Author Topic: Multiple EMDrive Cavities?  (Read 4565 times)

Offline CoryG

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Multiple EMDrive Cavities?
« on: 09/05/2016 08:15 PM »
I'm curious if anyone has tried the EMDrive with multiple cavities with a higher frequency compared to a single cavity at the same power level.  My rationale here is that the effect may be based in part on the spatial distribution of the waves inside a cavity and multiple smaller cavities covering the same volume with the same input power may yield more thrust.

On a related note, is there any information available relating frequency to the ideal cavity dimensions?

Offline Willem Staal

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Re: Multiple EMDrive Cavities?
« Reply #1 on: 09/07/2016 09:06 AM »
I was thinking about multible cavities too. Or even a fractal shaped cavity.  The problem is that you need also multiple rf units or a system to direct the waves into the other frustrums.  I think that there is more gain possible with a better way to push the waves in the frustrum.  (maybe a fractal transmitter?)

Offline JohnFornaro

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Re: Multiple EMDrive Cavities?
« Reply #2 on: 09/18/2016 02:49 PM »
Only way to scale up the technique, it would appear.
Sometimes I just flat out don't get it.

Offline LowerAtmosphere

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Re: Multiple EMDrive Cavities?
« Reply #3 on: 12/30/2016 11:51 PM »
This design idea is interesting and it is curious whether further progress in multi-cavity drives has taken place recently. The question remains how resonance would be achieved in each cavity; would this be a question of designing some sort of geometrical minmax based approximation algorithm trying to identify the optimum gradient? Perhaps let the walls in the consecutive cavities be independent variables and let a strong computer crunch away at permutations and curvatures while using FEKO or the likes.

Also completely neglected in the discussion is a rather fundamental question: why should the cavities be stacked in a straight line? Most theories agree - using vague terms since I'm not here to rehash emdrive.wiki or pass judgment as to the veracity of a particular theory - that the photonic energy gradient may be maintained in asymmetrical cavities. This gradient ignores wall shape, though mode and resonance of EM waves do not!

Small disclaimer for the pedants: scratches, discontinuities, folds, segments below cut-off and various other shapes will affect many different physical effects, I am generalizing here as the assumption remains that the majority of the significantly dense E/H fields will occur within the more central volume of the cavity depending on mode.

A "rose", "matryoshka", "beehive", or any other imaginable linked cavity network may perform the same work given the correct input frequency, material and configuration. A Cannae style device, or even Gallinat's trumpet, may be easy to manufacture, but is guaranteed to be suboptimal. It is never too early to look for ways to improve the design ignoring dogmatic single cavity thinking. If the Chinese patents are any indication, someone has definitely gone down this train of thought before for a logical reason.

Offline arachnitect

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Re: Multiple EMDrive Cavities?
« Reply #4 on: 12/31/2016 12:18 AM »
Excellent idea.

Step 1: two EM drive cavities attached back to back "thrusting" (or whatever the right verb is) in opposite directions

Step 2: is net thrust detected? Is it on the same order of magnitude as originally observed EM drive effects?

Step 3: reconsider hypotheses in light of test results.

Offline sanman

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Re: Multiple EMDrive Cavities?
« Reply #5 on: 01/01/2017 02:12 AM »
A "rose", "matryoshka", "beehive", or any other imaginable linked cavity network may perform the same work given the correct input frequency, material and configuration. A Cannae style device, or even Gallinat's trumpet, may be easy to manufacture, but is guaranteed to be suboptimal. It is never too early to look for ways to improve the design ignoring dogmatic single cavity thinking. If the Chinese patents are any indication, someone has definitely gone down this train of thought before for a logical reason.

I assume you meant "honeycomb" rather than "beehive" - but in such a "linked cavity network" as you mention, surely the cavities would all have to be aligned to produce net thrust - correct?

Nextly, what exactly do you mean by "linked", and why is this required?

I hate to throw up a cliche - but couldn't a 3D printer intricately print a bulk material consisting of many little frustrum cavities? But I suppose it would have to print in copper metal, unless you want to do it in plastic and then electroplate it with copper.

If 3D printers can be used to print optical waveguide materials, then isn't a bulk material consisting of many-little-frustrums a specific special case of such waveguide materials?

For instance, there are various examples of waveguide materials whose feature sizes are quite small:

http://phys.org/news/2015-10-d-microwave-circuits.html
http://mwca.ece.arizona.edu/researchAreas/three_D_printing.htm
http://www.optisys.tech/rf-faq


If your cell size (frustrum size) is on the order of microns, then you'd probably be using infrared or terahertz frequency, right?

How small can one go without losing the required defining features for working frustrums?
« Last Edit: 01/01/2017 02:14 AM by sanman »

Offline LowerAtmosphere

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Re: Multiple EMDrive Cavities?
« Reply #6 on: 01/01/2017 04:54 AM »
Honeycomb is exactly what I was getting at. See attached picture for my old example.

Alignment in the same orientation is not necessary. Consider the case of frustum designs which have such a radiation pressure gradient but not purely along the length axis of the cavity. A bent cone or hyperbolic paraboloid/saddle comes to mind. So, yes: the gradient(s) must be aligned but not necessarily the shapes.

Linked could imply that degraded wavelengths are recycled between cavities or simply that the cavities are physically connected. It is important because otherwise you are dealing with multiple single cavities essentially. Multiple cavities allow for aggregate thrust, but linked cavities offer the potential for recycling as EM waves redshift and degrade while also offering the possibility for more gain if you were to inject additional energy/varying gain medium etc. Lots of exotic effects such as vapour shockwaves (liquid drop nuclear reactors attached, I hope it is the right pdf) may also be mixed into such a complex design.

The wavelength can be terahertz sure, yet it is wise to consider degradation, splatter and general noise which could be recycled if you have stacks or bandpass filters between frustums.

You can go to CNT level frustums if you watch the input power as thermal warping can lead to pretty severe problems for the smaller and therefore fragile designs.

Smaller frustums do mean less thrust (???) and their only promise are more economies of scale and recycling.

P.S. Happy new year everybody :)

Offline ThinkerX

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Re: Multiple EMDrive Cavities?
« Reply #7 on: 01/01/2017 07:26 AM »
Way back along about the third or fourth main EM Drive thread, there were a few posts from a person who claimed to be with a company investigating 'stacked' EM Drive Units.  I recollect one quick mention that the experiment did not work out.  Then most of that persons posts vanished. 

Make of that what you will.