Cannae/EmDrive

[ZetaX]

Can we please not have another (fifth¿ sixth¿) round of this "discussion" that will mostly consist of "weird missunderstanding of quantum stuff" versus "the universe as we know it would break"¿

It had been done often enough in this thread, just look it up if you have a question, proposal, hypothesis or whatever; almost everything that can be said has been said. Give it a rest already until there are lots (!) of new data.

[magnemoe]

There are two different "if it works" scenarios here. If it provides thrust using some previously unseen interaction to transfer momentum, that'd merely be very bad. It'd mean we've missed something very big with the standard model.

If it actually violates conservation laws? It invalidates over 200 years of progress in physics. Needless to say SM could be just thrown into the garbage in its entirety. We'd be able to salvage Newton's laws as an approximation of typical behavior. That's about it. All of the physics following it, Lagrangian Mechanics, Classical Field Theory, Classical Electrodynamics, Thermodynamics, Relativity, Quantum Mechanics, Quantum Field Theory, Statistical Mechanics, and basically every branch of science they have spawned, rely either directly on conservation laws being true, or on symmetries that are fundamental to these conservation laws.

These are fundamental assumptions in absolutely every branch of physics. Violating them breaks everything beyond salvage.

Another major issue who might be worse is that an emdrive powered probe would at high speed gain more energy than it consumes.

it uses energy and accelerates constant, so the speed will increase linearly, however kinetic energy is mass*speed^2 so it will gain energy exponential.

Unless it has some upper speed it will gain more kinetic energy than the electrical energy you supply.

Even worse if you could put it at the end of an long rotating arm and get it to rotate fast enough you would be able to tap more energy from the machine than you supply.

[K^2]

1. The scale variation in which quantum/classical divergence operate when pushed, the virtual particle effects

2. The full ramifications of Higgs and its so-called variants.

Interaction via Higgs is just as likely as it being a weak force. There are far more plausible explanations. But either one of these would go against predictions of SM, which would go into that very bad pile.

people who have claimed the standard model is complete have been somewhat premature. For example how the higgs field propogates through space.

Same as any other gauge field? There is really nothing special about Higgs. It's just yet another gauge field for yet another gauge symmetry corresponding to yet another charge. As soon as we've confirmed that yes, that's a thing that happens, Higgs became as well understood as electroweak bosons.

Another major issue who might be worse is that an emdrive powered probe would at high speed gain more energy than it consumes.

It's not really so much another issue, as part of one big issue. You cannot break conservation of momentum without breaking conservation of energy, because they are consequences of the same symmetry. Another way to view it is through prism of relativity. Momentum conservation violation in one frame of reference is necessarily an energy conservation violation in another. So like you said, once the thing starts moving, it's extra energy it's producing, not just momentum.

And that's a big part of why it shatters things like thermodynamics and electrodynamics, where you might not have thought it matters as much. But as soon as momentum conservation is out, everything else falls to pieces.

[Scotius]

Huh...i haven't thought a metal drum filled with microwaves can have such far reaching consequences besides space travel Also, anyone else thought about 'mass effect' from the eponymous game series? That too was depicted as breaking physics 'as we knew it'.

[magnemoe]

It's not really so much another issue, as part of one big issue. You cannot break conservation of momentum without breaking conservation of energy, because they are consequences of the same symmetry. Another way to view it is through prism of relativity. Momentum conservation violation in one frame of reference is necessarily an energy conservation violation in another. So like you said, once the thing starts moving, it's extra energy it's producing, not just momentum.

And that's a big part of why it shatters things like thermodynamics and electrodynamics, where you might not have thought it matters as much. But as soon as momentum conservation is out, everything else falls to pieces.

Yes you are right, however saying creates energy from nothing sounds worse than breaking conservation of momentum.

So either its some bug or all physic is wrong. Option 2 sounds more fun

[Frozen_Heart]

Another paper has been released with test results from the EM drive. As before measuring tiny thrust and no indication of what's causing it.

[Technical Ben]

Remember, the pioneer probes was solved over a simple heat leak. Don't get too hung up on physics.

[Vaporo]

I wonder how future science classes will go if this turns out to be real.

"Ok, class. These physical law apply in all circumstances, all the time. There is no time that they do not work, and there is no way they can be broken. If you suspect something is not following these laws, check your experiment, because you will find that you are wrong. Except when you shine a magnetron into a metal barrel. Then you can just forget this entire course."

[Scotius]

Another paper has been released with test results from the EM drive. As before measuring tiny thrust and no indication of what's causing it.

How "tiny"? Because even thrust comparable to current ion engines, but requiring no fuel would be a huge thing.

[PB666]

Yes you are right, however saying creates energy from nothing sounds worse than breaking conservation of momentum.

So either its some bug or all physic is wrong. Option 2 sounds more fun

You can't get energy from nothing, but there is something everywhere, just not matter. At the quantum scale matter and energy can appear and disappear.

[Frozen_Heart]

I wonder how future science classes will go if this turns out to be real.

"Ok, class. These physical law apply in all circumstances, all the time. There is no time that they do not work, and there is no way they can be broken. If you suspect something is not following these laws, check your experiment, because you will find that you are wrong. Except when you shine a magnetron into a metal barrel. Then you can just forget this entire course."

Well that's school / college/ uni anyway. We are told every year that what we learned last year was inaccurate and this is actually how it works. :/

[Aanker]

If these physical laws are all incorrect, the biggest head scratcher will be why inventions and technology based on predictions made by those same laws work.

[Scotius]

Because Cannae\Emdrive is...magic? *cringes*

Come on, Science - explain it already.

[vger]

"Ok, class. These physical law apply in all circumstances, all the time. There is no time that they do not work, and there is no way they can be broken. If you suspect something is not following these laws, check your experiment, because you will find that you are wrong. Except when you shine a magnetron into a metal barrel. Then you can just forget this entire course."

*shrug*

Newtonian Gravity isn't accurate, but for nearly all practical applications it's "good enough."

And, did anyone find any updated newsbyte better than this link? I'm guessing these results aren't from the proposed upscaled experiment (bigger drive, bigger test chamber). http://nextbigfuture.com/2015/07/direct-thrust-measurements-of-emdrive.html

The official article is here but you have to pay for it. http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083

Edited July 26, 2015 by vger

[Ralathon]

*shrug*

Newtonian Gravity isn't accurate, but for nearly all practical applications it's "good enough."

That's because Newtonian gravity is a simplification of general relativity.

If you take GR and stay away from relativistic masses or velocities you end up with Newton.

That's not how things would work if this EM drive indeed produces reactionless thrust. It isn't "okay, we have this complex thing that simplifies to this stuff we know". Its "Okay, science says that this cloud is white but this EM drive says the cloud is purple...". They're simply not compatible.

[Kinglet]

How "tiny"? Because even thrust comparable to current ion engines, but requiring no fuel would be a huge thing.

Remember, the power levels fed into the engines are very low. If it actually works you could just attach a nuclear reactor to it.

[CptRichardson]

That's because Newtonian gravity is a simplification of general relativity.

If you take GR and stay away from relativistic masses or velocities you end up with Newton.

That's not how things would work if this EM drive indeed produces reactionless thrust. It isn't "okay, we have this complex thing that simplifies to this stuff we know". Its "Okay, science says that this cloud is white but this EM drive says the cloud is purple...". They're simply not compatible.

It probably doesn't produce reactionless thrust, and we're missing the interaction.

But we know for certain it exists now, because this guy is apparently a professional debunker who's had a lot of experience in edge-cases like this, and could only manage to validate the prediction model for the size of device he built and eliminated all the common talking-point errors people said the Eagleworks guys were making.

[notfruit]

So I've kind of been following the "discussion" here. How hard would it be to build one of these things? It's just microwaves and a bell shaped thing, so it can't be that hard right?

[SomeGuy12]

So I've kind of been following the "discussion" here. How hard would it be to build one of these things? It's just microwaves and a bell shaped thing, so it can't be that hard right?

I think building one is easy, the hard part is determining if anything is happening besides wasting electricity. You would need a design for the parts that won't overheat in a vacuum, a vacuum chamber, and some really sensitive detectors. Better make that a huge vacuum chamber, room sized or larger, so you can install the equipment on a plastic platform or suspended or something to minimize interactions with the environment. Unfortunately, that's probably what is actually happening - the device is pushing off the chamber walls or some other very ordinary interaction.

[CptRichardson]

So I've kind of been following the "discussion" here. How hard would it be to build one of these things? It's just microwaves and a bell shaped thing, so it can't be that hard right?

It would be a fincky build, for sure. It SOUNDS simple, but you'd have to be a pretty good machinist and have an idea of what you're doing with radio and microwave emitters. Scientific equipment would help a lot, but I've seen some pretty silly-simple test rigs.

[Scotius]

I think building one is easy, the hard part is determining if anything is happening besides wasting electricity. You would need a design for the parts that won't overheat in a vacuum, a vacuum chamber, and some really sensitive detectors. Better make that a huge vacuum chamber, room sized or larger, so you can install the equipment on a plastic platform or suspended or something to minimize interactions with the environment. Unfortunately, that's probably what is actually happening - the device is pushing off the chamber walls or some other very ordinary interaction.

If it would be ordinary interaction, someone would find it from the get-go. This is a part of a reason why Cannae\Emdrive is making such a stir - it's deceptively simple. Just a metal drum, some off the shelf electronics and a power source. And yet so far no one figured out how it does produce measurable and predictable thrust.

[magnemoe]

It probably doesn't produce reactionless thrust, and we're missing the interaction.

But we know for certain it exists now, because this guy is apparently a professional debunker who's had a lot of experience in edge-cases like this, and could only manage to validate the prediction model for the size of device he built and eliminated all the common talking-point errors people said the Eagleworks guys were making.

One idea who came up on another forum was if you got reflection of microwaves from the drive to the chamber and back again, this would increase the photon trust many times.

Weakness with this idea is that you would not get very many time more trust than the basis photon drive and it would be extremely dependent on placement to get much useful reflections.

[Streetwind]

So I've kind of been following the "discussion" here. How hard would it be to build one of these things? It's just microwaves and a bell shaped thing, so it can't be that hard right?

There are people building their own in the nasaspaceflight.com forum thread, you could try checking there.

The quality of discussion is also much, much higher there than in this thread.

[Scotius]

Because this forum is for mostly casual computer gamers, who happen to be interested in spaceflight On NASA page more hardcore crowd is to be expected.

[Esme]

I can well understand people being skeptical at whether the Cannae drive actually produces any thrust without using reaction mass (NB: reaction mass and fuel are not necessarily the same thing . In a chemical rocket they are the same thing, whereas in an ion engine, the reaction mass is ionised and thrown out the back - but some source of power is required to both ionise the reaction mass and charge a grid to repel it, whether that be solar power,a diesel electric generator or a lump of plutonium. )

Many thanks for whomever gave the pointer to the NASA forum,I shall have a look through it when I get back home. However, assuming that there is a valid, real efffect here; if it is so tiny, then it's unlikely to have any practical use so far as I can see (solar sails and ion engines would likely be more useful). If it's a case of it being an effect that can be amplified in some way with teh right setup, that may be more interesting. But the very fact that the effect exists (if it does) is very interesting indeed from the point of view of helping t improve our models of how the universe works,even if it doesn't have any practical use.

And if it turns out that the claimed effect doesn't actually eixst, but is an artefact caused by X (where X is some as yet unidentified bit of teh experimental setup) that's still interesting. At least the whole thing isn't obvious crank science, like yer average perpetual motion or free energy claimant.