Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 3130585 times)

Offline Notsosureofit

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If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.

Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.


That's an interesting experiment in that it is independent of the cavity errors.  If we look at something like Eq. 14 in Marco's paper, we might expect to see nothing for a perfectly conducting cavity.  Copper isn't perfect, so there may be an effect due to dielectric (or magnetic) leakage.  In any event, an independent weight measurement would be much less noisy, I would think.  (so more sensitive, as required)

Offline TheTraveller

...As mentioned I have silver epoxy and will be using it as the 1st 2 layers, then using the Copper/Metal epoxy for an overcoat. My experience with silver epoxy is that it doesn't have a lot of strength and can't be replied on to generate a physically strong joint...
The silver epoxy has a film thickness dependent conduction behavior (due to the percolation behavior of the conductive particles and the viscosity of the epoxy).  The resistivity levels are reduced as the adhesive film thickness increases. Conversely, when the thickness is reduced significantly, a significant increase in resistivity is observed coupled with a significant increase in the slope of the resistivity-thickness curve.  On the other hand, as the thickness increases, the strength decreases.  So, getting it right is an art  :)

I have experience working with silver epoxy. As stated will be using several thin layers. allowed to totally cure between layers and then using the copper/metal epoxy overcoat. Will also be using a thin / fine copper mesh, applied as the 1st layer, next to the copper outer skin, to back it up.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline phaseshift

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I do believe what we see in the 2nd image to the left of the Red RF feed may not be an impedance matching system but instead an arm that extends inside the Flight Thruster such that Shawyer can fine tune the antenna position. It appears to have a small arm / crank on the left end and the ability to slide in and out.

Eagle Eyes!

Yes, I agree, that's exactly what it appears to be. Would the crank move the launcher/antenna up and down - or side to side?
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

Offline TheTraveller

I do believe what we see in the 2nd image to the left of the Red RF feed may not be an impedance matching system but instead an arm that extends inside the Flight Thruster such that Shawyer can fine tune the antenna position. It appears to have a small arm / crank on the left end and the ability to slide in and out.

Eagle Eyes!

Yes, I agree, that's exactly what it appears to be. Would the crank move the launcher/antenna up and down - or side to side?

If there is a TM mode excitation antenna inside, someone said he used a T antenna, it would need to be aligned exactly to the cavity central axis, ie in exact alignment with a line between the end plate centres.

Depending on how he physically built this, would allow the desired movement he needed to get physical alignment of the internal excitation antenna to the frustum effective central axis.

As I will have only 100W to work with, will need every bit of tuning, tweaking and small incremental gains to get enough thrust to have a VERY healthy signal to noise ratio.

It may also need to be located at the frustum diameter where the guide wavelength is at the effective cavity guide wavelength, so to get 1/4 wave resonance from the centre of the antenna to each end plate or 1/2 wave resonance overall.
« Last Edit: 05/25/2015 04:00 pm by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline aero

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Regarding antenna placement. In Meep, exciting the electric modes, I have good success achieving resonance when I place the antenna one-half wavelength from the end of the cavity (cylindrical cavity). What does the theory say about antenna placement to achieve resonance?

Note that this works well even when I change the drive frequency as long as the frequency is near the resonant frequency of a mode of the cavity. Meep excites with a noisy (Gaussian) source and zeros in on the resonance frequency without to much fiddling this way.
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Offline SeeShells

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If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.

Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.


That's an interesting experiment in that it is independent of the cavity errors.  If we look at something like Eq. 14 in Marco's paper, we might expect to see nothing for a perfectly conducting cavity.  Copper isn't perfect, so there may be an effect due to dielectric (or magnetic) leakage.  In any event, an independent weight measurement would be much less noisy, I would think.  (so more sensitive, as required)

How could you visualize the Em waveforms of a thrust mode outside the cavity if somehow and still keeping the cavity shape and TM or TE resonate mode? (yes I know the copper is reflecting or absorbing the EM waves) Does this make sense in how I said it? Like a virtual wave? I'd try it without asking, but just don't have the software.
 

Offline TheTraveller

Regarding antenna placement. In Meep, exciting the electric modes, I have good success achieving resonance when I place the antenna one-half wavelength from the end of the cavity (cylindrical cavity). What does the theory say about antenna placement to achieve resonance?

Note that this works well even when I change the drive frequency as long as the frequency is near the resonant frequency of a mode of the cavity. Meep excites with a noisy (Gaussian) source and zeros in on the resonance frequency without to much fiddling this way.

I feel as the cavity needs to have resonance with the effective cavity guide wavelength, the use of a T antenna may be good, with the centre of the antenna placed at the frustum diameter which generates the same guide wavelength as the numerically integrated overall guide wavelength.

Then as the changing frustum diameter shortens or lengthens the guide wavelengths as they near the end plates, the antenna will sense cavity resonance, even thought the guide wavelength at each end will not be the guide wavelength present at the central point of the T antenna.

Trust this makes sense.
« Last Edit: 05/25/2015 04:08 pm by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline WarpTech

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If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.

Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.


That's an interesting experiment in that it is independent of the cavity errors.  If we look at something like Eq. 14 in Marco's paper, we might expect to see nothing for a perfectly conducting cavity.  Copper isn't perfect, so there may be an effect due to dielectric (or magnetic) leakage.  In any event, an independent weight measurement would be much less noisy, I would think.  (so more sensitive, as required)

Don't waste your time please. This is 10^22+ orders of magnitude too small to measure a gravitational effect on normal matter. Again, the gravitational field acts on matter across a very wide bandwidth of frequencies. The majority of mass is inside the nucleus, so the majority of the interaction with gravity is happening in that bandwidth. The effect we have here is only mimicking those effects over a very narrow bandwidth "inside" the waveguide. Outside, all you'll measure is heat.

Todd

Offline aero

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Has anyone ever tried to detect radiation at any frequency outside of the cavity? Theoretically I think there should be none but has that been verified?
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Offline TheTraveller

Has anyone ever tried to detect radiation at any frequency outside of the cavity? Theoretically I think there should be none but has that been verified?

You mean ionising radiation?

There is plenty of EMC as Shawyer commented on during the Demonstrator rotary test:
http://emdrive.com/dynamictests.html

Quote
The field strengths within the thruster equate to a power level of 17MW. Signal leakage causes EMC effects within the fixed video camera. This leads to the apparent vertical movements.
« Last Edit: 05/25/2015 04:32 pm by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline Notsosureofit

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If space time is being bent, and the bend is symmetrical, the non-thrusting (smaller) end plate should have an opposite attracting (pulling) force rather than a repulsive (pushing) force.

Could these forces be detected by Iulian in his test setup. So, rather than hang the drive on the scales, place the drive on the floor, then hang a weight on the scale that lies as close to the end plate as possible. Then repeat for the other plate.


That's an interesting experiment in that it is independent of the cavity errors.  If we look at something like Eq. 14 in Marco's paper, we might expect to see nothing for a perfectly conducting cavity.  Copper isn't perfect, so there may be an effect due to dielectric (or magnetic) leakage.  In any event, an independent weight measurement would be much less noisy, I would think.  (so more sensitive, as required)

How could you visualize the Em waveforms of a thrust mode outside the cavity if somehow and still keeping the cavity shape and TM or TE resonate mode? (yes I know the copper is reflecting or absorbing the EM waves) Does this make sense in how I said it? Like a virtual wave? I'd try it without asking, but just don't have the software.
 

You can look at the radiation patterns for a dielectric cavity of the same dimensions.  The losses in a copper cavity are principally from the resistance in the walls, but there are also some radiative losses (albeit very small, but not calculated at this point) from any cavity w/ a finite Q.  In the limit the Q gets very low and you have effectively a photon rocket.
« Last Edit: 05/25/2015 04:40 pm by Notsosureofit »

Offline Rodal

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...All good points. I believe she is trying to facilitate using Maxwell's equations by imagining there are particles inside the volume. Maxwell's equations are difficult, this is a crutch. Where she is making her mistake is that there actually are charged particles inside the volume, (besides air) they are not imaginary, they are confined to within the skin effect depth of the metal. The skin effect is inside the volume of integration for the Divergences, and it contains both positive and negative charges. Typically, we ignore the force acting on the lattice ions, since their mass is so much greater than the electrons, but they are there and they do scatter, vibrate and transfer momentum from the field to the frustum.

Unfortunately, she does not elaborate on the actual expressions of E and H, that would depend on the geometry, attenuation, phase, etc... she leaves that to the results table of her FEA. But the force equation she ends up with is still the correct equation. Its correctness, as always, depends on the accuracy of what you plug-in for E and H at the boundary, and the duty cycle of the power consumption. Therefore, if you know what to plug in, it's only a "minor" issue in her example and explanation, not in the actual FEA which is supposedly a realistic simulation of a brass cavity.

Let's agree that real charged particles (with the EM Drive in a vacuum) are confined within the skin depth of the material. 

At 2.45 GHz frequency, the skin depth is readily calculated to be only 1.3*10-6 m. 

Compare this dimension with the height of the cavity which she gives as 2*10-1 m.

Therefore the height of the cavity is 160,000 times larger than the skin depth.

This ratio (160,000 times) shows why she considers the case of having a fluid of charged particles inside the cavity.

If it takes a finite element mesh of  69,549 nodes to model the cavity, to also model the skin would take 160,000 times finer mesh (smaller finite elements) to model similar electromagnetic field variation.  The finite element matrix goes like the square, so to invert the finite element matrix becomes an overwhelming job, even for a supercomputer (that she does not indicate as having used).

Moreover, she would need to specify the constitutive model she would use to model the skin effect (which she does not specify).

No, the indications are that to simultaneously model the skin effect with a Finite Element model is not practically feasible and that's why she doesn't describe it.

On the contrary, she states that she effectively did not model the skin effect with a finite element discretization, see page 9, section 3.2 "Thrust calculation" where she states:

Quote
with air as filling medium and electric wall boundary condition,

So what she did was, instead of modeling the skin effect with a finite element discretization, she simply modeled it as a boundary condition.

Since we know that one cannot get a net force (averaged over an integer number of time periods) without charged particles in the cavity medium, or without a constitutive model describing absorption in the skin, either we have to take her at her word that she modeled the medium in the cavity as having charged particles, or that she used a separate equation to model the skin effect (not a finite element discretization of the skin effect).

Therefore, she must have some undisclosed free parameters, either modeling virtual charged particles in the medium in the cavity (air) or in her formula for the skin effect.

Then her model is not that different from Dr. White's, as she has "not nailed the problem" until one is satisfied that her free parameters can be substantiated by independent physical data. 

Quote from: John Von Neumann
With four parameters I can fit an elephant, and with five I can make him wiggle his trunk.
« Last Edit: 05/25/2015 05:03 pm by Rodal »

Offline zen-in

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Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?


I would go for an old fashioned soldering.  Why introduce another unknown variables caused by the glue?

BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.

Thanks for the comment.

I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.

As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.

It's very easy to cut thin copper with metal shears.   Inside curves are a little tricky but a straight edge linoleum knife works well.   Epoxy may work for joining the pieces if the joints are tab joints.   Otherwise handling and heating will make it come apart.   Conductive epoxy is an insulator at microwave frequencies, due to the skin effect.  Silver fill Copper or Brass is one option.   This product has a thin layer of Sterling Silver bonded to Copper or Brass sheet.  The Silver layer is thicker than plating.   I don't know who makes it now and you would really want fine Silver (999) anyway because Sterling Silver has a lower conductivity than Copper.   Silver plating, to achieve better RF skin layer conductivity than Copper is not easy to do.   If you really wanted to optimize this em-drive cavity you could use 24 K Gold plated fine Silver sheet.   Gold is actually a better conductor at microwave frequencies when skin effects, etc are considered; although fine Silver is the best room temperature conductor at DC and MF.
« Last Edit: 05/25/2015 05:13 pm by zen-in »

Offline TheTraveller


Plan is to laser cut all the pieces from 0.5mm thick copper sheet. Have found a company that can do a proper roll of the frustum so the side joint is a butt joint. Same company can form the spherical end plates.

1) UL certified Copper epoxy will be used to join the 2 end flanges to the frustum and then cover the butt joint.
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Does anyone have an opinion on this joining method?


I would go for an old fashioned soldering.  Why introduce another unknown variables caused by the glue?

BTW. I wanted to say Hi to the whole community. I've been around for a while reading, now I'll try to throw my 5 cents from the point of view of a mechatronic engineer... well if I have something useful to say.

Thanks for the comment.

I have concerns about the frustum warping when using soldering. Have built stuff before using thin copper plate, know it moves and the final soldered positions may not be the unsoldered position.

As I see it, making sure the 2 end plates are highly parallel and joined to the frustum at the same angle ensures the highest Q I can get. Using a cold assembly method should ensure the money I'm paying for laser cutting, to ensure everything is at the right angles to each other, will pay dividends.

It's very easy to cut thin copper with metal shears.   Inside curves are a little tricky but a straight edge linoleum knife works well.   Epoxy may work for joining the pieces if the joints are tab joints.   Otherwise handling and heating will make it come apart.   Conductive epoxy is an insulator at RF frequencies, due to the skin effect.  Silver fill Copper or Brass is one option.   This product has a thin layer of Sterling Silver bonded to Copper or Brass sheet.  The Silver layer is thicker than plating.   I don't know who makes it now and you would really want fine Silver (999) anyway because Sterling Silver has a lower conductivity than Copper.   Silver plating, to achieve better RF skin layer conductivity than Copper is not easy to do.   If you really wanted to optimize this em-drive cavity you could use 24 K Gold plated Fine Silver sheet.   Gold is actually a better conductor at RF frequencies when skin effects, etc are considered; although Fine Silver is the best room temperature conductor at DC and low RF frequencies.

Thanks for the information.

My use of silver epoxy will be restricted to external frustum surfaces. If any gets inside, it will be removed.  The Copper Epoxy overcoat is UL rated to not come apart in plumbing and fire sprinkler applications:

http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Quote
Safe and easy to use Copper-BondŽ is UL listed for joining copper tube used in fire sprinkler systems and NSF approved for hot and cold water systems.

As my max power input is 100W, I feel the joint temperatures should be well with-in the UL rating.

There will also be alum supporters as per the 1st Experimental device, so will get additional surface area to radiate heat. All this will be inside a sealed Faraday Cage as Shawyer used.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

The Copper Bond Epoxy may be of use to other replicators. Data here:
http://www.supergluecorp.com/super-glue/epoxies/copper-bond

Data sheet attached.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline WarpTech

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...All good points. I believe she is trying to facilitate using Maxwell's equations by imagining there are particles inside the volume. Maxwell's equations are difficult, this is a crutch. Where she is making her mistake is that there actually are charged particles inside the volume, (besides air) they are not imaginary, they are confined to within the skin effect depth of the metal. ...

Let's agree that real charged particles (with the EM Drive in a vacuum) are confined within the skin depth of the material. 

(...)
No, the indications are that to simultaneously model the skin effect with a Finite Element model is not practically feasible and that's why she doesn't describe it.

On the contrary, she states that she effectively did not model the skin effect with a finite element discretization, see page 9, section 3.2 "Thrust calculation" where she states:

Quote
with air as filling medium and electric wall boundary condition,

So what she did was, instead of modeling the skin effect with a finite element discretization, she simply modeled it as a boundary condition.

Since we know that one cannot get a net force (averaged over an integer number of time periods) without charged particles in the cavity medium, or without a constitutive model describing absorption in the skin, either we have to take her at her word that she modeled the medium in the cavity as having charged particles, or that she used a separate equation to model the skin effect (not a finite element discretization of the skin effect).

Therefore, she must have some undisclosed free parameters, either modeling virtual charged particles in the medium in the cavity (air) or in her formula for the skin effect.
(...)

Correct, she has undisclosed free parameters! That is what I meant when I said she did not elaborate on her expressions for E and H. Technically, she does not need to model the skin effect in her FEA. She simply needs to express her E and H amplitudes with an exponential attenuation factor.

If I go by Zeng and Fan, then;

E(r, theta, phi) = A(theta, phi)*exp[jk*r]

jk*r => -a*r - jb*r,

Where, "a" is the attenuation factor. Her amplitude would then include a factor of exp[-2a] in the pressure term. The attenuation factor is a free parameter that depends on the geometry and material, which she does not disclose. However, her "equation", is correct IFF you plug in the correct expressions for E and H at the boundary.

I wrote a paper back in 2007 about propellant-less propulsion, for an "Acceleration to Voltage Transducer". In it, I show how accelerating Mass with the Lorentz force is equivalent to an Inductive load, which must be offset by a capacitive load (charge) to do physical work, by correcting the power factor to unity. I showed that in a closed system where the divergence is zero and where momentum is stored, you can still transfer momentum from the field to the particles in a cleaver way, to produce thrust. There are many similarities to what we are discussing now. My work has a flaw however. I found it is impossible to store any significant amount of charge and have it not polarize everything around it, negating most of the effect. I end up with F1 - F2 ~ 0, except for losses and leakage flux, and the amount of charge required becomes enormous. (links) Though I have never built one and tested it.

https://www.dropbox.com/s/pddq48tlxtj5f7s/AccelerationTransducer.pdf?dl=0
https://www.dropbox.com/s/lmie4j7oo7lkqyo/Propellant-less%20Propulsionx3.pdf?dl=0




Offline Rodal

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...Correct, she has undisclosed free parameters! That is what I meant when I said she did not elaborate on her expressions for E and H. Technically, she does not need to model the skin effect in her FEA. She simply needs to express her E and H amplitudes with an exponential attenuation factor...
Well it is always a pleasure to discuss things with you.  Besides your universally recognized gift for explaining things in simpler terms that people can relate to, discussions with you lead to deeper levels of common understanding.

And now with that preamble, until Prof. Yang discloses her constitutive model for the skin effect, and we can independently ascertain whether her free parameter(s) are based on known material properties, is her model really to be preferred to models like Dr. McCulloch's or Notsosureofit's that also model the thrust, but with a minimum of free parameters ?  (Neither McCulloch's or Notsosureofit's models need such extra free parameters: they don't need the attenuation factor).
« Last Edit: 05/25/2015 05:47 pm by Rodal »

Offline demofsky

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...I also think I found a (minor?) error in the 2013 paper. In my estimation, equations 4 and 6 are correct. Where I disagree is that her premise is that there are charged particles in the volume, and then on equations 7 and 8, she removes the particle momentum density and the energy density of the field, for no apparent reason and then IMO, she abruptly ends the section....
Can you please elaborate why youthink this is, maybe, just a (minor) error by Prof. Yang and her co-authors?

(And by the way, I am looking at the 2010 paper, not the 2013 paper, in my comments below)

They write (2010 paper, translation page 4,  original page 28)

http://www.emdrive.com/NWPU2010translation.pdf
Quote
If the microwave electromagnetic field consists of charge particles, due to the
electromagnetic force, the charge particles can travel within the electromagnetic
field, so the charge particles can acquire energy and momentum from the
electromagnetic field. This indicates that electromagnetic field have energy and
momentum.

The microwave electromagnetic field inside the cavity is composed of photons (at microwave frequencies), which as we all know, have no charge whatsoever.  So the microwave electromagnetic field does not consist of charge particles (unless one considers the virtual particles of the QV or one considers ionized air).  This is the difference between Greg Egan's equations http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html, who finds no net thrust force, since he doesn't consider this term at all.

If there are any charges and currents, they are only present in the copper metal (translation says "brass"), and not inside the empty microwave cavity.  This seems to me a major issue, and not a minor point.



The original 2010 paper in Chinese (http://www.emdrive.com/NWPU2010paper.pdf) says (my translation)

Quote
The microwave electromagnetic field of charged particles , if present , due to the electromagnetic force 

The "if present" seems to have been translated to "if it consists of".  Either way, "If present" or "if it consists of" is a big if.   We have to understand whether this condition is met, and if so, what are these charged particles.

Are the authors considering charged particles to be present in the empty cavity?

In essence are the authors effectively considering virtual charged particles like the QV of Dr. White ?

Or are the authors considering having ionized air inside the cavity ?
  (one example:  http://www.jpier.org/PIERM/pierm26/20.12101201.pdf  )

Hm.  As has been noted many times both Sawyer and Yangs experiments are ran at atmospheric pressure and are furthermore (as far as anyone can tell) well sealed.

So, in an excess of caution desiring to make sure we explicitly cover all the bases here, I have to ask the following question:

Are these ion wind devices?  (Masquerading as exotic physics machines...)

Intuitively, if there is an ionic wind in these devices then I certainly can believe there will be measurable effects from the wind hammering (relatively speaking) the frustum wall.

One defence for this hypotheses is the difference in measured effects between the Yang and Sawyer devices and the Eagleworks vacuum tests.

Offline ThinkerX

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Quote
One defense for this hypotheses is the difference in measured effects between the Yang and Sawyer devices and the Eagleworks vacuum tests.

To me, this is a really crucial bit of info.  If these devices loose this much performance in a vacuum, then are they really all that superior to a photon rocket?  Or could they be some bizarre version of Bae's bouncing laser scheme, which increases photonic thrust on the order of 5000 times? (except with one spacecraft instead of two?)





Offline TheTraveller

The Frank Davies mode analysis (attached) did a really good covering most of the frustum TEmnp and TMmnp modes.

TE013 is missing and may be of interest as the E field intensity at the small end may be very large.

Can anybody supply the E and H field analysis as NASA did but for the missing TE013 mode? It will be worth your time as I have significant new information regarding the Flight Thruster. It operated in TE013 mode.
« Last Edit: 05/25/2015 06:23 pm by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

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