Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1871889 times)

Offline TheTraveller

Just to throw another log on the fire in Bringing Light into the Dark.

In the 2010 Chinese paper, Prof Yang discloses the equation they use to calculate cavity Q. Yes that is right, they don't measure Q, they calculate it from their in-house developed equation.

Search for equation 14 in the 2010 paper:
http://www.emdrive.com/NWPU2010translation.pdf

Quote
The quality factor of this resonator under no load can be calculated by the following equation:
Qu=∫|H|2dv/h/2∫|nxH|2ds+tgd∫|H|2dv = (14)
Where tg is the electric loss within the cavity, n is the normal vector of the wall, s is the cavity surface area, v is the volume of the cavity.

Who will be the 1st to post an Excel spreadsheet that duplicates Prof Yang's equation?
Sorry mr t, this is an arbitrary equation of limited value imo. One must ask why estimate when one can measure.

My point is this equation is what the Chinese use when they quote device Q. They don't, as far as I know, measure the quoted devices Q.
Seems like it mr t...with all the proper gear in their lab, why they chose not to measure is beyond me.

At least now we know how they calculate their reported Q.

So one step forward, a bit further out of the Dark.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline mwvp

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Thanks for the comments and suggestions.

Your welcome. Very happy to help - can't wait to see your drive work and figure out how its doing it.

I would suspect a typical antenna's Q would be 1, being energy in per cycle would equal energy lost (radiated) per cycle so no need to measure Q.

Not exactly. Best case is a tuned, long, thick conductor. A dipole is around 70 ohms, free space is 377 or so; antennas have an (evanescent) near field, which isn't radiated. The thicker the conductor or antenna width, the wider the bandwidth.

The antenna has an effective "radiation resistance". An AM radio ferrite loop antenna is a "high Q" antenna. They're called "electrically short" antennas. Typically poor radiation resistance to dielectric/ferrite/conductor loss. So your ferrite bar & tuning cap may have a Q of 100, and IIRC radiate < 5% of its power and make 95% heat from its losses.

You can tune up the transmitter and coax to an electrically short antenna for very low VSWR, and it will still suck because the energy isn't going to be radiated so much as heat the little antenna.

1st at very low power it can sweep the output frequency back and forth, by varing the Rf gen frequency, looking for the lowest VSWR around my spreadsheets calculated resonate frequency as lowest VSWR is the same thing as the highest return loss.

I think high reflected power for high return loss (say, -3db). A low reflected power (-20db) I suppose you might call high because its a bigger negative number, but -3db is 1/2 and -20db is 1/100. But its been a long time...

For this application, it doesn't matter that the Rf amps output impedance is not calibrated to any standard. It only matters that the VSWR reported by the Rf amp, when driving the cavity, is as low as possible as that means the input and output impedances of the 2 devices are as closely matched as possible and that the cavity will accept the max Rf energy it can, while rejecting the min Rf energy it can.

I would be shocked if it isn't 50 ohms.

Further by doing real time monitoring of the VSWR, while the Rf amp is driving the cavity, my embedded micro controller can detect when conditions inside the cavity have changed and the Rf gen's frequency needs to be adjusted to stay in the middle of the cavities resonance curve.

As an ex ham, I don't see why an antenna can't have a bandwidth measured at it's -3dB points as determined by converting the measured VSWR change, caused by deliberate Rf gen frequency change, into return loss dB change to determine the -3dB points from the peak return loss or lowest VSWR.

As with the difference between the dipole and the AM ferrite loop, or a tiny BaTiO:Zr dielectric puck for GPS. You can tune the coax to a Z-matched high-Q network fine, with VSWR meter. But does it really give you the Q of the network if you've got a length of un-tuned coax going to it, and the cavity feed and transmitter are also not perfectly matched?

Several variables involved, but the largest probably is the resonances and anti-resonances of the high-Q cavity. I think its best to put on a monitoring port. 1/16" hole with a tiny wire, maybe only 1/16" in, far from the feed point. But I've never messed with cavities before.

Offline TheTraveller

Thanks for the comments and suggestions.

Your welcome. Very happy to help - can't wait to see your drive work and figure out how its doing it.

I would suspect a typical antenna's Q would be 1, being energy in per cycle would equal energy lost (radiated) per cycle so no need to measure Q.

Not exactly. Best case is a tuned, long, thick conductor. A dipole is around 70 ohms, free space is 377 or so; antennas have an (evanescent) near field, which isn't radiated. The thicker the conductor or antenna width, the wider the bandwidth.

The antenna has an effective "radiation resistance". An AM radio ferrite loop antenna is a "high Q" antenna. They're called "electrically short" antennas. Typically poor radiation resistance to dielectric/ferrite/conductor loss. So your ferrite bar & tuning cap may have a Q of 100, and IIRC radiate < 5% of its power and make 95% heat from its losses.

You can tune up the transmitter and coax to an electrically short antenna for very low VSWR, and it will still suck because the energy isn't going to be radiated so much as heat the little antenna.

1st at very low power it can sweep the output frequency back and forth, by varing the Rf gen frequency, looking for the lowest VSWR around my spreadsheets calculated resonate frequency as lowest VSWR is the same thing as the highest return loss.

I think high reflected power for high return loss (say, -3db). A low reflected power (-20db) I suppose you might call high because its a bigger negative number, but -3db is 1/2 and -20db is 1/100. But its been a long time...

For this application, it doesn't matter that the Rf amps output impedance is not calibrated to any standard. It only matters that the VSWR reported by the Rf amp, when driving the cavity, is as low as possible as that means the input and output impedances of the 2 devices are as closely matched as possible and that the cavity will accept the max Rf energy it can, while rejecting the min Rf energy it can.

I would be shocked if it isn't 50 ohms.

Further by doing real time monitoring of the VSWR, while the Rf amp is driving the cavity, my embedded micro controller can detect when conditions inside the cavity have changed and the Rf gen's frequency needs to be adjusted to stay in the middle of the cavities resonance curve.

As an ex ham, I don't see why an antenna can't have a bandwidth measured at it's -3dB points as determined by converting the measured VSWR change, caused by deliberate Rf gen frequency change, into return loss dB change to determine the -3dB points from the peak return loss or lowest VSWR.

As with the difference between the dipole and the AM ferrite loop, or a tiny BaTiO:Zr dielectric puck for GPS. You can tune the coax to a Z-matched high-Q network fine, with VSWR meter. But does it really give you the Q of the network if you've got a length of un-tuned coax going to it, and the cavity feed and transmitter are also not perfectly matched?

Several variables involved, but the largest probably is the resonances and anti-resonances of the high-Q cavity. I think its best to put on a monitoring port. 1/16" hole with a tiny wire, maybe only 1/16" in, far from the feed point. But I've never messed with cavities before.

An yes the Ferrite bar antenna. Forgot about those. Clever devices.

Been doing more reading on measuring unloaded Q in microwave resonators using both S11 and S21 techniques.

Seems it is acceptable to do unloaded cavity Q measurements based only on S11 reflected data. Issue is that the S11 technique and data can't do a good job measuring loaded cavity Q, which is where the S21 technique shines.

For EMDrive Force prediction the variety of the Q used is the unloaded variety, which can be measured via S11 reflectance.

What I see is the EMDrive cavity loads the Rf amp like an antenna does but unlike a conventional microwave cavity, the EMDrive cavity has only one Rf in port.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline Rodal

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ELECTROMAGNETIC STRESS (2nd order tensor of Force/UnitArea calculation for the EM Drive)

After having reported the first published calculations of the Poynting vector (momentum density components in the relativity energy-stress tensor) for

a) initially for the exact solution (standing waves with RF Feed OFF)
and, lately for:
b) transient Finite Difference (using Meep) solution for RF feed ON,

we now report  the first published calculations of the Stress tensor







is the electromagnetic tensor and where is the Minkowski metric tensor of metric signature (−+++)





(*)
(**)

obtained using Wolfram Mathematica ( http://www.wolfram.com/mathematica/ ) , post-processed from the transient Finite Difference (using Meep) solution for RF feed ON for an EM Drive.

0) The highest stress by far is the one produced by the antenna.  It appears that the stress at other locations along the longitudinal axis of axi-symmetry is due to the antenna.

1) On the copper circular perimeter the stress tensor component sigma xx (acting normal to the circular cross section plane) fluctuates in certain locations (for example along the conical lateral surface at positions x=97 and x=149).  We naturally expect that the stress tensor on the copper itself should sum up to zero in order to satisfy the momentum equilibrium equation implied by Maxwell's equation. Intriguingly,  the stress tensor component sigma xx (acting normal to the circular cross section plane) in the copper at the location nearest the big base x=38 is consistently acting in the direction predicted by Roger Shawyer for the big base: pressing on it.  We need to also calculate in the future -not tonight :)  - the stress on the copper big base to see whether it agrees or not with Roger Shawyer's conjecture, and most importantly we need to also calculate the stress at the small base.

2) Along the longitudinal axis (x) of axi-symmetry of the EM Drive the stress tensor component sigma xx (acting normal to the circular cross section plane) reaches its maximum value in the interior of the EM Drive and it is consistently pressing.  In the calculated grids shown below (on the axis) the harmonic variation of the stress tensor is alternating between zero and it maximum value, at twice the frequency of the electromagnetic field.   Possibilities are that:

a) the stress tensor is pressing on a classical field (for example ionized plasma resulting from moist air inside the cavity) if it leaks out as an exhaust or
b) a non-classical field (i.e. axionic dark matter, or more controversial conjectures like the mutable, degradable Quantum Vacuum of Dr. White, or violation of p-t symmetry in QV, etc.)

3) Due to the fact that the studied cycles are after only 0.01 microseconds from RF feed turning on, this is very early in the process and hence the stress tensor is a million times smaller than in reported measurements.  However it is growing exponentially with time.  Based on extrapolation it would be required more than a hundred times longer (longer than one microsecond) at this exponential rate for the stress tensor to reach the reported values.

4) Now we have a more quantitative method to establish whether different antenna arrangements or mode shapes, or geometries may be better than others, to maximize the electromagnetic stress in the longitudinal direction perpendicular to the circular cross-sections.


 @aero has made available a number of csv files at 4 internal locations in the longitudinal x direction: at x=38, x=97, x=149, and x=208 (x ranging from 1 to 245, with x=1 at the extreme end beyond the big base and x= 245 at the extreme end beyond the small base).  The plane x=208 is near the antenna, and x=149 is the very important wave that is downstream of the antenna in the direction towards the big base.

See the very last picture attached below (showing the Poynting vector field)  to locate the 4 locations x=38, x=97, x=149, and x=208, where the x axis is the horizontal axis in the last picture

We start by showing the stress component sigma xx in the circular cross-sectional yz plane at  x=38, located on the interior, closest to the big end

EDIT:

1) Magnitude of stress is dependent on input power set for antenna.  Aero needs to inform what this input power is.

2) Blue is minimum and Red is maximum.  A plot ranging from 0 to +0.02 will show a blue plane for 0, while a plot ranging from 0 to -0.02 will show a red plane for 0.  A plot ranging from +0.02 to -0.02 will show a green plane for 0. It was easier for me to set PlotRange to Automatic, than to run through all the Max and Min and having to re-set all the Plots to be rendered to the same Max Min color rendering scheme.  At the beginning of the computation we don't know what the Max Min are going to be, so it is more expedient to set the range to Automatic.  The Max Min color rendering scheme can only be done post-fact after the results have been obtained for a cycle.

__________

(*)  (where we denote by sigmaxxxx= T11 the contravariant component of the tensor acting along the longitudinal direction "x" of the EM Drive, normal to the the plane yz having normal x, where direction "1" is "x")

(**) For the copper diamagnetism is assumed such that the magnetization M is assumed proportional to the applied magnetic field such that for free space it is assumed that M is zero in free space in the relationship 
« Last Edit: 07/16/2015 01:24 AM by Rodal »

Offline Rodal

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We continue by showing the stress tensor component sigma xx at the circular cross-sectional yz plane at  x=97, located on the interior, between the big end and the middle of the frustum
« Last Edit: 07/13/2015 02:00 AM by Rodal »

Offline Rodal

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We continue by showing the stress tensor component sigmaxx at a most important circular cross-sectional yz plane at  x=149, located on the interior, between the  middle and the antenna
« Last Edit: 07/13/2015 02:03 AM by Rodal »

Offline Rodal

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We finish by showing the stress tensor component sigma xx at the circular cross-sectional yz plane at  x=208, located on the interior, near the antenna, near the small end of the frustum
« Last Edit: 07/13/2015 02:06 AM by Rodal »

Offline rfmwguy

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Impressive doc, nicely done...

Offline Rodal

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Stress tensor component sigma xx (acting normal to the circular cross section plane) plotted  vs time (data points interpolated using cubic splines)

The total time from start of the RF feed in the Meep response analysis to the very last step is: 
 320 ( time slices) * 4.082199*10^(-11) seconds/timeSlice =
                                          = 0.013063 microseconds

Each "time slice" step is 4.082199*10^(-11) seconds/timeSlice

Duration of the total of 13 time slice steps = 53.068 *10^(-11) seconds

Last time step is at 0.013063 microseconds from the start of the RF feed ON


___________________________________________________________
Conversion to get SI Units from the graphs and equations in Meep units:

TIME:  Multiply Meep Time Slice "t" in the horizontal axis and in the formulae by the following factor:

((Total Meep Time)/(#Time Slices))*((Length Scale Factor)/(Speed of Light in Vacuum)) =
                                                                                                           =((13.054)/(320))*((0.3)/(299792458))
                                                                                                           =4.082199*10^(-11) seconds/timeSlice



ASSUMPTIONS: the validity of the following data:

Number of time slices for the total run = 320
Number of Meep time units for the total run = 13.054
Meep Length Scale factor= 0.3 meters
Meep Current (Io) = 1
« Last Edit: 07/13/2015 02:36 AM by Rodal »

Offline Ricvil

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Nice. The graph shows the mixing of the modes as a function of cavity shape.
There is a choice of frequency, and dimension on graph. Any specific motivation?
No idea.

I'm looking for a configuration when there is one hybrid mode, followed by any other mode very close.
Why? Because I think there is another thing interacting with the electromagnetic field of cavity.
This thing probally will have a very small coupling with the electromagnetic field.
To enhance this coupling I need:
- A mode excited by a source puting the max energy on cavity
- At least one second mode with frequecy very close to the first but not excited by the source.
In this situation, when a small region of the cavity has its electromagnetics properties changed to anything different of vacuum (epslon0 and mu0), then this little "scatter" region triggers a very strong perturbation called "ghost mode".
In waveguides "ghost modes" are caused by deformations or imperfections on waveguide, but in principle, any "pertubation" can cause this effect.
This "ghost modes" can in some situations, reflect almost all power flux in the waveguide, and the "scatter" will be under very strong radiation pressure.
I don't know if this case can be considered also a type of Fano resonance, but I think if I want some type of interaction of the field inside of cavity with some "other thing", I would try  to maximize this interaction with this setup.

To me this thing is the axion field/particle. To others can be particles from "quantum vacuum" or a space-time flutuactions, but the result of the ghost mode arising is the same,  change the incidence of electromagnetic radiation on the walls of cavity.

I had to look up ghost mode and Fano reasonance, interesting stuff to know. Perhaps explains why putting a dielectric in the frustrum is a bad thing. Dielectric loss aside, it could cause ghost modes if there are nearby modes available. Lots of google hits on microwave/klystron windows pertaining to ghost modes. Wikipedia notes microwaves are associated with Fano resonance. A 1958 paper by Jaynes http://bayes.wustl.edu/etj/articles/ghost.modes.pdf notes that microwave ghost modes have a similarity to localized imperfections in crystalline periodic structures (such as dopants) leads to bound states that overlap the conduction band. If that Fano resonance too? I'll have to absorb that awhile. I have no idea how that could conjure axions out of the qv.

In axion electrodynamic, the axion field equation has as source of the field a term like alfaE.B (dot product), where alfa is the coupling constant between the E and B fields and the axion field. For EM  fields distribuitions where E.B different from zero ( like in hybrid modes) the the axion field is very small ( because the coupling constant) but different from zero.
For the other side, when a axion field is present, they act as a metamaterial medium with very interesting properties like create Poynting vectors vortices as example.
The idea is to enhance the "ghost mode" effect caused by axion "metamaterial" scatter field.
« Last Edit: 07/13/2015 03:24 AM by Ricvil »

Offline SeeShells

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You know if all those images were in the same plane you could stack them into a video.

Long day off to bed.

Nite
Shell

Beautiful work!

Offline WarpTech

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...
Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.

Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.

rfmwguy, a big thanks from me, and a big applause,  for clarifying this issue: you are 100% right. 

The Q should be measured using two port S21.

All Q measurements using S11 are suspect: everybody should take with a grain of salt the reported Q's from different EM Drive researchers, unless the procedure to measure the Q is detailed and they have used S21.

Hence, why I ignored them and calculated the change in energy required for a given thrust, rather than a thrust given the reported stored energy based on Q. I don't trust the data.
Todd

Offline WarpTech

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Resolution of the Space-Drive Energy Paradox  (version 6)

Have at it @deltaMass and @wallofwolfstreet. I'm looking forward to your responses.

https://www.dropbox.com/s/p86dvc8733h9iph/Desiato-Energy_Paradox-v6.pdf?dl=0

Todd

Offline TheTraveller

...
Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.

Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.

rfmwguy, a big thanks from me, and a big applause,  for clarifying this issue: you are 100% right. 

The Q should be measured using two port S21.

All Q measurements using S11 are suspect: everybody should take with a grain of salt the reported Q's from different EM Drive researchers, unless the procedure to measure the Q is detailed and they have used S21.

Hence, why I ignored them and calculated the change in energy required for a given thrust, rather than a thrust given the reported stored energy based on Q. I don't trust the data.
Todd

Shawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.

So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.

Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak.

It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.
« Last Edit: 07/13/2015 04:44 AM 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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Got up to get a glass of milk and while browsing the clickbates I ran across the competitions extreme mass thruster. What could go wrong?

http://phys.org/news/2015-07-boeing-patent-focus-laser-powered-propulsion.html

Offline WarpTech

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...
Here is where they went wrong...under no industrial RF standard does anyone measure Q on return loss, S11. It is done on S21, forward power in the frequency domain for cavities. I stand by my claim that "Specsmanship" was used to create an unnaturally large Q, either by unfamiliarity or intent.

Note that S21 requires a 2 port measurement, input and output (note the sampling port on the frustums will provide the output). I'd bet a six-pack of craft beer that realistic Qs are in the 4 digit range for both shawyer and yang. And yes Doc, Yang should have used the -3dB points below 0 insertion, not -3dB above best return loss...not RF types IMHO.

rfmwguy, a big thanks from me, and a big applause,  for clarifying this issue: you are 100% right. 

The Q should be measured using two port S21.

All Q measurements using S11 are suspect: everybody should take with a grain of salt the reported Q's from different EM Drive researchers, unless the procedure to measure the Q is detailed and they have used S21.

Hence, why I ignored them and calculated the change in energy required for a given thrust, rather than a thrust given the reported stored energy based on Q. I don't trust the data.
Todd

Shawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.

So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.

Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak.

It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.

IMO, it would be more important to measure the energy and frequency stored at the small end, vs the energy and frequency stored at the big end, and maximize the difference. The Q means nothing, what matters is the difference in potential energy between the two ends.
Todd

Offline mwvp

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Shawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.

So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.

Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak.

It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.

Are you sure the EMDrive will never be "loaded"? Didn't Shawyer describe it as a motor/generator depending one which direction its moving? At rest, its RF-wise at equilibrium. If it moves backwards, it generates and a reflected wave will move towards your transmitter. Moving forward, shouldn't it present a greater load on the transmitter then?

Perhaps any coax reactance (a coax with an unevent # of 1/4 wavelengths) will be absorbed/dwarfed by the cavity tuning, so perhaps S11 is good enough for tuning.

However, wouldn't it be nice to sense each of the 3 modes in a TE013 frustrum at 90 degree points, and watch the amplitude modulations/traveling wave or Sagnac effect as it spins to or fro? Or configure the taps for phase rather than amplitude measurement to measure group velocity?

Would be a good reality check for the FEA/FDTD simulations.

BTW, I'm pretty sure the transmitter will have an isolator or circulator to protect the PA from VSWR damage. If it doesn't, it may be very easy to burn it out if its tuned at high-power while the cavity is tuned through its anti-resonance.

Offline dustinthewind

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Resolution of the Space-Drive Energy Paradox  (version 6)

Have at it @deltaMass and @wallofwolfstreet. I'm looking forward to your responses.

https://www.dropbox.com/s/p86dvc8733h9iph/Desiato-Energy_Paradox-v6.pdf?dl=0

Todd

So then if one appears to be traveling near light speed then one is indeed traveling near light speed (gravitationally) even though if in the moving frame light still appears to recede at light speed.  And if space is moving in to a point at near light speed then there is no escape (event horizion).  Velocity with respect to space being absolute. 

It reminds me of a non-rotating wheel as observed from a rotating observer.  A wheel is either rotating or it is not.  For a rotating observer he cannot say the wheel that rests in the lab frame appears to be rotating so it must experience acceleration.  If all the bonds are broken the wheel will not fly apart as it does not experience acceleration.  As a result rotation with respect to a center is absolute. 
« Last Edit: 07/13/2015 07:37 AM by dustinthewind »

Offline TheTraveller

Shawyer uses unloaded cavity Q for his Force calculations as the cavity is never attached to nor filled with anything to alter it's unloaded status. The unloaded Q is all there is. As I see it, it's like a LC circuit that never drives / is connected to anything but just sits there doing it's resonate thing and has its stored energy topped up, from time to time, to replace the parasitic energy loss.

So loaded cavity Q measurements have no place in the EMDrive world as the cavity is never loaded. It is a 1 port cavity.

Unloaded cavity Q can be calculated by 1 port S11 return loss measurements based on the side frequencies that are 3 dB down from the return loss peak.

It can also be calculated, in real time, by my Control & Measurement System, based on the Rf amps VSWR output.

Are you sure the EMDrive will never be "loaded"? Didn't Shawyer describe it as a motor/generator depending one which direction its moving? At rest, its RF-wise at equilibrium. If it moves backwards, it generates and a reflected wave will move towards your transmitter. Moving forward, shouldn't it present a greater load on the transmitter then?

Perhaps any coax reactance (a coax with an unevent # of 1/4 wavelengths) will be absorbed/dwarfed by the cavity tuning, so perhaps S11 is good enough for tuning.

However, wouldn't it be nice to sense each of the 3 modes in a TE013 frustrum at 90 degree points, and watch the amplitude modulations/traveling wave or Sagnac effect as it spins to or fro? Or configure the taps for phase rather than amplitude measurement to measure group velocity?

Would be a good reality check for the FEA/FDTD simulations.

BTW, I'm pretty sure the transmitter will have an isolator or circulator to protect the PA from VSWR damage. If it doesn't, it may be very easy to burn it out if its tuned at high-power while the cavity is tuned through its anti-resonance.

Thanks for the suggestions.

My 1st goal is to prove beyond doubt my EMDrive generates Force without using any form of propellant. Other interesting stuff may happen later as the Force verifiers are doing their jobs.

All that happens in GENERATOR mode is the absorbed KE is converted into increased Rf cavity energy and finally increased cavity heat. Can't back convert the increased cavity Rf energy into electricity and shove in back into the electrical power source.

The 100W Rf amp I'll be using has inbuilt protection against high reflected power, shorted output and overheat, plus my CMS can quickly shut down the Rf amp if anything reaches the boundary conditions I set in the software. So 2 layers of protection.
« Last Edit: 07/13/2015 08:30 AM 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 dumbo

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I did not receive a reply from the FEFF project. But I have now configured an AMI image based on Ubuntu with meep installed. I have also uploaded aero's file to it. Also, for some strange reason (meep version differences?) I had to change all occurences of the type:
(define variable)
(set! variable some-value)
to
(define variable some-value)
in order to get  the simulation to start.

Also, I have wrapped the main run statement in a (synchronized-magnetic ...) statement, to avoid the situation described on the meep wiki:
Quote from: meep wiki
In the finite-difference time-domain method, the electric and magnetic fields are stored at different times (and different positions in space), in a "leap-frog" fashion. At any given time-step t during the simulation, the E and D fields are stored at time t, but the H and B fields are stored at time t − Δt / 2 (where Δt is the time-step size).

This means that when you output the electric and magnetic fields from a given time step, for example, the fields actually correspond to times Δt / 2 apart. For most purposes, this slight difference in time doesn't actually matter much, but it makes a difference when you compute quantities like the Poynting flux \mathbf{E}\times\mathbf{H} that combine electric and magnetic fields together, e.g. for the output-poynting function. If what you really want is the Poynting flux \mathbf{S}(t) at time t, then computing \mathbf{E}(t)\times\mathbf{H}(t-\Delta t/2) is slightly off from this the error is of order O(Δt), or first-order accuracy. This is unfortunate, because the underlying FDTD method ideally can have second-order accuracy.

To improve the accuracy for computations involving both electric and magnetic fields, Meep provides a facility to synchronize the H and B fields with the E and D fields in time. Technically, what it does is to compute the magnetic fields at time t + Δt / 2 by performing part of a timestep, and then averaging those fields with the fields at time t − Δt / 2. This produces the magnetic fields at time t to second-order accuracy O(Δt2), which is the best we can do in second-order FDTD. Meep also saves a copy of the magnetic fields at t − Δt / 2, so that it can restore those fields for subsequent timestepping.

Ok, so most of the configuration work is done. My questions are now:
1) How many cycles should we run?
2) Is user apoc2021's generous offer to donate server time still open?
« Last Edit: 07/13/2015 08:51 AM by dumbo »

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