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#1180
by
X_RaY
on 30 Dec, 2016 17:11
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If we bring the height to 276 mm and keep the top and bottom the same, we'll get TE013 at 2.45 GHz.
Adjacent modes at 2.43 and 2.51, but the 2.43 GHz is a TM mode so shouldn't be a problem.
These other modes should be a problem for true, that's pretty close in frequency! Especially if he try to excite a TE01 mode pattern with a stub antenna. 
Good point. But with this mode I don't think we're going to get much more separation than that without using some sort of mode suppressing structure.
Lets use a loop instead so that a TM is less likely and adjust something else for min VSWR. Maybe bend the top or bottom plate with external bolts?
OR introduce a waveguide with circular iris coupling near the center node. A standard WR340 coax to waveguide could be used and stubs in the waveguide could help match the iris/cavity.
http://www.industrialshop.online/p/industrial-electrical/antennas__carolina-microwave-wr-340-waveguide-to-n-female-end-launch-co/a-B01LXG0HOE
Maybe $340 is a bit steep for this DIY project... Making one probably wouldn't be that difficult though.
In principle yes. Better would be a redesign in a way to keep other modes as far as possible. This can be done by altering the diameter(s) with re-adjustment of the length to reach 2.45GHz again.
This is the reason why I builded a spreadsheet that calcs more than 20 modes at the same time 
But then we mess with TT's DF...
What amount of mode separation would be sufficient?
Excellent question, next please
20MHz sounds a little less.
In fact it depends on the BW of the favorite mode and the parasitic modes.
For this reason i state -as far away as possible-.
To stay clear, this is from the microwave engineering perspective.
Till now it is not clear if mode interactions could cause thrust (if...) , if my memory serves I think Shell was on the way to test this.
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#1181
by
Donosauro
on 30 Dec, 2016 18:03
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I believe this has been waited for by some on here.
Now that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers. Marc Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, has spent the last two months reviewing the relevant papers. Although he is the primary author of what follows, he has enlisted the help of scientists with expertise in experimental issues, all of whom also contributed to BPP, and all of whom remain active in experimental work. The revisions and insertions of George Hathaway (Hathaway Consulting), Martin Tajmar (Dresden University), Eric Davis (EarthTech) and Jordan Maclay (Quantum Fields, LLC) have been discussed through frequent email exchanges as the final text began to emerge. Next week I’ll also be presenting a supplemental report from George Hathaway. So is EmDrive new physics or the result of experimental error? The answer turns out to be surprisingly complex.
http://www.centauri-dreams.org/?p=36830
A very good review. Thanks for posting it.
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#1182
by
RERT
on 30 Dec, 2016 18:28
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Sorry - are you saying it was a rumour that the EMdrive was to be discussed at a conference? Or that it was a rumour that there was a conference? Or that it was a rumour that the conference finished on the 25th?
Unless I'm hallucinating, this news/?rumour? generated much interest. Not rounding things out with some report on what happened seems wrong. Even if the report is 'It was a mistake, the EMdrive was not discussed', it would be better than nothing.
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#1183
by
Star One
on 30 Dec, 2016 18:39
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I believe this has been waited for by some on here.
Now that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers. Marc Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, has spent the last two months reviewing the relevant papers. Although he is the primary author of what follows, he has enlisted the help of scientists with expertise in experimental issues, all of whom also contributed to BPP, and all of whom remain active in experimental work. The revisions and insertions of George Hathaway (Hathaway Consulting), Martin Tajmar (Dresden University), Eric Davis (EarthTech) and Jordan Maclay (Quantum Fields, LLC) have been discussed through frequent email exchanges as the final text began to emerge. Next week I’ll also be presenting a supplemental report from George Hathaway. So is EmDrive new physics or the result of experimental error? The answer turns out to be surprisingly complex.
http://www.centauri-dreams.org/?p=36830
A very good review. Thanks for posting it.
It's certainly very through isn't it.
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#1184
by
otlski
on 30 Dec, 2016 20:14
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Would appreciate those of you with other modeling tools to have a look at this design. It is NOT the EW thruster, which I will do next. Please check the freq and the Qu so I can get this design bolted down and started to be made real.
As always comments and advise are sought as I feel we all want to see this thruster doing several revs on the test bed.
Thanks,
Phil
TT - assuming a 0.015" diameter torsion wire at 72" long, and given that your thrust estimates hold up, you would get 1.7 turns before maximum angular excursion.
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#1185
by
Joris
on 31 Dec, 2016 01:48
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Here you go.
Maybe use a cheap single-board computer or a smartphone instead of a laptop. Since laptops usually have a fan that ends up blowing air in a certain direction. (To the left for me, with a non-negligible force in the setup, messing up the experiment.)
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#1186
by
toloverufan
on 31 Dec, 2016 01:57
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He's made it clear the laptop doesn't have a fan. The only way it could blow air in any direction is by heating it.
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#1187
by
oyzw
on 31 Dec, 2016 02:15
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Here you go.
Maybe use a cheap single-board computer or a smartphone instead of a laptop. Since laptops usually have a fan that ends up blowing air in a certain direction. (To the left for me, with a non-negligible force in the setup, messing up the experiment.)
I suggest to close the laptop with a resin box
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#1188
by
ThinkerX
on 31 Dec, 2016 02:58
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Heated resonance chamber will result in a convection over it. It will be asymmetrical due to the shape of the compartment. You can expect of force directed to the side. So much more than a laptop - it does not heat up evenly.
Laptop will have it's screen closed flat to the keyboard and in sleep mode during the thruster acceleration tests. Even when operating, it doesn't get hot, just slightly warm to the touch. Hard Drive is a non moving SSD.
There will be 4 "NULL" tests done to characterise the thermal effects of every thing on the Book Shelf and their ability to cause rotation.
1) thruster small end pointed Up
2) thruster small end pointed Down
3) thruster small end pointed into the centre
4) thruster small end pointed away from the centre.
All tests started AFTER the thruster is fully powered and has thermally and resonance freq change stabilised. So there should not be any significant thermal heat change of any of the object during the active portion of the rotary tests. Will test to be sure there is no rotary effect being generated by anything during the NULL tests.
Does that address your concerns?
Two additional suggestions:
1 - a 'Calibration Test,' using weights, as per Emmett Brown;
2 - a 'Null Thermal Test,' replacing the microwave emitter with a heat source. This because one of the complaints, justified or not, about Shawyer's rotary test was the various pumps and fans on the unit. This setup, best do something to remove all doubt that the motion comes from thermal action.
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#1189
by
TheTraveller
on 31 Dec, 2016 05:04
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Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
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#1190
by
TheTraveller
on 31 Dec, 2016 06:20
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#1191
by
TheTraveller
on 31 Dec, 2016 06:48
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Here you go.
Maybe use a cheap single-board computer or a smartphone instead of a laptop. Since laptops usually have a fan that ends up blowing air in a certain direction. (To the left for me, with a non-negligible force in the setup, messing up the experiment.)
The laptop has no fan. no moving parts except kb. SSD drive. Sofrware that sets freq and does sweep to test modes, antenna & lowest reflected power runs on the laptop which will be closed and in sleep mode when rotary test runs are done. 4 runs will be done with thruster orientations that should not cause movement, so to verify there are no rotational thrust sources.
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#1192
by
TheTraveller
on 31 Dec, 2016 07:03
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How are you thinking of adjusting the insertion angle? Sounds mechanically complex.
Do you think the stub should be perpendicular to the side wall or to the frustum axis?
Will have 2 threads attached to the end of the stub via 2 x 0.5mm dia holes in the side wall and 1 x 0.5mm hole in the centre of each end plate. Can then pull the end of the stub left/right/up/down to get lowest reflected power. Can also adjust in and out the amount the stub penetrates into the central lobe'e E field.
Will try to ident the mode via side wall and end plate thermal signatures plus can insert a probe to measure the E field lobes.
Would appreciate anyone doing a steady state averaged surface temp calc based on 25C ambient, 8 W Rf inside the thruster, 0.3m^2 area and 0.95 emissitivity. I used a flat plate heat sink calculator and obtained 50C, which seems too high.
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#1193
by
oyzw
on 31 Dec, 2016 07:11
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Blank, single sided, 1 oz, fibreglass, flat end plate thruster data:
1oz copper = ~35um thickness.
5x skin depth (full penetration) is ~6.6um.
Board is 1mm thick.
At 300x300mm square, weight is 0.33kg.
300mm dia = ~0.260kg big end.
170mm dia = ~0.085kg small end.
https://www.jaycar.com.au/blank-fibreglass-pcb-300-x-300mm/p/HP9510
Hello，How do you calculate such a high power thrust ratio?
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#1194
by
Stormbringer
on 31 Dec, 2016 07:34
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Sorry - are you saying it was a rumour that the EMdrive was to be discussed at a conference? Or that it was a rumour that there was a conference? Or that it was a rumour that the conference finished on the 25th?
Unless I'm hallucinating, this news/?rumour? generated much interest. Not rounding things out with some report on what happened seems wrong. Even if the report is 'It was a mistake, the EMdrive was not discussed', it would be better than nothing.
OYZW may not notice that this was (probably?) addressed to him?
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#1195
by
oyzw
on 31 Dec, 2016 07:41
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Sorry - are you saying it was a rumour that the EMdrive was to be discussed at a conference? Or that it was a rumour that there was a conference? Or that it was a rumour that the conference finished on the 25th?
Unless I'm hallucinating, this news/?rumour? generated much interest. Not rounding things out with some report on what happened seems wrong. Even if the report is 'It was a mistake, the EMdrive was not discussed', it would be better than nothing.
OYZW may not notice that this was (probably?) addressed to him?
Sorry, I may have missed your message, in December 25th there is no conference in Beijing, there is no information about the test on orbit announced, many rumors have been confirmed rumors.
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#1196
by
flux_capacitor
on 31 Dec, 2016 07:48
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Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
So your small end plate diameter is just
below Shawyer's minimum cutoff diameter rule, which is exactly 149.25 mm at 2.45 GHz for TE01x modes. With machining tolerances, don't you think it could be a problem? Plus as the real operating frequency will not be exactly 2,450,000,000 Hz this could be ok (if the frequency is above that value, since the small end becomes large enough) or it could be worse (if the effective resonant frequency is below the predicted value).
That's if Shawyer's cutoff rule of thumb from open waveguides has a physical meaning for truncated cone cavities.
EDIT: The calc has been provided by Rodal:
Mode Shape: TE01
Frequency: 2.45 GHz
Table of Bessel zeros and Bessel Derivative zeros:
http://wwwal.kuicr.kyoto-u.ac.jp/www/accelerator/a4/besselroot.htmlxEquation for cut-off diameter:
Ds = (X'01 *c)/(Pi*frequency)
= (3.83170597020751*299792458 m/s)/(Pi*2.45*10^9 1/s)
=
0.14925 mI'm now waiting for X_RaY, zelerium, Monomorphic… to show us the predicted resonant frequency as an exact solution calculated by a specialized software like FEKO.
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#1197
by
Flyby
on 31 Dec, 2016 08:11
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I believe this has been waited for by some on here.
......
http://www.centauri-dreams.org/?p=36830
Excellent article !!! simply the best I've seen so far on the EMdrive....
I really liked this quote because it totally embodies my current sentiment on the EMdrive :
I realize the urge within human behavior for fast, definitive answers that we can act on. This lingering uncertainty is aggravating, even more so when peppered with distracting hype or dismissive disdain. To get to the underlying reality, we must continue with a focus on the fidelity of the methods to produce reliable results, rather than jumping to conclusions on the implications.
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#1198
by
RERT
on 31 Dec, 2016 09:40
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Sorry - are you saying it was a rumour that the EMdrive was to be discussed at a conference? Or that it was a rumour that there was a conference? Or that it was a rumour that the conference finished on the 25th?
Unless I'm hallucinating, this news/?rumour? generated much interest. Not rounding things out with some report on what happened seems wrong. Even if the report is 'It was a mistake, the EMdrive was not discussed', it would be better than nothing.
OYZW may not notice that this was (probably?) addressed to him?
Sorry, I may have missed your message, in December 25th there is no conference in Beijing, there is no information about the test on orbit announced, many rumors have been confirmed rumors.
Thanks, that's clear enough, and sorry for not mentioning your name in my response. R.
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#1199
by
flux_capacitor
on 31 Dec, 2016 09:54
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Sorry - are you saying it was a rumour that the EMdrive was to be discussed at a conference? Or that it was a rumour that there was a conference? Or that it was a rumour that the conference finished on the 25th?
Unless I'm hallucinating, this news/?rumour? generated much interest. Not rounding things out with some report on what happened seems wrong. Even if the report is 'It was a mistake, the EMdrive was not discussed', it would be better than nothing.
OYZW may not notice that this was (probably?) addressed to him?
Sorry, I may have missed your message, in December 25th there is no conference in Beijing, there is no information about the test on orbit announced, many rumors have been confirmed rumors.
The EmDrive Chinese news is like making sentences from several fortune cookies combined together: the more there are, the less understandable.
