Edit: 07/25/2015 10:57 PM by Rodal »

Offline RonM

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With such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.

I'll drink a couple of beers to it. Then again, I was planning on doing that tonight anyway.  ;)

Still, the results are positive. There's more work to do to figure out what is or is not going on.

I'd like to help, but my BS degree isn't up to the math and I've never worked with microwaves before, just optical wavelengths. Microwaves are dangerous. So I'll let the experts carry on the good work.

Offline aero

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Tajmar Experimental results

Cavity Length(m) = 0.0686
Big Diameter(m) = 0.0541
Small Diameter(m) = 0.0385

Ugh... This thruster is teeny.  Like half a shot glass.

Edit: corrected cut

Dr. Rodal - using your exact solution, what is the resonant frequency of this cavity?

And does that huge waveguide hanging off the side make the device something other than a conical frustum? Looks like different geometry to me.

aero
« Last Edit: 07/25/2015 11:00 PM by aero »
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Online Rodal

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Tajmar Experimental results

Cavity Length(m) = 0.0686
Big Diameter(m) = 0.0541
Small Diameter(m) = 0.0385

Ugh... This thruster is teeny.  Like half a shot glass.

Edit: corrected cut

Dr. Rodal - using your exact solution, what is the resonant frequency of this cavity?

And does that huge waveguide hanging off the side make the device something other than a conical frustum? Looks like different geometry to me.

aero

Excellent point.  I should analyze that when I have a chance.  Now I have to have a couple of beers , a Martini, to join Ron M :)
« Last Edit: 07/25/2015 11:03 PM by Rodal »

Offline flux_capacitor

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Excellent point.  I should analyze that when I have a chance.  Now I have to have a couple of beers , a Martini, to join Ron M :)

Me too! Shaken, not stirred ;)

This tiny size is even weirder considering Shawyer helped Tajmar in designing the cavity.

Offline WarpTech

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Good point, but I believe conventional wisdom is that space is flat. Of course, conventional wisdom could be wrong. If space isn't perfectly flat, then maybe we are on to something that would make a good drive for spaceflight. Still, no flying cars.  :(

space time is only flat where there is no gravity.  This is why light follows a curved path in the presence of a gravitational well.  http://www.math.brown.edu/~banchoff/STG/ma8/papers/dstanke/Project/curved_space.html

If you can artificially engineer a gravitational well of sorts, "maybe not exactly gravity but mimic it at a specific frequency", then you might be able to effectively curve space and time/energy at that particular wavelength.
Spacetime is curved in the presence of gravity but all measurements up to now is that space itself (not spacetime) is Euclidean flat.   RonM's statement was that space is (Euclidean) flat.  He is correct.


Experimental data from various, independent sources (WMAP, BOOMERanG and Planck for example) confirm that the universe is flat with only a 0.4% margin of error.

https://en.wikipedia.org/wiki/Shape_of_the_universe#Curvature_of_Universe


This is an important distinction.

Spacetime should not be confused with space.

Does the 0.4% margin of error in space being Euclidean flat leave enough room for a General Relativity explanation of EM drive thrust?

If spacetime were flat in 4D, there would be no gravity anywhere. Mass & energy curve spacetime, black holes and neutron stars exist, gravity exists. There is no doubt about these things. Spacetime is not flat near matter or energy.

On the cosmic scale of the entire universe, they do not detect any curvature that would indicate it is either open like a saddle, or closed like a sphere. That is what they mean by "flat". On the scale of things, the Earth is polished smoother than a new bowling ball, yet I would not want to climb Mt. Everest.

Inside the frustum, if resonant EM frequency shifts from one end to the other, and its potential energy drops. Then it is mimicking Newtonian gravity. One thing I'm trying to remember that might help, is that a variable refractive index with variable speed of light c/K is equivalent to a variable impedance Z with a constant speed of light, c. It is equivalent to doing a coordinate transformation from that of a distant inertial observer to that of a local inertial reference frame. Two sides of the same coin.
Todd

Offline birchoff

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With such small thrust and the apparatus not being self-contained, I am wary to break out any champagne here.

I'll drink a couple of beers to it. Then again, I was planning on doing that tonight anyway.  ;)

Still, the results are positive. There's more work to do to figure out what is or is not going on.

...

Intriguing... by all means. But I need to see an explaination for why the vertical orientation still registering thrust on the torsion balance. I have been following these emdrive threads with the assumption that a torsion balance could only move horizontally left(positive) or right(negative). So if arranging the thruster in a vertical orientation still registers thrust in the positive direction and my assumption is correct. Either there is still another source of error in the measurement or preferrably or that behavior tells us more about how the emdrive is propelling itself.

Offline deltaMass

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This graph clearly shows that the group velocity for small kr is faster than light.
Seriously?

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