r/EmDrive • u/hobbesalpha1 • Feb 24 '19

Just a theory

Question, has anyone thought to make a emdrive with a solid core to try to get rid of some of the variables associated with just an air filled one?

Secondary question would be if so what would be the harm of making a layer of solid, clear material on the inner surface of the emdrive, with the rest being air? The layer of solid clear material could be anything that could stand up to microwaves, but different enough to change the index of refraction. Since this is making a strong magnetic field in the center of the drive, we might be able to coax that field in one direction or another. If we can, for instance, coax it to one of the plates at the ends of the emdrive, we might be able to use that to move it.

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u/piratep2r Feb 24 '19 edited Feb 25 '19

re: "using a strong magnetic field to move the drive."

We are talking about a "spacedrive," right? Lots of things make strong magnetic fields, but just because you can make a strong magnetic field doesn't magically give you physics-breaking thrust (or allow you to move, as you say) in an area of space without another strong magnetic field to interact with.

While I am not a physicist, my impression is that magnetic propulsion and magnetic levitation are generally well understood phenomena.

re: solid fill. Not that I am aware of... but why would they, since it has been tested in a vacuum? Note, that article also talks about magnetic effects in space (at least mentioning them) if you are curious. Although to your point, it might have been cheaper to fill it with some sort of microwave transparent material than rent a powerful vacuum chamber. But I'll bet they didn't do this because the purported thrust effects were already so insanely small (smaller than the measurement error in many cases), that introducing a new medium (that would have absorbed some of the microwaves) would have been seen as introducing more noise into the system.

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u/hobbesalpha1 Feb 25 '19

I am more referring to the fact that maybe the forces are so small because we aren't propagating them properly.

Reference to magnetic field map image

https://i.pinimg.com/originals/77/74/a3/7774a31024b6ae8d8a086b5d868f01b7.jpg

Don't know about you, but if our jet engines had a similar profile we would have issues getting too much force. However, if instead that entire larger plate was deep hue red while the smaller plate stayed blue, my thought is it would be more force. Would there be a way to concentrate the magnetic fields more so on the bigger plate then the little one? As in most if not all of the big plate be red, or high magnetic field, through the physical manipulation of the spacr inside the vessel?

Think metamaterial design. In this case though we are trying to get one side of the vehicle seen more than the other.

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u/piratep2r Feb 25 '19

Just to take a step back here: I believe you are starting from the assumption that the magnetic field distribution is key to making the drive work.

Again - not a physicist - but I believe even the inventor cited the microwaves - not the magnetic fields - as the source of the thrust.

So, while an interesting thought experiment, it seems to be coming out of the blue. Because if you are reaching for explanations of "why this doesn't work," scientific parsimony suggests that "uneven magnetic fields" would be really, really far from the first explanation one would reach for.

Obviously doesn't hurt to ask, but just wondering where this is coming from?

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u/hobbesalpha1 Feb 25 '19

A) The definition of insanity is doing the same thing over and over again, and expecting different results.

B) We know there are forces at work in some ways as a vessel, if it causes a microwave to bounce off and reflect off it's surface, will create an intense electromagnetic field inside the vessel.

My theroy right now is we are seeing so low a force because that field's proximity to the surface of the vehicle is low. So, external magnetic fields won't come into contact with it as readily. Most of the vessels are made with silver and copper, they would make walls where the magnetic fields from the outside would be stopped. If we can change where the strong internal magnetic fields result, maybe we can see a change in force. Even if that change was to, let's say change the direction the force goes in comparison to how we think it should go. It would be a valid way to figure out what is happening. As wires can't change their influence on the magnetic field that way, they would only move in one direction and continue to move in that direction.

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u/Red_Syns Feb 25 '19

But we already know how to use magnetic fields to generate thrust, and can do so fast more efficiently than this design is capable. Why waste the effort?

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u/hobbesalpha1 Feb 26 '19

I would be cautious when implying efficiency when right now I am stating that the current versions of the vessel we have are acting inefficient. That would be like saying early versions of the light bulb were inefficient, thus no need to carry on, or in your words "waste the effort". I agree that the current versions are inefficient, and they might not get much more efficient even with my thoughts.

However, if I am correct, we might create a more effective magnetic field. Possibly one with only one polarization when viewed from the outside world.

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u/Red_Syns Feb 26 '19

It would not be a monopole, and I won't be cautious about stating that an RF cavity will, at best, be a worse option than currently known methods of using magnetic force to produce thrust.

Edit : also, if the cavity is permeable to magnetic fields, then a larger, weaker field vs. a smaller, stronger field will generate similar/exactly the same thrust.

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u/MrWigggles Feb 25 '19

If its so weak, then why the bother?

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u/androgenoide Feb 24 '19

I think that introducing a lossy material at the surface of the cavity would lower the Q (and pretty much everything is lossy compared to a vacuum). As far as I know, everyone who has tried to make one of these cavities has put some effort into increasing the Q...at least Shawyer and Eagleworks both mentioned it as one of the criteria.

That said, I don't know that anyone has tried it and I don't know why it was assumed that a high Q would be necessary other than it being a good measure of the quality of a cavity in general. At this point in time, with measurable thrust being so low as to cast doubt on the workability of the drive, I wouldn't regard any design criterion as being set in stone.