Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1796178 times)

Offline kml

Using the following dimensions:

Length:   138.6mm
Small diameter:   125.7mm
Big diameter:   231.4mm

and using the speed of light in air:

cAir = 299705000 (meter/s)

My exact solution gives:

Mode:   TE013
Frequency:   3.94571 GHz

Mode:   TE012
Frequency:   3.10927 GHz

Mode:   TE011
Frequency:   2.37833 GHz

So the question is: why are you going to excite this with TE013 at 3.95GHz, when you could be exiting it a 2.38 GHz (a frequency much closer to the usual magnetron frequency) in mode TE011 which should give you a greater amplitude (*) ?

Does your spreadsheet predict that you are going to get a higher thrust force with TE013 than with TE011 ?

Both modes TE011 and TE013 have identical electromagnetic field variation in the circular cross-section, the only difference is that TE013 has a higher frequency variation in the longitudinal direction.


(*) 1) Amplitude of mode shapes decreases with frequency, in general, for all kinds of vibrations and 2) Look at Notsosureofit's thrust force formula

Would TE011 actually work? 2.37GHz is below the TE01 cutoff frequency of 2.9GHz for a cylindrical waveguide of the small end dimension (125mm).     
« Last Edit: 05/28/2015 07:11 PM by kml »

Offline SeeShells

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Hot Tub Time, brain is fried! No, it's not a Time Machine Hot Tub as some have suggested. ;)

For the last several weeks I've been working, reading and even watching very good educational youtube videos to catch up because so many things just were not making sense. True, a 40 year old education is a little Model-T as far as current science is concerned and when I started this I assumed most of the foundations that were laid down during school would stand the test of time. Well, I learned some things change and some things never do.

I just read a very good paper and it exemplifies what I've been seeing and why it's a good thing I'm taking the time to re-learn and accept some "new" knowledge. Not as easy when I was much younger but,  I've learned a few things since then.

Build a EM Thruster? You betcha. Be safe? ? No question. Know how and why it works? Yep! That's the key. I've never built anything in my life without knowing the how and whys, it's the way I am.

Thanks for all the wonderful minds here, I'm learning so much and hopefully I can return the favor.

Oh, here is the link to this paper that has put many things into perspective for me and I think it's a good read.
Shell
http://arxiv.org/pdf/gr-qc/0205066.pdf

Offline WarpTech

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I'm just gonna leave this here...

"Macroscopic and Direct Light Propulsion of Bulk Graphene Material"
http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf


Quote
The force generated from such a process/mechanism is much
larger than the force generated directly from the conventional light pressure, which is
much smaller than the force required to propel the samples.

Quote
The mechanism behind this novel phenomenon is believed to be an
efficient light-induced ejected electron emission process, following an Auger-like path
due to both the unique band structure of graphene and its macroscopic morphology of
this unique material.

This article is showing that for certain types of materials, light can impart more force to the material, than it would if it were simply used to as a photon rocket to push the same material. The difference is the Auger Effect, where the incoming light causes a population inversion in the material, that then causes electrons to be ejected from the material, greatly increasing the force by many orders of magnitude. Perhaps a similar effect can be obtained asymmetrically in a cavity?

Thank you for posting it!

Todd

Offline aero

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Quote
The only advantage I see with TE013 is that it has the Poynting vector concentrated at the small end, and a local high amplitude at the small end.

Speaking of the Poynting vector, some number of pages back, you (Dr. Rodal) calculated that it has a zero average over a full wavelength in the cavity. Is that a full wavelength of the drive frequency, or a full wavelength of the stress tensor?

The reason I ask is because when using a mode TX m,n,p, if p is odd then the cavity doesn't have a full wavelength of the drive frequency.
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Offline Mulletron

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...Would TE011 actually work? 2.37GHz is below the TE01 cutoff frequency of 2.9GHz for a cylindrical waveguide of the small end (125cm).   
TE011 is actually not cut-off according to the exact solution with spherical ends for those dimensions listed above (125.7mm).   It looks good and strong, very clear signal in the exact solution.

It would have higher attenuation at the small end, which according to Todd's theory -which has my seal of approval  :) - is a plus.

I suppose that those that think that attenuation is bad may opt against, but it would be nice to test.

The only advantage I see with TE013 is that it has the Poynting vector concentrated at the small end, and a local high amplitude at the small end.

Hey Todd (WarpTech), we need to get your theory written up and in the Wiki http://emdrive.echothis.com/Theory
Challenge your preconceptions, or they will challenge you. - Velik

Offline Flyby

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Ayeye skipper.....Raises hand for the "Todd Conjecture"...  :P
« Last Edit: 05/28/2015 08:11 PM by Flyby »

Offline rfmwguy

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(...)
Oh, here is the link to this paper that has put many things into perspective for me and I think it's a good read.
Shell
http://arxiv.org/pdf/gr-qc/0205066.pdf
Great article, struggled abit, but demonstrates the uncertainties between classic and "modern" physics. The CoE/CoM handwavers must sense something is afoot. Pretty sure the resonance/shape frustum cavity is partlally responsible for the apparent "effect" and cranking more power may increase it; but it may reach a point of diminishing returns or thermal/practical limits due to materials knowledge or science. The dielectric material has been of special interest (obsession)  ;) to me. Can the "effect" be amplified exponentially, not by an increase in power, but by materials in the small end of the cavity. Guess I'm a fan of lower power experimentation with dielectric material as the only variable from test to test. Might have to break out my soldering iron after all... ;D

Offline SeeShells

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(...)
Oh, here is the link to this paper that has put many things into perspective for me and I think it's a good read.
Shell
http://arxiv.org/pdf/gr-qc/0205066.pdf
Great article, struggled abit, but demonstrates the uncertainties between classic and "modern" physics. The CoE/CoM handwavers must sense something is afoot. Pretty sure the resonance/shape frustum cavity is partlally responsible for the apparent "effect" and cranking more power may increase it; but it may reach a point of diminishing returns or thermal/practical limits due to materials knowledge or science. The dielectric material has been of special interest (obsession)  ;) to me. Can the "effect" be amplified exponentially, not by an increase in power, but by materials in the small end of the cavity. Guess I'm a fan of lower power experimentation with dielectric material as the only variable from test to test. Might have to break out my soldering iron after all... ;D
I know, so many want high power and to push it, but you know sometimes you can't hear the band if you bang the drums to hard?
I'll tell you this, I also see the "effect" under an influence with another material in the small end, just too many things that are clicking right about it. 

Offline rfmwguy

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Oh, here is the link to this paper that has put many things into perspective for me and I think it's a good read.
Shell
http://arxiv.org/pdf/gr-qc/0205066.pdf
Great article, struggled abit, but demonstrates the uncertainties between classic and "modern" physics. The CoE/CoM handwavers must sense something is afoot. Pretty sure the resonance/shape frustum cavity is partlally responsible for the apparent "effect" and cranking more power may increase it; but it may reach a point of diminishing returns or thermal/practical limits due to materials knowledge or science. The dielectric material has been of special interest (obsession)  ;) to me. Can the "effect" be amplified exponentially, not by an increase in power, but by materials in the small end of the cavity. Guess I'm a fan of lower power experimentation with dielectric material as the only variable from test to test. Might have to break out my soldering iron after all... ;D
I know, so many want high power and to push it, but you know sometimes you can't hear the band if you bang the drums to hard?
I'll tell you this, I also see the "effect" under an influence with another material in the small end, just too many things that are clicking right about it.

Yes, Shell, I'd start with cavity optimization, then dielectric, then power. Dielectric variables can be "tuned" as shown in Shawyer's model and Iulian is replicating. These threads seem to be focused on cavity discussions/optimization which is needed, but phase 2 could be dielectrics...guess i'm jumping ahead too soon  8)

Offline tchernik

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Oh, here is the link to this paper that has put many things into perspective for me and I think it's a good read.
Shell
http://arxiv.org/pdf/gr-qc/0205066.pdf
Great article, struggled abit, but demonstrates the uncertainties between classic and "modern" physics. The CoE/CoM handwavers must sense something is afoot. Pretty sure the resonance/shape frustum cavity is partlally responsible for the apparent "effect" and cranking more power may increase it; but it may reach a point of diminishing returns or thermal/practical limits due to materials knowledge or science. The dielectric material has been of special interest (obsession)  ;) to me. Can the "effect" be amplified exponentially, not by an increase in power, but by materials in the small end of the cavity. Guess I'm a fan of lower power experimentation with dielectric material as the only variable from test to test. Might have to break out my soldering iron after all... ;D
I know, so many want high power and to push it, but you know sometimes you can't hear the band if you bang the drums to hard?
I'll tell you this, I also see the "effect" under an influence with another material in the small end, just too many things that are clicking right about it.

Yes, Shell, I'd start with cavity optimization, then dielectric, then power. Dielectric variables can be "tuned" as shown in Shawyer's model and Iulian is replicating. These threads seem to be focused on cavity discussions/optimization which is needed, but phase 2 could be dielectrics...guess i'm jumping ahead too soon  8)

Personally, I'm also intrigued and wondering if the presence of gas molecules in the cavity has any impact on the thrust.

It seems it does, as per NASA Eagleworks' results, but they tested a vented cavity in air and in vacuum, not with a sealed vacuum inside the cavity working with air outside, or with sealed gas in the cavit with vacuum outside.  It rests to be seen in a sealed cavity filled with air molecules or other gas still keeps the same thrust when working in a vacuum.

Offline SeeShells

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Oh, here is the link to this paper that has put many things into perspective for me and I think it's a good read.
Shell
http://arxiv.org/pdf/gr-qc/0205066.pdf
Yes, Shell, I'd start with cavity optimization, then dielectric, then power. Dielectric variables can be "tuned" as shown in Shawyer's model and Iulian is replicating. These threads seem to be focused on cavity discussions/optimization which is needed, but phase 2 could be dielectrics...guess i'm jumping ahead too soon  8)
No you're right, you never design the cart before you get the horse. In the design you need to make room for a baseline design and that includes variable input frequencies, multiple injection points, phase shifting, a cavity that's tunable, easy disassembly and assembly, different materials and test equipment and the list goes on and on.  I've had engineers working for me that wanted to build a running Cadillac when all we needed was a wheel to get rolling and we could add another one if needed. ;)

Offline rthrfrd

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Sorry if this has been suggested already:

I would love to see a rig with all required ancillaries mounted on a rotating shaft or turntable, a rigid arm extending perpendicular to the axis of rotation, with the drive attached to the end of the arm. Accelerate the entire apparatus to a set speed and measure its rate of deceleration. The advantages for me would be:

 - Prevents any movement in the ancillaries from affecting the measurement.
 - Allows larger ancillaries (more power).
 - Control test and active test both have the apparatus in motion (no stiction).
 - Measures the cumulative effect of the device instead of just its peak - may be easier for those with less precise tools.
 - No physical connection required between sensors and apparatus.
 - No changes required to test in either direction.

Then again, perhaps such a setup isn't yet feasible with the forces involved.

Offline Space Ghost 1962

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I'm just gonna leave this here...

"Macroscopic and Direct Light Propulsion of Bulk Graphene Material"
http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf


Quote
The force generated from such a process/mechanism is much
larger than the force generated directly from the conventional light pressure, which is
much smaller than the force required to propel the samples.

Quote
The mechanism behind this novel phenomenon is believed to be an
efficient light-induced ejected electron emission process, following an Auger-like path
due to both the unique band structure of graphene and its macroscopic morphology of
this unique material.

This article is showing that for certain types of materials, light can impart more force to the material, than it would if it were simply used to as a photon rocket to push the same material. The difference is the Auger Effect, where the incoming light causes a population inversion in the material, that then causes electrons to be ejected from the material, greatly increasing the force by many orders of magnitude. Perhaps a similar effect can be obtained asymmetrically in a cavity?

Thank you for posting it!

Todd
Indeed. Have been reading the threads and following the readings/theories.

Asymmetrical/antisymmetrical reflection/refraction (also anisotropic materials) have been occasionally been investigated. These often break down quickly, as they are a form of "frozen enthalpy/entropy" that get disordered/ordered. Sometimes found in semiconductors and exotic coatings. These tend to "wear out".

I *have wondered* if the decay of "thrust" might be explained by an Auger-like phenomena with such a substance that "self exhaust" over a time interval, then after a interval "reorganize" and can be "discharged again". And ... erode?

Can anyone help me to "falsify" this? As well as other "hidden propellent" mechanisms ... I wonder if coatings, "air", or dielectrics ... might be breaking down as "erosion"? Would not take much under highly accelerated group velocities to amplify thrust ...

Thank you for an enjoyable thread.

Offline aero

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EDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2  the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.
So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles?

Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity?

Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?
Retired, working interesting problems

Offline TheTraveller

Quote
EDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2  the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.
So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles?

Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity?

Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?

Only the Experimental EM Drive used an internal small end dielectric. As a result, it had low Q and low thrust.

The Demonstrator and Flight Thruster EM Drives are high Q and high thrust devices which did not use a dielectric.

Shawyer says using a dielecrtic:

1) increases loss,

2) reduces Q,

3) reduces thrust.

His reported results back up that claim

So why the interest in dielectrics?
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline aero

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Quote
EDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2  the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.
So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles?

Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity?

Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?

Only the Experimental EM Drive used an internal small end dielectric. As a result, it had low Q and low thrust.

The Demonstrator and Flight Thruster EM Drives are high Q and high thrust devices which did not use a dielectric.

Shawyer says using a dielecrtic:

1) increases loss,

2) reduces Q,

3) reduces thrust.

His reported results back up that claim

So why the interest in dielectrics?

Why not? Would you be satisfies if I wrote, "and the existance or not of the dielectric"?
Retired, working interesting problems

Offline Rodal

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EDIT: Oh, by the way, the Poynting vector frequency is always twice the frequency of the electromagnetic field, its period is 1/2  the period of the electromagnetic field. It reverses direction twice as often as the electromagnetic fields.
So the Poynting vector is an even number of cycles no matter the number of half-cycles of the drive frequency. Well, next we ask, is the drive frequency (period, wavelength) always an interger number of half-cycles?

Seems it must be in order to resonate but the shape of the cavity and the existance of the dielectric makes one wonder, what is the effective drive frequency as far as the Poynting vector is concerned and does it remain always an even number of cycles everywhere within the cavity?

Perhaps a more salient question would be, what is the strength of the Poynting vector force over one-half cycle as that should be the maximum Poynting force attainable, and how does it compare to F = 2PQ/c?

Only the Experimental EM Drive used an internal small end dielectric. As a result, it had low Q and low thrust.

The Demonstrator and Flight Thruster EM Drives are high Q and high thrust devices which did not use a dielectric.

Shawyer says using a dielecrtic:

1) increases loss,

2) reduces Q,

3) reduces thrust.

His reported results back up that claim

So why the interest in dielectrics?

First read this:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1381229#msg1381229 which should answer your question.  Besides that post, there are respectable people in the aerospace community, outside this thread who have the following opinion:

1) NASA's experiments have falsified the results reported by Shawyer and NWPU
2) NASA only measured thrust using a dielectric insert.  No thrust measured without it.

I think that it is important for NASA at some point to conduct further experiments without a dielectric and using a magnetron at higher power as they intended to do, to clarify this situation. I am not convinced about the test without a dielectric because:
a) it was conducted very early in NASA's testing program
b) only a test was performed
c) it involved mode TE012 which, according to Brady's report, was difficult to replicate even with a dielectric, so they had to move on to mode TM212 which was never tested yet without a dielectric.

 It is also important to carry on with the testing program as envisioned by Dr. White, involving replication of the experiments at NASA Glenn.
« Last Edit: 05/28/2015 10:01 PM by Rodal »

Offline deltaMass

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Have asked Roger Shawyer to confirm the quoted Df for the Demonstrator EMDrive is 0.844:

http://emdrive.com/demonstratorengine.html
Can you please ask for him to check his original data documents (rather than his published papers) , and re-calculate the Design Factor based on known geometry, to make sure that there was not an unintended typo somewhere?

From work on my spreadsheet, that can easily adopt to various TMm,n and TEm,n modes, I believe it is possible to get an excitation mode that will deliver a high Df, small end operating just above cutoff (as Shawyer recommends), without using stupid geometry.

Did ask for the excitation mode. If he shares that, will be able to plug it into my spreadsheet and see what it says about small diameter.

The more I work with my spreadsheet, the more I get a good gut feeling about how the 3 dimensions, excitation mode and external Rf frequency interplay with each other to get an optimal mix of all 5 variables for max thrust per applied power.
Have you shared your spreadsheet here? If you do, I can possibly help out with the optimisation

Offline WarpTech

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Flight Thruster build update:

From the best photo of the Flight Thruster I could find and allowing for 2mm thick walls, to add thermal mass and reduce the rate of thermal expansion, the following internal Flight Thruster dimensions were obtained:

Length:   138.6mm
Small diameter:   125.7mm
Big diameter:   231.4mm

Applying those to my spreadsheet generated:

Df:   0.638
Frequency:   3.85GHz
Mode:   TE013

I then asked Roger Shawyer did I get close? His reply:

Df:  0.635
Frequency:   3.9003GHz
Mode:   TE013

I'm VERY happy with that as my Rf gen can easily go to that frequency. Time now to finalise drawings and get some copper sheet laser cut.

Roger also mentioned it is best to give the internal frustum surfaces a nice bright shinny polish. No need for Silver or Gold overcoats.

Will the end-plates be removable in your design? Can you do an experiment, attaching some Ferrite blocks or Metglass to the inside surface of the "big" end?

Offline PaulF

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so, no scat, there i was... I learned you can do stuff that violates the laws of physics so long as you label the process as happening in imaginary time even if it has real physical consequences.

http://phys.org/news/2015-05-physicists-quantum-tunneling-mystery.html

Synopsis: Massive things that quantum tunnel can violate the physical speed limit of light so long as there isn't anybody watching and there cannot be anyone watching because it happens in imaginary time.

I don't know about you; but i kind of had a different idea of what "imaginary" means but evidently imaginary does NOT mean unreal.
To put another spin on this, what intrigued me was their interpretation of gravity. Maybe someone could elaborate if they think they grasp this information, but in my phylisophical head I get the notion that gravity may be another physical dimension coupled to our 4 spacetime dimensions. Or a brane that intersects our 4D spacetime brane (if one wants to relate it to string or brane theory) in a certain way that this could be the mechanism that made the gravitational constant what it is. Or maybe it is parallel to our brane and has a set distance accounting for the grav. constant.

I am not saying gravity is not the effect of mass warping spacetime. Just to be clear.

Or am I thinking way too out there?
« Last Edit: 05/28/2015 10:38 PM by PaulF »

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