Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2107688 times)

Offline Voidman2015

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Greetings,

I am currently playing catchup (page 151), so my apologies if this has already been talked about. My question is how is the acceleration witness from the emdrive different from the Pioneer anomaly? Full disclosure time; I am not a scientist, but I am a fan of physics.  Thank you for the great conversations on this forum.
http://en.m.wikipedia.org/wiki/Pioneer_anomaly


Offline Rodal

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Greetings,

I am currently playing catchup (page 151), so my apologies if this has already been talked about. My question is how is the acceleration witness from the emdrive different from the Pioneer anomaly? Full disclosure time; I am not a scientist, but I am a fan of physics.  Thank you for the great conversations on this forum.
http://en.m.wikipedia.org/wiki/Pioneer_anomaly
Hi and welcome,

The Pioneer anomaly effect (due to radiation of heat) is an extremely small acceleration of (8.74±1.33)×10^(−10) m/s^2, which is equivalent to slowly accelerating to a velocity of 1 kilometre per hour (0.6 mph) over a period of ten years.

Thus, it is ~thousands of times smaller than the acceleration researchers claim in the EM Drive experiments.
« Last Edit: 05/21/2015 02:05 PM by Rodal »

Offline Voidman2015

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Rodal, thank you for the clarification. I am looking forward to reading more on this wonderful discussion. One quick stupid question: would not the shape of the cavity and the concentration of radiation in the cavity account for the higher acceleration reported? Or am I just way off?

Thank you again.

Offline OttO

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Stumbled on this one:

http://arxiv.org/abs/1503.06334

I think it can interest @Aero


Offline Rodal

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Stumbled on this one:

http://arxiv.org/abs/1503.06334

I think it can interest @Aero
Thanks.

For more background, see the following http://en.wikipedia.org/wiki/Faster-than-light#Faster_light_.28Casimir_vacuum_and_quantum_tunnelling.29 which discusses the work by  Guenter Nimtz,  author of the article

This is a quote from that section of the Wiki article:

Quote
They say they have conducted an experiment in which microwave photons—relatively low energy packets of light—travelled "instantaneously" between a pair of prisms that had been moved up to 3 ft (1 m) apart. Their experiment involved an optical phenomenon known as "evanescent modes", and they claim that since evanescent modes have an imaginary wave number, they represent a "mathematical analogy" to quantum tunnelling.[32] Nimtz has also claimed that "evanescent modes are not fully describable by the Maxwell equations and quantum mechanics have to be taken into consideration."[48] Other scientists such as Herbert G. Winful and Robert Helling have argued that in fact there is nothing quantum-mechanical about Nimtz's experiments, and that the results can be fully predicted by the equations of classical electromagnetism (Maxwell's equations).[49][50]

Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of." However, other physicists say that this phenomenon does not allow information to be transmitted faster than light. Aephraim Steinberg, a quantum optics expert at the University of Toronto, Canada, uses the analogy of a train traveling from Chicago to New York, but dropping off train cars at each station along the way, so that the center of the ever shrinking main train moves forward at each stop; in this way, the speed of the center of the train exceeds the speed of any of the individual cars.[51]
« Last Edit: 05/21/2015 03:01 PM by Rodal »

Offline OttO

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I try to follow this thread from the beginning and I must thanks all the people posting here.
From my side the reality of the thrust is not the most important. What is important is the things I learned here.

I shall confess that the majority of the stuff is way off my poor head.

@rodal thank you for the link :-) I will try it...
You asked an interesting question a while ago, what is peculiar about copper frustum?
Well I think that the mirrors are interesting.

Would it be silly to think of a kind of Hawking radiation to "deflate" the frustum?

Offline Rodal

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...Would it be silly to think of a kind of Hawking radiation to "deflate" the frustum?
McCulloch's explanation ( http://www.ptep-online.com/index_files/2015/PP-40-15.PDF ) is essentially akin to Hawking radiation, as Unruh radiation is akin to Hawking radiation
« Last Edit: 05/21/2015 03:02 PM by Rodal »

Offline TheTraveller

As a sanity check, what is the mode shape you predict for the above "resonance" calculation ?

Do you predict resonance at a Transverse Magnetic or Transverse Electric mode ?
what are the predicted mode shape quantum number m,n,p values ?

TMmnp  ?
TEmnp   ?

Thanks

Roger's bread crumb:

Quote
You need to develop a numerical model that calculates the guide wavelength, for the chosen mode, at discrete small increments along the cavity length and then integrate them into an effective wavelength for the whole cavity.

Which I followed and used the guide wavelengths, generated from the Df equation, at 1,000 equally spaced diameter points between and including the end plates.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline rfmwguy

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...Would it be silly to think of a kind of Hawking radiation to "deflate" the frustum?
McCulloch's explanation ( http://www.ptep-online.com/index_files/2015/PP-40-15.PDF ) is essentially akin to Hawking radiation, as Unruh radiation is akin to Hawking radiation

Thanks Doc... had not read this pdf. Helps unravel some of the theory for my practical, non-theoretical physics mind. I had actually been thinking about a non-frustum shape previously and there it was in this paper:

"The effect could be increased by increasing the degree of taper, for example using a pointed cone."

OK, I know what you're thinking...pointed cone...pointed rectangle...pyramid...So, perhaps I should add a Pyramid to my Die Glocke-shaped frustrum fears  ;)

Offline Rodal

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Rodal, thank you for the clarification. I am looking forward to reading more on this wonderful discussion. One quick stupid question: would not the shape of the cavity and the concentration of radiation in the cavity account for the higher acceleration reported? Or am I just way off?

Thank you again.
The Pioneer anomaly acceleration is towards the Sun, with the radiated heat (T1) occurring away from the Sun, at the back of the Pioneer probe facing the Sun.  The temperature (T2) around the EM Drive experiments (+68 F (+20 C)?) is much warmer than the background temperature (T2) at the back of the Pioneer probe (- 292 F (-180 C) around Saturn, for example).  The radiative heat transfer goes like the difference of the (absolute) temperatures to the fourth power:

« Last Edit: 05/21/2015 04:06 PM by Rodal »

Offline Rodal

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As a sanity check, what is the mode shape you predict for the above "resonance" calculation ?

Do you predict resonance at a Transverse Magnetic or Transverse Electric mode ?
what are the predicted mode shape quantum number m,n,p values ?

TMmnp  ?
TEmnp   ?

Thanks

Roger's bread crumb:

Quote
You need to develop a numerical model that calculates the guide wavelength, for the chosen mode, at discrete small increments along the cavity length and then integrate them into an effective wavelength for the whole cavity.

Which I followed and used the guide wavelengths, generated from the Df equation, at 1,000 equally spaced diameter points between and including the end plates.
In other words, I understand that you have developed a spreadsheet model predicting the correct geometry for resonance to occur at, but that you cannot predict whether the resonance occurs in a Transverse Magnetic mode, or a Transverse Electric mode, and that you cannot predict what is the resonance mode shape variation (m. n, p numberrs) in the longitudinal, transverse and azimuthal directions of the truncated cone.

Therefore we cannot check whether your ("Roger's bread crumb" ?) predicted resonance is correct.   :(
« Last Edit: 05/21/2015 03:55 PM by Rodal »

Offline hhexo

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McCulloch's explanation ( http://www.ptep-online.com/index_files/2015/PP-40-15.PDF ) is essentially akin to Hawking radiation, as Unruh radiation is akin to Hawking radiation

Hm... I read McCulloch's paper and it seems quite interesting, although the maths is again too much for me.
However, by following links and expanding the range of the bibliography I happened upon this: http://arxiv.org/abs/1105.4714
Yet again, too much maths, but it got me thinking.

The dynamic Casimir effect happens when an EM mirror moves at relativistic speed, and results in photon production in a narrow band.
Now, we know that the two plates in the EmDrive do not move. However, the plates are EM mirrors because of a "sea" of electron quantum states, which change when a wave hits the plate and is reflected. Could it be that the distribution of quantum states is somehow "oscillating" because of the resonance? Could this affect reflection in a "cycle"? In this case, we would have an "oscillating mirror" at each plate. There could be asymmetry factors (e.g. difference in plate size, or different "oscillation frequency") that cause an imbalance of dynamic Casimir effects between the two plates, leading to unbalanced photon production and net thrust.
(so, the net thrust from Maxwell's equations would be zero, but the high values for the oscillation of the EM field causing oscillations in the material's quantum states would create situations where Casimir effects are measurable)
(also, in the case of a dielectric the "mirror" might oscillate more?)

The first counter-argument to my own theory I can think of is that resonance is akin to a "standing wave" so there shouldn't be any oscillation at the boundary nodes. But reality might be more complex than that.
The second counter-argument to this hypothesis is that Casimir effects are minuscule and shouldn't be macroscopic. But I haven't even tried to run the numbers.

Also, I can't do the maths to do a proper derivation of any equation for this. :(

Please debunk me! :)

Offline WarpTech

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Warptech

Just had another look and your right.. jockey shorts.. laughing.

The iris idea is good.
Two counter rotating disks with circular holes could achieve the same thing at higher speed and minimal mechanical effort, better reliability.  My experience with sliding mechanical objects has usually not been that good over a reasonable time.... just saying.


I have been thinking about the cavity-resonance element of the em thruster.
I may be totally wrong but I strongly suspect there is far more than just em photons bouncing around inside a tin-can happening. The wave fronts momentum "could"? have a part to play in it but I am pursuing the trail of increased-energy-level confined to a small area, and the non-traditional events that may arise. My conjecture is that the Shawyer em-drive is in a very-mild way (at present power levels) interacting/distorting/impacting/modifying/???? space-time and hence its partner, Gravity, on a local level. If or when power levels ramp up to "considerable" watts.. we might see unusual things emerge in the environment immediately around the drive. 

The internal wavefronts inside the drive might somehow be helping to alternately create and then distort the shape and location of a G-modification?.

If the guys at NASA are reading this, are you able to up-the-watts, and test for G-modification not just inside but also around the device??.  {please santa}

I dont have any proof to support my conjecture....yet

I have a similar conjecture, but IMO it "mimics" gravity. The effect is not caused by a massive planet or high energy density however. It is caused by the attenuation of the wave due to the "effective mass" imposed on photons by the waveguide cut-off aperture. Go back and read some of my earlier posts, when I was working all this out for the 1st time.

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1369287#msg1369287

Todd

Offline SeeShells

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As a sanity check, what is the mode shape you predict for the above "resonance" calculation ?

Do you predict resonance at a Transverse Magnetic or Transverse Electric mode ?
what are the predicted mode shape quantum number m,n,p values ?

TMmnp  ?
TEmnp   ?

Thanks

Roger's bread crumb:

Quote
You need to develop a numerical model that calculates the guide wavelength, for the chosen mode, at discrete small increments along the cavity length and then integrate them into an effective wavelength for the whole cavity.

Which I followed and used the guide wavelengths, generated from the Df equation, at 1,000 equally spaced diameter points between and including the end plates.
In other words, I understand that you have developed a spreadsheet model predicting the correct geometry for resonance to occur at, but that you cannot predict whether the resonance occurs in a Transverse Magnetic mode, or a Transverse Electric mode, and that you cannot predict what is the resonance mode shape variation (m. n, p numberrs) in the longitudinal, transverse and azimuthal directions of the truncated cone.

Therefore we cannot check whether your ("Roger's bread crumb" ?) predicted resonance is correct.   :(
Please doc this is just a simple question, but why would absolute dimensional numbers be so important as long as you're in the ballpark for resonance? I think every device I've seen has taken into account that either you mechanically tune the EM cavity or shift the insertion frequency to optimize the thrust.
I've even thought of using a airtight Conductive Elastic Fabric on the endplate and varying the air pressure the chamber to optimize the reflected EM wave.

Offline aero

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Quote
I've even thought of using a airtight Conductive Elastic Fabric on the endplate and varying the air pressure the chamber to optimize the reflected EM wave.

Now that's an interesting idea. Do you have data showing a variation in magnetic permeability of air at different pressures?
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Offline Rodal

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...
Please doc this is just a simple question, but why would absolute dimensional numbers be so important as long as you're in the ballpark for resonance? I think every device I've seen has taken into account that either you mechanically tune the EM cavity or shift the insertion frequency to optimize the thrust.
I've even thought of using a airtight Conductive Elastic Fabric on the endplate and varying the air pressure the chamber to optimize the reflected EM wave.
Since whether the EM Drive "thrust" is an experimental artifact or whether it is something that can be used for space propulsion (and if so, what is its theoretical justification) is still unsettled, most issues, like whether it is good enough to be in the ballpark for resonance are very much a subject of debate.

If one assumes (as Shawyer appears to do) that the higher the Q the better, then it appears that one does want to be at the resonant peak, since as you know the higher the Q the narrower the bandwidth for such resonant peak. 

On the other hand, we have:

1) the beautiful theory being developed by Todd (WarpTech) that one may not want maximum Q
2) the experimental evidence from Prof. Yang achieving the highest thrust measured at Q's (when transformed such that they are calculated the same way as in the West) lower than Shawyer reported Q's
3) the experimental evidence from NASA Eagleworks showing that highest thrust is not one-to-one monotonically associated with highest Q
4) although Shawyer has been working on a superconducting EM Drive with a huge Q, no thrust values from such a device have been reported by Shawyer (who is in the process of being protected by his patent application for a superconducting EM Drive)
5) the superconducting Cannae drive achieved only milliNewtons and the test has been criticized earlier in the thread as being anomalous,  Cannae appeared to have shifted his attention to non-superconducting drives after that experiment (?)

Now, it is my understanding that TheTraveller is going through the trouble to calculate resonance following Shawyer's approach, based on achieving highest Q, which implies having to be at the resonant peak.

We also know from NASA Eagleworks that thrust is very much associated with particular mode shapes.  Notsosureofit's prediction formula is also dependent on mode shapes.

Thus, it appears that to understand the experimental reports one needs to assess what are the mode shapes involved.

Since I am skeptical of the derivation of TheTraveller's Shawye's resonance calculation (I am from Missouri: show me  :) ) the only way I have to verify it is by comparing the mode shapes to the exact solution (which would also be useful in its own right, as per NASA and Notsosureofit).   Since many mode shapes are bunched together at close frequencies, one cannot determine whether a natural frequency prediction is correct unless one assesses the mode shape prediction.
« Last Edit: 05/21/2015 05:16 PM by Rodal »

Offline aero

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Following Roger Shawyers kindly laid bread crumb trail, my EM Drive spreadsheet now can calc the effective internal guide wavelength and external Rf wavelength that will give resonance from end plate to end plate.

As an example for the Flight Thruster big and small end diameters as below, the required end plate to end plate spacing to achieve resonance with an external Rf of 3.85GHz is as below.

Alteration of either the big, small end or Rf frequency will now automatically generate a new Df and from that the end plate spacing needed to achieve resonance with the external Rf.

big diameter      m   0.2440000
small diameter   m   0.1450000
cavity length      m   0.1603484
rf frequency       Hz   3,850,000,000
Calculated Df      Df   0.49094
slant angle        Deg   28.8

1,000 point numerically integrated guide wavelength of the above example is: 0.0801741816

I will publish the spreadsheet but would 1st like to run / verify it against other frustum dimensions and what the calculated / measured resultant resonance was and in what mode.

With this spreadsheet if we know either end diameter, Rf frequency and Df, the other diameter and spacing can now be determined as all 3 dimensions and external Rf wavelength (4 variables) affect each other.

NEXT STEPS:

1) Determine the best way to inject the coax Rf into the Flight Thruster? Loop or Stub?

2) Determine the best location to inject the Rf into the Flight Thruster?

3) Determine the best way to impedance match the Flight Thruster to the impedance of the Rf generator so as to get optimal VSWR and energy delivery to inside the Flight Thruster?

Very interesting. Now I would like to see a comparison of cavity dimensions vs. drive frequency with the dimensions expressed in units of drive frequency wavelength. That is because it is very easy to model a the cavity using wavelength as the unit of length and it would be so nice to be able to conveniently change the drive frequency if I knew how the cavity dimensions changed with drive frequency wavelength.

« Last Edit: 05/21/2015 04:58 PM by aero »
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Offline aero

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Greetings,

I am currently playing catchup (page 151), so my apologies if this has already been talked about. My question is how is the acceleration witness from the emdrive different from the Pioneer anomaly? Full disclosure time; I am not a scientist, but I am a fan of physics.  Thank you for the great conversations on this forum.
http://en.m.wikipedia.org/wiki/Pioneer_anomaly

Welcome - This thread is growing so fast that we're all playing catchup. It's almost a full time job just to keep up with the thread.
Retired, working interesting problems

Offline TheTraveller

As a sanity check, what is the mode shape you predict for the above "resonance" calculation ?

Do you predict resonance at a Transverse Magnetic or Transverse Electric mode ?
what are the predicted mode shape quantum number m,n,p values ?

TMmnp  ?
TEmnp   ?

Thanks

Roger's bread crumb:

Quote
You need to develop a numerical model that calculates the guide wavelength, for the chosen mode, at discrete small increments along the cavity length and then integrate them into an effective wavelength for the whole cavity.

Which I followed and used the guide wavelengths, generated from the Df equation, at 1,000 equally spaced diameter points between and including the end plates.
In other words, I understand that you have developed a spreadsheet model predicting the correct geometry for resonance to occur at, but that you cannot predict whether the resonance occurs in a Transverse Magnetic mode, or a Transverse Electric mode, and that you cannot predict what is the resonance mode shape variation (m. n, p numberrs) in the longitudinal, transverse and azimuthal directions of the truncated cone.

Therefore we cannot check whether your ("Roger's bread crumb" ?) predicted resonance is correct.

It is now SPR calcs length resonance and end plate separation.

The guide wavelengths used are based on the Df equation, which I assume uses the mode Shawyer does his designs with. Would seem the Mode he used and developed his DF around is another unanswered question.

That being said, it implies the resonance calc is as valid as his Df calc.

To be clear Shawyer doesn't give the mode his equations are based on. Must be a bit of IP he doesn't wish to share. Which I respect. Never the less we don't need to know the mode he uses, just the guide wavelength that is produced by his Df equation in that mode. From those numbers, the physical end plate separation can be determined, operating in what ever mode Shawyer developed his Df equation from.

While I agree it would be nice to know the mode his calcs use, it is not required to determine the physical dimensions, which as a replicator, is all I really need.

As your math skills are superior to mine, maybe you can reverse engineer the operational mode from the Df equation and generated values, while I get on with the physical replication.
"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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@TheTraveller: Excuse my obtuseness, but don't you have the design freedom to arrange for Df to be as close to unity as you like? If there's one thing that Shawyer's work teaches, it's that maximising Df maximises thrust - therefore this seems to be worthwhile.

So what constraints forbid you designing for near-unity Df?

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