Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2104748 times)

Offline Mulletron

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We have Cannae dimensions. Page 6 of the anomalous thrust paper has some.
« Last Edit: 02/14/2015 05:21 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

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We have Cannae dimensions. Page 6 of the anomalous thrust paper has some.
How can one can conduct a thermal instability calculation with this information ?:

Quote from: page 6 of Brady et.al.
Each Cannae test article is approximately 11 inches in diameter and 4-5 inches between the ends of the beam pipes, not counting beam pipe extensions or antenna mounts.

It does not even include the most important buckling parameter: the thickness of the test article.
« Last Edit: 02/14/2015 05:38 PM by Rodal »

Offline Flyby

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From the video that Shawyer made of his test configuration  , many years ago, it is clear that the cone is moving towards the small diameter.

Not sure to why he wanted to represent his findings in a drawing that resembles a rocket engine (action- reaction) where there clearly is no exhaust force.. it kinda puzzles me...

Let's hope Paul March gives a conclusive answer to that so we can leave that confusion behind us.

Btw, ever since the EMdrive got worldwide publicity, a few months ago, I've been trying to follow the different discussions pro and contra between "believers" and "non-believers". I find the discussions here, on the NASA forum, by far the most constructive discussion.
Having only a basic scientific background, it is indeed sometimes tough to follow the discussions between professionals when they venture into the higher levels of mathematics, radiation physics and quantum mechanics, but even with only a 50% understanding it is great to see things unfold.

Strangely enough it gives me the same degree of excitement, then when I watched the live feed on the discovery confirmation of the Higgs-boson. Maybe, just maybe, we are indeed on the edge of a new chapter in space exploration...

Fantastic what you people established here. Really!
It is inspiring to see the collaboration from different fields in action, almost in real time...

Not sure, but if I may do a prudent suggestion, but in the discussion about magnetic permeability (some pages ago), wouldn't it make more economical sense to use iron instead of metglas. I believe it would be far easier to shape a slab of iron then finding a plate metglas 2714a. On condition iron scales linear compared to metglas, an iron backplate would still perform roughy 10 times better then copper.
Enough to validate all discussions till now for a reasonable price... ?

Geert

Offline Rodal

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From the video that Shawyer made of his test configuration  , many years ago, it is clear that the cone is moving towards the small diameter.

Not sure to why he wanted to represent his findings in a drawing that resembles a rocket engine (action- reaction) where there clearly is no exhaust force.. it kinda puzzles me...

Let's hope Paul March gives a conclusive answer to that so we can leave that confusion behind us.

Btw, ever since the EMdrive got worldwide publicity, a few months ago, I've been trying to follow the different discussions pro and contra between "believers" and "non-believers". I find the discussions here, on the NASA forum, by far the most constructive discussion.
Having only a basic scientific background, it is indeed sometimes tough to follow the discussions between professionals when they venture into the higher levels of mathematics, radiation physics and quantum mechanics, but even with only a 50% understanding it is great to see things unfold.

Strangely enough it gives me the same degree of excitement, then when I watched the live feed on the discovery confirmation of the Higgs-boson. Maybe, just maybe, we are indeed on the edge of a new chapter in space exploration...

Fantastic what you people established here. Really!
It is inspiring to see the collaboration from different fields in action, almost in real time...

Not sure, but if I may do a prudent suggestion, but in the discussion about magnetic permeability (some pages ago), wouldn't it make more economical sense to use iron instead of metglas. I believe it would be far easier to shape a slab of iron then finding a plate metglas 2714a. On condition iron scales linear compared to metglas, an iron backplate would still perform roughy 10 times better then copper.
Enough to validate all discussions till now for a reasonable price... ?

Geert

Welcome to the forum and thanks for the great post  :)

You are correct that we can ascertain a direction of movement from the above Shawyer video.

Unfortunately (see image below) Shawyer's presentation muddles the picture because, that is the "SPR Demonstrator Engine" which Shawyer says had forces (and hence movement ?) in both directions towards the small diameter and also towards the big diameter  :(

Also according to Shawyer, the Chinese EM Drive and the Shawyer "Flight Thruster" move in opposite direction to all the following EM Drives: the NASA EM Drive, to the Cannae (both room temperature and superconducting) and to the SPR tapered cavity with dielectric.

I look forward to Paul March's answer to the two questions I posed above.
« Last Edit: 02/14/2015 06:20 PM by Rodal »

Offline aero

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Do we know what the Eagleworks vacuum chamber is made of? I think I remember it being a Stainless Steel chamber but I can't find confirmation of that at the moment. It is kind of important to me because the evanescent fields from my simulation runs overlap the edges of the vacuum chamber. That means to me, that I need to add the vacuum chamber to my meep model. And expect different answers as a result.
Retired, working interesting problems

Offline Rodal

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Do we know what the Eagleworks vacuum chamber is made of? I think I remember it being a Stainless Steel chamber but I can't find confirmation of that at the moment. It is kind of important to me because the evanescent fields from my simulation runs overlap the edges of the vacuum chamber. That means to me, that I need to add the vacuum chamber to my meep model. And expect different answers as a result.
That's an excellent question, @aero, thanks for bringing it up.  I agree with your reason for asking it.

It is likely to be either Stainless Steel or Aluminum

 Look forward to March's answer.
« Last Edit: 02/14/2015 06:05 PM by Rodal »

Offline TMEubanks

Hello;

I have been following this for a while, but this is my first post. (I have corresponded with Josť Rodal about this in the past.) My congratulations on a spirited and informative discussion of some thorny issues.

It is apparent that the E&M waves on the outside of the drive extend far enough to interact with the walls of the vacuum chamber (not to mention the support, pendulum and other mechanisms inside the chamber). Thus, to verify (or rule out) the reality of the measured thrust, it will be crucial to calculate the force caused by these interactions. As I was reading through the forum, this point impressed itself upon me, and I was going to ask if it has been done but, of course, if we don't know the material of the chamber, it hasn't.

MEEP should be adequate to do this, as this is entirely a conventional physics effect, and I would encourage someone to take this on.

Offline Rodal

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Hello;

I have been following this for a while, but this is my first post. (I have corresponded with Josť Rodal about this in the past.) My congratulations on a spirited and informative discussion of some thorny issues.

It is apparent that the E&M waves on the outside of the drive extend far enough to interact with the walls of the vacuum chamber (not to mention the support, pendulum and other mechanisms inside the chamber). Thus, to verify (or rule out) the reality of the measured thrust, it will be crucial to calculate the force caused by these interactions. As I was reading through the forum, this point impressed itself upon me, and I was going to ask if it has been done but, of course, if we don't know the material of the chamber, it hasn't.

MEEP should be adequate to do this, as this is entirely a conventional physics effect, and I would encourage someone to take this on.

Welcome to the forum, Marshall.  It is great to have an MIT Astrophysicist in this thread who has a main-belt asteroid named after him.  I hope you stay here for a while and continue giving us your guidance, suggestions and comments :)
« Last Edit: 02/14/2015 07:48 PM by Rodal »

Offline Star-Drive

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All:

Sorry I didn't make the time to participate in this ME-Drive forum for the last 6-to-8 months up, but I will try to catch up with everyone else in due course.  That said lets try to answer the questions that popped up since my morning post.

1.  I was not the lead author for the Eagleworks' 2014 AIAA/JPC paper and in fact I only supplied pictures and data for same during that period because Dr. White thought that my time was best spent in the lab gathering data instead of report writing.  Thus some of the details that Dr. Rodal is looking for may have been lost or garbled in the report writing by the others on the author list.

2.0  The thrust vector for the four resonant modes examined in detail, (the cavity's fundamental TM010, TE012, TM211 & TM212 for our copper frustum is normally in the frustum's large OD to small OD direction for most, but not all the E&M resonant modes checked.  However, one can also reverse this thrust vector for this copper frustum by just changing which excited resonant mode is used and/or mounting the dielectric discs at the large OD end of the cavity instead of the small OD end, see attached resonant mode map.  Sorry, but a one size fits all solution to this EM-Drive thrust direction is not available in this venue because of the importance of the ExB phase relationship of the expressed Lorentz forces between the excited E&M fields and the possible dielectric and QV plasma flow phenomenon that may be at work in each resonant mode expressed.  That is why this type of E&M thruster is so hard to get a handle on, for there are far too many degrees of freedom in the system to track let alone directly control.

3. The Eagleworks vacuum chamber's main body is made from 304L stainless steel while its swing out door is made from aluminum.  Most of the nuts and bolts in the vacuum chamber are also made from 18-8, 304 or 316 stainless steel alloys. 

Now to try to answer Dr. Rodal's specific questions:

"1) In the NASA experiments the truncated cone's center of  mass moved towards the [  ? ] diameter end  (where ? stands for big or small)"

For the TE012 and TM212 excited resonant modes, our copper frustum's center of mass moved toward the small OD end of the frustum when RF power was applied to the copper frustum.

"2) In the NASA experiments, we at NASA Eagleworks define the thrust force direction to be in the  [? ] direction as the movement of the truncated cone's center of  mass  (where ? stands for same or opposite)"

For just the TE012 & TM212 excited resonant modes, the thrust force direction AKA thrust vector was observed to be in the same direction as the movement of the frustum's center of mass when RF power was applied to the frustum's magnetic loop antenna.

If I missed a question along the way keep asking, but I'll be in and out of the house for the rest of the day, so I may not get to answer them until late this evening or tomorrow afternoon USA based CST.

Best, Paul M.

Offline Rodal

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All:

Sorry I didn't make the time to participate in this ME-Drive forum for the last 6-to-8 months up, but I will try to catch up with everyone else in due course.  That said lets try to answer the questions that popped up since my morning post.

1.  I was not the lead author for the Eagleworks' 2014 AIAA/JPC paper and in fact I only supplied pictures and data for same during that period because Dr. White thought that my time was best spent in the lab gathering data instead of report writing.  Thus some of the details that Dr. Rodal is looking for may have been lost or garbled in the report writing by the others on the author list.

2.0  The thrust vector for the four resonant modes examined in detail, (the cavity's fundamental TM010, TE012, TM211 & TM212 for our copper frustum is normally in the frustum's large OD to small OD direction for most, but not all the E&M resonant modes checked.  However, one can also reverse this thrust vector for this copper frustum by just changing which excited resonant mode is used and/or mounting the dielectric discs at the large OD end of the cavity instead of the small OD end, see attached resonant mode map.  Sorry, but a one size fits all solution to this EM-Drive thrust direction is not available in this venue because of the importance of the ExB phase relationship of the expressed Lorentz forces between the excited E&M fields and the possible dielectric and QV plasma flow phenomenon that may be at work in each resonant mode expressed.  That is why this type of E&M thruster is so hard to get a handle on, for there are far too many degrees of freedom in the system to track let alone directly control.

3. The Eagleworks vacuum chamber's main body is made from 304L stainless steel while its swing out door is made from aluminum.  Most of the nuts and bolts in the vacuum chamber are also made from 18-8, 304 or 316 stainless steel alloys. 

Now to try to answer Dr. Rodal's specific questions:

"1) In the NASA experiments the truncated cone's center of  mass moved towards the [  ? ] diameter end  (where ? stands for big or small)"

For the TE012 and TM212 excited resonant modes, our copper frustum's center of mass moved toward the small OD end of the frustum when RF power was applied to the copper frustum.

"2) In the NASA experiments, we at NASA Eagleworks define the thrust force direction to be in the  [? ] direction as the movement of the truncated cone's center of  mass  (where ? stands for same or opposite)"

For just the TE012 & TM212 excited resonant modes, the thrust force direction AKA thrust vector was observed to be in the same direction as the movement of the frustum's center of mass when RF power was applied to the frustum's magnetic loop antenna.

If I missed a question along the way keep asking, but I'll be in and out of the house for the rest of the day, so I may not get to answer them until late this evening or tomorrow afternoon USA based CST.

Best, Paul M.

Thank you for the very clear answers !

and thanks again for two outstanding contributions just on the last few months:

1) The first time (to my knowledge) that an EM Drive is tested under hard vacuum, with experimentally confirmed  thrust (at a thrust/PowerInput level amply exceeding the one for a photon rocket).

2) The first time (to my knowledge) that the actual mode shape (TM21 at the big diameter) of an EM Drive is experimentally confirmed.
« Last Edit: 02/14/2015 09:23 PM by Rodal »

Offline Star-Drive

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PS:

The Cannae pill box cavity with asymmetric RF feeds was made from 2.0mm thick spun copper and 1.0 inch ID copper plumbing pipe and fittings. 

Correction: The thrust vector for this Cannae test article for its ~928MHz, TM010 resonant mode was always along its centerline toward its long 1.0" ID  diameter tube end where the coaxial E-field probe RF power input antenna with a Teflon dielectric cylinder used for 50 ohm impedance matching was mounted.  The opposite end of this Cannae pill box resonant cavity had a shorter 1.0" ID copper tube that housed the RF sense antenna.   

And this thruster was mounted almost on top of the torque pendulum arm's centerline, so most of its left/right thermal expansions should have canceled out.

Best, Paul M.
« Last Edit: 02/14/2015 09:38 PM by Star-Drive »
Star-Drive

Offline Rodal

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....
If I missed a question along the way keep asking, but I'll be in and out of the house for the rest of the day, so I may not get to answer them until late this evening or tomorrow afternoon USA based CST.

...
@aero had this question,

Quote from: @aero
please look at this model and tell me if your read of Paul March's description of the cavity joins are as shown, or is there a cone flange pinched under the Teflon gasket which is held in place by a thicker copper ring.

answering it would help better model evanescent waves with MEEP.  (Please click on the original picture inserted in his message:  http://forum.nasaspaceflight.com/index.php?topic=36313.msg1331345#msg1331345, to better appreciate the geometry he is interested in)

« Last Edit: 02/14/2015 10:01 PM by Rodal »

Offline Mulletron

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The fact that it has reverse too pretty much clinches it. That speaks volumes.


Challenge your preconceptions, or they will challenge you. - Velik

Offline Rodal

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The fact that it has reverse too pretty much clinches it. That speaks volumes.



You are right that "it speaks volumes", I agree, the good news about the EM Drive just keeps on coming from Eagleworks. but before "clinching it" we still have to address the electromagnetic field interaction, e.g. evanescent wave interaction with the vacuum chamber and other fixed components, as the ExB field phase relationship changes, don't we ?
« Last Edit: 02/14/2015 11:26 PM by Rodal »

Offline SleeperService

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Watching closely..
I think a zero-gee experiment is what we need.
Mr Musk would be up for this sort of thing as a payload for one of his re-used rockets. For free.
Can we come up with a self-contained payload to test this?
If not, why not?

Offline Mulletron

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I can think of 3 ways to test the evanescent wave theory. 1) Is the measured thrust the same with the chamber door open and closed? 2) Is the thrust still there when the test article is rolled out of the chamber. Not sure if 2 is possible.....3) Change the conditions near the resonant cavity; like wrap the thing in thick foam and then wrap all that with foil, see what the thrust does.

I know that evanescent modes won't couple with something that is not capable of accepting the resonant mode; they are by definition, non propagating, so that likely rules out the support structures. Aluminum beams aren't resonant structures or transmission lines. This is how wireless phone charging systems are safe to be around. They only can couple with the receiving antenna, not other stuff or people. Also the effect is evident in those videos I posted way back about quantum tunneling between prisms pushed together.
 
At the same time, it probably does not rule out the chamber. From what I've read, evanescent modes are strongest within 1/3 of a wavelength and falls off exponentially with the distance, so how far away is the chamber from any point of the test article? I dropped the evanescent wave thing long ago because it is just too far fetched IMHO and proving it or disproving it didn't seem possible at the time. What really ruled it out for me was that only the H (magnetic) component of ExH can get through the cavity walls, which means it could never propagate. Aero seems close to an answer, which is nice.

http://milesmathis.com/evane.pdf
http://en.wikipedia.org/wiki/Resonant_inductive_coupling
http://forum.nasaspaceflight.com/index.php?topic=29276.msg1284471#msg1284471 way back machine
Challenge your preconceptions, or they will challenge you. - Velik

Offline SleeperService

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I'm thinking an xU cubesat with a big battery. Spin stabilized even at 50 micro newtons we would see positive results within an hour, tracked from the ground.

Offline Mulletron

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http://en.m.wikipedia.org/wiki/Marin_Solja%C4%8Di%C4%87

Ask him. He's an evanescent wave expert at MIT.

Below are the approximate resonant modes of the vacuum chamber. Not taking into account perturbation. Doesn't look like the vacuum chamber can accept the modes within the test article.
« Last Edit: 02/15/2015 07:56 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline SleeperService

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I'm thinking an xU cubesat with a big battery. Spin stabilized even at 50 micro newtons we would see positive results within an hour, tracked from the ground.
I hoped to be experimental about this.
Experiment trumps theory every time.
With what we have, lets have an experiment in zero-g

Online RotoSequence

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I'm thinking an xU cubesat with a big battery. Spin stabilized even at 50 micro newtons we would see positive results within an hour, tracked from the ground.
I hoped to be experimental about this.
Experiment trumps theory every time.
With what we have, lets have an experiment in zero-g

I'd rather wait to see a confidence building ground experiment before committing to something of that scale. It shouldn't be too hard (or too expensive) to hit the target thrust levels for third party university verification, and it would almost certainly be much less expensive.

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