Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1797791 times)

Online Rodal

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One note I would like to add on this subject:   If Shawyer's em-drive does not produce any thrust in the absence of vibration then it will not work in outer space.    Space is a vacuum and sound waves don't travel in space.   There would be no vibrations to "stimulate" the em-drive.   


Attaching a vibrator to the drive is not hard.

Although when the press finds out the spacecraft needs a vibrator to come we will get lots of dildo jokes.
That presumes that all you have to do to get space propulsion is to have internally generated forces (in this case vibration), internal to the spacecraft, that further violates the principle of conservation of momentum.  I think that zen-in was looking at externally-forced vibration, in order to try to not break conservation of momentum.
« Last Edit: 06/29/2015 11:02 PM by Rodal »

Offline X_RaY

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Views of NSF-1701 are up:

https://drive.google.com/folderview?id=0B1XizxEfB23tfklENXg2TWhrbUhneGxZQzJ0VVhkRFRwUUhCN2xKX24yOGM2bFQzdVV5NlE&usp=sharing

This file shows the 18 views of the E and H components from x, y and z directions.
This is from a Meep model of rfmwguy's 10.2 inch cavity, in copper, driven by a 2.45000 GHz continuous Ez source. The resonant frequency of this cavity is somewhere close to 2.45 GHz but no resonance solutions indicate exactly 2.45 GHz. The continuous source used in this model is ideal and exact. There are no "shoulders" on the input power source, all input energy is at exactly the drive frequency, 2.45 GHz. The antenna model, a dipole, is oriented perpendicular to the central axis of rotation, one-half wavelength from the small end, and is 0.058 meters long.

An important point is to note that these views use a fixed Max/Min range of power/color intensity. I'll leave it to the experts to analyse the characteristics shown.

Since we continue without having any numerical result, we have to resort to some heuristic as following to interpret these pictures:

1) Picture showing fractal are a numerical artifact due to values close to zero, hence pictures with fractals should be interpreted as low values close to zero

2) Concentrate on images showing smooth and persistent contours (persistent in several frames)

3) Use the field in the longitudinal x direction to determine mode shape

4) Conduct independent eigenvalue analysis to determine frequencies of several modes at 10.2 inches.


///////////////////

Using the above-mentioned heuristics, we determine:

1) The strong field in the longitudinal x direction is Ex, in this case Ex -y (the electric field in the longitudinal direction, seen in the x-z plane with normal y).  This field shows 4 wave patterns in the longitudinal direction.  Hence p=4.  Notice that Ex - z is zero.

2) Hx  -y and Hx -z are fractal hence interpreted as close to zero

3) Actually all magnetic fields in this case appear to be fractal, hence interpreted as very low, close to zero

4) Ez is strong both in the planes with y and z normals.  Both show p=4

5) The strong Ex points towards a TM mode.  The lack of any strong H field in the transverse direcitons points towards a TE mode

I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

Online aero

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Views of NSF-1701 are up:

https://drive.google.com/folderview?id=0B1XizxEfB23tfklENXg2TWhrbUhneGxZQzJ0VVhkRFRwUUhCN2xKX24yOGM2bFQzdVV5NlE&usp=sharing

This file shows the 18 views of the E and H components from x, y and z directions.
This is from a Meep model of rfmwguy's 10.2 inch cavity, in copper, driven by a 2.45000 GHz continuous Ez source. The resonant frequency of this cavity is somewhere close to 2.45 GHz but no resonance solutions indicate exactly 2.45 GHz. The continuous source used in this model is ideal and exact. There are no "shoulders" on the input power source, all input energy is at exactly the drive frequency, 2.45 GHz. The antenna model, a dipole, is oriented perpendicular to the central axis of rotation, one-half wavelength from the small end, and is 0.058 meters long.

An important point is to note that these views use a fixed Max/Min range of power/color intensity. I'll leave it to the experts to analyse the characteristics shown.

Since we continue without having any numerical result, we have to resort to some heuristic as following to interpret these pictures:

1) Picture showing fractal are a numerical artifact due to values close to zero, hence pictures with fractals should be interpreted as low values close to zero

2) Concentrate on images showing smooth and persistent contours (persistent in several frames)

3) Use the field in the longitudinal x direction to determine mode shape

4) Conduct independent eigenvalue analysis to determine frequencies of several modes at 10.2 inches.


///////////////////

Using the above-mentioned heuristics, we determine:

1) The strong field in the longitudinal x direction is Ex, in this case Ex -y (the electric field in the longitudinal direction, seen in the x-z plane with normal y).  This field shows 4 wave patterns in the longitudinal direction.  Hence p=4.  Notice that Ex - z is zero.

2) Hx  -y and Hx -z are fractal hence interpreted as close to zero

3) Actually all magnetic fields in this case appear to be fractal, hence interpreted as very low, close to zero

4) Ez is strong both in the planes with y and z normals.  Both show p=4

5) The strong Ex points towards a TM mode.  The lack of any strong H field in the transverse direcitons points towards a TE mode

6) How can that be?  An examination of the eigenvalue problem using Mathematica and the exact solution shows:


TE114 = 2.434 GHz
TM114 = 2.479 GHz

CONCLUSION: TE114 is excited with strong participation of TM114  We see the strength of Meep: while all the other analysis (including COMSOL FEA by NASA) have been eigenvalue analyses, the Meep solution is a transient solution in time, hence it automatically incorporates a spectrum analysis: it looks at participation of nearby modes.  (This can also be done with COMSOL FEA and other FEA programs of course, but nobody else has reported transient solutions up to now).

Having two modes with equal m, n, p, nearby results in participation of both modes (having 114 mode shape).

I was thinking that because the intensity scale is fixed over each complete view data set, and there is little or no increase in intensity from beginning to end of the run, then the cavity is not resonating very well, certainly not strongly. The fractal nature of the H fields support that thought, by indicating low energy. JMO. Perhaps I will make the same run using a Gaussian source. Noise Bandwidth say, What? What is the noise bandwidth of a magnatron?
Retired, working interesting problems

Online Rodal

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Views of NSF-1701 are up:

https://drive.google.com/folderview?id=0B1XizxEfB23tfklENXg2TWhrbUhneGxZQzJ0VVhkRFRwUUhCN2xKX24yOGM2bFQzdVV5NlE&usp=sharing

This file shows the 18 views of the E and H components from x, y and z directions.
This is from a Meep model of rfmwguy's 10.2 inch cavity, in copper, driven by a 2.45000 GHz continuous Ez source. The resonant frequency of this cavity is somewhere close to 2.45 GHz but no resonance solutions indicate exactly 2.45 GHz. The continuous source used in this model is ideal and exact. There are no "shoulders" on the input power source, all input energy is at exactly the drive frequency, 2.45 GHz. The antenna model, a dipole, is oriented perpendicular to the central axis of rotation, one-half wavelength from the small end, and is 0.058 meters long.

An important point is to note that these views use a fixed Max/Min range of power/color intensity. I'll leave it to the experts to analyse the characteristics shown.

Since we continue without having any numerical result, we have to resort to some heuristic as following to interpret these pictures:

1) Picture showing fractal are a numerical artifact due to values close to zero, hence pictures with fractals should be interpreted as low values close to zero

2) Concentrate on images showing smooth and persistent contours (persistent in several frames)

3) Use the field in the longitudinal x direction to determine mode shape

4) Conduct independent eigenvalue analysis to determine frequencies of several modes at 10.2 inches.


///////////////////

Using the above-mentioned heuristics, we determine:

1) The strong field in the longitudinal x direction is Ex, in this case Ex -y (the electric field in the longitudinal direction, seen in the x-z plane with normal y).  This field shows 4 wave patterns in the longitudinal direction.  Hence p=4.  Notice that Ex - z is zero.

2) Hx  -y and Hx -z are fractal hence interpreted as close to zero

3) Actually all magnetic fields in this case appear to be fractal, hence interpreted as very low, close to zero

4) Ez is strong both in the planes with y and z normals.  Both show p=4

5) The strong Ex points towards a TM mode.  The lack of any strong H field in the transverse direcitons points towards a TE mode

I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

Excellent point !

I agree.  It is the result of a lot of modes nearby and the dipole antenna being used is not favoring one mode over another:

TE114 = 2.43 GHz
TE013 = 2.45 GHz
TM114 = 2.47 GHz

p=3 comes from TE013

Offline X_RaY

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Views of NSF-1701 are up:

https://drive.google.com/folderview?id=0B1XizxEfB23tfklENXg2TWhrbUhneGxZQzJ0VVhkRFRwUUhCN2xKX24yOGM2bFQzdVV5NlE&usp=sharing

This file shows the 18 views of the E and H components from x, y and z directions.
This is from a Meep model of rfmwguy's 10.2 inch cavity, in copper, driven by a 2.45000 GHz continuous Ez source. The resonant frequency of this cavity is somewhere close to 2.45 GHz but no resonance solutions indicate exactly 2.45 GHz. The continuous source used in this model is ideal and exact. There are no "shoulders" on the input power source, all input energy is at exactly the drive frequency, 2.45 GHz. The antenna model, a dipole, is oriented perpendicular to the central axis of rotation, one-half wavelength from the small end, and is 0.058 meters long.

An important point is to note that these views use a fixed Max/Min range of power/color intensity. I'll leave it to the experts to analyse the characteristics shown.

Since we continue without having any numerical result, we have to resort to some heuristic as following to interpret these pictures:

1) Picture showing fractal are a numerical artifact due to values close to zero, hence pictures with fractals should be interpreted as low values close to zero

2) Concentrate on images showing smooth and persistent contours (persistent in several frames)

3) Use the field in the longitudinal x direction to determine mode shape

4) Conduct independent eigenvalue analysis to determine frequencies of several modes at 10.2 inches.


///////////////////

Using the above-mentioned heuristics, we determine:

1) The strong field in the longitudinal x direction is Ex, in this case Ex -y (the electric field in the longitudinal direction, seen in the x-z plane with normal y).  This field shows 4 wave patterns in the longitudinal direction.  Hence p=4.  Notice that Ex - z is zero.

2) Hx  -y and Hx -z are fractal hence interpreted as close to zero

3) Actually all magnetic fields in this case appear to be fractal, hence interpreted as very low, close to zero

4) Ez is strong both in the planes with y and z normals.  Both show p=4
Question: Is it possible that such "superposition" of several modes caused the propagated trust ??? if one mode is located in the bigger region and the other all over the cone? There are more field-nodes at the bigger end in the x-direction...
5) The strong Ex points towards a TM mode.  The lack of any strong H field in the transverse direcitons points towards a TE mode

I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

Excellent point !

I agree.  It is the result of a lot of modes nearby and the dipole antenna being used is not favoring one mode over another:

TE114 = 2.43 GHz
TE013 = 2.45 GHz
TM114 = 2.47 GHz

p=3 comes from TE013

Question: Is it possible that such "superposition" of several modes caused the propagated thrust ??? if one mode is located in the bigger region and the other all over the cone? There are more field-nodes at the bigger end in the x-direction... that looks really different to the small end. The energie is stored in the different modes over some full cycles, at the transition from one mode to a otner there is a flux of energie from one mode to the other. That could be lead to a difference in the resulting poynting vector at this moment..
« Last Edit: 06/29/2015 09:30 PM by X_RaY »

Online Rodal

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Question: Is it possible that such "superposition" of several modes caused the propagated trust ??? if one mode is more located in the bigger region and the other all over the cone? There are more field-nodes at the bigger end in the x-direction... that looks realy different to the small end.

Yes, as happens with parametric vibrations, we could have coupling of modes favoring some nonlinear response.

For example: think of the coupling between torsional vibration and bending vibration of a wing leading to aeroelastic flutter and aerolastic divergence.

Imagine Shawyer trying to make sense of aeroelastic flutter back in WWI :)))  .  How would he describe it?

To understand aeroelastic flutter one has to solve coupled systems of differential equations: nobody with the EM Drive is doing this.  Instead we get talk about "the EM Drive likes vibration" "the EM Drive likes background forces"  "The EM Drive has thrust pointing in the opposite direction than acceleration"


This valuable Meep run adds to pointing out another source of lack of robustness  in the EM Drive research:

1) only one organization has actually verified the mode shape: (NASA that verified TM212).  Neither Shawyer or Yang ever provided any experimental verification of mode shapes being excited

2) the EM Drive researchers up to now have not analyzed theoretically or numerically a spectrum superposition.  They have performed eigenvalue analysis assuming that only one mode was being excited.  Shawyer who has been working on this the longest, according to TT uses a kludgy spreadsheet that assumes cylindrical cut-off of modes, pure mode shape excitation and cylindrical formulas. 

3) the fact that multiple mode participation is practically possible makes the analysis of the EM Drive data more difficult to interpret. 

4) add this to the already known issues of thermal expansion shifting the natural frequencies

5) add to this the effect of the RF feed: Yang using a waveguide, many using a magnetron, others not, and so on and on.

6) add to this the never settled, always fluctuating nature of the response due to the RF feed always being on, emitting more and more photons: there is never a state of just standing waves, as assumed by Egan.  We have travelling waves, standing waves and evanescent waves.

7) no wonder that robustness in measured results is so elusive and that the statistical distribution of results is so huge...

... hopefully continued analysis can shed further light into this. 

We need all three types of analysis:

theoretical,

numerical and

experimental

all hand-in-hand to understand what is going on.
« Last Edit: 06/29/2015 08:56 PM by Rodal »

Offline deuteragenie

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Question: Is it possible that such "superposition" of several modes caused the propagated trust ??? if one mode is more located in the bigger region and the other all over the cone? There are more field-nodes at the bigger end in the x-direction... that looks realy different to the small end.

Yes, as happens with parametric vibrations, we could have coupling of modes favoring some nonlinear response.

For example: think of the coupling between torsional vibration and bending vibration leading to aeroelastic flutter and aerolastic divergence.

Imagine Shawyer trying to make sense of aeroelastic flutter back in WWI :)))  .  How would he describe it?

To understand aeroelastic flutter one has to solve coupled systems of differential equations: nobody with the EM Drive is doing this.  Instead we get talk about "the EM Drive likes vibration" "the EM Drive likes background forces"  "The EM Drive has thrust pointing in the opposite direction than acceleration"


This valuable Meep run adds to pointing out another source of lack of robustness  in the EM Drive research:

1) only one organization has actually verified the mode shape: (NASA that verified TM212).  Neither Shawyer or Yang ever provided any experimental verification of mode shapes being excited

2) the EM Drive researchers up to now have not analyzed theoretically or numerically a spectrum superposition.  They have performed eigenvalue analysis assuming that only one mode was being excited.  Shawyer who has been working on this the longest, according to TT uses a kludgy spreadsheet that assumes cylindrical cut-off of modes, pure mode shape excitation and cylindrical formulas. 

3) the fact that multiple mode participation is practically possible makes the analysis of the EM Drive data more difficult to interpret. 

4) add this to the already known issues of thermal expansion shifting the natural frequencies

5) add to this the effect of the RF feed: Yang using a waveguide, many using a magnetron, others not, and so on and on.

6) no wonder that robustness in measured results is so elusive and that the statistical distribution of results is so huge...

... hopefully continued analysis can shed further light into this. 

I usually get as a response : just wait for more experiments... Well yes, if the experiments are well-controlled.  Otherwise the confusion persists.  So we need all three types of analysis:

theoretical,

numerical and

experimental

all hand-in-hand to understand what is going on.

Ack.

For a start, it would be good to simulate the effect of changing the dimensions a bit.  Does it dramatically affect the results ?
Same for frequency: does a small change in freq affects the results in significant way?
Same for antenna length.
Etc.
This could provide valuable information for experimenters. 

« Last Edit: 06/30/2015 08:19 AM by deuteragenie »

Offline RERT

Folks - I really applaud the work going on here. However, I see no obvious progress on the problem of thrust being greater than a photon rocket, namely P/E = 1/c.

At the risk of stating the blindingly obvious, for a moving particle P/E = (mv)/(0.5mv^2) = 2/v

and so for slow v, P/E is much larger than a photon rocket.

So what? Well, if the EM field transfers energy to kinetic energy of electrons within the copper, which then collide with the frustrum (copper atoms) transferring momentum to it, then the ratio of momentum to energy could be high.

I'm not sure if this type of interaction would be captured in Lorentz forces generated by the EM field on the Frustrum and its eddy currents.

Does not explain how momentum leaves the frustrum...

Online Rodal

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Ack.

For a start, it would be good to simulate the effect of changing the dimensions a bit.  Does it dramatically affect the results ?
Same for frequency: does a small change in freq affects the results in sigificant way?
Same for antenna length.
Etc.
This could provide valuable information for experimenters.
Agreed.  Ack. There is a lot to simulate.

We are going to have to put some priorities though...(There is also the issues of antenna type, antenna location, waveguide coupling, and on and on) :)

Online Rodal

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Folks - I really applaud the work going on here. However, I see no obvious progress on the problem of thrust being greater than a photon rocket, namely P/E = 1/c.

At the risk of stating the blindingly obvious, for a moving particle P/E = (mv)/(0.5mv^2) = 2/v

and so for slow v, P/E is much larger than a photon rocket.

So what? Well, if the EM field transfers energy to kinetic energy of electrons within the copper, which then collide with the frustrum (copper atoms) transferring momentum to it, then the ratio of momentum to energy could be high.

I'm not sure if this type of interaction would be captured in Lorentz forces generated by the EM field on the Frustrum and its eddy currents.

Does not explain how momentum leaves the frustrum...

<<At the risk of stating the blindingly obvious>>  that fact has not escaped the attention of the people in this thread. 

Take a gander at the last column of this table that we have endeavored to populate with data ("unobtanium" or difficult to obtain otherwise elsewhere):  http://emdrive.wiki/Experimental_Results

and ask yourself why have we bothered from the very beginning to relate the experimental results to a photon rocket, when none of the EM Drive researchers have reported data that way ?

As to  "not seeing obvious progress" ... progress, like beauty is in the eye of the beholder.  I see progress.

Sometimes it is difficult to see progress being made when one is making sausage.

For example, go to the field "Members" and look for WarpTech, and take a gander at his contributions in this regard.
« Last Edit: 06/29/2015 09:17 PM by Rodal »

Offline WarpTech

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Views of NSF-1701 are up:

https://drive.google.com/folderview?id=0B1XizxEfB23tfklENXg2TWhrbUhneGxZQzJ0VVhkRFRwUUhCN2xKX24yOGM2bFQzdVV5NlE&usp=sharing

This file shows the 18 views of the E and H components from x, y and z directions.
This is from a Meep model of rfmwguy's 10.2 inch cavity, in copper, driven by a 2.45000 GHz continuous Ez source. The resonant frequency of this cavity is somewhere close to 2.45 GHz but no resonance solutions indicate exactly 2.45 GHz. The continuous source used in this model is ideal and exact. There are no "shoulders" on the input power source, all input energy is at exactly the drive frequency, 2.45 GHz. The antenna model, a dipole, is oriented perpendicular to the central axis of rotation, one-half wavelength from the small end, and is 0.058 meters long.

An important point is to note that these views use a fixed Max/Min range of power/color intensity. I'll leave it to the experts to analyse the characteristics shown.

Since we continue without having any numerical result, we have to resort to some heuristic as following to interpret these pictures:

1) Picture showing fractal are a numerical artifact due to values close to zero, hence pictures with fractals should be interpreted as low values close to zero

2) Concentrate on images showing smooth and persistent contours (persistent in several frames)

3) Use the field in the longitudinal x direction to determine mode shape

4) Conduct independent eigenvalue analysis to determine frequencies of several modes at 10.2 inches.


///////////////////

Using the above-mentioned heuristics, we determine:

1) The strong field in the longitudinal x direction is Ex, in this case Ex -y (the electric field in the longitudinal direction, seen in the x-z plane with normal y).  This field shows 4 wave patterns in the longitudinal direction.  Hence p=4.  Notice that Ex - z is zero.

2) Hx  -y and Hx -z are fractal hence interpreted as close to zero

3) Actually all magnetic fields in this case appear to be fractal, hence interpreted as very low, close to zero

4) Ez is strong both in the planes with y and z normals.  Both show p=4

5) The strong Ex points towards a TM mode.  The lack of any strong H field in the transverse direcitons points towards a TE mode

I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

IMO, it's most likely due to the antenna being 1/2 wavelength from the small end instead of the 1/4 wavelength needed for resonance. This will cause a "beat" superimposed on the resonant wave. I can see in the pattern the 1/2 wavelength coming into play, and that's not going to resonate well off a reflector.
Todd

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Question: Is it possible that such "superposition" of several modes caused the propagated trust ??? if one mode is more located in the bigger region and the other all over the cone? There are more field-nodes at the bigger end in the x-direction... that looks realy different to the small end.

Yes, as happens with parametric vibrations, we could have coupling of modes favoring some nonlinear response.

For example: think of the coupling between torsional vibration and bending vibration of a wing leading to aeroelastic flutter and aerolastic divergence.

Imagine Shawyer trying to make sense of aeroelastic flutter back in WWI :)))  .  How would he describe it?

To understand aeroelastic flutter one has to solve coupled systems of differential equations: nobody with the EM Drive is doing this.  Instead we get talk about "the EM Drive likes vibration" "the EM Drive likes background forces"  "The EM Drive has thrust pointing in the opposite direction than acceleration"


This valuable Meep run adds to pointing out another source of lack of robustness  in the EM Drive research:

1) only one organization has actually verified the mode shape: (NASA that verified TM212).  Neither Shawyer or Yang ever provided any experimental verification of mode shapes being excited

2) the EM Drive researchers up to now have not analyzed theoretically or numerically a spectrum superposition.  They have performed eigenvalue analysis assuming that only one mode was being excited.  Shawyer who has been working on this the longest, according to TT uses a kludgy spreadsheet that assumes cylindrical cut-off of modes, pure mode shape excitation and cylindrical formulas. 

3) the fact that multiple mode participation is practically possible makes the analysis of the EM Drive data more difficult to interpret. 

4) add this to the already known issues of thermal expansion shifting the natural frequencies

5) add to this the effect of the RF feed: Yang using a waveguide, many using a magnetron, others not, and so on and on.

6) add to this the never settled, always fluctuating nature of the response due to the RF feed always being on, emitting more and more photons: there is never a state of just standing waves, as assumed by Egan.  We have travelling waves, standing waves and evanescent waves.

7) no wonder that robustness in measured results is so elusive and that the statistical distribution of results is so huge...

... hopefully continued analysis can shed further light into this. 

We need all three types of analysis:

theoretical,

numerical and

experimental

all hand-in-hand to understand what is going on.
Geez Jose have you nailed it! Great analysis and I couldn't agree more on your call.

I'm still working on dimensions and layout of the Helical Cone Antenna that hopefully will provide a wider frequency response to the ~2.45 Ghz Magnetron and excite more modes across a wider range around the 2.45 Ghz similar the the chart.
http://www.intechopen.com/source/html/16867/media/image32.jpg
I'm not sure if this cone antenna will help or worsen the situation we think is happening.

It would be interesting to see if Aero could input more than one base frequency into the antenna(s) during the same run to clear up the mode actions we see in the current meep run.

Anyway, great work Aero and Jose.

Shell

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Views of NSF-1701 are up:

https://drive.google.com/folderview?id=0B1XizxEfB23tfklENXg2TWhrbUhneGxZQzJ0VVhkRFRwUUhCN2xKX24yOGM2bFQzdVV5NlE&usp=sharing

This file shows the 18 views of the E and H components from x, y and z directions.
This is from a Meep model of rfmwguy's 10.2 inch cavity, in copper, driven by a 2.45000 GHz continuous Ez source. The resonant frequency of this cavity is somewhere close to 2.45 GHz but no resonance solutions indicate exactly 2.45 GHz. The continuous source used in this model is ideal and exact. There are no "shoulders" on the input power source, all input energy is at exactly the drive frequency, 2.45 GHz. The antenna model, a dipole, is oriented perpendicular to the central axis of rotation, one-half wavelength from the small end, and is 0.058 meters long.

An important point is to note that these views use a fixed Max/Min range of power/color intensity. I'll leave it to the experts to analyse the characteristics shown.

Since we continue without having any numerical result, we have to resort to some heuristic as following to interpret these pictures:

1) Picture showing fractal are a numerical artifact due to values close to zero, hence pictures with fractals should be interpreted as low values close to zero

2) Concentrate on images showing smooth and persistent contours (persistent in several frames)

3) Use the field in the longitudinal x direction to determine mode shape

4) Conduct independent eigenvalue analysis to determine frequencies of several modes at 10.2 inches.


///////////////////

Using the above-mentioned heuristics, we determine:

1) The strong field in the longitudinal x direction is Ex, in this case Ex -y (the electric field in the longitudinal direction, seen in the x-z plane with normal y).  This field shows 4 wave patterns in the longitudinal direction.  Hence p=4.  Notice that Ex - z is zero.

2) Hx  -y and Hx -z are fractal hence interpreted as close to zero

3) Actually all magnetic fields in this case appear to be fractal, hence interpreted as very low, close to zero

4) Ez is strong both in the planes with y and z normals.  Both show p=4

5) The strong Ex points towards a TM mode.  The lack of any strong H field in the transverse direcitons points towards a TE mode

I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

IMO, it's most likely due to the antenna being 1/2 wavelength from the small end instead of the 1/4 wavelength needed for resonance. This will cause a "beat" superimposed on the resonant wave. I can see in the pattern the 1/2 wavelength coming into play, and that's not going to resonate well off a reflector.
Todd
Will 1/4 wave allow the build up of energy between the antenna and endplate IMHO is important?

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...I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

IMO, it's most likely due to the antenna being 1/2 wavelength from the small end instead of the 1/4 wavelength needed for resonance. This will cause a "beat" superimposed on the resonant wave. I can see in the pattern the 1/2 wavelength coming into play, and that's not going to resonate well off a reflector.
Todd
The problem is that when people discuss "1/4 wavelength" or "1/2 wavelength" what wavelength are they talking about ?

As I have shown, and you can also see in Meep's results the wave-patterns do not form equal-1/4-wavelength inside the frustum.  The functions governing the distribution are not sines and cosines.  They are spherical Bessel functions that support unequal wavelength.

And you don't know ahead of time whether you are going to have 3 or 4 wave-patterns in the longitudinal direction (it alternates between both in this latest case)

So, in order to know the optimal location of the antenna one has to know the solution, which depends on the antenna location.  So it is an iterative process where one has to model many antenna locations.

And since I'm talking about antennas, Yang did not use an antenna, she used a waveguide to couple the power to the EM Drive, and she got the highest response ever.

And how do particle accelerators feed power to their cavities ? Yes, you guessed it: using waveguides instead of antennas.
« Last Edit: 06/29/2015 10:19 PM by Rodal »

Online aero

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@SeeShells

Yes, I can add as many sources as I want. But someone else must tell me what and where. And will that help the experimenters or theorists? I wonder if the experimenters here will be able to do add many different sources. Just the problem of coming up with the equipment and materials applied in such a way as to avoid degrading the measurements.

And what is the noise bandwidth of a magnetron?
Retired, working interesting problems

Offline SeeShells

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...I am not sure with p=4. Some times it  looks like p=3, a few frames later it looks like p=4 like you mean.
Maybe this is a degenerate state of 2 different modes close to each other?

IMO, it's most likely due to the antenna being 1/2 wavelength from the small end instead of the 1/4 wavelength needed for resonance. This will cause a "beat" superimposed on the resonant wave. I can see in the pattern the 1/2 wavelength coming into play, and that's not going to resonate well off a reflector.
Todd
The problem is that when people discuss "1/4 wavelength" or "1/2 wavelength" what wavelength are they talking about ?

As I have shown, and you can also see in Meep's results the wave-patterns do not form equal-1/4-wavelength inside the frustum.  The functions governing the distribution are not sines and cosines.  They are spherical Bessel functions that support unequal wavelength.

And you don't know ahead of time whether you are going to have 3 or 4 wave-patterns in the longitudinal direction (it alternates between both in this latest case)

So, in order to know the optimal location of the antenna one has to know the solution, which depends on the antenna location.  So it is an iterative process where one has to model many antenna locations.

And since I'm talking about antennas, Yang did not use an antenna, she used a waveguide to couple the power to the EM Drive, and she got the highest response ever.

And how do particle accelerators feed power to their cavities ? Yes, you guessed it: using waveguides instead of antennas.
Nice thing about a waveguide is it's not truly stuck in the "middle" of the frustum like the very point source of a dipole antenna. Waveguides I believe would exhibit different patterns when injecting into the cavity. Plus the frequencies passed by the wave guide is better than an antenna.

This is beyond what I could do, time and brains are not there. :)  I thought of designing a comb microwave filter that could select and pass the mode frequencies from a magnetron down a wave guide into the Frustum and not even worrying about a PITB antenna. (Maybe if I got more $$$ than peanuts retirement I could play).

shell

Offline SeeShells

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@SeeShells

Yes, I can add as many sources as I want. But someone else must tell me what and where. And will that help the experimenters or theorists? I wonder if the experimenters here will be able to do add many different sources. Just the problem of coming up with the equipment and materials applied in such a way as to avoid degrading the measurements.

And what is the noise bandwidth of a magnetron?

http://file.scirp.org/Html/8-9801080%5C7aa0f806-9c62-4bf5-ae30-1c09e7756ab9.jpg
This help?

Company... need to get but will be back.
Shell

Offline SeeShells

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@SeeShells

Yes, I can add as many sources as I want. But someone else must tell me what and where. And will that help the experimenters or theorists? I wonder if the experimenters here will be able to do add many different sources. Just the problem of coming up with the equipment and materials applied in such a way as to avoid degrading the measurements.

And what is the noise bandwidth of a magnetron?

http://file.scirp.org/Html/8-9801080%5C7aa0f806-9c62-4bf5-ae30-1c09e7756ab9.jpg
This help?

Company... need to get but will be back.
Shell
http://file.scirp.org/Html/8-9801080_2771.htm
Later...

Offline cej

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I just read Mr. Traveller claim on reddit that the vibration increase the thrust of the EmDrive. May I ask you folks if there was already a debate about it here? I would be glad to read about it bit more.

I have summarized my interpretation of Shawyer's/TheTraveller's claims here, and talked a little more about its implications here. If my understanding is correct, then I am very concerned that the experiments we've seen so far are not adequately addressing Shawyer's claims.

In short, one claim is that an EM Drive is an "inertial ratchet": it resists a change in momentum in one direction, and amplifies a change in the opposite direction. The general mechanism by which this is proposed to work is: by maintaining some "angular momentum" (e.g. the EM field, in the case of the EM drive), the ratchet must oppose changes that would increase its angular momentum, and amplify changes that would decrease its angular momentum -- all in order to obey conservation of momentum. A perfect inertial ratchet would negate acceleration in one direction and amplify acceleration in the other (extracting energy from its angular momentum), regardless of its own mass. Another claim is that this inertial ratchet effect can extract work from external vibrations.

I am not certain whether these are reasonable claims. And I suppose the reason why I am painstakingly trying to clearly describe what these claims are is so that they can be properly critiqued. Because TheTraveller's descriptions were so vague, I don't think it was really possible for anyone here to unequivocally refute them.


The magnitude and frequency of the vibration that facilitates the measurement of the EM Drive is never addressed.

Nor have any of the public experiments tried to measure these parameters. :(

Is the EM Drive an equal opportunity friend of all magnitudes and frequencies of vibration?   This is implied, but it leads to absurd nonsense: is nanometer amplitude vibration enough ? How about picometer amplitude vibration?  At what level the boundary between vibration in continuum mechanics and quantum mechanics uncertainty is breached ?

I think you make a good point: if it is an inertial ratchet, it is certainly not going to be perfect and the effect will probably be limited to a range of impulses. This range could probably be tuned by adjusting the cavity dimensions and material properties of the drive (electrical resistance, elasticity, mass, etc.). But it is not unheard of to extract work from molecular vibrations when there is a pressure gradient (e.g. a Brownian ratchet or a balloon). An inertial ratchet would effectively induce a pressure gradient, but you would have to input energy to maintain it because the vibrations would also be depleting its angular momentum.

One note I would like to add on this subject:   If Shawyer's em-drive does not produce any thrust in the absence of vibration then it will not work in outer space.   Space is a vacuum and sound waves don't travel in space.   There would be no vibrations to "stimulate" the em-drive.

I disagree -- you are forgetting that the EM Drive would be only one component of a space ship. All other components attached to it would very certainly be vibrating and could contribute toward extracting work from an inertial ratchet. But those vibrations might not fall within the range of impulses that it can respond to, as Rodal brought up.

But frobnicat suggested that you could instead attach the drive to an oscillating spring with a mass at the other end, which could be tuned within the ratchet's impulse response range. In any case, it remains to be seen whether the energy required to maintain both the ratchet's angular momentum and the vibrations for the ratchet to extract work from is any more efficient than a photon rocket.


(...)
Attaching a vibrator to the drive is not hard. (...)
That presumes that all you have to do to get space propulsion is to have internally generated forces (in this case vibration), internal to the spacecraft, that further violates the principle of conservation of momentum.  I think that zen-in was looking at externally-forced vibration, in order to try to not break conservation of momentum.

Would conservation of momentum still be violated if extracting work from the vibrations in turn eliminate those vibrations? (At the limit, causing the space ship to go into a deep freeze.) And as for external vibrations, what if the drive can be tuned such that it extracts work from external QV fluctuations?


On the other hand, a perfect inertial ratchet would resist all acceleration. So if you were in Earth orbit, then you could simply orient the ratchet against Earth's gravity field and you would fly away tangentially -- all for just the cost of restoring its angular momentum from heat/friction losses. Even if the ratchet only reduces the effect of gravity, it might still lower the amount of fuel required to escape orbit as you use your conventional rocket to increase your angular velocity. Note that in this configuration, the rocket would be oriented orthogonal to the ratchet so that its angular momentum is kept roughly static (lost only to heat/friction/vibrations).
« Last Edit: 06/30/2015 12:28 AM by cej »

Offline Silvercrys3467

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Been following this thread for a few weeks, decided to hop in to help if I could.

Aero, do you need only the most recent MEEP package?
I was going to go ahead and compile it from source for you but I found:
http://ab-initio.mit.edu/wiki/index.php/Meep_Download

According to the wiki, they have a precompiled source package available:
"apt-get install meep h5utils"

There is also a parallel source file:
"apt-get install meep-mpi"

If you need other packages compiled with it or the OpenMPI version, I will see what I can do.

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