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#2020 by WarpTech on 26 Oct, 2016 01:49
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...Thanks Jose, but I do not think he or I meant to imply that the mode shapes were due to absorption. Only that the energy lost will be asymmetrical. Greg Eagan's derivation does not take into consideration sources or sinks, both of which contribute to a divergence of decay time and energy (Volt-sec), that is not present in his derivation. He assumes all waves to be time symmetric and therefore average to zero, but that is not necessarily true when there are sources and sinks. Isn't that true?
Greg Egan solved the eigenvalue problem under well-stated assumptions.
Whenever Monomorphic or X_Ray have shown a FEKO solution, or Paul March or Samsonov (RFPlumber) have shown a COMSOL solution, they have solved the eigenvalue problem too, just like Egan, but done it numerically, instead of analytically.
All those solutions compare very well with experiments, concerning eigenmodes and eigenfrequencies.
The difference is that those solutions (COMSOL, FEKO, Egan) cannot calculate any thrust, since Maxwell's equations will show no thrust for a closed cavity, acting as a closed system. Even if you allow for dissipation of heat and release of heat into space as heat radiation one can readily show that the thrust would be less than that of a perfectly collimated photon rocket, and hence much less than what is claimed for the EM Drive.
Aren't you justifying the EM Drive thrust as due to a polarized quantum vacuum theory?
(not due to heat dissipation and heat radiating into Space)?
That is correct. However, like GR, we cannot measure the curvature of the space-time manifold without measuring how it affects test particles of matter and light waves. The same is true in the PV Model, we cannot directly measure the refractive index, we can only measure its effects. It turns out that the effects of gravity on matter may be modeled identically to those of a gradient in the damping factor applied to the "underdamped oscillators" of matter.
Can we agree that if the frustum has no RF leaks, then the only way for the energy input to escape is through the material as heat conduction?
Can we also agree that once the energy has been converted into heat, it is no longer resonant "inside" the cavity?
Can we also agree that if the frustum were a "perfect conductor" the time constant for the energy stored would be infinite and there would be no heat generated?
Anything less than perfect has a finite decay time, so can we agree that this decay time is not necessarily uniform on every surface of the frustum?
If we can agree on these points, then we agree that there can be a gradient in the damping factor that mimics the potential gradient of a gravitational field.
Thank you.
Todd
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#2021 by SeeShells on 26 Oct, 2016 02:01
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Seems almost too simple, I like it. I was awake last night and couldn't stop thinking a demonstration is all around us all the time. Much like gravity was exploited by mankind long before Newtons explanation. Still I would expect cylindrical cavities with varying endplates have been studied extensively.
A poor example off the top of my head, a common laser has partially silvered mirror at one end. Optical wavelengths reflected power are controlled with a "Brewster angle" at the junction between glass and air. Been far too long since I studied optics, have to add more to the reading list.
The problem with a laser is the wave velocity is too fast. ~c, so T ~ P/c. With the frustum, T ~ P/v, where;
1/v ~ -(1/w)*d[ln(Q)]/dr
Where w is 2pi*f. We can replace Q by tau for decay time, or replace Q by Reactive power stored over Real power lost per cycle, as a function of r from the apex of the cone. We could cut the frustum simulations from front to back into circular cross sections and look at how much energy is stored and how much energy is lost in each cross section to calculate the derivative of Q. We can also approximate this as;
1/v ~ -(1/w*L)*ln(Qb/Qs)
Where L is the length, and the Q's are at the big and small end, respectively.
In any case, this is the equation we need to maximize by design. The larger this value is, the more thrust we will get.
Todd
NASA found best results with PTFE and HDPE dielectrics at the small end, which increases tan delta (dissipation) at the small end, hence lower Qs at the small end
1/v ~ -(1/w*L)*ln(Qb/Qs)
But this would argue for materials having much larger dissipation losses than HDPE or PTFE be better ?
I thought that they tried materials with more dissipation and they found worse results, not better. But have to check...to be sure
Also this prescription runs contrary to Shawyer, who maintains that it is better not to use any dielectrics (which were involved in his initial patents) because they decrease Q at one end and he thinks that's bad...
I would somewhat agree with the dielectric inserts although other tests have shown that thrusts can be shown w/o dielectrics.
EagleWorks was able to measure with a TE012 Q 22,000 2.6Watts 55.4 uN of thrust. Impressive.
Shell
http://libertariannews.org//wp-content//uploads//2014//07//AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
Grab from page 18 of the
Anomalous Thrust Production from an RF Test Device
Measured on a Low-Thrust Torsion Pendulum
David A. Brady*
, Harold G. White†
, Paul March‡
, James T. Lawrence§
, and Frank J. Davies**
NASA Lyndon B. Johnson Space Center, Houston, Texas 77058
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#2022 by Rodal on 26 Oct, 2016 02:32
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...
I would somewhat agree with the dielectric inserts although other tests have shown that thrusts can be shown w/o dielectrics.
EagleWorks was able to measure with a TE012 Q 22,000 2.6Watts 55.4 uN of thrust. Impressive.
Shell
http://libertariannews.org//wp-content//uploads//2014//07//AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
Grab from page 18 of the
Anomalous Thrust Production from an RF Test Device
Measured on a Low-Thrust Torsion Pendulum
David A. Brady*
, Harold G. White†
, Paul March‡
, James T. Lawrence§
, and Frank J. Davies**
NASA Lyndon B. Johnson Space Center, Houston, Texas 77058
Yes, the story of the EM Drive continues to be quite confusive
Just to make it clear those numbers for TE012 by NASA Eagleworks were achieved also with a HDPE polymer insert at the small end of the EM Drive.
Although that test had a force/InputPower higher than any other test ever achieved at Eagleworks, they appear to never have tried TE012 again, because it was difficult to achieve TE012 resonance again...
And, according to my recollection, Eagleworks tried other polymer inserts with higher tan delta dissipation than HDPE and PTFE and they got ... worse results . So there is no clear data indicating that higher dissipation is better at the small end, if my recollection is correct... -
#2023 by WarpTech on 26 Oct, 2016 02:52
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The problem with a laser is the wave velocity is too fast. ~c, so T ~ P/c. With the frustum, T ~ P/v, where;
1/v ~ -(1/w)*d[ln(Q)]/dr
Where w is 2pi*f. We can replace Q by tau for decay time, or replace Q by Reactive power stored over Real power lost per cycle, as a function of r from the apex of the cone. We could cut the frustum simulations from front to back into circular cross sections and look at how much energy is stored and how much energy is lost in each cross section to calculate the derivative of Q. We can also approximate this as;
1/v ~ -(1/w*L)*ln(Qb/Qs)
Where L is the length, and the Q's are at the big and small end, respectively.
In any case, this is the equation we need to maximize by design. The larger this value is, the more thrust we will get.
Todd
NASA found best results with PTFE and HDPE dielectrics at the small end, which increases tan delta (dissipation) at the small end, hence lower Qs at the small end
1/v ~ -(1/w*L)*ln(Qb/Qs)
But this would argue for materials having much larger dissipation losses than HDPE or PTFE be better ?
I thought that they tried materials with more dissipation and they found worse results, not better. But have to check...to be sure
Also this prescription runs contrary to Shawyer, who maintains that it is better not to use any dielectrics (which were involved in his initial patents) because they decrease Q at one end and he thinks that's bad...
I am working my way through this data. I will let you all know what I find out.
The equation above can be viewed in two ways. Qb is very small, or Qs is very large. The acceleration "g" depends on the log of this ratio. There are a lot of ways to get the same ratio, so we need to remember the other half of the thrust equation is the equivalent "mass" of the stored energy, and m ~ Q.
T = -m*g ~ -P/v, with 1/v as above.
Like gravity, we only need a relatively small gradient in the potential to get a decent acceleration. Ideally, we want a small acceleration and a large mass, so higher Qs will dominate if we want to move larger masses.
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#2024 by SeeShells on 26 Oct, 2016 03:14
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You're recompilation...
I would somewhat agree with the dielectric inserts although other tests have shown that thrusts can be shown w/o dielectrics.
EagleWorks was able to measure with a TE012 Q 22,000 2.6Watts 55.4 uN of thrust. Impressive.
Shell
http://libertariannews.org//wp-content//uploads//2014//07//AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
Grab from page 18 of the
Anomalous Thrust Production from an RF Test Device
Measured on a Low-Thrust Torsion Pendulum
David A. Brady*
, Harold G. White†
, Paul March‡
, James T. Lawrence§
, and Frank J. Davies**
NASA Lyndon B. Johnson Space Center, Houston, Texas 77058
Yes, the story of the EM Drive continues to be quite confusive
Just to make it clear those numbers for TE012 by NASA Eagleworks were achieved also with a HDPE polymer insert at the small end of the EM Drive.
Although that test had a force/InputPower higher than any other test ever achieved at Eagleworks, they appear to never have tried TE012 again, because it was difficult to achieve TE012 resonance again...
And, according to my recollection, Eagleworks tried other polymer inserts with higher tan delta dissipation than HDPE and PTFE and they got ... worse results . So there is no clear data indicating that higher dissipation is better at the small end, if my recollection is correct...
is correct they did find that the TE012 was a tough one to meet in the selected cavity, there were several close by frequencies that would also resonate and I believe the frequency if I read what they did on the Cannae frequency locking they did the same thing on the Q-Drive and that sounded like a mostly manual tuning. Very tough to do.QuoteDuring testing, the Test Engineer controls the RF frequency generation via a 0-to-28 volts dc power input to a voltage-controlled oscillator (VCO). The VCO RF signal output is passed to a variable voltage attenuator (VVA), the output of which is controlled by the Test Engineer via a 0-to-17 volts dc power input. Based upon the VVA output, the amplifier will output up to approximately 28 watts. Amplifier output passes to a dual-directional coupler
(DDC), which allows forward and reflected power measurements to be obtained as the power is simultaneously passed to the test article input port. The Test Engineer monitors forward and reflected power and adjusts the input frequency to obtain the desired combination of cavity frequency and power delivery to the cavity.QuoteHowever, since the TE012 mode had numerous other RF modes in very close proximity, it was impractical to repeatedly operate the system in this mode, so the decision was made to evaluate the TM211 modes instead.
That's been one reason I've TE mode locked with the antenna where only the TE mode will excite and the only close one is a TM. I can check with a IR camera to see if I'm exciting that TM mode.
Shell -
#2025 by InterestedEngineer on 26 Oct, 2016 04:54
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Quote from: Rodal
No, the location of the peak energy density is not due to any "absorption". See the excellent discussion by Greg Egan"
Greg Egan's analysis assumes a vacuum throughout the volume of the frustum.
As soon as you put a dielectric on one side, you no longer have a vacuum and Greg's analysis I believe no longer applies. Does a dielectric change where the peak energy is in the frustum?
The reason I ask is that EW used T012 mode and reported no thrust sans dielectric. They had to add a dielectric to get thrust.
I note the T011 and T013 modes have peak energy closer to the ends of the frustum. Has anyone gathered data to show whether or not a dielectric changes thrust in those modes?
If the answers are that a dielectric moves the peak energy point in T012 then maybe you have the beginnings of some data to back one of the many hypothesis here...Quote from: WarpTechThe location of the stored "potential" energy and the location where that energy is more readily dissipated forms a gradient inside the frustum.
In other words, since one end-plate is absorbing more while the other is reflecting more, the energy density of the cavity will be lower nearer one end : the absorbing end. Because an absorbing wall represents an energy sink.
Correct?
...
No, the location of the peak energy density is not due to any "absorption". See the excellent discussion by Greg Egan
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html
for an exact solution. The location of the peak in energy density is due to the mode shape, and the mode shapes are a result of the eigenvalue problem which is dictated by the equations of motion and the boundary conditions, and not by dissipation.
Here you have the first 3 TE mode shapes in an electromagnetically resonant truncated cone cavity.
There is no change whatsoever in absorption at each end for these modes. The modes are a result of the eigenvalue problem. That's why they are called eigenmodes !
TE011
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TE012
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TE013
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -
#2026 by meberbs on 26 Oct, 2016 06:36
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You pulled the first quote out of context. The discussion as I understood it was about having the end plates be made out of different metals with different resistances.Quote from: RodalNo, the location of the peak energy density is not due to any "absorption". See the excellent discussion by Greg Egan"
Greg Egan's analysis assumes a vacuum throughout the volume of the frustum.
As soon as you put a dielectric on one side, you no longer have a vacuum and Greg's analysis I believe no longer applies. Does a dielectric change where the peak energy is in the frustum?
The reason I ask is that EW used T012 mode and reported no thrust sans dielectric. They had to add a dielectric to get thrust.
I note the T011 and T013 modes have peak energy closer to the ends of the frustum. Has anyone gathered data to show whether or not a dielectric changes thrust in those modes?
If the answers are that a dielectric moves the peak energy point in T012 then maybe you have the beginnings of some data to back one of the many hypothesis here...
Adding a dielectric to the cavity changes the properties that the waves are propagating through for part of the volume. This changes the resonance frequency and will also affect the mode shape. People have suggested before that the additional dissipation in the dielectric may contribute to the thrust.
Most such theories I have seen have not clearly stated how this works though. Dielectric or not, classical EM theories including special relativity (but not general relativity) all yield no potential for thrust. There are some general relativity loopholes, or otherwise a theory needs some kind of new physics, maybe some kind of phantom particle that is being interacted with. -
#2027 by OttO on 26 Oct, 2016 06:48
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I just found that:
Analytic Solution of the Electromagnetic Eigenvalues Problem in a Cylindrical Resonator
https://arxiv.org/abs/1610.02083
"In order to understand how a resonant accelerating cavity transfers energy to charged particles, it is important to determine how the electromagnetic modes are exited into such resonators. In this paper we present a complete analytical calculation of the resonating fields for a simple cylindrical-shaped cavity."
I do not know if it is something new -
#2028 by Gilbertdrive on 26 Oct, 2016 09:19
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Here's some theory I think is central to emdrive :
Why doesn't a 100 Watt light torch give a reaction force ( kick back ) similar to a mechanical device with a power of 100 Watts?
An example of mechanical 100 Watt thruster is : A man throwing 2kg mass projectiles at 10 m/s once per second, every second. Such action would be plenty to accelerate the man in the opposite direction of his projectiles at m/s.
But the kickback from 100 W light torch would be effectively zero by comparison.
Why? The answer is : only a tiny fraction of the energy in light is as mechanical energy \ momentum. Most of it is stored in a EM wave which is lateral to its motion. In other words, a photon is like a thrown grenade, its kinetic energy is insignificant in comparison to its stored potential energy.
There is a big misunderstanding. The problem is not that there is something specific to light, the problem is that the Kinetic Energy is not equally distributed between the mass ejected, and a ship or a man throwing projectiles.
the absolute value of Momentum is distributed equally, but since momentum is proportional to the speed, and Kinetic Energy proportional to the square of the speed, the Kinetic Energy is not distributed equally.
You seem to think that any mecanical thruster would give the same result. It is not the case. If your man throws 0,2kg masses at 100m/s, he will get the same thrust that in your example, but with spending 10 times more energy. Each 0,2kg mass will have 10 times more Kinetic Energy than in your example, but the momentum will be the same.
That is why an ionic drive tends to have the same energy efficiency than a photon drive if the speed of the ejected mass tends to the speed of light. It would not be very usefull to have an ionic drive that send mass to 99% of C. It is simpler to do a collimated photon rocket.
To come back to your example, I shall suppose that the man is not moving at the begining in the earth referential, and the Kinetic Energies are expressed in the Earth referential.
When the masses are ejected 10 times faster and are 100 times smaller, the same amount of energy would be spent. But the man throwing the masses gets 10 times less thrust. He gives much Kinetic energy to the masses, but he get few Kinetic Energy himself.
Thrust is proportional to the momentum of the mass ejected. Energy spent is proportional to the Kinetic Energy of the mass ejected. That is why, the faster the masses are ejected, the less energy efficient the motor is. That is why a photon drive is not energy efficient. It has nothing to see with laterality. -
#2029 by Peter Lauwer on 26 Oct, 2016 09:59
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I guess I will post this here, as I did on Reddit where I asked people's opinion of divulging EmDrive information.
Based on my own concerns, the number of new people asking for help building plus the feedback I received on reddit, I've decided not to help others design, build or test an EmDrive. The exception to this is the very small group of individuals I currently work with, know and trust to have the credentials to work with this dangerous piece of gear.
As I see this project move from conjecture to reality, safety concerns have to be the #1 priority. It bears repeating, as I've done so during every guest interview I've done on science podcasts.
Do not consider live testing of an EmDrive unless you have experience in High Voltage, High Power RF and general RFI/EMI experience. Yes, the device is fascinating and has a great potential...it also has a danger associated with it. Leave it to the experts. - Dave
/soapbox
This applies if you intend to go for the kilowatt option. If you plan to work with, say 5 W, as I do, the dangers are much less, don't you agree? (so, there are many reasons to go for the low power experiments: costs, battery operated, safety, less heat, ...).
You have to put more effort in the measuring apparatus (torsion balance), that's true. '-) -
#2030 by dustinthewind on 26 Oct, 2016 13:16
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Here's some theory I think is central to emdrive :
Why doesn't a 100 Watt light torch give a reaction force ( kick back ) similar to a mechanical device with a power of 100 Watts?
An example of mechanical 100 Watt thruster is : A man throwing 2kg mass projectiles at 10 m/s once per second, every second. Such action would be plenty to accelerate the man in the opposite direction of his projectiles at m/s.
But the kickback from 100 W light torch would be effectively zero by comparison.
Why? The answer is : only a tiny fraction of the energy in light is as mechanical energy \ momentum. Most of it is stored in a EM wave which is lateral to its motion. In other words, a photon is like a thrown grenade, its kinetic energy is insignificant in comparison to its stored potential energy.
There is a big misunderstanding. The problem is not that there is something specific to light, the problem is that the Kinetic Energy is not equally distributed between the mass ejected, and a ship or a man throwing projectiles.
the absolute value of Momentum is distributed equally, but since momentum is proportional to the speed, and Kinetic Energy proportional to the square of the speed, the Kinetic Energy is not distributed equally.
You seem to think that any mecanical thruster would give the same result. It is not the case. If your man throws 0,2kg masses at 100m/s, he will get the same thrust that in your example, but with spending 10 times more energy. Each 0,2kg mass will have 10 times more Kinetic Energy than in your example, but the momentum will be the same.
That is why an ionic drive tends to have the same energy efficiency than a photon drive if the speed of the ejected mass tends to the speed of light. It would not be very usefull to have an ionic drive that send mass to 99% of C. It is simpler to do a collimated photon rocket.
To come back to your example, I shall suppose that the man is not moving at the begining in the earth referential, and the Kinetic Energies are expressed in the Earth referential.
When the masses are ejected 10 times faster and are 100 times smaller, the same amount of energy would be spent. But the man throwing the masses gets 10 times less thrust. He gives much Kinetic energy to the masses, but he get few Kinetic Energy himself.
Thrust is proportional to the momentum of the mass ejected. Energy spent is proportional to the Kinetic Energy of the mass ejected. That is why, the faster the masses are ejected, the less energy efficient the motor is. That is why a photon drive is not energy efficient. It has nothing to see with laterality.
Here is a derivation of kinetic energy exchanged on the reflection of a massive ball with another massive object. https://forum.nasaspaceflight.com/index.php?topic=31037.msg1494279#msg1494279 The energy exchanged on a collision depends on the mass of the ball. The mass in a photon by its energy is ridiculously small so almost no energy is exchanged on a reflection. From this one can get the doppler shift in light from a reflection given here: https://forum.nasaspaceflight.com/index.php?topic=31037.msg1497641#msg1497641 Notice, a Doppler shifted photon from a reflection receives twice the Doppler shift, just as a photon sail receives twice the propulsion as a laser thuster (twice as much energy exchanged).
The only way I can see of harvesting the kinetic energy out of light in a closed cavity a.t.m. is by creating an asymmetry in the mass of light at one end of the cavity. After say, 1000 reflections of the photon losing .oo2% of its energy at one end and receiving back .001% at the other we have % energy exchanged = (.001-.002)%*1000 = -.2% energy lost by the photon, and in this case we have more effectively drained the kinetic energy from light but still not that effectively. Increasing the Q in this case would increase the thrust. We have to consider as the energy drains the light is red-shifted.
It seems to effectively change the mass of light in a cavity asymmetrically while preserving the direction of momentum may require another medium for light to exchange energy with as a propellant. This may be the Quantum vacuum or General Relativity for instance. A book Todd recommended on the QED vacuum: Book url or PV (polarizable vacuum by Puthoff) parallel to relativity. Another recent development has been the creation of electron-positron pairs from the vacuum, and one might surmise their analogue increase in osculation amplitude as they are created such that they exist with out fully existing as separate pairs. (i.e. at lower energy levels.) -
#2031 by kaublezw on 26 Oct, 2016 13:29
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I'm new to this massive thread. I have to say this has got to be the most exciting place to be on the internet.
I'm still trying to catch up and understand the test results and theory.
One question I have that I'm sure has already been answers: Has anybody been able to prove that the thrust is not caused by atoms being stripped from the cavity? -
#2032 by dustinthewind on 26 Oct, 2016 13:44
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I'm new to this massive thread. I have to say this has got to be the most exciting place to be on the internet.
If atoms inside the cavity are trapped and can not escape, then no net momentum should come from them. I'm still trying to catch up and understand the test results and theory.
One question I have that I'm sure has already been answers: Has anybody been able to prove that the thrust is not caused by atoms being stripped from the cavity? -
#2033 by RERT on 26 Oct, 2016 15:01
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"quite confusive" --- occasionally verging on downright confusticational!
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#2034 by Gilbertdrive on 26 Oct, 2016 15:26
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I'm new to this massive thread. I have to say this has got to be the most exciting place to be on the internet.
If atoms inside the cavity are trapped and can not escape, then no net momentum should come from them. I'm still trying to catch up and understand the test results and theory.
One question I have that I'm sure has already been answers: Has anybody been able to prove that the thrust is not caused by atoms being stripped from the cavity?
I suppose that kaublezw means ripped from and escaping outside...
My answer will be that, on this forum, we will not agree on this question. some, like The Traveller, considers that the Emdrive effects is proven to be real. Many of us think that there are no definite proof about almost anything.
Anyway, entire atoms being ripped from the cavity does not seem very likely, IMHO, electrons being riped and accelerated seems more likely to me... that is why battery powered and vacuum experiments are strongly needed
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#2035 by meems on 26 Oct, 2016 15:40
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...
You seem to think that any mecanical thruster would give the same result. It is not the case. If your man throws 0,2kg masses at 100m/s, he will get the same thrust that in your example, but with spending 10 times more energy. Each 0,2kg mass will have 10 times more Kinetic Energy than in your example, but the momentum will be the same.
That is why an ionic drive tends to have the same energy efficiency than a photon drive if the speed of the ejected mass tends to the speed of light. It would not be very usefull to have an ionic drive that send mass to 99% of C. It is simpler to do a collimated photon rocket...
Thanks Gilbert, that was a relevant post that needed to be written. I agree with what you say, and I agree that my 'harvesting the lateral EM wave of light' idea was a long shot. However, a brainstorm of such wild ideas are needed to try explain what emdrive is somehow doing : converting lightwave energy into kinetic energy.
I think this problem does have an all mechanical anology : converting the energy of bullets into slow coherent motion; this may give us insight into emdrive...
The problem of collisions at high energy momentum ratio
...i.e. firing bullets at a large boulder as a method of thrust for the boulder. The bullets, with their high energy/momentum ratio will act like a bit like waves when they hit the boulder : i.e. their energy will be converted into a spherically expanding shell of energy, bullet and boulder fragments, and a shockwave will dump heat in the boulder. Not useful for thrust. The bullet energy is converted to incoherent heat \ entrophy rather thn coherent motion of the boulder. The faster the bullet, the more wave like the collision is.
To itself as its travelling, the bullet's KE energy is coherent energy, it only becomes dispersed at collision with the boulder.
The question is then : How then to pass on the coherence of the bullets energy to the boulder?
Dough Boulder
One simple improvement it to make the boulder soft, like dough. This way, at least the bullet's energy isn't used to particlize and scatter the bullet or the boulder. The bullet decelerates slowly and comes to rest intact. But a lot of the bullets energy still goes into heating and deforming the boulder rather than pushing it.
Converting this analogy over to emdrive : step 1/2
( bear with us, its worth it! )
A slightly different, more hypothetical and fanciful idea would be to have the bullet collide sequentially with gradually slower moving small objects. The 1st object that it collides with is travelling only 1 m/s slower than the bullet and in the same direction : this highlights the idea of relative energy / momentum. From the perspective the gun and the boulder, the bullet has a high energy / momentum ratio, replete with the problem of converting energy to coherent motion at the boulder. But to an object that is nearly at rest wrt the bullet, the bullet's energy / momentum ratio is low, and momentum transfer can be efficient. After the bullet collides with the 1st object, it has slowed, it can then collide with the 2nd object, which was traveling at 2m/s slower than the bullets initial velocity, the process iterates, to the 3rd at 3m/s slower, 4th etc...
If this were possible it would be an even more effective than the dough boulder at converting the energy of the bullet into slow coherent KE - i.e. momentum.
Converting this analogy over to emdrive : step 2/2
So can something like this be happening in the emdrive cavity? Yes.
Starting with lightwaves ( the bullets ), we need to have something that will act as the set of sequentially slower moving objects. There is only one object that can be : electrons - yes a cavity full of microwaves with conductor walls will have a few loose electrons in it- electron plasma. Starting at one end of the cavity, light is passing its energy quite efficiently onto fast high energy electrons, which pass on kinetic energy to low energy electrons, until the lowest energy electrons pass on KE to one of the end plates, which absorbs the energy more efficiently as KE than if it was just being hit with the unaltered light ( initial high speed bullets ).
Lab experimenters may want to look for a gradient in electron energy within the cavity. -
#2036 by Bob012345 on 26 Oct, 2016 15:50
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Seems almost too simple, I like it. I was awake last night and couldn't stop thinking a demonstration is all around us all the time. Much like gravity was exploited by mankind long before Newtons explanation. Still I would expect cylindrical cavities with varying endplates have been studied extensively.
A poor example off the top of my head, a common laser has partially silvered mirror at one end. Optical wavelengths reflected power are controlled with a "Brewster angle" at the junction between glass and air. Been far too long since I studied optics, have to add more to the reading list.
The problem with a laser is the wave velocity is too fast. ~c, so T ~ P/c. With the frustum, T ~ P/v, where;
1/v ~ -(1/w)*d[ln(Q)]/dr
Where w is 2pi*f. We can replace Q by tau for decay time, or replace Q by Reactive power stored over Real power lost per cycle, as a function of r from the apex of the cone. We could cut the frustum simulations from front to back into circular cross sections and look at how much energy is stored and how much energy is lost in each cross section to calculate the derivative of Q. We can also approximate this as;
1/v ~ -(1/w*L)*ln(Qb/Qs)
Where L is the length, and the Q's are at the big and small end, respectively.
In any case, this is the equation we need to maximize by design. The larger this value is, the more thrust we will get.
Todd
There have been experiments where light has been slowed to very low values, such as 1 m/s within a specific gaseous environment. Combining that physics with resonant cavities of the properties of EmDrives with the correct adjustments, might allow one to use lasers to great effect instead of microwaves. Just a thought.
Also, on a related note, it has been shown that photons can be recycled between two mirrors using a gain medium with such stability that one can move the one of the mirrors with your hand and not ruin the Q. -
#2037 by kaublezw on 26 Oct, 2016 16:07
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I'm new to this massive thread. I have to say this has got to be the most exciting place to be on the internet.
If atoms inside the cavity are trapped and can not escape, then no net momentum should come from them. I'm still trying to catch up and understand the test results and theory.
One question I have that I'm sure has already been answers: Has anybody been able to prove that the thrust is not caused by atoms being stripped from the cavity?
I suppose that kaublezw means ripped from and escaping outside...
My answer will be that, on this forum, we will not agree on this question. some, like The Traveller, considers that the Emdrive effects is proven to be real. Many of us think that there are no definite proof about almost anything.
Anyway, entire atoms being ripped from the cavity does not seem very likely, IMHO, electrons being riped and accelerated seems more likely to me... that is why battery powered and vacuum experiments are strongly needed
Yes, I meant stripped from outside of the cavity. I've read everything that I could online, and I have to say that I'm skeptical of EmDrive's legitimacy, particularly the 2nd generation claims made by Shawyer. BUT that doesn't mean I'm not rooting for it! Also, there are a lot of haters out there that simply live to observe others' failures. But, the skepticism expressed in this thread seems to be healthy and warranted for the most part IMHO.
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#2038 by Rodal on 26 Oct, 2016 16:17
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A small note: there appears to be some typo or issue in the 2014 Brady report (http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf), both in that paragraph and in a chart (attached below), as the mode shape at that frequency is TM212, and not TM211, even according to their COMSOL analysis the TM211 resonates at a significant lower natural frequency than TM212 which resonates at 1.9 GHz with the HDPE insert.QuoteHowever, since the TE012 mode had numerous other RF modes in very close proximity, it was impractical to repeatedly operate the system in this mode, so the decision was made to evaluate the TM211 modes instead.
That's been one reason I've TE mode locked with the antenna where only the TE mode will excite and the only close one is a TM. I can check with a IR camera to see if I'm exciting that TM mode.
Shell
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#2039 by Notsosureofit on 26 Oct, 2016 17:10
is correct they did find that the TE012 was a tough one to meet in the selected cavity, there were several close by frequencies that would also resonate and I believe the frequency if I read what they did on the Cannae frequency locking they did the same thing on the Q-Drive and that sounded like a mostly manual tuning. Very tough to do.
I'm still trying to catch up and understand the test results and theory.