Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1875121 times)

Offline TheTraveller

Two errors there. First, momentum is conserved at all times in all sensible reference frames for a system comprising a photon bouncing between two mirrors. There is no "borrowing from The Cosmic Badger" going on. Secondly, please don't try and use "the reference frame of a photon", accelerated or otherwise. It's a semantic null statement to put things in that frame of reference. It's also another of Shawyer's conceptual errors.

Just to be clear about errors.

Do you believe that Shawyer and the Chinese have made errors in measured thrust in their test devices and there is really no thrust?
I can understand your curiosity about what all the other pollsters believe, when you yourself are the sole occupant of one of the offered categories.

So why avoid answering my question? Btw I'm not the sole occupant.
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Online kdhilliard

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Some people are comfortable with minor violations of Conservation of Momentum or Conservation of Energy as long as it doesn't occur in such as way as to allow for Perpetual Motion Devices or Free Energy Machines.  I feel that it is worth a few words to address Shawyer's attempt at Conservation of Energy.

Shawyer's FAQ #18:
Quote
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.

Without this decrease in specific thrust the situation is obvious.  Were you to install a 30 kN/kW EmDrive on an airplane and use it to accelerate the plane to its cruising speed of 100 m/s, it would then be doing 3 MW of mechanical work for every 1 kW of power it consumes.  Shawyer addresses this by limiting the specific thrust to the reciprocal of the velocity, T/P < 1/v.  This means that the work is restricted to be less than the power consumed, T v < P.

Nowhere in his Theory Paper does he explicitly state T/P < 1/v, but that is what you get by taking equation (16), combining it with his definition of thrust, and taking the limit on Q.  He also gives an example on pg. 8-9 where an EmDrive which has accelerated to 3 km/s is limited to a specific thrust of 333 mN/kW.  (Note that 333 mN/kW = 0.333 (kg m / s^2) / (10^3 kg m^2 / s^3) = 1 / (3 km/s) = 1/v.)

However this is not an emergent property of his theory, but is instead explicitly added on pg. 7-8 where he declares that the output power from the device which is transferred into the device's kinetic energy is equal to the change of the kinetic energy of the device (as measured in the reference frame from which the drive first started accelerating from v=0), and thus P_k = M v a = v T.  With total power equal to the sum P_k and the electrical losses P_e, we automatically have P < v T.

But just declaring that energy is conserved because it was constructed that way (in one reference frame) is not sufficient.  Conservation of energy is supposed to be invariant across inertial reference frames.  If momentum is conserved, then if energy is conserved in any one inertial reference frame it is conserved in all inertial reference frames.  But momentum is not conserved here, so even though CoE is declared to hold in one reference frame it will be violated in others.

Consider a 3 kN/kW EmDrive constructed and energized for the first time all while flying in an airplane traveling at its steady cruise velocity of 100 m/s (194 kts).  As far as the drive is concerned, it is at much at rest as its counterpart which was constructed and and first energized in a ground-based laboratory, but when energized the airborne drive will be doing 3 MW or work for every 1 kW of power it consumes, and this is work which could be harvested via air turbines extended from the plane.


Question:  Do other theories for these sorts of drives include this reduction in specific thrust as a function of velocity obtained via acceleration of the drive along the thrust vector?  Dr. Rodal, for the feature article you reported on Dr. Whites simulation, "The computer code also shows that the efficiency, as measured by the thrust to input power ratio, decreases at input powers exceeding 50 kiloWatts."  I assume that his theory would be properly invariant and not suffer reduction of specific thrust as a function of velocity.

~Kirk

Offline WarpTech

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[...]


I also feel doing a frequency sweep to look for resonance mush be done slowly as it takes time for a high Q frustum to react to the external Rf and fully fill the cavity. Sweep too fast and you may miss the high Q sweet spots.

The sweep must excite the cavity in TM mode. Putting a stub antenna through the frustum side wall will not, as far as I understand the process, excite TM mode. It will just excite TE mode. It seems you need to put the probe in the middle of one end to excite TM mode. But I'm not yet a microwave engineer, so there may be other ways to excite TM mode.

Any comments on how to excite TM mode, in a frustum, with a coax feed would be most welcome.

You are correct, to excite TM01 modes you should insert your stub-antenna in the middle of one end, preferably the small end. Then do a slow sweep like you said, to fine tune the resonant frequency. IMO, it probably doesn't matter if the stub antenna extended all the way through the axis of the frustum and attached to the big end, because that end should be a Null in the p-mode, TM01p anyway.

I'm currently working on analyzing this design, without the connection. So far, what I know is the capacitance is maximized at the small end, and the inductance is maximized at the big end. The magnetic Lorentz force, qv x B is not symmetrical between the walls and the antenna, because B is zero on the axis of the antenna, due to the symmetry of the frustum. However, calculating qE between them is more difficult, since relative phase is critical to the direction of the NET force.  It appears to work like a current transformer with a DC offset, due to an unbalanced resistive load on each half-cycle. Eventually it equalizes, but it can be pulsed to gain thrust as it decays.

Todd

Offline Rodal

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...Dr. Rodal, for the feature article you reported on Dr. Whites simulation, "The computer code also shows that the efficiency, as measured by the thrust to input power ratio, decreases at input powers exceeding 50 kiloWatts."  I assume that his theory would be properly invariant and not suffer reduction of specific thrust as a function of velocity.

~Kirk
I would not assume that, as any such assumption, as you so eloquently showed above for Shawyer's formulation is done at the peril of the person doing the assuming.

Dr. White's comments are paraphrased from his papers in a number of AIAA publications, WarpTech and DeltaMass and Frobnicat (for the longest time), among others, have discussed this. A valiant attempt was made by the person working on the EM Drive wiki, to condense the discussion on energy conservation and its attendant paradox:  http://emdrive.echothis.com/Generic_EM_Drive_Information

« Last Edit: 05/24/2015 04:40 PM by Rodal »

Offline Rodal

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...You are correct, to excite TM01 modes you should insert your stub-antenna in the middle of one end, preferably the small end. Then do a slow sweep like you said, to fine tune the resonant frequency. IMO, it probably doesn't matter if the stub antenna extended all the way through the axis of the frustum and attached to the big end, because that end should be a Null in the p-mode, TM01p anyway. ...
Todd, given the excitation frequencies and geometrical dimensions of the EM Drives being considered I presume you are discussing exciting some high mode TM01p with a higher p greater than 0.

Such a (high p) mode will be very difficult to single out and excite by itself because they lie next to several other modes having m>0 that have a variation of the electromagnetic field in the azimuthal variation.

Recall the experience of NASA Eagleworks that had issues of exciting TE012 (which initially gave a high thrust/InputPower) and had to stay with TM212, now for practically a year.
« Last Edit: 05/24/2015 04:43 PM by Rodal »

Offline phaseshift

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Streamed live on Apr 25, 2013
Special guest theorists Lisa Randall from Harvard University and Raman Sundrum from University of Maryland, who join CERN physicists to look at how the LHC experiments are investigating extra dimensions.

Great video.  It touches on so many topics that get discussed here on this forum.
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Offline Rodal

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Quote
Note: Shawyer's analogy to a rocket is non-viable because a rocket has variable mass , it is the propellant exiting the rocket (like a bullet exiting a gun results in the gun's recoil force), the variable mass of the rocket, that is responsible for a rocket's acceleration.  The EM Drive is a closed cavity and is described by Shawyer as propellant-less with nothing exiting the EM Drive.

Alternatively, a rocket throws momentum out of its back end. Perhaps this is what Shawyer means when he talks about thrust. If the net force from the microwaves on the cavity is towards the small end, then the cavity must accelerate towards the small end. However being in violation of CoM there must be momentum ejected in the opposite direction, ergo Shawyers thrust. This would then act as a pushing force in the opposite direction. Quite what the ejected momentum consists of is perhaps another matter.

Since the year 1900 by Lebedev (see:  http://web.ihep.su/dbserv/compas/src/lebedev01/eng.pdf ), experiments have been conducted, confirming that Maxwell was correct that the radiation pressure of photons against a surface push the surface in the same direction as the force, such that positive work is performed. 

This (Maxwell's theory and the experiments that have verified it)  is in sharp contrast with Shawyer's theory claiming that the Thrust pressure of photons towards the Big Diameter results in motion of the EM Drive in the opposite direction, towards the Small Diameter.  (This results, as I have shown, in the curious behavior that the Work being done is negative, according to Shawyer's theory)
« Last Edit: 05/24/2015 04:57 PM by Rodal »

Offline TheTraveller

Quote from: WarpTech
You are correct, to excite TM01 modes you should insert your stub-antenna in the middle of one end, preferably the small end. Then do a slow sweep like you said, to fine tune the resonant frequency. IMO, it probably doesn't matter if the stub antenna extended all the way through the axis of the frustum and attached to the big end, because that end should be a Null in the p-mode, TM01p anyway.

As per the attachment as well. Can't excite TM mode in a resonate cylinderical cavity via side wall mounted antenna.

Question: Did EWs test a non dielectric frustum, excited in TM mode via an antenna inserted in the middle of either end?
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Offline SeeShells

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Streamed live on Apr 25, 2013
Special guest theorists Lisa Randall from Harvard University and Raman Sundrum from University of Maryland, who join CERN physicists to look at how the LHC experiments are investigating extra dimensions.
I thoroughly enjoyed this, Thanks Dr. Rodal!!! 

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You know, we have a fan club now; where the million views came from. People who are counting on us to do the right thing, every time; without question. We're at the forefront. No different than those before us who dared to go against the grain. If we are selfless, and put good science on the table...maybe things will progress.

https://www.reddit.com/r/EmDrive/

History will judge us someday.

This is step one. Our first real chance to get it right. If we fail......
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Offline TheTraveller

Interesting.

Chinese theory claims thrust directs to the small / minor end plate and the H field force is many times greater than the E field force on the end plates.

Thus they excite their frustum in TE011 mode.

Would appreciate the theory guys doing as much due diligence on the attached Chinese paper as has been done on Shawyers papers.
« Last Edit: 05/24/2015 05:56 PM by TheTraveller »
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Offline apoc2021

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The one "force" that ignored all this mix of neatly assembled pieces and parts and the fundamental forces had to play its game was and is space time.
...
By invoking a field of electromagnetic harmonics (TM212 or one like it) that creates a bubble, a null, a void, a hollowed out area within the EM cavity do we start to see a manipulation of space time and space time can violate CoE and CoM like it did in the beginning with the great expansion.
...
Wonderfully the one explanation that is left and it's likely to be the one... spacetime.

Shell, thank you for this comment - this is an elegant view, and it reminds me of Einstein79's comments in thread 2. The sense I have gotten is that we aren't thinking big enough, as everything is always in motion including space itself even when we are at an apparent standstill. This IMHO causes our conventional concepts such as thrust and acceleration to fall short of requirements needed to explain what we are observing.

In the end I think we'll have come to realize that creating EM fields in a particular way alters spacetime in a particular way. For example the low power tests at EW compress spacetime ever so slightly and for us the observable effect most closely resembles thrust. Perhaps once refined the distances become arbitrary.

I think this is what EW was getting at - EM drive thrust, "warp drive"... Simply variations on a theme.

Offline phaseshift

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After going back and forth on the presence of rubber o-rings I've decided that they are needed for pressurization of the cavity and keeping two dissimilar metals apart for terrestrial applications might be important as well.  I looked at adding a choke ditch with an o-ring and decided that wasn't necessary with the wavelengths we are working with - though the guys building the 25GHz version might need this.

So in my construction I'm shortening the cone length by 2x the thickness of the o-ring. With screws applying 1000 lbs/inch the rubber will compress so I'm looking for equations on the amount of compression that will occur and compensate accordingly.

I'm not a waveguide engineer - and as TheTraveler likes to say 'yet' - so this is based on what I have read so far - if anyone can point me to other references to refine the design I would be delighted.
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Offline Rodal

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Interesting.

Chinese theory claims thrust directs to the small / minor end plate and the H field force is many times greater than the E field force on the end plates.

Thus they excite their frustum in TE011 mode.

Would appreciate the theory guys doing as much due diligence on the attached Chinese paper as has been done on Shawyers papers.
1) Please note that the screenshot you quoted deals entirely (100%) with their numerical predictions and it has no comparison whatsoever (in that screenshot) to experimental measurements.  Please let us know if you see a comparison of their theoretical predictions to their actual experimental measurements (I haven't read those papers in a long time and I don't recall)

2) Please note that the Finite Element software package they are using (which now belongs to ANSYS) is entirely based on the solution to the linear Maxwell differential equations and it is based entirely on the same numerical formulation used by COMSOL FEA and also the same equations that I solved exactly with my exact solution that you were previously criticizing.  Prof. Yang's predictions for the TEmnp and TMmnp modes are entirely based on standing waves.  They are not at all based on waveguides as you previously thought.  Prof. Yang's prediction of thrust is entirely uncoupled from her TEmnp and TMmnp mode predictions.

3) Notice that Prof. Yang, unlike Shawyer, refers to cavity modes (TEmnp and TMmnp) instead of open waveguide modes TMmn.

4) As Prof. Yang details in her paper, her "thrust" prediction is made a posteriori based on the numerical solution of Maxwell's equations as standing waves.  She performs an a posteriori calculation of the FEM classical solution, ignoring the pressure on the side walls.
« Last Edit: 05/24/2015 06:24 PM by Rodal »

Online Mulletron

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Interesting.

Chinese theory claims thrust directs to the small / minor end plate and the H field force is many times greater than the E field force on the end plates.

Thus they excite their frustum in TE011 mode.

Would appreciate the theory guys doing as much due diligence on the attached Chinese paper as has been done on Shawyers papers.

Would appreciate a look at this lecture chap 7.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

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...Great video.  It touches on so many topics that get discussed here on this forum.

...I thoroughly enjoyed this, Thanks Dr. Rodal!!!
As PhaseShift said it is interesting how this video deals with a number of topics we have been discussing.  For example, the question is asked (by somebody at CERN) to Sundrum as to whether there is a relation of the extra dimension(s) to the Quantum Vacuum virtual particles.  The answer is that this is unknown.  They are using Heisenberg's uncertainty principle as a given.  Sundrum emphasizes the fact that we can borrow much larger amounts of energy than we own (no need of collateral) but that you have to pay it back in an extremely small amount of time.  They are using this ability to borrow larger energy from the QV in their experiments to explore energy being lost in the extra dimension(s). Thus, the issue with Dr. White's proposal is the need to payback, in a very small amount of time, any energy you may borrow (the QV being immutable and non-degradable over longer periods of time).  Essentially, Dr. White's proposal is that one can default on the mortgage  :)
« Last Edit: 05/24/2015 06:38 PM by Rodal »

Offline TheTraveller

Quote from: Rodal
----

Her conclusion and final paper attached.
« Last Edit: 05/24/2015 06:24 PM by TheTraveller »
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Offline TheTraveller

Quote from: Rodal
----

Her conclusion and final paper attached.

Very interesting.  Thus we see here that Prof. Yang, far from imitating Shawyer, states a completely different conclusion: that the "measured net EM thrust" is directed towards the small end (towards the "minor end plate"), (the complete opposite of what Shawyer states).  She also states that this thrust direction (towards the small end) agrees with her theoretical prediction of thrust direction.

AND her theory predicts the thrust level per power input.  All without needing new  physics.
« Last Edit: 05/24/2015 06:35 PM by TheTraveller »
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Offline deltaMass

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Quote from: Rodal
----

Her conclusion and final paper attached.

Very interesting.  Thus we see here that Prof. Yang, far from imitating Shawyer, states a completely different conclusion: that the "measured net EM thrust" is directed towards the small end (towards the "minor end plate"), (the complete opposite of what Shawyer states).  She also states that this thrust direction (towards the small end) agrees with her theoretical prediction of thrust direction.
When you say "toward the small end plate", do you mean from the outside or the inside? That's the ambiguity with using that sort of nomenclature.

Once again, I recommend using "small end forward" etc. as the least ambiguous designator of the direction of the resultant thrust vector - the one which produces acceleration.

Offline phaseshift

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...Great video.  It touches on so many topics that get discussed here on this forum.

...I thoroughly enjoyed this, Thanks Dr. Rodal!!!
As PhaseShift said it is interesting how this video deals with a number of topics we have been discussing.  For example, the question is asked (by somebody at CERN) to Sundrum as to whether there is a relation of the extra dimension(s) to the Quantum Vacuum virtual particles.  The answer is that this is unknown.  They are using Heisenberg's uncertainty principle as a given.  Sundrum emphasizes the fact that we can borrow much larger amounts of energy than we own (no need of collateral) but that you have to pay it back in an extremely small amount of time.  They are using this ability to borrow larger energy from the QV in their experiments to explore energy being lost in the extra dimension(s). Thus, the issue with Dr. White's proposal is the need to payback, in a very small amount of time, any energy you may borrow (the QV being immutable and non-degradable over longer periods of time).  Essentially, Dr. White's proposal is that one can default on the mortgage  :)

As I understand it the amount of time that a virtual particle can exist is inversely proportional to the energy borrowed. Thus low debt particles have more time to travel than large debt particles.  So around whole quanta particles there is a fuzzy cloud of 'particles'/'waves' - low debt particles are farther away then high debt particles.  This can be and has been measured - we do interact with the virtual quantum vacuum.
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