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New Test Supports NASA's Controversial EM Drive
An anonymous reader writes: Last year, NASA's advanced propulsion research wing made headlines by announcing the successful test of a physics-defying electromagnetic drive, or EM drive. Now, this futuristic engine, which could in theory propel objects to near-relativistic speeds, has been shown to work inside a space-like vacuum. NASA Eagleworks made the announcement quite unassumingly via NASASpaceFlight.com. The EM drive is controversial in that it appears to violate conventional physics and the law of conservation of momentum; the engine, invented by British scientist Roger Sawyer, converts electric power to thrust without the need for any propellant by bouncing microwaves within a closed container. So, with no expulsion of propellant, there’s nothing to balance the change in the spacecraft’s momentum during acceleration.
I want a non-Newtonian drive as much as any other nerd out there, but it's still more probable that (assuming it works) it uses conventional physics, just in ways they haven't figured out yet.
That said, I think this result is the point where NASA, DOD, Lockheed Martin, Boeing et al should turn on the money spigot for research. There's obviously something going on, even if it's just conventional physics in unexpected ways. And on the odd chance it *is* new physics, the results could change the world.
They've gone into plaid?
Well the tests keep showing the damn thing works! Maybe it's just magic. Works based on fairies flying out of an engineer's butt, or something. Hopefully it doesn't break the universe :-/
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
I see you like to comment on something without reading it.... try taking a look at the article... it says specifically that conservation of momentum is NOT violated...
Well, the article says it, so it must be true.
If you're not throwing anything out of the back of the rocket, you're violating conservation of momentum.
When it spends 99% of its launch mass lifting itself to orbit, you have a bad system. Nice to see people trying to think outside the box.
Technically, they're keeping it all in the box.
The cesspool just got a check and balance.
Let's see: we can violate conservation of momentum by invoking some sort of vaguely defined quantum woo. Riiiight. Where do I send my check?
The practical result says that it works anyway.
I suspect that there is a balance in physics somewhere... just that no one knows where or what that is yet.
I am kind of curious though - does it have the acceleration curve of a VASMIR/Ion engine, or can we build something with it that will give greater speed in less time?
(...also, is the acceleration graph linear, curved sharply in either direction, hits a curve at a certain point... what?)
Quo usque tandem abutere, Nimbus, patientia nostra?
Actually, the test shows that is not fairies flying out of the engineer's butt, but rather invisible unicorns pushing the unit. Those tricky magical bastards....
I suspect that there is a balance in physics somewhere... just that no one knows where or what that is yet.
This.
Just because we can't see the balance doesn't mean it isn't there.
This might be another Cold Fusion moment. Or, it might be the start of something very interesting.
When an experiment contradicts a theory, there are two possibilities: (1) there's something wrong with the experiment; or (2) there's something wrong with the theory. If the correct answer is (1), then it's par for the course: mistakes happen, and the process of science corrects them eventually. But if the correct answer is (2) then it's cork-popping time, because you have discovered new science.
If it weren't for deadlines, nothing would be late.
[T]he EM Drive’s thrust was due to the Quantum Vacuum (the quantum state with the lowest possible energy) behaving like propellant ions behave in a MagnetoHydroDynamics drive (a method electrifying propellant and then directing it with magnetic fields to push a spacecraft in the opposite direction) for spacecraft propulsion.
So the recent test was trying to replicate the results in a vacuum to eliminate some unknown other factor as the explanation.
This posting is provided 'AS IS' without warranty of any kind, implied or otherwise.
If nobody knows how it works, how did the guy invent it?
Just like penicillin.
Don't disappoint your bird dog. Go to the range.
That is what peer review, replication of results and further study are for...and I am biting my lip not to add "dumbass" to the end of that sentence.
And BTW: those things are already happening. Other scientists are critiquing (constructively rather than your sort of nonsense) and others are carrying out new experiments in the same and novel situations to eliminate confounds. You know, the scientific world doing what they do.
What I find absolutely amazing here (apart from the *potential* discovery) is how everyone is more interested in bagging on the science than commenting on how this might be a major breakthrough after NASA (FFS) has been confirming the results.
Yes, it may not be as it is. But it is also WAAY too early to cry foul.
Some days the internet its like watching a tribe of chimps...
It is the same as if you are locked in a cage and bump yourself against the wall - the cage eventually moves. yet nothing is expelled outside of the cage.
Doesn't that only work because of static friction though? Bump hard enough to break the static friction and scoot across the floor, then move slowly when reversing such that you don't break the static friction on the way back.
They say one of the limiting factors (aside from violating the laws of physics) is the political will to launch a large nuclear power plant into space. The solution is obvious: use Cold Fusion to power the EM drive. There is great efficiency here because they can get two Nobel prizes with only one gadget.
We don't see the world as it is, we see it as we are.
-- Anais Nin
If two magnets get close enough and snap together are they violating conservation of momentum when forces are acting on them to accelerate toward each other?
Of course not. The total momentum of the system stays zero.
When I was a kid, I tried to make a self-propelled car by putting magnets on the back and front bumpers of a toy car, reasoning that the front magnet would attract the back one, and therefore produce thrust. When I built it, I learned a valuable lesson: it doesn't work. Because the force pulling the back magnet forward is exactly counterbalanced by the force pulling the front magnet backward.
The EM drive is closely analagous to this idea. Except that they didn't figure out when they were eight that this will never work.
A lovely summary from the Physics StackExchange which sums up my thoughts:
"The initial tests were at atmospheric pressure. To test the fan hypothesis, an easy way is to vary the pressure, another easy way is to put dust in the air to see the air-currents. The experimenters didn't do any of this (or at least didn't publish it if they did), instead, they ran the device inside a vacuum chamber but at ambient pressure after putting it through a vacuum cycle to simulate space. This is not a vacuum test, but it can mislead one on a first read.
In response to criticism of this faux-vacuum test, they did a second test in a real vacuum. This time, they used a torsion pendulum to find a teeny-tiny thrust of no relation to the first purported thrust. The second run in vacuum has completely different effects, possibly due to interactions between charge building up on the device and metallic components of the torsion pendulum, possibly due to deliberate misreporting by these folks, who didn't bother to explain what was going on in the first experiments they hyped up. Since they didn't bother to do a any systematic analysis of the effect on the first run, to vary air-pressure, look at air flows with dust, whatever, or if they did this they didn't bother to admit their initial error, this is not particularly honest experimental work, and there's not much point in talking about it any more. These folks are simply wasting people's time."
http://physics.stackexchange.com/questions/23725/is-the-emdrive-or-relativity-drive-possible
In conclusion, they did a really really bad experiment and got a bad result. Wow!
The other thing you get when you generate RF is eddy currents in nearby materials, generating magnetic fields from nearby materials. Nothing to see here, move along...
Well the tests keep showing the damn thing works! Maybe it's just magic.
If it is based on magic, then scientists are ill prepared to detect that. Instead you need a professional magician, who is skilled in the art of deceit and deflection. Is James Randi available?
Any light bulb and mirror can create momentum, with no propellant expended. SF writers have known for a long time that, in principle, electromagnetic effects like powerful lasers can create thrust.
By expelling photons, which are then acting as a propellant.
--
JimFive
Please stop using the word theory when you mean hypothesis.
https://xkcd.com/1404/
There's nothing currently practical about it. It's in the experimental stage. If we had a spacecraft flying around on one of these, I'd be much more confident. The last time an observation violated the laws of physics like this, it turned out to be a loose cable connection.
By Noether's theorem, if we're violating the law of conservation of momentum, the laws of physics must vary from place to place in the Universe. (Unfortunately, I don't understand general relativity well enough to generalize this.) If this actually works, we're going to need a rewriting of physics comparable to Special Relativity. We definitely should push ahead with testing this thing, although I still think it's going to turn out not to be a reactionless space drive.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
More like tests keep showing that it IS working, and nobody is sure why. Either the problem is with the test, or there's something else happening that we don't understand, but either way, nobody is sure yet what's going on.
I think it's likely that the test is faulty, but they need to figure out why or how the test is faulty.
Area man refuses to accept that something was demonstrated by a scientific experiment can possibly be true - insists that his knowledge of science as an 8 year old was more advanced than that of actual actual specialized scientists.
That's just silly. The people reporting this observable phenomenon do not claim to understand why this happens - in fact the point of the article is that we should strive to understand why this works.
Just because YOU don't understand why this works doesn't mean that they are claiming to be violating the conservation of momentum - especially since they are not. Most especially because there's a clear expenditure of input energy - a grossly inefficient (it would seem) one.
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Why do you keep saying this? They aren't giving an answer. They don't understand why it works, they clearly suggest that we should figure out why it does...
You seem to be building a straw man argument so you can rant about the COM.
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If I were to peer-review a paper on this, I would insist on a plausible physical explanation for the claimed measurement. The burden of proof is on them: they are making a truly extraordinary claim, one that, if true, would entail revising all of physics from its very foundation.
When somebody sounds like a total fucking crackpot, they almost always are.
You might have missed high temp super conductivity entirely then. The phenomenon was measured and replicated in many labs - but it was at least a few years before any plausible theory came out - and 20 years on we do not have firm agreement on the cause.
Except he in involved with all the tests and sets the parameters. This has been replicated by 3 different teams using their own manufactured cavity chambers and one of those teams works for NASA. Just a wee bit of a difference.
Or, rather than all of physics being wrong, maybe they have an erroneous measurement setup.
That doesn't mean you shouldn't investigate anomalous measurements. But at this stage you shouldn't be writing fluff pieces with page after page of how much your new technology will change spaceflight. You should be publishing a paper with a name like "Measurement of anomalous thrust in a microwave apparatus operated in a hard vacuum" and trying to avoid the media insomuch as possible - and when you need to talk with them, trying to explain "we don't know what's going on... we have some theories but they're controversial... we need to do more testing." etc.
Sigur RÃs: I didn't know that Heaven had a rock band.
If you learn of an alleged unusual phenomenon, and you have an immediate rigid response, please stay away from science. Go into religion or politics. The only appropriate response is "Hmmm interesting, let's look into this". Human knowledge is always provisional. Careless, absolute, knowledge claims are the currency of religion.
Nope, they're not. It's generating three orders of magnitude more thrust than would be generated merely by the momentum of emitted microwaves.
So it's powered by a typical Comcast bill
Table-ized A.I.
"If I were to peer-review a paper on this, I would insist on a plausible physical explanation for the claimed measurement." That's stupid. Providing proof that something interesting is happening and repeatable is viable science all on its own.
If they simply wrote a paper saying "we noticed an anomalous force in this experimental setup, and we don't understand why", then nobody would have a problem with it. They're not doing that. They are claiming that it can be used as a reactionless propulsion system, a claim which is entirely incredible without a solid physical theory to justify it.
The expulsion (should that not be expulsion or something?) are micro waves ...
hence the name: EM drive.
What you are describing is a photon drive where photons are the propellant. But the fine article explains:
After consistent reports of thrust measurements from EM Drive experiments in the US, UK, and China -- at thrust levels several thousand times in excess of a photon rocket, and now under hard vacuum conditions -- the question of where the thrust is coming from deserves serious inquiry.
The reason I don't believe it is real is the same reason I don't believe cold fusion is real. They put in metric ton-loads of energy and measure a very small effect. They say they will need to increase the efficiency by many orders of magnitude to create a practical device. I say they probably made a mistake somewhere and the tiny effect they measured is either noise or due to something else they haven't yet accounted for.
We don't see the world as it is, we see it as we are.
-- Anais Nin
Before we put it on the ISS, let's start by putting one on a cheap metal box with some dumb sensors and communication equipment on it. I'd rather test this on something that doesn't have somebody living in it.
You might have missed high temp super conductivity entirely then. The phenomenon was measured and replicated in many labs - but it was at least a few years before any plausible theory came out - and 20 years on we do not have firm agreement on the cause.
Poor comparison. High-Tc superconductivity was a demonstration of a known phenomenon (zero resistance current) under new physical circumstances. A better comparison might have been the photoelectric effect, which really had no explanation under the then-known laws of electromagnetism. The explanation for the photoelectric effect in fact did require a deep and radical revision of the basic laws of physics: Quantum Mechanics. Sometimes this happens.
These guys have not measured something which clearly requires such a revision of physics, yet they are full of breathless claims about its significance. Red flags all over the place.
"If I were to peer-review a paper on this, I would insist on a plausible physical explanation for the claimed measurement." That's stupid. Providing proof that something interesting is happening and repeatable is viable science all on its own. I've read quite a lot of highly-respected papers from highly-respected people in highly-respected journals which did nothing other than document a pattern of behavior without explanation. In fact, most scientists I know will say they rarely ever really think they know *why* something happened, but that doesn't stop them from wanting to know. Some things get thousands of perfectly cromulent papers written prior to anyone really having a firm grasp on the "why" - hell, if you have the "why" then you probably have the last paper that will ever need to be written on the subject. Even farking *gravity* is still a bit of a mystery. We're pretty good on exactly *how* it works, but the *why* that you insist is necessary, for even something we all pretend to understand, isn't really yet known.
Dr. Schweitzer will tell you the same thing. She found what looked like soft tissue in a T-Rex bone back in 1993 and published her results, in shock herself and knowing that it was impossible to really be that. She checked and rechecked to rule out contamination and other causes, never finding one. The entire scientific community though refused the possibility it was soft tissue because Schweitzer couldn't explain how it could be preserved. By the year 2000 though she'd found the same results from enough other fossils that she's finally getting some traction and it's now starting to be taken by others as true, and there is new research now into how the heck it has happened. Not many people would carry that a decade.
So you're one of the swags that believes all physics is right? Puh-leeze lets make up some more shit like dark matter an dark energy to make it so!
Any time you have an assumption based on physical laws, it must be able to be tested and measured and accounted for and predicted, and if the prediction based on those physical "laws" differs from what is observed, one must first, check their math for errors, check their method of measurement and if all of that checks out to be accurate to ask questions along the lines of: "What are the implications of what we have observed and measured and verified here?" or as Einstein asked "What would the universe be like if it operates the way we have observed it to here?" This is what allows science to side step conundrums based on incorrect assumptions and asking poorly worded questions that lead research astray and into asking the "Wrong questions". Before Einstein, the question was "Why does light always seem to be moving the same speed regardless of the point of view or movement of the observer with respect to that light, when we know that it can't?" That is a poorly worded question, because it assumes that what we know, but that we are unable to use to explain what we observe is correct, when it is likely it is not correct. This is why I hate the term "Laws of Physics" because it implies that they way we understand the universe is the way it operates, when these "Laws" are just our shorthand for documenting and understanding what we observe. This is also not to imply that when someone says "This breaks the laws of physics!" that they are pulling a James Dean, rebel attitude and getting something for nothing, it really, most likely means someone does not fully understand the thing they are dealing with and some corrections will be needed to science books of the future. As HAL9000 said in 2001, A Space Odyssey, "The problem can only be attributable to human error."
You might want to look at this nice summary from Reddit of all the experiments performed in China and at NASA about these drives:
The FACTS as we currently know them about the EmDrive and Cannae Drive
How come Slashdot never gets Slashdotted?
That is pretty close to what is going on.
There are now several experiments which confirm the production of thrust, many efforts to falsify the results, and a few efforts to come up with a theory which explains what we are seeing. There may be another test or two on the ground, but the first real space trial is likely coming soon. The only real way to be sure is to launch one and measure the dv.
I had the same thought they did initially, which is that convection of air was responsible for their thrust. That will not happen in vacuum, so that idea is right out.
This is a very promising experimental result, following several other very promising experimental results from different labs. I would say there is now serious evidence that this works, or at least that there is more to it than we can easily explain given our current understanding of physics.
I'm a signature virus. Please copy me to your signature so I can replicate.
Difference:
Pons and Fleischmann announce, others try to reproduce, fail.
vs.
British engineer announces, China tries to reproduce and succeeds, NASA tries to reproduce and succeeds. Supposedly BAE Systems, EADS Astrium, Siemens and the IEE have also gotten positive results.
Of course, there is still a lot of work to be done to see if it isn't some other effect contaminating the data.
On the actual surface of Alpha Centauri? Probably not.
Their measured force is far greater than radiation pressure could explain (around 1 newton /kW now, expected to be 500-1000 newtons per kW with some refinement if their current theories are correct), and it was not tested in sunlight as far as I know.
It cannot be simple radiation pressure, of this NASA is certain.
I'm a signature virus. Please copy me to your signature so I can replicate.
"They" are many different people here. The experiment has been reproduced by, what, five different teams all across the world by now? As I understand, only the guy with the original idea is making outlandish claims; everyone else is just trying to figure out what the hell is going on.
One observation that the other teams did make is that the observed output seems to be scaling nonlinearly with input, which implies that there's a peak of efficiency. They have a model that tries to guess what that is, which seems to be consistent with the results to date. If that model is right, the peak efficiency is very high - high enough for practical uses not just in space. That is speculation, of course, but it's strictly fact-driven (and comes with a very big "if" - if the engine actually works by itself).
The rest of it is the usual journalist pop sci.
Note that this is the fifth experiment so far that has reproduced the effect (and every new experiment tries to account for some explanation that could possibly invalidate the previous one; e.g. for the last one, they ran it in vacuum).
Wrong.
Conservation of linear momentum is most certainly NOT derived from Thermodynamics.
Conservation of linear momentum is a mathematical consequence of translational symmetry - in other words, momentum is conserved if the laws of physics are invariant in space. Similarly, angular momentum is conserved if the laws of physics are invariant by rotation.
First of all, you need to be careful of your pronouns. "They" the inventor of the device is mostly just saying it can be used to replace satellite thrusters, which would be a huge weight saving (no need for maneuvering or stationkeeping fuel). "They" NASA are saying that, *if* it scales up the way their current model says (yes, they have one), then after a lot of refinement and with a nuclear reactor powering it, this thing could produce hundreds of Newtons of thrust at a scale that would be feasible for spacecraft propulsion. Some people have worked out, based on the predicted thrust and the likely mass of such a craft generating that thrust, that it can be used to reach Alpha Centauri in under a century. The first of these is an obvious use case for anything that can generate a tiny thrust for a long time. The second is a straightforward application of the current-best (though probably still in need of major refinement) model of thrust detected to power input, which has been measured. The model is a guess, but the fact that more power = more thrust has been demonstrated; it is, as you say, a concrete fact. The third thing - the starship drive - is simply once again a straightforward application of the results of the model. Nobody is saying that the EmDrive makes starships possible, just that if we *had* a starship, and if it was propelled by an EmDrive that corresponds to the current model of power output, then it could reach Alpha Centauri in N years. That's simple mathematics; you can do the same for chemical rockets or solar sails or any other form of propulsion that works in vacuum.
Second, I don't know why you're calling the idea of scaling up an observed result "delusional". The first Wright Flyer could barely get one person off the ground for a few seconds, flew slower than a horse could run, and was so fragile that it was shattered by a gust of wind after only four flights. But, once you've demonstrated that it *works* - that heavier-than-air flight is actually possible (which should have been obvious to everybody, given that birds and bats and insects exist, but plenty of people thought humans would never achieve it) - then scaling that up to WW2 bombers was pretty straightforward: more-powerful-for-their-weight engines (the Wright brothers had to design their own engine; the existing ones at the time didn't have enough power to weight ratio), stronger-for-their-weight materials, lots of refinements to the design (the Wright brothers pioneered the use of wind tunnels and used them to fix several significant errors in the equations that govern aspects of flight like lift, but their first Flyer was still a very primitive design with many compromises or outright flaws), and other simple, iterative improvements. Breaking the sound barrier was a bigger challenge than getting across the ocean in one flight, in terms of theoretical challenges. All this from a craft that could barely get one guy a few hundred feet down a beach.
If somebody had watched the Wright Flyer and said "one day, people will be able to fly to Europe from the US in less than a day" would you have called them "totally delusional" too?
There's no place I could be, since I've found Serenity...
The more reproductions without someone figuring out what's wrong with the test the more likely it is that it's not the test that's wrong.
This engine is interesting on many fronts, the most important of which is it appears to violate what we know about conservation of momentum and IF it does it's going to actually point to some fundamental constant or principle of the universe that we've missed as long as it's not an experimental error. This is a big hurdle to take so it's going to take a LOT of evidence there is no mistakes with the test or engine.
Could be pretty cool if it turns out real. We won't need to ever worry about fuel for satellites and all you would need to travel to mars or even Pluto or even another star would be an energy source that would last the length of the journey. I wouldn't be surprised to see the DOD put one of these into space ASAP to find out if the work, it would revolutionize spy satellites if they don't have to worry about propulsion fuel.
Leaving aside the fact that light has momentum and therefore is sufficiently "physical" a propellant for this example, and the fact that this thing produces orders of magnitudes more thrust than a few Watts worth of photons could impart, you're still missing a really key problem:
You can impart momentum on a mirror by shining a flashlight on it, but you can't impart momentum on a sealed box by having a lit flashlight *inside* it!
The EmDrive uses a sealed cavity. There's nowhere for any propellant to come out, even if there were any!
There's no place I could be, since I've found Serenity...
I can attest that it is not thermal. It works in a vacuum. It works in a Faraday cage and it works when you reverse the device (the thrust reverses).
Well in that case, I've got plenty of Comcast bills to donate. They just need to be paid in full.
Life is not for the lazy.
It took me years before I came to the conclusion that I have no clue how high temp super conductivity works. We've got some ideas that match what happens in one material and then another material that couldn't possibly conduct with that theory goes and does it. I'm no expert but I've been following it for a few decades and made up and examined some of the cheaper to fabricate materials.
There are several medications doctors prescribe although they and even the researchers that invented them don't how or why they work.
obligatory, something something land at night.
Its not easy to measure 50 micro-newtons of force when you change a power level by 50 watts.
Currents cause magnetic forces. Things get hot and outgas producing thrust. RF power cables get hot and distort causing a force.
Think about it. The device weighs something like 5Kilos. That is 50 newtons gravitational force. So a 1 micro-radian tilt will cause a 50 micro-newton force. Walking across the lab floor could cause that amount of deflection. If the chamber is 1 meter across, a 0.1 degree temperature change on one side of the chamber (from a nearby power supply) could cause that much tilt.
There of course could be force just from photons - but that is a simple and well understood photon drive - known for at least 50 years now - basically a light-sail.
This is a very difficult experiment to do correctly, and they have not published in enough detail.
Meanwhile: conservation of momentum has been tested under conditions ranging from ultra-cold gas atoms to 100GeV particle collisions, to orbiting neutron stars. The RF fields they use are very modest. At SLAC we run hundreds of megawatts, not 50 watts. We have superconducting cavities where we easily see the deflection caused by the momentum in the microwave fields - operating at many thousands of times higher power than this experiment - we see nothing unexpected.
So: Difficult experiment. No unusual physical conditions. Apparent violation of one of the most carefully tested conservation laws in all of science.
It it literally more likely that the sun will not rise tomorrow (since that is also based on conservation of momentum) than that this experiment was correct.
It is very hard to believe that they are going to send a propulsion system into space without a clear understanding of how it works.
We send drivers on the road every day who don't have a clear idea how cars work.
Knowing how something works is nice, but not knowing how it works won't diminish its utility, so long as it *does*.
We use gravity daily to generate hydroelectric power. Ask a group of physicists how gravity works. We have the math for it, but we don't have the story of it. Either way, the lights come on when the water weight is converted from potential to kinetic energy, and we are still damned if we know the mechanism of conversion. If we did, we'd al be riding around on hoverboards.
Conservation of linear momentum is a mathematical consequence of translational symmetry - in other words, momentum is conserved if the laws of physics are invariant in space. Similarly, angular momentum is conserved if the laws of physics are invariant by rotation.
And energy is conserved if the system is invariant over a translation in time.
Hooray for Emmy Noether.
If it weren't for deadlines, nothing would be late.