Author Topic: EM Drive Developments - related to space flight applications - Thread 6  (Read 824511 times)

Offline rfmwguy

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This is a thread - Thread 6 in the series - focused on objective analysis of whether the EM Drive (a cavity resonating at microwave frequencies) reported "thrust force" is an experimental artifact or whether it is a real propulsion effect  that can be used for space applications, and if so, in discussing those possible space propulsion applications.

Objective skeptical inquiry is strongly welcome.   Disagreements should be expressed politely, concentrating on the technical, engineering and scientific aspects, instead of focusing on people.   As such, the use of experimental data, mathematics, physics, engineering, drawings, spreadsheets and computer simulations are strongly encouraged, while subjective wordy statements are discouraged. Peer-reviewed information from reputable journals is strongly encouraged.  Please acknowledge the authors and respect copyrights.

Commercial advertisement is discouraged.

In order to minimize bandwidth and  maximize information content, when quoting, one can use an ellipsis (...) to indicate the clipped material.

Only use the embed [img ]http://code when the image is small enough to fit within the page. Anything wider than the width of the page makes the page unreadable as it stretches it (we're working on auto reduction, but different browsers work different ways, etc.)

This link

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enables typing of mathematical symbols, including differentiation and integration, Greek letters, etc.

--

Links to previous threads:

Thread 1:
http://forum.nasaspaceflight.com/index.php?topic=29276.0

Thread 2:
http://forum.nasaspaceflight.com/index.php?topic=36313.0

Thread 3:
http://forum.nasaspaceflight.com/index.php?topic=37642.0

Thread 4:
http://forum.nasaspaceflight.com/index.php?topic=38203.0

Thread 5:
http://forum.nasaspaceflight.com/index.php?topic=38577.0

--

Entry level thread:
http://forum.nasaspaceflight.com/index.php?topic=37438.0

Baseline NSF Article:
http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/

This is the link to the EM Drive wiki that users are encouraged to contribute to, edit for accuracy, and build as a knowledge resource for the EM Drive:

http://emdrive.wiki
http://rfdriven.com

Chris note: Please note all posts need to be useful and worthwhile or they will be removed via moderation. This subject has large interest, with over 3.5 million thread reads and 850,000 article reads. Most people are reading and not posting, so when you post it is in front of a very large audience.

Also, and it should go without saying, amateur experiments are discouraged unless you have gained educated and/or professional advice for safety reasons.



« Last Edit: 12/14/2015 01:07 AM by rfmwguy »

Offline rfmwguy

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Chris has removed the general moderator - by mutual agreement - for this section and assigned me, an EM Drive regular, as the new moderator.

However, unlike the general moderation of the overall forum, my role here is specific to EM Drive and my role is one of a caretaker.

My suggestions are to keep posts brief with current commentary on designs, builds, tests and theories. Its about as simple as that. Also, we should recognize this thread and the much larger NSF community is viewed by a large amount of people around the world. We should strive to be civil, respectful and relevant to the topics.

I look at these threads as an interactive RSS feed or news ticker on the EM Drive. People come here to read current news about designs, builds, tests and theories. It is not ideal for archiving data sets and there are a number of websites that have volunteered to do this.

Some could read any of my future posts on EM Drive as the ultimate authority, but I am not.

Have some fun and let's have at it.

- Dave (rfmwguy)

Offline andygood

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Chris has removed the general moderator - by mutual agreement - for this section and assigned me, an EM Drive regular, as the new moderator.

- Dave (rfmwguy)

I, for one, welcome our new RF & microwave overlord!  ;)

Offline Rodal

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Re: EM Drive Developments - related to space flight applications - Thread 5
« Reply #2538 on: Today at 02:54 PM »
Quote from: ThereIWas3
I did a little Googling and found that many meep users (not just here - everywhere) ran into the negative Q problem.  It is an artifact of the way meep works, and is an indication that the simulation did not run long enough.  Decreasing the bandwidth helps too.

After some other attempts, hunting around, I finally set BW to 0.015, set the center frequency to 2.4959 GHz where it wanted to resonate anyway, and increased the runtime by a factor of 1.25.  (aero: I did this by increasing 'gc' from 8 to 10)  Now I get a positive Q, that is closer to Rodal's earlier result.  I got Q=99,938.   Also absolute amplitude went up from 4.9 to 23.5.   Error is 4.12E-7.  Runtime was about 2 hours.  Resonant frequncy came out 2.4959-1.248E-5i.

The equation I used for CU-D-conduct (which is the imaginary part of the relative complex permittivity (I should change the variable name) was posted earlier, -2*pi*2.4GHz*3.252698E+8i.  That evaluates to -4.9083E+9.   The "2.4GHz" term is actually in "meep units" so it is 2.4E+9 times 'a' divided by 'c'.

That's EXCELLENT work, @ThereIWas3, I also got Q's of ~90,000 using the exact solution for a (previous ?) geometry of the Shell Frustum (she has posted more than one geometrical shape for possible testing in the last year), depending on the input parameters (conductivity of copper, etc.). 

Please let us know what mode shape is present in the EM Drive when you have a chance, or post some images of the fields when you have a chance.

It is great to have more people running Meep.   Excellent work !

The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.  Using impure copper, together with an imperfect geometry and surface reflectivity, will bring down the quality of resonance Q to a lower value in actual testing.

______
PS: Again: no negative mass/negative energy, no dark mass, no dark energy, no leaky fields, no strange quantum effects, no microwave black magic, were responsible for a negative Q.  It was just a numerical artifact of the finite difference solution.
« Last Edit: 12/11/2015 03:20 PM by Rodal »

Offline Star One

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Chris has removed the general moderator - by mutual agreement - for this section and assigned me, an EM Drive regular, as the new moderator.

- Dave (rfmwguy)

I, for one, welcome our new RF & microwave overlord!  ;)

Seconded. Kind of biding my time at the moment over developments as I suspect that 2016 will bring a good degree of movement in that area.

Online ThereIWas3

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The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.

I think I got that number 3.252698E+8i from one of your own posts.  I have looked around the web for reference materials on more realistic real-world values but have not found a good one yet.  What units is that in?  It does not look like Siemens/meter, which is 58.6E6 for Cu.
"If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea" - Antoine de Saint-Exupéry

Offline Rodal

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The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.

I think I got that number 3.252698E+8i from one of your own posts.  I have looked around the web for reference materials on more realistic real-world values but have not found a good one yet.  What units is that in?  It does not look like Siemens/meter, which is 58.6E6 for Cu.
The background of that number is in my previous posts, with luxury of details, including a discussion of units and a discussion of a conversion to usual units.

My posts (as any user posts) can be searched by clicking on my NSF membership, and clicking "Show Posts"

For example (one of many posts on this subject):
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316

Basically it is based on a model proposed, for pure copper, by @DeltaMass.

It corresponds to a conductivity in SI units of  4.342937 E+7

As I have explained in previous messages:

1) For other material conductivities you simply have to ratio this input by the material conductivities

2) The input to MEEP should be changed for different frequencies.  The pure copper input is ONLY valid for 2.4 GHz.  At other frequencies the input should be linearly ratioed by the frequency ratio, so that the conductivity stays constant
At resonating frequencies higher than 2.4 GHz, you should input a correspondingly LOWER number to keep the conductivity constant.

At lower frequencies than 2.4 GHz you should input a correspondingly HIGHER number, so that the conductivity stays at the correct constant value.

As I wrote in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316:

Quote
only for f=2.4 E+09 Hertz one has

ε“/εo = 3.252698 E+08

while for f = 2.45 E+09 Hertz (for example) one has

ε“/εo = 3.186316 E+08

Quote from: Rodal
The conductivity in SI Units that corresponds to epsilon"=0.00288 is:

conductivity        = omega * epsilon"
                          = 2 Pi frequency 0.00288
                          = 2 Pi 2.4E+9 * 0.00288
                          = 4.342937 E+7

which is almost 10 times smaller than 3.25E+8

Please also recall that DeltaMass was conscious that it is incorrect to take 0.00288 as a constant !

That value is a function of frequency.

What is approximately constant in this regime is the conductivity itself.

DeltaMass gave you explicit instructions to keep the conductivity constant, at other frequencies:
for example, the conductivity at 1 GHz is also  4.342937 E+7, so

at 1 GHz you should input into Meep  (3.25...E+8 ) *2.4 = 7.8 E+8, for example

So, for pure Silver, for example (from the table in the link in your post),

Conductivity =  6.090E+07


So, instead of 3.25...E+8 for copper, you have to use   ( 6.090E+07/4.342937 E+7 ) *3.25...E+8 at 2.4GHz

in other words, at 2.4 GHz, your input to Meep for pure Silver should be 1.402276 times higher than for the copper value given by DeltaMass.  About 40% higher, whether in SI units or in Meep units.

In other words, everything else being the same, the quality of resonance (Q) should be about 40% higher with pure silver than with copper.



« Last Edit: 12/11/2015 05:12 PM by Rodal »

Offline SeeShells

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Re: EM Drive Developments - related to space flight applications - Thread 5
« Reply #2538 on: Today at 02:54 PM »
Quote from: ThereIWas3
I did a little Googling and found that many meep users (not just here - everywhere) ran into the negative Q problem.  It is an artifact of the way meep works, and is an indication that the simulation did not run long enough.  Decreasing the bandwidth helps too.

After some other attempts, hunting around, I finally set BW to 0.015, set the center frequency to 2.4959 GHz where it wanted to resonate anyway, and increased the runtime by a factor of 1.25.  (aero: I did this by increasing 'gc' from 8 to 10)  Now I get a positive Q, that is closer to Rodal's earlier result.  I got Q=99,938.   Also absolute amplitude went up from 4.9 to 23.5.   Error is 4.12E-7.  Runtime was about 2 hours.  Resonant frequncy came out 2.4959-1.248E-5i.

The equation I used for CU-D-conduct (which is the imaginary part of the relative complex permittivity (I should change the variable name) was posted earlier, -2*pi*2.4GHz*3.252698E+8i.  That evaluates to -4.9083E+9.   The "2.4GHz" term is actually in "meep units" so it is 2.4E+9 times 'a' divided by 'c'.

That's EXCELLENT work, @ThereIWas3, I also got Q's of ~90,000 using the exact solution for a (previous ?) geometry of the Shell Frustum (she has posted more than one geometrical shape for possible testing in the last year), depending on the input parameters (conductivity of copper, etc.). 

Please let us know what mode shape is present in the EM Drive when you have a chance, or post some images of the fields when you have a chance.

It is great to have more people running Meep.   Excellent work !

The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.  Using impure copper, together with an imperfect geometry and surface reflectivity, will bring down the quality of resonance Q to a lower value in actual testing.

______
PS: Again: no negative mass/negative energy, no dark mass, no dark energy, no leaky fields, no strange quantum effects, no microwave black magic, were responsible for a negative Q.  It was just a numerical artifact of the finite difference solution.
Top notch work to all!!!

I am using the more costly O2 free copper.
https://www.onlinemetals.com/merchant.cfm?pid=15244&step=4&showunits=inches&id=966&top_cat=87

https://www.onlinemetals.com/productguides/copperguide.cfm

Also the waveguides and the endplates are electroplated with silver which will bring up the Q just a little.

Shell

Offline Rodal

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The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.

I think I got that number 3.252698E+8i from one of your own posts.  I have looked around the web for reference materials on more realistic real-world values but have not found a good one yet.  What units is that in?  It does not look like Siemens/meter, which is 58.6E6 for Cu.
The background of that number is in my previous posts, with luxury of details, including a discussion of units and a discussion of a conversion to usual units.

My posts (as any user posts) can be searched by clicking on my NSF membership, and clicking "Show Posts"

For example (one of many posts on this subject):
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316

Basically it is based on a model proposed, for pure copper, by @DeltaMass.

It corresponds to a conductivity in SI units of  4.342937 E+7

As I have explained in previous messages:

1) For other material conductivities you simply have to ratio this input by the material conductivities

2) The input to MEEP should be changed for different frequencies.  The pure copper input is ONLY valid for 2.4 GHz.  At other frequencies the input should be linearly ratioed by the frequency ratio, so that the conductivity stays constant
At resonating frequencies higher than 2.4 GHz, you should input a correspondingly LOWER number to keep the conductivity constant.

At lower frequencies than 2.4 GHz you should input a correspondingly HIGHER number, so that the conductivity stays at the correct constant value.

As I wrote in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316:

Quote
only for f=2.4 E+09 Hertz one has

ε“/εo = 3.252698 E+08

while for f = 2.45 E+09 Hertz (for example) one has

ε“/εo = 3.186316 E+08

Quote from: Rodal
The conductivity in SI Units that corresponds to epsilon"=0.00288 is:

conductivity        = omega * epsilon"
                          = 2 Pi frequency 0.00288
                          = 2 Pi 2.4E+9 * 0.00288
                          = 4.342937 E+7

which is almost 10 times smaller than 3.25E+8

Please also recall that DeltaMass was conscious that it is incorrect to take 0.00288 as a constant !

That value is a function of frequency.

What is approximately constant in this regime is the conductivity itself.

DeltaMass gave you explicit instructions to keep the conductivity constant, at other frequencies:
for example, the conductivity at 1 GHz is also  4.342937 E+7, so

at 1 GHz you should input into Meep  (3.25...E+8 ) *2.4 = 7.8 E+8, for example

So, for pure Silver, for example (from the table in the link in your post),

Conductivity =  6.090E+07


So, instead of 3.25...E+8 for copper, you have to use   ( 6.090E+07/4.342937 E+7 ) *3.25...E+8 at 2.4GHz

in other words, at 2.4 GHz, your input to Meep for pure Silver should be 1.402276 times higher than for the copper value given by DeltaMass.  About 40% higher, whether in SI units or in Meep units.

In other words, everything else being the same, the quality of resonance (Q) should be about 40% higher with pure silver than with copper.


OK, as an example, let's calculate some numbers:

1) Since the resonant frequency you calculated was 2.4959 GHz instead of 2.4 GHz, the input instead of 3.252698 E+08 should have been:

(2.4/2.4959)*3.252698 E+08 = 3.127719 E+08

Therefore, your MEEP run's output quality of resonance Q instead of Q=99,938, would have been, at 2.4959 GHz, for DeltaMass pure copper:

Q = (2.4/2.4959)*99,938
   = 96,098

__________________________________________

2) If instead of copper's conductivity, as proposed by DeltaMass, you would have used the value for conductivity for  Bronze, Commercial (Annealed) in (http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/): 2.552E+07, the Q output would have been:

Q = (2.4/2.4959)*99,938*(2.552E+07)/(4.342937 E+7)
   =56,469

and the Meep input should have been:

(2.4/2.4959)*((2.552E+07)/(4.342937 E+7))*3.252698 E+08 = 1.837912 E+08

instead of 3.252698E+8
__________________________________________

3) If instead of copper's conductivity, as proposed by DeltaMass, you would have used the value for conductivity for Pure Silver in (http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/): 6.090E+07, the Q output would have been:

Q = (2.4/2.4959)*99,938*(6.090E+07)/(4.342937 E+7)
   =134,756

and the Meep input should have been:

(2.4/2.4959)*((6.090E+07)/(4.342937 E+7))*3.252698 E+08 = 4.385928 E+08

instead of 3.252698E+8


__________________________________________

NOTE:  See http://forum.nasaspaceflight.com/index.php?topic=39004.msg1456018#msg1456018

(Radio-frequency) investigations have shown that the conductivity of much of the commercial silver-plating is about half of that of pure copper
« Last Edit: 12/11/2015 06:42 PM by Rodal »

Offline OnlyMe

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The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.

I think I got that number 3.252698E+8i from one of your own posts.  I have looked around the web for reference materials on more realistic real-world values but have not found a good one yet.  What units is that in?  It does not look like Siemens/meter, which is 58.6E6 for Cu.
The background of that number is in my previous posts, with luxury of details, including a discussion of units and a discussion of a conversion to usual units.

My posts (as any user posts) can be searched by clicking on my NSF membership, and clicking "Show Posts"

For example (one of many posts on this subject):
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316

Basically it is based on a model proposed, for pure copper, by @DeltaMass.

It corresponds to a conductivity in SI units of  4.342937 E+7

As I have explained in previous messages:

1) For other material conductivities you simply have to ratio this input by the material conductivities

2) The input to MEEP should be changed for different frequencies.  The pure copper input is ONLY valid for 2.4 GHz.  At other frequencies the input should be linearly ratioed by the frequency ratio, so that the conductivity stays constant
At resonating frequencies higher than 2.4 GHz, you should input a correspondingly LOWER number to keep the conductivity constant.

At lower frequencies than 2.4 GHz you should input a correspondingly HIGHER number, so that the conductivity stays at the correct constant value.

As I wrote in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316:

Quote
only for f=2.4 E+09 Hertz one has

ε“/εo = 3.252698 E+08

while for f = 2.45 E+09 Hertz (for example) one has

ε“/εo = 3.186316 E+08

Quote from: Rodal
The conductivity in SI Units that corresponds to epsilon"=0.00288 is:

conductivity        = omega * epsilon"
                          = 2 Pi frequency 0.00288
                          = 2 Pi 2.4E+9 * 0.00288
                          = 4.342937 E+7

which is almost 10 times smaller than 3.25E+8

Please also recall that DeltaMass was conscious that it is incorrect to take 0.00288 as a constant !

That value is a function of frequency.

What is approximately constant in this regime is the conductivity itself.

DeltaMass gave you explicit instructions to keep the conductivity constant, at other frequencies:
for example, the conductivity at 1 GHz is also  4.342937 E+7, so

at 1 GHz you should input into Meep  (3.25...E+8 ) *2.4 = 7.8 E+8, for example

So, for pure Silver, for example (from the table in the link in your post),

Conductivity =  6.090E+07


So, instead of 3.25...E+8 for copper, you have to use   ( 6.090E+07/4.342937 E+7 ) *3.25...E+8 at 2.4GHz

in other words, at 2.4 GHz, your input to Meep for pure Silver should be 1.402276 times higher than for the copper value given by DeltaMass.  About 40% higher, whether in SI units or in Meep units.

In other words, everything else being the same, the quality of resonance (Q) should be about 40% higher with pure silver than with copper.


OK, as an example, let's calculate some numbers:

1) Since the resonant frequency you calculated was 2.4959 GHz instead of 2.4 GHz, the input instead of 3.252698 E+08 should have been:

(2.4/2.4959)*3.252698 E+08 = 3.127719 E+08

Therefore, your MEEP run's output quality of resonance Q instead of Q=99,938, would have been, at 2.4959 GHz, for DeltaMass pure copper:

Q = (2.4/2.4959)*99,938
   = 96,098

__________________________________________

2) If instead of copper's conductivity, as proposed by DeltaMass, you would have used the value for conductivity for  Bronze, Commercial (Annealed) in (http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/): 2.552E+07, the Q output would have been:

Q = (2.4/2.4959)*99,938*(2.552E+07)/(4.342937 E+7)
   =56,469

and the input should have been:

(2.4/2.4959)*((2.552E+07)/(4.342937 E+7))*3.252698 E+08 = 1.837912 E+08
__________________________________________

3) If instead of copper's conductivity, as proposed by DeltaMass, you would have used the value for conductivity for Pure Silver in (http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/): 6.090E+07, the Q output would have been:

Q = (2.4/2.4959)*99,938*(6.090E+07)/(4.342937 E+7)
   =134,756

and the input should have been:

(2.4/2.4959)*((6.090E+07)/(4.342937 E+7))*3.252698 E+08 =

How thick would the silver plating (over copper) need to be, to model the frustum as pure silver? And how might a thin plating of gold, to protect the silver plating affect things?
« Last Edit: 12/11/2015 05:37 PM by OnlyMe »

Offline Rodal

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The MEEP input properties for the conductivity of copper ( MEEP:-2*pi*2.4GHz*3.252698E+8i) are very high, corresponding to a copper of practically 100% purity.

I think I got that number 3.252698E+8i from one of your own posts.  I have looked around the web for reference materials on more realistic real-world values but have not found a good one yet.  What units is that in?  It does not look like Siemens/meter, which is 58.6E6 for Cu.
The background of that number is in my previous posts, with luxury of details, including a discussion of units and a discussion of a conversion to usual units.

My posts (as any user posts) can be searched by clicking on my NSF membership, and clicking "Show Posts"

For example (one of many posts on this subject):
http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316

Basically it is based on a model proposed, for pure copper, by @DeltaMass.

It corresponds to a conductivity in SI units of  4.342937 E+7

As I have explained in previous messages:

1) For other material conductivities you simply have to ratio this input by the material conductivities

2) The input to MEEP should be changed for different frequencies.  The pure copper input is ONLY valid for 2.4 GHz.  At other frequencies the input should be linearly ratioed by the frequency ratio, so that the conductivity stays constant
At resonating frequencies higher than 2.4 GHz, you should input a correspondingly LOWER number to keep the conductivity constant.

At lower frequencies than 2.4 GHz you should input a correspondingly HIGHER number, so that the conductivity stays at the correct constant value.

As I wrote in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316:

Quote
only for f=2.4 E+09 Hertz one has

ε“/εo = 3.252698 E+08

while for f = 2.45 E+09 Hertz (for example) one has

ε“/εo = 3.186316 E+08

Quote from: Rodal
The conductivity in SI Units that corresponds to epsilon"=0.00288 is:

conductivity        = omega * epsilon"
                          = 2 Pi frequency 0.00288
                          = 2 Pi 2.4E+9 * 0.00288
                          = 4.342937 E+7

which is almost 10 times smaller than 3.25E+8

Please also recall that DeltaMass was conscious that it is incorrect to take 0.00288 as a constant !

That value is a function of frequency.

What is approximately constant in this regime is the conductivity itself.

DeltaMass gave you explicit instructions to keep the conductivity constant, at other frequencies:
for example, the conductivity at 1 GHz is also  4.342937 E+7, so

at 1 GHz you should input into Meep  (3.25...E+8 ) *2.4 = 7.8 E+8, for example

So, for pure Silver, for example (from the table in the link in your post),

Conductivity =  6.090E+07


So, instead of 3.25...E+8 for copper, you have to use   ( 6.090E+07/4.342937 E+7 ) *3.25...E+8 at 2.4GHz

in other words, at 2.4 GHz, your input to Meep for pure Silver should be 1.402276 times higher than for the copper value given by DeltaMass.  About 40% higher, whether in SI units or in Meep units.

In other words, everything else being the same, the quality of resonance (Q) should be about 40% higher with pure silver than with copper.


OK, as an example, let's calculate some numbers:

1) Since the resonant frequency you calculated was 2.4959 GHz instead of 2.4 GHz, the input instead of 3.252698 E+08 should have been:

(2.4/2.4959)*3.252698 E+08 = 3.127719 E+08

Therefore, your MEEP run's output quality of resonance Q instead of Q=99,938, would have been, at 2.4959 GHz, for DeltaMass pure copper:

Q = (2.4/2.4959)*99,938
   = 96,098

__________________________________________

2) If instead of copper's conductivity, as proposed by DeltaMass, you would have used the value for conductivity for  Bronze, Commercial (Annealed) in (http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/): 2.552E+07, the Q output would have been:

Q = (2.4/2.4959)*99,938*(2.552E+07)/(4.342937 E+7)
   =56,469

and the input should have been:

(2.4/2.4959)*((2.552E+07)/(4.342937 E+7))*3.252698 E+08 = 1.837912 E+08
__________________________________________

3) If instead of copper's conductivity, as proposed by DeltaMass, you would have used the value for conductivity for Pure Silver in (http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/): 6.090E+07, the Q output would have been:

Q = (2.4/2.4959)*99,938*(6.090E+07)/(4.342937 E+7)
   =134,756

and the input should have been:

(2.4/2.4959)*((6.090E+07)/(4.342937 E+7))*3.252698 E+08 =

How thick would the silver plating (over) need to be, to model the frustum as pure silver? And how might a thin playing of gold, to protect the silver plating affect things?

It would need to be thicker than the skin depth for Silver at 2.4959 GHz, which is:

1.291 micrometers = 50.82 microinches


______________

Pure gold, according to http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/,  has a conductivity of 4.060E+07, which is less than Silver's 6.090E+07 and less than DeltaMass assumed conductivity for pure copper 4.342937 E+7

(Pure Silver Eddy Current Technology Incorporated)/(Pure copper DeltaMass) = 1.402

(Pure Gold Eddy Current Technology Incorporated)/(Pure copper DeltaMass) = 0.935

______________

So, for highest quality of resonance Q, best thing is Pure Silver, by far.  Followed by Pure Copper and Pure Gold which are close to each other.

The advantage of Gold is that it does not corrode or stain, its disadvantage is ... price  :)

Gold is the least reactive of all metals and is benign in all natural and industrial environments. Gold never reacts with oxygen (one of the most active elements), which means it will not rust or tarnish
« Last Edit: 12/11/2015 05:49 PM by Rodal »

Offline SeeShells

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Ref long thread... http://forum.nasaspaceflight.com/index.php?topic=39004.msg1455988#msg1455988

From what I've read I'm around 40-50 um and may put another coat but I don't think it's needed as RF penetration is under 5um.

I think I'll keep silver for now.

1) it develops oxides quite slowly (takes sulfur around it)  and it also cleans very easy.

2) To lay down a electroplated uniform layer of gold that remains under 1um is very hard to do with a hand method and it will need to wait for a professional plating shop specializing in waveguides.

Shell

modded, Stupiddd speeeling korector
« Last Edit: 12/11/2015 05:52 PM by SeeShells »

Online ThereIWas3

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I will correct the computation of permittivity to use the actual signal frequency rather than the fixed 2.4 GHz it is now.  I am trying to eliminate "magic constants" in the code as much as possible, so everything automatically tracks the input model data.

Edit:  meep does not do well at simulating very thin layers, unless you set the lattice size really small, which increases computation time enormously.  So I would keep the current thickish material specification and set the permitivity somewhere between Cu and Ag.  The current thickness is greater than real life for the same reason.   We do not need to simulate the escape of fields outside for the current purposes.
« Last Edit: 12/11/2015 06:07 PM by ThereIWas3 »
"If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea" - Antoine de Saint-Exupéry

Offline SteveD

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Stupid question: how does a spacecraft propelled by an EMDrive (if it works) slow down?  The basic answer is by creating a force in the opposite direction.  What happens to the energy that the drive has been loading into the spaceship?  It can't simply be destroyed, it has to go somewhere.  Where?

Offline OnlyMe

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Ref long thread... http://forum.nasaspaceflight.com/index.php?topic=39004.msg1455988#msg1455988

From what I've read I'm around 40-50 um and may put another coat but I don't think it's needed as RF penetration is under 5um.

I think I'll keep silver for now.

1) it develops oxides quite slowly (takes sulfur around it)  and it also cleans very easy.

2) To lay down a electroplated uniform layer of gold that remains under 1um is very hard to do with a hand method and it will need to wait for a professional plating shop specializing in waveguides.

Shell

modded, Stupiddd speeeling korector

I don't think from the information above, that gold plating would be worthwhile, funtionally or cost wise, as far as a test design is concerned. It would be good to know if silver electroplating can be modeled as pure silver or if it needs to be adjusted in some way.

Offline OnlyMe

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Stupid question: how does a spacecraft propelled by an EMDrive (if it works) slow down?  The basic answer is by creating a force in the opposite direction.  What happens to the energy that the drive has been loading into the spaceship?  It can't simply be destroyed, it has to go somewhere.  Where?

Actually assuming that the EMDrive or another EMDrive on the same satellite is used for deceleration, wouldn't that amount to conservation of momentum, just over an extended time frame... Acceleration and deceleration both generated by a closed box thruster.

Aside from that, since unsing a constant thrust device of any kind would involve far different trajectories, some of the thrust would dissipated in overcoming gravitation.., but that leads back to the conservation of momentum issue
« Last Edit: 12/11/2015 06:20 PM by OnlyMe »

Offline Rodal

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Ref long thread... http://forum.nasaspaceflight.com/index.php?topic=39004.msg1455988#msg1455988

From what I've read I'm around 40-50 um and may put another coat but I don't think it's needed as RF penetration is under 5um.

I think I'll keep silver for now.

1) it develops oxides quite slowly (takes sulfur around it)  and it also cleans very easy.

2) To lay down a electroplated uniform layer of gold that remains under 1um is very hard to do with a hand method and it will need to wait for a professional plating shop specializing in waveguides.

Shell

modded, Stupiddd speeeling korector

I don't think from the information above, that gold plating would be worthwhile, funtionally or cost wise, as far as a test design is concerned. It would be good to know if silver electroplating can be modeled as pure silver or if it needs to be adjusted in some way.

That's correct, electroplating is detrimental to conductivity when compared to pure copper, to the point that rather than increasing the Q, electroplating silver may actually decrease Q drastically, by up to 50% according to this peer-reviewed article:

"It is often found that silver-plating a copper conductor increases the radio-frequency losses (reduces Q) instead of reducing them as expected"

(Radio-frequency) investigations have shown that the conductivity of much of the commercial silver-plating is about half of that of pure copper

So that silver-plating, rather than increasing the Q by 40%, according to this classic paper, apparently will reduce Q to half of the Q with pure copper

Radio Frequency Performance of Electro Plated Finishes

A.M. Fowler

Proceedings IREE Australia May 1970

http://k6mhe.com/n7ws/Plating.pdf

« Last Edit: 12/11/2015 06:52 PM by Rodal »

Offline X_RaY

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Stupid question: how does a spacecraft propelled by an EMDrive (if it works) slow down?  The basic answer is by creating a force in the opposite direction.  What happens to the energy that the drive has been loading into the spaceship?  It can't simply be destroyed, it has to go somewhere.  Where?
1. Yes turn the ship or the device by 180° what is generating the thrust to slow down.
2. The device have to generate thrust... Some work has to be done to slow the ship done, this will generate some heat/ thermal radiation. All of this will increase the entropy of the universe... such as in the acceleration case. There isn't a difference between the acceleration and the deceleration phase. Acceleration and the deceleration are equal in the light of Relativity.
https://en.wikipedia.org/wiki/Work_%28physics%29
https://en.wikipedia.org/wiki/Entropy
3. Conservation of energy is one of the fundamental statements of modern physics, energy don't will destroyed.
« Last Edit: 12/11/2015 06:38 PM by X_RaY »

Offline aero

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I will correct the computation of permittivity to use the actual signal frequency rather than the fixed 2.4 GHz it is now.  I am trying to eliminate "magic constants" in the code as much as possible, so everything automatically tracks the input model data.

Edit:  meep does not do well at simulating very thin layers, unless you set the lattice size really small, which increases computation time enormously.  So I would keep the current thickish material specification and set the permitivity somewhere between Cu and Ag.  The current thickness is greater than real life for the same reason.   We do not need to simulate the escape of fields outside for the current purposes.
Please make a backup copy of your model before you refine it so that we can be sure to reconcile our models. The Shells model you are using was much different than mine, but I have made a model of what I think you are running. If the attached looks like what you have, I will run it with your input data to verify our models. I don't recall whether or not it is similar to the model that Dr. Rodal worked with. Maybe he does.

Edit add: Oh, and I suggest that you change your coordinate system to use the z-coordinate  as the axis of rotation. I used x at the time the NSF-1701 model was uploaded but it did cause confusion among our physicists friends. That's why I changed it to the generally accepted convention that holds z as the direction of propagation of EM waves.
« Last Edit: 12/11/2015 06:51 PM by aero »
Retired, working interesting problems

Offline Rodal

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I will correct the computation of permittivity to use the actual signal frequency rather than the fixed 2.4 GHz it is now.  I am trying to eliminate "magic constants" in the code as much as possible, so everything automatically tracks the input model data.

Edit:  meep does not do well at simulating very thin layers, unless you set the lattice size really small, which increases computation time enormously.  So I would keep the current thickish material specification and set the permitivity somewhere between Cu and Ag.  The current thickness is greater than real life for the same reason.   We do not need to simulate the escape of fields outside for the current purposes.

I agree, it does not make any sense (from a numerical solution viewpoint) to attempt to simulate with Meep the thin layer, at the same time that one is simulating the cavity.  Incompatible meshing size, leading to numerical instability upon solution of the simultaneous equations.  To simulate the thin layers would need to write a new separate code to couple the solution in the layer to the solution in the cavity, in order to eliminate the numerical instability that would unsue otherwise from trying to solve it within Meep in a single mesh.
« Last Edit: 12/11/2015 08:08 PM by Rodal »

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