Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1797263 times)

Offline SeeShells

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Todd

Todd,

Any EMDrive theory must show the direction of the dielectric generated Force (Small to Big) at 180 deg opposite the non dielectric case (Big to Small) and the dielectric Force to be much weaker than the non dielectric case.

Can your theory do that?

Traveller, is it true that a tapered waveguide with a dielectric insert in the small end will thrust towards the big end, and that the same tapered waveguide without the dielectric will thrust toward the small end?  Do I have that right?

With that in mind, how does Shawyer's variable group velocity ==> variable radiation pressure theory explain this flipping thrust direction?

The flipped Force direction is correct as per published experimental data from 4 experimenters as attached

As far as I know, Shawyer never addressed the dielectric results in his theory, other than in the 2 relevant UK patents attached.

So the field is wide open for you and others to have a go. Good luck.

BTW your claimed that Shawyer's claim that variable group velocity (variable Guide Wavelength) generates variable radiation Force is a theory is not correct. Cullen 15 (attached) and waveguide physics proves it is correct.

If you don't understand that please check out how Group Velocity and Group Wavelength are related Vg = c * (Lambda0 / Lambdag) Lambdag is the Guide Wavelength and it changes as the tapered waveguide diameter changes as the EM wave passes along the tapered waveguide.
Were is the reaction in the graph, only thrust is shown. Terminology defining thrust, reaction, of a force, it's all messed up and confusing. Needs to be cleaned up to make sense. MHO

Shell

Offline TheTraveller

Todd

Todd,

Any EMDrive theory must show the direction of the dielectric generated Force (Small to Big) at 180 deg opposite the non dielectric case (Big to Small) and the dielectric Force to be much weaker than the non dielectric case.

Can your theory do that?

Traveller, is it true that a tapered waveguide with a dielectric insert in the small end will thrust towards the big end, and that the same tapered waveguide without the dielectric will thrust toward the small end?  Do I have that right?

With that in mind, how does Shawyer's variable group velocity ==> variable radiation pressure theory explain this flipping thrust direction?

The flipped Force direction is correct as per published experimental data from 4 experimenters as attached

As far as I know, Shawyer never addressed the dielectric results in his theory, other than in the 2 relevant UK patents attached.

So the field is wide open for you and others to have a go. Good luck.

BTW your claimed that Shawyer's claim that variable group velocity (variable Guide Wavelength) generates variable radiation Force is a theory is not correct. Cullen 15 (attached) and waveguide physics proves it is correct.

If you don't understand that please check out how Group Velocity and Group Wavelength are related Vg = c * (Lambda0 / Lambdag) Lambdag is the Guide Wavelength and it changes as the tapered waveguide diameter changes as the EM wave passes along the tapered waveguide.
Were is the reaction in the graph, only thrust is shown. Terminology defining thrust, reaction, of a force, it's all messed up and confusing. Needs to be cleaned up to make sense. MHO

Shell

Forget what you think the labels mean. Read the table in the middle side. Shows in which direction (Reaction or Thrust) Force is generated for each case.

I will admit it could be made clearer.

Try the attached.
« Last Edit: 07/15/2015 04:05 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
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Offline wallofwolfstreet

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Todd

Todd,

Any EMDrive theory must show the direction of the dielectric generated Force (Small to Big) at 180 deg opposite the non dielectric case (Big to Small) and the dielectric Force to be much weaker than the non dielectric case.

Can your theory do that?

Traveller, is it true that a tapered waveguide with a dielectric insert in the small end will thrust towards the big end, and that the same tapered waveguide without the dielectric will thrust toward the small end?  Do I have that right?

With that in mind, how does Shawyer's variable group velocity ==> variable radiation pressure theory explain this flipping thrust direction?

The flipped Force direction is correct as per published experimental data from 4 experimenters as attached

As far as I know, Shawyer never addressed the dielectric results in his theory, other than in the 2 relevant UK patents attached.

So the field is wide open for you and others to have a go. Good luck.

BTW your claimed that Shawyer's claim that variable group velocity (variable Guide Wavelength) generates variable radiation Force is a theory is not correct. Cullen 15 (attached) and waveguide physics proves it is correct.

If you don't understand that please check out how Group Velocity and Group Wavelength are related Vg = c * (Lambda0 / Lambdag) Lambdag is the Guide Wavelength and it changes as the tapered waveguide diameter changes as the EM wave passes along the tapered waveguide.

The first of your linked patents, GB 2229865A, has the following quote from Shawyer.  the patent is for a cylindrical waveguide that has a dielectric insert at one end. 

Quote from: Shawyer
The force resulting from reflections of the guided electromagnetic waves in the end section containing the electrical material will be greater than the force resulting from reflections in the air or vacuum filled end section.  The difference between these forces will give rise to a resultant thrust on the unit.

To me that reads like Shawyer, at least back in 1988, believed that the thrust would be towards the dielectric filled section.  Assuming he was using variable group velocity as an explanation for thrust, do you or anyone else know of how the dielectric insert affects groups velocity?  And if the insert doesn't affect group velocity, is this design effectively operating off a different principle than a tapered cavity does?   
« Last Edit: 07/15/2015 04:00 PM by wallofwolfstreet »

Offline Rodal

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...

Your theory that Group Velocity is not the velocity of momentum inside a waveguide and that the Group Velocity doesn't vary with diameter change is not correct.
Your complete misrepresentation of what I wrote stands most prominent among your frequent misrepresentations.   I am glad that others can read and interpret for themselves what I wrote ( http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404987#msg1404987 ) without your complete mis-quotation.
« Last Edit: 07/15/2015 04:04 PM by Rodal »

Offline TheTraveller

...

Your theory that Group Velocity is not the velocity of momentum inside a waveguide and that the Group Velocity doesn't vary with diameter change is not correct.
Your complete misrepresentation of what I wrote stands most prominent among your frequent misrepresentations.   I am glad that others can read and interpret for themselves what I wrote ( http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404987#msg1404987 ) without your complete mis-quotation.

You have denied variable Group Velocity since I 1st came here.

Are you now reversing your position and accepting:

1) Group velocity is the velocity the EM waves momentum is travelling at, inside the waveguide, when it hits the end plate?

2) Group velocity varies as the cavity diameter varies and is different upon hitting each end plate?

3) Because of the different Group Velocity at each end plate, the Force generated as the EM wave bounces off the end plate varies as to the EM waves Group Velocity?

The above 3 statements are what Cullen, Shawyer and Prof Yang claim happens.

Do you now agree with them?
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline SeeShells

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This is interesting!!!

Attractive photons in a quantum nonlinear medium

http://www.nature.com/nature/journal/v502/n7469/full/nature12512.html
The fundamental properties of light derive from its constituent
particles—massless quanta (photons) that do not interact with one
another. However, it has long been known that the realization of
coherent interactions between individual photons, akin to those
associated with conventional massive particles, could enable a wide
variety of novel scientific and engineering applications2,3. Here we
demonstrate a quantum nonlinear medium inside which individual
photons travel as massive particles with strong mutual attraction,
such that the propagation of photon pairs is dominated by a twophoton
bound state4–7. We achieve this through dispersive coupling
of light to strongly interacting atomsin highly excited Rydberg states.
We measure the dynamical evolution of the two-photon wavefunction
using time-resolved quantum state tomography, and demonstrate
a conditional phase shift8 exceeding one radian, resulting in
polarization-entangled photon pairs. Particular applications of this
technique include all-optical switching, deterministic photonic
quantum logic and the generation of strongly correlated states of
light...
http://www.rle.mit.edu/eap/documents/Nature_attractive_photons.pdf

edit better link... a key.
« Last Edit: 07/15/2015 04:26 PM by SeeShells »

Offline DaCunha

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I have a question:

What is the most powerful microwave source that is available to private persons?
And what is the maximum intensity that, say, copper can withstand without melting, exploding or whatever?

Could we just buy a 1 MW+ microwave source build a frustrum resonator and see what happens?

After seeking cover of course.

Let us find a bored millionaire.

This can't be too expensive. We don't have to optimize the system, which would become expensive at long term of course.

Just apply the maximum power to a frustrum and check what will happen.
« Last Edit: 07/15/2015 05:38 PM by DaCunha »

Offline ElizabethGreene

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Inside a microwave waveguide Cullen has shown the bounce Force generated is reletative to the EM waves .....

May I have the title of this book or article?  Was it in Modern Radio Science 1988?  That's the only book I can find by him.

Thanks.

Offline TheTraveller

Inside a microwave waveguide Cullen has shown the bounce Force generated is reletative to the EM waves .....

May I have the title of this book or article?  Was it in Modern Radio Science 1988?  That's the only book I can find by him.

Thanks.

Cullen's equation 15 (2 different copies of his paper attached) is the basis for the microwave waveguide bounce Force calculation in both Shawyer's work and in Prof Yang's work. Please note the Force is related to the EM waves Lambda / Lambdag (Guide Wavelength), which is virtually the same thing as c / Group Velocity.
« Last Edit: 07/15/2015 05:50 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline SeeShells

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I have a question:

What is the most powerful microwave source that is available to private persons?
And what is the maximum intensity that, say, copper can withstand without melting, exploding or whatever?

Could we just buy a 1 MW+ microwave source build a frustrum resonator and see what happens?

After seeking cover of course.

Let us find a bored millionaire.

This can't be too expensive. We don't have to optimize the system, which would become expensive at long term of course.

Just apply the maximum power to a frustrum and check what will happen.

Ask the Myth Busters. They like blowing things up. :D

Offline WarpTech

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Todd

Todd,

Any EMDrive theory must show the direction of the dielectric generated Force (Small to Big) at 180 deg opposite the non dielectric case (Big to Small) and the dielectric Force to be much weaker than the non dielectric case.

Can your theory do that?

At present, I am not modeling anything with a dielectric insert. I am only "attempting" to model a tapered waveguide "correctly", per Zeng and Fan. What I'm missing is, how much "power" is required, in the frame of the EM Drive, to make it go. What I'm getting is, a rocket equation with an "extra" term, dependent on the gradient of the potential energy and a non-linear equation that implies power consumption is reduced. However, after yesterdays misunderstanding, revelation and embarrassment. I am still trying to put all the pieces back together in a comprehendible way.

The good news is, the discussion about the paradox cleared up a few things that will help me to finish the other paper correctly, but my question about F*vgroup for EM waves vs F*vphase for matter waves or propellant, still has me confused as to; Why are they different?
Todd

Offline ElizabethGreene

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I have a question:

What is the most powerful microwave source that is available to private persons?  And what is the maximum intensity that, say, copper can withstand without melting, exploding or whatever?

Your difficulty isn't that the copper melts, instead you have arcing inside the waveguide and resonator.  The gas (or lack thereof) inside the waveguide or cavity determines when this happens.  Arcing happens more readily in vacuum than in air than in https://en.wikipedia.org/wiki/Sulfur_hexafluoride.  The latter, Sulfur Hexafluoride, is used in large Van de Graaf generators to prevent arcing.  The gas inside the resonator is a type of dielectric, so you'll have a change in the group velocity and other math to consider.

To your other question, what is the largest size microwave source can you buy:   Big.  They are not controlled devices.  If you accidentally melt a busload of people with one, that will likely change.

The largest microwave sources I found were Gyrotrons.  There is a company, "Gyrotron Technology Inc." that offers custom and semi-custom gyrotrons with remarkable microwave sources available.  I have not reached out to them for pricing or capability details.

Offline TheTraveller

Todd

Todd,

Any EMDrive theory must show the direction of the dielectric generated Force (Small to Big) at 180 deg opposite the non dielectric case (Big to Small) and the dielectric Force to be much weaker than the non dielectric case.

Can your theory do that?

At present, I am not modeling anything with a dielectric insert. I am only "attempting" to model a tapered waveguide "correctly", per Zeng and Fan. What I'm missing is, how much "power" is required, in the frame of the EM Drive, to make it go. What I'm getting is, a rocket equation with an "extra" term, dependent on the gradient of the potential energy and a non-linear equation that implies power consumption is reduced. However, after yesterdays misunderstanding, revelation and embarrassment. I am still trying to put all the pieces back together in a comprehendible way.

The good news is, the discussion about the paradox cleared up a few things that will help me to finish the other paper correctly, but my question about F*vgroup for EM waves vs F*vphase for matter waves or propellant, still has me confused as to; Why are they different?
Todd

In a waveguide Group Velocity is below c and Phase Velocity is above c. Phase Velocity X Group Velocity = c^2.

Information, energy and momentum, in a waveguide travels at Group Velocity. As Phase Velocity is above c it is imaginary inside a waveguide and thus nothing inside a waveguide travels at Phase Velocity. This is microwave waveguide engineering 101.

Outside a waveguide normally Group Velocity = Phase Velocity = c.

So forget about Phase Velocity when dealing with EM waves inside a waveguide.

Group Velocity = c * (Free wavelength / Guide Wavelength).

Guide Wavelength depends on Cutoff Wavelength, which depends on excitation mode, waveguide diameter at the waves position and external Rf frequency.

Read this:
http://www.microwaves101.com/encyclopedias/waveguide-mathematics#guide
« Last Edit: 07/15/2015 06:13 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline ElizabethGreene

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So forget about Phase Velocity when dealing with EM waves inside a waveguide.

I've yet to find any use for the Phase Velocity.  I had a brief thought that obscene >> c values might cause some issues due to charges or magnetic fields being unable to rearrange fast enough in the material, but I intuit that should cause localized heating, not thrust.

Offline Rodal

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Estimate of Power in Meep Computer Simulations with Dipole Antenna RF feed

I have translated the Meep units for time and electromagnetic fields, but the Power Input into the Meep computer runs still has not been tackled.

I propose the following estimate of Power Input (comments, modifications and improvements are welcome).

We know the following:

@aero has modeled the RF feed with a dipole antenna (the simplest and most widely used class of antenna), consisting of two identical conductive elements such as metal wires or rods, which are bilaterally symmetrical. The driving current from the transmitter is applied, between the two halves of the antenna. 



The driving current in the Meep runs has been taking as the default value: 1 Amp

Length of Dipole Antenna modeled: 0.058 m

We can calculate the free-space wavelength as:  λ = c / frequency

Taking the frequency to be 2.45 GHz (as per @rfmwguy's model) then λ = c / frequency = 0.122364 m

Therefore the ratio of the dipole antenna length L to the wavelength λ is:

L / λ = 0.058 m/0.122364 m
      = 0.4740

Which is close to 1/2. 



Hence we take the Half-Wave dipole antenna far-field radiation resistance value for a half-wave dipole antenna (https://en.wikipedia.org/wiki/Dipole_antenna#Half-wave_dipole )

R = 73.1 Ω

(Using the short-dipole approximation (https://en.wikipedia.org/wiki/Dipole_antenna#Short_dipole ) way outside its valid range would give, by comparison, R = 44.26 Ω or 61% of the half-wave far-field resistance)

Now we use the relationship:

InputPower *Efficiency = (Io)2 R/2

(where the value of 1/2 is due to the cyclic time-average of the harmonic oscillation of Io)

Therefore the InputPower is

InputPower = (Io)2 R/ (2* Efficiency)

Using a value of Efficiency = 0.85, the Half-Wave Resistance value, and the Meep default value for Io =1 Amp we get:

InputPower  = (Io)2 R/ (2* Efficiency)
                   = 1 * 73.1 / (2 *0.85)
                   = 43 Watts

So the previous Poynting Vector and Stress calculations are for an Input Power of 43 Watts (similar to the value used by NASA in some of their runs).

The Poynting vector and the Stress values are proportional to the Input Power, so for example, if the Input Power were 860 Watts, that means that the calculated values for Poynting vector and Stress are 860 Watts/ 43 Watts = 20 times greater than shown in the plots.    In other words, for 860 Watts InputPower, the values for Poynting Vector and Stress in the plots need to be multiplied by a factor of 20.
« Last Edit: 07/15/2015 08:15 PM by Rodal »

Offline flux_capacitor

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I have a question:

What is the most powerful microwave source that is available to private persons?  And what is the maximum intensity that, say, copper can withstand without melting, exploding or whatever?

Your difficulty isn't that the copper melts, instead you have arcing inside the waveguide and resonator.  The gas (or lack thereof) inside the waveguide or cavity determines when this happens.  Arcing happens more readily in vacuum than in air than in https://en.wikipedia.org/wiki/Sulfur_hexafluoride.  The latter, Sulfur Hexafluoride, is used in large Van de Graaf generators to prevent arcing.  The gas inside the resonator is a type of dielectric, so you'll have a change in the group velocity and other math to consider.

To your other question, what is the largest size microwave source can you buy:   Big.  They are not controlled devices.  If you accidentally melt a busload of people with one, that will likely change.

The largest microwave sources I found were Gyrotrons.  There is a company, "Gyrotron Technology Inc." that offers custom and semi-custom gyrotrons with remarkable microwave sources available.  I have not reached out to them for pricing or capability details.

Along gyrotrons, the most powerful manmade source of microwaves are klystrons. SLAC uses 150 megawatts (pulsed) S-band (3GHz) klystrons and 1.25 MW CW klystrons! But we don't wand to ignite the plasma of a tokamak or power a particle accelerator, and we're not quite yet feeding lift engines of a mothership.

Below, a 65 MW SLAC klystron:


Offline deltaMass

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First, locate your eggs  8)
This is a Yoke, right?
Oxen ye shall receive  :P


Offline Tron

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Sorry for interrupting, but there are a couple things that puzzle me. I don't think I'll post much or at all after this, since the thread is so active and I don't have the energy to keep up with it continuously.

First, I don't quite understand the discussion about how wave behave in a waveguide, when we're not dealing with waveguides; the frustrum is a not (just) that but a resonant chamber.  This means the radiation inside should form standing waves, with their nodes where the field is always zero, and whatnot, am I correct?

I've been looking at several sources, but they confirm that, if we have a standing wave the phase velocity is zero and group velocity is infinite. I can't tell who's right, but either the resonant chamber should not move at all, or resonant chambers should all explode the instant you put some energy in them, depending on who's right.

Second, the talk about conservation of energy got entangled in relativity, and the reason confuses me. Could we agree to discuss scenarios where v<<c so gamma is close to 1? This way we can use classical mechanics and  not get needlessly bogged down on einstenian paradoxes while imultaneously recognizing that al inertial reference frames should be equivalent. Not that you need relativity for that, since equivalence under Galilean transformations has been part of classical mechanics for a very long time.

Offline Star One

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FYI:

http://www.huffingtonpost.com/benjamin-t-solomon/a-propellantless-propulsi_b_7718408.html

Well New Horizons has shown if you really want to completely study somewhere like Pluto you're going to need a much quicker way to get there.

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