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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all.
Looking at current efforts with high frequency (24GHz) setups got me thinking.
Could it be possible to make an EmDrive using a stack of etched double sided PCBs with the chamber made out of copper islands within them, and connected together to provide a contiguous structure? Each PCB would be spaced from the next by a thin piece of plastic so that the structure is rigid.
This would have several advantages, not least that the permeability of FR-4 is well known and by compressing or stretching out the stack the geometry of the chamber could be tuned to the Gunn diode's resonant frequency.
I know that Gunn diodes are not particularly efficient but they are relatively low cost compared to a solid state RF amplifier ($20 versus $2000+) and easily swapped out if they fail.
See
Additional wave-shaping could be accomplished by putting copper dots or other microstructures on alternating layers to encourage the formation of a standing wave within the chamber, which has an effect on Q-factor. Also worth doing is drilling small holes in the PCBs near the edges of the copper islands as this is where most of the power would be concentrated so losses here would be more critical.
I read that one problem with copper chambers is that they oxidize quite easily so coating with a thin layer of UV setting glue post etching would be advisable.
Registered Member #58215
Joined: Wed Dec 30 2015, 11:27AM
Location: Boise, Idaho
Posts: 65
Are you proposing multiple smaller EmDrives stacked on top of each other? I'm still a big skeptic of it, but checking in on results on the reddit sub and nasa forums. Hopefully someone here can answer (some guys on 4hv with the know-how doing an RF cavity thruster test would be quite cool) But in the event that they cannot, I suggest you ask your question here: <http://forum.nasaspaceflight.com/index.php?
board=73.0> Or here: <https://www.reddit.com/r/EmDrive/>
Both are filled with people who are either fanatical supporters because it is "awesome" and some scientists actually trying to test the validity.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
I don't know much about "EmDrive", but to the extent the effect is real, doesn't it depend on being able to produce very high EM field strength inside a specially shaped resonant cavity?
If that's the case, then it seems to me that you'd be plagued by the same issues that limit the accelerating gradients in high energy RF/microwave linear accelerators; i.e., field emission, multipactoring, etc.
So I would think that you'd need mechanically strong and stable, vacuum compatible, highly polished, highly conductive (or superconducting) structures, carefully designed to minimize surface electric fields.
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EmDrive improvements
