Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1802434 times)

Offline X_RaY

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Interesting book!

chapter 5, page 167ff, output circuits

Q factor of a magnetron and many more

https://www.jlab.org/ir/MITSeries/V6.PDF
« Last Edit: 07/25/2015 01:18 PM by X_RaY »

Offline Rodal

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The latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.

By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?

Thanks and have a nice weekend because this Monday will really be interesting.

PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.
I'm concerned with the headline "EmDrive could reach Pluto in 18 months" being so at odds with what I heard was Prof. Tajmar's experimental data he had obtained a couple of months ago:

less than 50 microNewton for hundreds of watts inputPower, in a partial  Vacuum

To put this in context, see:  http://emdrive.wiki/Experimental_Results

if this is compared with "propellant-less" claims

Yang          270,000 microNewtons for 300 watts inputPower  in Air
Shawyer    174,000 microNewtons for 400 watts inputPower  in Air

NASA                  55 microNewtons for    50 watts inputPower in Vacuum
Tajmar less than  50 microNewtons for several hundreds or watts inputPower  in Vacuum

compare with the propellant competition:

VASIMIR    5,700,000 microNewtons for 200,000 watts inputPower in Vacuum  with Argon Propellant

The numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even lower (when taking into account the InputPower) than obtained by NASA.

Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower  Vacuum. ???

Actually, 50 microNewtons for hundreds of watts is such a low thrust/InputPower that it is dubious whether it can even show anything in Low Earth Orbit, as air drag in LEO may overwhelm such tiny thrust.

The headline (Pluto in 18 months) is so at odds with actual experimental results !

Unless Prof. Tajmar has obtained much higher numbers than what he got a couple of months ago, on the contrary, these data is going to be seen by John Baez and Sean Carroll and others as showing what they already called "the incredibly shrinking force" as the thrust/InputPower, instead of increasing with further examination progressively shrinks.

I don't understand how raising the hopes sky-high with "reaching Pluto in 18 months" is commensurate with new results showing a thrust that is orders of magnitude smaller than what others previously claimed.

On the contrary, raising the hopes sky-high (in another EM Drive forum people are already posting that Tajmar's presentation is going to be "huge" news) can only serve to further raise disappointment.  It would have been much better if people would have waited to see what Tajmar actually presents.


« Last Edit: 07/25/2015 01:36 PM by Rodal »

Offline Prunesquallor

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The latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.

By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?

Thanks and have a nice weekend because this Monday will really be interesting.

PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.

I've read that even with low thrust it would still be useful for getting around the Solar System?

The key parameter is Thrust/Power. That is, assuming that continuous thrust is possible, about which some have strong opinions.
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Offline Star One

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The latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.

By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?

Thanks and have a nice weekend because this Monday will really be interesting.

PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.
I'm concerned with the title of the article EM Drive getting to Pluto in 18 months being so at odds with what I heard Prof. Tajmar's experimental data had obtained a couple of months ago:

less than 50 microNewton for hundreds of watts inputPower, in a partial  Vacuum

To put this in context, see:  http://emdrive.wiki/Experimental_Results

if this is compared with

Yang          270,000 microNewtons for 300 watts inputPower  in Air
Shawyer    174,000 microNewtons for 400 watts inputPower  in Air
NASA                  55 microNewtons for    50 watts inputPower  in Air

it can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.

Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower  Vacuum. ???

Unless Prof. Tajmar has obtained much higher numbers than what he got a couple of months ago, on the contrary, these data is going to be seen by John Baez and Sean Carroll and others as showing what they already called "the incredibly shrinking force" as the thrust/InputPower, instead of increasing with further examination progressively shrinks.

I don't understand how raising the hopes sky-high with "reaching Pluto in 18 months" is commensurate with new results showing a thrust that is orders of magnitude smaller than what others previously claimed.

On the contrary, raising the hopes sky-high (in another EM Drive forum people are already posting that Tajmar's presentation is going to be "huge" news) can only serve to further raise skepticism.  It would have been much better if people would have waited to see what Tajmar actually presents.

Precisely headline seems to be just click bait & nothing else.

Offline rfmwguy

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This is a good news bad news article for sure. Without knowing the mechanical and electrical configuration, its hard to judge...

However, for a lab that is known for eliminating measurement "noise", this experiment appears to rise above it in a vacuum; meaning this is not a propellant force, it is a propellantless force.

The door has been cracked open. Maybe one of us can help walk through it...

Offline Prunesquallor

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it can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.

Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower  Vacuum. ???


I look at this quite differently. If ANY verifiable, repeatable, non-experimental-artifact thrust significantly exceeding photon rocket level is demonstrated, it is mind-blowing. I seriously doubt that the experiments being performed today would have stumbled upon the optimal combination of design parameters that maximize performance. Getting the general principles accepted and understood is step one. THEN the engineers can go wild and see what the potential really is.  Having goals for that performance (e.g. space applications) is, I think useful even if the lab results are not there yet.

The Wright brothers demonstrated that the combination of the tecnology of the internal combustion engine and the science of aerodynamics could result in a heavier-than-air machine with lift/weight>1.  Many experts had declared that impossible. One could argue that the P-51 or the B-29 were straightforward engineering enhancements of those basic principles.
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Offline Rodal

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aero: did you say that you had run a Yang/Shell model with the antenna near the small end, in the transverse direction? (I thought you said that in a message, but I cannot find it)

If so, where are those .csv files?  in what folder?

are the Big End and Small End cuts at the correct location, or do you also have to re-run them again for the Yang/Shell case with the antenna near the small end?

is the mesh and the time step and the time slice information exactly the same as for the model with the antenna at the big end?

I cannot find such information

It would be nice to compare Yang/Shell with the antenna near the small end to see whether it looks better than with the antenna near the big end.

Based on the last run, placing the 58mm dipole antenna next to the big end in the longitudinal direction really looks bad.
« Last Edit: 07/25/2015 02:34 PM by Rodal »

Offline SeeShells

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The EMDrive has shown a red flag by
Air=thrust, No air=little thrust

Air = acoustic vibration on big end plate greater than small end plate (enables switch from IDLE to MOTOR mode).

No air = no acoustic vibration (hard to get out of IDLE mode).

But it does indicate thrust ~1.22% of the thrust with air. Where I'm at now is digging through the calculations to compare the number of molecules in a copper frustum on the inside copper, 3-5 um deep where I suspect ~20% are under the influence of the EM waves in the small end part of the cavity and compare that number with the amount of air that's removed in a vacuum. I think we'll find a good correlation.

I'll take this from Dr. Rodal's post just below.
Yang          270,000 microNewtons for 300 watts inputPower  in Air
Shawyer    174,000 microNewtons for 400 watts inputPower  in Air

NASA                  55 microNewtons for    50 watts inputPower in Vacuum
Tajmar less than  50 microNewtons for several hundreds or watts inputPower  in Vacuum

This is where I'm at and starting to bog down.
AIR
1 ft³ of air = 28.316847 litres
1 mole of any gas at STP = 22.4 litres
so 28.316847 litres of air = (28.316847 / 22.4) moles
= 1.264145 moles
= 761.286E+21 atoms.

Surface area of the Copper Frustum
A = π2 (r12 + r22 + (r1 + r2) * s) = π * [ r12 + r22 + (r1 + r2) * √((r1 - r2)2 + h2) ]

r1 = 0.0794 m
r2 = 0.13985 m
h = 0.2286 m
s = 0.2365 m
V = 0.008849 m3
L = 0.1629 m2
T = 0.01981 m2
B = 0.06144 m2
A = 0.2441 m2

r1 = radius1
r2 = radius2
h = height
s = slant height
V = volume
L = lateral surface area
T = top surface area
B = base surface area
A = total surface area
π = pi = 3.14159
√ = square root

A = 0.2441 m2 /2 to get interior surface area 0.12206 m2

If anyone who is much better than me at this want to jump in feel free otherwise it's gonna be awhile. ;)

Offline zen-in

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The latest article by Wired about the EmDrive hit the space community hard (already 200 shares of the article). I see all the channels I check buzz with the news. Even some hardcore sceptics are looking with some kind of interest to see what Prof. Tajmar results will be (as far as I can tell). Many "enthusiasts" as me are dejected, because of possibly very low thrust, but I want to believe that all new technology need to start somewhere and can develop. And hope that maybe we can use it for terrestrial application in some not so distant future. And of course even low thrust can be the start of the new era in space for humanity and perhaps colonization of our solar system in very distant future.

By the way just curious. This Prof. Tajmar has really this good reputation? Or rather he has a good laboratory to prove / disprove EmDrive works?


Thanks and have a nice weekend because this Monday will really be interesting.

PS: Get ready the forum can be flooded by posts for a while before it calms down after the Prof. Tajmar results.

The wired article just says there is yet another theory about how the em-drive works.

http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission
« Last Edit: 07/25/2015 02:26 PM by zen-in »

Offline X_RaY

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To get more control about the transmission factor into the resonator and get impedance matching against the magnetron there may be a (relative) simple way.
For that one need a 3 stub tuner, 50 Ohm broadband load, two high voltage schottky diodes and a xy-oscilloscope.
If the coupling is realized as a waveguide(the magnetron is), it is possible to use 2 schottky in a small distance(i think the needed was 45 deg? of phaseshift inside the waveguide) to get I,Q signal. Power schottky are available for high voltages (for example 170V) but it would be important to use a verry short length of the schottky stub-antenna inside the high power waveguide otherwise the magnetron kill the diode.
The signals on the diodes will generated by signal mixing of the forward(45deg) and reflected(also 45deg) wave component. That results in 2 canals with 90 deg phase difference --> Inphase and Quadrature

Use a xy-oscilloscope, put the load at the end of the magnetron and tuner line (unused tuner, screws as out as possible). Put the RF on. Measure the Voltage of the diodes. Tune both channels to be null Volt DC with the scope offsets. Switch the RF off.
After this, place the waveguide antenna feed onto the cavity.
Switch the RF on again and use the waveguidtuner to get impedance matching (the scope have to show null Volts for both channels as you are calibrated before)
tadaaa   Z=~50 Ohm  ;D 8)

Tuner:
Take a (rectangular) waveguide for the frequency of interest.
Calculate the wavelength using the dimensions of your waveguide.
Drill 3 holes into the waveguide at the middle of the a-axis, the first is random, the next two have to be in a distance of, i think it was for example(take a look of some design rules..) 1*lambda/8, 3*lambda/8, or 5*lambda/8 or something like that. Take some screws and put they into the holes

Detector diodes:
Same game, drill a hole (random) in a waveguide (some half wavelength away from the tuner) and a second in a distance of Lambda/8 to the first (or lambda/4? can't remember exactly) than stick one wire of the diode into the hole and fix it. This technique is also be used in gunn oscillator transceivers (CW).

I have tested the   procedure for commercial µW-sensors, it will work  8)
good luck and have fun while testing

This is a great idea, and will indeed work, BUT. It uses a "pure" 50 ohm load as the "reference". The frustum is very likely nowhere near a 50 ohm load, nor is that the load that the magnetron is expecting to see for maximum radiated power ( best match) in all likelyhood.

My own thought is that trying to design a cavity (frustum) "tuned" to a spectrally noisy source like a magnetron is a thankless task. How about designing the cavity (frustum) to a "best practices" standard. OFHC walls and ends, internally silver plated. Later you could even niobium plate it for superconducting tests. I'd consider making the frustum capable of at least 60 PSI internal pressure, or internal hard vacuum  for later filling with arc suppressors, maser gain media for higher frequency designs, or testing under vacuum.

The source would be a klystron (or other high power/high gain/relatively low phase noise amplifier  of your choice - NOT a noisy oscillator like a magnetron), coupled to the frustum via a crossguide or other well matched dual-directional coupler. This would almost take the frustum out of the equation, leaving you with a microwave source, driving the klystron, that could be a good lab quality microwave synthesizer. This gives you control over frequency, modulation (AM/FM,perhaps even phase), and power. The coupler gives you direct forward and reflected power, allowing direct match and Q measurement via power meters or spectrum analysis (or even a VNA), and the sampled signals could be used to directly phase or frequency lock the synthesizer at any point of interest (like measured thrust). Most modern lab quality synthesizers can be easily phase locked to a coupler output with a bit of signal conditioning.

I know this kind of turns the approach "on its head". Experimenters seem to be trying to make the perfect frustum for a very imperfect source. I think SeaShell has recognized this by making a frustum that can be relatively easily modified, and may negate atmospheric effects. I submit it's the microwave source that needs control, not the frustum. In other words, there's nothing "magic" about a magnetron. There may be something about the inherent modulation of an easily available magnetron (they're inherently very low Q oscillators, and amplitude modulate 100% at 50 or 60 Hertz if they are powered by a microwave oven supply).

This could be (relatively) easily tested with a fully controllable source, with the frustum itself as a "fixed" element in the experimental protocol.

Just some thoughts.
For all the people with lab in background or much money it's true that is no problem to measure the S-parameter with VNA. And it is no problem with broadband source and amp to find the optimal frequency (where S11 |r|=~0).
It's a possible way for people with low budget and Microwave Oven magnetrons. They can't sweep the frequency.
And yes of course (for this one point calibration) use a termination-load, it produce almost no reflections. For a magnetron+resonator situation this is the point with highest Transmission factor into* the resonator, means highest Q of the whole system. The waveguide tuner is a transducer between the different Z values of the magnetron and the cavity (one can tune also the cavity it selves or the antenna but all that leads to ~equal results, impedance matching).

* into AND out of the cavity! Both the internal Q of the resonator and the external Q (magnetron, waveguide losses, coupling factor,...) is important in real world experiments:
1/Q_eff= 1/Q_int+1/Q_ext
« Last Edit: 07/25/2015 02:22 PM by X_RaY »

Offline SeeShells

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This is a good news bad news article for sure. Without knowing the mechanical and electrical configuration, its hard to judge...

However, for a lab that is known for eliminating measurement "noise", this experiment appears to rise above it in a vacuum; meaning this is not a propellant force, it is a propellantless force.

The door has been cracked open. Maybe one of us can help walk through it...
Honestly I think the crack is showing and after I went to bed last night up way too long I could do nothing but semi-dream of the actions in the frustum.
<quote>
http://ntrs.nasa.gov/search.jsp?R=20150006842&qs=Nm%3D4294903350%7CAuthor%7CWhite%2C%2520Harold%26N%3D0

Makes so much sense in ways that even I can draw a parallel between all of them, eigenfrequencies, the casimir effect and a natural vacuum state that really seems to be mutable.

The EMDrive has shown a red flag by
Air=thrust, No air=little thrust

Doesn't this come close to what Todd has been thinking? What if through the wave actions of the cavity we alter the natural mutable vacuum by modifying the eigenfrequencies  of the matter in the cavity and even the walls of the frustum creating an area where the flustrum falls forward because it mutates the immutable Q vacuum and interacts with the "outside" QV.

Air=thrust
No air=little thrust ... the only thing still around is the QV and the copper of the cavity. The inside copper skin of the cavity ~5um is still interacting with the harmonic wave actions including evanescent and ghost modes inside of the cavity so the ~5um depth may be a little deeper.
What I'm wondering we have a thrust of (Ta) Thrust air and Thrust (Na) no air, what is the percentage of difference in mass between the two? Can a close ratio be derived between the thrust values?

My SO is telling me I need to go to bed. So I'll leave you all with this crazy Eddie thought. Be back in the morning over a cuppa joe.

Shell <End Quote>
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409349#msg1409349

So not able to sleep I got my cuppa of coffee and started to drudge through volumes of air vs no air and compare thrusts with what is left in the evacuated frustum... copper ~5 um of copper and compare it to the decrease in thrust percentages. 

What I see and what I can calculate with rusty math is gonna take awhile.

And a good morn to you... need more coffee!!! ;)

Shell

Added..
And the 5 um depth isn't just a solid barrier where the wave actions switch on and off it is starting to involve Heisenberg and all the actions on the immediate surface and into a depth of the copper where the EM waves strike. I need to simply simplify this is not a paper just rough calculations.
« Last Edit: 07/25/2015 02:26 PM by SeeShells »

Offline Rodal

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If anyone who is much better than me at this want to jump in feel free otherwise it's gonna be awhile. ;)

Look at the mean free path :  https://en.wikipedia.org/wiki/Mean_free_path and the vacuum https://en.wikipedia.org/wiki/Vacuum Wikipedia articles:


NASA and Tajmar tested (5*10^(-4) to 5*10^(-6) Torr) under high vacuum defined as (10^(−3) to 10^(−9) Torr) hence

10^13 – 10^9 molecules per cubic centimeter

as compared to

2.7 × 10^19 molecules per cubic centimeter  at ambient pressure

so, ambient air has more than a milllion 10^6 =1,000,000 (to up to 10^10=10 billion) times more molecules per cubic centimeter

« Last Edit: 07/25/2015 02:27 PM by Rodal »

Offline SeeShells

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...

If anyone who is much better than me at this want to jump in feel free otherwise it's gonna be awhile. ;)

Look at the mean free path :  https://en.wikipedia.org/wiki/Mean_free_path and the vacuum https://en.wikipedia.org/wiki/Vacuum Wikipedia articles:


NASA and Tajmar tested (5*10^(-4) to 5*10^(-6) Torr) under high vacuum defined as (10^(−3) to 10^(−9) Torr) hence

10^13 – 10^9 molecules per cubic centimeter

as compared to

2.7 × 10^19 molecules per cubic centimeter  at ambient pressure

so, ambient air has more than a milllion 10^6 =1,000,000 (to up to 10^10=10 billion) times more molecules per cubic centimeter
True... from https://answers.yahoo.com/question/index?qid=20111022145659AA2rCsy

The molar mass of copper is 63.55 g/mol. So, you convert grams to moles 127.08/63.55 =1.999 moles copper. Now, 1 mole = 6.022e23 atoms, so multiply # of moles by 6.022e23. 1.999 x 6.022e23= # of atoms of copper.

Then I need to consider how the EM wave might have more of an effect on the copper than air, different permeabilities.

Added. I sure don't want to throw this little hot potato into someones lap but I could use some help, maybe a little butter and salt on it? It is now getting beyond what my rusty math can do on a piece of paper. so Doc if you want to make mashed potatoes of it I'll try to help where I can.
« Last Edit: 07/25/2015 02:41 PM by SeeShells »

Online RotoSequence

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I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?
« Last Edit: 07/25/2015 03:07 PM by RotoSequence »

Offline RonM

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it can only be seen as disappointing, as the numbers obtained by Tajmar a couple of months ago are so much lower than reported by Yang and Shawyer and even much lower (when taking into account the InputPower) than obtained by NASA.

Who thinks that one can get to Pluto in 18 months with something that only gives 50 microNewton for hundreds of watts inputPower  Vacuum. ???


I look at this quite differently. If ANY verifiable, repeatable, non-experimental-artifact thrust significantly exceeding photon rocket level is demonstrated, it is mind-blowing. I seriously doubt that the experiments being performed today would have stumbled upon the optimal combination of design parameters that maximize performance. Getting the general principles accepted and understood is step one. THEN the engineers can go wild and see what the potential really is.  Having goals for that performance (e.g. space applications) is, I think useful even if the lab results are not there yet.

I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

Still, I await the numbers and verification at other labs before I believe it. However, I am more optimistic that another test in vacuum shows some thrust.

The Wright brothers demonstrated that the combination of the tecnology of the internal combustion engine and the science of aerodynamics could result in a heavier-than-air machine with lift/weight>1.  Many experts had declared that impossible. One could argue that the P-51 or the B-29 were straightforward engineering enhancements of those basic principles.

With more hard work we went from the P-51 to the SR-71. Maybe one day the EM drive will live up to the hype.
« Last Edit: 07/25/2015 03:17 PM by RonM »

Offline RonM

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I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?

That is worth testing. Without a proven theory to guide experimenters, it's worth testing various combinations and designs of EM drives. We're kind of at the alchemy level of knowledge, so experiments are the key.

Offline ThereIWas3

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If I follow Shell's reasoning correctly, it may matter exactly which gas fills the chamber, and how the Cu walls interact with it.  Perhaps air (mostly Nitrogen) is not the best choice.
"If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea" - Antoine de Saint-Exupéry

Offline SeeShells

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I'm not sure I completely grok where we're the discussion is going, but are we thinking about taking a look at a gas-filled, sealed (safety valves obviously necessary) EM drive, to see if it will achieve greater thrust in a vacuum than ventilated test articles?
Yes, along those lines, you have any answers on it? Does anything change if the frustum is filled? If so what percentages of change in thrust? What gas is used? What air pressures? Was the vacuum chamber slowly filled to ambient air pressures monitoring thrust? Did the thrust reappear when all else remained the same except the Vacuum chamber's air pressure?

Shell

speeeelingug
« Last Edit: 07/25/2015 03:31 PM by SeeShells »

Offline Notsosureofit

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I agree. By accepted theory, there should be no thrust whatsoever beyond a photon rocket. If there really is verifiable excess thrust, no matter how small, then this a breakthrough.

If by accepted theory you include General Relativity, then there should be a small thrust as long as you can accept some deviation from perfectly "flat" space.  (the swimming spaceman was a good example)

Offline Ricvil

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1) aero is modeling the Copper as a Drude material.  The Drude material constants he is using are equivalent to a material of unrealistically small resistivity.  An idea would be to try different Drude material constants that effectively bring up the resistivity such that a reasonable Q=45,000 is obtained

That sounds like cheating, a bad idea if it masks a flawed premise, like using an over-coupled dipole where a loosely coupled 1/4 wave probe or loop should be used. Or even an eigenmode excitation from Mpd. Just saying. I know, I need to stop criticizing and do it. I want to. My computer isn't amenable.

I would think if the Drude model came from Meepers, the units, being normalized to u0 and e0, would be natural and not the problem. But I speak from ignorance I'm eager to relieve.

2)  it is due to the fact that Meep is attempting to obtain Q from a time decay from the time response.

That should be entirely valid. However, think of the whispering gallery, with start-up transients. It matters where, as well as when the measurement is made.

Otherwise Meep needs to perform volume and surface integrations of the fields, in order to calculate Q during this transient period.

Perhaps Mpd (Meeps eigenmode harmonic solver) could do that real fast?


<<I would think if the Drude model came from Meepers, the units, being normalized to u0 and e0, would be natural and not the problem. But I speak from ignorance I'm eager to relieve.>>

No, take a look at the Drude model, its properties are very dependent on frequency.  The Drude model constants available are for the optical range and wholly inapplicable to the 2.45 GHz range. The Drude model constants are not u0 and e0



This Drude model is in Frequency Domain (FD) and Meep's cavity simulation works in Time Domain (TD), then how a complex number apears in a TD simulation?

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