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...
Quote from: Rodal on 12/09/2015 11:22 pmQuote from: aero on 12/09/2015 09:22 pmDr. 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.htmlthat 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 haveepsilon = 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 = 3.75tan δ (electric) = 0.0001then, 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.
Quote from: aero on 12/09/2015 09:22 pmDr. 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.htmlthat 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 haveepsilon = 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 = 3.75tan δ (electric) = 0.0001then, 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 ? )
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.htmlthat 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 haveepsilon = 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?
Quote from: RFPlumber on 12/09/2015 06:48 pm1. 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.
Acoustic ==> speed of soundElectromagnetic ==> speed of lightAcoustic 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
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?
By 235, he probably thinks that I am heavy, very heavy, that I weigh 235 lbs ~~~~~~~~~~~~~Quote from: aero on 12/10/2015 12:10 amQuote from: Rodal on 12/09/2015 11:22 pmQuote from: aero on 12/09/2015 09:22 pmDr. 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.htmlthat 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 haveepsilon = 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 = 3.75tan δ (electric) = 0.0001then, 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_dHere 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 εoThen (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 conductivityf (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“
Quote from: OnlyMe on 12/09/2015 03:16 pmI 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... Your good at analytical thinking.... but that's not quite the case. Shell
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...
Quote from: Rodal on 12/08/2015 08:18 pmAcoustic ==> speed of soundElectromagnetic ==> speed of lightAcoustic 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 tooWhile 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.
Quote from: Rodal on 12/10/2015 01:32 amBy 235, he probably thinks that I am heavy, very heavy, that I weigh 235 lbs ~~~~~~~~~~~~~Quote from: aero on 12/10/2015 12:10 amQuote from: Rodal on 12/09/2015 11:22 pmQuote from: aero on 12/09/2015 09:22 pmDr. 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.htmlthat 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 haveepsilon = 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 = 3.75tan δ (electric) = 0.0001then, 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_dHere 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 εoThen (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 conductivityf (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_Wikiwith 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-12I 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.
Quote from: glennfish on 12/09/2015 10:36 amA draft data store is available for critique, review, testing.http://www.rfdriven.comCurrently, 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 only2. A user DB view (where folks can add content or search for contentNothing 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 GuestLooking 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.
A draft data store is available for critique, review, testing.http://www.rfdriven.comCurrently, 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 only2. A user DB view (where folks can add content or search for contentNothing 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
Quote from: rfmwguy on 12/09/2015 12:17 pmQuote from: glennfish on 12/09/2015 10:36 amA draft data store is available for critique, review, testing.http://www.rfdriven.comCurrently, 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 only2. A user DB view (where folks can add content or search for contentNothing 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 GuestLooking 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'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.
Quote from: rfmwguy on 12/10/2015 02:00 amNice 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/
Quote from: zen-in on 12/10/2015 04:12 amI'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-.
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