#### aero

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##### Re: EM Drive Developments
« Reply #2000 on: 10/11/2014 11:33 PM »
By the way, that acceleration will exceed the speed of light in less than one cycle of the RF wave.
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#### Rodal

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##### Re: EM Drive Developments
« Reply #2001 on: 10/12/2014 01:44 AM »
And of course, for the photoelectric effect, to emit electrons from the surface of the copper, the microwave frequency is way too low:

Planck constant= 6.63×10^(−34) J s
Frequency = 1.93x10^9 1/s
Copper Photoelectric Work Function = 7.5 × 10^(−19) J

Kinetic Energy of Emitted Electron = (6.63×10^(−34) J s)x(1.93x10^9 1/s) - 7.5 × 10^(−19) J
= 1.28x10^(-24) J - 7.5 × 10^(−19) J
< 0

To emit electrons from the surface of the copper by the photoelectric effect, the frequency of the microwave is way too low, by a factor of about a million.
« Last Edit: 10/12/2014 01:49 AM by Rodal »

#### aero

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##### Re: EM Drive Developments
« Reply #2002 on: 10/12/2014 03:56 AM »
Electrons must come from the dielectric. At least that would explain why no thrust without dielectric.

If electrons are involved at all. What role do you see electrons playing in this device?
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#### Mulletron

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##### Re: EM Drive Developments
« Reply #2003 on: 10/12/2014 05:14 AM »
You hit the nail on the head when you mentioned the skin effect. Those accelerating electrons in the walls reacting to the rf stay inside. The only thing that makes it outside is uneven heating. Hence why you need to react against something for the thing to work. Otherwise you have a big fancy space heater thruster. Quantum thrust is the answer.
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#### Rodal

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##### Re: EM Drive Developments
« Reply #2004 on: 10/12/2014 05:15 AM »
Since we cannot see how the electrons in the copper would be accelerated to the required acceleration, let's examine the photons.

Extremely high accelerations are involved when photons are reflected at the copper surface.  Velocity is a vector of course: a change in direction is a change in velocity.  The highest acceleration is the one resulting from a photon traveling perpendicular to a flat surface, being reflected from the surface so that it travels in the opposite direction.

The photons reflected from the copper are identical to the incident ones, apart from the changed propagation direction. Some fraction of the photons are lost, while the energy content of each reflected photon is fully preserved. Which of the photons are lost is a matter of chance; there is a certain probability for each photon to be absorbed. There will be complete reflection (and no heating of the metal) in most cases and complete absorption with associated heating (creation of so-called phonons in the metal) in some cases.

Question: does acceleration due to reflection (due to a change in direction but no change in magnitude) satisfy the requirement of high acceleration for the Unruh radiation for McCulloch's simplified formula?
Is Unruh radiation involved whenever light hits a mirror ?

The dominant behavior in this case is reflection of course, but here is a discussion of group velocity (as used by Shawyer)  and phase velocity (as appearing in the refractive index)

1) The simplified McCulloch formula is similar to the Shawyer formula (albeit from completely different derivation and physical reasons): Power*Q/f*(1/radiusA - 1/radiusB).   Shawyer's derivation involves the group velocity.

2) The refractive index can be involved to a very small extent when a photon hits the copper surface with wavelengths smaller than a few micrometers.  But for the EMDrive we are dealing with much longer wavelengths in the order of 0.1 to 1 meters, (hundreds of thousand times longer wavelength).

The refractive index is inversely proportional to the phase velocity of light:

Refractive index = (velocity of light in a vacuum)/(phase velocity of light in the substance)

The phase velocity is the speed at which the crests of the wave move.   In copper the phase velocity [ for wavelengths exceeding 10 micrometers] is much lower than the speed of light in a vacuum.  The refractive index is much higher than 1 (actually much higher than 10 for the wavelengths exceeding 10 micrometers), and there are very high absorption losses at those wavelengths.

Real part of refractive index ( indicates the phase velocity):

Imaginary part of refractive index (indicates the amount of absorption loss when the electromagnetic wave propagates through the material.)

This example is not a good example for refraction in copper.  I only show it to illustrate what is the phase velocity[appearing in the refractive index] and what is the group velocity [used by Shawyer].

The red dot moves with the phase velocity, and the green dots propagate with the group velocity. In this case, the phase velocity is twice the group velocity. The red dot overtakes two green dots when moving from the left to the right of the figure.

« Last Edit: 10/13/2014 01:21 PM by Rodal »

#### Mulletron

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##### Re: EM Drive Developments
« Reply #2005 on: 10/12/2014 05:43 AM »
I get that phase velocity can out run group velocity and can even be superluminal but where's the thrust? It is a closed system.

I hope you're on to something. I'd like to do away with quantum thrust too and explain anomalous thrust in a simpler way, besides uneven heating.

« Last Edit: 10/12/2014 09:59 AM by Mulletron »
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#### aero

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##### Re: EM Drive Developments
« Reply #2006 on: 10/12/2014 05:44 AM »
If it's any help, some time ago I used E = mc^2 and calculated the energy mass of the stored energy within the cavity. I got -

1, TM211   1.37644E-12   kg
2, TM211   3.36321E-12   kg
3, TE012   6.36436E-13   kg

I don't know if this factors into the problem or not.
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#### frobnicat

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##### Re: EM Drive Developments
« Reply #2007 on: 10/12/2014 10:03 AM »
Well, for what its worth I calculate the skin depth for copper at 1900 MHz is about 1.5 microns.

The electron acceleration I get is about 7.7 g's. Not near high enough.

And note, to be precise, the cavity dimensions are about 0.25146 m major dia., 0.16764 m minor dia. 0.2286 m height. (Picked off the screen picture with a ruler scaling to the 1.5 inch cross section of the support arm.)

7.7g

If I understand Rodal, the idea would be to consider the oscillating electrons as a moving wall (a bit like the "moving mirror" in dynamical Casimir effect experiments). Those electrons wouldn't be ejected, they are accelerated back and forth but kept at stationary position (averaged on a period), it's like a "vibratory wall". During a half period that is 1/(2freq) all electrons could go for a back and forth trip of half a skin depth (considering only moves normal to the surfaces are relevant as for a moving "volume"). Give or take a 0.5 factor somewhere we are about max acceleration = skin_depth * freq² = 1.5e-6 * 1.9e9² = 5.4e12 m/s², huge but five orders of magnitude below needed acceleration for Unruh waves of 1m long (from McCulloch as reported by Rodal). That's by assuming all electrons go full back and forth oscillation at skin depth.

Was that it ?

http://arxiv.org/abs/1103.0835
I like fig. 2 page 4 that links the different effects.

I don't see photons could play the role of a moving wall for a cavity bouncing photons (virtual or real).
« Last Edit: 10/12/2014 10:05 AM by frobnicat »

#### Mulletron

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##### Re: EM Drive Developments
« Reply #2008 on: 10/12/2014 10:20 AM »
Well, for what its worth I calculate the skin depth for copper at 1900 MHz is about 1.5 microns.

The electron acceleration I get is about 7.7 g's. Not near high enough.

And note, to be precise, the cavity dimensions are about 0.25146 m major dia., 0.16764 m minor dia. 0.2286 m height. (Picked off the screen picture with a ruler scaling to the 1.5 inch cross section of the support arm.)

7.7g

If I understand Rodal, the idea would be to consider the oscillating electrons as a moving wall (a bit like the "moving mirror" in dynamical Casimir effect experiments). Those electrons wouldn't be ejected, they are accelerated back and forth but kept at stationary position (averaged on a period), it's like a "vibratory wall". During a half period that is 1/(2freq) all electrons could go for a back and forth trip of half a skin depth (considering only moves normal to the surfaces are relevant as for a moving "volume"). Give or take a 0.5 factor somewhere we are about max acceleration = skin_depth * freq² = 1.5e-6 * 1.9e9² = 5.4e12 m/s², huge but five orders of magnitude below needed acceleration for Unruh waves of 1m long (from McCulloch as reported by Rodal). That's by assuming all electrons go full back and forth oscillation at skin depth.

Was that it ?

http://arxiv.org/abs/1103.0835
I like fig. 2 page 4 that links the different effects.

I don't see photons could play the role of a moving wall for a cavity bouncing photons (virtual or real).

That is a good find and thank you. I'm starting to see a pattern here. Every way I look at emdrive, the quantum vacuum keeps getting put back on the table. (Confirmation bias or something real?) I'm going to spend the rest of the day digesting this paper.

You're right, figure 2 does a great job demonstrating the relations of all those in the presence of gravitational accelerations.

The walls of the cavity, in addition to the static casimir effects already postulated, could be exhibiting a weak dynamical casimir effect by virtue of the movements of the electrons. They aren't a moving mirror so this is very loosely correlated. How can a moving electron act as a moving mirror affecting any modes if any? The surface isn't exactly reflective in the optical sense, but it is to other wavelengths. Should the emdrive be silvered? Or covered in DLP like chips, to enhance this? Now I'm falling down another rabbit hole.

I imagine the whole cavity vibrates like this when rf is on. I can tell you from experience from radars, if you touch the outside of a magnetron while it is on, you feel a nice vibration or hum.

Rodal, is this where you were going?

Also, what is the parametric parameter with emdrive? Is there one?
« Last Edit: 10/12/2014 11:05 AM by Mulletron »
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#### Mulletron

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##### Re: EM Drive Developments
« Reply #2009 on: 10/12/2014 12:25 PM »
Well it looks like some Egyptian physics student named Aisha Mustafa has already invented this type of dynamic casimir effect quantum thruster. Another ball in EMdrive's court.

So we have Sonny White, Shawyer (though he isn't saying emdrive is being driven quantumly, and the consensus is his representations about how why his own invention works don't make sense, he might not know how why it works, he just knows it works), and this Egyptian girl all working on the same thing in parallel.

http://www.emdrive.com/theorypaper9-4.pdf Shawyer's latest theory paper.

Oh and Woodward too (same as Shawyer), and who knows who else is working on this kind of propulsion.

Seems like many people are grasping at the same ideas here in parallel.

Another very good sign that EMdrive probably really works.
« Last Edit: 10/12/2014 12:40 PM by Mulletron »
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#### JohnFornaro

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##### Re: EM Drive Developments
« Reply #2010 on: 10/12/2014 01:08 PM »
Another very good sign that EMdrive probably really works.

Another good sign that the promise of the drive excites the imagination, and results in a good deal of professional interest.

Film note:  One of my earlier pieces.

Hark ye!
Sometimes I just flat out don't get it.

#### Mulletron

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##### Re: EM Drive Developments
« Reply #2011 on: 10/12/2014 01:16 PM »
Another very good sign that EMdrive probably really works.

Another good sign that the promise of the drive excites the imagination, and results in a good deal of professional interest.

Film note:  One of my earlier pieces.

Hark ye!

I'm assuming I can trust the experimentalists. You're right though. It doesn't officially work until it is undeniable.
And I can feel the change in the wind right now - Rod Stewart

#### Rodal

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##### Re: EM Drive Developments
« Reply #2012 on: 10/12/2014 01:24 PM »
Back to the real world after all this Mustafa FLT, dynamic and static Casimir effects with non-existing plates at an infinitesimal distance from each other, back to the real world

As Prof. McCulloch posted today (http://physicsfromtheedge.blogspot.it/2014/10/mihsc-vs-emdrive-data-1.html), the acceleration of the photons transiting the cavity is

a = 2 c^2 / (CavityLength)

and recall that for Unruh radiation McCulloch inertial mass change we must have

a > 8 c^2 / (DiameterOfFlatSurface)

So we need,

2 c^2 / (CavityLength) > 8  c^2 / (DiameterOfFlatSurface)

or

(DiameterOfFlatSurface)/(CavityLength)  > 4

Which is not satisfied for these EMDrives.

Actually

For the NASA Eagleworks truncated cone, using the radius of the larger flat surface:

(DiameterOfFlatSurface)/(CavityLength)  ~ 1

So the acceleration required for Unruh radiation waves is about 4 times greater than the actual photon acceleration in the cavity.

As Prof. McCulloch states:  "this is a wild leap".

« Last Edit: 10/13/2014 02:20 PM by Rodal »

#### JohnFornaro

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##### Re: EM Drive Developments
« Reply #2013 on: 10/12/2014 01:42 PM »
2) What objects inside the cavity are accelerating to 7.2*10^17 m/s^2 ?

...that is an acceleration of
730,000,000,000,000,000
times larger than 1 g.

By the way, that acceleration will exceed the speed of light in less than one cycle of the RF wave.

Somebody check this?  Before I call el poopo del toro?

I get that phase velocity can out run group velocity and can even be superluminal but where's the thrust?

There is no thrust in group velocity.  Period.

Reading up on the Unruh thingy, first, a typical grammatical objection:

Vacuum is simply thought to be the lowest possible energy state of these fields.

I would never dare speak for the peanut gallery, but I'm struggling with accepting an effect which has not been observed as being postulated for another effect, anomalous thrust, which has not yet been reliably and repeatedly observed by others in the scientific community.
« Last Edit: 10/12/2014 01:43 PM by JohnFornaro »
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#### frobnicat

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##### Re: EM Drive Developments
« Reply #2014 on: 10/12/2014 01:58 PM »
The walls of the cavity, in addition to the static casimir effects already postulated, could be exhibiting a weak dynamical casimir effect by virtue of the movements of the electrons. They aren't a moving mirror so this is very loosely correlated. How can a moving electron act as a moving mirror affecting any modes if any? The surface isn't exactly reflective in the optical sense, but it is to other wavelengths. Should the emdrive be silvered? Or covered in DLP like chips, to enhance this? Now I'm falling down another rabbit hole.

A sea of free electrons is a mirror, for wavelengths longer than distance between them (optical yes, microwave definitely) so moving electrons do behave as a moving mirror (with a very low inertia compared to a solid mirror). Actually it is the "recoil" of being a mirror for the microwaves that makes them move and could make them move for other wavelength. Then the space charge prevent them to leave completely : they are bound within a certain depth by the positive holes they left in the lattice by moving... Basically this is a capacitor : applied E field => proportional charge displacements. That said, I'm far form certain this makes any sense : wouldn't the free electron (of the copper walls) move tangentially rather than normal to the surfaces to "counteract" the incoming E field and making the RF wave bounce ? What are the patterns of the "eddy currents" in presence of standing waves ? Intuitively I would say we have large scale current loops trying to make a H field normal to surface, that is tangential currents, not normal back and forth like a capacitor. If the charge displacements are tangential then the "mirror" isn't really moving (constant enclosed volume).

If alternating back and forth in the depth, then we have (from capacitor analogy) density of electrons rho=Q/A (Charge on Area) and electric field E=rho/eps (permittivity). From  8.5×10^28 electrons per cubic metre for copper we have 1.36e10 Coulomb/m^3 that is rho=2e4 C/m² at 1.5µm depth and E = 2e4/8.8e-12 = 2.3e15 V/m. See also permittivity D=eps E  : D is same as rho (C/m²) E electric field (V/m) and eps whatever...
I'm doing as if the electrons of the copper were in vacuum...

Mmm, this E is not in excess of vacuum dielectric strength (1e18 V/m)  What are the E fields reported for the EMdrives resonant cavities ? Because this is in far excess of air (3e6 V/m) and even teflon (up to 1.7e8 V/m) dielectric strength. So even if high Q factor could pump up E field amplitude to such levels, materials would experience breakdown. Unless I messed up a 10^9 factor somewhere again ?
And such a hypothetical move of all electrons back and forth to skin depth can only make for about 5e12m/s² moving (oscillating mirror) : is it enough ?

#### Mulletron

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##### Re: EM Drive Developments
« Reply #2015 on: 10/12/2014 02:06 PM »
By what logic are you assuming a photon would see unruh radiation when the speed of light is the same in all reference frames?

This accelerating photon seeing unruh radiation stuff is nonsense.

So is any notion of thrust using differences between group or phase velocities. Shawyer tried using the different group velocity argument.

The fact is that for any rocket to work it has to react against something.
« Last Edit: 10/12/2014 02:12 PM by Mulletron »
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#### Rodal

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##### Re: EM Drive Developments
« Reply #2016 on: 10/12/2014 02:08 PM »
The walls of the cavity, in addition to the static casimir effects already postulated, could be exhibiting a weak dynamical casimir effect by virtue of the movements of the electrons. They aren't a moving mirror so this is very loosely correlated. How can a moving electron act as a moving mirror affecting any modes if any? The surface isn't exactly reflective in the optical sense, but it is to other wavelengths. Should the emdrive be silvered? Or covered in DLP like chips, to enhance this? Now I'm falling down another rabbit hole.

A sea of free electrons is a mirror, for wavelengths longer than distance between them (optical yes, microwave definitely) so moving electrons do behave as a moving mirror (with a very low inertia compared to a solid mirror). Actually it is the "recoil" of being a mirror for the microwaves that makes them move and could make them move for other wavelength. Then the space charge prevent them to leave completely : they are bound within a certain depth by the positive holes they left in the lattice by moving... Basically this is a capacitor : applied E field => proportional charge displacements. That said, I'm far form certain this makes any sense : wouldn't the free electron (of the copper walls) move tangentially rather than normal to the surfaces to "counteract" the incoming E field and making the RF wave bounce ? What are the patterns of the "eddy currents" in presence of standing waves ? Intuitively I would say we have large scale current loops trying to make a H field normal to surface, that is tangential currents, not normal back and forth like a capacitor. If the charge displacements are tangential then the "mirror" isn't really moving (constant enclosed volume).

If alternating back and forth in the depth, then we have (from capacitor analogy) density of electrons rho=Q/A (Charge on Area) and electric field E=rho/eps (permittivity). From  8.5×10^28 electrons per cubic metre for copper we have 1.36e10 Coulomb/m^3 that is rho=2e4 C/m² at 1.5µm depth and E = 2e4/8.8e-12 = 2.3e15 V/m. See also permittivity D=eps E  : D is same as rho (C/m²) E electric field (V/m) and eps whatever...
I'm doing as if the electrons of the copper were in vacuum...

Mmm, this E is not in excess of vacuum dielectric strength (1e18 V/m)  What are the E fields reported for the EMdrives resonant cavities ? Because this is in far excess of air (3e6 V/m) and even teflon (up to 1.7e8 V/m) dielectric strength. So even if high Q factor could pump up E field amplitude to such levels, materials would experience breakdown. Unless I messed up a 10^9 factor somewhere again ?
And such a hypothetical move of all electrons back and forth to skin depth can only make for about 5e12m/s² moving (oscillating mirror) : is it enough ?
The maximum electric fields at the dielectric are calculated to be 47000 V/m.  The electric field in the cavity is only about 1500 to 2000 V/m.
I am on record since I entered this thread that I see nothing whatsoever in these EMDrives related to the hypothetical Dynamic Casimir effect.
« Last Edit: 10/12/2014 02:09 PM by Rodal »

#### frobnicat

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##### Re: EM Drive Developments
« Reply #2017 on: 10/12/2014 02:10 PM »
2) What objects inside the cavity are accelerating to 7.2*10^17 m/s^2 ?

...that is an acceleration of
730,000,000,000,000,000
times larger than 1 g.

By the way, that acceleration will exceed the speed of light in less than one cycle of the RF wave.

Somebody check this?  Before I call el poopo del toro?

7.2e17*(1/1.9e9) = 3.8e8 m/s = 380000km/s
exceeding light speed yes, but only slightly, I guess for such a small deviation we should be tolerant. For instance since the movement would be periodic and sinusoidal, this would be the max acceleration (at peaks) and the max speed in between (crossing the middle line) could be below c I believe. Also m/s² is ill defined when approaching relativistic speeds, no ?

#### Rodal

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##### Re: EM Drive Developments
« Reply #2018 on: 10/12/2014 02:14 PM »
By what logic are you assuming a photon would see unruh radiation when the speed of light is the same in all reference frames?

This accelerating photon seeing unruh radiation stuff is nonsense.

...

Non sequitur and unfounded.

« Last Edit: 10/12/2014 02:15 PM by Rodal »

#### frobnicat

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##### Re: EM Drive Developments
« Reply #2019 on: 10/12/2014 02:21 PM »
By what logic are you assuming a photon would see unruh radiation when the speed of light is the same in all reference frames?

Are you asking that to me ?
I don't think a photon would see Unruh radiation, I think a moving "wall of electrons" (periodically) accelerating at great values could see Unruh radiation. I believe the speed of light is the same in all inertial reference frames. I don't believe in the claimed results so far, I think a number of more or less exotic effects could be used to get net forward thrust from power, but not at better than 1/c (as Newtons/Watts). But I'm not qualified to have any authority on the subject, just trying to follow.
« Last Edit: 10/12/2014 02:22 PM by frobnicat »

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