Author Topic: EM Drive Developments - related to space flight applications - Thread 4  (Read 934734 times)

Offline WarpTech

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Not coming from the RF world, I wonder why this whole discussion about Q can't settle on Q=2*π*energy_stored/energy_dissipated_per_cycle as a standard. Out of curiosity, isn't it possible to switch off a RF source fast enough (a few cycles) and get this Q value by observing only the time constant of the decay of amplitude with a minimally invasive probe ?

BTW, not wanting to sound insistent but there is no answer to my questions about the relation of Q and "losses per round trip" (in the context of a linear resonant set up). If I am making a mistake by thinking "number of bounces" when hearing Q, then I'm not the only one : Think of it like the number of times a photon bounces inside a mirrored cavity. A clarification might be useful.

My conjecture on this would be that, a small cone angle will cause more bounces and a higher Q. However, my feeling is that as the wave propagates from the small end to the big end, it is reflecting off the side walls. Each reflection off the side walls imparts a tiny bit of momentum to the frustum. So the more bounces off the side walls (not the end plates) will produce more thrust. This means that a slower group velocity, bouncing over a longer period of time, would give higher thrust. This leads to the idea that the frustum should be shaped more like a trombone with a long throat. But... none of the theories so far support this idea, but none have tried either.
Todd
Todd, but the axial force component due to the side walls equals Sin[theta]*SideWallForce, where theta is the cone half-angle.  For theta = 0 ( a cylinder) the axial component due to the SideWallForce is Sin[0]*SideWallForce=0, it is zero no matter how large is the SideWallForce.  For small theta, the SideWallForce axial component is very low.  So, even if one grants you that the SideWallForce may be larger for small cone angle, the axial component is small.  Comments?

But, say Sin(Theta) were decreased by 1% value, how many additional bounces will that deliver? It's non-linear, so I don't know where the sweet spot is. Could a slightly lower cone angle provide much higher thrust because there are millions of more bounces at that angle? In other words, less thrust per bounce, but many more bounces. I don't know yet, but it is interesting and is yet "another" way of replacing Q with something else.
Todd

Offline rfmwguy

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Offline rfmwguy

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Thanks Shell...it was fun...a dry run for the fulcrum test in a couple of weeks. Think we had 24 viewers, not bad for short notice only here on NSF.

Offline Dasun

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Great work rfmwguy, watched the webcast and everything worked fine , look forward to the "real run" - best of luck!

And thanks to Dr Rodal for being a really effective ringmaster of this fringe circus!!!!
I am vendor neutral, I just want to see spacecraft fly.

Offline demofsky

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Offline meberbs

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Thinking about the ongoing controversy regarding TheTraveller's and Shawyer's theory raises a question for me.  Please forgive if this has been addressed in one of the earlier threads.

If Shawyer's theory is wrong then is Cullen's eqn 15 also incorrect??  Eqn 15 seems to be the bedrock of the theory (the bible they punch :D).

I am trying to unpack the controversy a bit from the recent standard of "the physics/theory is wrong".

Cullen is discussing a constant cross section wave guide the resonator that Shawyer is trying to analyze is a more complicated shape so Cullen's equation may or may not be applicable. There is probably something wrong with Shawyer's equation 7 since it ignores forces on the side walls. There are proofs in EM theory that show that EM waves will produces a time averaged net 0 force for any shape cavity, and any result that contradicts this either has incorrect math, or an assumption inconsistent with Maxwell's equations i.e. new physics.

If you are looking for a specific part of Shawyer's paper that is wrong, just after equation 7, he applies the special relativity velocity addition formula. This formula is used to transform the velocity of something measured in one reference frame to the velocity that object would appear to have in another reference frame.  Shawyer applies it to a random equation that he had rearranged to have a subtraction of velocities. He is not transforming reference frames, so applying the formula there is nonsense.

When he calculates the forces on the 2 plates separately for a waveguide moving at a different velocity, he is using the equation in the right context, but fails to account for the fact that he has to transform all of the variables into the moving reference frame. Some quantities that change are the cavity length, resonance frequency, injected frequency, and the energy stored in the waves. His claims of thrust reversing at a high fraction of the speed of light are a symptom of this misapplication of special relativity.

The fact that his paper's conclusions are completely wrong is sufficiently obvious to most experts that they don't even bother looking for what his specific mistakes are. The experimental results from multiple labs are another story, and those results are the only reason the EM drive is not completely dismissed.

Offline demofsky

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Thinking about the ongoing controversy regarding TheTraveller's and Shawyer's theory raises a question for me.  Please forgive if this has been addressed in one of the earlier threads.

If Shawyer's theory is wrong then is Cullen's eqn 15 also incorrect??  Eqn 15 seems to be the bedrock of the theory (the bible they punch :D).

I am trying to unpack the controversy a bit from the recent standard of "the physics/theory is wrong".

Cullen is discussing a constant cross section wave guide the resonator that Shawyer is trying to analyze is a more complicated shape so Cullen's equation may or may not be applicable. There is probably something wrong with Shawyer's equation 7 since it ignores forces on the side walls. There are proofs in EM theory that show that EM waves will produces a time averaged net 0 force for any shape cavity, and any result that contradicts this either has incorrect math, or an assumption inconsistent with Maxwell's equations i.e. new physics.

If you are looking for a specific part of Shawyer's paper that is wrong, just after equation 7, he applies the special relativity velocity addition formula. This formula is used to transform the velocity of something measured in one reference frame to the velocity that object would appear to have in another reference frame.  Shawyer applies it to a random equation that he had rearranged to have a subtraction of velocities. He is not transforming reference frames, so applying the formula there is nonsense.

When he calculates the forces on the 2 plates separately for a waveguide moving at a different velocity, he is using the equation in the right context, but fails to account for the fact that he has to transform all of the variables into the moving reference frame. Some quantities that change are the cavity length, resonance frequency, injected frequency, and the energy stored in the waves. His claims of thrust reversing at a high fraction of the speed of light are a symptom of this misapplication of special relativity.

The fact that his paper's conclusions are completely wrong is sufficiently obvious to most experts that they don't even bother looking for what his specific mistakes are. The experimental results from multiple labs are another story, and those results are the only reason the EM drive is not completely dismissed.

Excellent!.  Exactly the kind of detail I was looking for!  I think the discussion in this series of threads has reached a point where even folks who are not experts in this domain are interested in detailed critiques like this.

The detailed dialog of WarpTech and DeltaMass has given me a much deeper appreciation of what might or might not be happening.  Your excellent post also does this.  Thank you. 

And I certainly hope for more of this from both sides of the various controversies here! :D

Offline watermod

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No matter if the EM drive theory fails or not I do have a more basic physics question.

Back up to a simple situation where my finger or something pushes something else.   The actual protons and neutrons (maybe electron clouds) do not touch (unless in a particle collision device like Fermi or Cern) so what wavefronts or fields are coming into play to transfer the force from the pusher object?    Strong? Weak? Gravity? Magnetic? Electrical? A mixture? 

Has touching like that been modeled down to the field level? 
Has its relationship to reference frames in space been modeled?

I keep thinking rocket exhaust throwing mass out the back of the rocket - what does it really imply for different reference planes and the structure of space. 

+ added later:   And then there is the bit with particles that don't react with reference frames or matter unless they do a head on collision like the neutrino flashes in huge pools of carbon-tet.    So what's the traction factor?
« Last Edit: 08/08/2015 05:18 am by watermod »

Offline TheTraveller

but in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.
Todd

So Dr. Ray Kwok is also wrong?

I see nothing incorrect about what Dr. Kwok said. He said "Resonators". An antenna is a resonator and so is a cavity. One is an open system, the other is a closed system. The preferred methods are different at a "National Standards" level, according to @rfmwguy. While I agree 100% that the experimenters to date have consistently used the S11 method, that does not mean it is the "standard" way to do it. You are arguing that "In the EM Drive world" this is how it's done. Perhaps this is true, but is no less true that this is NOT the "standard" way to do it.

Stop arguing about it and accept that fact please. You're driving everyone bonkers with your obstinance and defense of obvious incongruences. I do not follow others. I make mistakes, try to understand learn from them and forge my own path and from what I've seen, that is how most of us here operate.
Todd

My point is Shawyer, Prof Yang, Eagleworks & Prof Tajmar measured unloaded Q via a 1 port S11 3dB off the max return loss dB and frequency.

Why did they do it that way?

Because the cavity in operation has no load, no output port. A high Q cavity is like a high impedance parallel LC circuit where any external load on the circuit / cavity will introduce additional circuit / cavity losses and thus drop circuit / cavity Q.

The EMDrive operates as a high Q unloaded cavity and doing 2 port S21 cavity Q measurement, where the 2nd port or probe removes some of the cavity energy, which increases cavity losses, reducing unloaded Q, is just nuts.

I have explained why EMDrive cavity Q must be measured via unloaded via S11 return loss and how it is done. I also explained using a 2 port S21 can measure Q but it is not unloaded Q as the 2nd port sample probe increases cavity losses and reduces the unloaded cavity Q.

But hey do it your way as all these arm chair experts who have never built an EMDrive and got it to produce Force know better than Shawyer, Prof Yang, Eagleworks, Prof Tajmar's & Prof Tajmar's uW expert prof.
« Last Edit: 08/08/2015 03:24 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline SteveD

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The testiness of this current discussion aside, I am genuinely interested in the reason why there is a difference between these two Q value viewpoints.

As far as I can gather, @TT is saying, "How they did it". @rfmwguy is saying "How it should've been done." and @tleach is saying "This is how it seems to fit McCulloch's formula."

Which BTW, McCulloch doesn't define how to measure Q. He simply redefines it as the number of bounces (reflections), in the time it takes the photon to decay to zero. So that's not even the same definition of the Q that is being kicked around here. @tleach was trying to bridge that gap.

What I conclude is, the experimenters may or may not be measuring it consistently using the same methodology, but in all cases, they are doing it wrong and should be using 2 ports to measure cavity resonance. We have yet to see anyone do it this way.
Todd

Can we simply agree to some notation to indicate which measurement scheme for Q we are talking about.  I'm sure there is a definitive answer for how to measure Q, but I get the feeling that deriving it involves complex math and probably deserves a paper of its own.  Can we simply agree on some way to easily notate which measuring scheme a poster is using and agree to disagree which is correct pending further data?

I mean hell, with the falloff in power requirements that TT was going on about on Reddit I'm not at all sure that the Q of the device isn't increasing the longer it is active.  (Which reminds me, has anybody pointed a geiger counter at one of these things to make sure it isn't throwing off unexpected radiation).

Offline TheTraveller

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True for my totally open EMDrive work as well.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline WarpTech

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Jose,

In Zeng & Fan they define the complex wave number propagating toward the small end as;

k = j*α - β, where j is the imaginary coordinate.

Momentum is directly proportional to k. So the squared magnitude of the momentum vector is proportional to;

k2 = α2 +  β2

Now, take a gander at the plots for attenuation and phase constant in Zeng & Fan. Which mode and cone half-angle do you think will have the highest momentum?

For TE modes, as β goes to 0, the wave is 100% attenuated at the small end. They refer to this as the cut-off. 

Wouldn't you agree, that the waves have the highest momentum when the cone angle is smallest and k*r is the largest?

Also, if the attenuation, α is asymmetrical, would the equation above not (rather simply) explain beyond doubt why momentum transfer is also asymmetrical?

@TheTraveler likes to use Guide wavelength, rather than phase velocity. So be it. The guide wavelength is the inverse;

λguide = 2*pi/β

Per Z&F, as α increases, β goes to 0, the guide wavelength will become infinitely long and momentum of the wave goes to zero. It is 100% attenuated and absorbed at the front end.

Going the other way, toward the big end, β is increasing and α is decreasing rapidly. The momentum of the wave is increasing.

In both directions, the force on the frustum which balances the change in momentum is "forward". It is only the reflection at the big end that opposes this force. Anything that can be done to minimize the "z" component of this reflection, will add to the thrust.
Todd




Offline TheTraveller

SPR has declined my license request.

Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.

Oh well at least I tried to do the right thing.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline demofsky

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SPR has declined my license request.

Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.

Oh well at least I tried to do the right thing.

As a practical matter will this affect you much?  Just trying to understand the implications of this.  Thanks!

Offline TheTraveller

SPR has declined my license request.

Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.

Oh well at least I tried to do the right thing.

As a practical matter will this affect you much?  Just trying to understand the implications of this.  Thanks!

Should have very little effect.

Was just trying to do the right thing by Shawyer / SPR and not be called out for ripping off the IP.

Told Shawyer I'll still give him / SPR 25% of any gross profit made.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline tleach

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SPR has declined my license request.

Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.

Oh well at least I tried to do the right thing.

As a practical matter will this affect you much?  Just trying to understand the implications of this.  Thanks!

Should have very little effect.

Was just trying to do the right thing by Shawyer / SPR and not be called out for ripping off the IP.

Told Shawyer I'll still give him / SPR 25% of any gross profit made.

So they'll still allow you manufacture in China/Australia and import the components?  That's good at least.  Bummer they won't let you give Shawyer some (financial) credit though...

EDIT: Oops!  Yeah, looks like you're going to give him 25%.  Sorry, it's getting late.  I misread that last line.
« Last Edit: 08/08/2015 06:58 am by tleach »
T. Thor Leach

Offline zen-in

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SPR has declined my license request.

Too much red tape with using Chinese frustum fabricators and my Australian company would need to be approved by both UK and Australian Depts of Defense.

Oh well at least I tried to do the right thing.

As a practical matter will this affect you much?  Just trying to understand the implications of this.  Thanks!

Should have very little effect.

Was just trying to do the right thing by Shawyer / SPR and not be called out for ripping off the IP.

Told Shawyer I'll still give him / SPR 25% of any gross profit made.

There is nothing to stop you from experimenting since you do believe in it.   That would be a better way to start anyway.

Offline flux_capacitor

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Wouldn't you agree, that the waves have the highest momentum when the cone angle is smallest and k*r is the largest?

Did you change your mind about k*r? In previous thread you implied the opposite, that it had to be the lowest possible in order to increase thrust.

It is only the reflection at the big end that opposes this force. Anything that can be done to minimize the "z" component of this reflection, will add to the thrust.
Todd

Anything decreasing the reflection at the big end would also dramatically decrease the Q of the cavity. Do you think about a particular method? EDIT: slotting maybe ;)
« Last Edit: 08/08/2015 07:39 am by flux_capacitor »

Offline Star One

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http://www.ustream.tv/channel/em-drive-experiment

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When you do the real thing are you going to publicise more widely?

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