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 Space

Postby jwl » 2015-11-05 02:57pm

Reading through the thread, he seems to indicate that a paper with more details will be published sometime in the first half of next year.

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

Postby cadbrowser » 2015-11-12 08:37am

I am curious about the part where the Cannae test that was conducted where they removed the cavity and observed no thrust. The cavity, am I correct in understanding that meant the cone shaped aperture?
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby jwl » 2015-11-13 04:44am

cadbrowser wrote:I am curious about the part where the Cannae test that was conducted where they removed the cavity and observed no thrust. The cavity, am I correct in understanding that meant the cone shaped aperture?

The Cannae drive is similier to the emdrive but not the same thing. Here is a picture: Image

The same article you are referring to does mention that the emdrive also had a control, in which case it would be the cone-shaped thing.

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

Postby Enigma » 2015-11-15 09:27pm

jwl wrote:
cadbrowser wrote:I am curious about the part where the Cannae test that was conducted where they removed the cavity and observed no thrust. The cavity, am I correct in understanding that meant the cone shaped aperture?

The Cannae drive is similier to the emdrive but not the same thing. Here is a picture: Image

The same article you are referring to does mention that the emdrive also had a control, in which case it would be the cone-shaped thing.


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

Postby bilateralrope » 2016-11-21 07:08am

An update:

It's official: NASA's peer-reviewed EM Drive paper has finally been published
It works.
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After months of speculation and leaked documents, NASA's long-awaited EM Drive paper has finally been peer-reviewed and published. And it shows that the 'impossible' propulsion system really does appear to work.

The NASA Eagleworks Laboratory team even put forward a hypothesis for how the EM Drive could produce thrust – something that seems impossible according to our current understanding of the laws of physics.

In case you've missed the hype, the EM Drive, or Electromagnetic Drive, is a propulsion system first proposed by British inventor Roger Shawyer back in 1999.

Instead of using heavy, inefficient rocket fuel, it bounces microwaves back and forth inside a cone-shaped metal cavity to generate thrust.

According to Shawyer's calculations, the EM Drive could be so efficient that it could power us to Mars in just 70 days.

But, there's a not-small problem with the system. It defies Newton's third law, which states that everything must have an equal and opposite reaction.

According to the law, for a system to produce thrust, it has to push something out the other way. The EM Drive doesn't do this.

Yet in test after test it continues to work. Last year, NASA's Eagleworks Laboratory team got their hands on an EM Drive to try to figure out once and for all what was going on.

And now we finally have those results.

The new peer-reviewed paper is titled "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum", and has been published online as an open access 'article in advance' in the American Institute of Aeronautics and Astronautics (AIAA)’s Journal of Propulsion and Power. It'll appear in the December print edition.

It's very similar to the paper that was leaked online earlier this month and, most notably, shows that the drive does indeed produce 1.2 millinewtons per kilowatt of thrust in a vacuum:
"Thrust data from forward, reverse, and null suggested that the system was consistently performing at 1.2 ± 0.1 mN/kW, which was very close to the average impulsive performance measured in air. A number of error sources were considered and discussed."


To put that into perspective, the super-powerful Hall thruster generates force of 60 millinewtons per kilowatt, an order of magnitude more than the EM Drive.

But the Hall thruster requires propellants, and that extra weight could offset the higher thrust, the team concludes.

Light sails on the other hand, which are currently the most popular form of zero-propellant propulsion, only generate force up to 6.67 micronewtons per kilowatt – two orders of magnitude less than NASA's EM Drive, says the paper.

But the team makes it clear that they also weren't attempting to optimise performance in these tests – all they were doing was trying to prove whether or not the drive really works. So it's likely that the EM Drive could get a lot more efficient still.

When it comes to how the drive actually works without messing up the laws of physics, that's a little less clear.

It's not the focus of this paper, but the team does offer a hypothesis:
"[The] supporting physics model used to derive a force based on operating conditions in the test article can be categorised as a nonlocal hidden-variable theory, or pilot-wave theory for short."


Pilot-wave theory is a slightly controversial interpretation of quantum mechanics.

It's pretty complicated stuff, but basically the currently accepted Copenhagen interpretation of quantum mechanics states that particles do not have defined locations until they are observed.

Pilot-wave theory, on the other hand, suggests that particles do have precise positions at all times, but in order for this to be the case, the world must also be strange in other ways – which is why many physicists have dismissed the idea.

But in recent years, the pilot-wave theory has been increasing in popularity, and the NASA team suggests that it could help explain how the EM Drive produces thrust without appearing to propel anything in the other direction.

"If a medium is capable of supporting acoustic oscillations, this means that the internal constituents were capable of interacting and exchanging momentum," the team writes.

"If the vacuum is indeed mutable and degradable as was explored, then it might be possible to do/extract work on/from the vacuum, and thereby be possible to push off of the quantum vacuum and preserve the laws of conservation of energy and conservation of momentum."

Of course, this is just one hypothesis, based on one round of tests. There's a lot more work to be done before we can say for sure whether the EM Drive is really producing thrust – the team notes they that more research is needed to eliminate the possibility that thermal expansion could somehow be skewing the results.

And even once that's confirmed, we'll then need to figure out exactly how the system works.

The scientific community is also notoriously unconvinced about the propulsion system – just yesterday a Motherboard article on the EM Drive was deleted by the moderators of the popular subreddit r/Physics because they "consider the EM Drive to be unscientific".

But is the first peer-reviewed research ever published on the EM Drive, which firmly takes it out of the realm of pseudoscience into a technology that's worth taking skeptically, but seriously.

The next step for the EM Drive is for it to be tested in space, which is scheduled to happen in the coming months, with plans to launch the first EM Drive having been made back in September.

If it produces thrust there, the scientific community will need to sit up and take note. Watch this space.

You can read the full research paper here.


If I'm understanding this right, the EM Drive has passed all the tests NASA can run on the ground.

The next steps are the reproduction of NASAs results and a test in space. Only the test in space will convince me that the EM Drive is working.

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

Postby The Romulan Republic » 2016-11-21 09:39am

Um... holy shit.

I really hope this doesn't turn out to be one of those "too good to be true" discoveries.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Tribble » 2016-11-21 10:33am

For the non-scientist dummies out there, why would this necessarily be a violation of Newton's Third Law? Couldn't the microwaves be interacting with something in some way that we can't really detect?

Also, have the odds of this thing working actually increased, or is it still far more likely that there was some error that wasn't detected?
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Simon_Jester » 2016-11-21 10:55am

The real test for "this might work" is NOT publication, it's replication.

It doesn't matter if nobody ever publishes a peer-reviewed paper on this, if several different groups build working drives. Nobody had to publish papers on fire or the wheel to make them successful technologies.

What does matter is that just anyone can build a working reactionless drive by following the correct procedures. If I make the wheel the correct shape, it doesn't matter who I am, it will work. Because wheels as such are a technology that works.

Pons and Fleischmann published a paper on their 'cold fusion' work, too. That didn't mean they actually had a working cold fusion reactor. It just means they thought they did, and they found peer reviewer(s) willing to sign off on their paper.

So here, I'm going to wait to see what happens when, oh, ten other laboratories all do the same thing and try to build corresponding drives using the same cavity geometry.

"Eagleworks" is still, frankly, a hack lab run by a hack man. They may have finally found something that works, but I remain skeptical.

bilateralrope wrote:If I'm understanding this right, the EM Drive has passed all the tests NASA can run on the ground.
No, they've passed all the tests one group can run on the ground. This has happened before, and will no doubt happen again.

I'm not clear on exactly how much the reactionless drive design here weighs, but unless it is really light (as in, CubeSat light), it would make a lot more sense to have several different groups try to build the drive on the ground, using the cavity geometry Eagleworks claims is working.

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

Postby Adam Reynolds » 2016-11-21 12:22pm

Even if this does work, unless they could massively increase the efficiency, it would actually be worse in practice than an ion engine most of the time. It only becomes more efficient when we are talking about missions with endurance times outside of the solar system.

Tribble wrote:For the non-scientist dummies out there, why would this necessarily be a violation of Newton's Third Law? Couldn't the microwaves be interacting with something in some way that we can't really detect?

It is rather complicated, but it has the potential to produce more kinetic energy than the amount of electrical energy that was put into it, which would lead to a violation of conservation of energy. While photon thrusters are a thing, exploiting the fact that massless light still has momentum, this is supposedly much more efficient.

In effect, it is the same problem as any other perpetual motion machine. Any solution to this problem runs into relativistic issues, as it would lead to the system having a different acceleration in different reference frames.

Also, have the odds of this thing working actually increased, or is it still far more likely that there was some error that wasn't detected?

Those odds haven't changed. The fact that it is peer reviewed just means there are no major problems in this paper. It doesn't mean there experiment has been confirmed by an outside laboratory, which would be needed before we throw out almost all of physics. Remember that these are the same people who believe they might just build a warp drive.

Most of this came from Scott Manley's video, which has a fair bit more depth on some of the problems:

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

Postby bilateralrope » 2016-11-21 12:28pm

Simon_Jester wrote:I'm not clear on exactly how much the reactionless drive design here weighs, but unless it is really light (as in, CubeSat light),


The article I linked links to another article about a planned launch by the EM Drives inventor. Using a cubesat.

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

Postby Simon_Jester » 2016-11-21 12:34pm

Adam Reynolds wrote:Even if this does work, unless they could massively increase the efficiency, it would actually be worse in practice than an ion engine most of the time. It only becomes more efficient when we are talking about missions with endurance times outside of the solar system.
True. Then again, I can't think of a single type of engine that was nearly as efficient when the first prototype was invented as it was 50-100 years later. It's not like the Newcomen steam engine could have been used to power a 19th century express locomotive.

Tribble wrote:For the non-scientist dummies out there, why would this necessarily be a violation of Newton's Third Law? Couldn't the microwaves be interacting with something in some way that we can't really detect?
It is rather complicated, but it has the potential to produce more kinetic energy than the amount of electrical energy that was put into it, which would lead to a violation of conservation of energy. While photon thrusters are a thing, exploiting the fact that massless light still has momentum, this is supposedly much more efficient.

In effect, it is the same problem as any other perpetual motion machine. Any solution to this problem runs into relativistic issues, as it would lead to the system having a different acceleration in different reference frames.
IF, hypothetically, this device does work on an action-reaction basis and pushes on something we can't detect directly*, then there may well be an efficiency factor that drops off as velocity increases, or so that power requirement increases as velocity increases. There's no guarantee that a machine which produces fourteen millinewtons of force by pulling itself along lines of longitude at rest would produce fourteen millinewtons of force by pulling the same lines of longitude at 100 km/s.
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*Dark matter is a tempting candidate, but if microwaves could interact with dark matter then it wouldn't be 'dark,' so we're going to have to drop THAT idea...

Also, have the odds of this thing working actually increased, or is it still far more likely that there was some error that wasn't detected?
Those odds haven't changed. The fact that it is peer reviewed just means there are no major problems in this paper. It doesn't mean there experiment has been confirmed by an outside laboratory, which would be needed before we throw out almost all of physics. Remember that these are the same people who believe they might just build a warp drive.
Yeah. Basically, the peer review eliminates the possibility that the whole thing is obvious bullshit, but it does not eliminate the possibility of bullshit.

So, say, if the odds of it being a case of wishful thinking and bad experimental design were 99.99999999% before, maybe they're 99.99999995% now or something.

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

Postby Simon_Jester » 2016-11-21 01:25pm

GHETTO EDIT:

I've been thinking about the point Manley makes about special relativity and how "the drive becomes less efficient as a function of its speed" causes problems in special relativity.

Basically, the cause of this problem comes down to the fact that it sets up whatever medium the drive interacts with as a privileged frame of reference. Your speed relative to that medium matters objectively, in a way that your speed relative to an outside observer does not.

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

Postby jwl » 2016-11-22 06:28pm

Adam Reynolds wrote:
Tribble wrote:For the non-scientist dummies out there, why would this necessarily be a violation of Newton's Third Law? Couldn't the microwaves be interacting with something in some way that we can't really detect?

It is rather complicated, but it has the potential to produce more kinetic energy than the amount of electrical energy that was put into it, which would lead to a violation of conservation of energy. While photon thrusters are a thing, exploiting the fact that massless light still has momentum, this is supposedly much more efficient.

In effect, it is the same problem as any other perpetual motion machine. Any solution to this problem runs into relativistic issues, as it would lead to the system having a different acceleration in different reference frames.

Well, that is only the case if it does actually break the conservation of momentum. If it is pushing against undetectable medium as Tribble suggests, it would not break energy conservation because it would start losing thrust as it moves faster relative to that medium. It is worth considering though, that if that is the case, there is a limit to how much they can further increase the efficiency before you start having to worry about whether this medium is still relative to the earth, the sun, or the cosmic microwave background, since the natural velocity of the EM drive on earth's surface knocks down its efficiency in the direction of motion.

But really, this is ignoring the most likely explanation if it works, which involves much less wacky physics: the thing is actually an accidental ion engine or something similar. If that is the case, it should work perfectly fine in space, it 's just that it will eventually run out of propellant (copper), just like other ion drives do. I dunno how else you could test for that, but until that option is no longer on the table I doubt mainstream physics is going to make the leap from simply an orbital test. Although of course how on earth it would produce such an ion drive effect is still an open question, but you're probably going to be looking at less weird solutions than what else is on the table.

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

Postby atg » 2016-11-22 08:09pm

jwl wrote:But really, this is ignoring the most likely explanation if it works, which involves much less wacky physics: the thing is actually an accidental ion engine or something similar. If that is the case, it should work perfectly fine in space, it 's just that it will eventually run out of propellant (copper), just like other ion drives do. I dunno how else you could test for that


Measure the mass, turn it on for a while, and then measure mass again? If it is shedding copper as propellant that should be fairly straightforward.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Simon_Jester » 2016-11-22 08:28pm

jwl wrote:Well, that is only the case if it does actually break the conservation of momentum. If it is pushing against undetectable medium as Tribble suggests, it would not break energy conservation because it would start losing thrust as it moves faster relative to that medium. It is worth considering though, that if that is the case, there is a limit to how much they can further increase the efficiency before you start having to worry about whether this medium is still relative to the earth, the sun, or the cosmic microwave background, since the natural velocity of the EM drive on earth's surface knocks down its efficiency in the direction of motion.
You're tangling, here, with the problem that gave rise to the Michelson-Morley experiment: the belief that there is a privileged frame of reference relative to which all other speeds can be measured. Michelson and Morley were trying to measure the speed of light in different directions to show that the "natural velocity of the [interferometer] on earth's surface" would result in different measurements of c when the instrument was turned in different directions. Trouble is, that didn't happen, because the laws of physics don't change as a function of where you are or how fast you're going.

Relativity will alter your perceptions of events happening elsewhere, but it always alters them in consistent ways, so that everyone agrees on what the basic rules are and what the physical constants (such as c) are.

That is why the "this drive pushes on something we can't see" explanation causes relativity problems. If this "something" were to exist everywhere in the universe, and the drive's efficiency is measured relative to that thing, then that thing's position constitutes a special, privileged frame of reference. You could measure all velocities relative to the velocity of "that-which-is-pushed." And physics would be concretely, measurably different, depending on how fast you were moving relative to this special medium and special frame of reference.

Michelson and Morley figured that you could do this relative to the luminiferous aether, that is to say, relative to the otherwise undetectable medium through which light propagated. The fact that light propagates equally quickly in all directions, and regardless of how fast you go, is strong evidence that the luminiferous aether does not exist.

For the EM drive to function as an inertialess drive, AND to avoid being a perpetual motion machine by permitting you to eventually start gaining more kinetic energy out of the drive than you put in via electricity... You would have to have the aether or something like it.

Of course, that leaves the possibility that the drive is inertial, that is to say, emits some recognizable kind of exhaust, on which more below...

But really, this is ignoring the most likely explanation if it works, which involves much less wacky physics: the thing is actually an accidental ion engine or something similar. If that is the case, it should work perfectly fine in space, it 's just that it will eventually run out of propellant (copper), just like other ion drives do. I dunno how else you could test for that, but until that option is no longer on the table I doubt mainstream physics is going to make the leap from simply an orbital test. Although of course how on earth it would produce such an ion drive effect is still an open question, but you're probably going to be looking at less weird solutions than what else is on the table.
The problem is that the energy is in the form of microwaves are bouncing around in a sealed container. That's not vaporizing anything. It's far more likely that it does literally nothing than that it somehow emits rocket exhaust made out of the vaporized contents of its own microwave cavity.

The other explanation is that the cavity somehow spawns exotic particles (e.g. neutrinos) that can pass through the walls and which act as the 'exhaust.' However, the thrust:power ratio of the EM drive is too high for it to be a massless particle, and no known particle that has mass would fit the description. Since the behavior of microwaves inside copper cones is well understood, there is little reason to expect that just making a copper cone in your dining room allows you to spawn exotic particles unknown under the Standard Model.

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

Postby K. A. Pital » 2016-11-24 03:22am

If experiments would confirm one of the non-mainstream explanations, it would be very, very unsettling.

It would mean that the scientific method has been used, over the past several decades, to construct a wrong model in the most important areas of fundamental research.

Far more relaxing would be a confirmation that this is just a fluke or error, or there is a form of propellant there we have not yet fully understood.

Don't misunderstand - I want Star Trek future to come sooner, I am just a bit wary of confirming such massive gaps in our scientific understanding of the world. If this could happen at such a fundamental level, then what to say of other, less precise, natural and, worse yet, social sciences?
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Ace Pace » 2016-11-24 04:06am

K. A. Pital wrote:If experiments would confirm one of the non-mainstream explanations, it would be very, very unsettling.

It would mean that the scientific method has been used, over the past several decades, to construct a wrong model in the most important areas of fundamental research.

Far more relaxing would be a confirmation that this is just a fluke or error, or there is a form of propellant there we have not yet fully understood.

Don't misunderstand - I want Star Trek future to come sooner, I am just a bit wary of confirming such massive gaps in our scientific understanding of the world. If this could happen at such a fundamental level, then what to say of other, less precise, natural and, worse yet, social sciences?


I think that's a very wrong statement to make. It would only say that the models we've built are not good enough to explain all phenomenons. This happens all the time and it's what drives scientific shifts. Physicists are looking for stuff that breaks the standard model (to take a serious example) because it might help lead them out of the rut they've found themselves there. An alternative example is the classic experimental problems which lead to Quantum Physics...

The scientific method is a way of generating models that are good enough to explain experiments and predict the results of future experiments. It is not a method for discovering "truth".
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby K. A. Pital » 2016-11-24 04:26am

I am not implying overturning theories should not happen.

But it would demonstrate severe deficiencies in theoretic concepts. Deficiencies that persisted for decades. In the end, significant resources could be commited by mankind in a completely wrong direction, and our advanced state of scientific understanding cannot preclude this.

This is not a bad thing, but it is a warning sign to humans not to get too optimistic about their understanding of space, time and the universe - presuming the experiements confirm the anomaly, of course, like I said before.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Starglider » 2016-11-24 08:38am

Simon_Jester wrote:There's no guarantee that a machine which produces fourteen millinewtons of force by pulling itself along lines of longitude at rest would produce fourteen millinewtons of force by pulling the same lines of longitude at 100 km/s.


I am not clear what the relevant reference frame for quantum vacuum interactions is, but I'm pretty sure it isn't 'the nearest planet'. The Earth is moving at 30 km/s relative to the Sun, the Sun is moving at about 200 km/s relative to the Milky Way, and the Milky Way is moving at about 500 km/s relative to the cosmic microwave background (the closest thing to a 'universal' reference frame there is). Follow on tests would hopefully try and identify directional asymmetry in the thrust.
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Starglider » 2016-11-24 08:49am

Demonstrating major gaps in existing particle physics theories would not be a problem. There are numerous widely acknowledged problems and open questions with existing models, which have only been around for a few decades; not long, in the history of science. What would be concerning is if a 'crank' experiment proved to be the source of a revolutionary advance; we would have to ask, why were 'cranks' able to do something that the massively better funded, respectable scientific establishment were not?
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Re: Test Suggests NASA's Impossible EM Drive Will Work In Space

Postby Simon_Jester » 2016-11-24 02:13pm

K. A. Pital wrote:I am not implying overturning theories should not happen.

But it would demonstrate severe deficiencies in theoretic concepts. Deficiencies that persisted for decades. In the end, significant resources could be commited by mankind in a completely wrong direction, and our advanced state of scientific understanding cannot preclude this.

This is not a bad thing, but it is a warning sign to humans not to get too optimistic about their understanding of space, time and the universe - presuming the experiements confirm the anomaly, of course, like I said before.
To be fair, we had a very similar collective experience towards the end of the 19th century. In 1890, almost all known things were considered physically explicable using known science- except biology, and most people were confident they'd figure that out fairly quickly.

In 1925, this was no longer the case, and we were frantically inventing new science to explain things that simply had not been seriously considered or even perceived prior to the late 1800s.

Starglider wrote:
Simon_Jester wrote:There's no guarantee that a machine which produces fourteen millinewtons of force by pulling itself along lines of longitude at rest would produce fourteen millinewtons of force by pulling the same lines of longitude at 100 km/s.


I am not clear what the relevant reference frame for quantum vacuum interactions is, but I'm pretty sure it isn't 'the nearest planet'. The Earth is moving at 30 km/s relative to the Sun, the Sun is moving at about 200 km/s relative to the Milky Way, and the Milky Way is moving at about 500 km/s relative to the cosmic microwave background (the closest thing to a 'universal' reference frame there is). Follow on tests would hopefully try and identify directional asymmetry in the thrust.
Bear in mind, firstly, that I used "pulling itself along lines of longitude" as a deliberately bullshit technobabble example of how a reactionless drive might work. It was a parody, not a serious proposal.

Secondly, the issue I was originally discussing was that REGARDLESS of what the relevant reference frame would be for interaction with the quantum vacuum (or dark matter, or lines of longitude, or any other thing that cannot be directly observed)...

There is a very serious problem with any reactionless drive, namely that you can put energy in, and observe a fixed change in momentum as a result, because the drive applies force, not kinetic energy. At sufficiently high velocity, adding that little extra bit of momentum by keeping the drive switched on for a second will result in adding more kinetic energy than you used to power the drive.

This issue is related to, but not only related to, the question of "relative to what reference frame is this drive exerting a thrust?" Because a perpetual motion machine in one frame of reference is going to be a perpetual motion machine in all other points

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

Postby jwl » 2016-11-24 03:08pm

Starglider wrote:
Simon_Jester wrote:There's no guarantee that a machine which produces fourteen millinewtons of force by pulling itself along lines of longitude at rest would produce fourteen millinewtons of force by pulling the same lines of longitude at 100 km/s.


I am not clear what the relevant reference frame for quantum vacuum interactions is, but I'm pretty sure it isn't 'the nearest planet'. The Earth is moving at 30 km/s relative to the Sun, the Sun is moving at about 200 km/s relative to the Milky Way, and the Milky Way is moving at about 500 km/s relative to the cosmic microwave background (the closest thing to a 'universal' reference frame there is). Follow on tests would hopefully try and identify directional asymmetry in the thrust.

Of course if this "mutable quantum vacuum" or the aether or whatever you want to call it is a thing; and can carry momentum away, this means that the relevant reference frame can change when you you pump that momentum into it. So if that idea is true, and such a system can exchange momentum with the rest of the universe via resonant cavities like this, it might be the case that natural resonant cavities in the earth pull the aether around to be at rest with its surface. Of course, if that were to be the case, you would then start seeing a difference as soon as you put it in orbit or whatever anyway.

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

Postby Simon_Jester » 2016-11-24 04:07pm

Actually, that theory was considered and rejected in the 19th century, because if the Earth exerts a force dragging the local aether along with it, then that causes the kinetic energy associated with the Earth's orbit to dissipate due to drag- sort of like wind resistance. Over time, this would result in the Earth spiraling into the Sun, and planets in general doing the same thing. And we'd be able to tell this process was going on even if it was very subtle, because it would affect all celestial bodies in an otherwise inexplicable way.

Sort of like how the precession of the perihelion of Mercury led us to deduce that there was something important about gravity we didn't understand- and we noticed this problem decades before anyone was in a position to explain it.

Basically, we don't observe any evidence that Earth itself or any other part of our solar system is interacting at a steady rate with some otherwise undetectable object or force.

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

Postby jwl » 2016-11-25 08:14am

Simon_Jester wrote:Actually, that theory was considered and rejected in the 19th century, because if the Earth exerts a force dragging the local aether along with it, then that causes the kinetic energy associated with the Earth's orbit to dissipate due to drag- sort of like wind resistance. Over time, this would result in the Earth spiraling into the Sun, and planets in general doing the same thing. And we'd be able to tell this process was going on even if it was very subtle, because it would affect all celestial bodies in an otherwise inexplicable way.

Sort of like how the precession of the perihelion of Mercury led us to deduce that there was something important about gravity we didn't understand- and we noticed this problem decades before anyone was in a position to explain it.

Basically, we don't observe any evidence that Earth itself or any other part of our solar system is interacting at a steady rate with some otherwise undetectable object or force.

Well that drag would rather depend on the effective density of the aether and how much it interacts with itself, wouldn't it? In the 19th century they were looking at something that would transmit light in a similar manner to sound, so the values of one or both of these things has to be high. In this case, you're just looking at somewhere for the EMdrive to dump it's momentum, so these values wouldn't have to be as high, no? You could probably calculate a minimum value for these quantities based on the claimed thrust-to-power ratio of the EMDrive, mind, and if you find that it still should have noticeably slowed down the earth's orbit you can throw that idea out of the window.

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

Postby Sky Captain » 2016-11-25 03:31pm

If EMDrive pushes against some kind of medium to generate thrust why would it break down physics any more than pretty much any other vehicle that's not pure rocket? Cars, airplanes and ships don't become perpetual motion machines after reaching certain speed just because they all use existing medium to push against. You could put maglev train in vacuum tunnel with no drag and no matter how fast it would go there would be no way to get out more energy than put in. Why EMDrive would be any different?


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