Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1804098 times)

Offline WarpTech

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I think I just proved my hypothesis, with an open ended cone anyway....

Excellent!  Does this require the duty cycle like that seen in magnetrons?  Would increasing the duty cycle increase thrust?  Thanks!

Sorry, I'm not ready to think about design parameters yet, but at least I balanced the rocket equation! :)
Todd

Offline dustinthewind

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I think I just proved my hypothesis, with an open ended cone anyway. Very simply put, the cone shape has an inductance gradient that acts as a particle accelerator. A constant DC Current flowing around the cone perimeter at the big end will feel a force toward the small end. The current will "fall" in that direction, losing energy (and mass) in the process. At the same time, an equal and opposite force is acting on the magnetic flux contained in the current loop, pushing the flux out the back of the cone.
Write up soon!
Todd

This is the same thing I was thinking would happen with the dual resonating cylinders in TE01 (circular currents on the plates) [tuned to resonate at same freq and one can adjust freq. a bit to cause phase shift momentarily].  Both cylinders appear to be pushed by time retarded magnetism like an antenna array which focuses radiation in a direction.  The radiation as a result travels in the opposite direction of the force.  I think there should be the appearance of modes moving from one cylinder to the next and possibly passing outside also.  The big question being if the traveling modes canceled out the currents force.   

One question that comes to mind is that the modes appear to be traveling towards the narrow end in the images provided by "aero"

https://drive.google.com/folderview?id=0B1XizxEfB23tfjVmb1RiZXpaajd6WGpGQmpSWDkxRlV3cG10TEJmWVVEbTd2U0t4MC1aa1E&usp=sharing

Dr. Rodal, this is the same link as before so I hope it will give you access to the new x slices data set. The cavity sliced 276 times across the axis of rotation. Only thing I see is that the influence of the antenna diminishes markedly toward the upper half of the cavity. That and it seems very little energy actually reaches the small end. That may be simply an artefact of the time slice I chose.

but it sounds like your stating that they are moving towards the big end.  Maybe it had to do with his antenna placement though. 

The other question would be if you get any large (greater than photons) force from it or not? 
« Last Edit: 06/24/2015 06:57 AM by dustinthewind »

Offline CW

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(...)

Everything vibrates, well maybe a bose condensate chilled just a bit above absolute 0c doesn't.  So as a motor where does it get the EMF to push against being a closed box that nothing (Shawyer said so) escapes? The internal QV of the device?

Honestly the generator and motor explanation goes against everything that makes sense even quantum theory make more sense to me.   



Shell

So it seems to boil down to this: If it is moved, it moves. If it isn't moved, it doesn't move. What an insight! Others call it inertia. Even if we assumed that the QV somehow imparted microscopic vibrations.. since all QV vibrations time-average to Zero, the device would spend half the time in 'generator mode' and half the time in 'propulsion mode'. Nothing gained from it. Whatever Mr. Shawyer came up with to explain movement or acceleration, doesn't make any logical sense. I'm more than willing to look at experimental data that shows signals well above SNR. But I'm not willing to throw logic out of the window just for argument's sake.
Reality is weirder than fiction

Offline WarpTech

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Just needs some vibration.

The EMDrive is an inertial ratchet. Push it on the small end and it will oppose that push, moving into Generator mode. Push it on the big end and it will support that push, moving into Motor mode.

It may be that EW cooked its own goose then they worked so hard to eliminate vibration, without which the EMDrive will just sit there and get hot.

Ha! I've been trying to keep my nose out of this controversy, but I just figured out what's going on. It's like a spinning bicycle wheel. It will just sit there and do nothing until you try to tip it one way or the other, and then the torque acts to rotate it in one direction and oppose rotation it in the other direction.  It doesn't exert any thrust due to the microwaves because Maxwell's equations say it can't. But it does store energy and that energy will have a back-reaction when you push it, which will be just as asymmetrical as the cavity attenuation.
Todd

Offline TheTraveller

Just needs some vibration.

The EMDrive is an inertial ratchet. Push it on the small end and it will oppose that push, moving into Generator mode. Push it on the big end and it will support that push, moving into Motor mode.

It may be that EW cooked its own goose then they worked so hard to eliminate vibration, without which the EMDrive will just sit there and get hot.

Ha! I've been trying to keep my nose out of this controversy, but I just figured out what's going on. It's like a spinning bicycle wheel. It will just sit there and do nothing until you try to tip it one way or the other, and then the torque acts to rotate it in one direction and oppose rotation it in the other direction.  It doesn't exert any thrust due to the microwaves because Maxwell's equations say it can't. But it does store energy and that energy will have a back-reaction when you push it, which will be just as asymmetrical as the cavity attenuation.
Todd

Well done. I'll accept that.

Like your bike wheel example, once you flip it into Motor or Generator mode, it will stay there as long as there is an external force, which can be just simple vibration.

If you look at this slide, Shawyer clearly shows the momentum generates no external Force.
« Last Edit: 06/24/2015 07:21 AM by TheTraveller »
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Offline A_M_Swallow

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If the drive is moved whilst a radio photon is travelling down the cone the distance and time taken to get to the end will change. The Δh and Δt are tiny but may not be zero.

Offline TheTraveller


(...)

Everything vibrates, well maybe a bose condensate chilled just a bit above absolute 0c doesn't.  So as a motor where does it get the EMF to push against being a closed box that nothing (Shawyer said so) escapes? The internal QV of the device?

Honestly the generator and motor explanation goes against everything that makes sense even quantum theory make more sense to me.   



Shell

So it seems to boil down to this: If it is moved, it moves. If it isn't moved, it doesn't move. What an insight! Others call it inertia. Even if we assumed that the QV somehow imparted microscopic vibrations.. since all QV vibrations time-average to Zero, the device would spend half the time in 'generator mode' and half the time in 'propulsion mode'. Nothing gained from it. Whatever Mr. Shawyer came up with to explain movement or acceleration, doesn't make any logical sense. I'm more than willing to look at experimental data that shows signals well above SNR. But I'm not willing to throw logic out of the window just for argument's sake.

Sorry not about linear inertia but about an inertial ratchet like effect.

Is about the shift in the waves inside the cavity and what happens to them then they do and no not experience an external force being +ve or -ve or nothing as per the attached.

Have attached the referenced presentation.

When placed into Generator mode, it will resist being moved small end to big end and when placed in Motor mode will support being moved big end to small end. In both movement cases, the EMDrive generates a Force which either acts to resist movement (Generator mode) or causes acceleration (Motor mode).
« Last Edit: 06/24/2015 07:40 AM by TheTraveller »
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Offline pogsquog

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Here's my understanding, if it helps to clarify anything:

Consider a vertical tube with mirrors on each end, and light bouncing between them, under the influence of acceleration i.e. the Earth's gravitational field. The light will gain energy while moving down, hitting the bottom of the tube with more momentum, and will lose energy while moving up, hitting the top of the tube with less momentum. This can happen repeatedly, due to the mirrors. One might imagine therefore that there will be a net force pushing in the direction of acceleration force i.e. down.  (I'd be interested to know what the flaw in this reasoning is, at it would appear to allow an EM drive like functionality fairly straightforwardly in the presence of a strong gravitational well.)

If we now consider the tube not in a gravitational well, but rather experiencing acceleration from an external force, then the same thing will happen. The  problem is that the net force will oppose the acceleration (i.e. it will add to the inertia).

For the EM drive to be working as Shawyer suggests, the net force is in some way arranged to be asymetric, such that the drive opposes acceleration in one direction, and enhances it in the other (which in turn gives rise to more acceleration).

Offline OttO

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I am not a Shawyer fan but the Traveller defense could be not so crazy, look at the following paper:

Motion induced radiation from a vibrating cavity
http://arxiv.org/abs/quant-ph/9606029

We study the radiation emitted by a cavity moving in vacuum. We give a quantitative estimate of the photon production inside the cavity as well as of the photon flux radiated from the cavity. A resonance enhancement occurs not only when the cavity length is modulated but also for a global oscillation of the cavity. For a high finesse cavity the emitted radiation surpasses radiation from a single mirror by orders of magnitude.
« Last Edit: 06/24/2015 08:52 AM by OttO »

Offline frobnicat

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Here's my understanding, if it helps to clarify anything:

Consider a vertical tube with mirrors on each end, and light bouncing between them, under the influence of acceleration i.e. the Earth's gravitational field. The light will gain energy while moving down, hitting the bottom of the tube with more momentum, and will lose energy while moving up, hitting the top of the tube with less momentum. This can happen repeatedly, due to the mirrors. One might imagine therefore that there will be a net force pushing in the direction of acceleration force i.e. down.  (I'd be interested to know what the flaw in this reasoning is, at it would appear to allow an EM drive like functionality fairly straightforwardly in the presence of a strong gravitational well.)

If we now consider the tube not in a gravitational well, but rather experiencing acceleration from an external force, then the same thing will happen. The  problem is that the net force will oppose the acceleration (i.e. it will add to the inertia).

For the EM drive to be working as Shawyer suggests, the net force is in some way arranged to be asymetric, such that the drive opposes acceleration in one direction, and enhances it in the other (which in turn gives rise to more acceleration).

Emphasized statement : classically this added inertia term is exactly the mass equivalent of the bound energy content (em wave bouncing inside cavity). Taking 1kW at Q=10000 for 2.45GHz yields 4mJ (milli-Joule), (I recall other way to calculate push that up to 1J ??) equivalently about 4.5*10^-20 kg ... this is so minuscule as to make no possible measurable difference on anything. For reasonable accelerations (compatible with a rigid body) this will be a much weaker effect than any asymmetry in exhaust photon thrust from waste IR alone. And even if it did a difference, this apparent added mass to the inertia is in fact exactly the same that was lost by the battery operating the system in the first place : taken as a whole, a spacecraft system with battery + frustum will see no change at all in apparent inertia, this is just a transfer of mass_energy from battery to frustum, this will change the x position of the hull (for a vanishingly small amount) as to conserve centre of mass overall, but will not yield any deltaV at all (until some of the energy_mass is radiated away as waste heat, at photon rocket thrust yield at best).

Offline cej

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If we now consider the tube not in a gravitational well, but rather experiencing acceleration from an external force, then the same thing will happen. The  problem is that the net force will oppose the acceleration (i.e. it will add to the inertia).

Emphasized statement : classically this added inertia term is exactly the mass equivalent of the bound energy content (em wave bouncing inside cavity). Taking 1kW at Q=10000 for 2.45GHz yields 4mJ (milli-Joule), (I recall other way to calculate push that up to 1J ??) equivalently about 4.5*10^-20 kg ... this is so minuscule as to make no possible measurable difference on anything.

That is for a cylinder, and if there is indeed meaningful resistance to changes in momentum in such a cavity due to photons bouncing between the two endplates, then the EM drive should also resist changes in momentum symmetrically (i.e. it would not prefer moving toward the small end or large end).

But in a frustum, would moving the cavity from the small end toward the large end "squeeze" the standing waves radially, effecting a change in frequency and thus momentum -- and would this change be significant as to resist movement? Whereas, in the other direction, the standing waves would not be squeezed, so there would not be a significant resistance to a change in momentum?

In other words, does accelerating the frustum in one direction change the resonance mode, while accelerating in the other does not? And will the resonance mode significantly resist being changed?
« Last Edit: 06/24/2015 10:27 AM by cej »

Offline Rodal

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I am not a Shawyer fan but the Traveller defense could be not so crazy, look at the following paper:

Motion induced radiation from a vibrating cavity
http://arxiv.org/abs/quant-ph/9606029

We study the radiation emitted by a cavity moving in vacuum. We give a quantitative estimate of the photon production inside the cavity as well as of the photon flux radiated from the cavity. A resonance enhancement occurs not only when the cavity length is modulated but also for a global oscillation of the cavity. For a high finesse cavity the emitted radiation surpasses radiation from a single mirror by orders of magnitude.

In this paper, the speed of the mirror needs to begin to match the the speed of the photons: relativistic speeds.

It’s hard to get an ordinary mirror moving at anything like relativistic speeds.  No EM Drive experienced that kind of vibration.

In experiments to verify what is discussed in the paper, instead of a conventional mirror, they’ve used a transmission line connected to a superconducting quantum interference device (SQUID). The SQUID changes the effective electrical length of the line and this change is equivalent to the movement of an electromagnetic mirror. By modulating the SQUID at GHz rates, the mirror moves back and forth. The transmission line is only 100 micrometres long and the mirror moves over a distance of about a nanometre. But the rate at which it does this means it achieves speeds approaching 5 per cent light speed.

I can't see anything like this happening in the EM Drive, the EM Drive does not experience mechanical vibration in the GHz or MHz range, so I'm afraid that this kind of vibration and effect does not apply to the EM Drive
« Last Edit: 06/24/2015 12:15 PM by Rodal »

Offline Rodal

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...

In other words, does accelerating the frustum in one direction change the resonance mode, while accelerating in the other does not? And will the resonance mode significantly resist being changed?
For that to happen, the mechanical acceleration would have to be huge, since the electromagnetic field frequency is in the GHz range.  But, on the contrary, the reported EM Drive accelerations instead of being huge, it is extremely tiny: in the only EM Drive experiment that experienced significant rigid body motion: Shawyer's Demo on an air bearing, it takes several minutes for the EM Drive to complete a circumference,  Extremely small acceleration.

Offline Notsosureofit

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...

In other words, does accelerating the frustum in one direction change the resonance mode, while accelerating in the other does not? And will the resonance mode significantly resist being changed?
For that to happen, the mechanical acceleration would have to be huge, since the electromagnetic field frequency is in the GHz range.  But, on the contrary, the reported EM Drive accelerations instead of being huge, it is extremely tiny: in the only EM Drive experiment that experienced significant rigid body motion: Shawyer's Demo on an air bearing, it takes several minutes for the EM Drive to complete a circumference,  Extremely small acceleration.

The interesting part is the multiplication factor of a high Q cavity.

Offline Rodal

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...

In other words, does accelerating the frustum in one direction change the resonance mode, while accelerating in the other does not? And will the resonance mode significantly resist being changed?
For that to happen, the mechanical acceleration would have to be huge, since the electromagnetic field frequency is in the GHz range.  But, on the contrary, the reported EM Drive accelerations instead of being huge, it is extremely tiny: in the only EM Drive experiment that experienced significant rigid body motion: Shawyer's Demo on an air bearing, it takes several minutes for the EM Drive to complete a circumference,  Extremely small acceleration.

The interesting part is the multiplication factor of a high Q cavity.
It shows that the finesse of an optical cavity (the equivalent of the Q of an electromagnetic cavity) has a multiplier effect on the number of produced photons.

The other interesting thing is that the number of photons to be expected on the outside of the cavity has a probability proportional to the finesse, in other words the probability of encountering these photons outside the EM Drive is proportional to the Q of the cavity.  So quantum tunneling of photons is at play.

<<Each photon has a probability 4ρ of escaping from the cavity during each roundtrip time 2τ>>

where ρ is the finesse (the equivalent of the Q)

so that the probability of photons escaping from the cavity is 4Q


////////////////


EDIT: I wonder whether Tajmar has done some emission  measurements on the outside of the EM Drive, and that's what he means by side effects in his upcoming talk:

5:00 PM - 5:30 PM
Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects
Martin Tajmar

http://arxiv.org/pdf/1505.02755.pdf

« Last Edit: 06/24/2015 12:56 PM by Rodal »

Offline Rodal

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A warnning on the detrimental effect of vibrations on scales, for people using scales to measure the EM Drive force, (as done for example by Shawyer), on Tajmar's paper:


Quote
we have demonstrated that periodical vibrations, in our case generated
by a spinning body, can significantly influence the readout of the scale, which probably
operates based on an active feedback loop. The majority of electronic scales would fall into
this category, since they use an electromagnetic feedback loop in order to determine the force
necessary to counter the weight of a test mass. This feedback loop has a defined frequency
(which is mostly a trade secret of the production companies) for any specific state. Thus the
interaction of these two frequencies can lead to measurement errors. In case this situation
cannot be avoided in a measurement, we advise that proper precautions should be taken in
order to decouple the vibration sources. Finally we conclude that the reason for the conflicting
reports of the mass measurements of spinning gyroscopes was due to the error sources
presented in this paper.   

http://arxiv.org/ftp/arxiv/papers/1506/1506.02689.pdf

The discussion in the previous pages that "the EM Drive" needs some vibration to operate, makes one wonder about the EM Drive measurements that relied on scales.
« Last Edit: 06/24/2015 12:57 PM by Rodal »

Offline TheTraveller

...

In other words, does accelerating the frustum in one direction change the resonance mode, while accelerating in the other does not? And will the resonance mode significantly resist being changed?
For that to happen, the mechanical acceleration would have to be huge, since the electromagnetic field frequency is in the GHz range.  But, on the contrary, the reported EM Drive accelerations instead of being huge, it is extremely tiny: in the only EM Drive experiment that experienced significant rigid body motion: Shawyer's Demo on an air bearing, it takes several minutes for the EM Drive to complete a circumference,  Extremely small acceleration.

The published video had a 8.2g resistance to rotation centre line of the EMDrive and the EMDrive generating 9.8g of force along the centre line. Effective Force was 1.6g which did a good job spinning the EMDrive.

Have heard with no load, the Demonstrator EMDrive can do a rev in 3 sec on that rig.

The 9.8g Force was generated with 334W. Magnetron can go to 1.2kW.
« Last Edit: 06/24/2015 01:08 PM by TheTraveller »
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Offline Rodal

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...

In other words, does accelerating the frustum in one direction change the resonance mode, while accelerating in the other does not? And will the resonance mode significantly resist being changed?
For that to happen, the mechanical acceleration would have to be huge, since the electromagnetic field frequency is in the GHz range.  But, on the contrary, the reported EM Drive accelerations instead of being huge, it is extremely tiny: in the only EM Drive experiment that experienced significant rigid body motion: Shawyer's Demo on an air bearing, it takes several minutes for the EM Drive to complete a circumference,  Extremely small acceleration.

The published video had a 8.2g resistance to rotation centre line of the EMDrive and the EMDrive generating 9.8g of force along the centre line.

Have heard with no load, the Demonstrator EMDrive can do a rev in 3 sec on that rig.
A rotation in 3 sec in that rig is a huge orders of magnitude smaller than required for a Dynamic Casimir effect.  You need to move at relativistic velocities in order to experience a Dynamic Casimir effect (which is essentially what the paper discusses, that's why the only way to do it  is with a SQUID).
« Last Edit: 06/24/2015 01:01 PM by Rodal »

Offline Fugudaddy

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A warnning on the detrimental effect of vibrations on scales, for people using scales to measure the EM Drive force, (as done for example by Shawyer), on Tajmar's paper:
Quote
we have demonstrated that periodical vibrations...

http://arxiv.org/ftp/arxiv/papers/1506/1506.02689.pdf

The discussion in the previous pages that "the EM Drive" needs some vibration to operate, makes one wonder about the EM Drive measurements that relied on scales.

Which is why the purely mechanical scales that Rfm and Shells are proposing are a much better mechanism for this sort of thing, at least in so far as to answer the basic question: does the EMDrive actually do something?

And there are no RF interference issues with a chunk of wood. ;)

Offline TheTraveller

A warnning on the detrimental effect of vibrations on scales, for people using scales to measure the EM Drive force, (as done for example by Shawyer), on Tajmar's paper:


Quote
we have demonstrated that periodical vibrations, in our case generated
by a spinning body, can significantly influence the readout of the scale, which probably
operates based on an active feedback loop. The majority of electronic scales would fall into
this category, since they use an electromagnetic feedback loop in order to determine the force
necessary to counter the weight of a test mass. This feedback loop has a defined frequency
(which is mostly a trade secret of the production companies) for any specific state. Thus the
interaction of these two frequencies can lead to measurement errors. In case this situation
cannot be avoided in a measurement, we advise that proper precautions should be taken in
order to decouple the vibration sources. Finally we conclude that the reason for the conflicting
reports of the mass measurements of spinning gyroscopes was due to the error sources
presented in this paper.   

http://arxiv.org/ftp/arxiv/papers/1506/1506.02689.pdf

The discussion in the previous pages that "the EM Drive" needs some vibration to operate, makes one wonder about the EM Drive measurements that relied on scales.

Eh?

There is always vibration until a lot of effort is spent to eliminate it but then as Shawyer says in the Force Measurement document, the end result for the vibration elimination is the EMDrive Force goes to zero.

"A number of methods have been used in the UK, the US and China to measure the
forces produced by an EmDrive thruster. In each successful case, the EmDrive force
data has been superimposed on an increasing or decreasing background force,
generated by the test equipment itself.


Indeed, in the UK when the background force changes were eliminated, in an effort
to improve force measurement resolution, no EmDrive force was measured.
This
was clearly a result of attempting to measure the forces on a fully static thruster,
where T and R cancel each other.

UK flight thruster measurements employ this principle to calibrate the background
noise on the force balance prior to carrying out force measurements."

Shawyer uses scales in 4 ways:
http://emdrive.wiki/Useful_EMDrive_Design_and_Test_Tools

Just maybe EWs efforts to eliminate vibration for their Warp Interferometer tests may have doomed them to very low or nothing EMDrive Force measurements.
« Last Edit: 06/24/2015 01:19 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

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