Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1798593 times)

Offline deltaMass

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Perhaps a poll would be in order?
Easier to just count the Likes

Offline deltaMass

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ACD
Asymmetric Cavity Drive

This debate is actually not really helpful.  :-\ The one who explains the correct physics will give it a name in his paper, or do it democratically, but let's go back to science right now ::)

This for example:
ghost modes in imperfect waveguides
http://bayes.wustl.edu/etj/articles/ghost.modes.pdf
Interesting paper. To explore further, cast a jaundiced eye on that shiny new gleaming copper frustum, and reach for the planishing hammer  8)

Watchword: dimples.
Can they be MEEPed?

Offline DrBagelBites

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DIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489

A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.

Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.

Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...

So, a problem I ran into is that when doing it the sheet method and you have the flat pattern of the section without top and bottom, the height of the frustum isn't the correct gauge for the width of the sheet metal.

For instance, I created a printout for a frustum cavity of height 9", and it did not fit on a sheet of width 12". Hence, I had to buy more sheet metal in order to correctly fit the flat diagram.

So, for any other builders using sheets, the dimension that you want to find in order to get the right sized sheet is the height from the "points" to the bottom of the larger diameter curve.

-I

Offline kdhilliard

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The Space Show will have Dr. Jim Woodward on tonight.

 Tuesday, July 21, 2015; 7-8:30 PM PDT (10-11:30 PM EDT; 9-10:30 PM-1 PM CDT): We welcome DR. JJIM WOODWARD back to the show to update us on his work with a Mach effect drive impulse engine- and gravitational physics.

http://www.thespaceshow.com/

The show has archived: http://thespaceshow.com/detail.asp?q=2509
Direct link to audio: http://archived.thespaceshow.com/shows/2509-BWB-2015-07-21.mp3

Both Sonny White and Paul March were mentioned in passing, but EM Drive was not specifically discussed.

~Kirk

Online SeeShells

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DIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489

A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.

Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.

Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...
Had to do with electric trolleys I think. Before my time.

One thing you need to be aware of in copper is that it's mixed with tin to prevent corrosion, 80-90% mix is normal and if not 99% pure copper it will cause more heating signal loss and not be as a good cavity.

Shell
PS:
I'm still waiting (have some time) for my last piece of copper is holed out to my specs, was hoping to have a simulation run,  it is 99% pure the same they use in waveguides.

Offline Johnny_Tsunami

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Use a simple internal working name (that describes the effect) for the overall project of discovering the theory/physics/mechanics of how (or if) this works, and take a hint from the marketing gurus in big pharma who put the scientific name in small print under the BIG EASY TO REMEMBER MARKETABLE NAME of a new drug splashed across the (insert media here). Brand it when there is a device that you want to have the masses interested enough in to fund it. Big companies may invest in it, but the masses still fund it, whether they want to ride on it or have it bounce reruns of Cheers to them from orbit.                                       

Offline flux_capacitor

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Can someone here whose job is in microwave physics and resonant cavities industry for years (not someone who is learning stuff through online sources) please clarify the following facts that are not even well explained among 600 pages of three consecutive EmDrive threads:

- Which conveys momentum in a waveguide: phase velocity or group velocity?

- Does the group velocity vary while bouncing from one end to the other in a tapered cavity, the group velocity being faster at the big end and slower at the small end?

- Is there a travelling wave (like in a waveguide) in a microwave cavity besides a standing wave, especially when the cavity is tapered like a frustum, and when an antenna/waveguide continuously adds energy into the cavity?

- If so, can a resonant cavity with a travelling wave within can be treated as a waveguide?

- Is there such thing as a cut-off diameter in a tapered cavity?

We need those answers because the current war between proponents of opposite statements cripples the debate. Alas microwave physics seems different in free-space than in a waveguide, different in a tapered waveguide than in a constant-section waveguide and different in a cavity with a travelling wave than in a cavity with a standing wave only. And I'm not talking about evanescent waves! I even think Wikipedia is wrong on some of those claims.
« Last Edit: 07/22/2015 10:20 PM by flux_capacitor »

Offline rq3

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DIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489

A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.

Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.

Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...

Does this help? OFHC copper in all kinds of thicknesses:
http://www.mcmaster.com/#standard-red-metal-sheets/=y6269f

"Mind the Gaps" - the space between a railroad car and the passenger platform.

Offline ElizabethGreene

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Cut-off is a concept that applies to constant section waveguides.  It does not apply to tapered waveguides, as it has been remarked and shown in several peer-reviewed papers I have pointed out ...  In a tapered waveguide modes do not get cut-off, instead the modes persist, with a larger diameter region where the wave is a traveling wave to a transition region to a region near the apex where the wave becomes evanescent.

I played with this today and I believe I understand now.

In a straight waveguide energy propagates at the speed of light until the widest dimension (a) becomes shorter than the wavelength.  At this point the speed of propagation drops, slowly at first and then exponentially as a approaches half of the wavelength. Below half-wavelength, no energy propagates.

In a tapered waveguide energy will still propagate, because the light, freed by non-orthogonal axis, has far more options for rearranging to match boundary conditions within the space.

I'm taking homework to play with this some more and see how very large or and very small angles effect this relationship.  Thank you for the entertaining evening.

Offline Rodal

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@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).

I see a number of files labeled as follows:   AxialAnt-##-eXBc.csv   and   AxialAnt-##-eXSc.csv  where I suppose   ## stands for the time slice number, X stands for components x, y and z, and "B" stands for BigBase and "S" stands for SmallBase.

However, these are all Electric Field components.  I don't see any files labeled  AxialAnt-##-hXBc.csv or AxialAnt-##-hXSc.csv  with the Magnetizing H field components.  To calculate the stresses I need all 6 components: all E components and all H components.

Are the Magnetizing H field component files for the AxialAnt case somewhere and I missed them ?
« Last Edit: 07/22/2015 11:23 PM by Rodal »

Offline A_M_Swallow

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{snip}
Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...

Seems appropriate for an underground transport system.

Offline rfmwguy

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DIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489

A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.

Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.

Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...
Had to do with electric trolleys I think. Before my time.

One thing you need to be aware of in copper is that it's mixed with tin to prevent corrosion, 80-90% mix is normal and if not 99% pure copper it will cause more heating signal loss and not be as a good cavity.

Shell
PS:
I'm still waiting (have some time) for my last piece of copper is holed out to my specs, was hoping to have a simulation run,  it is 99% pure the same they use in waveguides.
Ok shell, I accept ur tease about my age...elect trolleys ;)

Actually, mind the gap is a well known sign in the london underground.

Good point on tin mix. I've got the 99% stuff on my mesh, tin mix on skeleton.

Offline rfmwguy

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{snip}
Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...

Seems appropriate for an underground transport system.
Hey, no fair, u being from england...that was a test for Yanks only ;)

Offline rq3

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DIYer head's up. Copper flashing seems to be a cost-effect solution for frustum walls if you are not using mesh. As I was looking around for supplies, found this: http://www.acehardware.com/product/index.jsp?productId=1290779&KPID=984489&kpid=984489&pla=pla_984489

A 10ft roll seems to be the smallest length. I'd recommend the 14 inch for frustum heights to 11 inches. I can say from experience that .021 thickness will not be self-supporting and an exoskeleton will be needed. When I switched to a magnetron, the 1/8 in square copper supports were not ideal. I'd move to 1/4 in copper struts or possibly tubing.

Top and bottom plates on nsf-1701 were 1/2 oz copper clad pc board, again too flimsy for a 750g magnetron. Try the next size up. Solid copper plates would weigh too much, I stick with the pcb stuff, just make sure there are plated thru-holes or plenty of bolts to connect the 2 ground planes.

Any metal above ground potential will be subject to plasma discharge, so "mind the gaps" ;)

p.s. Bonus points for anyone who knows that phrase...
Had to do with electric trolleys I think. Before my time.

One thing you need to be aware of in copper is that it's mixed with tin to prevent corrosion, 80-90% mix is normal and if not 99% pure copper it will cause more heating signal loss and not be as a good cavity.

Shell
PS:
I'm still waiting (have some time) for my last piece of copper is holed out to my specs, was hoping to have a simulation run,  it is 99% pure the same they use in waveguides.

Shell, there are hundreds of copper alloys. Copper alloyed with tin is bronze. Copper alloyed with zinc is brass (both very generically speaking). What you are probably after is the highest possible electrical conductivity, which is commercially called 101 copper, or Oxygen Free High Conductivity (OFHC) copper.

Both brass and bronze typically have drastically lower conductivity than OFHC copper. Waveguides are often brass for structural reasons (its much stiffer and harder than OFHC), and are often silver plated internally to enhance conductivity. Cheaper waveguides are usually aluminum.

McMaster Carr (mcmaster.com) is a somewhat pricey but immediately available source for OFHC. Browse under "Raw Materials". They may even have perforated sheet.

Offline aero

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@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).

I see a number of files labeled as follows:   AxialAnt-##-eXBc.csv   and   AxialAnt-##-eXSc.csv  where I suppose   ## stands for the time slice number, X stands for components x, y and z, and "B" stands for BigBase and "S" stands for SmallBase.

However, these are all Electric Field components.  I don't see any files labeled  AxialAnt-##-hXBc.csv or AxialAnt-##-hXSc.csv  with the Magnetizing H field components.  To calculate the stresses I need all 6 components: all E components and all H components.

Are the Magnetizing H field component files for the AxialAnt case somewhere and I missed them ?

I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out.

Check it again, they are there now.
Retired, working interesting problems

Offline rfmwguy

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The Space Show will have Dr. Jim Woodward on tonight.

 Tuesday, July 21, 2015; 7-8:30 PM PDT (10-11:30 PM EDT; 9-10:30 PM-1 PM CDT): We welcome DR. JJIM WOODWARD back to the show to update us on his work with a Mach effect drive impulse engine- and gravitational physics.

http://www.thespaceshow.com/

The show has archived: http://thespaceshow.com/detail.asp?q=2509
Direct link to audio: http://archived.thespaceshow.com/shows/2509-BWB-2015-07-21.mp3

Both Sonny White and Paul March were mentioned in passing, but EM Drive was not specifically discussed.

~Kirk
Listening to it as I type. Fascinating discussion about the politics of advanced propulsion techniques. Regarding his theory, seems like spooky action at a distance on steroids. Heavy lifter discussion...cart B4 horse again.

Offline Rodal

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...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out.

Check it again, they are there now.
I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero.  The stress at the big base is a central point stress from the antenna.  Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically lower amplitude.

QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?

Most important: QUESTION2: did Meep give you a Q value for this case ?

Thanks
« Last Edit: 07/23/2015 12:51 AM by Rodal »

Offline Prunesquallor

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To all those proposing to use Thruster in the name, I reiterate what rfmwguy said:

Electromagnetic Drive or Reactor seems safe, perhaps a little better than Thruster since we're not 100% sure its pushing rather than pulling.

What could the possible difference be between "pushing" and "pulling"?
Retired, yet... not

Offline aero

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...I wondered why that went quicker last night. Not quick but a little quicker. I guess you found out.

Check it again, they are there now.
I'm looking at the Yang/Shell Axial Antenna at Big Base case now: very unusual: the stress, and hence the force at the small base is practically zero.  The stress at the big base is a central point stress from the antenna.  Close inspection of this mode looks like another TM11 transverse magnetic mode but with drastically different amplitude.

QUESTION1: was the mesh kept the same as in the previous csv Yang/Shell case, and you are sure this is the stress at the small base and not outside it?

Most important: QUESTION2: did Meep give you a Q value for this case ?

Thanks

Everything about the run was identical except the antenna. The csv files are the same size aren't they? If something were changed likely they would change size. And really, the bases should be in the same place they were previously. I looked at this data set with HDFview. But note that the row numbers I gave you I had 1 added, to start at 1 like the csv matrices, instead of 0 as HDFview uses. If you also added 1, that would be the problem. The model skin is three matrix rows thick, adding an extra 1 would make the small base row be inside the skin.

It was also the same 58 mm antenna centered quarter wavelength from the inside face of the big base but rotated 90 degrees to an axial orentation. Note that 1/4 wave length is only slightly more than half of 58 mm, so the end of the antenna near the big base was about 1.5 mm away from the base, and excited with ez component although hy would have been more natural.

Q? Yea, Q was ridiculously high, like 60 million and the resonant frequency was like 2.463 GHz, which I ignored and made the run at 2.45 GHz.
Retired, working interesting problems

Offline deltaMass

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To all those proposing to use Thruster in the name, I reiterate what rfmwguy said:

Electromagnetic Drive or Reactor seems safe, perhaps a little better than Thruster since we're not 100% sure its pushing rather than pulling.

What could the possible difference be between "pushing" and "pulling"?
A sign  ;D

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