Test Suggests NASA's Impossible EM Drive Will Work In Space

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Jub » 2015-05-04 05:18am

Darmalus wrote:
jwl wrote:
Terralthra wrote:Reactionless drives would be awesome, in that it would allow small craft built by amateurs to destroy cities.

....How does that work?

You assume said armature spacecraft has an unlimited power source (solar?) and time to build up to city-smashing velocities and a unobstructed orbit to do this in.


It could be possible if rather unlikely and difficult.

You could launch said craft via some combination of a balloon designed for high altitude flight and then a simple chemical rocket to push it into orbit. From there if you can figure out how to track it and can do the calculations getting it into an orbit and out to the moon. Once it's there, it can build up speed without having much chance of being spotted isn't going to be impossible. Once it has the required speed, you'll need to do the very serious math required to get it back to Earth. Keep in mind that this has to be done in such a way that it doesn't skip off the atmosphere and that it manages to get within a hundred miles of your intended target.

The other issue, of course, is going to be getting any significant mass to survive reentry to impact or airburst at a level that may do damage to anything on the ground.

This makes such a weapon the kind of thing that only state-level actors would be able to pull off. If they do, it's still more complicated and less likely to deal damage than a nuke.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Terralthra » 2015-05-04 05:52am

Nukes take significant infrastructure of enriching and refining fissile materials. So far as I know, this does not. And yes, it will take serious math, like I could do on my computer. Orbital mechanics are very well understood; there are games built around them. As for surviving re-entry, paradoxically, that's only a problem at low speeds (astronomically speaking). When something goes fast enough, the speed with which it enters the atmosphere turns it into a fusion bomb no matter what it's made of, as it will smack into the atmosphere fast enough that oxygen and nitrogen molecules will fuse as it strikes them, not slowing it appreciably before it strikes something a lot more solid.

As for unobstructed orbit...space is pretty empty. That's why it's called...space.

This is the well-known limitation of scifi involving reactionless drives: anything that sidesteps the Tyranny of Tsiolkovsky is practically by definition a potential weapon of mass destruction.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby LaCroix » 2015-05-04 07:22am

Simon_Jester wrote:The thing is, if there's one shape that makes it work well, there would generally (as in, this is true in most other kinds of physical phenomena) be other shapes that work less well. The odds of no one ever accidentally stumbling on one of them.


To be honest, our kw rated EM emitters are usually either mounted within a couple tons of vehicle, or a sturdy antenna, probably braced by cables, and able to withstand storms.

Even if someone used that perfects shape/configuration/whatever before in one of those systems, I don't think that forces less than 1N would ever be noticable there.
Figuratively, 720 mN is like someone leaned a book against the object. Even for a civil radio setup just standing on your desk, that won't even beat friction, and certainly won't make it slide or wiggle.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-05-04 07:56am

Jub wrote:It could be possible if rather unlikely and difficult.

You could launch said craft via some combination of a balloon designed for high altitude flight and then a simple chemical rocket to push it into orbit. From there if you can figure out how to track it and can do the calculations getting it into an orbit and out to the moon. Once it's there, it can build up speed without having much chance of being spotted isn't going to be impossible. Once it has the required speed, you'll need to do the very serious math required to get it back to Earth. Keep in mind that this has to be done in such a way that it doesn't skip off the atmosphere and that it manages to get within a hundred miles of your intended target.

The other issue, of course, is going to be getting any significant mass to survive reentry to impact or airburst at a level that may do damage to anything on the ground.

This makes such a weapon the kind of thing that only state-level actors would be able to pull off. If they do, it's still more complicated and less likely to deal damage than a nuke.

Okay, first of all, how is this any different to ion drives or photon rockets or whatever?

Next, how many many amateurs have built something that goes in orbit? As far as I am aware, the answer is "none". Satellite companies are not amateurs.

Finally, from what it sounds like, 2500W is apparently the right range of power accessible by solar panels. Under this, it will take at least 63e12/(2500*60*60*24*365) = 800 years for it to reach the energy of Hiroshima. So presumably this amateur will need to build a computer that can handle the situation automatically 800 or more years in the future, and they will need to be able to fit this onto the satellite, because there's no way a radio transmitter on earth sending instructions isn't going to be discovered in 800 years. And that's assuming the city it is aiming at is even still around bin 800 years time. It could be just an interesting archaeological site by then.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Guardsman Bass » 2015-05-04 10:47am

There's a pretty good article on it by Ethan Siegel over at Forbes.

So let me ask you this, aspiring (or armchair) scientists: what would be the criteria you’d demand as the extraordinary evidence necessary to convince you that this is real? For myself, here’s what I’d demand at minimum:

  • A detection of thrust that scaled with input power: the greater the power, the greater the thrust, in a predictable relationship.
  • A thrust that was at least many standard deviations above the measurement error.
  • An isolated environment, where atmospheric, gravitational and electromagnetic effects were all removed.
  • A reproducible setup and a transparent device design, so that other, independent teams can further test and validate the device/investigate the mechanism.
  • And finally, a detailed results report with the submission of an accompanying paper to peer review, and acceptance by the journal in question.

I think that’s reasonable, and hardly too much to ask. What we’ve got, unfortunately, doesn’t meet most of these criteria at all.

Let’s see what we have as respects these five points, above.

  • What we have is — for the three different “drives” from the three different teams — three different thrusts all created at different (inconsistent) power inputs.
  • For the EM Drive, the one in question here, thrust comes in consistently at between 30-and-50 microNewtons, where the limit of the measuring device is 10-to-15 microNewtons. In other words, we’re seeing results only a few standard deviations above the measurement error.
  • Previously, it was tested only in one orientation under atmospheric pressure. The new test was performed in a good vacuum (about a billionth of an atmosphere), and in many different orientations, presumably to rule out interactions with the Earth’s magnetic field and also to rule out thermal interactions with the surrounding air. 50 microNewtons may be a small number — about the weight of a half-formed snowflake — but it’s plausibly extremely significant, since the claimed results are orientation-independent.
  • The device simply exists and is in the hands of NASA Eagleworks, where engineer Paul March is performing further tests after initial tests by Sonny White, but so far, there is just the one team testing the one device.
  • And finally, there is no peer review of this device, its setup or its results; these are merely results from conference presentations.

On the one hand you have the “optimistic” group claiming that we’ve broken the old laws of physics, we can scale up and use this technology as a new method of space propulsion, and that marginally positive results (i.e., consistent with both positive and null results) from placing a Michelson interferometer indicate that we may be either distorting space (i.e., creating a “warp field”) or causing light to go faster than c, or the speed-of-light in a vacuum, by approximately 10^-18 m/s. If you listen to this group, we’ll have humans on Mars in less than three months once this technology is put into practice.

On the other hand, it’s possible that this is sloppy research (it hasn’t been peer reviewed) by a team of people highly motivated to get a positive result (Harold “Sonny” White at NASA, the primary person who worked on this, is notorious for making extraordinary claims about warp drive and fictitious physics) and eager to jump to unwarranted, fantastic conclusions. This latter possibility should be the default position of any onlooker, at least until the device is tested in such a way that it clears all five of the basic hurdles we set forth to validate this claim. The possibility that this is merely a device doing absolutely nothing new under the Sun is too great, and one that we need to definitively rule out before proceeding further.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Simon_Jester » 2015-05-04 11:09am

Terralthra wrote:Nukes take significant infrastructure of enriching and refining fissile materials. So far as I know, this does not.
On the other hand, getting a high-speed impactor like this to do city-busting damage may not require fissiles, but it DOES require you to be able to design and build a reentry vehicle and a deep space tracking network to monitor the movements of your high-speed impactors as they build up velocity. It may be easier than enriching uranium but it's not a LOT easier.

And yes, it will take serious math, like I could do on my computer. Orbital mechanics are very well understood; there are games built around them. As for surviving re-entry, paradoxically, that's only a problem at low speeds (astronomically speaking). When something goes fast enough, the speed with which it enters the atmosphere turns it into a fusion bomb no matter what it's made of, as it will smack into the atmosphere fast enough that oxygen and nitrogen molecules will fuse as it strikes them, not slowing it appreciably before it strikes something a lot more solid.
What is the critical velocity threshold required for this to happen?

I suspect that velocities high enough to ignore the atmosphere outright, AND to not simply have the projectile go 'splat' and form a high-altitude fireball similar to a nuclear airburst, are ALSO so high that you're not going to be able to attain such accelerations without a very long, laborious, looping buildup trajectory. In which case this weapon does strictly work, but you have to launch it long before impact. An enemy with conventional or nuclear weapons might well be able to intervene and "pre-taliate" before your high-speed impactors reach their targets.

As for unobstructed orbit...space is pretty empty. That's why it's called...space.
Ah, but if your projectile gets far enough out from Earth, determining its exact position becomes a problem. There is a very large risk that you will simply miss your target and accidentally blow up the wrong patch of land, if you do not have the means to track and monitor your projectiles in deep space as they build up speed.

This is the well-known limitation of scifi involving reactionless drives: anything that sidesteps the Tyranny of Tsiolkovsky is practically by definition a potential weapon of mass destruction.
This is true, but the electric-reactionless drive as described is a pretty constrained and limited example of the principle. A Weberverse impeller wedge it ain't.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Irbis » 2015-05-05 08:05pm

Simon_Jester wrote:Well frankly, it's conceivable but it's just not that likely a priori, especially since we have LITERALLY not observed a single inexplicable phenomenon related to electromagnetism in the past half century or so. It seems pretty well understood by now.

Um, high temperature superconductors were discovered less than 30 years ago. Until someone decided to bang some lanthanum-yttrium-oxygen crystals together, conventional superconductivity theory forbade it existing at temperatures above about 30 K. IIRC the question how exactly high temperature superconductors work is still an unsolved problem and instant Nobel prize for first team to figure it out.

Your points do make sense and scepticism is sold response, but still, when you remember one Nobel prize for rewriting understanding of matter was result of authoritarian powers demanding marble, not wooden tables in university labs, well...

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby K. A. Pital » 2015-05-06 04:58am

This plausible discovery breaks so much of our understanding of physics. Were it true, there would be lots of questions as to what makes this possible. Interestingly enough, launching nuclear reactors into space is not super-expensive. We routinely did that in the 1970s.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-05-06 06:08am

Irbis wrote:
Simon_Jester wrote:Well frankly, it's conceivable but it's just not that likely a priori, especially since we have LITERALLY not observed a single inexplicable phenomenon related to electromagnetism in the past half century or so. It seems pretty well understood by now.

Um, high temperature superconductors were discovered less than 30 years ago. Until someone decided to bang some lanthanum-yttrium-oxygen crystals together, conventional superconductivity theory forbade it existing at temperatures above about 30 K. IIRC the question how exactly high temperature superconductors work is still an unsolved problem and instant Nobel prize for first team to figure it out.

Your points do make sense and scepticism is sold response, but still, when you remember one Nobel prize for rewriting understanding of matter was result of authoritarian powers demanding marble, not wooden tables in university labs, well...

High-temperature superconductors aren't really all about maxwell's equations though, it's more solid state physics. Sure, it involves electricity and magnetism, but so does almost every thing ever, so by that you could also cite things like the hydrophobic force.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Simon_Jester » 2015-05-06 02:18pm

Irbis wrote:
Simon_Jester wrote:Well frankly, it's conceivable but it's just not that likely a priori, especially since we have LITERALLY not observed a single inexplicable phenomenon related to electromagnetism in the past half century or so. It seems pretty well understood by now.

Um, high temperature superconductors were discovered less than 30 years ago. Until someone decided to bang some lanthanum-yttrium-oxygen crystals together, conventional superconductivity theory forbade it existing at temperatures above about 30 K. IIRC the question how exactly high temperature superconductors work is still an unsolved problem and instant Nobel prize for first team to figure it out.
High temperature superconductivity isn't just about electromagnetism; it's a condensed-matter physics issue where the behavior of very large numbers of particles under quantum mechanics dominates the situation.

This reactionless drive, on the other hand, is about quantum electrodynamics in a complete vacuum, which is a much better understood and "no surprises in half a century" field.

It's not that surprises are categorically impossible, it's that this isn't the first and probably not the tenth time someone has proposed a reactionless drive that runs on quantum woo, using a technobabble explanation that makes about as much sense as saying that your car engine runs by pulling itself along lines of longitude.

Your points do make sense and scepticism is sold response, but still, when you remember one Nobel prize for rewriting understanding of matter was result of authoritarian powers demanding marble, not wooden tables in university labs, well...
Thing is, there was no ambiguity about whether high temperature superconductors worked. Anyone with a sample could test it and it would remain a superconductor at temperatures two or three times higher than expected.

Here we have, as yet, considerable ambiguity about whether the drive works, and it's not clear to me whether the teams claiming to have built it have bothered to publish the cavity geometry, which is what it would take to allow others to reproduce the experiment freely.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-05-06 04:48pm

Simon_Jester wrote:This reactionless drive, on the other hand, is about quantum electrodynamics in a complete vacuum, which is a much better understood and "no surprises in half a century" field.

The muon anomalous magnetic moment maybe?

It's not that surprises are categorically impossible, it's that this isn't the first and probably not the tenth time someone has proposed a reactionless drive that runs on quantum woo, using a technobabble explanation that makes about as much sense as saying that your car engine runs by pulling itself along lines of longitude.

Hmm... is this the first time one has got so much experimental evidence behind it though? Sure, this has happened to a higher degree with other major surprises, like ftl neutrinos, but I'm not aware of any ones which seem to break the conservation of momentum apart from the discovery of neutrinos (which don't count because it was broken much more heavily and they were also actually real).

Here we have, as yet, considerable ambiguity about whether the drive works, and it's not clear to me whether the teams claiming to have built it have bothered to publish the cavity geometry, which is what it would take to allow others to reproduce the experiment freely.

I would assume so, considering at the the spr team and the nasa team seem to have built the devices independently. Just look at them:
Image
vs
Image

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Simon_Jester » 2015-05-07 01:29am

jwl wrote:
Simon_Jester wrote:This reactionless drive, on the other hand, is about quantum electrodynamics in a complete vacuum, which is a much better understood and "no surprises in half a century" field.
The muon anomalous magnetic moment maybe?
That's predicted by quantum electrodynamics, to extreme accuracy. The word 'anomalous' doesn't mean 'we can't explain it' in this context.

QED is a theory that describes electromagnetism in quantum mechanical terms, the product of work done from the '30s up through the '50s or so. And it's still pretty much the definitive theory for "this is how electromagnetism works."

A reactionless drive that runs by magnetically manipulating quantum flux or whatever is not covered under QED, so either someone has just discovered some new physics (that predicts reactionless drives in which case it blows up the rest of physics), or it's quantum woo.

It's not that surprises are categorically impossible, it's that this isn't the first and probably not the tenth time someone has proposed a reactionless drive that runs on quantum woo, using a technobabble explanation that makes about as much sense as saying that your car engine runs by pulling itself along lines of longitude.
Hmm... is this the first time one has got so much experimental evidence behind it though? Sure, this has happened to a higher degree with other major surprises, like ftl neutrinos, but I'm not aware of any ones which seem to break the conservation of momentum apart from the discovery of neutrinos (which don't count because it was broken much more heavily and they were also actually real).
The problem here is the word "SEEM" in "seem to break the conservation of momentum."

The problem isn't just "oh wow, a violation of a conservation law." The problem is that conservation laws are built into all the underlying logic and mathematics that goes into describing how physical laws relate to each other. Declaring conservation of momentum to be "only sometimes true" instead of "always true" is deeply problematic.

It would be far less problematic to posit that momentum is somehow transferred by an unknown force between the engine and some other thing... but then the question is what the other thing is, and what force makes it possible.

Here we have, as yet, considerable ambiguity about whether the drive works, and it's not clear to me whether the teams claiming to have built it have bothered to publish the cavity geometry, which is what it would take to allow others to reproduce the experiment freely.

I would assume so, considering at the the spr team and the nasa team seem to have built the devices independently. Just look at them:
Image
vs
Image
Huh.

On the other hand... those are cones. A cone shape is not that unusual for a radio-frequency cavity... so I'm dubious of the idea that no one's ever built an RF cavity that SHOULD double as a reactionless drive by accident before, under this theory.

Are the specifications published anywhere we can locate? That's a very significant issue.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Terralthra » 2015-05-07 02:23am

Keep in mind that breaking conservation of momentum breaks a lot. Special relativity is out, for one thing.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-05-07 04:27am

Simon_Jester wrote:
jwl wrote:
Simon_Jester wrote:This reactionless drive, on the other hand, is about quantum electrodynamics in a complete vacuum, which is a much better understood and "no surprises in half a century" field.
The muon anomalous magnetic moment maybe?
That's predicted by quantum electrodynamics, to extreme accuracy. The word 'anomalous' doesn't mean 'we can't explain it' in this context.

The muon anomalous magnetic moment, not the electron one. That's slightly off from the standard model prediction, look it up.
It's not that surprises are categorically impossible, it's that this isn't the first and probably not the tenth time someone has proposed a reactionless drive that runs on quantum woo, using a technobabble explanation that makes about as much sense as saying that your car engine runs by pulling itself along lines of longitude.
Hmm... is this the first time one has got so much experimental evidence behind it though? Sure, this has happened to a higher degree with other major surprises, like ftl neutrinos, but I'm not aware of any ones which seem to break the conservation of momentum apart from the discovery of neutrinos (which don't count because it was broken much more heavily and they were also actually real).
The problem here is the word "SEEM" in "seem to break the conservation of momentum."

The problem isn't just "oh wow, a violation of a conservation law." The problem is that conservation laws are built into all the underlying logic and mathematics that goes into describing how physical laws relate to each other. Declaring conservation of momentum to be "only sometimes true" instead of "always true" is deeply problematic.

Well yeah. But what's the answer to my question? Have there been any other events that seem to break the conservation of momentum with this level of experimental evidence? I'm not aware of any.

It would be far less problematic to posit that momentum is somehow transferred by an unknown force between the engine and some other thing... but then the question is what the other thing is, and what force makes it possible.

Well it says in the article where the nasa team think the momentum went if it works: the quantum vaccum. This would mean that the quantum vaccum has a reference frame, which may conflict with the principle of relativity. Furthermore, if the drive is to conform to the conservation of energy, and the Chinese force results hold up, and you can get roughly the same force in all directions; then this reference frame must be moving with the earth, because if they go faster than the power/force (3500m/s) then it is a first-kind perpetual motion machine. The speed of the earth around the sun is 30000 m/s.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Kuroneko » 2015-05-07 06:33am

The discovery of superconductors is a bad analogy for several reasons, foremost of which is that nothing in electromagnetism suggested that they're impossible in the first place. Rather, before actual superconductors were discovered, hypothetical ones have been used as toy models or in illustration of key principles.

jwl wrote:
Simon_Jester wrote:That's predicted by quantum electrodynamics, to extreme accuracy. The word 'anomalous' doesn't mean 'we can't explain it' in this context.

The muon anomalous magnetic moment, not the electron one. That's slightly off from the standard model prediction, look it up.

It shouldn't count as a "surprise". Some further corrections from beyond the standard model are completely expected, and the standard model already includes electroweak unification beyond QED. So confirming a disagreement between theoretical and experimental predictions wouldn't demonstrate any significant problem with QED. It would simply underscore the fact that QED becomes inappropriate once effects on the electroweak scale or beyond are included. However, those things are completely irrelevant for the microwave resonators, and wouldn't demonstrate any truly fundamental discrepancy like Lorentz symmetry breaking anyway.

Perhaps the proton charge radius would be a better if still quite imperfect analogy, with the one measured using electrons significantly different from the corresponding experiments with muons.


jwl wrote:Well yeah. But what's the answer to my question? Have there been any other events that seem to break the conservation of momentum with this level of experimental evidence? I'm not aware of any.

Right now, it's at the "we don't really understand what's going on" stage. That might change in the future, but it's not remotely particularly good evidence of momentum nonconservation at this point in time.

jwl wrote:Well it says in the article where the nasa team think the momentum went if it works: the quantum vaccum. This would mean that the quantum vaccum has a reference frame, which may conflict with the principle of relativity.

The NASA team's statements about the quantum vacuum approach the "subatomic bacteria" level of misuse of terms. Whatever is going on, that's not it.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-05-07 09:43am

Kuroneko wrote:
jwl wrote:
Simon_Jester wrote:That's predicted by quantum electrodynamics, to extreme accuracy. The word 'anomalous' doesn't mean 'we can't explain it' in this context.

The muon anomalous magnetic moment, not the electron one. That's slightly off from the standard model prediction, look it up.

It shouldn't count as a "surprise". Some further corrections from beyond the standard model are completely expected, and the standard model already includes electroweak unification beyond QED. So confirming a disagreement between theoretical and experimental predictions wouldn't demonstrate any significant problem with QED.

Point taken.
Perhaps the proton charge radius would be a better if still quite imperfect analogy, with the one measured using electrons significantly different from the corresponding experiments with muons.

I was thinking the proton charge radius, but the main reason I didn't include it was that the problem is far more likely to lie in QCD than QED, whereas with the muon magnetic moment QED would still be the predominant contribution, so differences in that are more likely. But yeah, again this falls to the same argument expressed above: deviations from the standard model were expected anyway.
jwl wrote:Well yeah. But what's the answer to my question? Have there been any other events that seem to break the conservation of momentum with this level of experimental evidence? I'm not aware of any.

Right now, it's at the "we don't really understand what's going on" stage. That might change in the future, but it's not remotely particularly good evidence of momentum nonconservation at this point in time.

Well, no, this isn't particularly good evidence for momentum non-conservation. But it's still the best evidence we've seen since the discovery of the neutrino, as far as I am aware.
jwl wrote:Well it says in the article where the nasa team think the momentum went if it works: the quantum vaccum. This would mean that the quantum vaccum has a reference frame, which may conflict with the principle of relativity.

The NASA team's statements about the quantum vacuum approach the "subatomic bacteria" level of misuse of terms. Whatever is going on, that's not it.

Well it does seem rather that their version of the quantum vacuum is more something different which shares traits with the quantum vacuum, yeah. But reading a bit of that the thread it seems the least terrible explanation offered (other than, say, your meter is broken). The spr team think it can be explained by special relativity and think of the momentum in terms of the individual photons, neglecting the simple fact that you've got a box not emitting anything which is producing a force; and the chinese team base it on some weird gravitational effect. Also, the nasa group apparently built a model based on this idea which they say matches their results within 2% and seems to fit in with the results of the other teams too. So if this is legit, whatever quantum-vacuum-like entity they've introduced in their model is a much better candidate than the suggestions of the other two teams.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Kuroneko » 2015-05-07 03:53pm

jwl wrote:I was thinking the proton charge radius, but the main reason I didn't include it was that the problem is far more likely to lie in QCD than QED, whereas with the muon magnetic moment QED would still be the predominant contribution, so differences in that are more likely. But yeah, again this falls to the same argument expressed above: deviations from the standard model were expected anyway.

I think here the electron/muon difference in proton charge radius is simply too huge. In the magnetic moment case, the deviation between theory and experiment is so small as to naturally suggest a very high-order correction from high-energy effects. In the case of the proton charge radius, the low-energy theory 'should' be able to deal with it.

You're right in that the problem is not clearly with QED (it's very unclear what's going on at all), but at least it's plausible to suspect QED because it's directly about electromagnetic interactions between protons and other charged particles. Well, the problem may not be with any theory in itself, QED or QCD, but rather due to overlooking something nonobvious that the standard model would already predict. But I don't know nearly enough about it to judge what's most likely.

jwl wrote:Well, no, this isn't particularly good evidence for momentum non-conservation. But it's still the best evidence we've seen since the discovery of the neutrino, as far as I am aware.

Here we are seeing reports of preliminary work before it's even peer-reviewed. I would bet that by those standards, evidence of similar strength occurs with high regularity. Some form of antigravity using superconductors was all the rage in the previous two decades, for example, some of it made it past peer review and some of it funded by NASA as well.

jwl wrote:Well it does seem rather that their version of the quantum vacuum is more something different which shares traits with the quantum vacuum, yeah.

Even if one takes it seriously, I don't think 'quantum vacuum' is appropriate even as an analogy. It would be something else that's called 'quantum vacuum' for bizarre and dubious reasons.

jwl wrote:Also, the nasa group apparently built a model based on this idea which they say matches their results within 2% and seems to fit in with the results of the other teams too. So if this is legit, whatever quantum-vacuum-like entity they've introduced in their model is a much better candidate than the suggestions of the other two teams.

IIRC they were saying that about a year ago (too?), i.e. before actually testing their drive in near-vaccuum and seeing most of the thrust vanish.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-05-07 04:51pm

Kuroneko wrote:
jwl wrote:Well, no, this isn't particularly good evidence for momentum non-conservation. But it's still the best evidence we've seen since the discovery of the neutrino, as far as I am aware.

Here we are seeing reports of preliminary work before it's even peer-reviewed. I would bet that by those standards, evidence of similar strength occurs with high regularity. Some form of antigravity using superconductors was all the rage in the previous two decades, for example, some of it made it past peer review and some of it funded by NASA as well.

I'm not sure about this, but I thought the chinese experiment (not in a vacuum) was published? Original experiments+one published+one in a vaccum with no known cases of it failing to work (yet) is decently rare for something like this. I don't know much about that antigravity one, does that defy the conservation of momentum?

jwl wrote:Also, the nasa group apparently built a model based on this idea which they say matches their results within 2% and seems to fit in with the results of the other teams too. So if this is legit, whatever quantum-vacuum-like entity they've introduced in their model is a much better candidate than the suggestions of the other two teams.

IIRC they were saying that about a year ago (too?), i.e. before actually testing their drive in near-vaccuum and seeing most of the thrust vanish.

Was this the same team? I didn't know that. What did they predict beforehand? What data did they get beforehand?

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby ZOmegaZ » 2015-05-08 07:56pm

Great summary here of both Cannae Drive and EmDrive:
http://www.reddit.com/r/Futurology/comm ... about_the/

Cannae Tests So Far

The only independent (not conducted by the inventor, the inventor's company, or by labs hired by the inventor) tests of the Cannae Drive that I can verify have been done by Eagleworks at the Johnson Space Center.

They performed three tests:

The device as the inventor designed it.
The device as the inventor designed it without the slotting that the inventor claimed was critical. (Called the "null test".)
A control test that used the same energy, but without the cavity present in the design.

The results of these tests were as follows:

Approximately 25 micronewtons of thrust at 50 Watts.
The same results as test #1, showing that at the very least, the slotting provided no benefit or detriment to the effect happening.
No measurable thrust.

For each of these tests they use a torsion pendulum which could measure thrust down to about 10 micronewtons or so. They also ran the test multiple times. In addition, they ran the test in two directions, making sure that the directional thrust changed with the direction of the device (to attempt to eliminate the possibility of noise or instrumentation error). The Cannae Drive passed these test, and the control test showed it was unlikely (although not impossible) to be a heating or air current effect.

The confusion over the naming of the "null test" however led many people to think that NASA reported the same thrust in the control test. This was not the case. The fact that the null test showed only that the inventor's ideas for why thrust was being measured were incomplete or wrong, but it is certain that thrust was measured. That still does not eliminate other factors in measurement or the test setup that might have accounted for the measured thrust, although the control test does make the list smaller.

The "null test" also was only performed on the Cannae Drive, and has no bearing on the EmDrive tests, as the EmDrive has no such features which might have be tested in this way, which has been another point of confusion among many people.
EmDrive Tests

The following independent tests have been performed for the EmDrive.

A test at 2500 W of power during which a thrust of 750 millinewtons was measured by a Chinese team at the Chinese Northwestern Polytechnical University.
A test at 50 W of power during which a thrust of 50 micronewtons was measured by Eagleworks at the Johnson Space Center at ~760 Torr of pressure. (Summer 2014)
A test at 50 W of power during which a thrust of 50 micronewtons was measured by Eagleworks at the Johnson Space Center at ~5.0×10−6 torr or pressure. (Early 2015)
A test at 50 W of power during which an interferometer (a modified Michelson device) was used to measure the stretching and compressing of spacetime within the device, which produced initial results that were consistent with an Alcubierre drive fluctuation.

All these tests were conducted with a control device that did not produce thrust.

UPDATED

NOTE: a better source was found for the Chinese results, and I have changed this section to reflect that.

Test #1 was conducted at the direction of lead researcher Juan Yang. She tested the device at several power levels and frequencies using the same equipment used to test Ion Drives. The given result above was the largest result produced. Her team estimated that the total measurement error was less than 12%. Source 1 | Source 2

Tests number 2 and 3 were performed multiple times, changing direction of the device and observing a corresponding change in the direction of force. They were not especially careful about controlling for ALL variables however, mostly owing to the lack of funding for the project. The positive tests have resulted in more funding becoming available, although it is still very, very little, and possibly not enough to explain where the error occurred if the measurement is error of some kind.

Test #4 was performed, essentially, on a whim by the research team as they were bouncing ideas off each other, and was entirely unexpected. They are extremely hesitant to draw any conclusions based on test #4, although they certainly found it interesting.

The Eagleworks team has been able to dedicate very little hardware towards this experiment, as there has been almost no dedicated funding for this experiment. The lack of funding is related to how outlandish the claims are to those who understand physics very well, and the lack of adequate explanation on the math behind the devices from the inventors.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Tribble » 2015-05-08 11:11pm

IMO conducting more tests will be worthwhile. At the very least if the readings turn out to be due to an error it will be something for scientists to keep in mind when conducting similar experiments.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby Darth Holbytlan » 2015-07-29 05:24pm

Updated article wrote:"I noted in [the study’s] conclusion paragraphs that [Tajmar’s] apparatus was producing hundreds of micro-Newtons of thrust when it got very hot and that his measuring instrumentation is not very accurate when the apparatus becomes hot," Davis told io9. "He also stated that he was still recording thrust signals even after the electrical power was turned off which is a huge key clue that his thrust measurements are all systematic artifact false positive thrust signals."

If the drive is still measured to be working when it is turned off, that is a pretty big hint that it's a measurement artifact. Which is pretty much what we should be assuming, anyway, since it is such a more likely explanation than conservation of momentum turning out to be wrong.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Sp

Postby jwl » 2015-07-29 06:20pm

Darth Holbytlan wrote:
Updated article wrote:"I noted in [the study’s] conclusion paragraphs that [Tajmar’s] apparatus was producing hundreds of micro-Newtons of thrust when it got very hot and that his measuring instrumentation is not very accurate when the apparatus becomes hot," Davis told io9. "He also stated that he was still recording thrust signals even after the electrical power was turned off which is a huge key clue that his thrust measurements are all systematic artifact false positive thrust signals."

If the drive is still measured to be working when it is turned off, that is a pretty big hint that it's a measurement artifact. Which is pretty much what we should be assuming, anyway, since it is such a more likely explanation than conservation of momentum turning out to be wrong.

Well, yeah. From the paper: "We also observed that the thrust appeared not to go down to zero immediately after power is switched-off but rather noted a gradual decrease which still looks like a thermal artefact".

Also, the drive apparently seems to be producing a thrust sideways or something as well, something not predicted by anyone.



Apparently Shawyer (the guy who originally stumbled upon this) has got published now too, but given that the publisher for some reason allowed his bizarre Doppler theory section to go through to publication, that isn't saying much. http://www.sciencedirect.com/science/article/pii/S0094576515002726?np=y

I mean, fair enough on letting the experimental stuff get published and even the space engine speculation. But Shawyer's Doppler idea doesn't say where the momentum is supposed to be going to from a "black box" perspective but still claims to be consistent with mainstream physics. The publishers should have cut that bit out, at least.

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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Jaepheth » 2015-11-03 04:49pm

So... this thing's back in the news.

And still reporting unexplained thrust.

Biggest new thing seems to be they've ruled out Lorentz force interactions between the drive and Earth's magnetic field.

Yahoo wrote:NASA confirms that the ‘impossible’ EmDrive thruster really works, after new tests
digital-trends By Rick Stella
4 hours ago

Engineer Roger Shawyer’s controversial EmDrive thruster jets back into relevancy this week, as a team of researchers at NASA’s Eagleworks Laboratories recently completed yet another round of testing on the seemingly impossible tech. Though no official peer-reviewed lab paper has been published yet, and NASA institutes strict press release restrictions on the Eagleworks lab these days, engineer Paul March took to the NASA Spaceflight forum to explain the group’s findings. In essence, by utilizing an improved experimental procedure, the team managed to mitigate some of the errors from prior tests — yet still found signals of unexplained thrust.

Isaac Newton should be sweating.

Flying in the face of traditional laws of physics, the EmDrive makes use of a magnetron and microwaves to create a propellant-less propulsion system. By pushing microwaves into a closed, truncated cone and back towards the small end of said cone, the drive creates the momentum and force necessary to propel a craft forward. Because the system is a reaction-less drive, it goes against humankind’s fundamental comprehension of physics, hence its controversial nature.

On the NASA spaceflight forums, March revealed as much as he could about the advancements that have been made with EmDrive and its relative technology. After apologizing for not having the ability to share pictures or the supporting data from a peer-reviewed lab paper, he starts by explaining (as straightforward as rocket science can get) that the Eagleworks lab successfully built and installed a 2nd generation magnetic damper which helps reduce stray magnetic fields in a vacuum chamber. The addition reduced magnetic fields by an order of magnitude inside the chamber, and also decreased Lorentz force interactions.

However, despite ruling out Lorentz forces almost entirely, March still reported a contamination caused by thermal expansion. Unfortunately, this reported contamination proves even worse in a vacuum (i.e. outer space) due in large part to its inherently high level of insulation. To combat this, March acknowledged the team is now developing an advanced analytics tool to assist in the separation of the contamination, as well as an integrated test which aims to alleviate thermally induced errors altogether.

While these advancements and additions are no doubt a boon for continued research of the EmDrive, the fact that the machine still produced what March calls “anomalous thrust signals” is by far the test’s single biggest discovery. The reason why this thrust exists still confounds even the brightest rocket scientists in the world, but the recurring phenomenon of direction-based momentum does make the EmDrive appear less a combination of errors and more like a legitimate answer to interstellar travel.

Eagleworks Laboratories’ recent successful testing is the latest in a long line of scientific research allowing EmDrive to slowly shed its “ridiculous” title. Though Shawyer unveiled the device in 2003, it wasn’t until 2009 that a group of Chinese scientists confirmed what he initially asserted to be true — that is, that filling a closed, conical container with resonating microwaves does, in fact, generate a modest amount of thrust towards the wide end of the container. Although extremely cautious about the test, the team in China found the theoretical basis to be correct and that net thrust is plausible.

The thing is, the initial reaction on this theory (especially from the west) was met with polite skepticism. Though the published work showed the calculations to be consistent with theoretical calculations, the test was conducted at such low power that the results were widely deemed to be useless. Luckily, this didn’t stop the good folks over at NASA from giving the EmDrive a spin, resulting in an official study that was conducted in August of 2013. After deliberating on the findings, the space agency officially published its judgment in June of the following year before presenting it at the 50th Joint Propulsion Conference in Cleveland, Ohio.

NASA concluded the RF resonant cavity thruster design does produce thrust “not attributable to any classical electromagnetic phenomenon.” In other words, NASA confirmed Shawyer’s initial prognosis (much like the team of Chinese scientists), but couldn’t come up with a reasonable explanation as to why the thing works outside of, “it just does.”

Moving forward, NASA’s short term objective is to conduct a diverse array of tests on a quantum vacuum plasma thruster (a similar propellantless engine flatter in shape than the EmDrive), in hopes of gaining independent verification and validation of the thruster. Initial IV&V testing will be supported by the Glenn Research Center in Cleveland, Ohio, making use of a stainless steel vacuum chamber which has the capacity to detect force at a single-digit micronewton level, called a low-thrust torsion pendulum.

After that, a similar round of low-thrust torsion pendulum tests will then be conducted at NASA’s Jet Propulsion Laboratory before comparing the findings. It’s also reported that the Johns Hopkins University Applied Physics Laboratory has contacted the lab about conducting Cavendish Balance-type testing of the IV&V shipset. Ideally, this test would allow Johns Hopkins to measure the amount of gravitational force exerted in propellantless engines.

At this time, it’s unknown when Eagleworks Laboratories intends to officially publish its peer-reviewed paper, but even so, just hearing of the EmDrive’s advancements from one of its top engineers bodes well for the future of this fascinating tech.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby jwl » 2015-11-05 12:50pm



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