Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1802808 times)

Offline WarpTech

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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!

This is what happens when physicists pretend to be engineers. LOL!

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.

What do you mean by the aparatus not being self contained?
The power supply was not a part of the device for which a force was measured. Instead, it was connected to the device via Galinstan contacts. Thus the measured device was not self-contained, and leaves open the possibility of spurious forces caused by this external connection (thermal catenary sag for one, electromagnetic coupling for another, etc.).

Offline WarpTech

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

I am interpreting what I see. If you or anyone else has a different interpretation of it, by all means let's discuss it. This is important, because this is where the breakthrough in "new physics" is going to be found. Impedance is what it is, permeability x velocity. Normalized, these plots represent relative velocity,  relative impedance or relative refractive index as a function of kr and cone angle. Take your pick.

Hmm... getting over that peak in the phase velocity sort of reminds me of jumping to warp, doesn't it? ;)
Todd

EDIT: The peak in the TE11 graph occurs at the same kr, where the light barrier is broken in the TM01 graph. It is precisely where the ingoing wave becomes evanescent.
 
« Last Edit: 07/26/2015 12:38 AM by WarpTech »

Offline Tron

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Tajmar Experimental results

Cavity Length(m) = 0.0686
Big Diameter(m) = 0.0541
Small Diameter(m) = 0.0385
Dielectric = None
Frequency = 2.44Ghz
Input Power = 700w (output of magnetron)
Pressure = 410-6
Q = 20.3 (seems like this was measured and calculated after they finished all reported testing)
Force (mN) = 0.02


McCulloch's formula F = 6PQL/c * ( 1/(L+4wb) - 1/(L+4ws) )  predicts unless I'm mistaken 0,019 mN for those numbers. I think it's remarkable.

Offline demofsky

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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.

This gets into an earlier discussion about what might be happening inside the fustrum.  Shell speculated that evanescent waves collapsed at the big end which prompted DrBagleBites to recall a simple cavitation experiment.  In essence, there may be a weakness around the seams of the base and evanescent waves (or something) are leaking out the sides asymmetrically.

This type of leakage could explain the chaotic behaviour exhibited by the baby EM Drive, for instance.

Could an explanation for the EmDrive's internal workings be paralleled to something like cavitation bubbles in liquid? Such as:

It's kind of a wild thought, but for some reason it made sense to me.
« Last Edit: 07/26/2015 12:00 AM 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?
The power supply was not a part of the device for which a force was measured. Instead, it was connected to the device via Galinstan contacts. Thus the measured device was not self-contained, and leaves open the possibility of spurious forces caused by this external connection (thermal catenary sag for one, electromagnetic coupling for another, etc.).

Thanks for the explaination. though I cannot say I share your concern, eventhough I am also not ready to consider this a validation.

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.

This gets into an earlier discussion about what might be happening inside the fustrum.  Shell speculated that evanescent waves collapsed at the big end which prompted DrBagleBites to recall a simple cavitation experiment.  In essence, there may be a weakness around the seams of the base an evanescent waves (or something) are leaking out the sides asymmetrically.

This type of leakage could explain the chaotic behaviour exhibited by the baby EM Drive, for instance.

Could an explanation for the EmDrive's internal workings be paralleled to something like cavitation bubbles in liquid? Such as:

...

It's kind of a wild thought, but for some reason it made sense to me.

Entirely plausible. Since the detected microwave radiation leaking out of the device even though it was sealed.

Offline inquisitive-j

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I'm sure someone has addressed this concern before but just in case it hasn't been brought up, has anyone considered the gyroscopic effect? My understanding is that a magnetron works by moving electrons in a circular path. I realize that the mass of the electrons and therefore the corresponding gyroscopic effect would be very small, but we are talking about exceedingly small forces here. The emdrive is being tested on a torsion pendulum and a gyroscope hanging from a pendulum will attempt to move in a precession motion. This might help explain why, according to some reports, the orientation of the engine affects the measured thrust. If it is the gyroscopic effect that is producing the apparent thrust, then it will of course be useless as any sort of engine.
« Last Edit: 07/25/2015 11:56 PM by inquisitive-j »

Offline rfmwguy

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I'm sure someone has addressed this concern before but just in case it hasn't been brought up, has anyone considered the gyroscopic effect? My understanding is that a magnetron works by moving electrons in a circular path. I realize that the mass of the electrons and therefore the corresponding gyroscopic effect would be very small, but we are talking about exceedingly small forces here. The emdrive is being tested on a torsion pendulum and a gyroscope hanging from a pendulum will attempt to move in a precession motion. This might help explain why, according to some reports, the orientation of the engine affects the measured thrust. If it is the gyroscopic effect that is producing the apparent thrust, then it will of course be useless as any sort of engine.
Em is swirling out of a magnetron but not sure if i'd call it useless.

Big thks to mr B for an excellent summary...well done.

Very surprised at the small size, might show the shape has validity but at reduced performance.

I'm sipping some black and tans...the knife edge fulcrum was test platform, makes me feel good abt my video a few wks ago.

a reputable guy reports results that are not easily dismissed...reason for all interested to lift a glass to him. Prosit, cheers and here's mud in yer eye...good day for theorists, diyers, fans and interested followers...happy Saturday to all at nsf. heres to more progress in the near future.

Offline 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
Aero, your intuition is correct

Even the lowest modes, have a frequency higher than 2.45 GHz:

These are the lowest natural frequencies I calculate for those dimensions:

4.376 GHz "TE111  Cyl"        Q=56,599
4.717 GHz "TM010 Cyl" (*)   Q=24,677

The Q's are based on pure copper and perfect geometry, a copper alloy would have lower Q.


the only way I can see this "EM Drive" having a natural frequency at 2.45 GHz would be because of the huge opening for the waveguide, which should lower the natural frequency.



__________
(*)  the equivalent of TM010 in a cylinder (a degenerate mode since there is no such thing as TM010 in a truncated cone because p cannot be 0 because the fields in a truncated cone longitudinal direction cannot be constant , so this mode should be called something else)
« Last Edit: 07/26/2015 01:26 AM by Rodal »

Offline Rodal

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

Tajmar concludes:


Quote from: Tajmar and Fiedler
The nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far 

This is the most lukewarm kind of support imaginable.  Shawyer is encouraged by this ?  ( http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission  )

Quote from: Wired article The 'impossible' EmDrive could reach Pluto in 18 months
Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results.   

The authors state that they can not confirm or refute the claims of the EMDrive     !!!!!

(page 9 of Tajmar's report)

If the authors themselves conclude that they cannot confirm or deny the EM Drive claims, there is nothing here for John Baez or Sean Carroll to have to respond to.  All that Baez and Carroll have to do is to quote the authors saying that the authors accept that their report is inconclusive !
« Last Edit: 07/26/2015 01:24 AM by Rodal »

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.

Tajmar concludes:


Quote
The nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far 

This is the most lukewarm kind of support imaginable.

The authors state that they can not confirm or refute the claims of the EMDrive     !!!!!

(page 9 of Tajmar's report)

If the authors themselves conclude that they cannot confirm or deny the EM Drive claims, there is nothing here for John Baez or Sean Carroll to have to respond to.  All that Baez and Carroll have to do is to quote the authors saying that the authors accept that their report is inconclusive !
A huge clue to Tajmar's studied ambivalence is the title of his paper, containing as it does the designator "side-effects". His arm would need to twisted a lot harder for him to entitle it "thrust". There are politics involved here too.

Offline rfmwguy

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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
Aero, your intuition is correct

Even the lowest modes, have a frequency higher than 2.45 GHz:

This are the lowest natural frequencies I calculate for those dimensions:

4.376 GHz "TE111  Cyl"        Q=56,599
4.717 GHz "TM010 Cyl" (*)   Q=24,677

The Q's are based on pure copper and perfect geometry, a copper alloy would have lower Q.


the only way I can see this "EM Drive" having a natural frequency at 2.45 GHz would be because of the huge opening for the waveguide, which should lower the natural frequency.



__________
(*)  the equivalent of TM010 in a cylinder (a degenerate mode since there is no such thing as TM010 in a truncated cone because p cannot be 0 because the fields in a truncated cone longitudinal direction cannot be constant , so this mode should be called something else)
Meeper alert - other than frustum size, there is one other variance in design...slit antenna from waveguide launcher.

This is quite different from other tests. wasn't going to link to idiots playing with magnetrons, but below you will see the effects of a polarized output, what happens when you insert a grid or slit.
Effective radiation is reduced significantly. Does an omni pattern provide more radiation? I think yes. Did it affect tajmars experment? Possibly.


Offline 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
Aero, your intuition is correct

Even the lowest modes, have a frequency higher than 2.45 GHz:

This are the lowest natural frequencies I calculate for those dimensions:

4.376 GHz "TE111  Cyl"        Q=56,599
4.717 GHz "TM010 Cyl" (*)   Q=24,677

The Q's are based on pure copper and perfect geometry, a copper alloy would have lower Q.


the only way I can see this "EM Drive" having a natural frequency at 2.45 GHz would be because of the huge opening for the waveguide, which should lower the natural frequency.



__________
(*)  the equivalent of TM010 in a cylinder (a degenerate mode since there is no such thing as TM010 in a truncated cone because p cannot be 0 because the fields in a truncated cone longitudinal direction cannot be constant , so this mode should be called something else)
Meeper alert - other than frustum size, there is one other variance in design...slit antenna from waveguide launcher.

This is quite different from other tests. wasn't going to link to idiots playing with magnetrons, but below you will see the effects of a polarized output, what happens when you insert a grid or slit.
Effective radiation is reduced significantly. Does an omni pattern provide more radiation? I think yes. Did it affect tajmars experment? Possibly.

...

We have to add this new chapter to the strange history of the EM Drive: that the paper states:

Quote
We would like to thank Roger Shawyer for his assistance

and

Quote from: Wired article The 'impossible' EmDrive could reach Pluto in 18 months
Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results.   

when they tested a tiny EM Drive, with a huge waveguide on its side, and a Q=50 .  What kind of assistance did Shawyer provide????

Somehow I get the impression that Shawyer provided more assistance to TheTraveller, or else that TheTraveller followed more closely Shawyer's advice
« Last Edit: 07/26/2015 02:05 AM by Rodal »

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.

Tajmar concludes:


Quote from: Tajmar and Fiedler
The nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far 

This is the most lukewarm kind of support imaginable.  Shawyer is encouraged by this ?  ( http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission  )

Quote from: Wired article The 'impossible' EmDrive could reach Pluto in 18 months
Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results.   

The authors state that they can not confirm or refute the claims of the EMDrive     !!!!!

(page 9 of Tajmar's report)

If the authors themselves conclude that they cannot confirm or deny the EM Drive claims, there is nothing here for John Baez or Sean Carroll to have to respond to.  All that Baez and Carroll have to do is to quote the authors saying that the authors accept that their report is inconclusive !

Considering the fact that tajmar was not able to completely refute his claims. I can see how Shawyer would be encoraged. Think about it this way. Since he went public with his claims most everyone in the scientific community as labelled him a crack pot selling snake oil, or an idiot that doesnt know how to run an experiment. I believe in an earlier segment of this thread a comment was made about not trying hard enough to find your own errors. The fact that his experiment has received this much scrutiny from a NASA lab and now Tajmar's lab and the possibility that this is actually useful thrust has not been completely taken off the table. If I were him I would be encouraged too. Sure this wont win over the hard skeptics, But I think their is pretty much no room left for skeptics claiming that the reason this signal is still being seen is because of something trivial.

Offline rfmwguy

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Well said mr B. I agree with doc, if a reduced size frustum with slit feed was shawyers advice, i'd wonder about the usefulness of it. 2 key attributes were changed and the feed is definitely a big one. Don't think yang fed with slit and know ew didn't.

Yet, there is still something going on.

Seems more + than - considering the variance. Our aachen friends might agree considering the results of their micro frustum @25ghz and mw power levels...3 major variants.

Offline birchoff

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@Rodal or anyone for that matter know how to calculate shawyer's design factor?

In the conclusion Tajmar also said that the thrust measured in the oil damped torsion balance was close to the original predicted thrust if they take into consideration the smaller Q (the value they analyzed and calculated at the end of the oil damped torsion test). Since he states the original prediction of 98.2 micro newtons as if it was calculated using the output power of the magnetron via Shawyer's model. I would like to believe that his statement in the conclusion means they re ran the calculation for the prediction with the new Q value.
« Last Edit: 07/26/2015 02:13 AM by birchoff »

Offline Rodal

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Tajmar et.al.'s observation on the knife-edge balance that may be useful to rfmwgy and SeeShell's experiments:

Quote from: M. Tajmar and G. Fiedler

...The difference between upwards and downwards measurements was 229 μN and therefore close to our expectation of 2x98 μN. The horizontal direction was supposed to be our zero thrust reference, and indeed it was about only 1/3 of the downwards measure...


observations are as follows:

 The balance configuration seems to indeed measure thrust in the correct direction and magnitude as claimed by
Shawyer.

 The horizontal direction was supposed to measure only thermal effects and no thrust. We observed a turn-on
effect (of the same magnitude compared to other thrust directions but with an opposite value) and then an
increase to about 100 μN until the power was turned off. We then saw a behavior that was indeed expected from
a thermal side-effect: The thrust still further increased a bit (delay from thermal shielding) and then went down
to zero.

 The thruster up/down direction showed a very different behavior. They increased to 620 μN and 391 μN
respectively and then remained constant for a much larger time compared to the horizontal direction. A different
orientation of the magnetron (horizontal versus vertical) may have caused different thermal signatures and
therefore buoyancy effects. Still, this behavior was really different and repeatable. In the much lower power
measurements from Brady et al on the torsion balance, we can also see that it took some time after power turnoff that the balance reading went back to zero as if the EMDrive got somehow charged and produced thrust which rather decays contrary to a simple switch off after power is removed.

Our weakest part in this setup was certainly the simple connection of the magnetron with three flexible silicon
isolated wires to the power supply. A current of several Ampere is flowing over those wires which can generate
significant magnetic forces (although we tried to keep the wires close together such that the magnetic effects cancel) that may have influenced our measurements. This together with the buoyancy effect made this measurement setup less convincing compared to a torsion balance setup.

The buoyancy observations match the buoyancy observations of Iulian Berca.

« Last Edit: 07/26/2015 02:42 AM by Rodal »

Offline SeeShells

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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.
Producing a pressure and producing thrust and movement are close but no cigar. I've setup my fulcrum beam to be able to show both by just removing the scales measuring a pressure I have a beam free to swing up or down. I then can compare both sets of data to see if they match or show any abnormalities. I'm going to put a small arm and a weight attached down from the center of the fulcrum to measure acceleration for a given distance.

Offline deltaMass

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I spent a few fine nights and days with Martin Tajmar and Woodward and the gang down at STAIF in Albuquerque.

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