Author Topic: EM Drive Developments Thread 1  (Read 765782 times)

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #800 on: 09/20/2014 02:35 PM »
Presumably, the "plasma" refers to the probability that a pair of photons can create an electron-positron pair which transfer some momentum and recombine as a doppler shifted pair   photons.

There's the rub.  The wavefunction for the interaction would have a wavelength  of the order of the difference in energy between the before and after photons, ie. much larger than the resonator.

Then too, one of the dark matter candidates has extremely low mass, (long wavelength) but no interaction ?
« Last Edit: 09/20/2014 02:56 PM by Notsosureofit »

Online Rodal

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Re: EM Drive Developments
« Reply #801 on: 09/20/2014 03:14 PM »
.....
Then too, one of the dark matter candidates has extremely low mass, (long wavelength) but no interaction ?

Axions are predicted to change to and from photons in the presence of strong magnetic fields, and this property is used for creating experiments to detect axions.  Axions have no electric charge, a very small mass ( 10−6 to 1 eV/c^2 ), and very low interaction cross-sections for strong and weak forces. Axions interact only minimally with ordinary matter.

Given that (see previous post:  http://forum.nasaspaceflight.com/index.php?topic=29276.msg1256192#msg1256192)

1) even a photon rocket has orders of magnitude lower SpecificForce=thrust/InputPower than the reported experimental measurements and 2) to have net propulsion one has to have the photons escape one end of the device,

I don't follow how Axions could be responsible for the reported experimental measurements
« Last Edit: 09/20/2014 03:18 PM by Rodal »

Offline CW

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Re: EM Drive Developments
« Reply #802 on: 09/20/2014 03:22 PM »
Here is a little thought experiment:

Imagine a perfectly reflective metal cavity, into which a photon from the outside is injected through a tiny hole in the cavity walls. When the photon hits the inner wall for the first time, it imparts 2x its impulse on the cavity (when being absorbed and then emitted again). Thus, the cavity gains a little momentum and moves a little bit into the photon's original impulse direction, aka translation. Then the reflected photon hits the opposite inner wall and effectively stops the cavity's movement again. But: Out metal box moved for a nanosecond or so, and hence the box has experienced a translational movement. At the same time, conservation of momentum was not violated: It's time-averaged ZERO. Still, we got a translation. Let's say the photon can be reflected for 1s overall within the cavity - that would mean we'd get 10^9 impulse impartings and thus translational movements within a 15cm length cavity (1ns per ping-pong). Not bad for a lonely photon ;) .

What do you think?
« Last Edit: 09/20/2014 03:27 PM by CW »
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Online Rodal

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Re: EM Drive Developments
« Reply #803 on: 09/20/2014 03:27 PM »
Here is a little thought experiment:

Imagine a perfectly reflective metal cavity, into which a photon from the outside is injected through a tiny hole in the cavity walls. When the photon hits the inner wall for the first time, it imparts 2x its impulse on the cavity (when being absorbed and then emitted again). Thus, the cavity gains a little momentum and moves a little bit into the photon's original impulse direction, aka translation. Then the reflected photon hits the opposite inner wall and effectively stops the cavity's movement again. But: Out metal box moved for a nanosecond or so, and hence the box has experienced a translational movement. At the same time, conservation of momentum was not violated: It's time-averaged ZERO. Still, we got a translation.

What do you think?

1) In your model you assume that one end of the cavity is porous to photons but the other end is reflective

2) See previous post:  http://forum.nasaspaceflight.com/index.php?topic=29276.msg1256192#msg1256192)

Whether the photons could come from the outside and be reflected or whether they come from the inside and then make it out of the drive, the fundamental fact is that even a photon rocket has orders of magnitude lower SpecificForce=thrust/InputPower than the reported experimental measurements
« Last Edit: 09/20/2014 03:32 PM by Rodal »

Offline CW

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Re: EM Drive Developments
« Reply #804 on: 09/20/2014 03:29 PM »
Here is a little thought experiment:

Imagine a perfectly reflective metal cavity, into which a photon from the outside is injected through a tiny hole in the cavity walls. When the photon hits the inner wall for the first time, it imparts 2x its impulse on the cavity (when being absorbed and then emitted again). Thus, the cavity gains a little momentum and moves a little bit into the photon's original impulse direction, aka translation. Then the reflected photon hits the opposite inner wall and effectively stops the cavity's movement again. But: Out metal box moved for a nanosecond or so, and hence the box has experienced a translational movement. At the same time, conservation of momentum was not violated: It's time-averaged ZERO. Still, we got a translation.

What do you think?

1) In your model you assume that one of the cavity is porous to photons but the other end is reflective

2) As per previous posts, even a photon rocket has specific force orders of magnitude lower than the reported values

Actually, in my model there is exactly one tiny hole in the whole cavity through which the photon(s) can be shot into. Also, a photon rocket only uses each photon once. In my model, one photon would be recycled by, say, 10^9 times. Orders of magnitude larger than a measly photon rocket :p . And this thing wouldn't work as a rocket at all - no impulse is imparted, but a translation. Translations don't violate conservation of momentum ;) .
« Last Edit: 09/20/2014 03:33 PM by CW »
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Offline Notsosureofit

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Re: EM Drive Developments
« Reply #805 on: 09/20/2014 03:31 PM »
I think the original photons momentum was transferred to the cavity.  The doppler shifted reflected photon is what now balances  forever in a lossless cavity.

Online RonM

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Re: EM Drive Developments
« Reply #806 on: 09/20/2014 03:47 PM »
I think the original photons momentum was transferred to the cavity.  The doppler shifted reflected photon is what now balances  forever in a lossless cavity.

Yes, the original photon adds to the system. After that, any reemitted photons zipping around are part of the system.

Offline CW

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Re: EM Drive Developments
« Reply #807 on: 09/20/2014 04:01 PM »
I think the original photons momentum was transferred to the cavity.  The doppler shifted reflected photon is what now balances  forever in a lossless cavity.

Yes, the original photon adds to the system. After that, any reemitted photons zipping around are part of the system.

The point, that I wanted to make, was that a bouncing photon (that was injected externally) in a perfectly reflective cavity only gives the illusion of a continuous movement. In actuality, it is a go-stop-go-stop.. kind of motion.
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Offline Notsosureofit

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Re: EM Drive Developments
« Reply #808 on: 09/20/2014 04:09 PM »
Not really, the photon speed is much higher than the speed of sound in the cavity walls.

Online aero

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Re: EM Drive Developments
« Reply #809 on: 09/20/2014 05:17 PM »
Well, what if it were electrons instead of photons? Somehow (help me out here) electrons originate in the dielectric, and are scattered in all directions by the high Q RF wave magnetic/electric fields. Electrons all speed to the conducting cavity walls and of course some of them travel axially toward the base plate. In the travel toward the base plate they encounter the resonating RF waves, one set of magnetic/electric fields resonating perpendicular to the end plates, another resonating parallel to the base plate.

Now will the magnetic/electric fields of the RF wave turn the direction of travel of the electrons such that they never reach the base plate but instead are turned to the side and neutralized on the metallic sides of the cavity? In that situation the side forces would average to zero but the end-to-end forces would transfer momentum to the thruster body.

Ok - the momentum originates in the electron acceleration from the dielectric by the RF energy which reacts with the cavity but are turned by the RF energy at the base which does not react with the cavity. hmm.
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Online Rodal

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Re: EM Drive Developments
« Reply #810 on: 09/20/2014 05:29 PM »
Dr. White's hypothesis is precisely that electron/positron pairs of virtual particles emerge from the Quantum Vacuum and the EM drive behaves as a MagnetoHydroDynamics plasma.   Frobnicat, others and I have raised questions about that hypothesis.

It is a fact that has to be addressed by any  (classical or exotic)  explanation that:

No dielectric resonator = No measured thrust

Off center-of-mass position of dielectric resonator --> direction in which thrust is measured

Electrical Field in the dielectric resonator is orders of magnitude >> than in the rest of the cavity
« Last Edit: 09/20/2014 05:38 PM by Rodal »

Online Rodal

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Re: EM Drive Developments
« Reply #811 on: 09/20/2014 05:42 PM »
Well, what if it were electrons instead of photons? Somehow (help me out here) electrons originate in the dielectric, and are scattered in all directions by the high Q RF wave magnetic/electric fields. Electrons all speed to the conducting cavity walls and of course some of them travel axially toward the base plate. In the travel toward the base plate they encounter the resonating RF waves, one set of magnetic/electric fields resonating perpendicular to the end plates, another resonating parallel to the base plate.

Now will the magnetic/electric fields of the RF wave turn the direction of travel of the electrons such that they never reach the base plate but instead are turned to the side and neutralized on the metallic sides of the cavity? In that situation the side forces would average to zero but the end-to-end forces would transfer momentum to the thruster body.

Ok - the momentum originates in the electron acceleration from the dielectric by the RF energy which reacts with the cavity but are turned by the RF energy at the base which does not react with the cavity. hmm.

If that would work, wouldn't an Electron gun be more effective ? ( An electron emitter that produces a narrow, collimated electron beam as in cathode ray tubes (CRTs), used in older television sets, computer displays, and oscilloscopes. )  I disposed recently of a humongous high-definition CRT Sony TV (one of the last ones made) but I kept its electron gun  :)
« Last Edit: 09/20/2014 06:22 PM by Rodal »

Online aero

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Re: EM Drive Developments
« Reply #812 on: 09/20/2014 06:27 PM »
I prepared this post while you were making your post. Yes, in answer to your question.

Dr. White's hypothesis is precisely that electron/positron pairs of virtual particles emerge from the Quantum Vacuum and the EM drive behaves as a MagnetoHydroDynamics plasma.   Frobnicat, others and I have raised questions about that hypothesis.

It is a fact that has to be addressed by any  (classical or exotic)  explanation that:

No dielectric resonator = No measured thrust

Off center-of-mass position of dielectric resonator --> direction in which thrust is measured

Electrical Field in the dielectric resonator is orders of magnitude >> than in the rest of the cavity

Yes but Dr. White's theory comes up short with the assumption of electron/positron pairs. The positron, as I read the history of the theory development, is an electron moving backward in time postulated in order that the math will work to avoid infinite energies. That is, it is an artifact while the electron from the quantum vacuum is real. But irrespective of Dr. White's theory, I am postulating a 17 watt electron current originating in the dielectric and flowing to the cavity walls. This is like a CRT except instead of focusing the electron beam, the magnetic/electric fields within the cavity scatter the beam away from the base plate.

Newton's laws apply in my case, so for this to work, F = ma must be satisfied with F on the order of 50 - 100 muN and a single electron rest mass ~9 x 10^-31 kg. Of course a in this case is quite high. Guess the electron velocity is 3 x 10^6 m/s which is reasonable and non-relativistic. That gives a > 3.93701E+13 m/s^2 where the number is calculated assuming uniform acceleration across the cavity, dielectric to base plate. The result is that there must be 2.54E+12 electrons flowing.

But I will need to research to discover how to convert these flowing electrons to power. Power = 17 watts.
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Online aero

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Re: EM Drive Developments
« Reply #813 on: 09/20/2014 06:35 PM »
Maybe I answered to quickly. What is the electron generation efficiency of a heated filament in a CRT compared to the electron generation/creation efficiency of the dielectric with the RF energy imposed? I don't know which would create more electrons using 17 watts of power.
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Online Rodal

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Re: EM Drive Developments
« Reply #814 on: 09/20/2014 07:44 PM »
Some data:

Electric field shown in Fig. 14, titled "Cross section of test article (left) and close up of fields in RF drive pipe (right)", from the <<Computer modeling of the electric field within the pillbox and beam pipe (using COMSOL Multiphysics® software>>  of page 10 of 2014 JPC paper co-authored by Brady, White, et.al.

Maximum dissipated power in ("Teflon") PTFE dielectric resonator for Cannae device :

DissipatedPower = 2 Pi f (E^2) (permittivity of free space) (epsilon')(tan delta)

Taking the

maximum value of the Electric Field shown in Fig. 14, p.10, as 4.7189*10^4 V/m , and the given

frequency of 935 MHz, it immediately follows (for the Teflon PTFE dielectric resonator) that:


DissipatedPower per unit volume [W/m^3] = 2 Pi (935*10^6 1/s) (( 4.7189*10^4)^2) (8.85418782*10^(-12)) (2.1)(0.0003)

DissipatedPower per unit volume (in the dielectric resonator) =  72973  W/m^3 = 0.0729 W/cm^3

NonDissipatedPower per unit volume (in the dielectric resonator)~  243 W/cm^3

_____________________________________

Image from "Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum" by David A. Brady*, Harold G. White†, Paul March‡, James T. Lawrence§, and Frank J. Davies**, July 28-30, 2014, Cleveland, OH, AIAA 2014-4029, Propulsion and Energy Forum, 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

the article notes: "This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States." (Also see: http://en.wikipedia.org/wiki/Copyright_status_of_work_by_the_U.S._government) as posted in http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
« Last Edit: 09/20/2014 08:09 PM by Rodal »

Online RotoSequence

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Re: EM Drive Developments
« Reply #815 on: 09/20/2014 07:50 PM »
DissipatedPower per unit volume =  72973  W/m^3 = 0.0729 W/cm^3

Is that just waste heat, just thrust, or waste heat and thrust?
« Last Edit: 09/20/2014 07:51 PM by RotoSequence »

Online Rodal

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Re: EM Drive Developments
« Reply #816 on: 09/20/2014 07:51 PM »
DissipatedPower per unit volume =  72973  W/m^3 = 0.0729 W/cm^3

Is that just waste heat, or is that waste heat and thrust?


This 0.0729 W/cm^3 is dissipated heat, that turns into an increase in temperature.   No comment about thrust.
« Last Edit: 09/20/2014 08:02 PM by Rodal »

Online aero

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Re: EM Drive Developments
« Reply #817 on: 09/20/2014 08:00 PM »
Ok, I used 17 watts in the following, so it will need to be reduced a little to allow for the dissipated heat power.

I calculated that the number of electrons,  2.54E+12 from before carry a charge of 4.07E-07 C so the current flow is 4.07E-07 amps. 17 watts of power, P = I*V gives Voltage across the cavity of 41.8 MV . This is a little higher (factor of 10 higher) than the striking voltage in air so glow discharge might be a problem.

Other than that, does physics allow this mechanism?

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Online Rodal

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Re: EM Drive Developments
« Reply #818 on: 09/20/2014 08:06 PM »
Ok, I used 17 watts in the following, so it will need to be reduced a little to allow for the dissipated heat power.

I calculated that the number of electrons,  2.54E+12 from before carry a charge of 4.07E-07 C so the current flow is 4.07E-07 amps. 17 watts of power, P = I*V gives Voltage across the cavity of 41.8 MV . This is a little higher (factor of 10 higher) than the striking voltage in air so glow discharge might be a problem.

Other than that, does physics allow this mechanism?

1) Thank you for performing calculations and providing numbers  :)
2) I have to think about this.
3) I look forward to other readers providing comments, performing their own calculations and cross-checking.

Offline JohnFornaro

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Re: EM Drive Developments
« Reply #819 on: 09/20/2014 08:22 PM »
I saw the talk about Dark Hamsters, and shall be going back to my beer soon.  Still:

In my model, one photon would be recycled by, say, 10^9 times.

Let's not, say, shall we?  You have given no cause to make that assumption.
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