Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1802315 times)

Offline aero

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I have uploaded anther try at generating a TE mode in Shell's frustum model.
https://drive.google.com/folderview?id=0B1XizxEfB23tflFzUEREeWtJMVZucl9nOWtGaGUtUzlkdnczSkthYVVNVDU4UGNMZ29iRm8&usp=sharing

I uploaded a "standard" data set including all .png view files and all csv files including big and small end cuts and y and z cuts. If this data set doesn't show a TE resonant mode, then the problem is likely in my choice of coordinate systems being different than standard conventions. I am assuming of course that meep uses standard conventions internally - seems a safe assumption.

aero
Retired, working interesting problems

Offline rfmwguy

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Looks about right to me. Acceleration stops when the power is turned off, the velocity "slowly" decreases from there due to friction. Since there is very little friction, it keeps moving at nearly the same speed for quite a while but the acceleration stops when it's supposed to.
Todd
You don't see the velocity continuing to increase after power is turned off?
Perhaps a fan kicked on in one of those pieces of equipment on the table...but not that any of that is published.
Here's Shawyer's own data from the 2008 paper when the turntable was demonstrated seven years ago!!. My crude version below. Both show velocity increasing after power is removed. Thermal? Fans? Floobie Dust?
If the vertical axis is position, and the horizontal is time, then this looks like a fairly "constant" velocity slope to me, from nearly the moment that the power is turned off. I'm not analyzing your spreadsheet, just the slope on the graph provided.
Todd
Thanks, and a good fit. But it's not the full story. I'm a bit slow today (probably last night's beer with the boys) but finally got it. Will publish as soon as I have the data tidied up.
Have to admit DM, am impressed with your willingness to help...lots of skeptics just throw stones, you seem to have broken the mold...well done...cheers  8)

Offline deltaMass

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Looks about right to me. Acceleration stops when the power is turned off, the velocity "slowly" decreases from there due to friction. Since there is very little friction, it keeps moving at nearly the same speed for quite a while but the acceleration stops when it's supposed to.
Todd
You don't see the velocity continuing to increase after power is turned off?
Perhaps a fan kicked on in one of those pieces of equipment on the table...but not that any of that is published.
Here's Shawyer's own data from the 2008 paper when the turntable was demonstrated seven years ago!!. My crude version below. Both show velocity increasing after power is removed. Thermal? Fans? Floobie Dust?
If the vertical axis is position, and the horizontal is time, then this looks like a fairly "constant" velocity slope to me, from nearly the moment that the power is turned off. I'm not analyzing your spreadsheet, just the slope on the graph provided.
Todd
Thanks, and a good fit. But it's not the full story. I'm a bit slow today (probably last night's beer with the boys) but finally got it. Will publish as soon as I have the data tidied up.
Have to admit DM, am impressed with your willingness to help...lots of skeptics just throw stones, you seem to have broken the mold...well done...cheers  8)
You haven't seen me eat the crow yet.  Last night's beer has not been kind. But the data will be interesting nonetheless - stay tuned. I need one order better fitting polynomial, and it means a complete redo...

Offline Silversheep2011

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So while the experimenters are all making their first models.
What comes next?
Maybe get on with some EmDrive debugging and tunning?
I spent the last two days [As have been home with flu from work]
  And clean up a 2014 Paper by Yang from this is from a Public Domain sourced document.
Found here.
http://wulixb.iphy.ac.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=60316
This is different from 2010 and 2012 papers.
And have attempted to convert it from Chinese to English via the goggle translator  and the occasion bit of writer’s licence.
Please note: I’m not a translator, so please no slagging off about grammer being wrong or alike. And in fact encourage anyone the thread who is a proper translator with a proper qualification in translating ‘Chinese to English’ to give it a go!
I have tidied it up with the goal to make it somewhat more readable.  Changes you see marked in ‘Red’, Seems to help make it readable.
Warning: You still may need to read some sentences twice to get the full meaning. as I didn’t wish to make too much in the way of changes to original document and miss the meanings
At this stage it’s more of a ‘hey… look this is what in here!”     
And sorry-- no dimensions,
I think it carries several deep insights that could be helpful

 For example:
- What that rectangular waveguide window does [now I know].
-Importance of really ‘narrow band’ tunning.
- Why an EC solid-state feedback loop is important.
-Weird Feedback loop issues.
- Heating effects and monitoring suggestions that in turn related to volume convex distortions at the frustum


 
 

Offline TheTraveller

That is a false conclusion. There are strong forces exerted at 90 deg to the side walls. As the wave fronts expand, they push back on the walls.
Todd

Would seem the peer reviews have accepted there are no side wall Forces in this cavity design.

I think this mistake comes from assuming a "ray vector" approach, which is commonly used in waveguide physics. If you assume the ray vector emits from the apex and reflects off the spherical surface, the vector is always parallel to the walls. Then you would conclude that the wave does not touch the side walls, and you would be wrong.

When the E field makes a 90 deg angle to the cone wall, it is exerting "Maximum" force, not zero. The component of E that is parallel to the wall is zero, due to the boundary conditions. So the entire assumption of a ray vector falls apart when you analyze the fields and the boundary conditions. The ray is parallel to the wall, which means the fields E and H are perpendicular to the wall. As the wave expands, it exerts a strong Lorentz force on the walls when the wavelength is close to the lateral cut-off diameter.

Sorry TT, I have seen worse errors published in peer reviewed journals. Peer review does not guarantee it is correct and in this case, I can assure you with 100% confidence, that it is not.
Todd

When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure
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Offline TheTraveller

... SPR in-house software and produced the Df and resonant frequency at TE013 being:

Frustum big diameter   m: 0.2314m (my data)
Frustum small diameter: 0.1257m (my data)
Frustum centre length: 0.1386m (my data)
Mode: TE013 (my data)

Resonance: 3.9003 GHz (SPR data based on the above)
Df: 0.634 (SPR data based on the above)...
...BTW what resonance and Q do you get for my Flight Thruster estimated dimensions?...

Frustum big diameter   : 0.2314 m
Frustum small diameter: 0.1257 m
Frustum length: 0.1386 m

Mode Shape; TE013

air index of refraction at STP  = 1.000277
cVacuum = 299792458 (*meter/s*)
epsilon0 = 8.854187817*10^(-12)
mu0 = 0.999991(*copper*)*4*Pi*10^(-7)
resistivity =  1.678*10^(-8)(*copper*);

                                Frequency (GHz)     Q     
Flat Ends                   3.812                    less than 72,800    (flat ends approximated by equivalent spherical sections)
Spherical Ends           3.687                    74,052                      (exact solution)

Q's are for a perfect geometry and based on pure copper resistivity =  1.678*10^(-8)
for other purities of copper or other materials, scale the Q by the square root of the inverse resistivity ratio

Q's for flat ends should be lower than 72,800 because of degradation losses of spherical waves on flat ends is not exactly modeled.

Thanks for doing that. Most appreciated.

Both the SPR and my spreadsheet, assuming spherical end, predicts 3.9003GHz as the TE103 resonance for those estimated Flight Thruster internal dimensions. Roger did not disclose the Q and my spreadsheet is not yet doing Q so there I have nothing to compare.

You may wish to model my build dimensions as here I was told the Q was 88k and resonance was 2.4505GHz, which agrees with my models resonance calc.
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Offline SeeShells

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That is a false conclusion. There are strong forces exerted at 90 deg to the side walls. As the wave fronts expand, they push back on the walls.
Todd

Would seem the peer reviews have accepted there are no side wall Forces in this cavity design.

I think this mistake comes from assuming a "ray vector" approach, which is commonly used in waveguide physics. If you assume the ray vector emits from the apex and reflects off the spherical surface, the vector is always parallel to the walls. Then you would conclude that the wave does not touch the side walls, and you would be wrong.

When the E field makes a 90 deg angle to the cone wall, it is exerting "Maximum" force, not zero. The component of E that is parallel to the wall is zero, due to the boundary conditions. So the entire assumption of a ray vector falls apart when you analyze the fields and the boundary conditions. The ray is parallel to the wall, which means the fields E and H are perpendicular to the wall. As the wave expands, it exerts a strong Lorentz force on the walls when the wavelength is close to the lateral cut-off diameter.

Sorry TT, I have seen worse errors published in peer reviewed journals. Peer review does not guarantee it is correct and in this case, I can assure you with 100% confidence, that it is not.
Todd

When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure
Tapered cavity of a fiber optic wave.

Offline TheTraveller

That is a false conclusion. There are strong forces exerted at 90 deg to the side walls. As the wave fronts expand, they push back on the walls.
Todd

Would seem the peer reviews have accepted there are no side wall Forces in this cavity design.

I think this mistake comes from assuming a "ray vector" approach, which is commonly used in waveguide physics. If you assume the ray vector emits from the apex and reflects off the spherical surface, the vector is always parallel to the walls. Then you would conclude that the wave does not touch the side walls, and you would be wrong.

When the E field makes a 90 deg angle to the cone wall, it is exerting "Maximum" force, not zero. The component of E that is parallel to the wall is zero, due to the boundary conditions. So the entire assumption of a ray vector falls apart when you analyze the fields and the boundary conditions. The ray is parallel to the wall, which means the fields E and H are perpendicular to the wall. As the wave expands, it exerts a strong Lorentz force on the walls when the wavelength is close to the lateral cut-off diameter.

Sorry TT, I have seen worse errors published in peer reviewed journals. Peer review does not guarantee it is correct and in this case, I can assure you with 100% confidence, that it is not.
Todd

When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure
Tapered cavity of a fiber optic wave.


An interesting effect for sure.

My point was what Todd was claiming files in the face of how radiation pressure works, which is there will be no radiation pressure on a surface, from a EM wave, that is orthogonal to a reflecting surface, which is what Shawyer claims and was backed up by the peer reviewers.
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Offline flux_capacitor

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You may wish to model my build dimensions as here I was told the Q was 88k and resonance was 2.4505GHz, which agrees with my models resonance calc.

(clic on the link above to see the picture)

TT, is there a reason your cut-off diameter is 148.7 mm instead of the established value of 149.2 mm at 2.45 GHz? Speed of light in air instead of vacuum?

Rodal claims there is no sharp cut-off below the cut-off diameter in a truncated cone cavity, that modes continue, in some degraded way. But if we build a frustum with a small end just below cut-off, how will this affect the Q-factor? Does it degrades too?

What is Warptech advice about the best setting for the small end: just below, just exactly or just above the cylindrical-equivalent cut-off diameter?

If I recalled correctly, at some point you wanted to give more room to your small end, increasing it to 150 mm. What's your decision?

About the difference of c in vacuum and in air, and the gas you will use: somemone on Reddit was concerned about using nitrogen in your cavity, because N2 could maybe "oxidize" the copper forming copper nitride (Cu3N). So you would be more secure filling your sealed frustum with a noble gas such as argon. But what is the speed of light in Ar at 0.5 atm ?
« Last Edit: 08/04/2015 09:03 AM by flux_capacitor »

Offline Flyby

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When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure

The question is whether the (presumed) force in an EMdrive originates from radiation pressure, or whether there is another effect into play.

I do not think you can explain the EMdrive with radiation pressure. Several knowledgeable people inhere already demonstrated that the forces exceed the normal photonic force expectations.
Something else is at play here...

Consequently, i don't think it is fitting to argue about radiation pressure...

I sooo wish that somebody could actually confirm that an EMdrive produces a force, so i can drop the "supposedly" or "assumed" in front of the word "force"...




« Last Edit: 08/04/2015 09:21 AM by Flyby »

Offline TheTraveller

You may wish to model my build dimensions as here I was told the Q was 88k and resonance was 2.4505GHz, which agrees with my models resonance calc.

(clic on the link above to see the picture)

TT, is there a reason your cut-off diameter is 148.7 mm instead of the established value of 149.2 mm at 2.45 GHz? Speed of light in air instead of vacuum?

Rodal claims there is no sharp cut-off below the cut-off diameter in a truncated cone cavity, that modes continue, in some degraded way. But if we build a frustum with a small end just below cut-off, how will this affect the Q-factor? Does it degrades too?

What is Warptech advice about the best setting for the small end: just below, just exactly or just above the cylindrical-equivalent cut-off diameter?

If I recalled correctly, at some point you wanted to give more room to your small end, increasing it to 150 mm. What's your decision?

About the difference of c in vacuum and in air, and the gas you will use: somemone on Reddit was concerned about using nitrogen in your cavity, because N2 could maybe "oxidize" the copper forming copper nitride (Cu3N). So you would be more secure filling your sealed frustum with a noble gas such as argon. But what is the speed of light in Ar at 0.5 atm ?

My error.

There is a slight difference between my model and that of SPR, being 0.37% in length resonance. Df is spot on to 5 decimal places. When I cross check data I get from them I apply a compensation factor. Forgot to back it out when doing the frustum design. 149.2 is the correct cutoff dia at TE01 and 2.45GHz.

Working on a modified design that will allow a 2.3GHz bottom end, so to allow for manufacturing tolerances exceeding 0.05mm.

Dimensions are:
Frustum big diameter   : 400.0mm
Frustum small diameter: 159.0mm
Frustum centre length: 240.7mm

Using the above dimensions, the 2.45GHz Df drops from 0.925 to 0.857, so a slight drop in Force generation is predicted. At Shawyer's calculated Q of 88k, my 100W of Rf should produce around 50mN (5g) of Force.

As Demonstrator rotary table test produced 1.8g of net Force, driving a 100kg mass, my table should accelerate much quicker as there should be 2.8 times more Force, driving 20% of the mass or about 13.9 times greater acceleration.

Based on Shawyer's advise, there is no usable resonance nor Force generation if the small end is at or below cutoff. So doesn't matter if it drops off sharp or slow, don't go there.
« Last Edit: 08/04/2015 09:36 AM by TheTraveller »
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Offline TheTraveller

Demonstrator EMDrive rotary test acceleration calcs:

Known:

Distance moved: 1.85m
Powered on time: 80 sec
Start velocity: 0.0cm/s
Final powered on velocity: 2cm/s

Acceleration = 0.000289 m/s^2 being distance/(time^2)
Acceleration = 0.000250 m/s^2 being (Vfinal - Vstart)/time

Close enough for me.

From that the expected acceleration for my EMDrive and test rig would be approx
0.00348 m/s^2 or
0.354 milli-g.
« Last Edit: 08/04/2015 10:09 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 TheTraveller

When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure

The question is whether the (presumed) force in an EMdrive originates from radiation pressure, or whether there is another effect into play.

I do not think you can explain the EMdrive with radiation pressure. Several knowledgeable people inhere already demonstrated that the forces exceed the normal photonic force expectations.
Something else is at play here...

Consequently, i don't think it is fitting to argue about radiation pressure...

I sooo wish that somebody could actually confirm that an EMdrive produces a force, so i can drop the "supposedly" or "assumed" in front of the word "force"...

The UK gov, in funding the Demonstrator and rotary test rig, set up an expert panel that confirmed Shawyer (has been stated this happened in the UK Parliament). Links were given in this Forum.

Prof Yang also confirmed Shawyer.

Eagleworks atmo tests confirmed them both.

What more do you want?
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline Rodal

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...Rodal claims there is no sharp cut-off below the cut-off diameter in a truncated cone cavity,
The fact that there is not sharp cut-off for tapered waveguides is not a claim invented by me or something that is going to win me any prices among people in the know, it is something that is already known in the literature for quite some time.  It is as if somebody claims that the Earth is flat, and I say, no the Earth is not flat, and it has been known for quite some time that the Earth is not flat.  Please take a look at the peer-reviewed references I provided as well as the fact that any finite element computer program (ANSYS, COMSOL, etc.) can readily verify the fact that there is no sharp cut-off in a tapered waveguide. 


... that modes continue, in some degraded way. But if we build a frustum with a small end just below cut-off, how will this affect the Q-factor? Does it degrades too? ...

If you build a frustum with the small end below cut-off (it doesn't need to be "just below cut-off" as the modes persist way beyond it) it can resonate in a number of modes, for example it can resonate in a mode with higher p (where p is the longitudinal quantum mode number). 


The answer to this question:

QUESTION: if we build a frustum with a small end below cut-off and we excite it at the somewhat lower frequency at which the mode shape that would have been cut-off in a perfect cylindrical waveguide still resonates in the frustum how will this affect the Q-factor? Does the Q degrade? ...

is:

ANSWER: yes, of course that the Q will degrade in that case.  As I have shown, in such a frustum the region near the small base would be empty of standing waves, and instead contain evanescent waves hence that portion of the volume is wasted for Q resonance purposes.  As Q is the ratio of the volumetric to the surface integral of the square of the magnetic field, it follows that any such wasted volume devoid of standing waves results in a lower Q.

But again, if you build such a frustum, it is most likely to resonate at a higher p mode which will fill the entire frustum with standing waves -and hence have higher Q-, so the excitation of the mode shape discussed above cannot be taken for granted: it has to be excited at the correct frequency.
« Last Edit: 08/04/2015 12:00 PM by Rodal »

Offline rfmwguy

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When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure

The question is whether the (presumed) force in an EMdrive originates from radiation pressure, or whether there is another effect into play.

I do not think you can explain the EMdrive with radiation pressure. Several knowledgeable people inhere already demonstrated that the forces exceed the normal photonic force expectations.
Something else is at play here...

Consequently, i don't think it is fitting to argue about radiation pressure...

I sooo wish that somebody could actually confirm that an EMdrive produces a force, so i can drop the "supposedly" or "assumed" in front of the word "force"...
Here's where my theory is headed, slowly I might add...fluid dynamics - translation to particle dynamics needed:

Suppose we model a fluid vortex with photonic energy. IOW, imagine the frustum is spinning photons creating a centralized low pressure core of TM. COE/COM would require this to be filled from somewhere.

So I envision the engine, not as a thruster but a "puller" to use plain english.

In fluid dynamics particle speed and energy peak as u move down the vortex, or frustum. Since photons have little "fluid" resistance, speed is unlimited...except for C...where strange things happen...theoretical increase in mass....question is from where?

Mass inflow to the vortex should come from the small end because that's the way it works in nature...I know, I lived in tornado alley most my life. Some energy is lost in heat along the frustum.

So I went even further out on a limb, plain english and before I started translating fluid dynamics to particle dynamic for a vortex. Weird, huh?

If anyone wants to follow me down the rabbit hole with this strange conjecture, I welcome any help I can get as I'm still in my test mode :)

Offline Flyby

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The UK gov, in funding the Demonstrator and rotary test rig, set up an expert panel that confirmed Shawyer (has been stated this happened in the UK Parliament). Links were given in this Forum.

Prof Yang also confirmed Shawyer.

Eagleworks atmo tests confirmed them both.

What more do you want?

hmmm... the same thing that about 90% of the people on this forum want: a clear and unchallenged force signal, that is not hidden in a lot of measurement noise and that can be checked and verified by others.

I do agree with you that Shawyer's tests look convincing, but it is still too much based upon perception...

In our legal system there is a nice description that perfectly characterizes the current situation on the EMdrive :
There is a difference between "an indication of evidence" and "pure evidence".

As i see it, we're currently still in the "indication of evidence" phase....
We need irrefutable proof it is working. Period.
Several more testers need to produce identical/similar or better results like Shawyer's experiment.
Claims on paper have little meaning if they cant be matched with real world experiments (like you're doing).

It is not that I do not want to believe it works, but "believing" is not really a scientific attitude, is it?

Offline Flyby

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If anyone wants to follow me down the rabbit hole with this strange conjecture, I welcome any help I can get as I'm still in my test mode :)

I do like to follow your line of thought , as i got some of my own weird ideas also... ;)
My problem is that I do not have the proper training in this type speculations as my science background is seriously lacking there, compared to some people here who made a professional career out of it...
The last thing I want to venture into is pseudo science, so I usually refrain from going public with silly ideas... 8)

ah...It is a consequence of a decision i made 30 years ago, where I had to choose between nuclear engineer or architect as path in life. I choose the last option, but my interest in nuclear astrophysics never really left me. I can not keep up with high level discussions and the needed level of math they require, but I do keep trying to understand and follow what's being said.
No regrets doh... just a curiosity what life would have been if i had taken a different path...

« Last Edit: 08/04/2015 12:44 PM by Flyby »

Offline Slyver

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Quote
The UK gov, in funding the Demonstrator and rotary test rig, set up an expert panel that confirmed Shawyer (has been stated this happened in the UK Parliament). Links were given in this Forum.

Prof Yang also confirmed Shawyer.

Eagleworks atmo tests confirmed them both.

What more do you want?

I want a hermetically sealed, EM shielded, thermally preloaded box, with a self containted EMdrive/RF source/power supply inside it, on a rotating arm whose bearing stiction has been tested and proven to be several orders of magnitude below any observed effect.  I want there to be an angular acceleration of the system, which slows to a constant velocity exactly as expected by air resistance.

I then want the entire device (box, arm, drive, and air internal to the box) to be put in a reasonable vacuum and there to be no meaningful difference (at least agreement in the order of magnitude) between measurements taken in either environment.

(We don't know that air (internal, external (or both)) does not play a meaningful (not artifactual) part of the system (for whatever of the myriad reasons it might), and there are measurements that suggest the possibility that it does. This should be tested.)

Finally, I want to be able to find no flaws in the experimental setup within the order of magnitude of the measured forces; something I can not say about ANY experiment done so far. I also want every person who looks at it (with a reasonably open mind) to be just as comfortable with the results as myself.
« Last Edit: 08/04/2015 01:27 PM by Slyver »

Offline Rodal

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... SPR in-house software and produced the Df and resonant frequency at TE013 being:

Frustum big diameter   m: 0.2314m (my data)
Frustum small diameter: 0.1257m (my data)
Frustum centre length: 0.1386m (my data)
Mode: TE013 (my data)

Resonance: 3.9003 GHz (SPR data based on the above)
Df: 0.634 (SPR data based on the above)...
...BTW what resonance and Q do you get for my Flight Thruster estimated dimensions?...

Frustum big diameter   : 0.2314 m
Frustum small diameter: 0.1257 m
Frustum length: 0.1386 m

Mode Shape; TE013

air index of refraction at STP  = 1.000277
cVacuum = 299792458 (*meter/s*)
epsilon0 = 8.854187817*10^(-12)
mu0 = 0.999991(*copper*)*4*Pi*10^(-7)
resistivity =  1.678*10^(-8)(*copper*);

                                Frequency (GHz)     Q     
Flat Ends                   3.812                    less than 72,800    (flat ends approximated by equivalent spherical sections)
Spherical Ends           3.687                    74,052                      (exact solution)

Q's are for a perfect geometry and based on pure copper resistivity =  1.678*10^(-8)
for other purities of copper or other materials, scale the Q by the square root of the inverse resistivity ratio

Q's for flat ends should be lower than 72,800 because of degradation losses of spherical waves on flat ends is not exactly modeled.

Thanks for doing that. Most appreciated.

Both the SPR and my spreadsheet, assuming spherical end, predicts 3.9003GHz as the TE103 resonance for those estimated Flight Thruster internal dimensions. Roger did not disclose the Q and my spreadsheet is not yet doing Q so there I have nothing to compare.

You may wish to model my build dimensions as here I was told the Q was 88k and resonance was 2.4505GHz, which agrees with my models resonance calc.
I just saw your drawing.



Your definition of truncated cone length is different than mine.

We have been comparing apples to oranges.

I have been defining the length as the distance measured perpendicular between the plane surfaces defined by the diameters. (That is a consistent mathematical definition with the use of diameters).

You in turn have a drawing where you define the length as the difference between the spherical radii: your "length" is the length between the spherical surfaces, not between the plane surfaces of the diameters).
Your "length" is the lateral length of the spherical truncated cone: the difference between the spherical radii r2 -    r1

That is a different definition of length !  They are not the same.  Actually the difference makes a difference in frequencies of the order we are discussing.

That's comparing apples and oranges.

We are calculating frequencies based on different geometrical dimensions.

The natural frequency comparison for the spherical end case is moot, as it is predicated on different dimensions !

If I calculate the natural frequency based on your definition of length, I will get a higher natural frequency closer to 3.9 GHz
« Last Edit: 08/04/2015 01:25 PM by Rodal »

Offline SeeShells

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That is a false conclusion. There are strong forces exerted at 90 deg to the side walls. As the wave fronts expand, they push back on the walls.
Todd

Would seem the peer reviews have accepted there are no side wall Forces in this cavity design.

I think this mistake comes from assuming a "ray vector" approach, which is commonly used in waveguide physics. If you assume the ray vector emits from the apex and reflects off the spherical surface, the vector is always parallel to the walls. Then you would conclude that the wave does not touch the side walls, and you would be wrong.

When the E field makes a 90 deg angle to the cone wall, it is exerting "Maximum" force, not zero. The component of E that is parallel to the wall is zero, due to the boundary conditions. So the entire assumption of a ray vector falls apart when you analyze the fields and the boundary conditions. The ray is parallel to the wall, which means the fields E and H are perpendicular to the wall. As the wave expands, it exerts a strong Lorentz force on the walls when the wavelength is close to the lateral cut-off diameter.

Sorry TT, I have seen worse errors published in peer reviewed journals. Peer review does not guarantee it is correct and in this case, I can assure you with 100% confidence, that it is not.
Todd

When an EM wave is traveling orthogonal to a surface, the cosine loss of the radiation pressure equation is maxed and there is no radiation pressure produced on the surface by the passing EM wave. Don't believe it? Try to get thrust from a solar sail oriented so the surface is orthogonal to the sun's EM waves.

https://en.wikipedia.org/wiki/Radiation_pressure
Tapered cavity of a fiber optic wave.


An interesting effect for sure.

My point was what Todd was claiming files in the face of how radiation pressure works, which is there will be no radiation pressure on a surface, from a EM wave, that is orthogonal to a reflecting surface, which is what Shawyer claims and was backed up by the peer reviewers.

It's not in any uncertain terms just an interesting effect TT or a sideshow parlor trick.

Here we see in a tapered waveguide of fiber optic the light traveling down the optic fiber. The waves decaying into the side walls making evanescent waves imparting their spin and momentum through the walls moving large cells. This is an order above the simple pressures that light induces on a light sail. I could not shine a bright light on a cell and move it like this.

In this video a Evanescent wave is created traveling along the sidewalls of the fiber optic, created from the angle of incident reflection and the decay because it is a tapered fiber.  Maxwell's equations don't account for this effect. It requires quantum tunneling and the Schrödinger wave-function representing particle motion normal to the boundary. 

What I find very interesting is microwaves reflecting from the sidewalls of the frustum are also creating and transferring within the frustum walls this extraordinary spin and momentum from the decaying wave functions that's not covered by Maxwell's theorems.

For you to say there aren't any forces within the sidewalls from the microwaves is incorrect.

 REF and Quote... https://en.wikipedia.org/wiki/Evanescent_wave

Shell
« Last Edit: 08/04/2015 01:20 PM by SeeShells »

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