Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2098755 times)

Offline dustinthewind

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Not according to Maxwell's linear, isotropic equations.

The small base of the EM Drive is not open.  It is a closed cavity.  As such, the waves inside it are not travelling waves, but standing waves.   See this:  http://en.wikipedia.org/wiki/Standing_wave

The energy flux is pointed towards one end during half a (Poynting vector) period and it is pointed towards the opposite end during the next half-period.  Hence the net energy flux over a whole period is completely self-cancelling.

No net directional thrust for a microwave closed cavity can be explained just using Maxwell's linear, isotropic equations.  If the measurements are not an experimental artifact, another explanation is needed.

If the small base would be open, then it would be an inefficient photon rocket, with the microwave photons escaping at the small base end.  Less efficient for space propulsion than using a flashlight or a military searchlight as a means of propulsion.

Even for a perfectly collimated photon rocket, the thrust/powerInput of such a photon rocket is orders of magnitude less than what is claimed for these experiments.

With all respect, and I am not sure this is much of an issue to point out but I think the model of the waves in the cavity as standing waves may be a bit over-simplified. 

1. I think one can look at standing waves as super-imposed traveling waves of opposite direction but this part is likely less significant. 

2.  Maybe of more significance is the ac power in power lines can be modeled as standing waves but if no one is using power.  When power starts being consumed the standing waves begin to travel towards the object consuming the power.  The moving bulges of magnetic/electric field can be thought of as transporting power from the power station to the consumer.  There should be some traveling of the standing waves bulges from the power supply towards areas of heat loss in the cavity I would assume.  I can't say the power dissipated into heat loss is significant but it does seem to buck the perfect standing wave view for me a bit.  I do understand on the other hand that it may be a good approximation.

In ref to the image above, there is wealth of information buried within the earlier pages of this thread. A more accurate representation of what it looks like inside the cavity is available here:
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1333246#msg1333246
Paul March was kind enough to attach the Frustrum modes overview 2A.pdf which has all the mode shapes and characteristics of their test article.

So things are a bit more complicated than photons bouncing around like marbles in a can. For example, I know that I can only excite TM212 and TM311 (thanks @Rodal for modeling this) with my little setup at home.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1353372#msg1353372
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1352878#msg1352878

Paul March has shown clearly in his many posts that there is a clear correlation between mode shape and magnitude and direction of thrust. This is where input from RF Engineers would be extremely valuable.

Just food for thought, it is worth going back to page 1 and commenting on the stuff starting there. That way the conversation can keep building on ideas.





In response to the bold and underlined statements above I was just pointing out that I think we may be losing information by the idea of the standing wave model with out considering the power losses (due heating of the cavity and any propulsion) and the transport of energy by [E^2+B^2] http://hyperphysics.phy-astr.gsu.edu/hbase/electric/engfie.html where the stading wave bulges tend to move towards the areas of consumed energy (heating + sparks + propulsion +ect).  I was paralleling it to energy consumption in power lines.  There might be some hidden phase relation in here lurking that could suggest em-phase propulsion but that's just speculation. 

I agree in the line of  thinking of what is going on in the cavity as more of a wave model than thinking of them as marbles bouncing inside the cavity.  I admit there might be some parallel to the marbles but I don't see it. 

It is interesting to think that as the wave peaks travel towards the small end of the cavity they are being squeezed but if the wave peaks are traveling towards the larger end they are experiencing expansion.  It looks like as a result we see the increased B field near the tight end of the cavity and small B field near the big end.  I almost want to think of this squeezing as a form of propulsion in the form of resistance of the traveling of the semi-standing waves as they transport energy to areas of heat loss. 
« Last Edit: 05/02/2015 09:07 PM by dustinthewind »

Offline Rodal

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...

In response to the bold and underlined statements above I was just pointing out that I think we may be losing information by the idea of the standing wave model with out considering the power losses (due heating of the cavity and any propulsion) and the transport of energy by [E^2+B^2] http://hyperphysics.phy-astr.gsu.edu/hbase/electric/engfie.html where the stading wave bulges tend to move towards the areas of consumed energy (heating + sparks + propulsion +ect).  I was paralleling it to energy consumption in power lines.  There might be some hidden phase relation in here lurking that could suggest em-phase propulsion but that's just speculation. 

I agree in the line of  thinking of what is going on in the cavity as more of a wave model than thinking of them as marbles bouncing inside the cavity.  I admit there might be some parallel to the marbles but I don't see it. 

It is interesting to think that as the wave peaks travel towards the small end of the cavity they are being squeezed but if the wave peaks are traveling towards the larger end they are experiencing expansion.  It looks like as a result we see the increased B field near the tight end of the cavity and small B field near the big end.  I almost want to think of this squeezing as a form of propulsion in the form of resistance of the traveling of the semi-standing waves as they transport energy to areas of heat loss.

Can you please answer, according to your conjecture,when the thrust force is  measured towards the small end of the truncated cone:

1) Are there any particles being emitted, according to your conjecture, out of the cavity in the axial direction towards the big base ?

[If nothing is being emitted, then there cannot be any propulsion, because it would violate conservation of momentum.  If nothing is being emitted, please skip the next question]

2) what  particle is being emitted, out of the cavity, in the axial direction towards the big base ?

[for example, if you conjecture that photons are being emitted, even if that conjecture would be true, it would be contradicted by what is claimed, because what is claimed is a thrust thousands of times better than the thrust of a perfectly collimated photon rocket]

So, if you are attempting to explain the claimed thrust just based on Maxwell's equations, I still don't understand your conjecture. If I misunderstood something, please correct me.  Thanks.
« Last Edit: 05/02/2015 10:05 PM by Rodal »

Offline Notsosureofit

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Just want to run this by the group.

I am a believer that thrust doesn't scale ONLY with Q. We even can see that in the data. See the original Nasa paper.
http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf

I think I have a good idea for once. I think the "Where is the balanced gain and loss?" thing from the other day is addressed by creating an unstable cavity, aka not high Q, not low Q either.

The balanced gain and loss stuff came up here. 4th-6th links from top.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1357829#msg1357829

I think the trick is to get energy in, put it to work a few thousand times (doing all that quantum wizardry I posted papers on :) ), then let it go as heat, which will inevitably happen as photons are red shifted and fall out of resonance. High Q is a baddie. Low Q is a baddie.

What's the point of having all that accumulated energy sitting in there static, doing nothing?

We need this thing to ride the razor's edge between gain and loss.

Also, what made this kinda click with me is what Mr. Shawyer said below. The Cullen paper he mentioned is shared here:
https://drive.google.com/folderview?id=0B4PCfHCM1KYoTXhSUTd5ZDN2WnM&usp=sharing

So if this passes the smell test, how is the next question. Seems like not having the dielectric covering the entire small end (vs just a small patch) might be a good thing to try. I'm sure there's a ton of ways to do this.

There's a lot we can learn from that whispering-gallery research cited.
http://revolution-green.com/optics-breakthrough-demonstrates-new-behaviors-physics/
http://www.researchgate.net/publication/262451086_Paritytime-symmetric_whispering-gallery_microcavities
http://arxiv.org/ftp/arxiv/papers/1308/1308.4564.pdf

I'm openly brainstorming here. Would like some feedback.

Shawyer's explanation does not pass the smell test, and is not adressed by the Cullen paper you linked. Look for example at figure 5. There is a movable piston at the end of the waveguide T-junction, which is subject to radiation pressure. The piston will exert a (Newton's 3rd law) reaction force, and so momentum is conserved.

The EM drive is a fully enclosed cavity. The radiation inside will reflect off the walls and create some strain in the copper, but the net force integrated by the surface (given by the integral of the Poynting vector) has a time average of 0, as has been demonstrated mathematically many many times.

It is absolutely true that one can view standing waves as linear superpositions of traveling waves. This is just a different way of saying that Maxwell's equations are linear. Rodal's analysis is true whether one thinks of the fields as standing or superpositions of traveling waves. There is nothing besides the stress-energy tensor in the classical theory of electromagnetism.

To be clear: there is NO explanation for any increase in momentum of the drive to be found in classical theory (including Special Relativity through Maxwell's equations).

If there is an actual effect, then it must be caused by the coupling of electromagnetic fields to some other heretofore unobserved field. Even if such a coupling could be made in a way that is Lorentz invariant, it should have been detectable very easily at particle colliders. So again I ask:

If there is some effect here, why has it not been observed in far more precise experiments that probe the exact same physics?

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

Edit:  The self acceleration of photons, on the other hand, is old news.
         http://www.nature.com/ncomms/2014/141030/ncomms6189/abs/ncomms6189.html

« Last Edit: 05/02/2015 11:07 PM by Notsosureofit »

Offline PaulF

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Hello again all,

The layman in physics would like to offer an analogy to ponder, nullify or use as an example..If it can assist you in getting a bit closer to the solution, I am thrilled I could help. If not, I am thrilled I got the opportunity to propose my idea to people who really know what they are talking about :D

Q: Would it be useful to suggest to also consider comparing the process in the cavity to standing sound waves? They can exist as the result of reflected self-interference but I know that contructive bulges can pack a hell of a punch. And especially what triggered this thought: the notion that the waves may be squeezed and stretched in the small and wide end of the cavity. I know matter waves are different from EM waves as they have duality, but still.

Another thought I had about CoE. It's probably already been explained in this context before but I probably didn't understand it :P I assume when you talk about CoE, that as much power is pumped into the device, as is released from the device in the various forms of energy and matter? Closed as it is, power is flowing THROUGH the device, which means the above must be measured to be certain as much power comes out as goes in. If there is a measurable difference and all errors have been nulled (and assuming the energy content in the cavity remains constant on average), would that indicate energy is being injected into the QV? If you have the time and patience, can someone clarify or correct me on this? Thank you so much.

P.S. I just had another bit of imagination: Remember the Cake Walk at the fair? Two vertical sets of steps that move up and down in a sine type movement, and moving 180 degrees out of phase of each other. Now in the beginning you try to get up but if you step on the steps at the wrong moment of the phase, you end up stepping on the same steps over and over. But if you change your cyclic movement and do it 180 degrees out of phase, you can ride the steps up and you would use hardly any energy yourself (the electromotors would draw a bit more current to provide the kinetic energy to lift me up every step).

With far-fetched (how appropriate!) deducing you could conclude that it is possible to ride wave bulges with the correct frequency , amplitude, and phase shift... Could this idea be adapted to suit EM waves? Is this any food for thought for anyone of you brilliant guys? ;)

With regards,

Paul F
« Last Edit: 05/02/2015 11:13 PM by PaulF »

Offline Nathan

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My take:
There is a potential gradient formed within the cavity causing one end of the device to fall toward the other. The energy density at each end would differ due to the geometry leaving one side with a slightly higher mass-energy density than the other, creating the gradient.
Nathan Rogers
« Last Edit: 05/02/2015 10:34 PM by Nathan »
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Offline inquisitive-j

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If light is passing through the EM drive faster than the speed of light as people are suggesting from warp field inferometer test results, wouldn't that imply that that area had a refractive index less than 1? And if that's the case, isn't that something that can be easily tested?

Offline frobnicat

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Hey everyone!


My name is Kurt Zeller, my colleague Bran Kraft and I are undergraduate Aerospace Engineering students at California Polytechnic State University, San Luis Obispo. (authors of this review: http://www.slideshare.net/KurtZeller/investigation-and-analysis-of-anomalous-electromagnetic-propulsion-devices-41315-46946953 )

We are currently designing an experiment to test a resonant cavity. We have made considerable progress on our own and would like to share our methodology with the forum to gain insight and suggestions before we start purchasing materials. Our primary objective is to demonstrate thrust using a counterbalanced lever. Our secondary objective is to quantify the thrust and make changes to the geometry of the dielectric.

We have recently received funding for a copper cavity, PTFE plate, and aluminum beam. This aluminum beam will have a sharp fulcrum welded to the bottom and the ends will be recessed lower than the fulcrum to put the center of mass closer to the balance point. We anticipate the thrust will be larger than the fulcrum's friction but this is still a concern in our experiment. An additional concern is the tension force from the cables that supply power. We plan to fix these cables above the fulcrum with enough slack to negate this issue. We acknowledge the difficulties in accurately obtaining thrust measurements but are mainly attempting to demonstrate thrust before quantifying it. 

The cavity will be made of C10100 Copper alloy tube with two C11000 copper end plates. A symmetric shape was chosen to minimize complications and cost as well as provide a different cavity geometry for comparison. A PTFE plate will machined into discs of varying thickness that fit adequately at the end of the cylinder. We have access to a VNA from our EE department and will use it to determine the resonant frequencies.

We are still awaiting approval for our latest proposal to the Cal Poly committee where we requested $3,500 to rent a 2-3 GHz signal generator, a 50W amplifier, and a spectrum analyzer. We are also planning to implement a matched load to absorb reflected power but are still working with professors to design it.   

Because these devices are incredibly expensive, we have been researching how to engineer a microwave oven magnetron into the power source. Unfortunately, the relatively constant frequency will limit the number of resonant modes that can be excited unless our cavity length is adjustable. Furthermore, thermal expansion may be a much greater issue at higher power and resonance may be more difficult to maintain.

In the event that we are approved funding for the rental equipment we will most likely attempt both setups.
We are happy to address questions or concerns and we look forward to any suggestions you may have. We understand Eagleworks is planning a similar experiment and we are hoping to gain more insight into their power delivery system.

We would like to thank all the contributors to this forum who have been a great help and inspiration for us throughout this project.

Hello and welcome.

Maybe a (simplified) schematic of your projected set up would help people here (including those less fluent in English) visualize your future experiment and have suggestions. By "sharp fulcrum" do you mean a conical piece with "point contact" on support that allows for rotation around vertical axis, or a prismatic edge with linear contact on support, that rotates horizontally like in a teeter totter balance ? What roughly would be the dimensions and weight of the moving assembly, what choice of material for fulcrum and support where it rests ? Risk with dry contacts at N levels is stiction... why not go hanging Cavendish torsion pendulum ? There seems to be a rare consensus that it would be best.

edit : also be aware that you are pumping some heat in a contained volume, either make you cavity completely hermetic or leave a large opening (1cm or so, with a conductive mesh to keep waves from leaking) between inside and outside. Either will prevent a potential pressure build up to "jet", but the worse would be an uncontrolled thin slit letting the heated air leak outside but not enough to equalize pressure "instantly". And while I'm at it, beware of thermal dilation centre of mass shifts (depending on the type of balance...).

For powering the system, why not go with batteries to avoid problem with cables from fixed part to moving assembly ? Lithium batteries at ~100Wh/kg are readily available at modest costs. A pack sized for 50W output for half an hour would add significant but not enormous weight to the moving assembly and would avoid a whole lot of potential spurious signals, and make your experiment better than Eagleworks' one (so far) on that aspect. A lot of people have suggested a fully self enclosed system (thermally, electrically, and magnetically if possible) on the balance as a required condition for better credibility.

One of the very few (only ?) reported null result (down to sensitivity) with experiment on propellantless device (not em drive type...) was obtained with a fully self contained test article :
Null Findings on Electromagnetic Inertia Thruster
Experiments using a Torsion Pendulum by Brito, Marini, Galian 2009


Knowing how to create and see an EM thrust signature, if there is such a thing, is nice. Designing and conducting the experiment to see no thrust signature if there is none is more scientifically valuable IMHO. And at this stage there appear to be more risks in false positives than in false negatives.
« Last Edit: 05/02/2015 11:00 PM by frobnicat »

Offline Dmytry

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One of the very few (only ?) reported null result (down to sensitivity) with experiment on propellantless device (not em drive type...) was obtained with a fully self contained test article :
Null Findings on Electromagnetic Inertia Thruster
Experiments using a Torsion Pendulum by Brito, Marini, Galian 2009


Knowing how to create and see an EM thrust signature, if there is such a thing, is nice. Designing and conducting the experiment to see no thrust signature if there is none is more scientifically valuable IMHO. And at this stage there appear to be more risks in false positives than in false negatives.
Now that was a great experimental setup. Appropriate $ spending for how credible the claims were, yet potentially very sensitive, repeatable, and accurate.

Regarding enclosing it, the first test is to at least just enclose it pneumatically, i.e. so it wouldn't be blowing ions. Albeit enclosing it electrically may be necessary to avoid it messing up the pendulum. Another good thing about the hanging pendulum that is not too stiff, is that heating of the wire it's hanging from is not likely to result in a huge zero shift.

(The fact of just how cheap a good set up can be is also why any requests for extra funding only bring to mind an image of a certain generally very disrespected Italian scientist who had been doing otherwise straightforward calorimetry using a very expensive thermal imaging camera.)

And it's more in line with the topic of the thread as well, because to use it in space you need it to be self contained. Also it helps a little if you have more money left for space stuff.
« Last Edit: 05/02/2015 11:05 PM by Dmytry »

Online Robotbeat

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But if there's no thrust when the drive is enclosed and if the thrust is diminished, though still present, in a vacuum (when there is no air to push against), doesn't that suggest that the cavity is spewing particles somehow?
Right, put kilowatts of power into something, it will heat up and start outgassing something fierce. But also do a lot of other things.

2.5kW is a LOT of power. If it's all essentially absorbed by the cone, then it gets converted into heat. 2.5kW is like the power output of an oven or like 40 incandescent light bulbs. Especially in a vacuum, you're going to heat up your device to hundreds of degrees. If this gets transferred to the thrust-measuring arm at all (which it likely would), you're going to change the resistance of your strain gauge, thus giving you a false thrust reading.


Remember that strain gauges are just copper wire, and so acts just as well as a kind of thermometer. A temperature change (unless super, super carefully canceled out--almost impossible to do if there's a large temperature gradient on the gauge itself) will show up as a change in resistance, just like force will.
« Last Edit: 05/02/2015 11:51 PM by Robotbeat »
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Offline Rodal

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Just want to run this by the group.

I am a believer that thrust doesn't scale ONLY with Q. We even can see that in the data. See the original Nasa paper.
http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf

I think I have a good idea for once. I think the "Where is the balanced gain and loss?" thing from the other day is addressed by creating an unstable cavity, aka not high Q, not low Q either.

The balanced gain and loss stuff came up here. 4th-6th links from top.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1357829#msg1357829

I think the trick is to get energy in, put it to work a few thousand times (doing all that quantum wizardry I posted papers on :) ), then let it go as heat, which will inevitably happen as photons are red shifted and fall out of resonance. High Q is a baddie. Low Q is a baddie.

What's the point of having all that accumulated energy sitting in there static, doing nothing?

We need this thing to ride the razor's edge between gain and loss.

Also, what made this kinda click with me is what Mr. Shawyer said below. The Cullen paper he mentioned is shared here:
https://drive.google.com/folderview?id=0B4PCfHCM1KYoTXhSUTd5ZDN2WnM&usp=sharing

So if this passes the smell test, how is the next question. Seems like not having the dielectric covering the entire small end (vs just a small patch) might be a good thing to try. I'm sure there's a ton of ways to do this.

There's a lot we can learn from that whispering-gallery research cited.
http://revolution-green.com/optics-breakthrough-demonstrates-new-behaviors-physics/
http://www.researchgate.net/publication/262451086_Paritytime-symmetric_whispering-gallery_microcavities
http://arxiv.org/ftp/arxiv/papers/1308/1308.4564.pdf

I'm openly brainstorming here. Would like some feedback.

Shawyer's explanation does not pass the smell test, and is not adressed by the Cullen paper you linked. Look for example at figure 5. There is a movable piston at the end of the waveguide T-junction, which is subject to radiation pressure. The piston will exert a (Newton's 3rd law) reaction force, and so momentum is conserved.

The EM drive is a fully enclosed cavity. The radiation inside will reflect off the walls and create some strain in the copper, but the net force integrated by the surface (given by the integral of the Poynting vector) has a time average of 0, as has been demonstrated mathematically many many times.

It is absolutely true that one can view standing waves as linear superpositions of traveling waves. This is just a different way of saying that Maxwell's equations are linear. Rodal's analysis is true whether one thinks of the fields as standing or superpositions of traveling waves. There is nothing besides the stress-energy tensor in the classical theory of electromagnetism.

To be clear: there is NO explanation for any increase in momentum of the drive to be found in classical theory (including Special Relativity through Maxwell's equations).

If there is an actual effect, then it must be caused by the coupling of electromagnetic fields to some other heretofore unobserved field. Even if such a coupling could be made in a way that is Lorentz invariant, it should have been detectable very easily at particle colliders. So again I ask:

If there is some effect here, why has it not been observed in far more precise experiments that probe the exact same physics?

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

Edit:  The self acceleration of photons, on the other hand, is old news.
         http://www.nature.com/ncomms/2014/141030/ncomms6189/abs/ncomms6189.html

(Kudos to old-timers  8) ), this has been predicted since at least 36 years ago, going back to 1979, when Berry and Balazs proposed that the Schrodinger equation describing a free particle can exhibit a nonspreading Airy wave packet solution with the ability to freely accelerate even in the absence of any external potential (in other words, with no force acting).  What is relatively new (last 10 years) are the experiments, confirming their theoretical prediction.

See page 266 of this: 

https://michaelberryphysics.files.wordpress.com/2013/07/berry078.pdf
M.V. Berry, N.L. Balazs, Am. J. Phys. 47, 264 (1979)



PS: Balazs was at State University in Stony Brook at the time (kudos to MIT's James Simons, who I think was chairman of the math department at Stony Brook University at the time (am I correct ?)

Nandor Balzs was assistant to Schroedinger at the Dublin Institute for Advanced Studies, and a one year assistant to Einstein at the Institute for Advanced Study in Princeton.  He also had close working collaboration with  Paul Dirac , Chandrasekhar, and Eugene Wigner.
« Last Edit: 05/03/2015 03:10 AM by Rodal »

Offline Dmytry

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Speaking of the power levels, there was 55 uN in air from 2.6 watts, TE012. Now that's something that's easy and safe to build with a couple high frequency transistors and assorted passives. Can obtain feedback with another antenna in the cavity so that it is always resonating. Albeit you'd need a quite expensive oscilloscope.

Offline Rodal

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But if there's no thrust when the drive is enclosed and if the thrust is diminished, though still present, in a vacuum (when there is no air to push against), doesn't that suggest that the cavity is spewing particles somehow?
Right, put kilowatts of power into something, it will heat up and start outgassing something fierce. But also do a lot of other things.

2.5kW is a LOT of power. If it's all essentially absorbed by the cone, then it gets converted into heat. 2.5kW is like the power output of an oven or like 40 incandescent light bulbs. Especially in a vacuum, you're going to heat up your device to hundreds of degrees. If this gets transferred to the thrust-measuring arm at all (which it likely would), you're going to change the resistance of your strain gauge, thus giving you a false thrust reading.


Remember that strain gauges are just copper wire, and so acts just as well as a kind of thermometer. A temperature change (unless super, super carefully canceled out--almost impossible to do if there's a large temperature gradient on the gauge itself) will show up as a change in resistance, just like force will.

NASA Eagleworks reported a thrust force measurement with only 2.6 watts input in ambient air conditions (that's almost 1,000 times less power than quoted above):

lengths in meter
rfFrequency in 1/second (microwave frequency during test)
power in watts
force in milliNewtons
force per PowerInput in milliNewtons/kW

rfFrequency = 1.8804*10^9;
power = 2.6
Q = 22000
measured force = 0.05541
measured ForcePerPowerInput = 21.31
Force/PowerInput of a Photon Rocket =0.003337
measured ForcePerPowerInput to the one of a photon rocket =6,386.7
« Last Edit: 05/03/2015 12:47 AM by Rodal »

Offline Dmytry

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Keep in mind also that such results make me think the rig is not working right. Power levels vary widely, so does the Q-factor (and thus the actual EM field inside the cavity), thrust on the other hand somehow always stays within the range of drifts.
« Last Edit: 05/03/2015 12:47 AM by Dmytry »

Online Robotbeat

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Also, if you're talking about microNewtons in the ambient air... That's absurd. The HVAC system would easily produce stronger forces on the experimental system. Heck, I could easily see it producing milliNewtons, not just microNewtons. I've had this very problem while teaching physics lab to electrical engineering students.

And even if it's enclosed, in order to reliably measure in the microNewtons, you need careful vibration isolation.

In order for me to be anywhere near convinced that there's the slightest possibility they're on to something, I'd have to have a very thorough examination of the experimental setup, or have someone else used to such highly sensitive measurements.
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Offline Rodal

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The original report of Brady et.al. "Anomalous report..."
The only experimental report written so far by NASA Eagleworks on the EM Drive
« Last Edit: 05/03/2015 01:52 AM by Rodal »

Offline Rodal

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But seriously what is this complaining about Engineers ?

And what is this complaining about the units?  The article you misquoted has the units next to the numbers

Quote from: http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/
However, in 2010, Prof. Juan Yang in China began publishing about her research into EM Drive technology, culminating in her 2012 paper reporting higher input power (2.5kW)

What's wrong with the units in 2.5kW  ???
« Last Edit: 05/03/2015 01:11 AM by Rodal »

Offline Mulletron

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My take:
There is a potential gradient formed within the cavity causing one end of the device to fall toward the other. The energy density at each end would differ due to the geometry leaving one side with a slightly higher mass-energy density than the other, creating the gradient.
Nathan Rogers

First, thanks for stimulating discussion.  :)

Yes there is. It is especially evident in TE012. This anisotropy alone isn't enough to explain the thrust.
http://forum.nasaspaceflight.com/index.php?topic=36313.1440
Where is the coupling?

What I have quoted above is theorized to lead to lots of exciting phenomenon like anisotropy of the vacuum itself yet proof remains elusive. It is very much predicted by multiple independent parties.

When you say "fall" though, that throws very controversial gravity research into the mix. What experimental evidence do we have to support the PV model by Puthoff et al?

It is very tempting to try and connect anisotropy of light in matter....(proven)to anisotropy of light in vacuum  (not proven), and then further try and tie that to gravity itself (not proven). It may very well be that way. But where is the proof? Right now there is none.

I looked back through the thread and we've discussed Dr. White's dependence on energy density rather than the Poynting vector.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1355995#msg1355995

To my knowledge, we haven't produced anything showing energy densities, like what Egan presented here:
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html

There's so much info buried in the thread that I might have lost it.

The thrust dependence on energy density theme is reoccurring. I'm not so sure that is the best approach to go with ONLY dependence on energy density. I think we need energy density and a defined Poynting vector.

It doesn't appear as if the original design intent was centered on the that idea:
http://www.emdrive.com/theorypaper9-4.pdf
http://emdrive.com/principle.html
..............Everything is about group velocity at Emdrive.com

A nice writeup here about the discrepancy: http://en.wikipedia.org/wiki/EmDrive#Theory

Dependence on the Poynting vector has more or less been abandoned here, mostly due to very good calculations by Dr. Rodal. I've been trying to sway conversation away from it.But I started thinking that the design of EMdrive is just way off the mark when it comes to the Poynting vector.

Especially when Shawyer himself is telling me the thrust is coming from the traveling wave:
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1368066#msg1368066

The only hope I see left for the Poynting vector would be unknowns which may introduce a Poynting vector such as uneven heat loss. Would a more detailed analysis uncover a non zero Poynting vector?

Based on my post from yesterday:
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1368066#msg1368066
I'm reconsidering throwing out the Poynting vector. Also see Rodal's post I linked to below which I rediscovered while writing this post.

It seems like the EMdrive as it is currently incarnated is needs a slight change in design. We want to keep the features which make it an energy storage device, but we need to introduce a very pronounced Poynting vector. A very high Q just kills that Poynting vector. Just as @Rodal said too.

This probably explains how Emdrives work, experimenters are telling us they work....but they barely work.

How can we get very high Q and get a nice Poynting vector at the same time?
That doesn't make sense to me, but that is what we need.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1354235#msg1354235

I believe that slight changes are needed in the basic design of Emdrive if it is ever going to be useful for spaceflight. The biggest factor I see is the addition of a better dielectric or magnetoelectric material.
http://arxiv.org/abs/1211.0530
« Last Edit: 05/03/2015 02:02 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Mulletron

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You accurately and completely answered the questions I asked.  Unfortunately, I didn't ask my questions very well.  :)

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1354235#msg1354235

A constant-amplitude standing wave does indeed result in a zero time-average Poynting vector.  However, I am questioning your conclusion that a constant-amplitude standing wave accurately represents a real resonator cavity such as the as-tested EM drive frustum.  Instead, I would expect a decaying amplitude standing wave to be a more accurate model/plot (as would be derived from a full solution to Maxwell's equations with proper boundary conditions such as non-zero resistance, etc).

Once a time-decaying standing wave is used for computation of a time-average Poynting vector, I'm having trouble seeing how the incident and reflected energy can perfectly cancel and become zero.  I'll readily admit I may be oversimplifying and/or missing a fundamental concept;  it's been a long time since I actually computed time constants for resonant cavities using Maxwell's equations and non-zero resistances.

Phrased a bit differently, I believe only excited modes with current/thermal losses in the base plates will significantly weight the direction of the time-average Poynting vector.  Each pair of incident/reflected waves would have a larger energy loss at the base plate with the excited E field (and therefore excited currents) than the energy loss at the opposing base plate.  For modes with near-zero E fields at the base plate boundaries, each incident/reflected wave pair would have a near equal energy delta regardless of which base plate they came in contact with;  the resulting time-averaged direction would be random and magnitude limited by the energy lost in the very first reflection (randomly either the large or small base, with a magnitude very close to zero).

I view this Poynting vector discussion to be completely independent of whether Dr. White's QV interactions, or some other classical physics can explain the EM drive anomalous thrust.  Just wanted to chime in on a what appeared to be the use of a constant-amplitude standing wave to describe a real-world system.  Your earlier observation of a non-zero time averaged Poynting vector seemed like a reasonable statement given that only excited modes with current/thermal losses in the base plates would quickly diverge from the simplified constant-amplitude standing wave model. 

Regards,
James
James, thank you for the interesting, thought-provoking discussion.  :)

Let's calculate some numbers to estimate what we are discussing.

The electromagnetic fields transition from the air or vacuum medium (where they are out of phase by 90 degrees) to the copper over an extremely small distance: a boundary layer. The skin depth for copper at 2 GHz is 1.48 micrometers = 58.2 microinches .  When showing the Poynting vector field distribution this distance is infinitesimal compared to the rest of the cavity.  In this very small distance inside the copper (1.48 micrometers ) the electromagnetic fields in the copper are out of phase by approximately 45 degrees (due to the high conductivity of copper).  For a transverse magnetic (TM) mode, the only electromagnetic field component that is continuous across the vacuum/copper interface is the electric field component tangent to the copper surface.

More interestingly (for this thread's discussion due to the significance that the NASA experimenters have placed on the dielectric being responsible for providing the measured thrust) is what happens in the High Density PolyEthylene (HDPE) dielectric polymer insert.  Because the dimensions of the dielectric are not negligible compared to the EM Drive's dimension, and the dielectric is not modeled as just a boundary condition.

The loss tangent of HDPE is reported to be

tan delta = 0.0004

Therefore the intrinsic impedance angle is

intrinsic impedance angle =(ArcTan[0.0004])/2

Therefore, inside the HDPE dielectric the electric and magnetic fields, instead of being out of phase by 90 degrees (as they are in the air or vacuum medium), will be out of phase by:

90 - (ArcTan[0.0004])/2 = 89.9998 degrees

This phase angle (89.9998 degrees)  will show practically no visual difference with 90 degrees at the resolution of the following image :



The Poynting vector inside the HDPE dielectric, instead of having a zero time average, will have the following factor multiplying ExB/mu :

Cos[90 - (ArcTan[0.0004])/2]/2 = 0.0000999999940000637

So, inside the HDPE polymer dielectric the Poynting vector has this small magnitude over a period (or multiples thereof).

So, the extent of this approximation, for the HDPE dielectric is about 0.01 % (which is negligible in comparison to several other approximations).


Now, let's examine what this (very small intensity Poynting vector time average) means, concerning the discussion in this EM Drive.

If one were to posit that the EM Drive's thrust is due to the very small magnitude of the time average of the Poynting vector due to these thermal losses (in the HDPE dielectric or in the copper):

1) It would mean that there should be more thrust with lower Q.  This is the complete opposite of what the experimenters like Shawyer claims (Shawyer claims that the higher the Q, the greater the thrust).  Notice that

Tan [loss angle] = Tan[ 2 impedance angle ]= 1/Q

2) All the equations proposed so far (by Shawyer, McCulloch and @Notsosureofit) have predicted thrust proportional to Q.  This is the complete opposite of what such a Poynting vector would predict (it would predict thrust proportional to 1/Q instead), because

Tan delta= 1/Q

measured Q        effective tan delta

7320                  1.366* 10 ^(-4)
22000                4.545* 10 ^(-5)
10^6                  10^(-7)

3) It would mean that experimenters like Shawyer and Fetta are in the completely wrong track pursuing superconducting EM Drives, as superconducting EM Drives would lead to practically no thrust (the opposite of what they claim) because superconducting EM Drives would display practically no heat losses and hence zero time average Poynting vector.

4) Considering the HDPE dielectric acting as a sink (energy flowing from the EM Drive towards the HDPE where the energy is dissipated internally in the dielectric polymer due to its tandelta and hence irretrievably lost instead of being reflected), the Poynting vector would be directed towards the HDPE dielectric, that is towards the small base, and hence the EM Drive should experience a recoil force and acceleration towards the big base.  This is the opposite direction force found in NASA's experiments with the dielectric.  (Recall that NASA Eagleworks found no thrust force with mode TE012 without a HDPE dielectric and that with the HDPE dielectric inserted at the small base they found a force and acceleration directed towards the small base.)

Dang! How did this slip through the cracks? Read the whole thing. See #3! This has been bubbling up from all the discussion, up until now.

@Rodal, we need you more than ever to help quantify this missing Poynting vector that everyone says isn't there in an unloaded cavity, and absolutely is not there when calculated using standard classical methods.

James is right, there is NO WAY there is a perfect standing wave in there.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1354319#msg1354319

I see a way forward here:

1) Find the tiny missing Poynting vector. TE012 is a candidate. See if it is consistent with the anomalous thrust.
2) If that works, find a way to enhance the Poynting vector.
3) Plug in a Casimir momentum theory that is consistent with established scientific principles.
4) Test, rinse, repeat.

#1) and #3) should be enough to stop the handwaving.
#2) and #4) to make it work better and to test ideas.

IRT to this and many posts about TE012, the Poynting vector is self canceling without the dielectric.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1352885#msg1352885

Quote
I showed the fact that boundary conditions for the transverse electric (TE) electromagnetic mode shapes all Poynting vector components vanish at the walls of the EM Drive and the fact that for mode shape TE012 without the dielectric the Poynting vector is self-cancelling. This is consistent with NASA Eagleworks results and supports NASA Eagleworks preference for the transverse magnetic (TM) modes over the transverse electric (TE) modes.

I can't remember if the Poynting vector was self canceling with the dielectric or not. I'm pretty sure it was not self canceling WITH the dielectric. Is that accurate?

Keep in mind, NASA reported no thrust at TE012 without dielectric, and good thrust with dielectric.
« Last Edit: 05/03/2015 08:30 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline CW

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One question, regarding Mr. Shawyer's understanding of what's going on in his EM-drive:

Let's pretend we are a photon. We are traveling at c. Due to Lorentz-contraction of space in our traveling direction, how does the universe look like for us, a photon? I think that the universe actually appears as a sort of surface in our traveling direction, due to the maximum Lorentz contraction of space in front of us.

The question is: For a photon, moving at c, how does the inner geometry of an EM-drive frustum really look like? Could there be an apparent nonlinearity, from the viewpoint of a photon, within an EM-drive device, that we in our everyday, non-Lorentz contracted world don't perceive? Is there someone on the forum who can do the math that projects how the maximum-Lorentz contracted universe looks like for a photon, and apply this to an EM-drive environment?

Best,
CW
Reality is weirder than fiction

Offline Mulletron

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Excellent work posting the Shawyer emails.

Question on your test rig. You are aware, according to Shawyer, a non moving EMDrive will not generate any thrust and that it must move to enable thrust to be indirectly measured? Are you planning to use a rotary test?

http://www.emdrive.com/EmDriveForceMeasurement.pdf

Additionally his test with a dielectric, resulted in reduced thrust generation.

http://www.emdrive.com/iac2014presentation.pdf - page 2

Wish you all the best of luck. Would be interested to replicate your device.

That is the missing Poynting vector. See above in bold. Think about Doppler shift inside a resonant cavity when it moves, then photons fall out of resonance, and go evanescent. That energy is lost to work/heat.

The energy flowing back into the cavity is the missing Poynting vector.

This is common to all resonant modes.

From the http://www.emdrive.com/EmDriveForceMeasurement.pdf
Quote
Because the thruster is at rest, no force will be measured on the load cell.
i.e. F = T-R = 0
It therefore appears that a force measurement can only be made in a dynamic environment, ideally by allowing the thruster to accelerate, measuring that acceleration, and then calculating the thrust from T = -Ma.

How is the Eagleworks pendulum satisfying that requirement? That it must be moving in order to get a measurement? All this noise.....see screenshot.

Reminds me of the old light in a box discussion we had.
http://usersguidetotheuniverse.com/?p=2865 (also where the math is)
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1334277#msg1334277
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1334560#msg1334560


Please review page 2
http://www.emdrive.com/iac2014presentation.pdf

Note the use of a dielectric resulted in weaker thrust and in the opposite direction, line 3, to a non dielectric EMDrive, line 4, 5 & 6.

This suggest EW may have found a new way to gen thrust, via a dielectric, that appears to work when the test device is fixed/stationary and in the opposite direction to a classic EMDrive.

Interesting.
TheTraveler keeps sending me PMs which are good stuff. He needs to post in open forum. He's essentially saying the dielectric section also serves to "bootstrap" this initial acceleration requirement.

Probably should have listened more closely to what Shawyer was saying. Knowing what we know now, this is an opportunity to improve these devices by looking at how to improve energy flow through the cavity with different dielectric and magnetoelectric materials, or some other way......

http://arxiv.org/abs/1211.0530 A whole bunch of candidate materials.

This has some interesting ramifications too. An Emdrive just sitting there on the bench is subject to a constant 1g proper acceleration.
« Last Edit: 05/03/2015 02:01 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

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