Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2170639 times)

Offline rfmwguy

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For experimenters who might be considering a horn shaped frustum (easier to build for proof of concept), SETI has some interesting low-cost construction pics...note the RF feed pic from bottom on right:

http://www.setileague.org/photos/wghorn.htm

Offline SeeShells

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Please doc this is just a simple question, but why would absolute dimensional numbers be so important as long as you're in the ballpark for resonance? I think every device I've seen has taken into account that either you mechanically tune the EM cavity or shift the insertion frequency to optimize the thrust.
I've even thought of using a airtight Conductive Elastic Fabric on the endplate and varying the air pressure the chamber to optimize the reflected EM wave.


Since I am skeptical of the derivation of TheTraveller's Shawye's resonance calculation (I am from Missouri: show me  :) ) the only way I have to verify it is by comparing the mode shapes to the exact solution (which would also be useful in its own right, as per NASA and Notsosureofit).   Since many mode shapes are bunched together at close frequencies, one cannot determine whether a natural frequency prediction is correct unless one assesses the mode shape prediction.
I know I've been reviewing the mode work done by by Frank Davies of NASA and relating it to thrust and I'm observing some interesting correlations between the two. And it's not so much the Q.  :-X
Data, more data! 
For instance did you sweep the frequency from ~900mhz to ~3Ghz or just dial in a close TM frequency and then fine tune? If you did sweep do you have any data you could share?

Offline TheTraveller

@TheTraveller: Excuse my obtuseness, but don't you have the design freedom to arrange for Df to be as close to unity as you like? If there's one thing that Shawyer's work teaches, it's that maximising Df maximises thrust - therefore this seems to be worthwhile.

So what constraints forbid you designing for near-unity Df?

Dr Rodal did this excellent bit of work, which shows near unity Dfs are possible.

Might help to explain why the Flight Thruster was designed to run at 3.85GHz. To my knowledge Shawyer has never quoted the Df of the Flight Thruster.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline Rodal

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For instance did you sweep the frequency from ~900mhz to ~3Ghz or just dial in a close TM frequency and then fine tune? If you did sweep do you have any data you could share?
Both Frank Davis at NASA (using Finite Element Analysis) and I (using my exact solution) have only performed an eigenvalue analysis problem, from where we obtain the natural frequencies and mode shapes.

The reported results of Frank Davis for the frequencies and mode shapes are within ~1% of my exact solution.  I think that Frank Davis is an excellent Finite Element analyst, as he got the finite element mesh just right.
The only think I had some questions with is that NASA decided to interpret the mode shapes of the truncated cone using the same numbering system as a perfect cylinder, and this only works for mode shapes that are analogous.  Earlier in the thread I have discussions with Paul March where I pointed out mode shapes in the truncated cone that are not analogous to a cylinder's mode shape.  This usually happens when a mode shape is close to being cut-off and there is a lot of attenuation.  Curiously, this is the condition that Shawyer is shooting for, hence I am skeptical of what TheTraveller is calculating based on simple wavelengths.

I have not performed (and Paul March has not reported such data either) a spectrum response analysis yet.

In a real cavity experiment it is very unlikely that one is going to excite a single mode shape.
Actually, as Notsosureofit has repeatedly pointed out, one may be better off having two equidistant close frequencies locked up at the half power points if one is pursuing the highest Q (which again it is not known whether that's what one really wants).

To answer these questions (and more) one has to perform a spectrum analysis (NASA can do that with COMSOL, I would have to use ANSYS or ADINA or write my own program with Mathematica).

« Last Edit: 05/21/2015 05:47 PM by Rodal »

Offline deltaMass

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Quote from: TheTraveller
Dr Rodal did this excellent bit of work, which shows near unity Dfs are possible.
I know that - and also I did the same derivations myself (upon which you commented). But that doesn't directly answer my question. You published some specs that showed you are designing to a small Df. Why?
« Last Edit: 05/21/2015 05:43 PM by deltaMass »

Offline saucyjack

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We haven't heard TheTraveller's opinion.

Should we change the Experimental Spreadsheet assuming that Shawyer made a typo and the DesignFactor for the Demonstrator was 0.484 instead of 0.844 ?

Well, I was guessing he'd say yes, so I changed it already on http://emdrive.echothis.com/Experimental_Results.  Will of course switch it back if consensus says otherwise.

Offline Rodal

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...Reading it I had a question (more than one but..). And this is for everyone, why did Eagle Works observe no thrust in a EM device with no HDPE insert? Makes me wonder what effect achiral materials like this that can induce chirality would have with relativity and electromagnetic fields in your equations?

Thanks nice work!

Thanks a lot. The reason why a material can change the behaviour is magnetic permeability. This can enhance the effect by several magnitude orders. They use low input power, if I am right, and so this could be a good way around to such a limitation.

High Density PolyEthylene (HDPE) is a nonconductive polymer with no special magnetic properties, its relative magnetic permeability is very nearly unity, as is generally true of polymers. 

Hence we cannot explain the report that NASA observed thrust with a HDPE insert and observed no thrust in a EM device without the HDPE insert based on the relative magnetic permeability of HDPE (which is practically 1).

I think to explain this fact, and still be compatible with Marco's interesting paper, we must use the expression from Maxwell's theory for the speed of light:

1 / c2  =  μo εo = (magnetic permeabiltity) * (electric permittivity)

We can use this expression to convert magnetic permeability as follows:

o)2 = 1 / ( c4  (εo )2)

if we substitute this expression in the expression for the energy density parameter we obtain:

(Uo)4 / (μo)2  = (Uo)4  c4  (εo) 2

and therefore we can eliminate the factor of  c4 in Eq. 60 and get a more beautiful equation (with one less parameter) that depends explicitly on the electric permittivity as the following quantity gets transformed:

(Pi2 G / c4 ) ( (Uo)4  /(μo)2)  = Pi2 G  (Uo)4  (εo)2

In relativity, magnetic and electric fields are essentially different aspects of a unique electromagnetic field.  In the resonant cavity, when the magnetic field is maximum, the electric field is zero and vice-versa. The energy from the magnetic field goes into the electric field, back and forth.
« Last Edit: 05/21/2015 06:39 PM by Rodal »

Offline StrongGR

...Reading it I had a question (more than one but..). And this is for everyone, why did Eagle Works observe no thrust in a EM device with no HDPE insert? Makes me wonder what effect achiral materials like this that can induce chirality would have with relativity and electromagnetic fields in your equations?

Thanks nice work!

Thanks a lot. The reason why a material can change the behaviour is magnetic permeability. This can enhance the effect by several magnitude orders. They use low input power, if I am right, and so this could be a good way around to such a limitation.

High Density PolyEthylene (HDPE) is a nonconductive polymer with no special magnetic properties, its relative magnetic permeability is very nearly unity, as is generally true of polymers. 

Hence we cannot explain the report that NASA observed thrust with a HDPE insert and observed no thrust in a EM device without the HDPE insert based on the relative magnetic permeability of HDPE (which is practically 1).

I think to explain this fact, and still be compatible with Marco's interesting paper, we must use the expression from Maxwell's theory for the speed of light:

1 / c2  =  μo εo = (magnetic permeabiltity) * (electric permittivity)

We can use this expression to convert magnetic permeability as follows:

o)2 = 1 / ( c4  (εo )2)

if we substitute this expression in the expression for the energy density parameter we obtain:

(Uo)4 / (μo)2  = (Uo)4  c4  εo 2

and therefore we can eliminate the factor of  c4 in Eq. 60 and get a more beautiful equation (with one less parameter) that depends explicitly on the electric permittivity as the following quantity gets transformed:

(Pi2 G / (  c4  ) )  Uo)4  / c4  =
(Pi2 G  Uo)4  (εo)2

That's fine and depends on the kind of material used as a dielectric. I was considering teflon with mu about 10^-6 but you were using HDPE and things can be quite different.

I am evaluating the thrust equation from general relativity and I can see that Q of cavity, the power P and choice of the mode, k, can alleviate the smallness of the factor G/c^4 as also the choice of a good dielectric. These enter with square. On the other side, this formula applies well for r2>>r1 and r1 even more smaller. Also h, the height of the frustum, appears to be relevant in this evaluation.

Offline TheTraveller

Quote from: TheTraveller
Dr Rodal did this excellent bit of work, which shows near unity Dfs are possible.
I know that - and also I did the same derivations myself (upon which you commented). But that doesn't directly answer my question. You published some specs that showed you are designing to a small Df. Why?

My goal is to NOT reinvent the wheel 1st go and to build a Flight Thruster as close to the one Shawyer built. While Df is important, more so is Q, operating at resonance and impedance matching.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

We haven't heard TheTraveller's opinion.

Should we change the Experimental Spreadsheet assuming that Shawyer made a typo and the DesignFactor for the Demonstrator was 0.484 instead of 0.844 ?

Well, I was guessing he'd say yes, so I changed it already on http://emdrive.echothis.com/Experimental_Results.  Will of course switch it back if consensus says otherwise.

Could you also put also a (1) next to 0.484 and indicate in the note that Shawyer's reference has 0.844 but that this number gives a small diameter in conflict with the picture of the Demonstrator, therefore it is assumed there was typo transposition of the numbers ?

Would agree 0.844 seems a bit high for the Demonstrator. Will check it out.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline Reactionless

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Iulian is indeed alive and still (one assumes) possesses his eyeballs!

http://www.masinaelectrica.com/emdrive-independent-test/

Offline Rodal

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That's fine and depends on the kind of material used as a dielectric. I was considering teflon with mu about 10^-6 but you were using HDPE and things can be quite different...

Some information from NASA on their experiments with the truncated cone with the HDPE insert:

NASA Eagleworks has used a High Density Polyethylene dielectric insert for most of their experiments.  It was obtained from McMaster Carr.  It came from a supplier of extruded HDPE rods.

http://www.mcmaster.com/#standard-plastic-rods/=w0bzy0

under Rigid HDPE Polyethylene, apparently they no longer supply the 6.25" dimension.  Biggest diameter they list is 6.00 inches:  Rigid HDPE Polyethylene Rod, 6" Diameter

This site http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm reports

HDPE to have a relative electric permittivity εr = 2.26 @ 3 GHz

Notice from this picture that the HDPE dielectric insert is located towards the apex of the cone, which is the location (r~r1) where the effect, discussed in Marco' paper, is strongest:




Bigger image (click here to download):
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=634621
............................................

« Last Edit: 05/21/2015 06:57 PM by Rodal »

Offline Rodal

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Iulian is indeed alive and still (one assumes) possesses his eyeballs!

http://www.masinaelectrica.com/emdrive-independent-test/

Iulian reports:

"I flipped the cone in the original setup and i have the thrust downwards (scale goes positive). Unfortunately the thrust downwards is around 7 times smaller. difference on the scale is only 0.20 grams and is consistent with the power on and off . I will post the video on YouTube."

So, it appears that the true thrust should be

(Iulian convention:  positive reading going DOWN and a negative reading going UP)

TRUE EM DRIVE THRUST = (MeasurementDOWN - MeasurementUP) /2

which should subtract the lifting force due to the heated air (assuming that the lifting force is the same when pointed small diameter facing down and when the small diameter faces up)

For MeasurementDOWN = - MeasurementUP / 7; we get

TRUE EM DRIVE THRUST = MeasurementUP ( (1/7) + 1) /2 = 0.57 * MeasurementUP

It is interesting that the thrust of the EM Drive downward appears to be (a little)  greater than the lifting force of the heated air

« Last Edit: 05/21/2015 07:21 PM by Rodal »

Offline deltaMass

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We can figure out the true thrust now (T=thrust, a=air effect, in gm-wt)
T + a = -0.54
-T + a = +0.54/7
solving by eliminating a gives
T = -0.31 gm-wt

so thrusting forward at the small end

a = -0.23 (upwards)
« Last Edit: 05/21/2015 07:05 PM by deltaMass »

Offline SeeShells

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...Reading it I had a question (more than one but..). And this is for everyone, why did Eagle Works observe no thrust in a EM device with no HDPE insert? Makes me wonder what effect achiral materials like this that can induce chirality would have with relativity and electromagnetic fields in your equations?

Thanks nice work!

Thanks a lot. The reason why a material can change the behaviour is magnetic permeability. This can enhance the effect by several magnitude orders. They use low input power, if I am right, and so this could be a good way around to such a limitation.

High Density PolyEthylene (HDPE) is a nonconductive polymer with no special magnetic properties, its relative magnetic permeability is very nearly unity, as is generally true of polymers. 

Hence we cannot explain the report that NASA observed thrust with a HDPE insert and observed no thrust in a EM device without the HDPE insert based on the relative magnetic permeability of HDPE (which is practically 1).

I think to explain this fact, and still be compatible with Marco's interesting paper, we must use the expression from Maxwell's theory for the speed of light:

1 / c2  =  μo εo = (magnetic permeabiltity) * (electric permittivity)

We can use this expression to convert magnetic permeability as follows:

o)2 = 1 / ( c4  (εo )2)

if we substitute this expression in the expression for the energy density parameter we obtain:

(Uo)4 / (μo)2  = (Uo)4  c4  εo 2

and therefore we can eliminate the factor of  c4 in Eq. 60 and get a more beautiful equation (with one less parameter) that depends explicitly on the electric permittivity as the following quantity gets transformed:

(Pi2 G / (  c4  ) )  Uo)4  / c4  =
(Pi2 G  Uo)4  (εo)2

That's fine and depends on the kind of material used as a dielectric. I was considering teflon with mu about 10^-6 but you were using HDPE and things can be quite different.

(1) Magnetic susceptibilities of paramagnetic and diamagnetic materials... see anything interesting?
http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_6.html

Offline Lobo

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So I'm a newbie to this thread, and don't really understand the concept very well.  As I'll never have time to read through the previous 200+ pages (I've read through some of the more recent ones) I just had a couple of simple questions that could maybe catch me up a bit.  If Someone doesn't mind answering them although I'm sure they've been addressed at various points in this thread in the last 200 pages.

1)  I've read some articles online on this, including the recent article here.  I think I understand the general idea behind it.  There's a lot of skeptism about it about how it violates the laws of physics.  On the other side apparently the radiation is producing the force, so it's actually not a reactionless drive?
So are we at a point where the indications are a majority that it can work?...and be practically flown in the not too distant future?  After the recent Eagleworks testing?

2)  What would be the impulse of the thrust of such a drive?  I think Ion thrusters can get up to 5000s?  How would this compare?  Chris's article mentioned some very fast transit times, but no mention of what the actual impulse number is.

3)  Is it possible to generate enough power on a realistic spacecraft to power it so that it could actually take crews or robots to other planets in the solar system?  One criticism is that even if this worked, it would take so much power that it wouldn't be feasible.  But Chris's article didn't seem to indicated that the power requirements were unfeasible.   And that the thrust to power input ratio went down as power went up?  What's the view on that on the thread?

Anyway, pardon my simplistic questions.  Just kinda trying to get a summary of where this thread has covered in the past 200 pages, and if this is actually something we might see fly sometime?  Or is it highly theoretical like a "warp" drive? (which the Eagleworks had been working on)

Offline Reactionless

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We can figure out the true thrust now (T=thrust, a=air effect, in gm-wt)
T + a = -0.54
-T + a = +0.54/7
solving by eliminating a gives
T = -0.31 gm-wt

so thrusting forward at the small end

Quote
the thrust downwards is around 7 times smaller. difference on the scale is only 0.20 grams

I'm confused.

From Iulian's quote, wouldn't Test 1 = 0.2*7=1.4g and Test 2 = 0.2 . Then the equation would be set up like this?

T=thrust
A=air

T+A=1.4g
T-A=0.2g
T=0.8g
A=0.6g

Offline Iulian Berca

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Hi,

When i saw the people start thinking i died i was concerned. I wanted to post when i have some results but now i`m forced me to post some unfinished work :)

I just closed the cone with new setup in place and in the next days i will be busy adjusting the distance and see if i have any improvement. The work will be slow because i need to make a lot of tests with different distance for each test i need to let the magnetron to cool down for at least 5 minutes.

Iulian

Offline tchernik

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Hi,

When i saw the people start thinking i died i was concerned. I wanted to post when i have some results but now i`m forced me to post some unfinished work :)

I just closed the cone with new setup in place and in the next days i will be busy adjusting the distance and see if i have any improvement. The work will be slow because i need to make a lot of tests with different distance for each test i need to let the magnetron to cool down for at least 5 minutes.

Iulian

Glad to hear you are OK.

Yes, you seem to be growing kind of a fan club on the Internet, with even rumors being spread on Twitter about your wellness. Happily, all false.


Offline Rodal

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(1) Magnetic susceptibilities of paramagnetic and diamagnetic materials... see anything interesting?
http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_6.html

mass susceptibility per kilogram, χ, at 20C

Vacuum    .  .  .  .  0
   
Polyethylene   .  .  .+0.2 *10^(-8)  (paramagnetic)
   
Aluminium  .  .  .  . +0.82*10^(-8)  (paramagnetic)

Copper      .  .  .  .  −0.107*10^(-8) (diamagnetic)

All very small values compared to iron, cast iron and other magnetic materials

The value for Polyethylene confirms that the magnetic permeability of HDPE shoud be close to 1.

However, this is for the real part of the susceptibility.  I recall that Paul March said that what was most interesting were the imaginary components of the permittivity and the permeability.

Can anyone find the imaginary permittivity and imaginary permeability for HDPE ?

The imaginary parts act as absorption coefficients (more in the direction of attenuation pointed out by Todd)

« Last Edit: 05/21/2015 07:41 PM by Rodal »

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