Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1802309 times)

Offline wembley

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A bit of an update - can't release details from Tajmar yet, but keep watching...

http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission

Offline SeeShells

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http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409010#msg1409010

Was editing when kicked off the internet...

NASA found Transverse Electric mode TE012 to be the one that produced the highest force/InputPower (http://emdrive.wiki/Experimental_Results), however they could not replicate it consistently (it is in their report).  NASA found the Transverse Magnetic Modes to be easier to excite and reproduce apparently ?  (They also explain that TM modes are better according to White's QV theory)

It is also interesting that apparently Shawyer started with TM modes and later on switched to TE modes.

Yang has been using TE modes apparently.
I agree what you see as well. I'm just looking at the red flags and this is one of them. One can't help but wonder why the Chinese have pursued the TE modes along with Shawyer, whereas I read a listing on a image where EW elected to ignore the Chinese thrusts because it couldn't be verified even when their highest thrust was an TE mode. (don't know the timeline for the discounting and the testing for EW TEmode vs the Chinese)

Image clipped from a larger picture and sharpened for clarity.

Offline Rodal

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A bit of an update - can't release details from Tajmar yet, but keep watching...

http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission

Look at this:

http://forum.nasaspaceflight.com/index.php?topic=37642.msg1408539#msg1408539

I find the extremely small force/InputPower measured by Tajmar NOT to be something that Shawyer should be so  encouraged about, for the reasons in my post.  I don't see anything in Tajmar's results pointing towards the practicality of an EM Drive mission to Pluto in 18 months anytime soon.  We will see...

It certainly would be nice to find out I'm wrong about this :)
« Last Edit: 07/24/2015 04:05 PM by Rodal »

Offline Rodal

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http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409010#msg1409010

Was editing when kicked off the internet...

NASA found Transverse Electric mode TE012 to be the one that produced the highest force/InputPower (http://emdrive.wiki/Experimental_Results), however they could not replicate it consistently (it is in their report).  NASA found the Transverse Magnetic Modes to be easier to excite and reproduce apparently ?  (They also explain that TM modes are better according to White's QV theory)

It is also interesting that apparently Shawyer started with TM modes and later on switched to TE modes.

Yang has been using TE modes apparently.
I agree what you see as well. I'm just looking at the red flags and this is one of them. One can't help but wonder why the Chinese have pursued the TE modes along with Shawyer, whereas I read a listing on a image where EW elected to ignore the Chinese thrusts because it couldn't be verified even when their highest thrust was an TE mode. (don't know the timeline for the discounting and the testing for EW TEmode vs the Chinese)

Image clipped from a larger picture and sharpened for clarity.

Well, I trust NASA Eagleworks more than Yang.  Neither Yang nor Shawyer ever reported a single test in vacuum.  We will see :)
« Last Edit: 07/24/2015 04:01 PM by Rodal »

Offline SeeShells

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http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409010#msg1409010

Was editing when kicked off the internet...

NASA found Transverse Electric mode TE012 to be the one that produced the highest force/InputPower (http://emdrive.wiki/Experimental_Results), however they could not replicate it consistently (it is in their report).  NASA found the Transverse Magnetic Modes to be easier to excite and reproduce apparently ?  (They also explain that TM modes are better according to White's QV theory)

It is also interesting that apparently Shawyer started with TM modes and later on switched to TE modes.

Yang has been using TE modes apparently.
I agree what you see as well. I'm just looking at the red flags and this is one of them. One can't help but wonder why the Chinese have pursued the TE modes along with Shawyer, whereas I read a listing on a image where EW elected to ignore the Chinese thrusts because it couldn't be verified even when their highest thrust was an TE mode. (don't know the timeline for the discounting and the testing for EW TEmode vs the Chinese)

Image clipped from a larger picture and sharpened for clarity.

Well, I trust NASA Eagleworks more than Yang.  Neither Yang nor Shawyer ever reported a single test in vacuum.  We will see :)
True, we will see. It somehow feels like this all is coming to a head. I'm still planing to build and test because I simply feel there isn't a solid and truly verifiable theory as to why this works and maybe this old gal will excite enough brain cells to find something useful. So keep me on the straight and narrow and focused so I don't try to suck up everything at once.

Offline aero

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The stress at the small base is practically zero for all the previously shown time steps.  In order to save bandwidth I only show the last step

Therefore (?), all of the energy is attenuated by the side walls before it reaches the small base?

Todd

Dr. Rodal,
I suggest that I move the small base cuts one row toward the center to confirm that the cut I made was not actually inside the surface of the copper base. If you get markedly different results one row further inward, doesn't that mean that the current cut was most likely in the wrong place? And if you get very similar results, does that confirm the cut location? Or do I need to move the cut further inward to confirm? And even if the current cut is in the correct location, wouldn't a few cuts in toward the center tell us something? How many and how much?

Thanks for your offer to further clarify this.

I looked at the matrix, and established that the inner electromagnetic fields outermost positions in the longitudinal x direction are at:


Row 16 (rows ranging from 1 to 229) which should be the "Big Base" location

Row 215 (rows ranging from 1 to 229) which should be the "Small Base" location

Please confirm whether the present locations you supplied of the Big Base and the Small Base are at these locations (notice that the first row is defined as 1, not 0) or at another location (and if so at what location).

Thanks

______________

EDIT:

From your message:

@SeeShell -
Your .png and .csv files data is/are up have been uploaded here:

https://drive.google.com/folderview?id=0B1XizxEfB23tfm04QWNVVVVvT3gtcVAzRUp6T1BCLVpoV0EyeVVKR2ZxQkp2a3NKcUNPMU0&usp=sharing

I uploaded my meep data request file/form to hopefully explain what the data is, although it needs more English and fewer Scheme statements. The inside big end is at row 15 and small end at row 216 of the csv files, and the total run meep time t = 13.054 (6527 timesteps).

you don't specify whether you are counting rows starting at 0 or at 1 (1 is the most common convention), but it is apparent that the location of the big base and small base cuts appear to be 1 row beyond the correct location for the field next to the boundary, which should be 16 and 215 instead of 15 and 216

I made the cuts of the .h5 file at rows 15 and 216. Looks like I messed up the cuts by converting to the csv row numbers before making the cuts on the .h5 file. Of course I need to leave them relative to the .h5 file while cutting the .h5 file. So I cut the .h5 file at row 15 (the csv line number I applied to the .h5 file line number 15, starting from 0, and at row 216 which applied to the .h5 file row number 216 starting at 0. That means that my cuts were really at rows 16 and 217 in the output csv rfiles.

Cutting the Big end one row closer to the antenna will make a huge difference as one row in the lattice corresponds to 0.0012 mm, a large fraction of the separation between the big base and the antenna. And of course cutting the small end one row closer puts it inside the metal so that data is meaningless.

I will re-run the csv data. I understand that you want the .CSV file rows 16 and 215, counting from 1. That will make them rows 15 and 214 of the .h5 file, counting from 0. Please verify
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Offline TheTraveller

I agree what you see as well. I'm just looking at the red flags and this is one of them. One can't help but wonder why the Chinese have pursued the TE modes along with Shawyer, whereas I read a listing on a image where EW elected to ignore the Chinese thrusts because it couldn't be verified even when their highest thrust was an TE mode. (don't know the timeline for the discounting and the testing for EW TEmode vs the Chinese)

While not a dielectric fan or expert, exciting TM mode has the E field banging on the end plates and dielectric. When Shawyer used dielectrics, he excited in TM mode as EW are doing.

After giving away dielectrics, Shawyer and Prof Yang switched to TE mode as that way the more powerful H field is banging away on the end plates and delivering more Force than the E field (TM mode) can.

As Prof Yang commented:
Quote
The thrust curves demonstrate that on the surfaces of the major
and the minor end plates, the magnetic thrust is two orders
of magnitude higher than the electric thrust.

Seems go for TM modes if using dielectrics, get very low "electric thrust" Force generation or go with no dielectrics, TE modes, "magnetic thrust", to get the best Force generation.

BTW back in hospital, last surgery. If this doesn't work, will be time to use the magnetron on my pelvic regions.
« Last Edit: 07/24/2015 05:53 PM by TheTraveller »
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Online aceshigh

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I hope we might soon get a The Space Show program with Dr Paul March or Dr Sonny White.

In the Space Show interview with Dr Jim Woodward, about Mach Effect Theory (link in the related thread), in the beginning of the interview (around minute 15-20 I think), the show host Dr David Livingstone talks with Dr Jim Woodward about Dr White and Dr Paul March (Woodward seems to be acquainted with Dr White and I know he IS acquainted with Paul March), and complains that NASA is making it very difficult, to not say impossible, for him to contact Dr White for a new interview to talk about EM Drive, Warp Drive, etc.

Dr Jim Woodward then told Livingstone that he would later give him the personal phone of Paul March, so he could call him and get him as a show guest.


Let's hope...

Offline Rodal

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..

While not a dielectric fan or expert, exciting TM mode has the E field banging on the end plates and dielectric. When Shawyer used dielectrics, he excited in TM mode as EW are doing.

After giving away dielectrics, Shawyer and Prof Yang switched to TE mode as that way the more powerful H field is banging away on the end plates and delivering more Force than the E field (TM mode) can.

As Prof Yang commented:
Quote
The thrust curves demonstrate that on the surfaces of the major
and the minor end plates, the magnetic thrust is two orders
of magnitude higher than the electric thrust.

Seems go for TM modes if using dielectrics, get very low "electric thrust" Force generation or go with no dielectrics, TE modes, "magnetic thrust", to get the best Force generation.

BTW back in hospital, last surgery. If this doesn't work, will be time to use the magnetron on my pelvic regions.

We care about you.  Thank you for keeping in touch.  Best,

Offline Eer

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QUESTION: Why do you count from zero ?  Mathematica counting rows or columns starts at 1.  It is actually arbitrary, but it would be nice to agree on a common convention,  I suggest to use the common mathematical convention to count rows and columns starting at one unless there is some compelling reason to do otherwise.

The convention goes back to counting fingers, as the integers starting at one were known much before they came up with the notion of zero as a number.


The On-Line Encyclopedia of Integer Sequences

https://oeis.org/A000027

http://mathworld.wolfram.com/CountingNumber.html

http://mathworld.wolfram.com/NaturalNumber.html


Yes, I know that Wikipedia does not take a position:   https://en.wikipedia.org/wiki/Natural_number  <<There is no universal agreement about whether to include zero in the set of natural numbers. Some authors begin the natural numbers with 0, corresponding to the non-negative integers 0, 1, 2, 3, ..., whereas others start with 1, corresponding to the positive integers 1, 2, 3, ....[7][8][9][10] This distinction is of no fundamental concern for the natural numbers as such, since their core construction is the unary operation successor. Including the number 0 just supplies an identity element for the (binary) operation of addition, which makes up together with the multiplication the usual arithmetic in the natural numbers, to be completed within the integers and the rational numbers, only.>>

One reason for starting with zero relates to how array and table data structures are addressed in memory - using a base address and an offset to the beginning of data for the record or array entry desired.  In such a scheme, offset 0 references the first entry or element or record of the table or array.

In the C language, which is really just a cross platform assembler, this is represented as the address of an entry in the array A[entry].  The first one is 0, the second is 1 and so forth, because 0 multiplied by the length of the entry, when added to the base address (pointer) of A gets you the address of that 1st entry in the table.  Ditto 1 times the entry length gets you the starting offset in the table of the 2nd entry.

It's a source of continuing confusion.  Yes, make clear what convention you are using (0-based or 1-based arrays) when discussing them.

Strongly typed languages, including Pascal and Ada, make it practical to define arrays as ranging from 1..max, but C, being a glorified assembler, only represents arrays as 0..max-1.

I took your question  to be an honest one and not rhetorical.  Sorry if I missed intended irony.

Offline aero

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Counting the .h5 rows from 0 is not my choice, it is the way they are numbered and I don't get to choose.

Quote
rows 16 and 215, counting from 1 as I wrote. (rows ranging from 1 to 229)

so that will be rows 15 and 214 for .h5 rows ranging from 0 to 228.

I have attached a screen shot of part of the big end and the antenna, showing the separation. This screen shot was taken after 3 meep time-steps. You can see the field energy penetrating the surface of the big end and observe that the antenna is very close. Well, I'll attach it to the following post as I can't add an image by editing this post.
« Last Edit: 07/24/2015 06:24 PM by aero »
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Offline Rodal

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Continuing from this: http://forum.nasaspaceflight.com/index.php?topic=37642.msg1408974#msg1408974 and this one:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1408555#msg1408555

Here are the Poynting vector fields in the xy and xz planes (x being the longitudinal axis of axi-symmetry of the cone and y and z are perpendicular Cartesian axes) for Yang/Shell with the Antenna in the Axial x orientation next to the big base, at time slice 00 (the 14th previous time slice to the end of the run).  In contrast with the Poynting vector field previously shown for rfmwguy/NSF-1701, this Yang/Shell case shows all Poynting vector flux concentrated at the antenna and a negligible amount elsewhere
« Last Edit: 07/24/2015 06:22 PM by Rodal »

Offline kitsuac

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Because EW is using real world materials with analog sources, not discretized sources and idealized copper that doesn't seem to heat or suffer significant losses of any sort. Perhaps, just guessing here, perhaps if the node granularity was less than the skin depth of the copper, we could see more realistic skin effects. But its not so we can't.

I'm currently running some tests using MIT's starcluster to automate a cluster of meep servers. Using a higher resolution setting in meep of course is much slower, but I think it may allow for more parallelism. If that proves to be true, higher resolutions could be run at a more feasible speed at the expense of using a more costly cluster of servers. Would that be helpful to you folks?

Yes it would.

My point of Node granularity being less than skin depth is simply that with the current resolution, node granularity, being about 1.2 mm, is about 1000 times larger than skin depth, and it is within the skin where the losses must occur. This is true for both the sides and the ends. As Dr. Rodal posted, Q is inversely proportional to losses but running at the current resolution meep cannot "sample" the skin depth so losses there don't exist in the numerical model. Hence the only "known" source of losses is ignored --> very high Q.

I addressed this issue late last year on the meep-discuss mailing list and got two responses.

First response, can meep use a high resolution for the geometry of the skin while low resolution in the rest of the lattice where 10 nodes per wavelength is adequate? The response was no, meep doesn't do that but perhaps I should use a commercial software as some do have that capability, or alternatively as the source code is available, I am welcome to write my own functions.

Second response, which we may now have the talent to address here was,

"Fictitious materials can be used in place of the metal skin, materials designed to have a gross response like copper except that the response occurs over a much greater skin depth more suitable to the resolution at which the model runs."

I still have no idea how to design such a material (a Drude model of some sort) but it would be straight forward to increase the thickness of the cavity material in the model, within reason, to accommodate such a fictitious material.

Just an update in case anyone is interested in meep scalability. Increasing resolution did in fact increase parallelism (did some experiments using 4/8/16/32/64/128 worker nodes in starcluster). Unfortunately, the step preceding the first meep time step does not speed up by throwing more workers at it. Increasing the number of workers improved the time step speed nearly proportionally to the number of workers, but after a certain number of workers the preceding step began taking so long that I had to give up and kill the experiment (left it running for about an hour, which isn't cheap at that scale). There is also an unfortunate limit where a resolution of > ~800 fails because some integer value wraps around the max, turns negative, and an error is thrown.

I'll likely write up an article with simple steps for anyone to setup starcluster + meep. Perhaps someone more well versed in meep would be able to get rid of the parallelism bottleneck(s) and at that point having a way to scale things up will become useful. To those talking about GPU optimizing meep - Good luck, you will most likely run into the same issue and then some.

Offline aero

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Here is the image  I referred to above.
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Offline SeeShells

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I agree what you see as well. I'm just looking at the red flags and this is one of them. One can't help but wonder why the Chinese have pursued the TE modes along with Shawyer, whereas I read a listing on a image where EW elected to ignore the Chinese thrusts because it couldn't be verified even when their highest thrust was an TE mode. (don't know the timeline for the discounting and the testing for EW TEmode vs the Chinese)

While not a dielectric fan or expert, exciting TM mode has the E field banging on the end plates and dielectric. When Shawyer used dielectrics, he excited in TM mode as EW are doing.

After giving away dielectrics, Shawyer and Prof Yang switched to TE mode as that way the more powerful H field is banging away on the end plates and delivering more Force than the E field (TM mode) can.

As Prof Yang commented:
Quote
The thrust curves demonstrate that on the surfaces of the major
and the minor end plates, the magnetic thrust is two orders
of magnitude higher than the electric thrust.

Seems go for TM modes if using dielectrics, get very low "electric thrust" Force generation or go with no dielectrics, TE modes, "magnetic thrust", to get the best Force generation.

BTW back in hospital, last surgery. If this doesn't work, will be time to use the magnetron on my pelvic regions.

Thank You for you input and insight. And hoping all goes well for you.

Shell

Offline frobnicat

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Taking the numbers for making this flying saucer to fly (last part before conclusion) 1.9*10^22 A/s, so first second of hovering needs about 10^22 A, and only increasing quadratically. Any copper coil would sublimate instantly, going superconducting niobium-tin @ 200000 A/cm would require a coil with an astonishing section of 5 trillion square meters, more than surface of India...

I apologize if I misunderstand, but there are two dots above the I in that equation.  I believe that to mean that the rate of the change in the change of current flow needs to be ~ 10^22 amperes per second squared, not that the total power requirements are of that order of magnitude.  The latter part of the same paragraph implies that is roughly 5 amps at 10GHz.

Is that right?

Is that incorrect?

What I said was the current requirement at the end of 1s of hovering. In general, the current requirement for their flying saucer goes as I(t)=0.5*1.9*1022*t where t is duration of steady state hovering. The "imply a few amps at 10GHz" mention is a farce, 10GHz means a periodic current, so while it might be true that they show a force enough to levitate for a fraction of a nanosecond on achievable AC current, the next half-period(*) of such achievable AC current the force is reversed, and so on, and 0 on average.

Eq. 48 says it all, force proportional to I_dot_dot, not I_dot_dot nor absolute_value(I_dot_dot).
Take a periodic current, any shape (even asymmetric, ramp up, down, whatever) it decomposes on sum of sines (Fourier...), the second derivative of the sum of components is the sum of the second derivative of components (derivation is linear) each component yielding 0 net second derivative value on average. Periodic current => 0 force, according to their own formula.

The other way around, constant force => constant second derivative of current => quadratically (wrt time) diverging current. A sine is not a quadratic function, even if it locally closely follows quadratic shape for fraction of period. A quadratic diverging excitation is required. So why the authors seem to imply that an argument about an AC current of reasonable magnitude is relevant ? Notice that they don't speak of power, nor of duration of the hovering...

Thanks @WarpTech for pointing out other blanks in this paper (AC current => not strictly 0 force actually, but only at photon rocket efficiencies at most).

(*) corrected period -> half-period
« Last Edit: 07/24/2015 09:36 PM by frobnicat »

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Taking the numbers for making this flying saucer to fly (last part before conclusion) 1.9*10^22 A/s, so first second of hovering needs about 10^22 A, and only increasing quadratically. Any copper coil would sublimate instantly, going superconducting niobium-tin @ 200000 A/cm would require a coil with an astonishing section of 5 trillion square meters, more than surface of India...

I apologize if I misunderstand, but there are two dots above the I in that equation.  I believe that to mean that the rate of the change in the change of current flow needs to be ~ 10^22 amperes per second squared, not that the total power requirements are of that order of magnitude.  The latter part of the same paragraph implies that is roughly 5 amps at 10GHz.

Is that right?

Is that incorrect?

... so while it might be true that they show a force enough to levitate for a fraction of a nanosecond on achievable AC current, the next period of such achievable AC current the force is reversed, and so on, and 0 on average.
...

No, that's not quite right. When the two current loops are separated by 1/4 wavelength, the force exerted on both loops is full-wave rectified to be in the same direction. If a high enough frequency, current at a close separation can be achieved, the force due to the magnetic field is not negligible! However, the force due to the electric field is not negligible either, which is where the authors are missing the opposing force. The magnetic force and the electric force, "independently" do not average 0 over a full sin(wt) cycle. They are both full-wave rectified but in opposite directions.
Todd


Offline aero

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Offline frobnicat

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... so while it might be true that they show a force enough to levitate for a fraction of a nanosecond on achievable AC current, the next period of such achievable AC current the force is reversed, and so on, and 0 on average.
...

No, that's not quite right. When the two current loops are separated by 1/4 wavelength, the force exerted on both loops is full-wave rectified to be in the same direction. If a high enough frequency, current at a close separation can be achieved, the force due to the magnetic field is not negligible! However, the force due to the electric field is not negligible either, which is where the authors are missing the opposing force. The magnetic force and the electric force, "independently" do not average 0 over a full sin(wt) cycle. They are both full-wave rectified but in opposite directions.
Todd

I trust you on that, I was just taking the consequence of their own equation, not questioning its validity. Their equation tells a 0 net average force on AC current (corrected in my comment : period -> half-period).
« Last Edit: 07/24/2015 09:41 PM by frobnicat »

Offline Rodal

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@Rodal and SeeShell,

Rerun csv files are uploaded, here

https://drive.google.com/folderview?id=0B1XizxEfB23tflNPTnJEcWVZNkVJSUhuUkUtdzJEaWlSRWR0R2xsdmN4Y05mdlBzRHAza28&usp=sharing
Did you make any changes other than to output different locations (like changed mesh, time step, time slices, scaling factor, material Drude model, antenna location and type, etc.) ?

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