Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1799122 times)

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
I think we should not entertain gossip about Eagleworks testing until Star-Drive re-appears, as engaging in such discussion may jeopardize NASA Eagleworks's ongoing efforts, giving NASA's response to the "warp-drive" media articles.

Understandable. Thanks!

There is a short-fim made about this (if you speak German, turn-off the sound and just read the English subtitles) :)   :

http://captiongenerator.com/48295/Hitler-Reacts-to-current-EmDrive-Situation

Hah, I saw that linked a while back, but only ever browse on my phone, so I never clicked it >_< I'll have to watch it after work.

Also, thinking more on the collision of photons, one source said they may form a matter/antimatter pair. If this source is accurate, and collisions are occurring, is it possible the formation and annihilation redirects the forces of the photons in some odd manner?

I apologize if I'm derailing the discussion, feel free to stop me at any point :)
Photons do scatter off one another, but the energy densities required are beyond experimental reach currently. PVAS is the European facility that promises to get closest to seeing at least some nonlinearities in the near future using extremely high-power lasers. For ordinary experiments, you might as well assume they don't see each other at all.
« Last Edit: 07/13/2015 04:56 PM by deltaMass »

Offline marshallC

  • Member
  • Posts: 10
  • Liked: 2
  • Likes Given: 25
I think we should not entertain gossip about Eagleworks testing until Star-Drive re-appears, as engaging in such discussion may jeopardize NASA Eagleworks's ongoing efforts, giving NASA's response to the "warp-drive" media articles.

Understandable. Thanks!

There is a short-fim made about this (if you speak German, turn-off the sound and just read the English subtitles) :)   :

http://captiongenerator.com/48295/Hitler-Reacts-to-current-EmDrive-Situation

Hah, I saw that linked a while back, but only ever browse on my phone, so I never clicked it >_< I'll have to watch it after work.

Also, thinking more on the collision of photons, one source said they may form a matter/antimatter pair. If this source is accurate, and collisions are occurring, is it possible the formation and annihilation redirects the forces of the photons in some odd manner?

I apologize if I'm derailing the discussion, feel free to stop me at any point :)
Photons do scatter off one another, but the energy densities required are beyond experimental reach currently. PVAS is the European facility that promises to get closest to seeing at least some nonlinearities in the near future using extremely high-power lasers. For ordinary experiments, you might as well assume they don't see each other at all.

And just to be sure, that includes considering the frustrum's shape being a wave-guide, correct? I'm not sure if that would make them more likely to connect, despite the small density.

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Give it up. EmDrive contains no black holes, cosmic strings, gravity anomalies, self-interacting photons, axions, WIMPs, MACHOs, pink unicorns or floobie-dust.

Although there might be some floobie-dust  8)
« Last Edit: 07/13/2015 05:04 PM by deltaMass »

Offline SeeShells

  • Senior Member
  • *****
  • Posts: 2326
  • Every action there's a reaction we try to grasp.
  • United States
  • Liked: 2956
  • Likes Given: 2588
I posted a Danger alert and it went poof. Summary as I'll try again, weird.

I asked why the shape of the calculated stress values were shaped around the antenna like they were, squeezed in the forward accelerating direction and flattened out to the sides.
It reminds me of Einstein effects for an object approaching the speed of light. Interesting all other meep views were of this nice round antenna shape.

Just wondering how that compressed stress took that shape.

Shell

I don't recall Meep views of a round antenna shape.   
The antenna is much longer in one direction and has a "thickness" of only 2 Finite Difference nodes.
So, viewed from one side the antenna looks like a line, and when looked from the perpendicular view it looks like a point (or a very small circle of just 2 Finite Difference nodes).
When plotting the stress as the height of the "line antenna" the stress looks like a plate with rounded corners at the top.

Could you please link to the message, or even better copy and paste the round antenna image in your response ?

I need to see the 2 images you are referring to as a picture is worth a thousand words.

Thanks
You 're quite right the antenna is being shown in the horizontal plane not the vertical. I asked the question nicely and did say it was a danger alert. It is the exact way it should be and nothing is funny about it.

Edit: added the picture of the vertical antenna of the poynting vector you calculated associated the 2 and did a divide by 0.
« Last Edit: 07/13/2015 05:25 PM by SeeShells »

Offline rfcavity

  • Member
  • Posts: 37
  • Liked: 46
  • Likes Given: 0
I think we should not entertain gossip about Eagleworks testing until Star-Drive re-appears, as engaging in such discussion may jeopardize NASA Eagleworks's ongoing efforts, giving NASA's response to the "warp-drive" media articles.

Understandable. Thanks!

There is a short-fim made about this (if you speak German, turn-off the sound and just read the English subtitles) :)   :

http://captiongenerator.com/48295/Hitler-Reacts-to-current-EmDrive-Situation

Hah, I saw that linked a while back, but only ever browse on my phone, so I never clicked it >_< I'll have to watch it after work.

Also, thinking more on the collision of photons, one source said they may form a matter/antimatter pair. If this source is accurate, and collisions are occurring, is it possible the formation and annihilation redirects the forces of the photons in some odd manner?

I apologize if I'm derailing the discussion, feel free to stop me at any point :)
Photons do scatter off one another, but the energy densities required are beyond experimental reach currently. PVAS is the European facility that promises to get closest to seeing at least some nonlinearities in the near future using extremely high-power lasers. For ordinary experiments, you might as well assume they don't see each other at all.

And just to be sure, that includes considering the frustrum's shape being a wave-guide, correct? I'm not sure if that would make them more likely to connect, despite the small density.

Not at all. One of the great things to come from EM is superposition. For example, you have two point sources of EM separated by some distance. All you have to do is add together the (complex valued) fields contributed from each point source and you directly get the field everywhere. This means you can integrate over non-point volume/line sources very easily to get the field in free space. Its like the reason we can get analytical solutions for shaped cavities.

Online Rodal

  • Senior Member
  • *****
  • Posts: 5835
  • USA
  • Liked: 5913
  • Likes Given: 5253
...
Does anyone see any downside to those lower frequencies? Why does he go TM010 when it looks like TE012 on the experiments does better?
Resonant response should be higher at lower frequency modes: something true in all kinds of resonance oscillations, including electromagnetic resonance.
The issue here is the controversy surrounding the EM Drive, as to whether it is a real effect or an experimental artifact.  If it is a real effect, how can it get propulsion without violating conservation of momentum? Is it a free-energy machine?  Until we know how it works, we won't know precisely whether certain modes are better than others .  Yang has reported highest thrust and she has written that TE modes are to be preferred.  It looks like Shawyer has favored TE modes, particularly after discarding the dielectric inserts.  NASA Eagleworks preference for TM modes may be related to their preference to use dielectric inserts, as TM modes have an electric field in the  longitudinal direction of the EM Drive and it may favor the interaction of the electric axial field with the dielectric.

NASA reported the highest thrust/inputPower with TE012 with a dielectric but it looks like it was difficult to reproduce.  They reported no thrust with TE012 without a dielectric.

So, in a few words, their preference for TM010 instead of TE012 may be due to:

1) TM010 has lower frequency thant TE012, which should translate in higher amplitude
2) preference for TM modes in general because that's what they have been using the most in their testing (although for this particular example they were not intending to use a dielectric)
3) Dr. White's QV computer program may favor TM over TE modes even without a dielectric.
« Last Edit: 07/13/2015 05:13 PM by Rodal »

Offline marshallC

  • Member
  • Posts: 10
  • Liked: 2
  • Likes Given: 25
Give it up. EmDrive contains no black holes, cosmic strings, gravity anomalies, self-interacting photons, axions, WIMPs, MACHOs, pink unicorns or floobie-dust.

Although there might be some floobie-dust  8)

As a member of the pink unicorn religion, I am offended at such flagrant heresy.

Thanks for the explanations, deltamass and rfcavity.

Offline CraigPichach

  • Member
  • Posts: 59
  • Calgary Alberta
  • Liked: 42
  • Likes Given: 4
...
Does anyone see any downside to those lower frequencies? Why does he go TM010 when it looks like TE012 on the experiments does better?
Resonant response should be higher at lower frequency modes: something true in all kinds of resonance oscillations, including electromagnetic resonance.
The issue here is the controversy surrounding the EM Drive, as to whether it is a real effect or an experimental artifact.  If it is a real effect, how can it get propulsion without violating conservation of momentum? Is it a free-energy machine?  Until we know how it works, we won't know precisely whether certain modes are better than others .  Yang has reported highest thrust and she has written that TE modes are to be preferred.  It looks like Shawyer has favored TE modes, particularly after discarding the dielectric inserts.  NASA Eagleworks preference for TM modes may be related to their preference to use dielectric inserts, as TM modes have an electric field in the  longitudinal direction of the EM Drive and it may favor the interaction of the electric axial field with the dielectric.

NASA reported the highest thrust/inputPower with TE012 with a dielectric but it looks like it was difficult to reproduce.  They reported no thrust with TE012 without a dielectric.

So, in a few words, their preference for TM010 instead of TE012 may be due to:

1) TM010 has lower frequency thant TE012, which should translate in higher amplitude
2) preference for TM modes in general because that's what they have been using the most in their testing (although for this particular example they were not intending to use a dielectric)
3) Dr. White's QV computer program may favor TM over TE modes even without a dielectric.

Honestly I think that is why Paul's design makes the most sense for next step - fire an EM Thruster with enough juice that you produce some usable results, however inefficient or unoptimized - to at least determine if all of the theoretical arguments are worth spending time analyzing. My guess is that we need more experimental data anyway to validate a theory (especially if we are talking quantum vacuum), if any theory ends up being needed. If it is a real effect than let's see something real. Man discovered and used fire before understanding combustion. Let's get a thrust > 1 N - for $20K that is money well spent win or lose.

My understanding on the HDPE dielectric is that NASA thought it was only needed due to the low power input of their experiments and that at the kW range no additional dielectric is needed (apart from air) which is why Shawyer's EMDrive experiments work with no HDPE insert?

I think the liquid cooling is literally dump the Q-thruster in a pail of cold water and fire it for a second; at >1N thrust that's all you need to get a result.... that is if you actually can design the thruster for 957.833MHz at TM010.  My worry is that you build this thruster using a 915MHz unit at TM010 and it does nothing, where as if you could fire it at exactly 957.833MHz the thing would take off (which seemed to occur in the experiments). Wish I knew how to modify that CWM-100L across the L-band but it looks like they are just +/- 10MHz. Any solutions here?

Wish I knew the tolerance on that COMSOL screen shot, I would assume that is the 17"Od x 28" long unit at 957MHz. I bet he ran it at 929Hz too and that is "off set high" case....... tempted just to go ahead and try and see what happens. Have a local University willing to run tests on it.








Offline SeeShells

  • Senior Member
  • *****
  • Posts: 2326
  • Every action there's a reaction we try to grasp.
  • United States
  • Liked: 2956
  • Likes Given: 2588
...
You 're quite right the antenna is being shown in the horizontal plane not the vertical. I asked the question nicely and did say it was a danger alert. It is the exact way it should be and nothing is funny about it.
Sorry, I am a foreigner and don't understand what Danger Alert meant :).  I might have been clueless, was that a Lost in Space reference?
Yes, it is a Lost in Space reference. It means a visual type Engineer thinking about physics and postulating by what they see. 

Offline ElizabethGreene

  • Member
  • Posts: 69
  • Nashville, Tennessee
  • Liked: 138
  • Likes Given: 3
A question popped into my head today - can photons collide/interfere, and if so,...

I can't answer your latter questions, but I can answer this one.

Yes, photons can collide and interfere.  One of the really fascinating things about light is that it can, in photon-photon interactions, behave as if it has no mass, positive mass, or negative mass.  For all of these cases, F=mA still applies.  If you interact a photon in positive mass mode with a photon in negative mass mode then you can have two photons exit the collision moving in the same direction.  This is real, measurable, and breaks the symmetry of Newtons 3rd law [1].

(end of facts, beginning wild supposition here)

The above effect leads directly to my theory du jour for the operating principle of the emDrive.  The asymmetric resonator is creating a standing wave of photons producing identical radiation pressure on the front and rear endplates.  Some light is leaking into the space at the small end and is trapped bouncing back and forth between the standing waves (no radiation pressure) and the small end (radiation pressure).  This latter light is what moves the drive.  The reflectivity of the small end and the strength of the standing wave determine the "lifespan" of the trapped light and explain the correlation between Q and thrust.

I have a few ideas on proving this, but nothing substantial yet.

[1] Optical diametric drive acceleration through action–reaction symmetry breaking - Martin Wimmer, Alois Regensburger, Christoph Bersch, Mohammad-Ali Miri, Sascha Batz, Georgy Onishchukov, Demetrios N. Christodoulides & Ulf Peschel
http://www.nature.com/nphys/journal/v9/n12/full/nphys2777.html
(If your local library has ebscohost, it is available there in full text.)

Online Rodal

  • Senior Member
  • *****
  • Posts: 5835
  • USA
  • Liked: 5913
  • Likes Given: 5253
...
You 're quite right the antenna is being shown in the horizontal plane not the vertical. I asked the question nicely and did say it was a danger alert. It is the exact way it should be and nothing is funny about it.
Sorry, I am a foreigner and don't understand what Danger Alert meant :).  I might have been clueless, was that a Lost in Space reference?
Yes, it is a Lost in Space reference. It means a visual type Engineer thinking about physics and postulating by what they see.

Now I feel like Data in Star Trek Next Gen, being told a joke

« Last Edit: 07/13/2015 07:18 PM by Rodal »

Offline D_Dom

  • Global Moderator
  • Full Member
  • *****
  • Posts: 456
  • Liked: 154
  • Likes Given: 105
... my theory du jour for the operating principle of the emDrive.  The asymmetric resonator is creating a standing wave of photons producing identical radiation pressure on the front and rear endplates.  Some light is leaking into the space at the small end and is trapped bouncing back and forth between the standing waves (no radiation pressure) and the small end (radiation pressure).  This latter light is what moves the drive. 

Thanks for posting that. Every time I feel close to understanding this conversation I have learned to ask a clarifying question. Can you explain " light is leaking into the space at the small end"? I think you mean random ambient light through gaps in the construction.
 Similarly (to my meager grasp of the concept) "trapped bouncing back and forth between the standing waves" brought to mind particles interacting with the energy of RF peaks... "and the small end (radiation pressure)" which I read as the reflective surface of the end plate.
« Last Edit: 07/13/2015 06:18 PM by D_Dom »
Space is not merely a matter of life or death, it is considerably more important than that!

Offline DaCunha

  • Member
  • Posts: 35
  • Liked: 38
  • Likes Given: 14
...
Does anyone see any downside to those lower frequencies? Why does he go TM010 when it looks like TE012 on the experiments does better?
Resonant response should be higher at lower frequency modes: something true in all kinds of resonance oscillations, including electromagnetic resonance.
The issue here is the controversy surrounding the EM Drive, as to whether it is a real effect or an experimental artifact.  If it is a real effect, how can it get propulsion without violating conservation of momentum? Is it a free-energy machine?  Until we know how it works, we won't know precisely whether certain modes are better than others .  Yang has reported highest thrust and she has written that TE modes are to be preferred.  It looks like Shawyer has favored TE modes, particularly after discarding the dielectric inserts.  NASA Eagleworks preference for TM modes may be related to their preference to use dielectric inserts, as TM modes have an electric field in the  longitudinal direction of the EM Drive and it may favor the interaction of the electric axial field with the dielectric.

NASA reported the highest thrust/inputPower with TE012 with a dielectric but it looks like it was difficult to reproduce.  They reported no thrust with TE012 without a dielectric.

So, in a few words, their preference for TM010 instead of TE012 may be due to:

1) TM010 has lower frequency thant TE012, which should translate in higher amplitude
2) preference for TM modes in general because that's what they have been using the most in their testing (although for this particular example they were not intending to use a dielectric)
3) Dr. White's QV computer program may favor TM over TE modes even without a dielectric.

Honestly I think that is why Paul's design makes the most sense for next step - fire an EM Thruster with enough juice that you produce some usable results, however inefficient or unoptimized - to at least determine if all of the theoretical arguments are worth spending time analyzing. My guess is that we need more experimental data anyway to validate a theory (especially if we are talking quantum vacuum), if any theory ends up being needed. If it is a real effect than let's see something real. Man discovered and used fire before understanding combustion. Let's get a thrust > 1 N - for $20K that is money well spent win or lose.

My understanding on the HDPE dielectric is that NASA thought it was only needed due to the low power input of their experiments and that at the kW range no additional dielectric is needed (apart from air) which is why Shawyer's EMDrive experiments work with no HDPE insert?

I think the liquid cooling is literally dump the Q-thruster in a pail of cold water and fire it for a second; at >1N thrust that's all you need to get a result.... that is if you actually can design the thruster for 957.833MHz at TM010.  My worry is that you build this thruster using a 915MHz unit at TM010 and it does nothing, where as if you could fire it at exactly 957.833MHz the thing would take off (which seemed to occur in the experiments). Wish I knew how to modify that CWM-100L across the L-band but it looks like they are just +/- 10MHz. Any solutions here?

Wish I knew the tolerance on that COMSOL screen shot, I would assume that is the 17"Od x 28" long unit at 957MHz. I bet he ran it at 929Hz too and that is "off set high" case....... tempted just to go ahead and try and see what happens. Have a local University willing to run tests on it.

>The problem is EW does not have 20k $ to spend "win or lose". And, what makes it very painful if you ask me, we the people are not allowed to crowdfund their work.

Quote from Paul March: "As to crowd sourcing, as I and several others have tried to explain on the NASASpaceFlight.com EM-Drive forum in the past, NASA projects can't take outside funding from non-government entities except via a space act agreement through NASA Headquarters in Washington DC, so crowd sourcing is not possible. However thanks for the thought."

However, I see a small chance. Tomorrow New Horizons will pass Pluto at closest distance. And this event could remind everyone that this will be the last planetoid extraterrestrial unknown object that we will discover.

It will remind them, that without new propulsion technology this will be the end of human space exploration.

What if we start a white house petition to show the government the people's interest in investigating the EMDrive concept?

If all who visited this thread would sign it.. I think this would increase the chances for a space act drastically.
« Last Edit: 07/13/2015 06:44 PM by DaCunha »

Offline marshallC

  • Member
  • Posts: 10
  • Liked: 2
  • Likes Given: 25
A question popped into my head today - can photons collide/interfere, and if so,...

I can't answer your latter questions, but I can answer this one.

Yes, photons can collide and interfere.  One of the really fascinating things about light is that it can, in photon-photon interactions, behave as if it has no mass, positive mass, or negative mass.  For all of these cases, F=mA still applies.  If you interact a photon in positive mass mode with a photon in negative mass mode then you can have two photons exit the collision moving in the same direction.  This is real, measurable, and breaks the symmetry of Newtons 3rd law [1].

(end of facts, beginning wild supposition here)

The above effect leads directly to my theory du jour for the operating principle of the emDrive.  The asymmetric resonator is creating a standing wave of photons producing identical radiation pressure on the front and rear endplates.  Some light is leaking into the space at the small end and is trapped bouncing back and forth between the standing waves (no radiation pressure) and the small end (radiation pressure).  This latter light is what moves the drive.  The reflectivity of the small end and the strength of the standing wave determine the "lifespan" of the trapped light and explain the correlation between Q and thrust.

I have a few ideas on proving this, but nothing substantial yet.

[1] Optical diametric drive acceleration through action–reaction symmetry breaking - Martin Wimmer, Alois Regensburger, Christoph Bersch, Mohammad-Ali Miri, Sascha Batz, Georgy Onishchukov, Demetrios N. Christodoulides & Ulf Peschel
http://www.nature.com/nphys/journal/v9/n12/full/nphys2777.html
(If your local library has ebscohost, it is available there in full text.)

Would you know if this is a behavior that could be modeled and added to meep's computations? It's been a bit since I've had ebscohost access from a college, so I'll have to check my library. Thank you for bringing this information up :)
« Last Edit: 07/13/2015 06:50 PM by marshallC »

Offline CraigPichach

  • Member
  • Posts: 59
  • Calgary Alberta
  • Liked: 42
  • Likes Given: 4
Quote
Quote from Paul March: "As to crowd sourcing, as I and several others have tried to explain on the NASASpaceFlight.com EM-Drive forum in the past, NASA projects can't take outside funding from non-government entities except via a space act agreement through NASA Headquarters in Washington DC, so crowd sourcing is not possible. However thanks for the thought."

However, I see a small chance. Tomorrow New Horizons will pass Pluto at closest distance. And this event could remind everyone that this will be the last planetoid extraterrestrial unknown object that we will discover.

It will remind them, that without new propulsion technology this will be the end of human space exploration.

What if we start a white house petition to show the government the people's interest in investigating the EMDrive concept?

If all who visited this thread would sign it.. I think this would increase the chances for a space act drastically.

I think a better strategy is to use the clues (CWM-100L at 100kW at 957.833MHz, 17"OD x 28" long) and build it for him and publish the results here. That fulfills the NASA mandate of creating triggers within the market which he can in turn use to push his projects forward.

Offline rfmwguy

  • EmDrive Builder (retired)
  • Senior Member
  • *****
  • Posts: 2165
  • Liked: 2681
  • Likes Given: 1124
Give it up. EmDrive contains no black holes, cosmic strings, gravity anomalies, self-interacting photons, axions, WIMPs, MACHOs, pink unicorns or floobie-dust.

Although there might be some floobie-dust  8)
DM, if I had not nicknamed my project NSF-1701, "Floobie Dust" would have been a brilliant name ;^)

Offline aero

  • Senior Member
  • *****
  • Posts: 2739
  • 92129
  • Liked: 704
  • Likes Given: 236
I did not receive a reply from the FEFF project. But I have now configured an AMI image based on Ubuntu with meep installed. I have also uploaded aero's file to it. Also, for some strange reason (meep version differences?) I had to change all occurences of the type:
(define variable)
(set! variable some-value)
to
(define variable some-value)
in order to get  the simulation to start.

Also, I have wrapped the main run statement in a (synchronized-magnetic ...) statement, to avoid the situation described on the meep wiki:
Quote from: meep wiki
In the finite-difference time-domain method, the electric and magnetic fields are stored at different times (and different y O(Δt2), which is the best we can do in second-order FDTD.

... Snip ...

Meep also saves a copy of the magnetic fields at t − Δt / 2, so that it can restore those fields for subsequent timestepping.

Ok, so most of the configuration work is done. My questions are now:
1) How many cycles should we run?
2) Is user apoc2021's generous offer to donate server time still open?

I would like to see the changes you have made, particularly "Also, I have wrapped the main run statement in a (synchronized-magnetic ...) statement, to avoid the situation described on the meep wiki:"
If you would be so kind as to post the snippets showing the relevant code.
Retired, working interesting problems

Offline zen-in

  • Full Member
  • ****
  • Posts: 531
  • California
  • Liked: 468
  • Likes Given: 365


...

>The problem is EW does not have 20k $ to spend "win or lose". And, what makes it very painful if you ask me, we the people are not allowed to crowdfund their work.

...

However, I see a small chance. Tomorrow New Horizons will pass Pluto at closest distance. And this event could remind everyone that this will be the last planetoid extraterrestrial unknown object that we will discover.

It will remind them, that without new propulsion technology this will be the end of human space exploration.

What if we start a white house petition to show the government the people's interest in investigating the EMDrive concept?

If all who visited this thread would sign it.. I think this would increase the chances for a space act drastically.
Like you I am fascinated by the results from the NH spacecraft.   A dear friend of mine and former co-worker at NASA has been involved in this project for several years now.   I playfully chided her a few short years ago that it would take a long, long time to reach Pluto.   But now we are there.   There will be other discoveries, asteroids to visit, etc.    I don't think NASA needs to be convinced of the need for a means of high specific impulse propulsion.   There is a potential downside to your suggestion of a petition.   What if there is nothing to the em-drive but poor experimental practices?    NASA gets whip-sawed so much by Congress, pork-belly politics, and well-meaning academics already.    They are already supporting the Eagleworks Lab and nothing conclusive has come from that.   If your petition were successful and NASA sunk $100M into an accelerated research program that proved without a doubt the em-drive is not a form of propulsion that would set back other more promising research.    NASA critics would then point to the em-drive fiasco and say "No, we don't want to get burned again by bad science."
« Last Edit: 07/13/2015 07:32 PM by zen-in »

Offline CW

  • Full Member
  • *
  • Posts: 187
  • Germany
  • Liked: 141
  • Likes Given: 51

>The problem is EW does not have 20k $ to spend "win or lose". And, what makes it very painful if you ask me, we the people are not allowed to crowdfund their work.

Quote from Paul March: "As to crowd sourcing, as I and several others have tried to explain on the NASASpaceFlight.com EM-Drive forum in the past, NASA projects can't take outside funding from non-government entities except via a space act agreement through NASA Headquarters in Washington DC, so crowd sourcing is not possible. However thanks for the thought."

However, I see a small chance. Tomorrow New Horizons will pass Pluto at closest distance. And this event could remind everyone that this will be the last planetoid extraterrestrial unknown object that we will discover.

It will remind them, that without new propulsion technology this will be the end of human space exploration.

What if we start a white house petition to show the government the people's interest in investigating the EMDrive concept?

If all who visited this thread would sign it.. I think this would increase the chances for a space act drastically.

Just one comment about crowdfunding not being possible for NASA.. that restraint is, and please forgive my unfiltered rage, pure unadulterated horse shite. If tax payers money isn't crowdfunding on the largest possible scale already, I don't know what is. Maybe they don't like the thought that tax payers might do productive things without consent from 'authorities'. Hey mom! Can I have my EM drive allowance, please? No? Why!? But I was a good boy! Aww... . OK, mom. Yes, wars are important. Maybe next week?
*CoM violating facepalm deluxe*.
« Last Edit: 07/13/2015 08:06 PM by CW »
Reality is weirder than fiction

Online Rodal

  • Senior Member
  • *****
  • Posts: 5835
  • USA
  • Liked: 5913
  • Likes Given: 5253
I did not receive a reply from the FEFF project. But I have now configured an AMI image based on Ubuntu with meep installed. I have also uploaded aero's file to it. Also, for some strange reason (meep version differences?) I had to change all occurences of the type:
(define variable)
(set! variable some-value)
to
(define variable some-value)
in order to get  the simulation to start.

Also, I have wrapped the main run statement in a (synchronized-magnetic ...) statement, to avoid the situation described on the meep wiki:
Quote from: meep wiki
In the finite-difference time-domain method, the electric and magnetic fields are stored at different times (and different y O(Δt2), which is the best we can do in second-order FDTD.

... Snip ...

Meep also saves a copy of the magnetic fields at t − Δt / 2, so that it can restore those fields for subsequent timestepping.

Ok, so most of the configuration work is done. My questions are now:
1) How many cycles should we run?
2) Is user apoc2021's generous offer to donate server time still open?

I would like to see the changes you have made, particularly "Also, I have wrapped the main run statement in a (synchronized-magnetic ...) statement, to avoid the situation described on the meep wiki:"
If you would be so kind as to post the snippets showing the relevant code.
I understand that there are 6527 FD time steps for a total Meep time of 13.054, giving
FD time step = 0.002 Meep time
there are 32 periods in the total Meep time of 13.054
1 period = 13.054/32 Meep time
so
1 period = 13.054/(32*0.002) FD time steps
             = 203.9687 FD time steps
or

1 FD time step = 0.002*32/13.054 period
                       = 0.490% of a period

The "error" you are discussing is 1/2 of a finite difference time step, which means: 0.245% of a period.  This "error" does not affect the stability scheme  (that's why the standard Meep option is not to synchronize). It is small for the microwave frequencies we are discussing because microwave frequencies are much lower than optical frequencies,  it is something to take into account when dealing with very high frequencies which have much shorter periods, and when calculating Poynting vectors.

There is a price: synchronizing the fields takes time, and also increases the memory usage in order to backup the unsynchronized fields.

If you think that it is worthy to spend the resources to synchronize because of this 0.245% "error", you might consider as an alternative decreasing the time step, which decreases this "error" while simultaneously improving stability (which synchronization does not). 

This "error" 0.245% per period mainly affects the Poynting vector calculation because of ExH affects the time but it does not impact the stress calculation, because the stress calculation deals with the square of E and B, and for the stress calcualtion those terms get algebraically added instead of multiplied.

Then again, if synchronization does not take much computer resources, you might as well synchronize.
But it is important to compare apples to apples,  I suggest that @dumbo run

1) Identical (NO changes) file as run by aero to calculate the Poynting vector with no synchronization
2) Identical (NO changes) file as run by aero to calculate the Poynting vector with synchronization

To compare results with and without synchronization. 

If a) synchronization leads to significantly different results and b) it involves negligible increase in computer time, then do synchronization from then on.

If a) synchronization leads to significantly different results and b) it involves a significant increase in computer time, then you have to consider: c) do you need to calculate the Poynting vector, and if the answer is yes, then d) consider increasing the number of time steps without doing synchronization: which reduces synchronization error linearly but improves stability (which synchronization does not improve), and compare that with doing synchronization with the present FD time step.
« Last Edit: 07/13/2015 08:48 PM by Rodal »

Tags: