Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2103596 times)

Offline Flyby

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Quote from: Von Neumann
The sciences do not try to explain, they hardly even try to interpret, they mainly make models. By a model is meant a mathematical construct which, with the addition of certain verbal interpretations, describes observed phenomena. The justification of such a mathematical construct is solely and precisely that it is expected to work.
"Method in the Physical Sciences", in The Unity of Knowledge (1955), ed. L. G. Leary (Doubleday & Co., New York), p. 157

Funny... that's exactly the main idea I "learned" from reading Stephin Hawking's "Grand design" : the fact that we as humans are trying to come up with ever new models or concepts of how the world supposedly functions or looks like.  I'd pull it even larger and include religious concepts together with science models as being examples of our irresistible urge to explain things with models. I'd call them "mental constructs" and are inventions of our imagination.
 
Some those models correlated better with our observations then others, but who am I to say what's better then others? Today's concept(s) might be outdated or corrected in a few years...
Look at the concept of the "aether". When I was getting my science classes, the old greek concept by Aristotle was met with laughter... now 3 to 4 decades later, it kinda resurfaces as being a very valid concept to explain dark matter...go figure... :)

I realize that ancient philosophy has little to offer to the current science development, but science most definitely should have more impact on contemporary philosophy, on what impact current developments in science can have on our view of the "world" (or universe, in this case)

about the "free energy concept" : it is not because you, as 21th century human, do not see where the energy originates from that it should be "energy from nothing".
Transport yourself 100 years back and then explain to any people  in the street how you can gain 17kiloton TNT equivalent energy out of 1kg of uranium...where does that energy comes from? today we know, but back then we didn't...
All we know today is that after careful calculations scientists discovered that only 4.9% of the universe is matter like we know it...
Good question then is... what with all the rest? what's that? can or do we interact with it? does it hold energy?  Lots of questions needing lots of answers...
« Last Edit: 02/20/2015 05:16 PM by Flyby »

Offline frobnicat

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The key take away from the light in a box page was the red shift/blue shift. The same thing is presented by Shawyer. Also the theory paper presented (see Colbert) explains precisely how momentum is conserved. There is no free/cheap momentum.

Asserting there are conservation issues /while at the same time not understanding the interaction doesn't make sense. That's like passing legislation governing the use of time travel and warp drive before they become real. Just speculation.

You just have to read the paper.

What paper ? Colbert ? Where ?
Not trying to be obtuse here but you'll have to connect the dots for me (and for some other readers I guess)... still not understanding how this is supposed to make an energy generating scheme to fail (under the assumption that an emdrive could give 1N of thrust when fed 1kW microwave power for instance).

Some doppler shift is supposed to modifie the thrust/power ratio when emdrive is accelerated ? Does it pertain to accelerations vectors orthogonal to the axis of the frustum (as would be the case for a frustum mounted on a flywheel) ? Does it pertain to arbitrarily low accelerations (as the proposed device would work at, say, fixed tangential velocity V=2 km/s, acc=V˛/R so by extending the radius, radial acceleration can be made arbitrarily low) ? Does it pertain to an emdrive that is not accelerating, that is on straight trajectory, at constant velocity and thrusting at constant force that is pulling a tether that is rotating an electric generator ?

I'm not saying there is conservation issue, I'm concerned about consistency of a phenomenological model that's implied when mission profiles are proposed, this model is very simple : at a given microwave power there is a given thrust. Thrust=f(Power). Not Thrust=f(Power, Velocity wrt?, Acceleration, ...?) Granted, this model is speculative, but within this speculation it is not a speculation to state that the same effect used to accelerate a spacecraft can be used in a system that generates energy. It is not logical to operate under this assumption to devise mission profiles and not to devise unlimited energy generators.

From your previous remark :
I think this explains how Emdrive can never go over unity.

http://usersguidetotheuniverse.com/?p=2865

So you seem to think that "Emdrive can never go over unity", isn't it a bit speculative at this stage ? Regardless of why, that would imply that you consider that the Emdrive can't be used to accelerate a spacecraft at constant thrust/power ratio. What would be the proposed Thrust=f(Power, Velocity wrt?, Acceleration, ...?)

To be clear, I'm not trying to make a case that emdrive makes apparent energy conservation breaking and that therefore it must be bogus. If the effect is bogus or not is decided by experience, not by armchair physicists. But armchair physicist is legitimate to foretell that if effect is not bogus for space flight application (thrusting for deltaV) then it is not bogus for energy generation : the two situations can be made undistinguishable from the point of view of the device. This is a package. Take both or leave both.  Otherwise makes the claims appear not serious. Just saying.

For the later (energy generation) limitation on material makes the idea practical around 1N/kW above 1km/s speed (wrt local energy harvesting frame). So maybe the effect proves possible but not at such levels and that "prevents" the practical energy generation potential of the package. But even 50µN/50W is already enough to apparently break energy conservation, if not practically, at least in some physically possible setup.
« Last Edit: 02/20/2015 09:31 PM by frobnicat »

Online birchoff

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The key take away from the light in a box page was the red shift/blue shift. The same thing is presented by Shawyer. Also the theory paper presented (see Colbert) explains precisely how momentum is conserved. There is no free/cheap momentum.

Asserting there are conservation issues /while at the same time not understanding the interaction doesn't make sense. That's like passing legislation governing the use of time travel and warp drive before they become real. Just speculation.

You just have to read the paper.

What paper ? Colbert ? Where ?
Not trying to be obtuse here but you'll have to connect the dots for me (and for some other readers I guess)... still not understanding how this is supposed to make an energy generating scheme to fail (under the assumption that an emdrive could give 1N of thrust when fed 1kW microwave power for instance).

Some doppler shift is supposed to modifie the thrust/power ratio when emdrive is accelerated ? Does it pertain to accelerations vectors orthogonal to the axis of the frustum (as would be the case for a frustum mounted on a flywheel) ? Does it pertain to arbitrarily low accelerations (as the proposed device would work at, say, fixed tangential velocity V=2 km/s, acc=V˛/R so by extending the radius, radial acceleration can be made arbitrarily low) ? Does it pertain to an emdrive that is not accelerating, that is on straight trajectory, at constant velocity and thrusting at constant force that is pulling a tether that is rotating an electric generator ?

I'm not saying there is conservation issue, I'm concerned about consistency of a phenomenological model that's implied when mission profiles are proposed, this model is very simple : at a given microwave power there is a given thrust. Thrust=f(Power). Not Thrust=f(Power, Velocity wrt?, Acceleration, ...?) Granted, this model is speculative, but within this speculation it is not a speculation to state that the same effect used to accelerate a spacecraft can be used in a system that generates energy. It is not logical to operate under this assumption to devise mission profiles and not to devise unlimited energy generators.

From your previous remark :
I think this explains how Emdrive can never go over unity.

http://usersguidetotheuniverse.com/?p=2865

So you seem to think that "Emdrive can never go over unity", isn't it a bit speculative at this stage ? Regardless of why, that would imply that you consider that the Emdrive can't be used to accelerate a spacecraft at constant thrust/power ratio. What would be the proposed Thrust=f(Power, Velocity wrt?, Acceleration, ...?)

To be clear, I'm not trying to make a case that emdrive makes apparent energy conservation breaking and that therefore it must be bogus. If the effect is bogus or not is decided by experience, not by armchair physicists. But armchair physicist is legitimate to foretell that if effect is not bogus for space flight application (thrusting for deltaV) then it is not bogus for energy generation : the two situations can be made undistinguishable from the point of view of the device. This is a package. Take both or leave both.  Otherwise makes the claims appear not serious. Just saying.

For the later (energy generation) limitation on material makes the idea practical around 1N/kW above 1km/s speed (wrt local energy harvesting frame). So maybe the effect proves possible but not at such levels and that "prevents" the practical energy generation potential of the package. But even 50µN/50W is already enough to apparently break energy conservation, if not practically, at least in some physically possible setup.

What is the end goal of this line of reasoning?

Does the model presented with the mission profile, potentially lead to a situation where the EmDrive could be used as an over Unity power generator? Maybe. But lets for arguments sake agree that it does. What use is this information? I ask this question because if anything is clear from the discussions in this thread and the reported results to date. We only have a few rough guestimates at what is going on within the EmDrive. To prove or disprove the over unity power generation assertion you would need to completely characterize everything that is going on in the system. Right now the most we know is that when we pump EM into the cavity we get some thrust. We don't know beyond a reasonable doubt where the thrust is actually coming from. We don't know what we are actually interacting with. Now there are probably a whole lot of potential consequences of this research if it holds up to experimental scrutiny. But right now, the one thing I could probably guarantee, is that there will be a subset of those potential consequences that will not be possible once we have a better understanding of what is ACTUALLY happening.

On the flip side, should the researchers be allowed to propose mission profiles that could potentially not pan out due to a fundamental lack of understanding of what is actually going on? Maybe. Though from my perspective I think I am willing to give the primary investigators some leeway in painting a picture of what could be possible. As long as they assume the responsibility of dealing with the fall out if their vision is never realized.

Offline lele

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I think that frobnicat is simply saying that
IF there is a system (any system) that generate a given thrust when it's fed a given electrical power* (with no other parameters affecting the thrust) THEN it can be used to generate power, at least theoretically.

This implication doesn't necessitate knowledge of quantum physics, it's simply basic physics.

The interesting question is then "Is EMdrive a system that generate a given thrust when it's fed a given electrical power?"
If it is, we can generate power with EMdrive. It is an useful information: it means that, since free energy doesn't exist, we take this energy from somewhere.
If it isn't, knowing which parameters affect the thrust will probably give us some insight into how EMdrive generate thrust.

(as usual, if we assume that the thrust is not an artefact)

Edit: precision, see frobnicat's post below
* and the thrust/power ratio is better than that of a phton rocket (3.33 µN/kW)
« Last Edit: 02/21/2015 12:03 AM by lele »

Offline Flyby

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To get away from this overunity discussion , which is - in the current situation - a mere distraction with an apparently high polarized discussion risk... :)
 
the following idea popped up in my mind: what if instead of a truncated cone, other shapes are used?

What would be the implications of fe, using a paraboloid (or a hyperboloid) ?
http://mathworld.wolfram.com/Paraboloid.html
A paraboloid has a natural focal point, which probably would create an ever higher H-field intensity, as far as the resonance patterns go?


I also would like to understand to why the curved bottoms of Shawyer's new test rig "makes more sense" , from microwave resonance point of view?


As for the suggestion to analyze the available pictures of the shawyer and chinese EMdrives...
challenge accepted, i'll have a closer look at them. ? 8)

Finding pictures of shawyer's test device(s) is not that hard, but can any1 actually confirm that this is the Chinese truncated cone? or is it completely unrelated?

« Last Edit: 02/20/2015 11:44 PM by Flyby »

Offline Mulletron

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Last post converted to PM.
Here's all I have to say about this.

Quote
“The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations—then so much the worse for Maxwell's equations. If it is found to be contradicted by observation—well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics, I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” Sir Arthur Eddington (The Nature of the Physical World, 1915)
http://web.mit.edu/keenansymposium/overview/background/
« Last Edit: 02/21/2015 06:35 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline frobnicat

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What is the end goal of this line of reasoning?

This stems from the (maybe false) impression that enthusiasts consider that cheap momentum (thrusting for deltaV) is good while cheap energy is wrong (or that matter should be kept silent or mysterious). Such bias would introduces inconsistencies in the way to think about both theoretical aspects and engineering (space flight) prospects, and also degrade the perception from the general scientific public. If the impression of bias is false, and/or my ramblings aren't helping to reduce inconsistencies of thought or improving the sceptical public perception, then I apologize.

Quote
Does the model presented with the mission profile, potentially lead to a situation where the EmDrive could be used as an over Unity power generator? Maybe.

Certainly. How could it be otherwise ? Why let a doubt fly over that immediate consequence of the model ? The attempts to hide or confuse that fact in the published papers can only lower the academic credits of this line of research.

Quote
But lets for arguments sake agree that it does. What use is this information?

Consistency : momentum and energy conservation are to be taken together to build well behaved theories of operation that would help devise clear experiments for refutation/confirmation of said theories. So far, the few papers dealing with the "energy generation" addressed this aspect as a problem to avoid, not as a feature to incorporate. This yields inconsistent ideas and confusing writings, like thrust depending on velocity (with no clear way to tell relative to what), or like telling that classical action/reaction propulsion suffers "the same problem". The only clean simple consistent model is constant thrust at given power, regardless of velocity/trajectory/history of the device, and that simple predictive model predicts possibility of energy generation, but this is seemingly embarrassing people. Why ?

Quote
I ask this question because if anything is clear from the discussions in this thread and the reported results to date. We only have a few rough guestimates at what is going on within the EmDrive. To prove or disprove the over unity power generation assertion you would need to completely characterize everything that is going on in the system. Right now the most we know is that when we pump EM into the cavity we get some thrust. We don't know beyond a reasonable doubt where the thrust is actually coming from. We don't know what we are actually interacting with. Now there are probably a whole lot of potential consequences of this research if it holds up to experimental scrutiny. But right now, the one thing I could probably guarantee, is that there will be a subset of those potential consequences that will not be possible once we have a better understanding of what is ACTUALLY happening.

Well, there are a lot of unknowns. It is quite possible that space flight application is part of the "subset of those potential consequences that will not be possible".

Quote
On the flip side, should the researchers be allowed to propose mission profiles that could potentially not pan out due to a fundamental lack of understanding of what is actually going on? Maybe. Though from my perspective I think I am willing to give the primary investigators some leeway in painting a picture of what could be possible. As long as they assume the responsibility of dealing with the fall out if their vision is never realized.

At the moment the painting is framed in such a way as not to show the whole picture...
One of the clearer answer I got so far (from those questions) :

Last topic for the night for me.  Someone on this list asked if one could extract energy from the QV.  If the QV is GRT space-time, and space-time is the cosmological gravitational field that is created by all the causally connected mass/energy in our section of the universe, then we live in a high pressure sea of gravitational energy.  Now if the QV energy state is degradable and locally changeable, then one can posit the possibility of a thermodynamic energy conversion cycle that can extract energy from a pressure difference created in this QV media relative to the QV background average pressure, with a net decrease in this universal gravitational pressure or temperature reflective of the amount of energy so extracted.  And try to remember that gravitational energy is negative energy.  I'll leave the rest to you folks to draw your own conclusions from what this might mean...

Best, Paul March

As I understand this line of reasoning is high-risk/low-payoff I will stop there.

Offline Notsosureofit

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Entropically speaking, are there any other shapes for which we can write an analytic dispersion relation ?

And where did I leave my Gunn diode oscillator ?

Edit: and so far the work done/energy input is ~10-7, a long way from Newtonian unity.
« Last Edit: 02/20/2015 11:50 PM by Notsosureofit »

Offline Rodal

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Entropically speaking, are there any other shapes for which we can write an analytic dispersion relation ?

And where did I leave my Gunn diode oscillator ?

I understand you mean a closed form expression in terms of readily available computable functions...

cylindrical

parallelopipedal

and...


 the spherical cavity

EDIT: and the paraboloid cavity (the solution involves Kummer’s confluent hypergeometric function, so not a simple function...   http://arxiv.org/pdf/physics/0101011.pdf  )
« Last Edit: 02/21/2015 12:24 AM by Rodal »

Offline frobnicat

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I think that frobnicat is simply saying that
IF there is a system (any system) that generate a given thrust when it's fed a given electrical power (with no other parameters affecting the thrust) THEN it can be used to generate power, at least theoretically.

Basically, yes.
To be precise, any system that is not expelling mass, that is thrusting at better that tpr = 1/c = 3.33 µN/kW (photon rocket) can be used to generate power if it can be "hooked" to a generator at a relative speed above 1/tpr. For 50µN/50W = 1000 µN/kW that speed is 1000 km/s (hard to hook to anything). For a photon rocket 1/tpr=c : nothing can go > c so the energy generating scheme is intrinsically impossible for a photon rocket. An Emdrive with 1N/kW starts to be overunity above 1km/s. Spinning it at 2km/s tangential speed (engineering feat but not impossible) would leave ample margin for inefficiencies in the closed cycle and still have a small net margin>0.

Quote
This implication doesn't necessitate knowledge of quantum physics, it's simply basic physics.

Yes, and anybody with a background in mechanics will see that.

Quote
The interesting question is then "Is EMdrive a system that generate a given thrust when it's fed a given electrical power?"
If it is, we can generate power with EMdrive. It is an useful information: it means that, since free energy doesn't exist, we take this energy from somewhere.
If it isn't, knowing which parameters affect the thrust will probably give us some insight into how EMdrive generate thrust.

(as usual, if we assume that the thrust is not an artefact)

Right. Thank you !
« Last Edit: 02/21/2015 12:01 AM by frobnicat »

Offline flux_capacitor

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Finding pictures of shawyer's test device(s) is not that hard, but can any1 actually confirm that this is the Chinese truncated cone? or is it completely unrelated?



I think it's from Shawyer and improperly attributed to Juan Yang on some other web sites: http://emdrive.com/flightprogramme.html

Someone should ask Roger Shawyer directly about the Chinese version (especially the dimensions of the cavity). He knows a lot about it, since he went there to speak with Juan Yang and give her some advice.

Offline Rodal

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....
I also would like to understand to why the curved bottoms of Shawyer's new test rig "makes more sense" , from microwave resonance point of view?

....
Because the type of electromagnetic waves that satisfy the boundary conditions at the lateral curved surfaces of a cone are spherical waves.  The great Russian/American scientist/engineer Schelkunoff showed this in the 1930's (http://forum.nasaspaceflight.com/index.php?topic=36313.msg1332981#msg1332981).  The natural Boundary Conditions for the bases of the cone are thus spherical surfaces.

The Finite Element and the Finite Difference calculations of NASA's EM Drive confirm that the electromagnetic fields are spherical standing waves away from the flat ends.

For a given spherical radius, the bigger the cone's angle, the more different is the spherical surface from a flat end, and the more important is to have spherical ends.  Kudos to Shawyer for being the first EM Drive researcher to realize this.



« Last Edit: 02/21/2015 02:25 AM by Rodal »

Offline Rodal

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..

What would be the implications of fe, using a paraboloid (or a hyperboloid) ?
http://mathworld.wolfram.com/Paraboloid.html
A paraboloid has a natural focal point, which probably would create an ever higher H-field intensity, as far as the resonance patterns go?


...
Because of Maxwell's equations, and the paraboloid boundary conditions, the paraboloid cavity actually has the central axis as a forbidden zone for electromagnetic waves,  see these mode shapes:

authors: Jens U. Nockel, Isabelle Robert, Jean-Marie Moison, and Izo Abram
« Last Edit: 02/21/2015 12:38 AM by Rodal »

Offline Rodal

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Finding pictures of shawyer's test device(s) is not that hard, but can any1 actually confirm that this is the Chinese truncated cone? or is it completely unrelated?

...


I think it's from Shawyer and improperly attributed to Juan Yang on some other web sites: http://emdrive.com/flightprogramme.html

Someone should ask Roger Shawyer directly about the Chinese version (especially the dimensions of the cavity). He knows a lot about it, since he went there to speak with Juan Yang and give her some advice.


Yes, that Shawyer's Flight Thruster development programme. A 3.85GHz thruster weighing 2.92 Kg,.



http://emdrive.com/flightprogramme.html

I don't recall estimated dimensions for it. If anybody estimated the dimensions, @aero is the most likely one to have done it.
« Last Edit: 02/21/2015 01:12 AM by Rodal »

Online aero

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Finding pictures of shawyer's test device(s) is not that hard, but can any1 actually confirm that this is the Chinese truncated cone? or is it completely unrelated?

...


I think it's from Shawyer and improperly attributed to Juan Yang on some other web sites: http://emdrive.com/flightprogramme.html

Someone should ask Roger Shawyer directly about the Chinese version (especially the dimensions of the cavity). He knows a lot about it, since he went there to speak with Juan Yang and give her some advice.


Yes, that Shawyer's Flight Thruster development programme. A 3.85GHz thruster weighing 2.92 Kg,.



http://emdrive.com/flightprogramme.html

I don't recall estimated dimensions for it. If anybody estimated the dimensions, @aero is the most likely one to have done it.

I did not. I see nothing to use as a reference. Perhaps someone could estimate ratios. Big/small, big/height or whatever.
Retired, working interesting problems

The photo is a bit blurry and that makes estimating a bit challenging, and there are lens distortions to the photo, but nothing too major.  If the concrete block happened to be the standard width of 440 mm, cited by wikipedia, then the dimensions would be roughly as estimated in the chart.

I'm an artist, not a physicist.  If these dimensions seem wrong and you have a different guess for the width of the concrete block, let me know and I'll recalculate based on your width standard.
« Last Edit: 02/21/2015 02:21 AM by lasoi »

Offline Rodal

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The photo is a bit blurry and that makes estimating a bit challenging, and there are lens distortions to the photo, but nothing too major.  If the concrete block happened to be a common standard size, which of course is no given, then the dimensions would roughly be:

Excellent !  Thank you lasoi !!!

« Last Edit: 02/21/2015 02:23 AM by Rodal »

Happy to help.  I love reading your posts.  Keep up the great work!

Offline ThinkerX

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Oh well, time for me to demonstrate my ignorance again, this time with a suggestion:

All through these calculations, the thrust is given as 'thrust per photon.' 

Photons seem to be durable little critters, capable of a lot of bounces (50,000+?) before becoming absorbed. 

Bouncing photons are a feature of the laser driven drives proposed by a Doctor David Bae (?) have to look this up, who reported a 3000 fold increase in thrust in a laboratory setting from this mechanism.

Unlike the EM drive, his work is based on known technology and principles.

Given this, might not a 'bouncing photon scale' be of some use in measuring the performance of the EM drive?

Run the thrust per photon calculation, assuming each 'bounce' adds a (decreasing) unit of thrust.  The upper theoretical limit should be well above what Bae reported. 

If the EM Drive stays within this scale in a vacuum, then maybe photon bouncing has something to do with its operation.

Ok, I better call it quits while I'm behind. 

Offline Mulletron

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http://eec.wustl.edu/aboutthedepartment/Pages/news-story.aspx?news=7577&source=admin

http://adsabs.harvard.edu/abs/2014NatPh..10..394P

http://ieeexplore.ieee.org/iel7/4563994/4814557/06690216.pdf

Man we need way stronger magnetic fields and better materials in that thing. The more I keep reading about this subject of PT symmetry breaking the clearer it becomes that this is routine.
« Last Edit: 02/21/2015 08:17 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

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