Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1805129 times)

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1364
http://www.eagleyard.com/uploads/tx_tdoproductstorage/EYP-TPA-0808-02000-4006-CMT04-0000.pdf

is a nice little asymmetric cavity device just itching to get into space.
But 50 mW in gets you 2 Watts out?
Heh. Forget cavities  8)

"with proper injection from a seed laser"

Offline kdhilliard

  • Full Member
  • *
  • Posts: 171
  • Kirk
  • Tanstaa, FL
  • Liked: 162
  • Likes Given: 523
They have tested it in a vacuum. What will they do next with the EM drive? Will they possibly build a spacecraft with the EM drive to be tested in orbit?

Back in February, Paul March, an engineer at NASA's Eagleworks Lab, reported on their vacuum results -- 50 micro-Newtons forward at 50W, 16 micro-Netwons reverse with a failing RF amp.  These are very small forces, and while they believe that these results are not due to thermal effects (such as imbalance due to thermal expansion), they need to increase the thrust to at least 100 micro-Newtons before trying to replicate the experiment at NASA Glenn Research Center since the lowest force that GRC's thrust stand can measure is about 50 micro-Newtons.  They are also setting up a 1.2kW non-vacuum test from which they hope to have results by July.

Summary: The lab considers the results to be promising, but they are not definitive, and there is a lot more work to do on Earth before testing in orbit.

~Kirk

Online WarpTech

  • Full Member
  • ****
  • Posts: 1229
  • Do it!
  • Vista, CA
  • Liked: 1296
  • Likes Given: 1754
1) Yang has the thrust force (from the EM field) directed towards the Small End. This is completely opposite to Shawyer's unorthodox "thrust force".

I'm starting to wonder if Shawyer doesn't use the term "thrust" as something similar to the "thrust the exhaust gas of a rocket would produce if the cavity was, er, a rocket" (i.e. opposite to the direction of movement), and the term "reaction" as the meaning of "direction of the movement of the cavity" relatively to the "virtual" thrust. I'm not sure, since EmDrive does not expel anything. We don't understand what Shawyer tries to explain with his scheme "thrust vs reaction" (CoM evidently, but it is evident only to him).

Everyone else (Eagleworks, NWPU, Cannae LLC, you, me) uses the word "thrust" as the force in the direction of movement, i.e. small end forward.

So if Shawyer use the word "reaction" instead of our thrust, how could we understand each other? And I insist, I'm not even sure what term he chose for the direction of movement. That's so trivially weird :(

My understanding so far of what he says is this;

First, refers to "thrust" as the EM field moving backwards, and "reaction" as the frustum moving forwards, toward the small end. His idea of thrust is that when the photons are reflected from the small end, the frustum goes forward, the photons go backwards, and momentum is exchanged on the bounce. When they reach the back wall, the effect is the opposite and now "thrust" is forward and "reaction" is backwards, toward the big end. These two reactions do not add to zero. This is why it is not only confusing to read it, but to understand it. Thrust and reaction are both bi-directional, but their sum is not zero.




Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Yang doesn't take the free dynamics bull by the horns.

Also, if she's using heat dissipation as an explanation, how does this system manage  not to be a photon rocket?

(...)
No idea how she can get Force/InputPower thousands of times better than perfect photon rocket.

(...)

Make Q a cyclic, time dependent, PWM duty cycle controlled function, not a constant!

It charges until it has enough thrust to overcome the resistance of the mass, but once it moves, that energy is dissipated. P drops back to Pin and Q has to build up again. I don't see any other way...
Quite frankly, if the thrust measured is to be taken at face value, then it appears to be on order Q*(photon rocket thrust at the same power).  Obviously not sustainable, as you point out. Indeed, to simply be a non-magic photon rocket, the duty cycle has to be 1:1/Q

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
If Yang "nailed it" with "no new physics", which of Noether or Einstein did she decide to trash? Because you have to choose, and either way, it's new physics. To recap: for the free motion:

1. If P = F v, then magically v is known, which implies a preferred rest frame, and Einstein shrieks
2. If P = F = constant, then free energy is available in profusion, and Noether shrieks.

No new physics?

No. 2 is not quite correct since all of the "free energy" schemes have circular terms in the Hamiltonian and only the acceleration to spacial seperation looks that way.  Noether snoozes.
Well, in that case I must ask you to go through my equations and to spot the error.

Offline SeeShells

  • Senior Member
  • *****
  • Posts: 2326
  • Every action there's a reaction we try to grasp.
  • United States
  • Liked: 2956
  • Likes Given: 2590
...Great video.  It touches on so many topics that get discussed here on this forum.

...I thoroughly enjoyed this, Thanks Dr. Rodal!!!
As PhaseShift said it is interesting how this video deals with a number of topics we have been discussing.  For example, the question is asked (by somebody at CERN) to Sundrum as to whether there is a relation of the extra dimension(s) to the Quantum Vacuum virtual particles.  The answer is that this is unknown.  They are using Heisenberg's uncertainty principle as a given.  Sundrum emphasizes the fact that we can borrow much larger amounts of energy than we own (no need of collateral) but that you have to pay it back in an extremely small amount of time.  They are using this ability to borrow larger energy from the QV in their experiments to explore energy being lost in the extra dimension(s). Thus, the issue with Dr. White's proposal is the need to payback, in a very small amount of time, any energy you may borrow (the QV being immutable and non-degradable over longer periods of time).  Essentially, Dr. White's proposal is that one can default on the mortgage  :)
Ahhh the Quantum Vacuum, the QV. If there wasn't so much evidence that it exists as appearing and disappearing particles and forces from somewhere out of the planck levels of space and possible links into another dimension of space time, I'd think QV is a Genie in the bottle.
Reading about the QV http://en.wikipedia.org/wiki/Vacuum_state
What is that time period I need to "give it back"? a femtosecond, 1 week, a couple years, the forecast age of the universe? I'm not sure if it is a set time as we see it. And what if I warped, just a little and just enough spacetime with an EM field, would that have an effect of the borrowed time and during that time I had it couldn't I just strip of a little something extra before I gave it back?
My head is feeling a little mushy and I think I need some hot tub time with something cold.
To all, thanks for putting up with me and my crackpot ideas of our world.
I asked this question here because when I told my grandson who is in first year engineering asked me almost this very same question.  I said virtual particles really don't exist except in calculations and mostly are not or can not be observed in the real world. He sent me this from Wikipedia and said not true. Could anyone help me here to put this into a easier form to understand? Thanks
http://en.wikipedia.org/wiki/Virtual_particle
Manifestations[edit]
There are many observable physical phenomena that arise in interactions involving virtual particles. For bosonic particles that exhibit rest mass when they are free and actual, virtual interactions are characterized by the relatively short range of the force interaction produced by particle exchange.[citation needed] Examples of such short-range interactions are the strong and weak forces, and their associated field bosons. For the gravitational and electromagnetic forces, the zero rest-mass of the associated boson particle permits long-range forces to be mediated by virtual particles. However, in the case of photons, power and information transfer by virtual particles is a relatively short-range phenomenon (existing only within a few wavelengths of the field-disturbance, which carries information or transferred power), as for example seen in the characteristically short range of inductive and capacitative effects in the near field zone of coils and antennas.[citation needed]
Some field interactions which may be seen in terms of virtual particles are:
The Coulomb force (static electric force) between electric charges. It is caused by the exchange of virtual photons. In symmetric 3-dimensional space this exchange results in the inverse square law for electric force. Since the photon has no mass, the coulomb potential has an infinite range.
The magnetic field between magnetic dipoles. It is caused by the exchange of virtual photons. In symmetric 3-dimensional space this exchange results in the inverse cube law for magnetic force. Since the photon has no mass, the magnetic potential has an infinite range.
Electromagnetic induction. This phenomenon transfers energy to and from a magnetic coil via a changing (electro)magnetic field.
The strong nuclear force between quarks is the result of interaction of virtual gluons. The residual of this force outside of quark triplets (neutron and proton) holds neutrons and protons together in nuclei, and is due to virtual mesons such as the pi meson and rho meson.
The weak nuclear force - it is the result of exchange by virtual W and Z bosons.
The spontaneous emission of a photon during the decay of an excited atom or excited nucleus; such a decay is prohibited by ordinary quantum mechanics and requires the quantization of the electromagnetic field for its explanation.
The Casimir effect, where the ground state of the quantized electromagnetic field causes attraction between a pair of electrically neutral metal plates.
The van der Waals force, which is partly due to the Casimir effect between two atoms.
Vacuum polarization, which involves pair production or the decay of the vacuum, which is the spontaneous production of particle-antiparticle pairs (such as electron-positron).
Lamb shift of positions of atomic levels.
Hawking radiation, where the gravitational field is so strong that it causes the spontaneous production of photon pairs (with black body energy distribution) and even of particle pairs.
Much of the so-called near-field of radio antennas, where the magnetic and electric effects of the changing current in the antenna wire and the charge effects of the wire's capacitive charge may be (and usually are) important contributors to the total EM field close to the source, but both of which effects are dipole effects that decay with increasing distance from the antenna much more quickly than do the influence of "conventional" electromagnetic waves that are "far" from the source. ["Far" in terms of ratio of antenna length or diameter, to wavelength]. These far-field waves, for which E is (in the limit of long distance) equal to cB, are composed of actual photons. It should be noted that actual and virtual photons are mixed near an antenna, with the virtual photons responsible only for the "extra" magnetic-inductive and transient electric-dipole effects, which cause any imbalance between E and cB. As distance from the antenna grows, the near-field effects (as dipole fields) die out more quickly, and only the "radiative" effects that are due to actual photons remain as important effects. Although virtual effects extend to infinity, they drop off in field strength as 1/r2 rather than the field of EM waves composed of actual photons, which drop 1/r (the powers, respectively, decrease as 1/r4 and 1/r2). See near and far field for a more detailed discussion. See near field communication for practical communications applications of near fields.
Most of these have analogous effects in solid-state physics; indeed, one can often gain a better intuitive understanding by examining these cases. In semiconductors, the roles of electrons, positrons and photons in field theory are replaced by electrons in the conduction band, holes in the valence band, and phonons or vibrations of the crystal lattice. A virtual particle is in a virtual state where the probability amplitude is not conserved. Examples of macroscopic virtual phonons, photons, and electrons in the case of the tunneling process were presented by GŁnter Nimtz [9] and Alfons A. Stahlhofen.[10]

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5845
  • USA
  • Liked: 5927
  • Likes Given: 5270
...

NOTE: A structural Finite Element solution with a rigid body mode (free to translate in space) is singular, hence the matrix cannot be inverted.  What boundary conditions did she choose? How did she get rid of rigid body modes to get a Stress Tensor solution?    I also have to look at how she dealt with that (CoM)
Of course, the way she deals with this complexity is that she ignores it.  Prof. Yang did not calculate the stresses on a deformable EM Drive.  Yang considered the EM Drive to be an infinitely rigid solid, she did not perform an FEA of the deformation due to thermal strains caused by the dissipation.  This avoids having to deal with a singular matrix and taking out the rigid body modes.

Yang computed the Maxwell Stress tensor components from the electromagnetic field based on a solution of Maxwell's differential equations (taking into account dissipation) for an infinitely rigid EM Drive.   This explains why later she had to perform elaborate experiments by embedding thermocouples in the real, deformable, EM Drive (the first researcher to do so).

Yang's EM Drive must distort under the effect of the high input energy she uses, and this thermal deformation must make the EM Drive detune itself from the high Q resonance: hence her later effort to understand the thermal effects. Of coursse, we don't have her EM Drive dimensions, so we don't know how deformable it is. (The drawings and the fact that she was able to embed thermocouples in the walls make me feel that her EM Drive is much thicker than NASA's).

Also notice that NASA could not get any thrust without a dielectric insert using the same mode shape preferred by Yang: TE012 and that NASA could only perform one test with the dielectric (where they got the highest thrust/InputEnergy of any reported experiment) but they could not reproduce it consistently and they had to switch to TM212.  It looks to me that TE012 must result in thermal deformation of the cavity, particularly with the thinnness of copper used by NASA Eagleworks.  This results in NASA's thin EM Drive detuning itself.  Since NASA was not using a magnetron, NASA has more problems with this TE012 mode since it may result in greater thermal deformation of NASA's EM Drive than the deformation under the highr mode TM212.
« Last Edit: 05/24/2015 11:13 PM by Rodal »

Offline Flyby

  • Full Member
  • ***
  • Posts: 384
  • Belgium
  • Liked: 447
  • Likes Given: 47

My understanding so far of what he says is this;

First, refers to "thrust" as the EM field moving backwards, and "reaction" as the frustum moving forwards, toward the small end. His idea of thrust is that when the photons are reflected from the small end, the frustum goes forward, the photons go backwards, and momentum is exchanged on the bounce. When they reach the back wall, the effect is the opposite and now "thrust" is forward and "reaction" is backwards, toward the big end. These two reactions do not add to zero. This is why it is not only confusing to read it, but to understand it. Thrust and reaction are both bi-directional, but their sum is not zero.

aahhh... that would make sense...
basically he's describing the radiation pressure on both front and back plate...
http://en.wikipedia.org/wiki/Radiation_pressure#/media/File:Sail-Force1.gif

damn..you really have a gift of writing things out in a clear and layman-understandable way...

but from a radiation pressure point of view, part of the big plate and the totality of the front plate nullify each other, so if there is a difference to be observed, shouldn't it be in the difference between the angled sides and the small left over of (big plate - small plate)?

The fact that the sidewalls are angled give me the impression that electromagnetic waves will bounce more often on the sidewalls of the frustum when going towards the small end, then when going towards the big end.
This is because reflection angles on the sidewalls are steeper when going to the small end, and more shallow going the other direction.

Now... a silly idea/question...

but is the size of a force/momentum truly linear with the angle of incidence?
cause, if a force would be a bit less then linear for a shallow angle, that could account for the residual force towards the small end?
Are there any studies about momentum/force transfer for electromagnetic waves when reflected?

Probably talking nonsense here, but you never know, even a blind man can hit a target.. :-[
« Last Edit: 05/24/2015 11:09 PM by Flyby »

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1364
If Yang "nailed it" with "no new physics", which of Noether or Einstein did she decide to trash? Because you have to choose, and either way, it's new physics. To recap: for the free motion:

1. If P = F v, then magically v is known, which implies a preferred rest frame, and Einstein shrieks
2. If P = F = constant, then free energy is available in profusion, and Noether shrieks.

No new physics?

No. 2 is not quite correct since all of the "free energy" schemes have circular terms in the Hamiltonian and only the acceleration to spacial seperation looks that way.  Noether snoozes.
Well, in that case I must ask you to go through my equations and to spot the error.

? ? ? http://emdrive.echothis.com/Theory ?

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
If Yang "nailed it" with "no new physics", which of Noether or Einstein did she decide to trash? Because you have to choose, and either way, it's new physics. To recap: for the free motion:

1. If P = F v, then magically v is known, which implies a preferred rest frame, and Einstein shrieks
2. If P = F = constant, then free energy is available in profusion, and Noether shrieks.

No new physics?

No. 2 is not quite correct since all of the "free energy" schemes have circular terms in the Hamiltonian and only the acceleration to spacial seperation looks that way.  Noether snoozes.
Well, in that case I must ask you to go through my equations and to spot the error.

? ? ? http://emdrive.echothis.com/Theory ?
Nope.
Well, in that case I must ask you to go through my equations and to spot the error. :)

Online WarpTech

  • Full Member
  • ****
  • Posts: 1229
  • Do it!
  • Vista, CA
  • Liked: 1296
  • Likes Given: 1754
...Great video.  It touches on so many topics that get discussed here on this forum.

...I thoroughly enjoyed this, Thanks Dr. Rodal!!!
As PhaseShift said it is interesting how this video deals with a number of topics we have been discussing.  For example, the question is asked (by somebody at CERN) to Sundrum as to whether there is a relation of the extra dimension(s) to the Quantum Vacuum virtual particles.  The answer is that this is unknown.  They are using Heisenberg's uncertainty principle as a given.  Sundrum emphasizes the fact that we can borrow much larger amounts of energy than we own (no need of collateral) but that you have to pay it back in an extremely small amount of time.  They are using this ability to borrow larger energy from the QV in their experiments to explore energy being lost in the extra dimension(s). Thus, the issue with Dr. White's proposal is the need to payback, in a very small amount of time, any energy you may borrow (the QV being immutable and non-degradable over longer periods of time).  Essentially, Dr. White's proposal is that one can default on the mortgage  :)
Ahhh the Quantum Vacuum, the QV. If there wasn't so much evidence that it exists as appearing and disappearing particles and forces from somewhere out of the planck levels of space and possible links into another dimension of space time, I'd think QV is a Genie in the bottle.
Reading about the QV http://en.wikipedia.org/wiki/Vacuum_state
What is that time period I need to "give it back"? a femtosecond, 1 week, a couple years, the forecast age of the universe? I'm not sure if it is a set time as we see it. And what if I warped, just a little and just enough spacetime with an EM field, would that have an effect of the borrowed time and during that time I had it couldn't I just strip of a little something extra before I gave it back?
My head is feeling a little mushy and I think I need some hot tub time with something cold.
To all, thanks for putting up with me and my crackpot ideas of our world.
I asked this question here because when I told my grandson who is in first year engineering asked me almost this very same question.  I said virtual particles really don't exist except in calculations and mostly are not or can not be observed in the real world. He sent me this from Wikipedia and said not true. Could anyone help me here to put this into a easier form to understand? Thanks
http://en.wikipedia.org/wiki/Virtual_particle
(...)

QFT is even weirder than that! It must be thought of in terms of "information" rather than propagation. When an electron moves from point A to point B, it doesn't move through space-time. It is "annihilated" at point A and "created" at point B. Why? Because this is what we observed, what was at A is now at B, but we did not "observe" the particle between those 2 points, at the quantum scale. There are an infinite number of paths it could have taken, but we do not have that information. QM is based on what is observable, i.e. Heisenberg!

I think the best example is the DC electric field of a capacitor. It is conveyed by virtual photons. They can only be observed by the force they exert on charged matter, but in that regard, the "effects" of virtual particles are observable, if not the particles themselves.




Online WarpTech

  • Full Member
  • ****
  • Posts: 1229
  • Do it!
  • Vista, CA
  • Liked: 1296
  • Likes Given: 1754
...
aahhh... that would make sense...
basically he's describing the radiation pressure on both front and back plate...
http://en.wikipedia.org/wiki/Radiation_pressure#/media/File:Sail-Force1.gif

damn..you really have a gift of writing things out in a clear and layman-understandable way...

but from a radiation pressure point of view, part of the big plate and the totality of the front plate nullify each other, so if there is a difference to be observed, shouldn't it be in the difference between the angled sides and the small left over of (big plate - small plate)?

The fact that the sidewalls are angled give me the impression that electromagnetic waves will bounce more often on the sidewalls of the frustum when going towards the small end, then when going towards the big end.
This is because reflection angles on the sidewalls are steeper when going to the small end, and more shallow going the other direction.

Now... a silly idea/question...

but is the size of a force/momentum truly linear with the angle of incidence?
cause, if a force would be a bit less then linear for a shallow angle, that could account for the residual force towards the small end?
Are there any studies about momentum/force transfer for electromagnetic waves when reflected?

Probably talking nonsense here, but you never know, even a blind man can hit a target.. :-[

Thank you.

Shower uses the notion that the wave velocity is also different at the small end (slower) than at the big end. But then he uses special relativity to subtract the 2 velocities, and gets a NET force. His derivation is not correct on so many levels, but it is correct to say that the forces do not sum to zero.

You have the right idea. The taper toward the small end will offer greater attenuation than the taper toward the large end. The energy for Q is stored energy. As it is dissipated, that dissipation occurs asymmetrically.  The paper by Zeng & Fan show graphs of the attenuation factor at various taper angles and frequencies. Though they are referring to a waveguide, not a frustum cavity.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-17-1-34




Offline Rodal

  • Senior Member
  • *****
  • Posts: 5845
  • USA
  • Liked: 5927
  • Likes Given: 5270
Yang doesn't take the free dynamics bull by the horns.

Also, if she's using heat dissipation as an explanation, how does this system manage  not to be a photon rocket?

(...)

No idea how she can get Force/InputPower thousands of times better than perfect photon rocket.

(...)

Make Q a cyclic, time dependent, PWM duty cycle controlled function, not a constant!

It charges until it has enough thrust to overcome the resistance of the mass, but once it moves, that energy is dissipated. P drops back to Pin and Q has to build up again. I don't see any other way...

But looking at Yang's paper, she does not perform an ON-OFF duty cycle analysis of her EM Drive.  Her calculations are ON, steady state, harmonic, for indefinite amount of time.

So the question remains unanswered as to how her Finite Element calculations can result in a performance of her EM Drive thousands of times more efficient than a perfectly collimated  photon rocket.

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5845
  • USA
  • Liked: 5927
  • Likes Given: 5270
...
I asked this question here because when I told my grandson who is in first year engineering asked me almost this very same question.  I said virtual particles really don't exist except in calculations and mostly are not or can not be observed in the real world. He sent me this from Wikipedia and said not true. Could anyone help me here to put this into a easier form to understand? Thanks
...
Well, I prefer the answer given in the previous video by Randall's co-author Raman Sundrum ( http://forum.nasaspaceflight.com/index.php?topic=37642.msg1379064#msg1379064 ), but here is a Prof. that agrees with the answer you gave to your grandson, for another point of view (in case you didn't see it):

http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/
« Last Edit: 05/25/2015 12:25 AM by Rodal »

Offline SeeShells

  • Senior Member
  • *****
  • Posts: 2326
  • Every action there's a reaction we try to grasp.
  • United States
  • Liked: 2956
  • Likes Given: 2590
...
I asked this question here because when I told my grandson who is in first year engineering asked me almost this very same question.  I said virtual particles really don't exist except in calculations and mostly are not or can not be observed in the real world. He sent me this from Wikipedia and said not true. Could anyone help me here to put this into a easier form to understand? Thanks
...
Well, I prefer the answer given in the previous video by Randall's co-author Raman Sundrum ( http://forum.nasaspaceflight.com/index.php?topic=37642.msg1379064#msg1379064 ), but here is a Prof. that agrees with the answer you gave to your grandson, for another point of view (in case you didn't see it):

http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/
Thanks for the great links, I sent them to him and told him to read and study. I think he was trying to set old grandma up. ;)

Online WarpTech

  • Full Member
  • ****
  • Posts: 1229
  • Do it!
  • Vista, CA
  • Liked: 1296
  • Likes Given: 1754
...
She said; "(2) The calculation of the different modes and different cavity structure, the mode TM012 which has smallest cavity Large-End has the largest thrust, so has the highest quality factor and thrust. Mode TM011 thrusters has the worst performance."

So a narrower cone angle, and a TM012 mode. What's wrong with that? The TM011 mode is not bad, but requires a larger cone, so of course it will be weaker. I actually think this is theoretically correct.
...

The translation of Chinese to English seems to be low quality: the translation text states TM012 mode (as you wrote) but the original Chinese text reads TE012 instead (which is correct, as TM012 is at significantly higher frequency !!)
The original Table 1 in Chinese shows larger geometrical dimensions for mode TE012 than the geometrical dimensions used for TM011.

So, no the geometrical dimensions for mode TE012 and TM011 are such that the dimensions for TE012 were larger than for TM011.

Please take a gander and let me know what you think:


Looking at her chart, Figure 3, the TM012 mode should be a good one too, but I'll take your word for it.

The horizontal axis of Figure 3 is (D/L)^2, so a larger number indicates larger diameter, shorter length. It defines the aspect ratio of the two, not the physical dimensions. No? What am I missing?




Offline Rodal

  • Senior Member
  • *****
  • Posts: 5845
  • USA
  • Liked: 5927
  • Likes Given: 5270
..Looking at her chart, Figure 3, the TM012 mode should be a good one too, but I'll take your word for it.

The horizontal axis of Figure 3 is (D/L)^2, so a larger number indicates larger diameter, shorter length. It defines the aspect ratio of the two, not the physical dimensions. No? What am I missing?
I re-wrote my post:


The translation of Chinese to English seems to have issues: the translation text states TM012 mode (as you wrote) but the original Chinese text reads TE012 instead (which is correct).


They kept the small diameter constant and they considered different big diameters and heights.  The big diameter is a variable.

The original Table 1 in Chinese shows larger truncated cone heights for mode TE012 than the heights used for TM011.


I think that the translation should be:

Quote
(2) For the calculation of the different modes and different microwave cavity structures, for the mode TE012 the cavity which has the minimum diameter at the large end has the largest thrust and the highest quality factor. Mode TM011 thrusters has the worst performance. (3) As the Large-End diameter of the cavity increases, the height of cavity is reduced, cavity volume and wall surface area also reduced, leading to low quality factor and producing less thrust

Later on, in the last section, the translation states:

Quote
Calculation show that under the four modes, TE011, TE012, TE111 and TM011, the quality factor of TE012 is highest and with highest thrust, followed by TE011. With the Small End of the cavity unchanged, the quality factor and thrust decrease with the increase in the Large End

So, again best modes recommended by Prof. Yang are Transverse Electric TE012 followed by TE011, instead of the Transverse Magnetic modes recommended by Shawyer and the Transverse Magnetic mode (TM212) presently used by NASA.

Please take a gander and let me know what you think (notice that the table gives the "height" in mm of the truncated cone:

two heights were considered for TE012: 240 mm and 175 mm

two heights were considered for TM011: 150 mm and 122 mm

clearly TE012 and TE011 had the best numbers of all the modes considered (TE011, TE012, TE111 and TM011)

Notice that the heights of Prof. Yang's cavities are smaller than NASA's and Shawyer's



« Last Edit: 05/25/2015 03:12 AM by Rodal »

Online WarpTech

  • Full Member
  • ****
  • Posts: 1229
  • Do it!
  • Vista, CA
  • Liked: 1296
  • Likes Given: 1754
...
Looking at her chart, Figure 3, the TM012 mode should be a good one too, but I'll take your word for it.

The horizontal axis of Figure 3 is (D/L)^2, so a larger number indicates larger diameter, shorter length. It defines the aspect ratio of the two, not the physical dimensions. No? What am I missing?
But the vertical axis in Figure 3 does not appear to be thrust force, so how do you know that TM012 should be a good one?

And, when the time comes for her to calculate the thrust force (Table 2) she does not consider TM012

Okay, so my take on the vertical axis was that it represented Q somehow, but I admit it is unclear to me what that vertical axis represents. If it does represent Q, it shows that the TE012 mode cavity requires a longer length and smaller big diameter than the TM01 mode, for the same Q value. I'm assuming that is the case for the TM012 mode as well, showing it requires longer length and smaller big diameter than TM011 or TE111.

What's your take on it?

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5845
  • USA
  • Liked: 5927
  • Likes Given: 5270
...
Looking at her chart, Figure 3, the TM012 mode should be a good one too, but I'll take your word for it.

The horizontal axis of Figure 3 is (D/L)^2, so a larger number indicates larger diameter, shorter length. It defines the aspect ratio of the two, not the physical dimensions. No? What am I missing?
But the vertical axis in Figure 3 does not appear to be thrust force, so how do you know that TM012 should be a good one?

And, when the time comes for her to calculate the thrust force (Table 2) she does not consider TM012

Okay, so my take on the vertical axis was that it represented Q somehow, but I admit it is unclear to me what that vertical axis represents. If it does represent Q, it shows that the TE012 mode cavity requires a longer length and smaller big diameter than the TM01 mode, for the same Q value. I'm assuming that is the case for the TM012 mode as well, showing it requires longer length and smaller big diameter than TM011 or TE111.

What's your take on it?
Table 3, page 28 of the original Chinese paper shows:



Vertical Axis: ( (Frequency[Hz] * Diameter[cm] )/(Hz*cm) )2 * 10- 20



Horizontal Axis:  (Diameter / Height)2



I didn't have the time yet to chase what Diameter is she referring to.

To me it is a table for mode shapes in terms of natural frequency and geometry.

Let me know what you think
« Last Edit: 05/25/2015 02:53 AM by Rodal »

Offline zellerium

  • Full Member
  • *
  • Posts: 171
  • Pittsburgh, PA
  • Liked: 279
  • Likes Given: 400
I'm glad to see the discussion move away from Shawyer and back to examining the experiment by Yang; her apparatus seems to work the best, which probably contributes to her reluctance to share information. A friend of mine who recently moved from China has told me NWPU is heavily tied with the Chinese military, and has one of the best aerospace programs in the country. I sent a translated email to Dr. Yang on Monday with a few questions, but no response yet.

A couple interesting things I have noticed about her experiments:
The depiction of the input port of the frustum has changed a few times, from the center to closer to the top and bottom.
Does anyone know what year this first picture is from? [Edit: found the paper it came from here http://wulixb.iphy.ac.cn/EN/abstract/abstract60316.shtml but it isn't translated] I would guess it is a later design. The two rods look like some kind of tuning mechanism. It also looks like they have an adjustable aperture. Seems a lot like Todd's Conjecture to me, a symmetric resonant cavity to build up energy, and distribute it to the frustum to attenuate the wave. 

I've been looking into the different methods of power delivery and now I am leaning towards trying the setup by Yang first. (We'll have plenty of time to try other methods if it doesn't work out) I'm thinking we should put the magnetron antenna directly inside an aluminum tube (through the side to activate the TE modes)  which feeds to the frustum at 15% of the height from the large end. We could have an adjustable plate on the inside of the tube as well as the frustum to change lengths. I'm still trying to figure out if we can put a magnetron in our vacuum chamber, I expect overheating to be an issue. Also I believe the casing is made of steel which our professor won't allow in the chamber because of outgassing. Backup plan is to use an intermediate cavity to convert magnetron output to coax and feed that into the chamber.   

By the way, Cal Poly Connect has given us the full amount of funding we requested, enough to rent a signal generator, 50 W amp, and a spectrum analyzer. We also have extra money to try some different dimensions and we're working on getting the RF module of COMSOL. We're not going to rent the equipment until after we have already tried using the magnetron because the resolution of our thrust measurement system is estimated ~1 mN at best. A clean signal at 50 W probably won't give us anything we can see.
 
We're putting together a summary of our experimental design that I'll post in the next couple of days.

Happy to see everyone still thinking  :)

Kurt
« Last Edit: 05/25/2015 03:59 AM by zellerium »

Tags: