Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1800953 times)

Offline DrBagelBites

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@rfmwguy

Chatted up some of the companies at the conference, asked the ones in R&D about any sort of electromagnetic engines/propulsions they may be working on. No dice. Most or all are researching hall thrusters/ion propulsion/etc.
...

That isn't surprising.

Yeah, I know. And even if they did, I don't think they'd leak it at a conference where it would spread like wildfire.

Offline deltaMass

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The Chinese are very quick to capitalise on new stuff. They also have someone who claims to have the best performance figure ever recorded for a frustum.

And yet...

Offline mittelhauser

The device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al.  It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...

Yes I agree it is very the Experimental EMDrive except Shawyer got 16mNs out of his.

It took him several years to get it right. Q was 5,900 but that was because it had a dielectric inside. He used 5 magnetrons, burnt out 3 and burned a hole in a waveguide. But he got there.

His experimental data was verified by a expert Uk aerospace industry group set up by the UK gov Dept of Defense. After the experts gave him the thumbs up, the UK gov gave him the 1st grant to build the Demonstrator EMDrive and the rotary test rig.

After the UK gov again verified the data from the Demonstrator trials he got the final payment from the UK gov.

Sigh.  I'll try one more time.  You keep making these statements over and over.  However, you have provided no evidence to support those statements.  Who were the experts who "verified" it?  Where is a document which shows what was verified?  Etc, etc.  You promised us a paper which would end all doubts and all that was produced was an old paper which didn't have any new experimental data. 

I *really* want to be a believer and you make it extremely difficult.   I'll say once again, stop posting blindly optimistic projections and focus on your build and get some data which can be independently verified and which shows what you claim...Please!  I'm wishing you luck.

Frankly, if this had been truly verified at the levels you imply, funding wouldn't be an issue and folks wouldn't be scrambling to do FundMe's for DIY versions.  I sit within 50 miles of a LOT of people who would happily throw millions at the project if there was evidence such as you keep insisting already exists.



Offline deltaMass

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TheTraveller does not think that EmDrive violates conservation of momentum.  So good luck on presenting him with a reasoned argument. He is a closed book.

Offline rfmwguy

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thks for update dr bb...if they answered quickly and didn't ask u what it was it may indicate they know abt it. that might be a good first question. ..have u heard abt. 

also agree we must avoid third-party advocacy posts...unscientific and not useful

Offline cee

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It's quite possible there wasn't a iris  given the low Q reported. You probably wouldn't see it anyway   A thin sheet of copper with a slot in it between the WR 340 waveguide flange attached to the frustum and the WR 340 to WR 430 transition wave guide and WR 430 the Magnetron was coupled to.

Offline cej

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Actually, I forgot that Tajmar had a screw-driven reduction in length.  The length given must be the external length, the maximum length possible.
...
There is an uncertainty from these two factors:

1) We don't quite know the internal length with the screw-modified length
...

I think the length/height is exactly what Tajmar claims it is -- 68.6 mm:

Quote from: M. Tajmar
A much larger resonance peak appeared above 3 GHz, but as we did not have a variable frequency microwave source we had to stick to Q ≈ 50. As our magnetron had an output power of 700 W, we expected a thrust of 98.2 μN according to Shawyer’s models. This was much higher than the resolution of our measurement equipment (< 0.1 μN) and we therefore decided to go ahead with testing and explore this low Q factor regime.  After all adjustments, epoxy adhesive was used to fix the EMDrive’s top part on the cavity.  Afterwards, some vibration testing was done and the Q factor measurement repeated to be sure that it does not change after extensive testing.

Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.

Offline DrBagelBites

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thks for update dr bb...if they answered quickly and didn't ask u what it was it may indicate they know abt it. that might be a good first question. ..have u heard abt. 

also agree we must avoid third-party advocacy posts...unscientific and not useful

They fully acknowledged what I was asking about and most knew NASA was doing some tests. No quick answers, or maybe they were very deliberate. In any case, if they truly aren't researching it, I don't know. But that is what I got from them.

-I

Offline cee

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Sir,
Could you ask the question of Tajmar whether a slotted resonant iris was used between the WR 340 and WR 340 430 Transition Waveguide flanges for impedance matching purposes in his test setup.

Offline DrBagelBites

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Sir,
Could you ask the question of Tajmar whether a slotted resonant iris was used between the WR 340 and WR 340 430 Transition Waveguide flanges for impedance matching purposes in his test setup.

If I have the time. Can't make any guarantees.

-I

Edit: I think you were talking to me. Let me know if you weren't.
« Last Edit: 07/27/2015 05:59 PM by DrBagelBites »

Online Rodal

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Actually, I forgot that Tajmar had a screw-driven reduction in length.  The length given must be the external length, the maximum length possible.
...
There is an uncertainty from these two factors:

1) We don't quite know the internal length with the screw-modified length
...

I think the length/height is exactly what Tajmar claims it is -- 68.6 mm:

Quote from: M. Tajmar
A much larger resonance peak appeared above 3 GHz, but as we did not have a variable frequency microwave source we had to stick to Q ≈ 50. As our magnetron had an output power of 700 W, we expected a thrust of 98.2 μN according to Shawyer’s models. This was much higher than the resolution of our measurement equipment (< 0.1 μN) and we therefore decided to go ahead with testing and explore this low Q factor regime.  After all adjustments, epoxy adhesive was used to fix the EMDrive’s top part on the cavity.  Afterwards, some vibration testing was done and the Q factor measurement repeated to be sure that it does not change after extensive testing.

Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.

I think that X-Ray, TheTraveller, Todd "WarpTech" got this right.  The dimensions are off by a factor of 2. 

Tajmar et.al. explicitly state that the top part was adjustable for length (page 3 of their report):

Quote
We iterated our design several times by consulting with R. Shawyer to be as representative as possible. Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor.
bold added for emphasis

Besides the fact that they explicitly write that the length was adjustable, one can see the length-adjusting frame on Figures 2b and 2c or their report.

Figure 2a (COMSOL FEA plot) shows that the adjusted length was not longer than the big diameter.

Finally, calculation shows that to resonate at 2.45 GHz, the dimensions had to be off by a factor of 2 and that the adjusted internal length was significantly smaller than the exterior full length.

In your statement:
Quote
Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.

You are confusing "dynamic adjustment" with plain adjustment.  I never claimed that there was dynamic adjustment.  Rather, that they adjusted the internal length to get the cavity in resonance for TE111, prior to force measurements.  This does NOT require any dynamic adjustment, this can be done at the outset, as they did.
« Last Edit: 07/27/2015 06:25 PM by Rodal »

Online Rodal

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I show the calculated TE111 Electric Field in theta polar direction for Tajmar's TU Dresden University EM Drive, to compare it with his COMSOL FEA calculation

Assumed dimensions:


Big diameter = 0.1062 m = (2*0.0541m - 0.002 m)
Small diameter = 0.075 m = (2*0.0385 m - 0.002 m)
Axial Length = 0.100842 m =  0.735*2*0.0686 m

As per TheTraveller I have subtracted 2 mm for copper thickness from the external dimensions, however this has a negligible influence on the results

The axial internal length is 73.5% of the exterior length (it is adjusted internally with a screw prior to testing)

TE111 Natural frequency = 2.446 GHz

I enclose strictly for discussion, research and illustration purposes Fig. 2 a of Tajmar et.al. COMSOL FEA analysis for comparison with my calculations


 “…for purposes such as criticism, comment, news reporting, scholarship, or research…” under US Fair Use

http://fairuse.stanford.edu/overview/fair-use/what-is-fair-use/

This is the  American Institute of Aeronautics and Astronautics link to Martin Tajmar's et.al. paper, that should be obtained from the American Institute of Aeronautics and Astronautics:

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
« Last Edit: 07/27/2015 06:22 PM by Rodal »

Offline X_RaY

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Actually, I forgot that Tajmar had a screw-driven reduction in length.  The length given must be the external length, the maximum length possible.
...
There is an uncertainty from these two factors:

1) We don't quite know the internal length with the screw-modified length
...

I think the length/height is exactly what Tajmar claims it is -- 68.6 mm:

Quote from: M. Tajmar
A much larger resonance peak appeared above 3 GHz, but as we did not have a variable frequency microwave source we had to stick to Q ≈ 50. As our magnetron had an output power of 700 W, we expected a thrust of 98.2 μN according to Shawyer’s models. This was much higher than the resolution of our measurement equipment (< 0.1 μN) and we therefore decided to go ahead with testing and explore this low Q factor regime.  After all adjustments, epoxy adhesive was used to fix the EMDrive’s top part on the cavity.  Afterwards, some vibration testing was done and the Q factor measurement repeated to be sure that it does not change after extensive testing.

Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.

I think that X-Ray, TheTraveller, Todd "WarpTech" got this right.  The dimensions are off by a factor of 2. 

Tajmar et.al. explicitly state that the top part was adjustable for length (page 3 of their report):

Quote
We iterated our design several times by consulting with R. Shawyer to be as representative as possible. Our final tapered cavity design had a top diameter of 38.5 mm, a bottom diameter of 54.1 mm and a height of 68.6 mm as well as a side entrance for the microwaves as shown in Fig. 2. The cavity was made out of three copper pieces where the lower and middle part as well as the side flange were hard soldered using silver and the top part was able to adapt its position in order to optimize for a high Q factor.
bold added for emphasis

Besides the fact that they explicitly write that the length was adjustable, one can see the length-adjusting frame on Figures 2b and 2c or their report.

Figure 2a (COMSOL FEA plot) shows that the adjusted length was smaller than the big diameter.

Finally, calculation shows that to resonate at 2.45 GHz, the dimensions had to be off by a factor of 2 and that the adjusted internal length was significantly smaller than the exterior full length.

In your statement:
Quote
Although Shawyer sometimes uses a dynamically adjusted length to maintain a high Q, Tajmar seems to have fixed it at the outset. Which is smart because the point here is to validate, not optimize. I hope that anyone attempting to use a dynamic length in their experiments will record the parameter and graph it alongside their thrust and heat measurements.

You are confusing "dynamic adjustment" with plain adjustment.  I never claimed that there was dynamic adjustment.  Rather, that they adjusted the internal length to get the cavity in resonance for TE111, prior to force measurements.  This does NOT require any dynamic adjustment, this can be done at the outset, as they did.
There is only one other option to get resonance in that setup.
It is possible that they saw is a resonance peak caused by an oscillation between the endplate of the rectangular waveguide and the cavity, but the Comsol picture does not imply that.

Offline cee

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Lower the power of the magnetron and stabilize the output so less is lost in spurious non-Q effects and one last thought I've had is modifying a fanless CPU cooler to keep the magnetron cooler.
http://www.acousticpc.com/images/a_nofan_cr-95c_copper_fanless_cpu_cooler.jpg
I'm still thinking about this one.

Shell

Yes. Every DIYer planning to use a magnetron should look at the already discussed paper "The Magnetron - A Low noise, Long Life Amplifier" (also attached to this message).

To summarize here (I try to advertise the content of the paper for those who would still not have read it) the tricks to transform a noisy magnetron into a cleaner RF amp is to add a feedback mechanism limiting the temperature and thus emission of the cathode in a more subtle way and control over the anode current. To do this you need to:

- Add a switch to disconnect the included lower-end DC power supply off the magnetron, whose sole purpose was to continuously heat the cathode filament, after the tube has started. So after heating has started, let the cathode be heated by back bombardment power alone.

- Use an external, well filtered DC power supply to run the magnetron as a reflection amplifier also more specifically known as a directional amplifier, where the drive power injected through a ferrite circulator becomes indistinguishable from the power reflected by a mismatched load.

- In such a configuration, there is a phase difference between input and output which also limits the gain, because the free running frequency of the driver is not tuned. Forcing the magnetron to operate at the same frequency as the driver can be done by using the natural magnetron's frequency dependence upon the anode current which is called magnetron pushing, or conversely the reactive component of load (magnetron pulling). The former is used more often.

- Add a little solenoid called a buck-boost coil in the magnetic circuit, to control the anode current which changes the free running frequency of the magnetron, into a phase locked amp. The coil creates a magnetic field which increases or reduces the operating voltage, hence the anode current intercept of the load line with a fixed voltage power supply. The coil is ran with low power (< 5 W) from an op-amp that amplifies the phase error signal.



- How to acquire noise data and add a feedback control loop is detailed in the paper so I won't rewrite it there. All you need to know is with that basic tuning the author decreased the noise in a frequency band of 300 kHz at 10 MHz from the carrier by more than 100 dB below the carrier level over a broad range of operating voltage, magnetic field, load and gain. With only 0.6 W drive, the gain was 30 dB at 560 W output. Noise at 10 kHz from the carrier can also be decreased in an even finer way.

This way you obtain a high-gain, phase-locked, long-life, low noise microwave amplifier from a very cheap commercial oven magnetron.
Excellent paper, didn't realize such a small coil could effectively change the operating frequency.

Offline flux_capacitor

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Dr. Rodal, doesn't Tajmar's COMSOL image show a flat upper small end plate, but a… conical bottom big end, about 90° from the side wall?
« Last Edit: 07/27/2015 06:54 PM by flux_capacitor »

Offline cee

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Sir,
Could you ask the question of Tajmar whether a slotted resonant iris was used between the WR 340 and WR 340 430 Transition Waveguide flanges for impedance matching purposes in his test setup.

If I have the time. Can't make any guarantees.

-I

Edit: I think you were talking to me. Let me know if you weren't.
Yes I was asking you dr bb, still new to this format. Appreciate your time.

Offline DrBagelBites

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Yes I was asking you dr bb, still new to this format. Appreciate your time.

No problem! Welcome to the forum. :)

Offline cee

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I show the calculated TE111 Electric Field in theta polar direction for Tajmar's TU Dresden University EM Drive, to compare it with his COMSOL FEA calculation

Assumed dimensions:


Big diameter = 0.1062 m = (2*0.0541m - 0.002 m)
Small diameter = 0.075 m = (2*0.0385 m - 0.002 m)
Axial Length = 0.100842 m =  0.735*2*0.0686 m

As per TheTraveller I have subtracted 2 mm for copper thickness from the external dimensions, however this has a negligible influence on the results

The axial internal length is 73.5% of the exterior length (it is adjusted internally with a screw prior to testing)

TE111 Natural frequency = 2.446 GHz

I enclose strictly for discussion, research and illustration purposes Fig. 2 a of Tajmar et.al. COMSOL FEA analysis for comparison with my calculations


 “…for purposes such as criticism, comment, news reporting, scholarship, or research…” under US Fair Use

http://fairuse.stanford.edu/overview/fair-use/what-is-fair-use/

This is the  American Institute of Aeronautics and Astronautics link to Martin Tajmar's et.al. paper, that should be obtained from the American Institute of Aeronautics and Astronautics:

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
Dr. Rodal,
I just wanted to confirm the comsol jpeg rectangular to frustum transition. Yang and others have cut a rectangular slot in the frustrum sidewall and attached the rectangular waveguide. The comsol drawing shows the rectangular waveguide with a conical radial sector cutout, strange configuration, am I viewing that correctly ? A top view of the test setup would confirm that.

Online Rodal

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...
Dr. Rodal,
I just wanted to confirm the comsol jpeg rectangular to frustum transition. Yang and others have cut a rectangular slot in the frustrum sidewall and attached the rectangular waveguide. The comsol drawing shows the rectangular waveguide with a conical radial sector cutout, strange configuration, am I viewing that correctly ? A top view of the test setup would confirm that.

I would take Tajmar et.al.' COMSOL Finite Element Analysis most seriously and as representative of the best technical information available for engineering purposes:  nobody would dedicate the very expensive time (not just the computer time but the much more expensive time of an analyst that has expertise in Finite Element Analysis) without careful attention to the engineering details.   The COMSOL analysis must show how things were in reality, as it is in their interest to model reality.

Concerning Tajmar's EM Drive design being "strange" please notice that Tajmar writes how he went out of his way to consult with Roger Shawyer, not just once, buy many times through several iterations to get Roger Shawyer's approval for what he tested:

Quote from: Tajmar et.al.
We iterated our design several times by consulting with R. Shawyer to be as representative as possible. 

Tajmar implies that Roger Shawyer approved of the tested design as being representative.
« Last Edit: 07/27/2015 06:56 PM by Rodal »

Offline SeeShells

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The device used by Tajmar looks more like a version of Shawyer's first fustrum than the latest work by Yang, et al.  It would be very nice if we could get actual schematics of Tajmar's fustrum rather than squinting at pictures trying to figure out what he did...

Yes I agree it is very the Experimental EMDrive except Shawyer got 16mNs out of his.

It took him several years to get it right. Q was 5,900 but that was because it had a dielectric inside. He used 5 magnetrons, burnt out 3 and burned a hole in a waveguide. But he got there.

His experimental data was verified by a expert Uk aerospace industry group set up by the UK gov Dept of Defense. After the experts gave him the thumbs up, the UK gov gave him the 1st grant to build the Demonstrator EMDrive and the rotary test rig.

After the UK gov again verified the data from the Demonstrator trials he got the final payment from the UK gov.

Sigh.  I'll try one more time.  You keep making these statements over and over.  However, you have provided no evidence to support those statements.  Who were the experts who "verified" it?  Where is a document which shows what was verified?  Etc, etc.  You promised us a paper which would end all doubts and all that was produced was an old paper which didn't have any new experimental data. 

I *really* want to be a believer and you make it extremely difficult.   I'll say once again, stop posting blindly optimistic projections and focus on your build and get some data which can be independently verified and which shows what you claim...Please!  I'm wishing you luck.

Frankly, if this had been truly verified at the levels you imply, funding wouldn't be an issue and folks wouldn't be scrambling to do FundMe's for DIY versions.  I sit within 50 miles of a LOT of people who would happily throw millions at the project if there was evidence such as you keep insisting already exists.
Here is a builder who isn't either way, I'm an engineer who can be optimistic, but in the end I rely on data. I've seen some proof in NASA's EagleWorks and in the current tests which are verified. The Chinese could be questioned if you want.

There are many things that could lead to aberrations in thrust, I'll agree in that point, but what's interesting, each test is a little different with different jigs to test, different power, different cavities, different sizes, in vacuum or not and the list is quite extensive.

The few things in all of those that have reported thrust (verified or not) is that have is they injected microwaves into a resonate conical enclosed cavity and thrust was measured. I have looked for the common ingredient other than those I just listed and there doesn't seem to be one at all.  I'm not alone, as there are very sharp skeptics picking it apart.

It's good enough for me to take what little I got from gofundme and my own pocket and pick apart this bit by bit test by test to get to a truth in why this simple device has confounded some of the finest minds around. Answers are not going to take millions but a well designed tests could for a few thousand. When I'm over and done and have solid answers and maybe the key, I'll share it. So if you or one of your friends within that 50 mile radius want to put a couple bucks to help not to make more millions but because they choose to dream, I'll welcome it.

Shell

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