Author Topic: EM Drive Developments Thread 1  (Read 796163 times)

Offline Rodal

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Re: EM Drive Developments
« Reply #840 on: 09/21/2014 03:55 AM »
So, bottom line is, "Yes, there is a possibility of the release of a large number of real electrons within the dielectric end of the thruster, via an electron avalanche." Such an electron avalanche was not a design feature of the thruster. And further, we know nothing definitive about the tapered cavity thruster.

Is there another mechanism which may have released electrons numbering in the ball park of 10^13 electrons/second? Note that is not a large number of electrons as such things go. The electron lifetime would be on the order of 10^-8 to 10^-9 seconds so at any given instant there only a few 10's of thousands of electrons within the cavity. That is a very small number as plasma densities go. Isn't it reasonable to assume that some small number of air molecules ionized within the cavity to create that small number of electrons?

Of course ionized air would result in positively charged ions also but if the cause of the electron acceleration was the magnetic field of the RF wave, then it would not discriminate between ion and electron acceleration forces. Ions would have a larger gyro radius around the magnetic field lines, and gyrate in the opposite direction (?) from the electrons but ultimately they would end up in the same place I think.

I'm on a roll here so I'd better stop before I go stupid on you.

It depends on a lot of things, like the amount of polarization that is achieved in the PTFE dielectric resonator.

This we know: there was no measurable thrust when they removed the PTFE dielectric resonator and the direction of the thrust correlates with the location and polarization of the dielectric resonator.

Offline aero

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Re: EM Drive Developments
« Reply #841 on: 09/21/2014 04:30 AM »
So, bottom line is, "Yes, there is a possibility of the release of a large number of real electrons within the dielectric end of the thruster, via an electron avalanche." Such an electron avalanche was not a design feature of the thruster. And further, we know nothing definitive about the tapered cavity thruster.

Is there another mechanism which may have released electrons numbering in the ball park of 10^13 electrons/second? Note that is not a large number of electrons as such things go. The electron lifetime would be on the order of 10^-8 to 10^-9 seconds so at any given instant there only a few 10's of thousands of electrons within the cavity. That is a very small number as plasma densities go. Isn't it reasonable to assume that some small number of air molecules ionized within the cavity to create that small number of electrons?

Of course ionized air would result in positively charged ions also but if the cause of the electron acceleration was the magnetic field of the RF wave, then it would not discriminate between ion and electron acceleration forces. Ions would have a larger gyro radius around the magnetic field lines, and gyrate in the opposite direction (?) from the electrons but ultimately they would end up in the same place I think.

I'm on a roll here so I'd better stop before I go stupid on you.

It depends on a lot of things, like the amount of polarization that is achieved in the PTFE dielectric resonator.

This we know: there was no measurable thrust when they removed the PTFE dielectric resonator and the direction of the thrust correlates with the location and polarization of the dielectric resonator.

That's fine then. Due to the small number of electrons needed, we don't really need an avalanche, just some "modest" level of ionization within the dielectric resonator. Unfortunately, didn't I read that they have plans to change the dielectric for the IV&V thruster models?
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Offline Rodal

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Re: EM Drive Developments
« Reply #842 on: 09/21/2014 08:44 AM »
That's fine then. Due to the small number of electrons needed, we don't really need an avalanche, just some "modest" level of ionization within the dielectric resonator. Unfortunately, didn't I read that they have plans to change the dielectric for the IV&V thruster models?

<<Moving forward, a new tapered cavity RF resonance system has been designed and characterized using COMSOL® with Q-thruster physics. Figure 26 shows some of the COMSOL® analysis with the higher performance dielectric resonator clearly visible. This resonator material has a relative permittivity that is an order of magnitude higher than our current tapered cavity test article resonator material. The lessons learned with antenna design and location have been factored in and the design of both the drive and sense antennas have been explicitly optimized to excite the RF thruster at the target frequency and mode (e.g., the optimal location has been analytically determined). The thrust performance of this next generation tapered test article has been analytically determined to be in the 0.1 newton per kilowatt regime.>>

Offline JohnFornaro

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Re: EM Drive Developments
« Reply #843 on: 09/21/2014 01:37 PM »
[quoting another]This resonator material has a relative permittivity that is an order of magnitude higher than our current tapered cavity test article resonator material...
[/quote]

Compressed hummingbird wings? (Which is real)  Ground unicorn horns? (Which is fake)

Always a mysterious special sauce, it would seem.

Seriously tho, you guyz have lost me with the sidetrack about your all's analysis of the dimensionless PTFE and the nature of the Comsol modeling, now expected to accomodate a new material.  Like I always say:

Ausência de evidência é evidência de ausência de evidência.

But enough talk about you.  Let's talk about GoatGuy's math.  I don't think it's correct.  Lemme try again.

The second case is a bit harder to prove, but still within reach of ordinary algebra:

Ek = ½mV²   ... kinetic energy as a function of V, again.
V = at ... again, now substitute
Ek = ½ma²t²  and remembering that [F = ma]...
Ek = F²t²/(2m)

If F = ma, then F^2 = (ma)^2 = m^2a^2, correct?

GoatGuy doesn't write that.  Instead he writes:

Quote from: goatGuy
Ek = ½ma²t²

How did he get from Ek = ½ma²t² to Ek = F²t²/(2m)?

Apenas dizendo.
Sometimes I just flat out don't get it.

Offline Rodal

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Re: EM Drive Developments
« Reply #844 on: 09/21/2014 02:02 PM »
you guyz have lost me
Apenas dizendo.

For those having difficulties following the recent discussion between aero, RotoSequence, Notsosureofit and me, we have been analyzing the possibility (among many possible explanations) that the anomalous thrust experimental results may have been due to (unintended) field emission of electrons from the ("Teflon") PTFE dielectric resonator (acting as an unintended electron rocket with Teflon acting as the propellant). 

If such an explanation for the experimental results would be true, it would mean that the thrust was not at all due to the Quantum Vacuum or to Woodward's transient mass effects, and the dreams of a quick trip to the moons of Jupiter and Saturn using this type of propulsion would be thoroughly dashed.  Comprende ?
« Last Edit: 09/21/2014 02:23 PM by Rodal »

Offline JohnFornaro

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Re: EM Drive Developments
« Reply #845 on: 09/21/2014 02:21 PM »
Apenas dizendo.

For those having difficulties following the recent discussion ....  Comprende ?

I do follow the gist of the conversation.

What I don't follow are the various specifics.  Which is fine in principle, even as it requires my trust in your all's line of argument. 

The idiot in me sees the genius in you.

[Edit: From the snappy comeback department.   Which is not what namaste means, but close enough.]

But what about GoatGuy's math?  I spent four beers and an hour going over his post yesterday evening, and I choked at the point I mention above.
« Last Edit: 09/21/2014 11:40 PM by JohnFornaro »
Sometimes I just flat out don't get it.

Offline Rodal

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Re: EM Drive Developments
« Reply #846 on: 09/21/2014 02:31 PM »

How did he get from Ek = ½ma²t² to Ek = F²t²/(2m)?

Apenas dizendo.

The force equation (from Newton's 2nd Law) is F=ma, where "F" is the force, "m" is the mass and "a" is the acceleration. Hence the acceleration is a=F/m, and all one has to do is to substitute the acceleration expression a=F/m into the Kinetic Energy expression Ek = (½)ma²t² as follows:

Ek = (½)ma²t² = (½)m(F/m)²(t²)= (½)(m/m²)(F²)(t²)=(½)(1/m)(F²)(t²)= F²t²/(2m)

So, no problemo

_________
PS:
A) I have not checked GoatGuy's derivation further than this, but I can make the following trivial comment:


B) It is understood that there is an (inconsequential) assumption in GoatGuy's derivation (http://forum.nasaspaceflight.com/index.php?topic=29276.msg1254645#msg1254645). This assumption does not affect what he addresses (thrust propulsion and energetics).  The assumption is that the velocity is a linear function of time with the constant velocity term = 0,

[GoatGuy]  <<V = at  ... delta V as function of acceleration and time assuming constant)>>


 such that, simply, acceleration=velocity*time.  We might as well state this clearly (even though it is inconsequential) [where I use "v" for velocity instead of GoatGuy's "V" to comply with John's request].

This is easy to show, of course:

x=displacement, v=velocity, a= acceleration

For x=A t² + B t + C, then v=dx/dt= 2 A t + B and a=dv/dt = 2 A, hence

v=a*t + B

(In GoatGuy's derivation the constant velocity term B is zero).

If the velocity would be a higher order function of  time, for example such as an acceleration that varies linearly with time:

For x=D t3 +A t² + B t + C, then v=dx/dt=3 D t² + 2 A t + B and a =dv/dt= 6 D t + 2 A, hence

v=a*t + B - 3 D t²

(GoatGuy derivation is for both the constant velocity term B and the higher order velocity term D to be zero).  His derivation applies to a displacement increasing as the square of time (constant acceleration) without any linear time term (uniform velocity = 0) or higher order (cubic or higher) terms in time.  His derivation is for:

a displacement expressible as follows x=A t² + C  and hence a velocity v= 2 A t and constant acceleration
a = 2 A = v*t
« Last Edit: 09/21/2014 05:13 PM by Rodal »

Offline Rodal

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Re: EM Drive Developments
« Reply #847 on: 09/21/2014 02:48 PM »
...

John, you wanted to have a sidebar on Woodard's derivation.  If you still want to do this, are there any Woodward-derivation-experts on this thread that could answer questions regarding Woodward's derivation?  Because if there are no people on this thread willing and able to answer Woodward-derivation-questions, it looks like such a thread would be a debate where one of the parties doesn't show up...

Solo dicendo...
« Last Edit: 09/21/2014 02:49 PM by Rodal »

Offline aero

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Re: EM Drive Developments
« Reply #848 on: 09/21/2014 04:42 PM »
you guyz have lost me
Apenas dizendo.

For those having difficulties following the recent discussion between aero, RotoSequence, Notsosureofit and me, we have been analyzing the possibility (among many possible explanations) that the anomalous thrust experimental results may have been due to (unintended) field emission of electrons from the ("Teflon") PTFE dielectric resonator (acting as an unintended electron rocket with Teflon acting as the propellant). 

If such an explanation for the experimental results would be true, it would mean that the thrust was not at all due to the Quantum Vacuum or to Woodward's transient mass effects, and the dreams of a quick trip to the moons of Jupiter and Saturn using this type of propulsion would be thoroughly dashed.  Comprende ?

Well, not quite. The electron supply could be deliberately designed into the thruster using a hot cathode for example. The question becomes, is the thruster reactionless or not? If the electrons somehow penetrate the base plate and exit the system then the RF resonate cavity thruster becomes nothing but an interesting electron thruster using electrons as the reaction mass. It still has a very good Isp but charge imbalance would quickly eliminate the thrust in space. It would show very good performance when tested in a grounded vacuum chamber. But we can reasonably expect that the electron stream exiting the cavity would be detected in testing.

If instead the electrons somehow do not exit the cavity, it becomes a reactionless thruster which will allow the benefits of the high Isp of the electron beam without the problem of charge build-up on the cavity. This would be a new and to my mind very useful class of thruster.

This leads to my question, "How can the RF waves in the cavity turn the high speed electrons from the axial direction to the sideways direction to impact the side walls without an action in the axial direction?"
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Offline Rodal

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Re: EM Drive Developments
« Reply #849 on: 09/21/2014 05:17 PM »

Well, not quite. The electron supply could be deliberately designed into the thruster using a hot cathode for example. The question becomes, is the thruster reactionless or not? If the electrons somehow penetrate the base plate and exit the system then the RF resonate cavity thruster becomes nothing but an interesting electron thruster using electrons as the reaction mass. It still has a very good Isp but charge imbalance would quickly eliminate the thrust in space. It would show very good performance when tested in a grounded vacuum chamber. But we can reasonably expect that the electron stream exiting the cavity would be detected in testing.

If instead the electrons somehow do not exit the cavity, it becomes a reactionless thruster which will allow the benefits of the high Isp of the electron beam without the problem of charge build-up on the cavity. This would be a new and to my mind very useful class of thruster.

This leads to my question, "How can the RF waves in the cavity turn the high speed electrons from the axial direction to the sideways direction to impact the side walls without an action in the axial direction?"

Yes, that's better stated, thank you.  The field emission of electrons (from the PTFE dielectric resonator) classical explanation as an electron rocket using the PTFE as the propellant implies that the cavity is leaky enough (at the opposite end of the PTFE dielectric resonator) to allow axial escape of the electrons.   If the experimental measurements were indeed due to any propulsion (a significant assumption in need of verification) I find the idea of real electrons being responsible for it more plausible than virtual electron/positron pairs from the Quantum Vacuum being responsible.

I agree that there are big problems with this explanation, and it appears as another desperate attempt at explaining the experimental results: A) the field emission of electrons when calculations show that the Electric Field is two orders of magnitude lower than the dielectric breakdown, B) the cavity was not tested in a vacuum, since axial trajectory of electrons would need a vacuum, and C) it is unlikely that the opposite end is porous to electrons.

I don't have an answer to your question.  I don't understand why is there a need for "RF waves in the cavity [to] turn the high speed electrons from the axial direction to the sideways direction", since we don't know what is on the interior surface of the circuit board (large diameter) end, and axial exit (perpendicular to the large diameter surface) is needed for axial propulsion.
« Last Edit: 09/21/2014 05:32 PM by Rodal »

Offline frobnicat

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Re: EM Drive Developments
« Reply #850 on: 09/21/2014 05:24 PM »
This leads to my question, "How can the RF waves in the cavity turn the high speed electrons from the axial direction to the sideways direction to impact the side walls without an action in the axial direction?"

Initially didn't understand what you were aiming at with your electron gun, then your drawing rung my momentum conservation breaking alarm, now this is clearer with this phrase.

Answer : they can't. Action, reaction. If a field turns a particle flow sideways so as to zero its axial momentum, then the axial momentum of the flow has to be imparted to another part of the system. There is no fundamental difference between a long range field mediated momentum exchange and contact forces, consider the thought experiment where the electrons are a water jet, and the field is a solid "conical ramp" (er, quarter circle revolution surface ?) that smoothly throws the jet sideways in a plane perpendicular to the jet. This deviating ramp would be imparted a thrust exactly equal in magnitude and opposite to the thrust of the water jet at its emission. If the ramp and the emitting nozzle are mechanically linked then the system will always have 0 net thrust overall. That is : without rewriting all known physics.

also from a more practical point of view : there can't be smooth electron trajectories like that unless in a good vacuum, the later results (anomalous thrust...) not being in such vacuum.

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #851 on: 09/21/2014 05:43 PM »
Just an update from the pictures:  There is circuit board material on both ends of the truncated cone.  The second layer on the large end seems to be just part of the mount.

Does anyone know where the dielectric material is in the cone ?

Offline aceshigh

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Re: EM Drive Developments
« Reply #852 on: 09/21/2014 05:45 PM »
  Comprende ?

not sure if this was spanish or portuguese (like in the last JohnFornaro posts). If it´s portuguese, there are two Es there... "compreende".

but please, follow on. I have not heard portuguese mixed with propellantless propulsion since reading Orson Scott Card's "Speaker to the Dead".  :D :D

at Rodal, regarding both the possibility of the teflon acting as a thruster and the derivation of Woodward's equations, I guess Paul March would be able to answer... I guess those questions would not be under his NDA with NASA.

Offline Rodal

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Re: EM Drive Developments
« Reply #853 on: 09/21/2014 05:57 PM »
  Comprende ?

not sure if this was spanish or portuguese (like in the last JohnFornaro posts).

It was meant as neither Spanish nor Portuguese.  It was meant as Italian.  Any resemblance to Spanish or Portuguese is a coincidence due to the fact that they are all Romance languages  ;)

But from now on I will use capisce, so that there is no confusion...

Lei capisce ?

« Last Edit: 09/21/2014 06:26 PM by Rodal »

Offline Rodal

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Re: EM Drive Developments
« Reply #854 on: 09/21/2014 06:02 PM »
Just an update from the pictures:  There is circuit board material on both ends of the truncated cone.  The second layer on the large end seems to be just part of the mount.

Does anyone know where the dielectric material is in the cone ?

How do you know that there is circuit board material on the small diameter end of the Frustum (truncated cone) ? (the color and smoothness looks very different from the other end)

Take a look at the images below that show the position of the (annular shaped) dielectric resonator:
« Last Edit: 09/21/2014 06:08 PM by Rodal »

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #855 on: 09/21/2014 06:08 PM »
I have this material.  I think the small end looks different because of the lighting, although some of the pieces I have are darker or lighter than others.

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #856 on: 09/21/2014 06:16 PM »
Frustum Dielectric looks like a simulation of a superconducting cavity.  Did the model use a realistic copper wall w/ complex n ??

Offline Rodal

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Re: EM Drive Developments
« Reply #857 on: 09/21/2014 06:23 PM »
Frustum Dielectric looks like a simulation of a superconducting cavity.  Did the model use a realistic copper wall w/ complex n ??

There is no distinction between the cavity's interior and the (copper ?) metal wall in the COMSOL finite element analysis display of the Electric Field, so my reading of this is that the metal wall was modeled as a Boundary Condition for the field.

« Last Edit: 09/21/2014 06:25 PM by Rodal »

Offline Rodal

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Re: EM Drive Developments
« Reply #858 on: 09/21/2014 06:43 PM »
Frustum Dielectric... model use a realistic copper wall w/ complex n ??
See this COMSOL finite element demonstration paper http://www.michelsencentre.com/doc/pdf%20dokumenter/comsol/comsol_acdc_rf_42a.pdf  for example

Offline aero

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Re: EM Drive Developments
« Reply #859 on: 09/21/2014 07:35 PM »
Well, if the RF field can not turn the electron stream without a reacting force, then that leaves

1. Dr. White's idea of the electrons/protons appearing and disappearing from/to the quantum vacuum, and
2. The alternative of the real electrons disappearing into the quantum vacuum.

The first idea has been discounted by critics. The second idea has not been put forward, to my knowledge.

Of course there are the ideas put forth by Shayer, and by the Chinese experimental group, as well as new ideas that might be held Boeing and Cannae groups.
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