Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1872058 times)

Online sghill

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Seems to me that if the thicknesses of the copper walls are varied, but the other dimensions remain the same, and thrust also differs between the models, then we know the drive is interacting with the outside environment somehow. If thrust does not vary between models of different wall thickness, then the thrust is occurring in-house- so to speak.
Cart before the horse? - if you will excuse me saying so.

To date we do not even have at least two independent laboratories using identical devices producing identical thrust to within experimental tolerances.

That for me is a prerequisite for declaring that there is any thrust at all.

The geometrical dimensions of these two independent devices are identical.
Identical mode shape.
The force/PowerInput not rigorously the same (extreme rigor leads to "rigor mortis") but these two are very comparable [considering that reported Force/InputPower ranges from 0 to 1000 for other researcher tests]:

Description       Mode           Pressure    Length (m) Db (m)      Ds(m)    mN/kW

NASA Eagleworks  TM212      Ambient   0.2286   0.2794   0.15875   3.00

Iulian Berca          TM212       Ambient   0.2286   0.2794   0.1588    2.80


Berca Tests 3 & 3.1 (averaged w/up/down directional effects subtracted as per you, deltaMass -so you can't object to those numbers :)  )

Iulian's Berca Lab is very independent from NASA.

NASA Brady, White, March, Lawrence, and Davies, b

Pretty good agreement between these two (certainly within experimental tolerance).

Iulian Berca did not make noise, but he quietly humbly went about his business, the first independent researcher to produce results and his results (in force/PowerInput) are very close to NASA's.

Thanks Jose,

But do we know the thicknesses of these two drives?  Were they very different in thickness, but achieved approximately the same thrust?  Is the signal to noise even high enough to distinguish (perhaps not yet)?
Bring the thunder Elon!

Offline SeeShells

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Cavity Q refresher: http://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/q-and-bandwidth-resonant-circuit/
Thanks, that was refreshing. Honestly I really needed a the link to some of those old school formulas, helps me stay on base.

Don't get me wrong on thinking that the high Q of the device is important but what I think is as or more important is the tradeoff between a smaller Q and the stored release of that buildup of Q.  I think it has a direct relationship to thrust.

I was looking for a good Q in this design but more importantly a very stable mechanical and small thermal expansion environment.  I know heat can play havoc with a smooth cone shape as the modes through time change warpage in the walls occur leading to a non-stable environment. What drives this thought is this... I built a machine to dice IC wafers. The Z axis was so good you could touch the stainless steel chuck for less than one second and then measure doing a height test. And see expansion from that brief  touch and just from the heat of your finger. It was only a micron or so but that was on a 1 inch thick piece of stainless steel!

I've looked for six sided hexagon horn antennas and found very little info but nothing bad. So I am open to thoughts and ideas. You guys are way smarter than this silly girl.

Shell

Offline aero

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Yes, they are 2-D perfect metal cavities, Ez excitation. I'll make a 3-D run for comparison.

Meep tells me that for the best Q values, the antenna should be place on the axis of rotation. Parallel for Hy (magnetic) excitation and perpendicular for Ez (electric) excitation. The distance from the end is an open question for me but for Ez excitation I've used 1/4 and 1/2 wavelength and don't remember which worked best. For Hy, it seems to depend on the mode I'm trying to excite. Note that I've settled on a dipole antenna, 0.2 wavelengths long for lack of better information. Of course for the Brady antenna, I use 14 mm which is the diameter of the loop antenna he is now using. Unfortunately I don't know how to model a loop antenna in meep, it is not one of the defaults that I can find.
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Offline Rodal

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Thanks Jose,

But do we know the thicknesses of these two drives?  Were they very different in thickness, but achieved approximately the same thrust?  Is the signal to noise even high enough to distinguish (perhaps not yet)?
We know that both drives were built at their homes, using thin copper sheet.  Therefore we know that the thickness of the copper sheet (compared to the geometrical dimensions) is small.  We can also ascertain that any difference in copper sheet thickness between NASA and Iulian is negligible, regarding conical frequency and mode shape, and Q (since we know that the skin depth is much smaller than the copper thickness).

From an examination of the experimental results in the wiki EM Drive table it can be statistically affirmed that Bercan and NASA have statistically similar results (take a look at the range of force/InputPower for different researchers).
« Last Edit: 06/22/2015 05:43 PM by Rodal »

Offline Rodal

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Yes, they are 2-D perfect metal cavities, Ez excitation. I'll make a 3-D run for comparison.

Meep tells me that for the best Q values, the antenna should be place on the axis of rotation. Parallel for Hy (magnetic) excitation and perpendicular for Ez (electric) excitation. The distance from the end is an open question for me but for Ez excitation I've used 1/4 and 1/2 wavelength and don't remember which worked best. For Hy, it seems to depend on the mode I'm trying to excite. Note that I've settled on a dipole antenna, 0.2 wavelengths long for lack of better information. Of course for the Brady antenna, I use 14 mm which is the diameter of the loop antenna he is now using. Unfortunately I don't know how to model a loop antenna in meep, it is not one of the defaults that I can find.

For a 2-D model you MUST place the antenna in the axis of axisymmetry, otherwise you are going to converge to the wrong solution:  a trapezium box, where the boundaries are straight walls perpendicular to the plane.

The interesting thing will be what you may find from the 3D model of a CONE, which has inherent geometrical axi-symmetry.  Will an offset RF feed (as most researchers have, entering one of the side conical walls) lead to an unsymmetric solution?  Or will the axisymmetry of the cone prevail and you will still have a symmetric solution?

Offline SeeShells

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Yes, they are 2-D perfect metal cavities, Ez excitation. I'll make a 3-D run for comparison.

Meep tells me that for the best Q values, the antenna should be place on the axis of rotation. Parallel for Hy (magnetic) excitation and perpendicular for Ez (electric) excitation. The distance from the end is an open question for me but for Ez excitation I've used 1/4 and 1/2 wavelength and don't remember which worked best. For Hy, it seems to depend on the mode I'm trying to excite. Note that I've settled on a dipole antenna, 0.2 wavelengths long for lack of better information. Of course for the Brady antenna, I use 14 mm which is the diameter of the loop antenna he is now using. Unfortunately I don't know how to model a loop antenna in meep, it is not one of the defaults that I can find.

For a 2-D model you MUST place the antenna in the axis of axisymmetry, otherwise you are going to converge to the wrong solution:  a trapezium box, where the boundaries are straight walls perpendicular to the plane.

The interesting thing will be what you may find from the 3D model of a CONE, which has inherent geometrical axi-symmetry.  Will an offset RF feed (as most researchers have, entering one of the side conical walls) lead to an unsymmetric solution?  Or will the axisymmetry of the cone prevail and you will still have a symmetric solution?

This is why you didn't see my placement of the RF feed into the EMDrive and why it's important to make it flexible. It will be very interesting to see Aero's results, I'm so glad he is here and after I tried my hand at Meep I know, it's not easy... at all.

Shell

Offline rfmwguy

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Cavity Q refresher: http://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/q-and-bandwidth-resonant-circuit/
Thanks, that was refreshing. Honestly I really needed a the link to some of those old school formulas, helps me stay on base.

Don't get me wrong on thinking that the high Q of the device is important but what I think is as or more important is the tradeoff between a smaller Q and the stored release of that buildup of Q.  I think it has a direct relationship to thrust.

I was looking for a good Q in this design but more importantly a very stable mechanical and small thermal expansion environment.  I know heat can play havoc with a smooth cone shape as the modes through time change warpage in the walls occur leading to a non-stable environment. What drives this thought is this... I built a machine to dice IC wafers. The Z axis was so good you could touch the stainless steel chuck for less than one second and then measure doing a height test. And see expansion from that brief  touch and just from the heat of your finger. It was only a micron or so but that was on a 1 inch thick piece of stainless steel!

I've looked for six sided hexagon horn antennas and found very little info but nothing bad. So I am open to thoughts and ideas. You guys are way smarter than this silly girl.

Shell

Shell, think you are just fine with a hex cone. Besides, the variety of designs is what makes this appealing. No entity has come out and said they have the only solution that will work. Hex on!

Offline SeeShells

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Time to start my build.

Godspeed John Glenn!

Thanks... oh so much, you just choked me up sghill.

shell

Offline WarpTech

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Time to start my build.

I think I have most of the info to be sure I can get something viable from a first test. Thanks to all of you! You're all Supermen (women too) in my mind!

I'm basing the cavity on Yang's sizes @2.45 Ghz, keeping the Frustum angle shallow like theirs but extending it to only 1 inch in diameter at the small end. I'm allowing the Cavity to be able to be flexible so as to remove and replace the small endplates to test different harmonics and modes while only changing the small endplate. I think Dr. Rodal's ideas mirror my thoughts here (Loved the write up BTW Jose) and the smaller endplates will lead to greater forces being exhibited. The fine tuning is going to be done through a lead screw in the large endplate, which is concave. Note: I've a English wheel and have put a very nice curve into a piece of soft sheet metal just to test if it could be done.

The material is going to be ~ 18 Gauge Perforated Copper sheet. I found some at a surplus metal company but it's a 150 mile RT drive to get it and he said he has others I need to look at also. Just got a 32" sheet metal break to make my bends.

I'm going to use a Microwave Magnetron rated at 800w and 2.45 Ghz as it's cheap and should give me a DC component as well as a broad frequency spread enough to get any forces above the noise level. Important! ... a fine mesh Chicken wire cage to enclose the entire thing as we need WiFi and to keep the FCC happy. ;)

I like being able to get into the cavity to change the Microwave antenna and the endplates plus being able see inside the maelstrom of microwave cavity activity might prove to be a plus.

I have some thoughts on the testing rig and still working those out. I like the fulcrum with the oil damping idea and I'll post a drawing of my thoughts later, but I want to get the Frustum built first.

Shell

Just a thought. At the center of the big end plate, if you cut some radial slots there, maybe 20% of the diameter in length, to prevent circulating current around the axis near the center, that is where a majority of opposing forces are generated. This will prevent those currents, and will probably allow some energy to leak out. This should give "significant" increase in thrust, IMO. Just don't stand behind it. :)


Todd



Offline SeeShells

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Time to start my build.

I think I have most of the info to be sure I can get something viable from a first test. Thanks to all of you! You're all Supermen (women too) in my mind!

I'm basing the cavity on Yang's sizes @2.45 Ghz, keeping the Frustum angle shallow like theirs but extending it to only 1 inch in diameter at the small end. I'm allowing the Cavity to be able to be flexible so as to remove and replace the small endplates to test different harmonics and modes while only changing the small endplate. I think Dr. Rodal's ideas mirror my thoughts here (Loved the write up BTW Jose) and the smaller endplates will lead to greater forces being exhibited. The fine tuning is going to be done through a lead screw in the large endplate, which is concave. Note: I've a English wheel and have put a very nice curve into a piece of soft sheet metal just to test if it could be done.

The material is going to be ~ 18 Gauge Perforated Copper sheet. I found some at a surplus metal company but it's a 150 mile RT drive to get it and he said he has others I need to look at also. Just got a 32" sheet metal break to make my bends.

I'm going to use a Microwave Magnetron rated at 800w and 2.45 Ghz as it's cheap and should give me a DC component as well as a broad frequency spread enough to get any forces above the noise level. Important! ... a fine mesh Chicken wire cage to enclose the entire thing as we need WiFi and to keep the FCC happy. ;)

I like being able to get into the cavity to change the Microwave antenna and the endplates plus being able see inside the maelstrom of microwave cavity activity might prove to be a plus.

I have some thoughts on the testing rig and still working those out. I like the fulcrum with the oil damping idea and I'll post a drawing of my thoughts later, but I want to get the Frustum built first.

Shell

Just a thought. At the center of the big end plate, if you cut some radial slots there, maybe 20% of the diameter in length, to prevent circulating current around the axis near the center, that is where a majority of opposing forces are generated. This will prevent those currents, and will probably allow some energy to leak out. This should give "significant" increase in thrust, IMO. Just don't stand behind it. :)


Todd
Good idea! I like how you think. That goes into the "to do" #1 pile! Thanks!

I'm open to different ideas if someone has a pet thought that I can put into testing, I am trying to be like the Drive... flexible.

Shell

Offline WarpTech

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@ Dr. Rodal -

Attached are images of the Brady cavity and the Rodal cavity showing antenna location. Are you sure you want to place the antenna where EW had theirs placed? Before you answer that, take a look at the field patterns here:

Brady_corner_ant
https://drive.google.com/folderview?id=0B1XizxEfB23tfjBKSFF2dFp4WVV2MEZzNUtOU3NmdTZrQWd0dVo4WFIxcll0NDZEUjFXeEk&usp=sharing

and here:
Rodal_corner_ant
https://drive.google.com/folderview?id=0B1XizxEfB23tfjkxdTdaWjdxMmdLZ0syUktiaU9hSklYQmFGbzdkZGVtc09GRFB4ZzJTZ1k&usp=sharing

Add: Anyone interested in the EM thruster, feel free to check them out. -aero

Based on what I've calculated, and what Shawyer says, the antenna should be located at the diameter where it is Sqrt(2) x cutoff diameter. So, if you know the diameter at the cutoff frequency, then the antenna should be located at 1.414X that diameter.

The reason is, at this diameter the free-space frequency matches the guide frequency, so the impedance should be matched at this location.

(1/2)/sqrt(1 - 1/2) =1/sqrt(2)

Todd

Offline ZuluMoon99

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Cavity Q refresher: http://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/q-and-bandwidth-resonant-circuit/
Thanks, that was refreshing. Honestly I really needed a the link to some of those old school formulas, helps me stay on base.

Don't get me wrong on thinking that the high Q of the device is important but what I think is as or more important is the tradeoff between a smaller Q and the stored release of that buildup of Q.  I think it has a direct relationship to thrust.

I was looking for a good Q in this design but more importantly a very stable mechanical and small thermal expansion environment.  I know heat can play havoc with a smooth cone shape as the modes through time change warpage in the walls occur leading to a non-stable environment. What drives this thought is this... I built a machine to dice IC wafers. The Z axis was so good you could touch the stainless steel chuck for less than one second and then measure doing a height test. And see expansion from that brief  touch and just from the heat of your finger. It was only a micron or so but that was on a 1 inch thick piece of stainless steel!

I've looked for six sided hexagon horn antennas and found very little info but nothing bad. So I am open to thoughts and ideas. You guys are way smarter than this silly girl.

Shell

Not sure if this will be of use Shell but if you look at :

http://www.ece.rutgers.edu/~orfanidi/ewa/ch19.pdf

You will find details on the calcs for Aperture Antenna radiation

The Maths is way over my head but maybe you and others might find it of use.

Offline aceshigh

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did a search and did not find this... hope it was not posted yet


Quote
AIAA Propulsion and Energy Forum and Exposition
27–29 July 2015
Hilton Orlando, Orlando, Florida
...
TUESDAY, JULY 28, 2015
NFF-04. Future Flight Propulsion Systems
Chair(s): Gregory Meholic (The Aerospace Corporation)
Co-Chair(s): Heidi Fearn (California State University, Fullerton)
2:30 PM - 5:30 PM; Lake Nona A
...
3:30 PM - 4:00 PM
Design and First Measurements of a Superconducting Gravity-Impulse-Generator
Istvan Lörincz; Martin Tajmar

4:00 PM - 4:30 PM
Replication and Experimental Characterization of the Wallace Dynamic Force Field Generator
Martin Tajmar

4:30 PM - 5:00 PM
New Theoretical Results for the Mach Effect Thruster
Heidi Fearn

5:00 PM - 5:30 PM
Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects
Martin Tajmar


I wonder if someone from this thread could attend the conference and if there is a following Q/A, even mention some of the experiments discussed here, ask questions, etc.
« Last Edit: 06/22/2015 07:45 PM by aceshigh »

Offline Rodal

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5:00 PM - 5:30 PM
Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects
Martin Tajmar


I wonder if someone from this thread could attend the conference and if there is a following Q/A, even mention some of the experiments discussed here, ask questions, etc.

Martin Tajmar is the same guy who has claimed  to have measured a gravitomagnetic version of the frame-dragging effect caused by a superconductor with an accelerating or decelerating spin, that nobody else, to my knowledge has observed independently (actually hasn't it been falsified ?).  Now, he is going to present results on the EM Drive, and moreover on side effects ?

Didn't Tajmar suggest gravity-EM coupling billions of times stronger than predicted by General Relativity, but his own experiments showed a much smaller effect than what he was predicting?.

If I recall correctly he later  attributed his results to air currents caused by his cryo-coolant sublimating and retracted his paper.

Wasn't Tajmar's general design also used by Ning Li and Podkletnov ? with different details of cooling and method of obtaining rotation and materials for the disks?. 

Now Tajmar is going to present results on the EM Drive ? The story of the EM Drive gets stranger all the time...
« Last Edit: 06/22/2015 08:41 PM by Rodal »

Offline tchernik

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5:00 PM - 5:30 PM
Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects
Martin Tajmar


I wonder if someone from this thread could attend the conference and if there is a following Q/A, even mention some of the experiments discussed here, ask questions, etc.

Martin Tajmar is the same guy who has claimed  to have measured a gravitomagnetic version of the frame-dragging effect caused by a superconductor with an accelerating or decelerating spin, that nobody else, to my knowledge has observed independently (actually hasn't it been falsified ?).  Now, he is going to present results on the EM Drive, and moreover on side effects ?

The story of the EM Drive gets stranger all the time...


I understand he recanted his own results, admitting they were probably due to measurement error (the dreaded atmospheric/thermal effects).

Edit: the article below goes into much more details. Personally, I think it speaks leagues about this guy's integrity that he actually made a paper to recant himself. Quite a rare sight.

http://lanl.arxiv.org/ftp/arxiv/papers/0806/0806.2271.pdf
« Last Edit: 06/22/2015 08:39 PM by tchernik »

Offline deltaMass

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Heidi Fearn is Woodward's collaborator.

It is noteworthy that she's reporting on theoretical developments rather than on experimental progress.
« Last Edit: 06/22/2015 08:37 PM by deltaMass »

Offline graybeardsyseng

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Cavity Q refresher: http://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/q-and-bandwidth-resonant-circuit/

Excellent Link!! Thanks.

Have you developed an approach for measuring Q in you DUT?    I tend to think in of "Q as Ctr Freq/3dB  Bandwidth" from the filter world as well and have been pondering this.  VNA? 

BTW - thanks for the earlier welcome and yes I am (mostly) an old RF guy.

Herman

EMdrive - finally - microwaves are good for something other than heating ramen noodles and leftover pizza ;-)

Offline graybeardsyseng

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Cavity Q refresher: http://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/q-and-bandwidth-resonant-circuit/
Thanks, that was refreshing. Honestly I really needed a the link to some of those old school formulas, helps me stay on base.

Don't get me wrong on thinking that the high Q of the device is important but what I think is as or more important is the tradeoff between a smaller Q and the stored release of that buildup of Q.  I think it has a direct relationship to thrust.

I was looking for a good Q in this design but more importantly a very stable mechanical and small thermal expansion environment.  I know heat can play havoc with a smooth cone shape as the modes through time change warpage in the walls occur leading to a non-stable environment. What drives this thought is this... I built a machine to dice IC wafers. The Z axis was so good you could touch the stainless steel chuck for less than one second and then measure doing a height test. And see expansion from that brief  touch and just from the heat of your finger. It was only a micron or so but that was on a 1 inch thick piece of stainless steel!

I've looked for six sided hexagon horn antennas and found very little info but nothing bad. So I am open to thoughts and ideas. You guys are way smarter than this silly girl.

Shell

Shell -
From a short discussion with some waveguide colleagues I get the impression that hexagonal should work pretty well - I didn't go into what I was asking for, just discussions of circular vs rectangular vs hexagonal wg.   mode calculations are somewhat different of course but hex or octagonal etc are just closer approximations to circular (insert spherical chicken in a vacuum joke here). 

I think matching the horn geometry to frustum geometry is likely a good idea but thats just because it "feels right".   I will try playing with it tonight if I can.

Love all the different experimental setups - the more the merrier.   

Herman
EMdrive - finally - microwaves are good for something other than heating ramen noodles and leftover pizza ;-)

Offline aero

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Ok - here is what the Brady cavity looks like in 3D. x, y, and z views. The y view looks pretty good as it should because that is the symetric view of both cavity and antenna. The end view and the other side view, not so much as the antenna is not symetric with those view directions.
Retired, working interesting problems

Offline kml

I have started conducting tests on my linear EmDrive.   The test assembly is fully untethered using a battery power source and IR remote control for RF on/off.  Forces are measured using an AND MC-10K 10.1kg x 0.001g scale.   The initial tests are using a 4"x3"x0.25" Al2O3 ceramic dielectric.  During tests the scale and unit are enclosed within a cardboard breeze break.    The rectangular non-tapered resonator internal dimensions are 6.5"x3.25"x13", mode TE102.  "Up Orientation" means the fixed end with the feedpoint and the dielectric plate is on top, the adjustable end is on bottom closest to the scale.   In all orientations the RF PA, battery, and sample port heat sink are on top of the unit, furthest from the scale.

The initial tests with dielectric were promising, with forces very close to the 15mg predicted:

http://kl.net/emdrive/20150621-test-9-al2o3-up.png


Unfortunately, I also saw similar forces in most of the control experiments, such as with no dielectric installed:

http://kl.net/emdrive/20150621-test-32-no-dielectric-up.png


And even with the unit suspended by a wood stand just above the scale (to prevent contact), with ceramic flooring tiles placed on the scale tray for similar loading:
http://kl.net/emdrive/20150621-test-33-no-dielectric-up-suspended-tiles.png


Only the dummy load test did I not see any change in scale output.   The output of the isolator is directly connected to the dummy load that normally takes the output of the sampling port, thus bypassing the RF cavity:

http://kl.net/emdrive/20150621-test-36-no-dielectric-dummy-load.png


Most likely there is an RFI problem with the scale.  I'm going to attempt to shield the scale with the unit suspended above it to prove that it is RFI.
« Last Edit: 06/22/2015 10:38 PM by kml »

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