Cannae/EmDrive

[sal_vager]

I thought NASA verifying it works was enough, it works in a vacuum.

1 May 2015 7:30 pm

New tests show that NASA's EMDrive produces thrust in a vacuum

A group at NASA’s Johnson Space Center has successfully tested an electromagnetic (EM) propulsion drive in a vacuum

How it works will come later.

[Bill Phil]

I thought NASA verifying it works was enough, it works in a vacuum.

How it works will come later.

It at least works, which means it's beyond hope when it comes to having great propulsion in space. The only question is how?

If it does lose reaction mass over time, it's still an improvement over every other type of engine ever.

Neat.

[crazyewok]

I thought NASA verifying it works was enough, it works in a vacuum.

How it works will come later.

so modding a engine with unlimited DV wont be cheating now in KSP ?

[vger]

Funny you should phrase it that way, because if we find out that it is true, we will at the same time gain understanding of it. Hoping that the EMDrive is real is a wish for the ability to understand more of the universe.

I, for one, have a theory of the universe that allows for such a thing to happen without implying any sort of instability, but I'm going to have rocks tossed at me here if I try to elaborate.

I think I too have had that theory hypothesis)...

Not per se... This could be a very specific affect occurring under very specific circumstances. This would mean that our understanding would be off only in these circumstances.

We have 'laws' that are now inaccurate, but still good enough to still be used for nearly all conventional activities.

Gravity was once a simple rule that what goes up, must come back down, and that it always comes down at 9.8m/s/s. Then we discovered this is not a constant as we moved away from the Earth and looked at the bigger picture.

If the drive is real, it doesn't mean the universe is broken. It just means that our current laws do not cover the bigger picture. String theory suggests there may be up to 26 dimensions. Whether that's true or not, we can only perceive three... maybe four of them. Our current ideas about the universe leave room for a LOT of uncharted territory.

Aside from concerns about this being a possible harbinger of "Doomsday," is there any OTHER reason that anyone has for hoping this isn't real?

Edited May 3, 2015 by vger

[Rakaydos]

Looking for ways that EM Drive might be violating conservation of momentum is a waste of time. It's like spending your entire pay check on lottery tickets. Sure, if you win, it's going to be all kinds of beneficial. But you aren't going to. Not in any likely scenario.

What about ways it might be propellantless without breaking conservation of momentum?

http://physics.stackexchange.com/questions/46180/can-a-deformable-object-swim-in-curved-space-time

Might a microvave resonator with a shifting energy density perform the same "swimming" effect in earth's curved spacetime?

[sal_vager]

If it's really warping space like some people have suggested, the thrust could be a byproduct.

[Frozen_Heart]

If it really is warping space then it could be acting as one half of an Alcubierre drive. It bends space one way of so can move.

[Three1415]

While K^2 may be moving into zealotry territory, I do agree with his assessment that it is fantastically unlikely that the EmDrive is somehow violating conservation of momentum, which so far has been upheld in every other physical process we as a species have ever observed. Returning to that Arthur C. Clarke quote, we have only eliminated the more likely possibilities (that thrust measurements are a result of fraud or experimental error), and so are now moving on to the less likely ones (i.e, the EmDrive is somehow generating negative energy or using that vacuum as reaction mass); breaking conservation of momentum is the least likely, so that shall be settled upon only when no other possibilities still exist.

Personally, I think the EmDrive is producing (comparatively) large quantities of negative energy, as that would explain much of what has been observed in its operation--lack of apparent reaction mass, preliminary findings as to space-time warping, etc. Negative energy/matter, if properly controlled, basically allows one to gimmick one's way around more or less every physical law without actually violating them, so I very much hope we have found a good way to generate it, or at least, if the EmDrive works by some other means, have an infinite specific impulse thruster.

[Nuke]

i dont think isp can ever be infinite (i want to say c is the limit but im not sure, too lazy to math). you are still going to be limited to the life/fuel of your power supply. fission and fusion reactors are going to be running out of fuel eventually. if you are using solar then the sun is your reactor and that too will run out of fuel. you are going to have a considerably higher isp than any engine currently available, but it wont be infinite.

[Scotius]

Unless we manage to harness infamous Zero Point Energy

https://en.wikipedia.org/wiki/Zero-point_energy

[vger]

i dont think isp can ever be infinite (i want to say c is the limit but im not sure, too lazy to math). you are still going to be limited to the life/fuel of your power supply. fission and fusion reactors are going to be running out of fuel eventually. if you are using solar then the sun is your reactor and that too will run out of fuel. you are going to have a considerably higher isp than any engine currently available, but it wont be infinite.

For all practicality, if it needs nothing but sunlight to run, it's infinite. We can start complaining that it's not good enough when we start having ten-billion-year lifespans.

[K^2]

i dont think isp can ever be infinite (i want to say c is the limit but im not sure, too lazy to math).

Ayup. Photon drive is the most effective a reaction drive can be, giving you effective I_SP of c. But relativistic rocket formula is tricky if your velocity changes significantly.

What about ways it might be propellantless without breaking conservation of momentum?

http://physics.stackexchange.com/questions/46180/can-a-deformable-object-swim-in-curved-space-time

Might a microvave resonator with a shifting energy density perform the same "swimming" effect in earth's curved spacetime?

In general geometry, sure. But Earth results in almost perfect Schwarzschild geometry, which isn't usable for this. And while there are gradients you could probably grab onto, they are absolutely miniscule. You'd need a much larger system to produce far less thrust than is reported.

In the end, momentum still needs to be transferred to something. If you are using space-time curvature to push from, you are effectively using gravity of the planet bellow you to transfer momentum to it. You don't need General Relativity to understand how it works or how weak the effect is going to be for Earth. You only other options are to have propellant. If you don't bring any mass with you, or don't have medium to push from, best you can do is aforementioned photon drive.

If it really is warping space then it could be acting as one half of an Alcubierre drive. It bends space one way of so can move.

A warp drive still can't produce thrust in vacuum. It can move an object, but not generate a force against it. This goes back to conservation of momentum and the notion above about propellant.

Now, could the system be generating a weak warp field that simply deflects nearby matter? Sure. But it's very unlikely that we are generating a strong enough warp field here to account for that much thrust. It would be very obvious.

So it still leaves us with two plausible explanations. Either the drive produces exhaust, or it interacts with medium. I'm still betting on the former, because it's been reported that resonance chambers with perfect vacuum did not work as well. A piece of polymer in the chamber, which is known to evaporate under test conditions, gives much higher "thrust". So it's still very likely that the thing simply manages to work like an ion drive. If it's managing to produce thrust from interaction with environment, on the other hand, there might be some interesting applications to the system. It's worth looking into.

Personally, I think the EmDrive is producing (comparatively) large quantities of negative energy, as that would explain much of what has been observed in its operation--lack of apparent reaction mass, preliminary findings as to space-time warping, etc.

You have absolutely no idea what you are talking about. The words "negative energy" can be replaced with "pixie dust" in your sentence with no change to the meaning.

[vger]

You have absolutely no idea what you are talking about. The words "negative energy" can be replaced with "pixie dust" in your sentence with no change to the meaning.

While I agree with this statement, I also think this might be why the very idea of this thing "working" irks a lot of people. At the moment, it's boderline magic. And while Scientists are excited, it seems like Atheists hate it and can't wait to see it fail based on the article comments I've been seeing.

[SargeRho]

What does Atheism have to do with a drive that seemingly works for no apparent reason?

[vger]

What does Atheism have to do with a drive that seemingly works for no apparent reason?

It doesn't have anything to do with it. But zealotry doesn't care about that. The simple possibility of something that in layman's terms is a freaking miracle, is apparently enough to ruffle a lot of feathers.

[K^2]

Tail wags the dog. Critical thinkers tend to be atheists. Critical thinkers don't expect miracles. They know what the odds are that this is new physics, vs just a very weird application of well-known science.

And to be clear, a lot of people criticizing this thing are very far from being laymen. I have over a decade of academia to back me up. And what actually annoys me is not whether or not this thing works, but how people with absolutely zero knowledge in any relevant field jump in and start arguing the "you can't possibly know," angle.

[vger]

zero knowledge in any relevant field jump in and start arguing the "you can't possibly know," angle.

Except that this is exactly the case. You CAN'T possibly know. And it doesn't take someone who is an expert in the field to know that. Of course the odds are low, but this would hardly be the first time that there has been a game changer, and it wouldn't be the last time either.

And again, exactly why I think this is irking so many people. Because "you can't possibly know" is exactly the same argument that is often applied to another... thing... that will not be discussed in depth here for obvious reasons.

What's sad is I think the LACK of these kinds of things is what makes it so hard to get people interested in science these days. The bar is SO HIGH now that you need to be richer than Midas (through grants), AND smarter than Hawking to get anywhere now. It's a far cry from the days when you could just accidentally spill a couple of things in your kitchen, see a cool reaction, and stumble upon something that nobody ever knew before. People like to experiment. The trouble is we can't do it in our garage anymore and expect something amazing and new to happen. This EM Drive fluke reminds me of that "wow, what the heck just happened?!" kind of feeling that I used to get as a kid when experimenting with random stuff, when I didn't know that everything I could possibly figure out on my own without two or more degrees, had already been figured out decades or centuries before me.

Edited May 4, 2015 by vger

[Aanker]

So let's keep experimenting to see what's really going on and let's keep trying to find flaws in the same experiments to exclude systematic errors. Basically what's going on right now.

[K^2]

Except that this is exactly the case. You CAN'T possibly know. And it doesn't take someone who is an expert in the field to know that. Of course the odds are low, but this would hardly be the first time that there has been a game changer, and it wouldn't be the last time either.

Again, same argument. Do you know the history behind the "game changers"? Do you understand why conservation laws are different? Do you know why they are fundamental? Any of this? Then what in the world gives you the idea that you have a better idea about how likely it is than somebody who has spent a decade or longer actually studying these things?

We have knowledge necessary to gauge how unlikely this is. It's absurdly unlikely. It would be a waste of time trying to verify these things. Not to mention that it's practically a problem of proving the negative.

Any hypothesis of EM Drive's operation that assumes violation of the conservation laws is false by any practical measure. We do not need to investigate these. And if you'd like to spend a decade of your life and actually learn some field theory, we can have a discussion about the specific reasons. But by then, you'll probably already understand.

[vger]

Again, same argument. Do you know the history behind the "game changers"? Do you understand why conservation laws are different? Do you know why they are fundamental? Any of this? Then what in the world gives you the idea that you have a better idea about how likely it is than somebody who has spent a decade or longer actually studying these things?

Well gee, guess I was wrong. There ARE gods in Science.

But since you asked: what is your definition of "violating a law?"

Would you say, for example, that a warp field would be a violation of relativity? For my money, that's the kind of thing I think is happening. I wouldn't say that's the same as violating a law though.

Even if it did, it's not going to make conservation laws obsolete. They'll still be fine for nearly all practical applications. Newton is still universal, even in space, even though technically it's not completely accurate.

Edited May 4, 2015 by vger

[K^2]

Lets see, does Warp Drive violate local Poincare symmetry? No. Actually, it's the consequence of it. So Warp Drive works because momentum is conserved.

If you'd actually studied field theory and relativity, you'd know these things. And you'd be able to tell what is and is not a violation. This isn't something people just make up. There are firm, mathematical definitions for absolutely all of it.

Of course, it's much easier for you just to use your ignorance as cover and pretend that everyone else is just as ignorant. How's that working out?

[Scotius]

Gentlemen...chill the heck down No one is implying Emdrive is some sort of magical, unicorn-in-a-box propulsion system spewing fairy dust out of its rectum. It may be virtual particles, negative energy or minuscule warp bubble bending the space around itself - but i bet the explanation WILL be physical, not metaphysical. It may be just something new. Something we did not observed yet. Like infrared light was for Hershel when he started tinkering with prisms. I'm pretty sure he was as baffled as we are now, when his thermometer began registering a rise in temperature out of, well - seemingly nothing.

So please, do not start throwing personal insults around. Or do it using private messages. Some of us want to follow this interesting, potentially historical discovery without having to slog through three pages of back-and-forth rant about perceived ignorance and\or zealotry.

[Albert VDS]

What ever the results of testing this thing out gets, it's still better than almost anything else humans keep them selfs busy with.

[K^2]

No one is implying Emdrive is some sort of magical, unicorn-in-a-box propulsion system spewing fairy dust out of its rectum. It may be virtual particles, negative energy or minuscule warp bubble bending the space around itself

All of which is equivalent to unicorn-in-a-box. EM Drive is reported to produce a force. That means there has to be a stress-energy current leaving the thing. That means either a) Massive exhaust, or Environment to push from.

Why can't vacuum be suitable environment to push from? Because it'd need to have quite a bit of mass. Now, vacuum might be massive, but we'd detect that much mass long time ago.

Why can't it be virtual particle exhaust? Because somewhere down stream you must have massive particles carrying away the current. Virtual particles can't propagate out to infinity. Energy required to create massive particles downstream would be enormous. Far greater than energy consumption of EM Drive.

Every other "explanation" falls onto some combination of the above. This leaves us with just two possibilities.

a) There is massive environment besides vacuum, such as residual atmosphere, that the craft pushes from.

and/or

It's leaking something.

In other words, it acts either like a normal rocket or a normal jet engine in terms of how it interacts with reaction mass. Either one can still be useful, because everything points to it being damn efficient. But it still uses reaction mass. So it will either need a supply that it can run out of, or it can only operate in LEO. Making it just an efficient ion drive.

[Technical Ben]

It's probably just making a magnetic field and pushing off the walls of the metal structure in the building or the table legs.