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#720 by Bob012345 on 07 Aug, 2017 17:42
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(...) Do you think you will someday build a Cannae type device also? Anyone else here working on Cannae devices?
Great question Bob012345,
if Guido Fetta's results are em thrust then there must be longitudonal asymetry in his lobes and it would be nice to know exactly how they are arranged.
Presuming that the design idea came from a working knowlege of linear particle accelerators, somone familiar with that technology might be able to get some good results.
My question is, can a Fetta type resonator be constructed that would resonate at 60 GHz and what would the dimensions of its lobes be?
Fetta claims his device works by the Lorentz force. I'm not sure exactly how since I don't have his paper but I've been thinking a lot about how a Lorentz force might work but I'm not confident enough to say yet. Also, looking at his design for a Deep Space Probe, the device actually is stated to have an area of some 90 square meters which is huge. His pancake like structures are over 3 meter in diameter yet operate with less than 20 watts but at only 50MHz. The large size is dictated by passive cooling of the superconducting chambers.
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#721 by Monomorphic on 07 Aug, 2017 18:07
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Are you not worried the heat generated by the frustum warping the PLA scaffold?
If I were using a higher powered amp, I might be worried, but the amp I am using will top out around 25W. To preserve the amp, I plan on running tests between 2W - 20W. Test duration is usually less than one minute so I do not expect enough heat to be absorbed to cause problems due to the internal surface area (~0.28m2). PLA glass transition temp is 65C (150F). So if I can keep everything well below that temperature, there shouldn't be any warping.
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#722 by aero on 07 Aug, 2017 18:44
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Are you not worried the heat generated by the frustum warping the PLA scaffold?
If I were using a higher powered amp, I might be worried, but the amp I am using will top out around 25W. To preserve the amp, I plan on running tests between 2W - 20W. Test duration is usually less than one minute so I do not expect enough heat to be absorbed to cause problems due to the large internal surface area (~2.8m2). PLA glass transition temp is 65C (150F). So if I can keep everything well below that temperature, there shouldn't be any warping.
You should probably re-check that internal surface area calculation. ... -
#723 by Monomorphic on 07 Aug, 2017 18:53
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You should probably re-check that internal surface area calculation. ...
Whoops! Thanks aero, let me correct that. -
#724 by X_RaY on 07 Aug, 2017 19:46
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You should probably re-check that internal surface area calculation. ...
Whoops! Thanks aero, let me correct that.
James could you re quote the dimensions of your current build please.
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#725 by Monomorphic on 07 Aug, 2017 19:51
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James could you re quote the dimensions of your current build please.
small diameter: 17.8cm (36.41cm spherical radius)
height: 24cm
big diameter: 29.9cm (61.161cm spherical radius)
It's the same dimensions as the current flat end frustum, except with spherical ends. I have also listed the spherical radii. -
#726 by Monomorphic on 07 Aug, 2017 21:42
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X_Ray, attached is the STL file of the cavity interior that I used to create the 3D print files. It was created in another CAD program to get around FEKO's limitation of drawing parabolic surfaces instead of spherical ones. You can import this using the mesh import. Make sure you set the scale factor under advanced tab to .001 so it will import at the correct scale. Then you can remesh it using FEKO's mesh function by deselecting use model mesh. Then create a new mesh as usual.
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#727 by spupeng7 on 08 Aug, 2017 01:47
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Safe to say that the heat absorbed by the frustum due to energy input cannot exceed that generated by the energy input. Can we go further and subtract the energy of any thrust achieved from that figure?Are you not worried the heat generated by the frustum warping the PLA scaffold?
If I were using a higher powered amp, I might be worried, but the amp I am using will top out around 25W. To preserve the amp, I plan on running tests between 2W - 20W. Test duration is usually less than one minute so I do not expect enough heat to be absorbed to cause problems due to the internal surface area (~0.28m2). PLA glass transition temp is 65C (150F). So if I can keep everything well below that temperature, there shouldn't be any warping. -
#728 by ThinkerX on 08 Aug, 2017 02:32
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Ok, gotta ask...
will Shell and/or Stardrive be publishing any of their accumulated research soon?
Say...by years end? -
#729 by demofsky on 08 Aug, 2017 03:24
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Depends on how conservative an analysis you want to do. Since we are looking at failure modes it might be better to ignore thrust.
Safe to say that the heat absorbed by the frustum due to energy input cannot exceed that generated by the energy input. Can we go further and subtract the energy of any thrust achieved from that figure?Are you not worried the heat generated by the frustum warping the PLA scaffold?
If I were using a higher powered amp, I might be worried, but the amp I am using will top out around 25W. To preserve the amp, I plan on running tests between 2W - 20W. Test duration is usually less than one minute so I do not expect enough heat to be absorbed to cause problems due to the internal surface area (~0.28m2). PLA glass transition temp is 65C (150F). So if I can keep everything well below that temperature, there shouldn't be any warping. -
#730 by Flyby on 08 Aug, 2017 08:46
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Are you not worried the heat generated by the frustum warping the PLA scaffold?
If I were using a higher powered amp, I might be worried, but the amp I am using will top out around 25W. To preserve the amp, I plan on running tests between 2W - 20W. Test duration is usually less than one minute so I do not expect enough heat to be absorbed to cause problems due to the internal surface area (~0.28m2). PLA glass transition temp is 65C (150F). So if I can keep everything well below that temperature, there shouldn't be any warping.
Personally I would have taken PETG instead of PLA as it has a higher glass transition temp (80°C). It is just as cheap to use and has only a slightly higher printing temp compared to PLA.
ABS has an ever higher glass transition temperature, but is notorious for warping and splitting.
Through the years of experience , I've developed a distaste for using ABS. It is toxic and damn hard to get right in daily use (The splitting and warping ruined many prints destined for clients)
PETG is actually food safe and has a superior layer binding, and unlike PLA, it has a superior impact resistance. IF you accidentally drop a PLA piece, it is very likely pieces might brake off. Not so with PETG..
Apparently, PEEK is the ultimate printable material to use (glass transition at 143°C), but helas, it needs a special hot-end due to a much higher melting point. I have yet to try it...
added:
Oh, I forgot about PC (polycarbonate) filaments.... Extremely tough and with a high glass temp of 147°C.
Again, it needs a high temp hot-end (265-300°C, depending on speed) -
#731 by Monomorphic on 08 Aug, 2017 15:07
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Personally I would have taken PETG instead of PLA as it has a higher glass transition temp (80°C). It is just as cheap to use and has only a slightly higher printing temp compared to PLA.
I used PLA because a roll came with the printer.
There's a growing list of things I wish I had done, like bolt holes so I don't have to drill holes and epoxy everything together. The next version will be much more thought out. I also want to replace the Y axis bearings on the printer with something less noisy.
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#732 by spupeng7 on 09 Aug, 2017 04:32
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#733 by Bob Woods on 09 Aug, 2017 04:46
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http://emdrive.com/ is worth a look today :-)
Thanks for the link. But let's wait until real details and data is provided before we fire up the barbie.
Plans for 3G Demonstrator developing... -
#734 by Chrochne on 09 Aug, 2017 05:43
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http://emdrive.com/ is worth a look today :-)
Thanks for the link. But let's wait until real details and data is provided before we fire up the barbie.
Plans for 3G Demonstrator developing...
We know that they allow Mr. Shawyer to release very little information about any progress considering all NDA in place. It is first time ever he speaks about 3rd generation, but I think we already saw the patent few months back.
Still this is very interesting information indeed. If I find anything more about this sudden release I will post it here.
Link for patent mentioned in the presentation:
https://www.ipo.gov.uk/p-find-publication-getPDF.pdf?PatentNo=GB2537119&DocType=A&JournalNumber=6647
Can also someone elaborate on the use of Sapphire substrate? -
#735 by Flyby on 09 Aug, 2017 08:29
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there was already a discussion about that in thread 8:
http://forum.nasaspaceflight.com/index.php?topic=40959.msg1607569#msg1607569
Unless I'm mistaken, it had something to do with spahire being the ideal substrate to place a layer of YBCO on.
This configuration pops up in other experiments also, like the quantum locking experiment :
https://www.nature.com/scitable/blog/student-voices/a_closer_look_at_quantum.
added :
found out exactly why a sapphire substrate is used, in this document :
https://etd.ohiolink.edu/!etd.send_file?accession=ucin971281869&disposition=attachment
Basically, "the thermal expansion match" between sapphire and YBCO (superconducting material) is the reason to why YBCO is placed upon a sapphire substrate. Apparently, YBCO (brittle?) would crack is placed upon a material that does not have a matching thermal expansion..
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#736 by Chrochne on 09 Aug, 2017 09:57
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there was already a discussion about that in thread 8:
http://forum.nasaspaceflight.com/index.php?topic=40959.msg1607569#msg1607569
Unless I'm mistaken, it had something to do with spahire being the ideal substrate to place a layer of YBCO on.
This configuration pops up in other experiments also, like the quantum locking experiment :
https://www.nature.com/scitable/blog/student-voices/a_closer_look_at_quantum.
added :
found out exactly why a sapphire substrate is used, in this document :
https://etd.ohiolink.edu/!etd.send_file?accession=ucin971281869&disposition=attachment
Basically, "the thermal expansion match" between sapphire and YBCO (superconducting material) is the reason to why YBCO is placed upon a sapphire substrate. Apparently, YBCO (brittle?) would crack is placed upon a material that does not have a matching thermal expansion..
Interesting, basicaly he chose sapphire substrate as a material that he sees as ideal for this device.
"Besides its excellent electrical insulating properties, sapphire has high thermal conductivity. CMOS chips on sapphire are especially useful for high-power radio-frequency (RF) "
from wikipedia - https://en.wikipedia.org/wiki/Sapphire (almost to the bottom)
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#737 by Monomorphic on 09 Aug, 2017 12:28
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With a 2,400 liter tank of LH2, it won't be cheap to fill up! Best to produce the LH2 on site ($0.70/liter) vs off site ($2.20/liter). I wonder how big the battery would need to be if we eliminate the fuel cells and used a dedicated refrigeration system for cooling the emdrives.
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#738 by flux_capacitor on 09 Aug, 2017 12:42
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He'd better hire a designer for his PAV too. Why not just put the tanks (as well as three couples of EmDrives) at the vertices of an equilateral triangle:
Then you just have to modulate the power applied at each vertex to pitch and roll, thus accelerate and move forward, turn, slow down and stand still of even move backward, like a helicopter. But a totally silent one with no rotating airfoil!
*Sigh* This is still just plain science fiction. -
#739 by Flyby on 09 Aug, 2017 13:05
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My biggest problem is the proposed 1.54kN/kW...
Really ?? kilo-Newtons ?
1540 Newtons per kiloWatt?
And all this while we have yet to see a solid milli-Newton scale result ??
Not that I do not want to believe it could work, but this sure doesn't make it sound "believable"..
It rather falls in the category of "wishful thinking" instead of "engineering optimism"...
There's a growing list of things I wish I had done, like bolt holes so I don't have to drill holes and epoxy everything together. The next version will be much more thought out. I also want to replace the Y axis bearings on the printer with something less noisy.
1540 Newtons per kiloWatt?