Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2141298 times)

Offline Mulletron

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This does fit (as far as I've gotten) the concept of a self-accelerating Dirac wavepacket (which does conserve momentum).
...
Please tell us more when you have a chance about the <<self-accelerating Dirac wavepacket (which does conserve momentum)>> as conservation of momentum has been the biggest problem of the scientific media (Prof. Baez and Sean Carroll for example) and with the serious science-fiction media (Greg Egan) with the EMDrive.  How does momentum get conserved in the EMDrive when there is nothing coming out of the EM Drive?

http://physics.stackexchange.com/questions/160702/self-accelerating-wavepackets-what-are-they-and-can-they-impulse-a-spaceship

http://www.nature.com/nphys/journal/vaop/ncurrent/fig_tab/nphys3196_F1.html

http://newsoffice.mit.edu/2015/self-accelerating-particles-0120

Or are you considering that evanescent waves coming out of the EM Drive in outer space (with no fields or matter nearby to interact with) are responsible for conservation of momentum with an effectiveness much greater than a photon rocket?

This is certainly interesting but there are no "specially engineered phase masks" in Emdrive.

Same people: http://arxiv.org/pdf/1205.2112.pdf
« Last Edit: 02/17/2015 11:00 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Online aero

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...
So what do you propose as a resolution to your critique?
Same thing I proposed here:

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1332813#msg1332813

.. it is critical, to assess results of a numerical solution, to compare the results of a numerical solution (for example Finite Difference method) to an exact solution.  In this case, an exact solution to a cylindrical cavity exists  (http://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity), and it would be worthwhile to compare how far is the MEEP solution for a resonant cylindrical cavity, say of a diameter=Sqrt[BigDiameterOfTruncatedCone * SmallDiameterOfTruncatedCone]=0.21060 m and same axial length, with the same material inputs and mesh as used for the Finite Difference solution of the Truncated Cone.
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I propose a MEEP analysis for a resonant cylindrical cavity (no dielectric), with  diameter=Sqrt[BigDiameterOfTruncatedCone * SmallDiameterOfTruncatedCone] and same axial length=0.2286 m as the NASA cavity, with the same material inputs and mesh as you used for the Finite Difference solution of the Truncated Cone. 


Actual geometry
Large OD : 11.00 " (0.2794m),
Small OD: 6.25" (0.1588 m)
Length : 9.00 " (0.2286m)
Geometric Mean Diameter: 0.2106056741875679 m


If the MEEP mesh for the truncated cone cannot be used to obtain a  MEEP solution close to the exact solution for a cylindrical cavity of similar dimensions (an easier problem to solve than the truncated cone), then that mesh and solution (2D?) cannot get a reliable solution for the EM Drive truncated cone, concerning EM Drive for space flight applications. (The cylindrical cavity is an easier problem because the mode shapes are either purely resonating (real solutions) or evanescent (imaginary solutions) while for a truncated cone there are modes that go from resonating to evanescent, and because the truncated cone displays interesting attenuation and focusing properties).

As you must know, there are several more-or-less independent modules in meep. The core FDTD algorithm that we should be concerned about is not the same as the Harminv algorithm which determines resonance frequencies and as you know, is suspect, at least by me and Dr. Dominic and I think, yourself. Proving again that the Harminv module is suspect will not show anything one way or the other about the core FDTD algorithm or the Flux and Forces modules. In other words, You already know the answer, so what is your point? 

In reading this I detect a hint of frustration, but I am.
Retired, working interesting problems

Offline Mulletron

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This is a goldmine of information concerning non-reciprocal materials!

http://arxiv.org/abs/1211.0530

The visual is to help communicate the concept.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

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As you must know, there are several more-or-less independent modules in meep. The core FDTD algorithm that we should be concerned about is not the same as the Harminv algorithm which determines resonance frequencies and as you know, is suspect, at least by me and Dr. Dominic and I think, yourself. Proving again that the Harminv module is suspect will not show anything one way or the other about the core FDTD algorithm or the Flux and Forces modules. ....

If the MEEP mesh discretization (distance between nodes and time increment between steps, and type of finite difference operator) used for the truncated cone cannot also be used to obtain a MEEP solution close to the exact solution for a cylindrical cavity of similar dimensions (an easier problem to solve than the truncated cone), then that mesh and solution (2D?) cannot get a reliable solution for the EM Drive truncated cone, concerning EM Drive for space flight applications. 

We shouldn't accept that the reason is due to anything wrong with the Harminv module, the reason may be inherent with the finite difference discretization (and 2D?) model being used I only recently realized that you are using a 2-D model instead of 3-D model. If your cavity analysis was also 2-D I would focus more on the fact that the 2-D model is modeling the cavity as a flat rectangle instead of a 3D cylinder. It would be incorrect to assume that Maxwell's equations in 2D would give similar results as Maxwell's equations in 3D

If the  cylinder was modeled as 3-D and results were obtained far away from the exact solution for a cylindrical cavity and you suspect Harminv, then what should be done is to conduct a time-stepping solution, going through the initial transient state until a steady state solution is obtained.  The frequency and mode shapes can then be obtained from inspecting the data output from MEEP, instead of relying on Harminv.  Actually if the problem would be nonlinear, for example, you would not be allowed to use Harminv anyway and you would have to resort precisely to this type of analysis: examining the response until a steady state is obtained to then ascertain the frequency and mode shape.

Once a good comparison with MEEP has been obtained for the easier problem of the cylindrical cavity which has a simple exact solution, one can then proceed to the more difficult problem of the truncated cone, to have confidence in the solution as applicable to EM Drive for space flight applications. 
« Last Edit: 02/18/2015 01:40 AM by Rodal »

Offline Notsosureofit

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This does fit (as far as I've gotten) the concept of a self-accelerating Dirac wavepacket (which does conserve momentum).
...
Please tell us more when you have a chance about the <<self-accelerating Dirac wavepacket (which does conserve momentum)>> as conservation of momentum has been the biggest problem of the scientific media (Prof. Baez and Sean Carroll for example) and with the serious science-fiction media (Greg Egan) with the EMDrive.  How does momentum get conserved in the EMDrive when there is nothing coming out of the EM Drive?

http://physics.stackexchange.com/questions/160702/self-accelerating-wavepackets-what-are-they-and-can-they-impulse-a-spaceship

http://www.nature.com/nphys/journal/vaop/ncurrent/fig_tab/nphys3196_F1.html

http://newsoffice.mit.edu/2015/self-accelerating-particles-0120

Or are you considering that evanescent waves coming out of the EM Drive in outer space (with no fields or matter nearby to interact with) are responsible for conservation of momentum with an effectiveness much greater than a photon rocket?

This is certainly interesting but there are no "specially engineered phase masks" in Emdrive.

Same people: http://arxiv.org/pdf/1205.2112.pdf

Ahhh, but there are, they are the boundary conditions set by the cavity walls. 

Offline Mulletron

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Quote
It has been recently argued that the
quantum vacuum can possess momentum
http://arxiv-web3.library.cornell.edu/abs/0908.4390

As far as the theoretical side of things, as the Emdrive isn't ejecting anything and appears to violate conservation of momentum, we need to critically examine the above quote.

Experimental replications of Emdrive seem to suggest it is gaining momentum via unconventional means; like the quantum vacuum or somewhere else.

If the vacuum can be shown to possess momentum, as the authors claim, we are in business.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Notsosureofit

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This is a goldmine of information concerning non-reciprocal materials!

http://arxiv.org/abs/1211.0530

The visual is to help communicate the concept.

Yes, this is a goldmine to be explored !!!

Offline Mulletron

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Quote
It has been recently argued that the
quantum vacuum can possess momentum
From the most basic concepts, I argue that yes the quantum vacuum can possess momentum.



Can one gain momentum from the quantum vacuum? NO. Due to the universal symmetry of the quantum vacuum...........Can anyone else venture to guess which two combined symmetries you have to break in order to gain momentum from the QV?

Out of the 3 to choose from, Charge, Parity, and Time.....which two have multiple researchers saying you can gain momentum from the QV by breaking?


Edit: It's PT. I have been saying for months now that you can't gain momentum from the QV under normal symmetry conditions. And that research from multiple parties suggests that if you simultaneously break PT symmetry of the vacuum, you can gain momentum from the QV. The multiple replications of Emdrive are experimental evidence which support their claims that it is in fact possible to gain momentum from the QV, and that arguments claiming Emdrive violates conservation of momentum are false. The conditions inside Emdrive fit the theory, and theory and experiment reinforce each other.
« Last Edit: 02/18/2015 04:57 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline mvpel

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You should reach out to the Center for High-Throughput Computing at the University of Wisconsin. They've got a statewide federation of computing resources that's been used, for example, to find new radio pulsars in Arecibo data.
http://einstein.phys.uwm.edu/forum_thread.php?id=10397
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline Notsosureofit

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FYI before bed:

Noticed that the ratio of work done (from start to static peak) versus energy (per photon on the 50W, Q=6726) was ~7x10-5 ??

Pretty small % or did I miscalculate ?

Sunrise: Probably should be half that. (integrating against linear spring)

The curve "looks like" a sudden rise followed by a (thermal?) drift through the resonance.

The power output in that initial rise looks (very roughly) like 3x10-7 W.

Back when I was driving cavities (and Hector was a pup) I used a double balanced modulator to lock the half power points of the resonance using the "bow tie" display.  No "rotation", meant the center freq was correct and a minimum of the "crossing point" meant the bandwidth was correct.  This gave "precision" measurements of the resonances.  The freq standard then was the LORAN station on Cape Cod !  (this was for transport property measurements in gases)  The odd thing that sticks in my mind was that von Hipple at MIT wanted to apply the techniques to "an idea" he had for RF cavities, but he never got funding.  (and he never said what the idea was)

Just musings over coffee.............

« Last Edit: 02/18/2015 11:51 AM by Notsosureofit »

Offline Mulletron

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I've tried to understand the totality of the emdrive mystery in a lot of different ways ranging from it being pure bs to some quirk with inertia. The only way it makes sense is to apply that "momentum from the qv" theory I've been going on about. It is the only one left that still passes the smell test and doesn't try and overturn established science. It seems like a perfect fit for the conditions and two unconnected teams of researchers make the same claims.

Most importantly, it makes falsifiable predictions.
« Last Edit: 02/18/2015 08:00 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline ChrisWilson68

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I've tried to understand the totality of the emdrive mystery in a lot of different ways ranging from it being pure bs to some quirk with inertia. The only way it makes sense is to apply that "momentum from the qv" theory I've been going on about. It is the only one left that still passes the smell test and doesn't try and overturn established science. It seems like a perfect fit for the conditions and two unconnected teams of researchers make the same claims.

Most importantly, it makes falsifiable predictions.

Except that it *does* "try and overturn established science".  Momentum from the quantum vacuum is not compatible with generally accepted physics.

Unconnected teams can easily be mislead by similar mistakes.  Just look at how many independent observers claimed to see canals on the surface of Mars when they were on the edge of the signal/noise boundary of optical telescopes.

Offline Star One

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I've tried to understand the totality of the emdrive mystery in a lot of different ways ranging from it being pure bs to some quirk with inertia. The only way it makes sense is to apply that "momentum from the qv" theory I've been going on about. It is the only one left that still passes the smell test and doesn't try and overturn established science. It seems like a perfect fit for the conditions and two unconnected teams of researchers make the same claims.

Most importantly, it makes falsifiable predictions.

Except that it *does* "try and overturn established science".  Momentum from the quantum vacuum is not compatible with generally accepted physics.

Unconnected teams can easily be mislead by similar mistakes.  Just look at how many independent observers claimed to see canals on the surface of Mars when they were on the edge of the signal/noise boundary of optical telescopes.

No it doesn't necessarily try and overturn establish science. Your example of canals on Mars is not really relevant to the experimental work seen on this thread.

Offline Mulletron

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Well it has been accepted for publication at least.
http://iopscience.iop.org/0953-8984/page/Forthcoming%20articles#Special_isCasimir_fo

And the other citations are already published.
http://lpm2c.grenoble.cnrs.fr/spip.php?page=publications&id_auteur=18&clepubli=van%20Tiggelen&lang=fr

So we're not dealing with a crank here.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Star One

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Well it has been accepted for publication at least.
http://iopscience.iop.org/0953-8984/page/Forthcoming%20articles#Special_isCasimir_fo

And the other citations are already published.
http://lpm2c.grenoble.cnrs.fr/spip.php?page=publications&id_auteur=18&clepubli=van%20Tiggelen&lang=fr

So we're not dealing with a crank here.

Well unfortunately anything that seems a radical step forward in an area can attract proclamations of crank science even when not warranted.

That first link keeps coming up invalid parameters?
« Last Edit: 02/18/2015 12:25 PM by Star One »

Offline Star-Drive

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Folks:

While you all talk about various ways to accomplish the E&M simulations of these frustum cavities, I thought you might like to take a look at the COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity driven with a ~16mm OD loop antenna located 15% up the side wall of the frustum from the large OD end of the cavity. 

BTW, the EMPower amplifiers were delivered to the Lab yesterday and I'll be calibrating the power metering for one that was installed yesterday on the torque pendulum.

Best, Paul M,
Star-Drive

Offline Rodal

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Folks:

While you all talk about various ways to accomplish the E&M simulations of these frustum cavities, I thought you might like to take a look at the COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity driven with a ~16mm OD loop antenna located 15% up the side wall of the frustum from the large OD end of the cavity. 

BTW, the EMPower amplifiers were delivered to the Lab yesterday and I'll be calibrating the power metering for one that was installed yesterday on the torque pendulum.

Best, Paul M,

Thank you, Paul, for posting this, the attached pdf with COMSOL plots (which I first missed, my bad, thanks to Mulletron for pointing it out to me  :) ) is very useful for all of us (those like me working on the exact solution of the frustum, and those working with numerical methods like MEEP, COMSOL, ANSYS-multiphysics, etc.).

I could not find in the pdf attached to your post, or in your post. language to indicate whether the COMSOL calculations in the attachment (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=796287) include or do not include a dielectric inside the truncated cone (frustum). My impression is that these COMSOL calculations do not include the dielectric inside the truncated cone (this impression is based on the frequency calculated for TE012).

Still a clarification for some readers like me, may be useful (to those to whom what I write below is obvious, please forgive me for taking your time):




1) Clarification: the jpg image you posted are not "COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity", the COMSOL plots are in the pdf attached to your post (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=796287)

2) The mode shapes in the slide are for a different geometry: a circular waveguide (instead of a truncated cone/frustum like NASA's EM Drive) , that had been plotted in published journals since 1936, without using a digital computer. The actual reference's date is 1985 (instead of 1966): http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1132998.  Since COMSOL was started in 1986, Lee, Lee and Chuang did not use COMSOL: they had no need to use a finite element program, because an exact solution exists for what they plotted: the mode shapes of a circular waveguide.

The circular waveguide exact solution is present in the 1943 textbook by Schelkunoff, and in papers he published in the 1930's.  The mode shapes look identical to the plots that Schelkunoff published in the 1930's without the benefit of a digital computer: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1332981#msg1332981.  The article by Lee, Lee and Chuang states: "The earliest plots of modal field distribution in rectangular/circular waveguides were given by Southworth (1936), Barrow (1936), Schelkunoff (1937), and Chu and Barrow (1937)"

3) The solution for a truncated cone (the geometry of the NASA frustum, and the geometry analyzed by COMSOL in the attached pdf) is different from the solution for a circular waveguide in several respects: the natural frequencies are quite different, and while in a circular waveguide different mode shapes are either resonant or cutoff, in a truncated cone some mode shapes are resonant, some are evanescent and some have a transition from resonant to evanescent (a characteristic not present in circular waveguides).  Also, the attenuation and focusing aspects of the truncated cone (frustum) are not present in the circular waveguide.

« Last Edit: 02/18/2015 03:29 PM by Rodal »

Offline JasonAW3

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Ok, maybe I'm a bit slower than I ought to be lately, but are you guys telling us that they are, essentially, developing a propellentless thrust system based on a RADAR SYSTEM?
My God!  It's full of universes!

Offline Mulletron

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Ok, maybe I'm a bit slower than I ought to be lately, but are you guys telling us that they are, essentially, developing a propellentless thrust system based on a RADAR SYSTEM?

You never noticed that the ship rocks harder when the radars are turnin' and burnin'? Shoot, they should just sector SPY back aft and cut the engines. :-)

http://en.wikipedia.org/wiki/Arleigh_Burke-class_destroyer

Based on electromagnetic waves. Waveguide are found in numerous applications besides radars. Sorry back on topic...
« Last Edit: 02/18/2015 02:05 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Notsosureofit

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Ok, maybe I'm a bit slower than I ought to be lately, but are you guys telling us that they are, essentially, developing a propellentless thrust system based on a RADAR SYSTEM?

You never noticed that the ship rocks harder when the radars are turnin' and burnin'? Shoot, they should just sector SPY back aft and cut the engines. :-)

http://en.wikipedia.org/wiki/Arleigh_Burke-class_destroyer

Based on electromagnetic waves. Waveguide are found in numerous applications besides radars. Sorry back on topic...

Wasn't that how Shawyer got the idea, only from a satellite not a ship?


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