Author Topic: EM Drive Developments - related to space flight applications - Thread 5  (Read 778021 times)

Offline rfmwguy

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Don't let Doc make you nervous Aero...his IQ is the same as ours...about 235.  ::)

Offline Emmett Brown

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1. You have thrust but it is small for your test bench to measure. How did you make the aluminum frustum? I mean it is hard to solder aluminum... so how is it held together? One possibility is that your frustum has a very low Q and hence a very low thrust level...


You can see the seam of the cone in this pic.  It's pretty tight, but it hasn't been soldered yet.  (There's a few inches of overlap where those clips at the back are).  I've done some brazing on this (the maggie mount plate) already.  Yes, it's not the easiest, but if you can get it clamped properly, it's not too bad.

I was still debating on when to make it permanent - whether I was going to just run simulations, or bite the bullet and get the miniVNA to tune it.



Offline Rodal

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By 235, he probably thinks that I am heavy, very heavy, that I weigh 235 lbs  :)

~~~~~~~~~~~~~

Dr. Rodal,

I'm still missing something in the terminology.
I want to model SeeShells Quartz rod in her CE3 cavity but it is fruitless if I don't get it right.

I have from Shell, here http://www.technicalglass.com/technical_properties.html

that disapation factor < 1E-4, which equals tan delta, and the constant = 3.75 so I calculate the imaginary part of relative permittivity as 3.75E-4 . Now I get shakey. I think I have
epsilon = 3.25 +i3.25E-4 and now the terminology changes and I get more confused.

You wrote CONDUCTIVITY = omega * epsilon"

and the meep units wiki gives meep electrical conductivity = sigma_d = e_r *e_o * c/a . I know e_o, c and a, but if e_r is the real part = the constant, where is epsilon"?

It seems self evident to me that epsilon" must factor into sigma_d somehow.

Or is it so simple as sigma_d = transformation factor * epsilon"  and I misinterpreted above?

If you define the following values for the constitutive properties of fused quartz:

(real value of) relative electric permittivity = εr
                                                               = 3.75

tan δ (electric) = 0.0001

then, it follows that:

relative complex permittivity = εr*(1 - i* tan δe)
                                            = εr*(1 - i* 0.0001)

                                           
relative complex permittivity =  3.75(1 - i* 0.0001)
                                            = 3.75 - i * 0.0001*3.75
                                            = 3.75 - i * 0.000375
                                       


COMMENTS:

1) I don't understand why you wrote 3.25 instead of 3.75 in your expression (epsilon = 3.25 +i3.25E-4)

2) The sign of the imaginary part should be negative, because a negative imaginary part results in power loss.  A positive sign (as in your expression) would result in power production, which violates the 2nd law of thermodynamics (dielectric materials entail power loss, not power production). (As pointed out in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316)

3) I don't understand your discussion of electric conductivity in this context or the questions that follow.  Quartz is a dielectric material, not a metal conductor.  Please try to re-word your question on conductivity to explain the intended context or purpose (are you talking about the conductivity of copper ? )

First, 3.25 was a nervous slip. You make me nervous   :-[

Second, in the meep code,
(material (make medium (epsilon epsilon_r) (D-conductivity CU-D-conduct)))
the parameter : CU-D-conduct should be less than zero, that is, negative..

Third, I think that I was still confused, but the light dawned. Is this the correct expression?

sigma-d = epsilon" * e_r *e_o * c/a .
so that conductivity = Omega * sigma_d.

I'll code that up (using the negative sign), print it out and re-post here for validation.

No, it is not true that conductivity = Omega * sigma_d


Here it is step by step (I'm using a positive conductivity, you can add the negative sign):

We know that the conductivity in SI units is σ=ω ε

σ=ω ε
  =2 π f ε
  = 2 π f (ε/ε') ε'
  = 2 π f tan δe ε'
  = 2 π f tan δe (ε'/ εo) εo
  = 2 π f tan δe εr εo

Then (from http://ab-initio.mit.edu/wiki/index.php/Conductivity_in_Meep#Conductivity_and_complex_.CE.B5 ), the conversion between the (dimensionless) Meep conductivity σD and the conductivity σ (in SI units) is:

σD = (a/c) σ /( εr εo)
                     = 2 π f (a/c)  tan δe
                   
where

a= length scale (I think that aero chose a = 0.3 meters)
c = speed of light in vacuum (299792458 meters / second)
f = frequency (in Hertz = 1 / second)

where you can interpret

σD is the dimensionless Meep conductivity

f (a/c) is the dimensionless frequency (notice that a/c has units of time)

tan δe is the dimensionless expression corresponding to the dimensional imaginary permittivity ε
« Last Edit: 12/10/2015 03:17 AM by Rodal »

Offline rfmwguy

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1. You have thrust but it is small for your test bench to measure. How did you make the aluminum frustum? I mean it is hard to solder aluminum... so how is it held together? One possibility is that your frustum has a very low Q and hence a very low thrust level...


You can see the seam of the cone in this pic.  It's pretty tight, but it hasn't been soldered yet.  (There's a few inches of overlap where those clips at the back are).  I've done some brazing on this (the maggie mount plate) already.  Yes, it's not the easiest, but if you can get it clamped properly, it's not too bad.

I was still debating on when to make it permanent - whether I was going to just run simulations, or bite the bullet and get the miniVNA to tune it.


Nice build! Don't be afraid to move the mag around. Iulian had side insertion like others. With mesh, I used top and bottom insertion. No results until I centered it on large diameter. Solder on aluminum? Or solder paste/epoxy?

Offline SteveD

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Acoustic  ==> speed of sound
Electromagnetic ==> speed of light

Acoustic fundamental natural frequencies are millions of times less than the fundamental natural frequencies in electromagnetic cavities.  Wavelengths are correspondingly vastly different.  Mode shapes are different too



While all of this is true, if the thing looks like a horn, I'd think at least a cursory check of the acoustical literature might be in order to see if it points to mathematical function describing the shape that rfmwguy experimentally arrived at.  The questions, as I see it, are 1. why does the proposed optimal frustum shape look like this, 2. what formula produces the shape and 3. does that formula suggest further optimization.  At the very least, a search of acoustical literature might turn up some elegant math to describe the shape.
« Last Edit: 12/10/2015 04:02 AM by SteveD »

Offline zen-in

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I'm not going to take sides on this and I am not going to send an email to Chris.   Everyone should just settle down and get back on track before Chris gets so annoyed at the whole lot of us that he shuts down the thread for good.   Let's see some experimental results and focus on what we know and what we can do to get to the bottom of this em-drive phenomena.  Enough with the distractions.

Offline Emmett Brown

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Nice build! Don't be afraid to move the mag around. Iulian had side insertion like others. With mesh, I used top and bottom insertion. No results until I centered it on large diameter. Solder on aluminum? Or solder paste/epoxy?

Thanks!  Yes, I've planned to move it around like you suggested.   That's why the mounting plate went the full length of the sidewall and has some pre-drilled holes.  For brazing the aluminum, I used Bernzomatic AL3 rods.

http://www.bernzomatic.com/product/al3-aluminum-brazing-welding-rods/

Offline aero

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By 235, he probably thinks that I am heavy, very heavy, that I weigh 235 lbs  :)

~~~~~~~~~~~~~

Dr. Rodal,

I'm still missing something in the terminology.
I want to model SeeShells Quartz rod in her CE3 cavity but it is fruitless if I don't get it right.

I have from Shell, here http://www.technicalglass.com/technical_properties.html

that disapation factor < 1E-4, which equals tan delta, and the constant = 3.75 so I calculate the imaginary part of relative permittivity as 3.75E-4 . Now I get shakey. I think I have
epsilon = 3.25 +i3.25E-4 and now the terminology changes and I get more confused.

You wrote CONDUCTIVITY = omega * epsilon"

and the meep units wiki gives meep electrical conductivity = sigma_d = e_r *e_o * c/a . I know e_o, c and a, but if e_r is the real part = the constant, where is epsilon"?

It seems self evident to me that epsilon" must factor into sigma_d somehow.

Or is it so simple as sigma_d = transformation factor * epsilon"  and I misinterpreted above?

If you define the following values for the constitutive properties of fused quartz:

(real value of) relative electric permittivity = εr
                                                               = 3.75

tan δ (electric) = 0.0001

then, it follows that:

relative complex permittivity = εr*(1 - i* tan δe)
                                            = εr*(1 - i* 0.0001)

                                           
relative complex permittivity =  3.75(1 - i* 0.0001)
                                            = 3.75 - i * 0.0001*3.75
                                            = 3.75 - i * 0.000375
                                       


COMMENTS:

1) I don't understand why you wrote 3.25 instead of 3.75 in your expression (epsilon = 3.25 +i3.25E-4)

2) The sign of the imaginary part should be negative, because a negative imaginary part results in power loss.  A positive sign (as in your expression) would result in power production, which violates the 2nd law of thermodynamics (dielectric materials entail power loss, not power production). (As pointed out in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316)

3) I don't understand your discussion of electric conductivity in this context or the questions that follow.  Quartz is a dielectric material, not a metal conductor.  Please try to re-word your question on conductivity to explain the intended context or purpose (are you talking about the conductivity of copper ? )

First, 3.25 was a nervous slip. You make me nervous   :-[

Second, in the meep code,
(material (make medium (epsilon epsilon_r) (D-conductivity CU-D-conduct)))
the parameter : CU-D-conduct should be less than zero, that is, negative..

Third, I think that I was still confused, but the light dawned. Is this the correct expression?

sigma-d = epsilon" * e_r *e_o * c/a .
so that conductivity = Omega * sigma_d.

I'll code that up (using the negative sign), print it out and re-post here for validation.

No, it is not true that conductivity = Omega * sigma_d


Here it is step by step (I'm using a positive conductivity, you can add the negative sign):

We know that the conductivity in SI units is σ=ω ε“

σ=ω ε“
  =2 π f ε“
  = 2 π f (ε“/ε') ε'
  = 2 π f tan δe ε'
  = 2 π f tan δe (ε'/ εo) εo
  = 2 π f tan δe εr εo

Then (from , the conversion between the (dimensionless) Meep conductivity]http://ab-initio.mit.edu/wiki/index.php/Conductivity_in_Meep#Conductivity_and_complex_.CE.B5 ), the conversion between the (dimensionless) Meep conductivity σD and the conductivity σ (in SI units) is:

σD = (a/c) σ /( εr εo)
                     = 2 π f (a/c)  tan δe
                   
where

a= length scale (I think that aero chose a = 0.3 meters)
c = speed of light in vacuum (299792458 meters / second)
f = frequency (in Hertz = 1 / second)

where you can interpret

σD is the dimensionless Meep conductivity

f (a/c) is the dimensionless frequency (notice that a/c has units of time)

tan δe is the dimensionless expression corresponding to the dimensional imaginary permittivity ε“

I think I've got it now, but I'm having a hard time reconciling this reference:
http://meepunits.wikia.com/wiki/Meep_unit_transformation_Wiki
with this reference:
 http://ab-initio.mit.edu/wiki/index.php/Conductivity_in_Meep#Conductivity_and_complex_.CE.B5 ), the conversion between the (dimensionless) Meep conductivity
 They seem to be the inverse of one another.
I chose to follow your example and calculated sigma_d =  Q_D_conduct = -1.670715037160664e-12

I did read the previous reference on Fused Quartz more closely and noticed that the data was at 1 MHz, so found another reference which gave data at 100MHz and 3GHz. This reference gave
tan δe     0.0002 @ 100 MHz, 0.00006 @ 3 GHz so I've coded 0.00006 as the loss tangent at 3 GHz.
« Last Edit: 12/10/2015 05:06 AM by aero »
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Offline SteveD

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I guess that assumes an insignificant thrust from your current build? Since no one knows how thrust is developed.., if it is developed, you souldn't destructively tear a successful build apart, until.., maybe allowing it to be retested by another builder...

:-X
Your good at analytical thinking.... but that's not quite the case.  8)

Shell

Betting pool is now open.  Whoever gets the number closest to the reported amount gets a green star (gold stars have some morbid history).

I've got 0.38N and 0.04N.

Offline Rodal

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Acoustic  ==> speed of sound
Electromagnetic ==> speed of light

Acoustic fundamental natural frequencies are millions of times less than the fundamental natural frequencies in electromagnetic cavities.  Wavelengths are correspondingly vastly different.  Mode shapes are different too



While all of this is true, if the thing looks like a horn, I'd think at least a cursory check of the acoustical literature might be in order to see if it points to mathematical function describing the shape that rfmwguy experimentally arrived at.  The questions, as I see it, are 1. why does the proposed optimal frustum shape look like this, 2. what formula produces the shape and 3. does that formula suggest further optimization.  At the very least, a search of acoustical literature might turn up some elegant math to describe the shape.
1) "A cursory review" of what rfmwguy wrote reveals that  rfmwguy already knows what mathematical function describes the shape that rfmwguy proposed.  It is called the logarithmic function, or equivalently the mathematical inverse of the exponential function (depending on how you pose the variables).

2) There is no "elegant math" unique to the acoustical literature.  Acoustics uses the same mathematical tools as other branches of physics and engineering  The logarithmic function is the mathematical inverse of the exponential function, which is one of the most elementary mathematical functions because it has very nice properties for the solution of differential equations:

the derivative of the exponential function is ...  the exponential function
« Last Edit: 12/10/2015 12:37 PM by Rodal »

Offline Rodal

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By 235, he probably thinks that I am heavy, very heavy, that I weigh 235 lbs  :)

~~~~~~~~~~~~~

Dr. Rodal,

I'm still missing something in the terminology.
I want to model SeeShells Quartz rod in her CE3 cavity but it is fruitless if I don't get it right.

I have from Shell, here http://www.technicalglass.com/technical_properties.html

that disapation factor < 1E-4, which equals tan delta, and the constant = 3.75 so I calculate the imaginary part of relative permittivity as 3.75E-4 . Now I get shakey. I think I have
epsilon = 3.25 +i3.25E-4 and now the terminology changes and I get more confused.

You wrote CONDUCTIVITY = omega * epsilon"

and the meep units wiki gives meep electrical conductivity = sigma_d = e_r *e_o * c/a . I know e_o, c and a, but if e_r is the real part = the constant, where is epsilon"?

It seems self evident to me that epsilon" must factor into sigma_d somehow.

Or is it so simple as sigma_d = transformation factor * epsilon"  and I misinterpreted above?

If you define the following values for the constitutive properties of fused quartz:

(real value of) relative electric permittivity = εr
                                                               = 3.75

tan δ (electric) = 0.0001

then, it follows that:

relative complex permittivity = εr*(1 - i* tan δe)
                                            = εr*(1 - i* 0.0001)

                                           
relative complex permittivity =  3.75(1 - i* 0.0001)
                                            = 3.75 - i * 0.0001*3.75
                                            = 3.75 - i * 0.000375
                                       


COMMENTS:

1) I don't understand why you wrote 3.25 instead of 3.75 in your expression (epsilon = 3.25 +i3.25E-4)

2) The sign of the imaginary part should be negative, because a negative imaginary part results in power loss.  A positive sign (as in your expression) would result in power production, which violates the 2nd law of thermodynamics (dielectric materials entail power loss, not power production). (As pointed out in http://forum.nasaspaceflight.com/index.php?topic=38577.msg1453316#msg1453316)

3) I don't understand your discussion of electric conductivity in this context or the questions that follow.  Quartz is a dielectric material, not a metal conductor.  Please try to re-word your question on conductivity to explain the intended context or purpose (are you talking about the conductivity of copper ? )

First, 3.25 was a nervous slip. You make me nervous   :-[

Second, in the meep code,
(material (make medium (epsilon epsilon_r) (D-conductivity CU-D-conduct)))
the parameter : CU-D-conduct should be less than zero, that is, negative..

Third, I think that I was still confused, but the light dawned. Is this the correct expression?

sigma-d = epsilon" * e_r *e_o * c/a .
so that conductivity = Omega * sigma_d.

I'll code that up (using the negative sign), print it out and re-post here for validation.

No, it is not true that conductivity = Omega * sigma_d


Here it is step by step (I'm using a positive conductivity, you can add the negative sign):

We know that the conductivity in SI units is σ=ω ε

σ=ω ε
  =2 π f ε
  = 2 π f (ε/ε') ε'
  = 2 π f tan δe ε'
  = 2 π f tan δe (ε'/ εo) εo
  = 2 π f tan δe εr εo

Then (from , the conversion between the (dimensionless) Meep conductivity]http://ab-initio.mit.edu/wiki/index.php/Conductivity_in_Meep#Conductivity_and_complex_.CE.B5 ), the conversion between the (dimensionless) Meep conductivity σD and the conductivity σ (in SI units) is:

σD = (a/c) σ /( εr εo)
                     = 2 π f (a/c)  tan δe
                   
where

a= length scale (I think that aero chose a = 0.3 meters)
c = speed of light in vacuum (299792458 meters / second)
f = frequency (in Hertz = 1 / second)

where you can interpret

σD is the dimensionless Meep conductivity

f (a/c) is the dimensionless frequency (notice that a/c has units of time)

tan δe is the dimensionless expression corresponding to the dimensional imaginary permittivity ε

I think I've got it now, but I'm having a hard time reconciling this reference:
http://meepunits.wikia.com/wiki/Meep_unit_transformation_Wiki
with this reference:
 http://ab-initio.mit.edu/wiki/index.php/Conductivity_in_Meep#Conductivity_and_complex_.CE.B5 ), the conversion between the (dimensionless) Meep conductivity
 They seem to be the inverse of one another.
I chose to follow your example and calculated sigma_d =  Q_D_conduct = -1.670715037160664e-12

I did read the previous reference on Fused Quartz more closely and noticed that the data was at 1 MHz, so found another reference which gave data at 100MHz and 3GHz. This reference gave
tan δe     0.0002 @ 100 MHz, 0.00006 @ 3 GHz so I've coded 0.00006 as the loss tangent at 3 GHz.

1) the two references for conversion of Meep conductivity pointed above agree with each other, if one overlooks the subscript "D" (the meaning of the subscript is different in the two references).  Rather than looking at the subscript, start from the concept that the Meep conductivity is dimensionless, which shows which interpretation is correct.  The Meep conductivity is dimensionless and the usual conductivity (as in textbooks) is dimensional.

2) you don't point out the reference you found for fused quartz data so it is impossible to comment on its veracity, but on principle I don't agree with choosing properties based on which Internet reference you find based solely on frequency (unless your reference is from a peer-reviewed reference showing the actual measurement vs frequency).

There are different qualities of materials, dependent not only on their material make up but also on their manufacturing method.  Shell may have selected her source for properties based on the supplier of her quartz.  It would be a mistake to ignore that if the data is from her supplier.

 RF Cafe data is notoriously unreliable (as previously discussed in these threads).  Microwaves 101 (http://www.microwaves101.com/encyclopedias/quartz) has data that is pretty close to the one given by Shell. 
« Last Edit: 12/10/2015 02:23 PM by Rodal »

Offline glennfish

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A draft data store is available for critique, review, testing.

http://www.rfdriven.com

Currently, there's no content, just a draft structure.  The database has two views:
1.  A web directory view (so archive.org can grab the content) which is read only
2.  A user DB view (where folks can add content or search for content

Nothing is frozen so now would be a good time to suggest changes, variations, etc.

Ultimately I'll migrate the user DB view to something a bit more robust, but for archive.org, we have to use a directory structure of some kind, else it won't be found.

If anyone wants to start adding content, PM me, and I'll set up an account for you.  Please be specific where you want write permissions.  Write includes delete so don't ask for everything.   :)  Ultimately delete will mean "archive" but not today.

The default DB view login is Guest and the password is Guest
Looking good Glenn, let me know via PM when you're ready to get my data, I'll try and input it. Or, if you prefer, ask me the questions and I'll give you everything I know...which varies from day to day...64K of memory should do the trick. ;)

Well, I'm not sure if this is an idea that people are going to support.

I've got exactly one contributor request, although 26 folks have taken a look, without comment.

Interesting spread of interest (map below).

Thoughts?

Offline rfmwguy

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A draft data store is available for critique, review, testing.

http://www.rfdriven.com

Currently, there's no content, just a draft structure.  The database has two views:
1.  A web directory view (so archive.org can grab the content) which is read only
2.  A user DB view (where folks can add content or search for content

Nothing is frozen so now would be a good time to suggest changes, variations, etc.

Ultimately I'll migrate the user DB view to something a bit more robust, but for archive.org, we have to use a directory structure of some kind, else it won't be found.

If anyone wants to start adding content, PM me, and I'll set up an account for you.  Please be specific where you want write permissions.  Write includes delete so don't ask for everything.   :)  Ultimately delete will mean "archive" but not today.

The default DB view login is Guest and the password is Guest
Looking good Glenn, let me know via PM when you're ready to get my data, I'll try and input it. Or, if you prefer, ask me the questions and I'll give you everything I know...which varies from day to day...64K of memory should do the trick. ;)

Well, I'm not sure if this is an idea that people are going to support.

I've got exactly one contributor request, although 26 folks have taken a look, without comment.

Interesting spread of interest (map below).

Thoughts?

I support it, no time this week to start uploading.

Offline Rodal

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I'm not going to take sides on this and I am not going to send an email to Chris.   Everyone should just settle down and get back on track before Chris gets so annoyed at the whole lot of us that he shuts down the thread for good.   Let's see some experimental results and focus on what we know and what we can do to get to the bottom of this em-drive phenomena.  Enough with the distractions.

I have been on this EM Drive thread since thread number one.  Some people presently contributing to these threads were not present at that time and may be unfamiliar with its history, and how these threads are such a headache for the NSF moderators and for NSF administration.

Thread number had to be closed, completely shut down by NSF administration for several days because of exchanges that also resulted in banning of individuals.  At that time it was unknown whether the EM Drive would continue to exist.

This kind of stuff happens on the EM Drive thread much more often than in the conventional threads about NASA and Space X.

Multiple people have been banned and are sorely missed.

If the audience wants these threads to continue it is a question of self moderation and not arguing with moderators on their established guidelines, in order to make the moderator and NSF administration's job easier - or at least more similar to their regular monitoring of other threads-.
« Last Edit: 12/10/2015 12:26 PM by Rodal »

Offline rfmwguy

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Nice build! Don't be afraid to move the mag around. Iulian had side insertion like others. With mesh, I used top and bottom insertion. No results until I centered it on large diameter. Solder on aluminum? Or solder paste/epoxy?

Thanks!  Yes, I've planned to move it around like you suggested.   That's why the mounting plate went the full length of the sidewall and has some pre-drilled holes.  For brazing the aluminum, I used Bernzomatic AL3 rods.

http://www.bernzomatic.com/product/al3-aluminum-brazing-welding-rods/
Whoa...nice thoughts...looks like we have the real deal here! Btw, the vna is a painful $$$ but well worth it imho.

Offline rfmwguy

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From horn antenna on wikipedia:

"The horn shape that gives minimum reflected power is an exponential taper. Exponential horns are used in special applications that require minimum signal loss, such as satellite antennas and radio telescopes. However conical and pyramidal horns are most widely used, because they have straight sides and are easier to design and fabricate."

While they call it exponential, I've always heard logrithmic. So, I'm all stoked up about the baritone  when it arrives. Note: my wife is already wondering about me, the arrival of the baritone will convince her to summon the white coats  ;)

https://en.m.wikipedia.org/wiki/Horn_antenna

Offline SeeShells

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1. You have thrust but it is small for your test bench to measure. How did you make the aluminum frustum? I mean it is hard to solder aluminum... so how is it held together? One possibility is that your frustum has a very low Q and hence a very low thrust level...


You can see the seam of the cone in this pic.  It's pretty tight, but it hasn't been soldered yet.  (There's a few inches of overlap where those clips at the back are).  I've done some brazing on this (the maggie mount plate) already.  Yes, it's not the easiest, but if you can get it clamped properly, it's not too bad.

I was still debating on when to make it permanent - whether I was going to just run simulations, or bite the bullet and get the miniVNA to tune it.



Don't know where your budget is but two options on the VNA.
http://www.ebay.com/itm/138M-4-4G-SMA-signal-source-generator-simple-spectrum-analyzer-Tracking-source-/111493176997?hash=item19f582dea5
I have this one, ~$70-100 bucks, the software I have is buggy (I think it was corrupted) and I had a very hard time getting them to responding to my emails for new software. The reports are basically favorable, but mention the software issue and make sure you get it  with your order.

The second one is around $600 miniVNA tiny http://miniradiosolutions.com/54-2/
Software is clean and the device works well. rfmwguy, TheTraveler and I have bought this model.

Shell

PS: Nice work and a thought on coupling the parts together.

Offline VrilMachine

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I'm not going to take sides on this and I am not going to send an email to Chris.   Everyone should just settle down and get back on track before Chris gets so annoyed at the whole lot of us that he shuts down the thread for good.   Let's see some experimental results and focus on what we know and what we can do to get to the bottom of this em-drive phenomena.  Enough with the distractions.

I have been on this EM Drive thread since thread number one.  Some people presently contributing to these threads were not present at that time and may be unfamiliar with its history, and how these threads are such a headache for the NSF moderators and for NSF administration.

Thread number had to be closed, completely shut down by NSF administration for several days because of exchanges that also resulted in banning of individuals.  At that time it was unknown whether the EM Drive would continue to exist.

This kind of stuff happens on the EM Drive thread much more often than in the conventional threads about NASA and Space X.

Multiple people have been banned and are sorely missed.

If the audience wants these threads to continue it is a question of self moderation and not arguing with moderators on their established guidelines, in order to make the moderator and NSF administration's job easier - or at least more similar to their regular monitoring of other threads-.


As a layperson following these threads I cannot stress enough the need for civility. I hope these threads are preserved and studied in the years to come because people like me dont get to see science as it happens. These threads have done more to inspire me and my children than any of you can imagine. I am in my 40s contemplating going back to school and getting a mechanical engineering degree because I am so inspired by what some of you wrote.
 I absolutely love the nature of the correspondence between most of you and have made a few of you heroes to my children. One of my daughters said she wants to be an inventor like SeeShells when she grows up.


 So much science happens behind doors and being able to experience something like this feels very special to me. Please mods do not lock and ban.




"There is hopeful symbolism in the fact that flags do not wave in a vacuum." -Clarke
« Last Edit: 12/10/2015 12:57 PM by VrilMachine »

Online Chris Bergin

I'm not going to take sides on this and I am not going to send an email to Chris.   Everyone should just settle down and get back on track before Chris gets so annoyed at the whole lot of us that he shuts down the thread for good.   Let's see some experimental results and focus on what we know and what we can do to get to the bottom of this em-drive phenomena.  Enough with the distractions.

Too late. ;)

I've had a look. I see what the mods have to deal with and there have been *a lot* of complaints about that member's posts, more than anyone else on this thread (despite several attempts to advise that member) - to the point his own decision to leave resulted in many of the main players in this thread returning from lurking to posting - after they said they wouldn't post here again while he was here).

I'll get him back later, but with a final reminder on forum rules.

It's worth noting 19 people (as in active members with posts etc, not Chinese shoe discount spammers) have been banned in the history of NSF (10+ years. NINETEEN. I doubt there's any forum in the world this size with that few bans. However, nine are from the EM Drive threads, which is crazy considering EM Drive isn't even a "real" NSF subject thread (like Shuttle, SLS, SpaceX, ULA, etc).

A good solution for a satellite topic like this is to NSF (where most aren't part of the overall NSF community, but are a bunch of people in a shed in the garden, or an outdoor hot tub  - sadly....as in it's a leftfield topic outside of the main NSF domain!) is to have an objective/non-controversial EM Drive regular moderate these threads, as opposed to the mods more used to the more naturally civil and on topic areas (everywhere else on the forum). Self moderation should be a given, not a request.

I'll pop back into this thread over the coming days and see who looks like a good candidate for that.

---

Now please return to discussing the subject matter.

Offline Rodal

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From horn antenna on wikipedia:

"The horn shape that gives minimum reflected power is an exponential taper. Exponential horns are used in special applications that require minimum signal loss, such as satellite antennas and radio telescopes. However conical and pyramidal horns are most widely used, because they have straight sides and are easier to design and fabricate."

While they call it exponential, I've always heard logrithmic. So, I'm all stoked up about the baritone  when it arrives. Note: my wife is already wondering about me, the arrival of the baritone will convince her to summon the white coats  ;)

https://en.m.wikipedia.org/wiki/Horn_antenna

It depends on what variables you chose to define the problem.  Suppose that you have only two variables, x and y, related by:

x = y^2

this square function formula (which is well-behaved: there is only one value of x for a given value of y) can also be written in terms of its mathematical inverse:

y = Sqrt[ x]

but the formulation in terms of the inverse, the square root, introduces a number of complexities (there are two possible values of y for a given value of x, and for negative values of x, y becomes imaginary).  It is better to solve the problem in terms of x = y^2. 

Similarly the problem can be posed in terms of the exponential or its inverse, the logarithmic function.  The preferred formulation is in terms of the exponential which has nicer properties, including the beautiful fact that the derivative of the exponential function is the same function: the exponential.  Ditto for its integral.
« Last Edit: 12/10/2015 01:04 PM by Rodal »

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