Author Topic: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive  (Read 192178 times)

Offline Star One

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #320 on: 05/03/2015 10:45 PM »

Just a general comment even by the low standards of space & science reporting online it seems this particular article has suffered terribly in its wider reporting and analysis. I hope this hasn't caused any damage to the site's reputation.
It is not so much the "low standards" but the uncontained urge for sensational reporting that usually does more damage then good.
News reporting feels compelled to scale down information to its lowest understandable form, omitting all nuances and subtleties, hence stripping it from its real content and meaning. That's how the casual "mentioning of an observation of an anomaly reported by a NASA engineer" turns into "NASA discovers Startrek-type warpdrive" in no time...
Sadly, this does way more harm then good, because it tends to discredit any research attached to the subject.

In the same category, you have those who insist in turning the EMdrive into an over-unity device. It really doesn't help for the credibility of the EMdrive. Just stay away from any of those "contaminated" topics and focus on the device, on the theoretical and practical issues of the device...

The upcoming high power test, scheduled for July (according P.March), will be the make or brake event for me as I'm still on the balance. I remain skeptical, yet I do carry the hope it turns out to be a positive test, simply because it would mean a giant leap forward for human space exploration (stationary orbital spacestations, human interplanetary travel and even interstellar probe travel).. we'll see... give it another 2-3 months......

Even if it does work there's a vast gap between that & going on holiday to the moon on a regular four hour shuttle flight. It seems as if people expect to be flying around the Solar System by next year.

Offline aceshigh

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #321 on: 05/03/2015 10:51 PM »
It is known to be impossible to violate energy conservation. Stating that it clearly does is a non-sequitur, as it implies complete knowledge of how Emdrive works (if it really does work). There is no accepted theory of operation for this thing.

For all we know, the universe might be a ginormous energy bank that you can borrow from and loan to; if you know how. You still have to balance the books at the end of the day. (pure conjecture)

I think we need to remember that until proven otherwise, this copper can is a black box. It is what it is, regardless of what some guy's theory says about it, which is likely wrong until proven correct.


I just started reading a sci-fi book where they have relativistic, non FTL travel that work exactly like that. I almost thought I was reading something about the EM Drive when the author started describing it.

Starfarers, by Poul Anderson

Offline JPHar

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #322 on: 05/03/2015 11:07 PM »
This may sound off the wall, but I have an idea for low cost experiments. 

Use a Crooke's Radiometer positioned adjacent to the device in the thrust direction.  Distance to the device, pane charge, temperature, pressure, polarization of light allowed through the radiometer wall, and mill pane materials are controls to be varied.  Very low mass panes should be constructed, perhaps by coating thin slivers of aerogel through vacuum metalization or other very thin layer material application processes for the emissive and aborbant sides of the pane. 

Hypothesis: If any propellant is present, to include virtual particles temporarily conferred enough energy to bring them into a non-virtual state, then it should be possible to observe radiometer motion under the right combination of conditions and materials.  The conditions and materials that achieve radiometer motion then provide insight into the nature of propellant.

I do not have the expertise to evaluate which materials and conditions should be tried, nor in which order. 

Skepticism: The mass and friction of the radiometer system must be low enough that a fraction of the thrust generated by the device is sufficient to cause rotation.  Experiments using materials with thermoelectric properties or other sophisticated materials may be required and may not be inexpensive. 

edit: To clarify, the goal in the experiments would not necessarily be to demonstrate thermal phenomena, but to adapt the operating principle of the radiometer to different interactions with the environment until the correct interaction is discovered.
You do know how a Crooke's device works don't you? Why would this elucidate anything to do with an EM drive?
Maybe I am missing something though...

Crooke's Radiometer works by inducing a pressure difference in partial vacuum.  One side of each mill pane is engineered to be more thermal absorbent and the other to be more thermal emissive.  The gas must be at a sufficiently low pressure that thermal potential difference is possible, but sufficiently high pressure that heat radiates on the emissive side. 

I don't see why this wouldn't work via any means of creating a thermal energy differential between different sides of the panes.  Aerogel is an extraordinarily low-mass thermal insulator, and materials may be selected to convert electromagnetic energy to thermal to fulfill the operating principle in subsequent tests.  This facilitates a platform for testing of various frequencies of electromagnetic radiation, attempts at generating the thermal differential via exothermic reaction, or whatever else the more knowledgeable engineers at NASA may deem worthy of testing.

Continuing along that line of reasoning, any particles of any kind that act as a propellant must carry energy in symmetry with that presenting via thrust, if this device does not demonstrate a violation of the conservation of momentum.  Therefore, if the hypothetical propellant carries any energy in a form convertible to thermal, then it may be detected this way.  The means of detection then facilitate inference of the propellant's properties.

This may be used to eliminate possibilities. 

Personally, I'd use four high speed cameras arranged at 0 radians, pi/2, pi, and 3pi/2, with the thruster device at an angle between two of the cameras.  Then, a computer could time video recording for an effective motion framerate equal to four times that of one of the cameras (purely for motion detection purposes).  MIT has software that can detect and highlight motion imperceivable to humans. 

I'd begin with gold nanocrystals on one side of each mill pane and vacuum metalized iridium on the other side.  But then, that's just a guess off the top of my head.  If I'm correct that gold nanocrystals have significant heat conduction properties and specific heat while iridium has significant conduction properties and low specific heat, then this should work as a very sensitive thermal energy detector. 

From there, light polarization film on the outer glass enclosure of the Crooke's apparatus, various experiments with electromagnetic interference with any EM waves passing into it, and whatever other trials may suit the researchers allow for elimination of various possibilities, one by one.  Different kinds of energy tested for using a similar experimental setup provide a framework to demonstrate significance if rotation of the radiometer is achieved.

But like I said earlier, it's a very old tool with a few tweaks in this idea.  There are explanations for the thrust that would not be detected this way.

Another useful experiment would be to point two of these devices' thrust direction at each other to see if the principal of propulsion can even interact with itself.
« Last Edit: 05/03/2015 11:11 PM by JPHar »

Offline vulture4

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #323 on: 05/03/2015 11:16 PM »
...

Those people do not know the struggling of a scientist to get just a little more funding in their lab where only 3 or 4 other colleagues work with them. Eagleworks has an old dying RF amp and they do not even have the bucks to replace it… Paul had to build the copper frustum at home, in his wife's dining room! Really people would be shocked if they knew that....
Yes, the more crude the instrumentation, the stronger the effect.
I also do basic research at a NASA center and I agree that even the most meager resources are extremely hard to come by. I had to personally buy a lot of our equipment on E-bay with money I made working weekends at a second job. I strongly feel that all NASA centers should have a substantial budget for internally selected research projects. Our nation is falling behind in basic research. Unfortunately it requires at least modest taxpayer funding, and the NASA budget is flat, and every dollar is spoken for. NASA's viewpoint is they give you a little seed money and in less than a year you have to turn your idea into something venture capitalists will be fighting to finance. Not so easy when you are trying to understand basic science. I'd be happy to see this project better financed, and certainly to see a physicist added to the team,  but there are many other deserving projects that are rejected or abandoned every year without notice but aren't talked about much because they are not as controversial.
« Last Edit: 05/03/2015 11:36 PM by vulture4 »

Offline KittyMoo

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #324 on: 05/03/2015 11:16 PM »
But a Crooke's device will rotate even in a uniform radiation field, even your fancy variant.
I am not clear how it could be used to test an EM drive, which doesn't emit any photons in a preferred direction.

Offline Prunesquallor

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #325 on: 05/03/2015 11:23 PM »

Even if it does work there's a vast gap between that & going on holiday to the moon on a regular four hour shuttle flight. It seems as if people expect to be flying around the Solar System by next year.

NASA is an applied research organization. To justify spending any resources on this, a space flight application is needed. I don't see a problem with pointing out potential applications if they fall within postulated performance. Yes, there are many unknowns about the emdrive's practical performance given it works at all. But if it just a laboratory curiosity, NASA is the wrong group to be working on it.
Retired, yet... not

Offline JPHar

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #326 on: 05/03/2015 11:27 PM »
But a Crooke's device will rotate even in a uniform radiation field, even your fancy variant.
I am not clear how it could be used to test an EM drive, which doesn't emit any photons in a preferred direction.

It doesn't emit EM radiation that has been detected so far.  That does not mean that every possible mode of energy transference to ... something ... has been eliminated. 

The experiment would need to be calibrated by measuring rotation caused by ambient energy, or (better yet) such rotation could be eliminated completely if at all possible.  But if there is any way to convert whatever comes from the back of that thing into thermal energy then there is some way to have it affect the rotation of the radiometer.  And if thermal energy is transmitted across space, then the energy can be measured to establish conservation of momentum.

The benefit of these experiments is that they can eliminate possibilities at low cost. 

The only three things I can think of that would not at all be detectable this way are gravity, extraordinarily short-lived virtual particles, or some means by which a microwave is split such that one interacts with the other. 

For the virtual particle possibility, I'd suggest tapping these people:

http://scitation.aip.org/content/aip/journal/apl/98/23/10.1063/1.3597793

For the gravity possibility, I'd suggest eliminating every other possibility, even if it involves some blind alley testing.  For the microwave self-interference (correct term?) possibility, I'd suggest using two of these devices in an attempt to elicit an interaction between them such that detectable radiation indicating the effect results.

edit: To be clear, the radiometer idea may seem crazy, but it's an attempt to come up with a very low cost means of experimentation. 
« Last Edit: 05/03/2015 11:30 PM by JPHar »

Offline KittyMoo

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #327 on: 05/03/2015 11:34 PM »
You make good and fair points.
I just disagree that it is worthwhile for EM drive experiments.
Probably no harm in trying, but I just can't see it myself.

Offline JPHar

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #328 on: 05/03/2015 11:38 PM »
To be fair, I wouldn't be surprised if I'm flat out wrong.  It's just the next step I'd take.  Studying and debating theory only gets one so far when it seems that the theory doesn't suffice.  Sometimes, it's necessary to bang rocks together.  :D 

Offline vulture4

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #329 on: 05/03/2015 11:47 PM »
"It doesn't emit EM radiation that has been detected so far. "  The resonator in the NASA reports clearly emits EM radiation in the infrared band, and in an asymmetrical manner. IR radiation produces a recoil force and is now believed to be responsible for the anomalous acceleration of the Pioneer probes.
« Last Edit: 05/03/2015 11:50 PM by vulture4 »

Offline KittyMoo

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #330 on: 05/03/2015 11:55 PM »
"It doesn't emit EM radiation that has been detected so far. "  The resonator in the NASA reports clearly emits EM radiation in the infrared band, and in an asymmetrical manner. IR radiation produces a recoil force and is now believed to be responsible for the anomalous acceleration of the Pioneer probes.
That would make it a photon rocket which the EM device clearly is not... Read the main thread for analysis of this.

Offline JPHar

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #331 on: 05/04/2015 01:12 AM »
I must agree with a FAQ suggestion I saw from the main thread at this point.  It's not a trivial task to compile it, but perhaps instead a topic index with brief synopses and links would suffice if a sufficiently qualified person can identify worthy posts. 

This kind of thing excites people who have a passion for science because in an open question, it's feasible that a nudge in the right direction can come from anywhere.  This is also an important enough topic that it can clearly be used to spur public interest in NASA and interest in related topics.  But the discussion needs a framework that's approachable from an interdisciplinary perspective. 

After that point, reference material might be discussed to assist those of us running to catch up.  After the vacuum test, it appears to be likely that this will be an increasingly popular topic with time, and that calls for preparation.

Offline Collapsar

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #332 on: 05/04/2015 01:52 AM »
Before we gets lots of questions about terrestrial applications.

Quote
18.
Q. How can the EmDrive produce enough thrust for terrestrial applications?
A. The second generation engines will be capable of producing a specific thrust of 30kN/kW. Thus for 1 kilowatt (typical of the power in a microwave oven) a static thrust of 3 tonnes can be obtained, which is enough to support a large car. This is clearly adequate for terrestrial transport applications.
The static thrust/power ratio is calculated assuming a superconducting EmDrive with a Q of 5 x 109. This Q value is routinely achieved in superconducting cavities.
Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.

http://emdrive.com/faq.html

Maybe this is a stupid question, but if thrust drops off rapidly when used to accelerate the vehicle along the thrust vector, how can it be useful for interstellar travel?  You would be wanting to accelerate the vehicle in the same direction of the thrust for a long period of time (toward the target star system).  I can only imagine that it would be useful for lifting payloads to a certain altitude, or repositioning from LEO to GEO.  Watching the Shawyer Youtube videos, he even says that a propellant is needed to get up to orbital velocity once the altitude is achieved.

Offline ragingrei

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #333 on: 05/04/2015 02:16 AM »
Question from a layman... if the EM Drive works as described, would there be a force against whatever is behind it?

For example, a helicopter causes a lot of wind beneath the blades and displaces dust. Would an EM Drive do the same?

Offline ChrisWilson68

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #334 on: 05/04/2015 02:33 AM »
Question from a layman... if the EM Drive works as described, would there be a force against whatever is behind it?

For example, a helicopter causes a lot of wind beneath the blades and displaces dust. Would an EM Drive do the same?

That's kind of like asking if a Unicorn existed what it's horn would be made of.

There are different proposed theories for what might cause an EM Drive to work, if it did work.  Some people think all the proposed theories are likely wrong, even if it does work.

This is like people speculating about what the canals of Mars were made from, back during the craze when so many people thought they saw canals at the fringe of detectability through their telescopes.

Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #335 on: 05/04/2015 02:41 AM »
Before we gets lots of questions about terrestrial applications.

Quote
18.
Q. How can the EmDrive produce enough thrust for terrestrial applications?
A. The second generation engines will be capable of producing a specific thrust of 30kN/kW. Thus for 1 kilowatt (typical of the power in a microwave oven) a static thrust of 3 tonnes can be obtained, which is enough to support a large car. This is clearly adequate for terrestrial transport applications.
The static thrust/power ratio is calculated assuming a superconducting EmDrive with a Q of 5 x 109. This Q value is routinely achieved in superconducting cavities.
Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.

http://emdrive.com/faq.html

Maybe this is a stupid question, but if thrust drops off rapidly when used to accelerate the vehicle along the thrust vector, how can it be useful for interstellar travel?  You would be wanting to accelerate the vehicle in the same direction of the thrust for a long period of time (toward the target star system).  I can only imagine that it would be useful for lifting payloads to a certain altitude, or repositioning from LEO to GEO.  Watching the Shawyer Youtube videos, he even says that a propellant is needed to get up to orbital velocity once the altitude is achieved.

Yeah, think it on through. Forget interstellar, think of the power difference required to move east rather than west on the earth. Due to the rotation of the planet you are traveling at 1000 mph to the east. Trying to go that way would be like hitting a brick wall. But it gets worse. The earth orbits the sun at 66000 mph so trying to go up at the wrong time of day would be far worse.

The device makes no sense as stated.

Online KelvinZero

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #336 on: 05/04/2015 02:45 AM »
Maybe this is a stupid question, but if thrust drops off rapidly when used to accelerate the vehicle along the thrust vector, how can it be useful for interstellar travel?  You would be wanting to accelerate the vehicle in the same direction of the thrust for a long period of time (toward the target star system).  I can only imagine that it would be useful for lifting payloads to a certain altitude, or repositioning from LEO to GEO.  Watching the Shawyer Youtube videos, he even says that a propellant is needed to get up to orbital velocity once the altitude is achieved.
Obeying conservation of energy could still give you a 'velocity proportional to kinetic energy squared' relationship, which is what they are trying to claim here. This is still vastly better than the exponential relationship between propellent and velocity that you get from the rocket equation.

The problem is that they are glossing over that in the case where energy is conserved there appears to have to be a particular frame of reference, such as the air that a plane moves through. They sort of imply you are always stationary wrt to this frame of reference at the moment you turn the machine on. In this case energy you can get more energy than you put in by continually turning the machine off and on.. but it is not really clear what is being claimed which to me is the most significant problem by far. Without a clear claim there is no way to falsify it.

My impression is that the original theory that lead to the experiment has been found in error, but experimenters still feel they found an effect, though the reason for such an effect is now up in the air. It is the lack of one specific theory that makes it very hard to distinguish effect from artefact.

Science is often willing to invest far more, and make conclusions on the basis of far more sensitive phenomena than what is claimed here. Consider the multibillion dollar searches for new particles that only occasionally collide with supercooled detectors far below the surface to avoid cosmic rays (or perhaps it is colliders that get the big bucks, it doesnt matter). The difference is that these are testing very well defined theories, so it is far easier to discard anomalous values as not proof of a specific claim. In those tests getting a result a thousand times stronger than you predicted is not lauded as a step forwards, it is time to rip out your hair, retest all your equipment and finally rip up your theory and try to think of another one. :)

Offline ragingrei

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #337 on: 05/04/2015 03:01 AM »
Question from a layman... if the EM Drive works as described, would there be a force against whatever is behind it?

For example, a helicopter causes a lot of wind beneath the blades and displaces dust. Would an EM Drive do the same?

That's kind of like asking if a Unicorn existed what it's horn would be made of.

There are different proposed theories for what might cause an EM Drive to work, if it did work.  Some people think all the proposed theories are likely wrong, even if it does work.

This is like people speculating about what the canals of Mars were made from, back during the craze when so many people thought they saw canals at the fringe of detectability through their telescopes.

Correct me if I'm wrong, but those don't sound like very pertinent analogies.

It seems reasonable to suppose that if they were able to measure some thrust, then they might have measured or might be able to surmise what effects are observed nearby.

Offline WarpTech

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #338 on: 05/04/2015 03:55 AM »
So this made me think about the time I took a 3 port circulator apart. For those that are not familiar with circulators, the work like this:
Put power in port 1 and it comes out port 2, put it in 2 and it comes out 3, put it in 3 and it comes out 1. All with out much loss. But if you try to go backwards, say 3 to 2,  you loose 99% of the power.

Cool little device. So when I take it apart all it is is a flat triangle of copper, 2 triangle shaped pieces of ferrite, and a magnet.

If you don't know the math behind it, is looks at first blush as "silly" as the emdrive. No way could it do that. But it does. This thing may well work, we just don't know the math.

I'm an Engineer and I've studied the Polarizable Vacuum Model of General Relativity. What it would say is the following;

As a waveguide, the group velocity is something like;

v_g = c x sqrt(1 - (c/2d*f)^2)

Where, c is the usual speed of light, d is the diameter of the cylinder, and f is the frequency of the microwave excitation.

c/2d = fc,  is the Low cut-off frequency of the waveguide.

The refractive index depends on the Low cut-off frequency as a function of the diameter,

K = 1/sqrt( 1 - (fc/f)^2)

For f >> fc, K~1. But for frequencies in the band fc1 < f <~ fc2, K is much larger.

There is a strong gradient in the refractive index from one end of the cone to the other. This "mimics" gravity, as interpreted in the PV Model.

Therefore, we can assume there is a "gravitational" gradient in the microwave band refractive index, along the length of the cone. At one end they have diameter d1, and at the other end they have diameter d2, and d1 > d2. Below fc1, the mode frequencies exponentially decay to zero. Just like the Casimir effect.

Here is how it conserves momentum;

In the PV Model, momentum transforms as,

p => p*sqrt(K)

In a resonant cavity, p is the SUM of all the photons “in phase", minus the losses of the cavity. 

However, as photons “fall” from the large end toward the small end, they gain momentum, which is passed on to the cone when they are reflected from the small end. The photon then loses momentum as it travels back to the large end, where it imparts “less” momentum to the large end. The result is a NET propulsion in the direction of the small end. In other words, the photons are blue-shifted falling forward, and red-shifted going backwards, due to the gradient in the refractive index. It is literally gravitational red & blue shift, according to the PV Model.

The interesting thing is, the refractive index in the waveguide does not depend on the power of the microwaves, or the energy density. It is simply a matter of the geometry and frequency band relative to the cut-off. What matters more, is having enough resonant momentum stored to make the effect noticeable.

That’s IMHO as an engineer of course. Any comments?

See PV Model: https://www.researchgate.net/publication/223130116_Advanced_Space_Propulsion_Based_on_Vacuum_%28Spacetime_Metric%29_Engineering

Todd D.

Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #339 on: 05/04/2015 04:14 AM »
So this made me think about the time I took a 3 port circulator apart. For those that are not familiar with circulators, the work like this:
Put power in port 1 and it comes out port 2, put it in 2 and it comes out 3, put it in 3 and it comes out 1. All with out much loss. But if you try to go backwards, say 3 to 2,  you loose 99% of the power.

Cool little device. So when I take it apart all it is is a flat triangle of copper, 2 triangle shaped pieces of ferrite, and a magnet.

If you don't know the math behind it, is looks at first blush as "silly" as the emdrive. No way could it do that. But it does. This thing may well work, we just don't know the math.

I'm an Engineer and I've studied the Polarizable Vacuum Model of General Relativity. What it would say is the following;

As a waveguide, the group velocity is something like;

v_g = c x sqrt(1 - (c/2d*f)^2)

Where, c is the usual speed of light, d is the diameter of the cylinder, and f is the frequency of the microwave excitation.

c/2d = fc,  is the Low cut-off frequency of the waveguide.

The refractive index depends on the Low cut-off frequency as a function of the diameter,

K = 1/sqrt( 1 - (fc/f)^2)

For f >> fc, K~1. But for frequencies in the band fc1 < f <~ fc2, K is much larger.

There is a strong gradient in the refractive index from one end of the cone to the other. This "mimics" gravity, as interpreted in the PV Model.

Therefore, we can assume there is a "gravitational" gradient in the microwave band refractive index, along the length of the cone. At one end they have diameter d1, and at the other end they have diameter d2, and d1 > d2. Below fc1, the mode frequencies exponentially decay to zero. Just like the Casimir effect.

Here is how it conserves momentum;

In the PV Model, momentum transforms as,

p => p*sqrt(K)

In a resonant cavity, p is the SUM of all the photons “in phase", minus the losses of the cavity. 

However, as photons “fall” from the large end toward the small end, they gain momentum, which is passed on to the cone when they are reflected from the small end. The photon then loses momentum as it travels back to the large end, where it imparts “less” momentum to the large end. The result is a NET propulsion in the direction of the small end. In other words, the photons are blue-shifted falling forward, and red-shifted going backwards, due to the gradient in the refractive index. It is literally gravitational red & blue shift, according to the PV Model.

The interesting thing is, the refractive index in the waveguide does not depend on the power of the microwaves, or the energy density. It is simply a matter of the geometry and frequency band relative to the cut-off. What matters more, is having enough resonant momentum stored to make the effect noticeable.

That’s IMHO as an engineer of course. Any comments?

See PV Model: https://www.researchgate.net/publication/223130116_Advanced_Space_Propulsion_Based_on_Vacuum_%28Spacetime_Metric%29_Engineering

Todd D.

In what sense does this conserve momentum?

Treat the device as a black box. I don't know or care what is happening inside it. At time T0 it has no momentum. Turn it on and let it accelerate so that it has some velocity and so momentum at time T1. Unless you can point to something with the same amount of momentum going in the other direction then by definition you have violated conservation of momentum. What happens inside the box simple does not affect that fact.

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