Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2098626 times)

Offline Mulletron

  • Full Member
  • ****
  • Posts: 1106
  • Liked: 774
  • Likes Given: 1007
This old dog has to be dealt with. There isn't much left besides this:

Thermal instability technical paper from Rodal:
http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293349#msg1293349

« Last Edit: 02/12/2015 08:11 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
This old dog has to be dealt with. There isn't much left besides this:

Thermal instability technical paper from Rodal:
http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293349#msg1293349
Agreed, all that NASA Eagleworks has to do to eliminate this artifact is:

...get rid of the fiber-reinforced-polymer printed circuit board and just simply use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329239#msg1329239

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329424#msg1329424
« Last Edit: 02/12/2015 08:16 PM by Rodal »

Offline Giovanni DS

  • Regular
  • Full Member
  • *
  • Posts: 186
    • ChibiOS/RT Project
  • Liked: 44
  • Likes Given: 162
I have a question about how the thrust is usually measured. Is it a pendulum? if so, could a physical cavity deformation simply move the barycenter? that could be mistaken as thrust.

Far from being an expert, I am still enjoying the thread :)

Offline Mulletron

  • Full Member
  • ****
  • Posts: 1106
  • Liked: 774
  • Likes Given: 1007
What I don't understand still is how that thermal buckling could appear as a sustained false thrust signature over 30-45 second runs, instead of just a quick impulse. Is it because the CG moved or something?
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
I have a question about how the thrust is usually measured. Is it a pendulum? if so, could a physical cavity deformation simply move the barycenter? that could be mistaken as thrust.

Far from being an expert, I am still enjoying the thread :)

It is a horizontal torsional pendulum, with the torsional axis of rotation in the vertical direction  (call it "z"), paralel to the direction of the force of gravity and hence perpendicular to the floor.  The EM Drive's force produces a rotation around that vertical axis "z", such that the motion of the EM Drive occurs mainly in the x-y plane parallel to the floor, perpendicular to "z".   There is a small amount of coupling between the rotations around z, rotation around x and rotation around y due to the moments of inertia.  I wrote a program in Mathematica taking into account the nonlinear coupled equations of motion, thinking that the forces could be an artifact due to nonlinear coupling of the equations of motion but I after comparing with the data I rejected that possibility.
« Last Edit: 02/12/2015 08:35 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
What I don't understand still is how that thermal buckling could appear as a sustained false thrust signature over 30-45 second runs, instead of just a quick impulse. Is it because the CG moved or something?
Yes, good question.  For a perfectly elastic pendulum it should restore itself, as you say.  For it to persist for 45 seconds, one needs to posit some nonlinear non-conservative mechanism, perhaps in the nonlinear coupled equations of motion or perhaps also involving parasitic electromagnetic effects.

EDIT: There is another explanation that was offered by Oak Ridge involving thermal expansion, shifting the center of mass, we should discuss that sometime... (Thermal expansion is slower, but it could be that the answer is due to 1) thermal buckling (fast) + 2) thermal expansion (slower))
« Last Edit: 02/12/2015 08:44 PM by Rodal »

Offline SleeperService

  • Member
  • Posts: 48
  • Liked: 15
  • Likes Given: 15
I have a question about how the thrust is usually measured. Is it a pendulum? if so, could a physical cavity deformation simply move the barycenter? that could be mistaken as thrust.

Far from being an expert, I am still enjoying the thread :)

It is a horizontal torsional pendulum, with the torsional axis of rotation in the vertical direction  (call it "z"), paralel to the direction of the force of gravity and hence perpendicular to the floor.  The EM Drive's force produces a rotation around that vertical axis "z", such that the motion of the EM Drive occurs mainly in the x-y plane parallel to the floor, perpendicular to "z".   There is a small amount of coupling between the rotations around z, rotation around x and rotation around y due to the moments of inertia.  I wrote a program in Mathematica taking into account the nonlinear coupled equations of motion, thinking that the forces could be an artifact due to nonlinear coupling of the equations of motion but I after comparing with the data I rejected that possibility.
Could you share your Mathmatica code nevertheless?

Offline Star One

  • Senior Member
  • *****
  • Posts: 7969
  • UK
  • Liked: 1274
  • Likes Given: 168

This old dog has to be dealt with. There isn't much left besides this:

Thermal instability technical paper from Rodal:
http://forum.nasaspaceflight.com/index.php?topic=29276.msg1293349#msg1293349
Agreed, all that NASA Eagleworks has to do to eliminate this artifact is:

...get rid of the fiber-reinforced-polymer printed circuit board and just simply use a 1/4  inch thick (0.25 inches) copper plate for flat ends to prevent this thermal instability, and hence eliminate this artifact from consideration

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329239#msg1329239

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329424#msg1329424

Be interested to hear Star Drive's response to that particular enquiry.

Offline SleeperService

  • Member
  • Posts: 48
  • Liked: 15
  • Likes Given: 15
I think we are getting close to a truth here...

Offline aero

  • Senior Member
  • *****
  • Posts: 2736
  • 92129
  • Liked: 704
  • Likes Given: 235
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 1.937115E+009 Hz. This would compare directly to the situation presented yesterday, except the dielectric has been removed.

I note that by watching the development of the fields from the first half-period, the cavity resonance does not seem to be as strong. That is, the fields drift with time. The strong blue point moves.
Retired, working interesting problems

Offline aero

  • Senior Member
  • *****
  • Posts: 2736
  • 92129
  • Liked: 704
  • Likes Given: 235
Something I should mention. In watching the development of the evanescent waves and the propagating waves within the cavity, I can see no evidence that one moves any faster than the other.

I think what that means is that as soon as the evanescent wave exits the gap in the end plates, its velocity reverts to the classic solution. The equations needed to determine this are in the paper I referenced yesterday,
http://wwwsis.lnf.infn.it/pub/INFN-FM-00-04.pdf though it would take some tinkering to formulate them to correctly make this determination.

Anyone want to tackle that problem?
Retired, working interesting problems

Offline aero

  • Senior Member
  • *****
  • Posts: 2736
  • 92129
  • Liked: 704
  • Likes Given: 235
@ Rodal
Quote
For a perfectly cylindrical resonator we have a simple exact solution (see:  http://en.wikipedia.org/wiki/Microwave_cavity#Cylindrical_cavity ) all that one needs to do is to compare the frequency calculated by MEEP for a cylindrical cavity with the exact solution.

Yes, that fact was used in Dr. Dominic's analysis. However, he also wanted to verify that the meep fields were as they were supposed to be and not the cause of the discrepancy. They are OK and peaks match the cylindrical cavity resonance frequencies nicely.
Retired, working interesting problems

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 1.937115E+009 Hz. This would compare directly to the situation presented yesterday, except the dielectric has been removed.

I note that by watching the development of the fields from the first half-period, the cavity resonance does not seem to be as strong. That is, the fields drift with time. The strong blue point moves.

You calculated a force with the dielectric in the cavity,


what force do you calculate without the dielectric?


How does the force compare?
« Last Edit: 02/12/2015 10:10 PM by Rodal »

Offline aero

  • Senior Member
  • *****
  • Posts: 2736
  • 92129
  • Liked: 704
  • Likes Given: 235
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 1.937115E+009 Hz. This would compare directly to the situation presented yesterday, except the dielectric has been removed.

I note that by watching the development of the fields from the first half-period, the cavity resonance does not seem to be as strong. That is, the fields drift with time. The strong blue point moves.

You calculated a force with the dielectric in the cavity, what force do you calculate without the dielectric?

How does the force compare?

Interesting question.

That is another time consuming computer job. I might have answers for you tonight, if not, tomorrow.
Retired, working interesting problems

Offline Mulletron

  • Full Member
  • ****
  • Posts: 1106
  • Liked: 774
  • Likes Given: 1007

I accidentally stumbled upon this report:
https://hal.archives-ouvertes.fr/hal-00551421v1/document

I'm still trying to find which reference it was where any of this implied non-reciprocity.

It does imply non-reciprocity:

http://arxiv.org/pdf/1101.1174v1.pdf
Section 2.1.
Quote
Magneto-electric directional anisotropy can be induced in all media, including centrosymmetric
ones. It was first predicted by G. E. Stedman and coworkers [11] and observed for the first time in
a crystal by G. L. J. A. Rikken and coworkers [12]. This non-reciprocal effect is supposed to be independent on light polarization.

I'm sure any optics expert would tell me, well duh!
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245

I accidentally stumbled upon this report:
https://hal.archives-ouvertes.fr/hal-00551421v1/document

I'm still trying to find which reference it was where any of this implied non-reciprocity.

It does imply non-reciprocity:

http://arxiv.org/pdf/1101.1174v1.pdf
Section 2.1.
Quote
Magneto-electric directional anisotropy can be induced in all media, including centrosymmetric
ones. It was first predicted by G. E. Stedman and coworkers [11] and observed for the first time in
a crystal by G. L. J. A. Rikken and coworkers [12]. This non-reciprocal effect is supposed to be independent on light polarization.

I'm sure any optics expert would tell me, well duh!

Yes. 

I also read the (C. Robilliard and G. Bailly) paper (Table 1) as stating that the calculated magneto-electric linear birefringence MELB = nB − nE for the Quantum Vacuum is  3*10^(-10) of the value for Nitrogen: ten orders of magnitude smaller for the Quantum Vacuum than for Air.
« Last Edit: 02/12/2015 10:47 PM by Rodal »

Offline aero

  • Senior Member
  • *****
  • Posts: 2736
  • 92129
  • Liked: 704
  • Likes Given: 235
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 2.168E+009Hz. In this case, dielectric has been removed and the drive frequency has been increased. Increased drive frequency means that the actual simulated time is less than in the previous cases because the period is shorter.
Retired, working interesting problems

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5831
  • USA
  • Liked: 5897
  • Likes Given: 5245
Attached find the fields from the Copper Kettle at the 32-nd half-period of the drive frequency, 2.168E+009Hz. In this case, dielectric has been removed and the drive frequency has been increased. Increased drive frequency means that the actual simulated time is less than in the previous cases because the period is shorter.
Thanks. It appears then that the evanescent fields are strong and unsymmetric (fore and aft of the EM Drive) with a resonant cavity with the dielectric at 1.9 GHz





The evanescent fields are weaker and their intensity much more symmetric (fore and aft of the EM Drive) with the dielectric removed at the same frequency 1.9 GHz.  There is no strong resonance now because with the dielectric removed the natural frequencies for the same mode shapes occur at higher frequencies.




With the dielectric removed, at the higher frequency of 2.1 GHz, the evanescent field intensities are unsymmetric again (fore and aft) like with the dielectric at 1.9 GHz but the fields don't seem to be as strong



1) You need to give us a contour field mapping rule: what do the colors mean in numerical terms, to further understand the contourplot. For example: what is the intensity of the white areas? of the red areas? of the orange areas? of the blue areas?

2) It would be great to get the forces on the center of mass of the EM Drive you compute for the three different cases
« Last Edit: 02/13/2015 12:08 AM by Rodal »

Offline Mulletron

  • Full Member
  • ****
  • Posts: 1106
  • Liked: 774
  • Likes Given: 1007
I think we have shown that both of these conditions have been met within EMdrive, which means that the research of Tiggelen, Rikken, Donaire and Shen directly apply to this.

http://arxiv-web3.library.cornell.edu/find/quant-ph/1/au:+Tiggelen_B/0/1/0/all/0/1
http://arxiv-web3.library.cornell.edu/find/quant-ph/1/au:+Rikken_G/0/1/0/all/0/1
http://arxiv-web3.library.cornell.edu/find/quant-ph/1/au:+Donaire_M/0/1/0/all/0/1
http://ptp.oxfordjournals.org/content/119/3/351.full.pdf

1) magneto-electric medium in crossed external fields
https://hal.archives-ouvertes.fr/hal-00551421v1/document (nitrogen)
http://arxiv.org/pdf/1101.1174v1.pdf (nitrogen, dielectrics)

2) chiral object in magnetic field
http://www.esrf.eu/UsersAndScience/Publications/Highlights/2011/scm/scm4
http://www.nature.com/srep/2013/130313/srep01444/full/srep01444.html
http://content.elsevierjournals.intuitiv.net/content/files/s003238610400713x-19125334.pdf
http://goo.gl/JegLXS
http://chemed.chem.purdue.edu/genchem/topicreview/bp/1polymer/terms.html

I am not implying this answers all the questions but I do think this is a significant lead in the right direction.
Source of slide http://qvg2013.sciencesconf.org/conference/qvg2013/program/Donaire_qvg2013.pdf

This also points the way toward ways of improving test results if this research does apply. It appears that only a weak coupling of QV momentum is present within the test article att.
1)Replace the pseudo-chiral PE with a truly chiral enantiopure material, preferably one exhibiting "strong magnetochiral dichroism"
2)Place the material in an area of highest magnetic field intensity.
3)Repressurize the cavity if possible.
4)Go back to TE012 mode.



Edit: added enantiopure and #4.
« Last Edit: 02/13/2015 05:01 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Mulletron

  • Full Member
  • ****
  • Posts: 1106
  • Liked: 774
  • Likes Given: 1007
Is there anything useful right now, today..... that can be done with an always on 50uN of thrust in space?
Challenge your preconceptions, or they will challenge you. - Velik

Tags: