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#1760 by Rodal on 16 Jan, 2016 02:36
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Dr. Rodal and others -
Attached find my attempt, with SeeShell's guidance, to model the geometry of Tajmar's frustum. I have labelled the sections so that we can identify them for discussion.
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Since you brought up Tajmar, and I was just re-reading that paper a couple days ago, do you actually think / believe that he was truly getting any abnormal thrust? Why?
IMHO, his conclusions and reasoning are on par with Shawyer, where Shawyer at least gets a discount as a promoter / inventor / (or a great troll). Tajmar in turn is supposed to be an unbiased critical thinker... yet he follows the same flawed logic of "here's a difference in some thermal force... it must be thrust... now try this in vacuum... the thermal force is gone completely along with its difference which used to be our thrust... this does not teach us anything though because now there is some other force observed which is also different, and so the difference must again be thrust as we just can't think of anything else".
I think that the point of modeling Tajmar's experiment is to independently and objectively assess what is claimed in his paper, precisely for the reasons you point out: instead of taking for granted what he writes and concludes, to understand what were the electromagnetic fields, resonant mode shape, quality factor (why was the Q so low, did he have a lousy coupling factor, ... ?) etc., in his experiment. How strange to perform a test, under advice from Roger Shawyer on a miniature EM Drive with a huge waveguide entering from one side asymmetrically. What were they thinking?
And to perhaps learn from his experiment and how does it relate to other EM Drive experiments.
I think that Tajmar's findings are extremely weak, and rather than make people "believe" in the reality of "thrust" , in his own words:
Bold added for emphasis:QuoteOur test campaign can not confirm or refute in any way the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far. We did find a number of side-effects in the previous setups that indeed can produce large false signals. More work is needed to assess other error sources and the source of the signals that we have observed. Next steps include better magnetic shielding, further vacuum tests and improved EMDrive models with higher Q factors and electronics that allow tuning for optimal operation. We believe that this is a good education project to track down measurement errors and as a worst case we may find how to effectively shield thrust balances from magnetic fields
Concluding that "We believe that this is a good education project to track down measurement errors and as a worst case we may find how to effectively shield thrust balances from magnetic fields" says it all
He seems to be implying that the EM Drive is a study in "side effects" and "false signals" and he does state that he cannot confirm or refute any of the claims by Roger Shawyer for the EM Drive, who is furthermore listed as an assistant to the project !QuoteAcknowledgement
We would like to thank Roger Shawyer for his assistance
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#1761 by rfmwguy on 16 Jan, 2016 02:37
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Just received the following communication from Australia. I believe he could use some emdrive design help. See attachment for his contact info:
"Dave,
just a note to thank you for your report dated 10/2015 describing your thruster experiments. I am attempting to produce the effect using a 60GHz diode resonator but lack the experience required to design the waveguide and signal insertion.
Please let me know if anyone is interested in recommending design ideas.
Meantime, good luck with further experiments. What a useful method of propulsion this could be.
Yours John Newell..
N.B: An attempt to explain the mechanism of action is attached"
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#1762 by Tellmeagain on 16 Jan, 2016 03:12
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Since you brought up Tajmar, and I was just re-reading that paper a couple days ago, do you actually think / believe that he was truly getting any abnormal thrust? Why?
IMHO, his conclusions and reasoning are on par with Shawyer, where Shawyer at least gets a discount as a promoter / inventor / (or a great troll). Tajmar in turn is supposed to be an unbiased critical thinker... yet he follows the same flawed logic of "here's a difference in some thermal force... it must be thrust... now try this in vacuum... the thermal force is gone completely along with its difference which used to be our thrust... this does not teach us anything though because now there is some other force observed which is also different, and so the difference must again be thrust as we just can't think of anything else".
Tajmar's thrust in vacuum may just be Lorentz force. His experiment suffered from the same problem as with zellerium's experiment (Cal Poly). See my post to get the idea what they missed, http://forum.nasaspaceflight.com/index.php?topic=39004.msg1475977#msg1475977 -
#1763 by SteveD on 16 Jan, 2016 04:16
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Here’s to successfully modified frustum which now happily resonates at 2,331 MHz. I removed 8 mm from the small end, resulting in a shorter central length and a bigger diameter of the small end, thus pushing the small end cut-off frequency further down and away from resonance. New cut-off freq is 2,256 MHz which is 75 MHz below test frequency.
These resonance cavities turn out to be remarkably predictable. Simulating new dimensions (in COMSOL) was showing a freq shift of +20 Mhz (2323 MHz-> 2343 Mhz). Actual as-measured freq moved by +19 MHz (2312 MHz->2331 Mhz). 80(?) years-old technologies rule.
New dimensions:
D_big: 264 mm (as before)
D_small: 162 mm (+4 mm)
L_center: 196 mm (-8 mm)
TE012 freq (MHz): Simulated: 2343, Actual: 2331.
Df: 0.69
Small end cut-off: 2,256 MHz.
Q factor (at -3 dB S11): 2300 (went down from the original 3100, not sure if this is due to coupling mismatch under new dimensions, or oxidation from minor torch work, or just aging since the last time it was measured).
If anyone knows why this frustum should not be producing thrust then speak now or forever hold your peace.
Ladies and Gentleman, you can now make your bets. (I have already simulated mode frequency shifts for difference thicknesses of HDPE disks at the small end, so this gives a good hint as to what my own prediction for this upcoming test is…)
0.0019 Newtons (1900 uN). Looking forward to seeing your results.
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#1764 by HarlanGraves on 16 Jan, 2016 04:21
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I had an idea like this in 2014, which involved magnetic's being used in front of the spacecraft to drag it forward continuously and repeatedly, repeat the process. Thus adding more speed to the craft continuously as time and space is covered. I just don't see how this cannot work, it is in fact very possible. In theory it may be possible to accelerate close to or even past the speed of light unmanned. If a powerful magnet is in front of the spacecraft would it not drag, hence propel the rest of the craft forward using magnets from both ends? Somewhat like being dragged towards a gravitational pull, but a magnet instead. The craft would never slow down until reverse propulsion is used.
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#1765 by SteveD on 16 Jan, 2016 04:40
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@rfmwguy: what material did you finally decided on. I heard something about brass, but then you were talking about copper spinning.
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#1766 by RFPlumber on 16 Jan, 2016 04:42
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I had an idea like this in 2014, which involved magnetic's being used in front of the spacecraft to drag it forward continuously and repeatedly, repeat the process. Thus adding more speed to the craft continuously as time and space is covered. I just don't see how this cannot work, it is in fact very possible. In theory it may be possible to accelerate close to or even past the speed of light unmanned. If a powerful magnet is in front of the spacecraft would it not drag, hence propel the rest of the craft forward using magnets from both ends? Somewhat like being dragged towards a gravitational pull, but a magnet instead. The craft would never slow down until reverse propulsion is used.
This will work great as soon as someone figures out how to drag forward those magnets so they could drag the spacecraft with them...
(Sorry, couldn't resist...) -
#1767 by RFPlumber on 16 Jan, 2016 04:52
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Concluding that "We believe that this is a good education project to track down measurement errors and as a worst case we may find how to effectively shield thrust balances from magnetic fields" says it all
He seems to be implying that the EM Drive is a study in "side effects" and "false signals" and he does state that he cannot confirm or refute any of the claims by Roger Shawyer for the EM Drive, who is furthermore listed as an assistant to the project !QuoteAcknowledgement
We would like to thank Roger Shawyer for his assistance
So... it is almost like he is trolling Shawyer?
This is a whole new angle to how to read this paper then 
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#1768 by Stormbringer on 16 Jan, 2016 06:23
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This will work great as soon as someone figures out how to drag forward those magnets so they could drag the spacecraft with them...
(Sorry, couldn't resist...)
Here you go: http://www.psfk.com/2016/01/moon-shoes-moonwalker-moonshine-crea.html -
#1769 by rfmwguy on 16 Jan, 2016 13:01
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@rfmwguy: what material did you finally decided on. I heard something about brass, but then you were talking about copper spinning.
Still dependent on whether I can find a spinner and which material they prefer. If it is brass, I'll copper flash it and perhaps silver it. Not 100% decided yet. -
#1770 by Rodal on 16 Jan, 2016 13:10
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Just received the following communication from Australia. I believe he could use some emdrive design help. See attachment for his contact info:
"Dave,
just a note to thank you for your report dated 10/2015 describing your thruster experiments. I am attempting to produce the effect using a 60GHz diode resonator but lack the experience required to design the waveguide and signal insertion.
Please let me know if anyone is interested in recommending design ideas.
Meantime, good luck with further experiments. What a useful method of propulsion this could be.
Yours John Newell..
N.B: An attempt to explain the mechanism of action is attached"
John Newell,
You may be interested in reading this post (and the other posts in that NSF thread): https://forum.nasaspaceflight.com/index.php?topic=39214.msg1474347#msg1474347
as you are attempting to conduct this experiment at 60GHz, which is ~60/2=30 times higher frequency than NASA Eagleworks. Therefore, the dimensions of your EM Drive would have to be 1/30 of the dimensions of NASA's EM Drive (your diameters would have to be 1/30 of the diameters and the length would have to be 1/30 of the length), in order to be able to be excited with the same mode shape. For example, the length would have to be 0.3 inches (7.6 mm) instead of 9 inches (229 mm).
Using the same material (copper) and keeping everything else the same, that means that the quality of resonance (Q) would be Sqrt[30]=5.48 times smaller, and therefore, the force/power predicted by all three theories (McCulloch, Shawyer and Notsosureofit) would be 5.48 times smaller.
Another problem is due to the fact that power fed into the EM Drive is roughly proportional to the volume of the internal cavity. Since your EM Drive would be tiny (7.6 mm long) with a much higher frequency (60GHz) you most likely would be feeding a much smaller power (as done by the group at Aachen with a miniature EM Drive at 24 GHz) because the volume is much smaller, which in turn would result (according to all three theories (McCulloch, Shawyer and Notsosureofit)) in a proportionally smaller force, meaning that you would have to measure theoretical forces much smaller than the already tiny forces in NASA's experiment.
See http://emdrive.wiki/Experimental_Results for the entry "Baby EM Drive" by the group at Aachen, Germany, where they conducted tests at 24 GHz on a small EM Drive. The power they used was only 0.04 watts (4% of a watt !! ), which is orders of magnitude smaller than the power used in experiments with larger EM Drives.
Just like a bigger animal (for example a bear) is able to, proportionally, lose less of its energy through its body surface than a small animal (because the ratio of surfaceArea /volume decreases with increasing size), a bigger EM Drive will lose less energy than a small EM Drive and therefore a bigger EM Drive is more efficient: has a higher Q, and hence according to all three theories (McCulloch, Shawyer and Notsosureofit) has a larger force/power.
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#1771 by rfmwguy on 16 Jan, 2016 13:28
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Dr. Rodal and others -
Attached find my attempt, with SeeShell's guidance, to model the geometry of Tajmar's frustum. I have labelled the sections so that we can identify them for discussion.
...
(...)QuoteAcknowledgement
We would like to thank Roger Shawyer for his assistance
As you proved in your post just above this...anyone serious about doing their own experiment MUST come here to get out collective take on things. No one is 100% right or wrong, but the community will get designs much closer that what Dr Tajmar might of been lead to do...a seriously undersized/overcoupled assembly IMHO. -
#1772 by rfmwguy on 16 Jan, 2016 14:03
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I'd like to thank monomorphic, from another forum who put together a great comparison of most known emdrive cavities. Well done and thanks for sharing!
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#1773 by Rodal on 16 Jan, 2016 14:12
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I'd like to thank monomorphic, from another forum who put together a great comparison of most known emdrive cavities. Well done and thanks for sharing!
If you are in contact with her/him, perhaps you can ask him/her to add the Aachen group "Baby EM Drive" and Shawyer's Flight ("Boeing project") Flight Thruster to the very nice plot.
The fact that the Baby EM Drive and the Flight Thruster experiments were conducted at a higher frequency than 2.45 GHz should not be a deterrence because the NASA tests were conducted at lower frequencies than 2.45 GHz. The frequency of the experiments could be annotated below each EM Drive.
And what also matters is the mode shape really, and NASA had very different mode shape (TM212) than Shawyer and Yang (TE012 or TE013), and Tajmar (TM010). Also, NASA's and Shawyer's Experimental had dielectric inserts, while other EM Drives did not. So, several are different already, might as well show all the shapes and dimensions tested
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#1774 by SeeShells on 16 Jan, 2016 16:17
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Before I set upon the what I'll call the burning probe matchstick test (about a month ago) that ended with me toasting my waveguide antennas into the frustum and the direct designed coupling from the magnetron into the coax I was hoping to have it last long enough to get some results. Sadly it didn't, but I had other plans in the works that I have been actively perusing since then to stabilize the dual phase reversed injection into the drive. I feel this is the best way to have a stable high power injection into the drive.
This design addresses the shortcomings of the prior test in phasing the two incoming RF signals. I talked about this method very lightly about 6 months ago using two phase locked magnetrons, but I found way too many design hurdles to overcome using the direct injection method. One was the massive amount of excess heat from the magnetrons that would be strapped onto the cavity, swamping any measurements of thrust.
If the burning probe matchstick test failed because of design limitations (which it kind of did, got a large force displacement on the digital scales before it fried itself) I had plan number 2. And I'll present it here for the first time and invite comments.
Getting together pieces and parts to build, I've had to go surplus because it's not cheap. From the undocumented power on test results of the first one I know it's the way I need to go to assure a stable clean high power high Q mode control into my drive.
Shell
PS: RfPlumber this is why I hadn't answered your last question, simply I've gone beyond it and I'd welcome any inputs you or anyone may have.
Added: Speeeling corrections.
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#1775 by SeeShells on 16 Jan, 2016 16:48
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I'd like to thank monomorphic, from another forum who put together a great comparison of most known emdrive cavities. Well done and thanks for sharing!
VERY nice piece of work and a great way to look at the current designs!
Shell -
#1776 by glennfish on 16 Jan, 2016 16:55
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This design addresses the shortcomings of the prior test in phasing the two incoming RF signals.
Not being an RF type, but trolling the RF posts, would it be reasonable to ask for the dimensions and see what MEEP would predict for the injection port characteristics and any other effects that would happen in the waveguide?
Having worked a few microwave backhauls in my time, there could be a few oh-by-the-ways buried in the design. In my world it's usually a straight haul from the transmitter port to the antenna. Something like this would floor the RF guys I work with, not that it won't work, I can just picture the reaction I'd get if I said, "we're going to use this on the next link."
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#1777 by SeeShells on 16 Jan, 2016 17:17
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Sure Glen it's not perfect and I welcome thoughts on how I could do a straighter shot into the cavity.
This design addresses the shortcomings of the prior test in phasing the two incoming RF signals.
Not being an RF type, but trolling the RF posts, would it be reasonable to ask for the dimensions and see what MEEP would predict for the injection port characteristics and any other effects that would happen in the waveguide?
Having worked a few microwave backhauls in my time, there could be a few oh-by-the-ways buried in the design. In my world it's usually a straight haul from the transmitter port to the antenna. Something like this would floor the RF guys I work with, not that it won't work, I can just picture the reaction I'd get if I said, "we're going to use this on the next link."
I started this basic layout about three months ago and as I learned more about waveguides and what I needed I ran across John F. Gerling's VP of Gerling Applied Engineering, Inc very nice paper on the basics about a month ago. He had almost the same design I'd done but with a few additions I liked. I'd used only one phase shifter (I saw going into the cavity off phase with one side being out of phase wasn't going to be right). Also I speced flexible waveguides for the bends and my tuner was different.
I even have a design using one waveguide to the frustum and splitting it there but I'm worried about the extra weight.
Shell
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#1778 by rfmwguy on 16 Jan, 2016 17:46
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Nice Shell...remember, 90 degrees out of phase is OK, 180 would be "problematic"
Sure Glen it's not perfect and I welcome thoughts on how I could do a straighter shot into the cavity.
This design addresses the shortcomings of the prior test in phasing the two incoming RF signals.
Not being an RF type, but trolling the RF posts, would it be reasonable to ask for the dimensions and see what MEEP would predict for the injection port characteristics and any other effects that would happen in the waveguide?
Having worked a few microwave backhauls in my time, there could be a few oh-by-the-ways buried in the design. In my world it's usually a straight haul from the transmitter port to the antenna. Something like this would floor the RF guys I work with, not that it won't work, I can just picture the reaction I'd get if I said, "we're going to use this on the next link."
I started this basic layout about three months ago and as I learned more about waveguides and what I needed I ran across John F. Gerling's VP of Gerling Applied Engineering, Inc very nice paper on the basics about a month ago. He had almost the same design I'd done but with a few additions I liked. I'd used only one phase shifter (I saw going into the cavity off phase with one side being out of phase wasn't going to be right). Also I speced flexible waveguides for the bends and my tuner was different.
I even have a design using one waveguide to the frustum and splitting it there but I'm worried about the extra weight.
Shell
This is a good way to "stir the EM pot" at the frustum, but it might interfere with mode stability. Good thing about it is being adjustable is you can find the optimum phase angle. This will be VERY interesting to see. If a wormhole vortex opens up over Colorado, we're blaming you!
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#1779 by X_RaY on 16 Jan, 2016 17:57
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Before I set upon the what I'll call the burning probe matchstick test (about a month ago) that ended with me toasting my waveguide antennas into the frustum and the direct designed coupling from the magnetron into the coax I was hoping to have it last long enough to get some results. Sadly it didn't, but I had other plans in the works that I have been actively perusing since then to stabilize the dual phase reversed injection into the drive. I feel this is the best way to have a stable high power injection into the drive.
Hi Shell,
This design addresses the shortcomings of the prior test in phasing the two incoming RF signals. I talked about this method very lightly about 6 months ago using two phase locked magnetrons, but I found way too many design hurdles to overcome using the direct injection method. One was the massive amount of excess heat from the magnetrons that would be strapped onto the cavity, swamping any measurements of thrust.
If the burning probe matchstick test failed because of design limitations (which it kind of did, got a large force displacement on the digital scales before it fried itself) I had plan number 2. And I'll present it here for the first time and invite comments.
Getting together pieces and parts to build, I've had to go surplus because it's not cheap. From the undocumented power on test results of the first one I know it's the way I need to go to assure a stable clean high power high Q mode control into my drive.
Shell
PS: RfPlumber this is why I hadn't answered your last question, simply I've gone beyond it and I'd welcome any inputs you or anyone may have.
Added: Speeeling corrections.
could you so kind to add the circulator direction ( or port numbers & type/datasheet)?
I have to think about the effect of your phase shifters.
This is a whole new angle to how to read this paper then 
