Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1878952 times)

Offline BL

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Flyby posted this:.

‘I, fe, have a hard time believing that the Q will scale so linear as has been assumed, but I would gladly be proven wrong by an experiment that shows it can be done....”

And rfmwguy said this:

“
We have a unique opportunity to shove this thing along or simply prove its not possible. While I'd love to prove its real, I'd also feel accomplishment by showing the alternative, as we all should.
"


As I understand it, Shawyer’s premise all along has been that the EmDrive will produce useful thrust AND that the thrust is proportional to Q and power. 

I hope he is right, but I am not qualified to critique his theory.

I am also all for any and all DIY’ers who are building and testing their own systems to, hopefully, either confirm or reject the validity of the generic EmDrive phenomenon.

What I worry about is that none of the experiments that I have seen being proposed on the forum have much of a chance (my opinion) of doing either.

They propose building a frustum ‘to spec’ to use microwave oven magnetrons as drivers.  These magnetrons run at 2.45 GHz (nominally), produce a lot of power, are cheap, and readily available. 

So what is the problem?

Several. 

Let’s postulate that the design/build process actually produces a frustum with one of its many resonant frequencies centered at exactly 2.45 GHz.   Let us also postulate that Shawyer was right and that when excited at the proper mode the frustum produces thrust proportional to Q and power.  Fixed dimension frustums described on the forum resonate at multiple frequencies, each with its own ‘Q’.  Let us also postulate that excited at the optimum mode the frustum has a relatively modest Q of 5000.  That implies that the bandwidth at that mode is around 500 kHz. 

Oven magnetrons as described on this forum produce lots of power centered, more or less, at the nominal 2.45 GHz.  Unfortunately, the power is spread over 30+ MHz and is delivered at several distinct frequencies.  The specific frequencies of the spectral lines and the distribution of power among them vary with the load seen by the magnetron, variations in the power supply, the temperature, and, for all I know, the price of tea in China.  For the purpose of heating water or ruining meat in an oven, that is not important.  For the purpose of testing frustums, it is.

The magnetron CAN be ‘locked’ to an external standard, but the design of the phase lock circuitry is non-trivial.  Even when phase locked they cannot be tuned over a wide enough frequency range to explore the various resonant modes of the frustums.  From what I have read most or all of the DIY projects will use a free running magnetron.

Given the above, what are the chances that:

 
a.  The frustum, AS BUILT, will actually have a resonant mode at 2.45 GHz?
b.  Of the many resonant modes of the frustum the one that produces thrust will occur at 2.45 GHz?
c.  One of the spectral peaks in the magnetron output will occur at 2.45 GHz?
d.  The spectral line occurring at 2.45 GHz will contain an appreciable portion of the total magnetron output power?
e.  The DIY’er who designed and built the frustum will be able to answer any of the above by injecting the output of the magnetron into his frustum?

The magnetron is not easily tuned, so if the DIY’er doesn’t get super lucky and wind up with the predominant magnetron output spectral line occurring at the exact frequency required to excite the frustum in the mode that will produce thrust he (she, in the case of SeeShell) will be dead in the water.   None of the ‘features’ of the magnetron output are readily or, perhaps more importantly, precisely and repeatedly, controllable. 

What is more likely is that the magnetron will perform as advertised, the frustum will develop hot spots in a pattern that can be analyzed by Dr. Rodal or others to determine the mode which was established, little or no thrust will be detected (even if Shawyer IS right), and the arguments and second guessing re the test procedures, whether the frustum needs to be ‘vibrated’, whether it could accelerate freely enough, whether the output spectrum was optimum, etc. will continue ad infinitum.  And that is with EmDrive thrust proportional to Q and power POSTULATED to be valid. 

To guarantee that output of the magnetron falls within the bandwidth of the frustum requires a bandwidth of at least 40 MHz, to allow for build tolerance and center frequency variations in the magnetron.  That in turn requires that the Q not exceed approximately 60.  Which in turn means that even if EmDrive is ‘real’, and thrust is proportional to Q and power (postulated) the likelihood of detecting thrust from a frustum with a Q of 60 is vanishingly small.  It also means that exciting a HIGH Q frustum designed for 2.45 GHz with a 2.45 GHz magnetron is ALSO very unlikely to produce measurable, repeatable thrust because of the small chance that a significant fraction of the output power will be centered in the bandwidth of the frustum and REMAIN there for the duration of the test run.  Variations in load as seen by the magnetron, the power supply, temperature, the frustum, and a host of other factors make it unlikely that even if thrust is detected on one or several runs, the data will be repeatable enough to be convincing to a sceptic. 

In other words, until a high Q frustum is tested with a stable, high power source whose frequency, power, and even output spectrum can be controlled at will, with wide enough frequency coverage to allow excitation at ALL resonant modes, it will not be possible, except for blind squirrel luck, to either confirm OR reject the existence of the generic EmDrive principle. 

Alternately, Dr. Rodal and the other theorists could finally torture the equations into confessing THEORETICAL thrust, at which point the equations can be turned into a frustum thruster design cookbook and we can all buy earlybird reduced fare tickets to Mars.

Offline TheTraveller

If a 'motion test' is needed...

...why not put the whole device, power supply and all, in a very small boat and test it in, say, a 'kiddie pool' or something similar?  That would be pretty dang close to frictionless, without the technical worries associated with the rotary test.

Very hard to collect data on that setup. Even harder to replicate test setups, test run per test run.

The idea of a test rig is to reduce unknows / things you can't control.

I hope to be able to achieve long term test runs that develop 1,000s of RPM from continual long term acceleration.
So you truly are following in Shawyer's footsteps.

The SPR rotary test rig had 5 cables connection the equipment on the table to the outside world and thus limiting rotation to a few turns.

I'll have no connections, a totally self contained system that can rotate and accelerate as long as the batteries last and the rotation stays stable.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline TheTraveller

Flyby posted this:.

‘I, fe, have a hard time believing that the Q will scale so linear as has been assumed, but I would gladly be proven wrong by an experiment that shows it can be done....”

And rfmwguy said this:

“
We have a unique opportunity to shove this thing along or simply prove its not possible. While I'd love to prove its real, I'd also feel accomplishment by showing the alternative, as we all should.
"


As I understand it, Shawyer’s premise all along has been that the EmDrive will produce useful thrust AND that the thrust is proportional to Q and power. 

I hope he is right, but I am not qualified to critique his theory.

I am also all for any and all DIY’ers who are building and testing their own systems to, hopefully, either confirm or reject the validity of the generic EmDrive phenomenon.

What I worry about is that none of the experiments that I have seen being proposed on the forum have much of a chance (my opinion) of doing either.

They propose building a frustum ‘to spec’ to use microwave oven magnetrons as drivers.  These magnetrons run at 2.45 GHz (nominally), produce a lot of power, are cheap, and readily available. 

So what is the problem?

Several. 

Let’s postulate that the design/build process actually produces a frustum with one of its many resonant frequencies centered at exactly 2.45 GHz.   Let us also postulate that Shawyer was right and that when excited at the proper mode the frustum produces thrust proportional to Q and power.  Fixed dimension frustums described on the forum resonate at multiple frequencies, each with its own ‘Q’.  Let us also postulate that excited at the optimum mode the frustum has a relatively modest Q of 5000.  That implies that the bandwidth at that mode is around 500 kHz. 

Oven magnetrons as described on this forum produce lots of power centered, more or less, at the nominal 2.45 GHz.  Unfortunately, the power is spread over 30+ MHz and is delivered at several distinct frequencies.  The specific frequencies of the spectral lines and the distribution of power among them vary with the load seen by the magnetron, variations in the power supply, the temperature, and, for all I know, the price of tea in China.  For the purpose of heating water or ruining meat in an oven, that is not important.  For the purpose of testing frustums, it is.

The magnetron CAN be ‘locked’ to an external standard, but the design of the phase lock circuitry is non-trivial.  Even when phase locked they cannot be tuned over a wide enough frequency range to explore the various resonant modes of the frustums.  From what I have read most or all of the DIY projects will use a free running magnetron.

Given the above, what are the chances that:

 
a.  The frustum, AS BUILT, will actually have a resonant mode at 2.45 GHz?
b.  Of the many resonant modes of the frustum the one that produces thrust will occur at 2.45 GHz?
c.  One of the spectral peaks in the magnetron output will occur at 2.45 GHz?
d.  The spectral line occurring at 2.45 GHz will contain an appreciable portion of the total magnetron output power?
e.  The DIY’er who designed and built the frustum will be able to answer any of the above by injecting the output of the magnetron into his frustum?

The magnetron is not easily tuned, so if the DIY’er doesn’t get super lucky and wind up with the predominant magnetron output spectral line occurring at the exact frequency required to excite the frustum in the mode that will produce thrust he (she, in the case of SeeShell) will be dead in the water.   None of the ‘features’ of the magnetron output are readily or, perhaps more importantly, precisely and repeatedly, controllable. 

What is more likely is that the magnetron will perform as advertised, the frustum will develop hot spots in a pattern that can be analyzed by Dr. Rodal or others to determine the mode which was established, little or no thrust will be detected (even if Shawyer IS right), and the arguments and second guessing re the test procedures, whether the frustum needs to be ‘vibrated’, whether it could accelerate freely enough, whether the output spectrum was optimum, etc. will continue ad infinitum.  And that is with EmDrive thrust proportional to Q and power POSTULATED to be valid. 

To guarantee that output of the magnetron falls within the bandwidth of the frustum requires a bandwidth of at least 40 MHz, to allow for build tolerance and center frequency variations in the magnetron.  That in turn requires that the Q not exceed approximately 60.  Which in turn means that even if EmDrive is ‘real’, and thrust is proportional to Q and power (postulated) the likelihood of detecting thrust from a frustum with a Q of 60 is vanishingly small.  It also means that exciting a HIGH Q frustum designed for 2.45 GHz with a 2.45 GHz magnetron is ALSO very unlikely to produce measurable, repeatable thrust because of the small chance that a significant fraction of the output power will be centered in the bandwidth of the frustum and REMAIN there for the duration of the test run.  Variations in load as seen by the magnetron, the power supply, temperature, the frustum, and a host of other factors make it unlikely that even if thrust is detected on one or several runs, the data will be repeatable enough to be convincing to a sceptic. 

In other words, until a high Q frustum is tested with a stable, high power source whose frequency, power, and even output spectrum can be controlled at will, with wide enough frequency coverage to allow excitation at ALL resonant modes, it will not be possible, except for blind squirrel luck, to either confirm OR reject the existence of the generic EmDrive principle. 

Alternately, Dr. Rodal and the other theorists could finally torture the equations into confessing THEORETICAL thrust, at which point the equations can be turned into a frustum thruster design cookbook and we can all buy earlybird reduced fare tickets to Mars.

I concluded quite some time ago magnetrons are not the pathway for DIY builds, for all the reasons you mentioned.

My design is very high Q, aiming for at least 100,000. Rf source is programmable in 1kHz steps. 20W Rf amp then drives the cavity via an isolator.

My EMDrive Calculator, developed with assistance from Roger Shawyer, makes designing the cavity fairly easy.

With the ability to have a very narrow band Rf generator that allows frequency modification, simple to then find the cavity resonant frequency for Shawyer's recommended TE013 mode.

I expect the spreadsheet indicated resonant TE013 frequency to be very close to the actual operational frequency.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
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Offline ThinkerX

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Quote
If a 'motion test' is needed...

...why not put the whole device, power supply and all, in a very small boat and test it in, say, a 'kiddie pool' or something similar?  That would be pretty dang close to frictionless, without the technical worries associated with the rotary test.

Quote
Very hard to collect data on that setup. Even harder to replicate test setups, test run per test run.

The idea of a test rig is to reduce unknows / things you can't control.

I hope to be able to achieve long term test runs that develop 1,000s of RPM from continual long term acceleration.

Possibly you missed the 'technical worries' comment in my post.  Both Shawyer's rotary test and the Baby EM rotary test show very high noise to signal ratio's, something commented on by multiple posters in this thread (Rodal and SeaShells among others - and SeaShells has substantial experience with such systems)

A 'boat test,' though, is much simpler.  It either moves or it does not, thus testing Shawyer's claim that a vertical/balance test is doomed to failure, minus the distinctive noise associated with rotary tests. 



« Last Edit: 07/08/2015 05:16 AM by ThinkerX »

Offline TheTraveller

Quote
If a 'motion test' is needed...

...why not put the whole device, power supply and all, in a very small boat and test it in, say, a 'kiddie pool' or something similar?  That would be pretty dang close to frictionless, without the technical worries associated with the rotary test.

Quote
Very hard to collect data on that setup. Even harder to replicate test setups, test run per test run.

The idea of a test rig is to reduce unknows / things you can't control.

I hope to be able to achieve long term test runs that develop 1,000s of RPM from continual long term acceleration.

Possibly you missed the 'technical worries' comment in my post.  Both Shawyer's rotary test and the Baby EM rotary test show very high noise to signal ratio's, something commented on by multiple posters in this thread (Rodal and SeaShells among others - and SeaShells has substantial experience with such systems)

A 'boat test,' though, is much simpler.  It either moves or it does not, thus testing Shawyer's claim that a horizontal test is doomed to failure, minus the distinctive noise associated with rotary tests.

The SPR rotary test rig had high noise to signal ratio?? Where did that come from? You have data I don't have?

BTW if you had read the associated test notes you would have learned the high audio noise level in the video was produced by the air compressor feeding the rotary air bearing.

http://www.emdrive.com/testnotes.pdf

I'm not using an air bearing, just a simple magnetic thrust bearing with 2 other low friction/stiction bearings.

My test rig will be very quite, just the sound of the table rotating/acceleration from the EMDrive generated Force/Torque.
« Last Edit: 07/08/2015 05:20 AM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline deltaMass

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Erm, audio noise was not what was being indicated by ThinkerX.

BTW, what is Shawyer's record RPM value and do you think you can beat it?
« Last Edit: 07/08/2015 05:26 AM by deltaMass »

Offline ThinkerX

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The SPR rotary test rig had high noise to signal ratio?? Where did that come from? You have data I don't have?

You somehow missed two or three pages of in depth discussion on the topic?  Rodal posted a copy of Shawyer's video with attendant comments, mostly about continued acceleration when off.  Other posters commented on how much or all of the thrust seemed to come from a 'ratcheting effect.'  SeaShells gave what amounted to a miniature paper on the problems inherit with air bearings.  Somebody else pointed out they saw a fan on the mechanism (I didn't, but my eyes are not the best anymore. 
 
Quote
I'm not using an air bearing, just a simple magnetic thrust bearing with 2 other low friction/stiction bearings.

To me, this sounds very much like the setup used to detect thrust for the Baby EM Drive.  Again, there was extensive commentary about a high noise to signal ratio.

With the boat test...no finicky air bearing, no magnetic bearing causing interference, just water. 

(Got to thinking along these lines a few weeks ago when I was at a lake, watching a 2-3 year old toddler pushing a boat around in shallow water without difficulty.  On land, he couldn't have budged the boat period, but in the lake, he just gave it a little shove and away it went.)

Offline TheTraveller

Erm, audio noise was not what was being indicated by ThinkerX.

BTW, what is Shawyer's record RPM value and do you think you can beat it?

Roger told me max was 2 RPM due to cords.

Easy to beat as my rotary test setup has no cords and can accelerate until the batts die or it becomes unstable.

Attached are the published Demonstrator EMDrive static and rotary test results.

BTW SPR never hid the fact that after they switched off the cooling system, when they switched off the magnetron, they had some KE in the coolant loops transfer to rotary KE.

Might have been better to allow the rotation to stop before stopping the coolant flow as then it would have been constant coolant circulation pre, during and post rotation.
« Last Edit: 07/08/2015 05:47 AM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline WarpTech

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Dumb question alert - so linear acceleration dimishes with time? If so, at what rate of decay?

Acceleration is proportional to (1/M)*dM/dt. It is either gaining or losing mass to accelerate. The same applies to a photon rocket, or a chemical rocket. At no time will the kinetic energy exceed the total delta-Mass x c^2.
Todd
In effect, not a propellantless thruster?

I didn't say that. Look at my equation. There are 2 terms for dm/dt. The second one does not need to expel anything. It just needs to drop from the small end to the big end.
Todd

Offline TheTraveller

Quote
The SPR rotary test rig had high noise to signal ratio?? Where did that come from? You have data I don't have?

You somehow missed two or three pages of in depth discussion on the topic?  Rodal posted a copy of Shawyer's video with attendant comments, mostly about continued acceleration when off.  Other posters commented on how much or all of the thrust seemed to come from a 'ratcheting effect.'  SeaShells gave what amounted to a miniature paper on the problems inherit with air bearings.  Somebody else pointed out they saw a fan on the mechanism (I didn't, but my eyes are not the best anymore. 
 
Quote
I'm not using an air bearing, just a simple magnetic thrust bearing with 2 other low friction/stiction bearings.

To me, this sounds very much like the setup used to detect thrust for the Baby EM Drive.  Again, there was extensive commentary about a high noise to signal ratio.

With the boat test...no finicky air bearing, no magnetic bearing causing interference, just water. 

(Got to thinking along these lines a few weeks ago when I was at a lake, watching a 2-3 year old toddler pushing a boat around in shallow water without difficulty.  On land, he couldn't have budged the boat period, but in the lake, he just gave it a little shove and away it went.)

Must have happened when I was in hospital or in drugged state. Never saw it.

Seems you never saw my drawing either? It is nothing like the Baby EMDrive test rig.

All the various items CG are the same distance from the centre.

All the various items are covered by a transparent cover to give very low and symmetrical wind resistance.
« Last Edit: 07/08/2015 06:10 AM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline ThinkerX

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Seems you never saw my drawing? It is nothing like the Baby EMDrive test rig.

All the various items CG are the same distance from the centre.

All the various items are covered by a transparent cover to give very low and symmetrical wind resistance

A drawing is one thing.  A physical device is something else.

Now...NOT an attack, but an expression of concern:

Shawyer gets high marks in my book as far as the EM Drive goes.  It was his concept, he holds patents, he built several physical test rigs with results that were interesting. 

My issue is this:

Shawyers published test results seem very roughly comparable to those of EW or the Chinese - interesting, but with a fair degree of noise level.  No vacuum tests (a critical point).  Still, something that might be refined into keeping satellites in place or maybe interplanetary probes, once developed a bit more.

Instead, WITHOUT supporting physical evidence, Shawyer and yourself seem to be jumping straight from those early results into 'flying car' territory.  By 'physical evidence,' I mean a functional device producing that kind of thrust that can be replicated elsewhere without involvement from Shawyer.  Instead, we get word that his 2014 paper has been peer reviewed and accepted for publication.  Not good enough.  'Peer reviewed,' especially with extraordinary or controversial claims, does not equal 'fact.'  It might mean more people are taking Shawyers work seriously. 

Now here, on the other hand, we have an assortment of very bright people with a wide range of knowledge and experience tackling this problem step by step, attempting to avoid preconceived notions along the way.  Going where actual, repeatable, verifiable evidence leads, considering different explanations for said evidence.  And most importantly, doing so publically.   

 








Offline Chrochne

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Seems you never saw my drawing? It is nothing like the Baby EMDrive test rig.

All the various items CG are the same distance from the centre.

All the various items are covered by a transparent cover to give very low and symmetrical wind resistance

A drawing is one thing.  A physical device is something else.

Now...NOT an attack, but an expression of concern:

Shawyer gets high marks in my book as far as the EM Drive goes.  It was his concept, he holds patents, he built several physical test rigs with results that were interesting. 

My issue is this:

Shawyers published test results seem very roughly comparable to those of EW or the Chinese - interesting, but with a fair degree of noise level.  No vacuum tests (a critical point).  Still, something that might be refined into keeping satellites in place or maybe interplanetary probes, once developed a bit more.

Instead, WITHOUT supporting physical evidence, Shawyer and yourself seem to be jumping straight from those early results into 'flying car' territory.  By 'physical evidence,' I mean a functional device producing that kind of thrust that can be replicated elsewhere without involvement from Shawyer.  Instead, we get word that his 2014 paper has been peer reviewed and accepted for publication.  Not good enough.  'Peer reviewed,' especially with extraordinary or controversial claims, does not equal 'fact.'  It might mean more people are taking Shawyers work seriously. 

Now here, on the other hand, we have an assortment of very bright people with a wide range of knowledge and experience tackling this problem step by step, attempting to avoid preconceived notions along the way.  Going where actual, repeatable, verifiable evidence leads, considering different explanations for said evidence.  And most importantly, doing so publically.

I like this approach Mr. ThinkerX . It can boost the credibility of this project. That evidence is definitely needed.

But I also like to see the enthusiasm. It is good to be enthusiast as it gives you incredible energy to go on! Now I really can not wait for papers from NASA and Mr. Shawyer. Just one working EmDrive of second generations would do wonders...not to mention the income generated by investors for further research.

Offline deltaMass

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I see that Shawyer's "latest paper"  8)  contains a specification of 2/3 N/W. This corresponds to a breakeven velocity of 3 m/s, mechanically an easily attainable value. Can we therefore expect Shawyer to branch out into the power generation field in the near future?
Just a little follow-up here to answer a question that some may be asking: "What is a reasonable value of Newtons/Watt such that overunity could be achieved with a rotary device in a terrestrial lab?"

It's a mechanical limitation. An aggressive spec. is something like 1,000 gee with a 1 metre radius arm. That's about 1,000 rpm and a tangential velocity of about 100 m/s. That in turn calls for a minimum k-value of
0.02 N/W.
Keep that figure in mind.
@kdhilliard has been kind enough to point out to me that the correct figure here should be 0.01 N/W, because the power breakeven velocity is what's important from a practical point of view. To recap:
Energy breakeven velocity = 2/k
Power breakeven velocity = 1/k

The power breakeven proof is not difficult:
Pout = d/dt(0.5 m v2) = m v a = Pin when v := vp
So vp = Pin / (m a) = Pin / F = Pin / (k Pin) = 1/k
QED

Offline Possibles

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Some interesting reading.

"Extraordinary momentum and spin in evanescent
waves"

http://dml.riken.jp/pdf/ncomms4300rr.pdf

« Last Edit: 07/08/2015 09:33 AM by Possibles »

Offline Rodal

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...

All the various items are covered by a transparent cover to give very low and symmetrical wind resistance.
Are you going to have a vacuum inside the transparent cover?
If the answer is no, the initially static air has its own inertia and will resist being moved and rotated, it will be moved by the no-slip condition at the boundary with the rotating solid objects, and dragged by its viscosity mainly at the boundary layer.  This will still produce fluid mechanics effects, including vortices and aerodynamic drag (what you call "wind resistance) inside the cover until a steady-state is achieved.
« Last Edit: 07/08/2015 09:46 AM by Rodal »

Offline SeeShells

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Some interesting reading.

"Extraordinary momentum and spin in evanescent
waves"

http://dml.riken.jp/pdf/ncomms4300rr.pdf

I know, I liked that paper as it was very well done and connecting flags all over it.

The rest of this post isn't about your post it's just me stomping my feet and saying grrr. ;)

I've been accused of bonehead thoughts that cause the physicists to curl their toes, well good, you need that, it makes you think!  40 some years as an engineer gave me an advantage to see patterns and link things that are seemingly unrelated. It could be in building the next best doodad or wingwang or taking a physicist's papers with chicken scratchings, understanding them, making them work, or refining them to something better, or curling my toes and saying what a bonehead idea. 

When I see something that just seems to work or connect from both sides of the thought table I throw it on this blog, so curl your toes or just think I'm throwing you a bone to chew on. There is no such thing as a bad idea, unless it involves beer and guns.

Like the paper you linked or (read it several time before) or
http://arxiv.org/abs/gr-qc/9906084
On the relation between a zero-point-field-induced inertial effect and the Einstein-de Broglie formula
or
Superluminal Behaviors of Electromagnetic Near-fields
or...or
I've close to 20 papers that say there is a connection in what we just don't quite understand happening in this device that makes it do what it does and but I think it does something extraordinary.

Here I am building something that a dozen theories exist about, no real solid formulas, no solid theoretical design posts, oh, will a stabilized RF source make a difference, or will a higher frequency, or different cavity shape, or hanging it with a rope from the rafters, filling it with jello? I'll do the best I can with the little I have (sounds like NASA by wishing I had just a little more funds than my social Security ;) ) with half baked theories that make me curl my toes too.

Shell

PS: I try to post some pics...

Offline mwvp

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...
They propose building a frustum ‘to spec’ to use microwave oven magnetrons as drivers.  These magnetrons run at 2.45 GHz (nominally), produce a lot of power, are cheap, and readily available. 

So what is the problem?

Several. 
...
Fixed dimension frustums described on the forum resonate at multiple frequencies, each with its own ‘Q’.
...
Oven magnetrons as described on this forum produce lots of power centered, more or less, at the nominal 2.45 GHz.  Unfortunately, the power is spread over 30+ MHz and is delivered at several distinct frequencies.  The specific frequencies of the spectral lines and the distribution of power among them vary with the load seen by the magnetron, variations in the power supply, the temperature, and, for all I know, the price of tea in China.
...
The magnetron CAN be ‘locked’ to an external standard, but the design of the phase lock circuitry is non-trivial.  Even when phase locked they cannot be tuned over a wide enough frequency range to explore the various resonant modes of the frustums.  From what I have read most or all of the DIY projects will use a free running magnetron.

Did you have a look at, "IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 52, NO. 9, SEPTEMBER 2005, Noise Performance of Frequency- and Phase-Locked CW Magnetrons Operated as Current-Controlled Oscillators, Imran Tahir, Amos Dexter, and Richard Carter, Senior Member, IEEE"

Someone here linked to it. It also points out magnetrons can be "pulled" by a tuned load, which fits with other info I've read. They are negative-resistance oscillators, which will obligingly (for good or ill) lock onto the frequency of the network they are connected to.

Given the above, what are the chances that:

 
a.  The frustum, AS BUILT, will actually have a resonant mode at 2.45 GHz?

Put a tuning slug on your frustrum to tune it to the magnetron.

b.  Of the many resonant modes of the frustum the one that produces thrust will occur at 2.45 GHz?

Tune your frustrum.

c.  One of the spectral peaks in the magnetron output will occur at 2.45 GHz?

It may work anyways, and has according to Shawyer and NWPU

The magnetron is not easily tuned, so if the DIY’er doesn’t get super lucky and wind up with the predominant magnetron output spectral line occurring at the exact frequency required to excite the frustum in the mode that will produce thrust he (she, in the case of SeeShell) will be dead in the water.   None of the ‘features’ of the magnetron output are readily or, perhaps more importantly, precisely and repeatedly, controllable. 

When Iullian "published" his results, I shared your above sentiments. Oh, did I mention tuning the frustrum to the magnetron?

And, don't forget the magnetron-ist may cook and/or electrocuting themselves, their pets, and blowing everyone off wifi and cellphones for blocks around, attracting the attention of "Uncle Charlie" (fcc).

What is more likely is...the arguments and second guessing re the test procedures, whether the frustum needs to be ‘vibrated’, whether it could accelerate freely enough, whether the output spectrum was optimum, etc. will continue ad infinitum.

Lol. That's gunna happen anyways.

even if EmDrive is ‘real’, and thrust is proportional to Q and power (postulated) the likelihood of detecting thrust from a frustum with a Q of 60 is vanishingly small.

According to Shawyer and NWPU, not so. Perhaps those without experience in radio/radar will have a vanishingly small chance of making it work.

Variations in load as seen by the magnetron, the power supply, temperature, the frustum, and a host of other factors make it unlikely that even if thrust is detected on one or several runs, the data will be repeatable enough to be convincing to a sceptic. 

A sceptic will not be convinced until said device flies up their waveguide  ;D
So what.

In other words, until a high Q frustum is tested with a stable, high power source whose frequency, power, and even output spectrum can be controlled at will, with wide enough frequency coverage to allow excitation at ALL resonant modes, it will not be possible, except for blind squirrel luck, to either confirm OR reject the existence of the generic EmDrive principle. 

I share your concerns, but disagree. The competent experimenter may tune their frustrum, even auto-tune it with AFC if they're clever, to the magnetron. My understanding is both Shawyer and NWPU have done so.

There are some good things to be said for magnetrons. They are high-power, they're tubes - no ESD sensitivity, and can take abuse/vswr that will destroy expensive solid-state amplifiers.

I looked at some 2.5 GHz power transistors on Digikey yesterday. Several hundred bucks. I don't feel lucky. If the flux moves me, I'd try using a magnetron and detect palpable force levels before trying to detect uN forces with cheap amps or risk VSWR destroying a solid-state power amp. Unless the government was paying for it  ;D

Offline SeeShells

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@rfmwguy
Excellent 👍:D

Offline Possibles

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@ Shell.

I feel the same way. Although I have no resources to physically check things out myself nor your experience as an engineer, everything I have read and investigated brings me to the conclusion that there is something we are missing here. There are too many seemingly related threads that point to there being really something special to discover. You can almost taste it. And from my experience this doesnt tend to happen with bad ideas. Something is definitely going on.

It's just that finding that damn thing is the difficult bit.

Offline SeeShells

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@ Shell.

I feel the same way. Although I have no resources to physically check things out myself nor your experience as an engineer, everything I have read and investigated brings me to the conclusion that there is something we are missing here. There are too many seemingly related threads that point to there being really something special to discover. You can almost taste it. And from my experience this doesnt tend to happen with bad ideas. Something is definitely going on.

It's just that finding that damn thing is the difficult bit.
Well dang it thank you!
One of my favorite books was https://en.wikipedia.org/wiki/The_Mote_in_God's_Eye
They talked about "The Crazy Eddie Drive" and sometimes I begin to feel this is "The Crazy DYI Drive". :D

I have no doubt with the great minds here and those sitting in silence until a time comes to speak up, it will be solved.

Shell


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