Final NASA Eagleworks Paper Confirms Promising EM Drive Results (hacked.com) 477
An anonymous reader quotes a report from Hacked: Earlier this month Hacked reported that a draft version of the much expected EmDrive paper by the NASA Eagleworks team, had been leaked. Now, the final version of the paper has been published. The NASA Eagleworks paper, titled "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum," 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, a prestigious peer-reviewed journal. The paper will appear in the December print issue of the journal. The final version of the paper is very similar to the leaked draft. In particular, the NASA scientists confirm the promising experimental results: "Thrust data from forward, reverse, and null suggested that the system was consistently performing at 1.2 +/- 0.1 mNkW, which was very close to the average impulsive performance measured in air. A number of error sources were considered and discussed." The scientists add that, though the test campaign was not focused on optimizing performance and was more an exercise in existence proof, it is still useful to put the observed thrust-to-power figure of 1.2 mN/kW in context. "[For] missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2 mN/kW performance parameter is over two orders of magnitude higher than other forms of 'zero propellant' propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the 3.33--6.67 uN/kW (or 0.0033--0.0067 mN/kW) range."
In other words, a modest thrust without having to carry fuel can be better, especially for long-distance space missions, than a higher thrust at the cost of having to carry bulky and heavy propellant reserves, and the EmDrive performs much better than the other "zero propellant" propulsion systems studied to date.
If confirmed, does this make it realistic? (Score:4, Informative)
What's the usual format of an EM drive? Does it go on a satellite for maintaining orbit instead of a chemical thruster that'll one day run out of fuel? On an interplanetary probe for long-term acceleration, like solar sails might? How big should it be for useful propulsion, and what levels of power does it require -- given that heat dissipation is a perpetual issue for small spacecraft?
Re:If confirmed, does this make it realistic? (Score:5, Funny)
What's the usual format of an EM drive?
Large arrays of them go on the back of our Terran Battleship to propel them out into the darkness as they bring the Light of Mankind to a savage and ignorant galaxy. Until we find someone smarter than us.
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Large arrays of them go on the back of our Terran Battleship to propel them out into the darkness as they bring the Light of Mankind to a savage and ignorant galaxy. Until the robots running the ship rise up against their masters and return to destroy us all
There, fixed it for you
Re:If confirmed, does this make it realistic? (Score:4, Insightful)
The most implication of experimentally confirming these observations would be for our fundamental physical models [wikipedia.org]. Nobody can really say what it means, but it is potentially as important as the discovery of spectral lines [wikipedia.org], which was instrumental for the development of quantum theory.
As with most discoveries in fundamental physics, the actual applications are often unpredictable and rarely match the initial expectations. If anyone tells you they know, they are talking out of their asses.
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You vastly underestimate the situation. The EM drive could be the Michelson-Morley experiments of the 21st century. If you don't recognize that, those are the series of experiments whose "inexplicable" data led to Einstein's discovery of relativity.
Re:If confirmed, does this make it realistic? (Score:5, Insightful)
While the OP did indeed ask for practical propulsion applications, the implications of a change in physics theory is enormous, as his example illustrates quite well.
Spectral lines led to the realization that energy is not continuous, but discrete in very small units which can interact with matter, and by inverting that principle, small changes to matter can result in large changes to energy. That directly led to the theory behind semiconductors, enabling transistors and other solid-state electronics, ultimately leading to the entirety of modern electronics technology.
Similarly, verifying a repeatable violation of the laws of physics means that those laws are inaccurate. By refining the theory to fit the new observations, we can also revisit our assumptions about what is possible using electromechanics. To address OP's question, energy, not fuel, becomes the limiting factor in propulsion. That in turn alters the theory of rocketry, which affects the limits of human expansion, providing new areas of study for anthropology and sociology.
However, the scope of affect also lies beyond rocketry. If EM can produce thrust, we may be able to miniaturize the device to a nanotechnology scale, as a new tool for nanomachines. As one example off the top of my head, we may be able to produce self-controlled materials that change shape by rearranging microscopic structures, similar to how animal muscles work by moving actin and myosin molecules.
In short, the actual application of any discovery is the increase in understanding of how the universe works, and from that we can derive advances in technologies.
Re:If confirmed, does this make it realistic? (Score:5, Insightful)
Are you serious? If the EM drive works we are at the gates of a major revolution in Physics (as in 'our understanding of Physics'). First we should have to understand how it works, tinker with it till the smallest-lightest-efficientest designs emerge. In parallel, other people would be trying to determine WHY it works. That's a much bigger task, that requires a rewriting of most Physic's textbooks. When we have a new theory that explains the EM drive, then probably still better drives can be designed, perhaps using other kinds of radiation.
What I'm driving at, is that discussing how possibly adequate or inadequate this EM drive is to space travel is like discussing the usefulness of electricity when good old Thales started rubbing amber pieces against animal skins.
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>Are you serious?
Yes. By examining its practicability in the current format, we can guess at how much improvement is still on the cards, or remain in the deck, for various aspects of the technology. Changes to the fundamental sciences are so impredictable as to not consider; so I'm assuming they're precious to basically everyone for exactly the reason that we now have nuclear power and what-not despite at first only having extremely huge bombs.
Re:If confirmed, does this make it realistic? (Score:4, Interesting)
Umm, you realize we needed to make nuclear power plants *before* we could make the bombs, right? Granted they were designed specifically to enrich the natural fissiles into weapons-grade isotopes, but the reactors still came first.
And no, looking at the current state of a technology based on physics that we don't yet understand in no way helps us understand how much improvement that technology may undergo. At best it gives us a glimpse at what it might enable.
In that context though, the best initial application is likely to be deep space probes. Satellite maintenance might get included as well, but that's more a convenience than an enabling technology - there's already orbital refueling vehicles under development. Deep space though - that's where constant low thrust acceleration pays off big time.
From what I can find, current RTGs for space applications top out at about 5W/kg. Assuming a 1kW RTG is half the total mass of the probe, that gives us a 400kg probe with 1.2mN of thrust using the current unoptimized EM drive tested. That translates to 3um/s^2 of constant acceleration. You're not going see much change right away. Starting from rest, in one minute it will travel a grand total of 5.4mm. But acceleration adds up:
Displacement as a function of time:
1day: 11km. 1 week:550km 1month:10,000km 1 year:1.5Mkm (yay, 0.5% of the way to Mars!) 10 years: 150Mkm (Wait, we're still not to Mars?). 100 years: 1.5Bkm (3x the distance to Pluto). 5200 years: ~4.2 light years(we've reached Proxima Centauri!)
So yeah, with current technology it's not actually much good for deep space probes, and I haven't even factored in the losses of climbing out of the sun's gravitational well. If you're operating close enough to the sun to use solar though you can up your power to 300W/kg (near Earth orbit), and assuming the same 50/50 power to payload ratio that will get you ~60x the thrust (and thus 60x the distance per unit time). Then the numbers look a bit better: You might get most of the way to Mars in a single year for example. And more importantly be able to turn around and repeat the journey indefinitely.
So I suppose inner-system scouting probes and perhaps interplanetary cargo transportation could be early applications. And if optimizations could yield a 10-fold improvement in engine thrust/W, well then things start getting really interesting. Travel to and from Mars in a month, with no need for refueling? That's the stuff science fiction is made of.
Re:If confirmed, does this make it realistic? (Score:5, Interesting)
False. [wikipedia.org]
Trinity, the very first man-made nuclear explosion, used Plutonium from the Hanford Engineering Works, created in the B, D, and F reactors. You do know that Plutonium doesn't exist in nature, right? It's either created in a reactor via neutron bombardment of U238, or in a cyclotron.
More than that, the Chicago Pile [wikipedia.org] was the first man-made self-sustaining nuclear reaction (in 1941), and the basis of all reactor design that followed to support the Manhattan Project, which made bombs detonated in 1945.
Reactors very much came before the bombs.
Re:If confirmed, does this make it realistic? (Score:5, Funny)
It's very simple, instead of being inefficient like a regular rocket engine and moves the rocket in space, it simply allows the rocket to be stationary and it moves the universe.
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There is no rewrite of any single text book necessary.
There is a small chapter added to quantum mechanics, that's it.
Re:If confirmed, does this make it realistic? (Score:5, Insightful)
Seriously. Top scientists don't know how it works yet. What makes you think you have the answers?
Re:If confirmed, does this make it realistic? (Score:4, Informative)
If it works it violates conservation of momentum, which is just as big a deal as violating conservation of energy.
Re:If confirmed, does this make it realistic? (Score:4, Insightful)
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Yep, because we don't have any forces exerting mysterious action at a distance. Gravity, EM fields, etc. only operate through physical contact...
Assuming it works, and at this point there's enough evidence to seriously entertain the possibility, figuring out the "how" will undoubtedly be headline news among scientists. At the least it will point out heretofore unexpected loopholes in our assumptions. At most it could shake the foundations of physics as thoroughly as did Quantum Mechanics or field force th
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I can see it now. After a few more confirming experiments, we design the largest EM motor we can and boost it into orbit. We aim it toward Jupiter and flip the switch. Said EM powered craft shoots off at unexpectedly relativistic speeds.
Meanwhile, the Earth has stopped rotating on its axis...
Oops!
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Except all inertial reference points in the universe are equally at rest and speed is an observer-based phenomenon. If you can expend X energy to get Y change in kinetic energy, then all you have to do is observe the same thing while passing at a much higher speed in the opposite direction to see that you're actually getting a much larger change in kinetic energy for the same expenditure of energy. Either it violates physics at all speeds, or it doesn't.
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Just because you don't understand how it works doesn't mean it's instantly a "perpetual motion machine". I sincerely doubt it's creating energy from nothing.
No, it's creating momentum from nothing.
Seriously. Top scientists don't know how it works yet. What makes you think you have the answers?
No, any scientist with two neurons to rub together knows it doesn't work. Newton's Third Law makes me think I have the anwers.
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It's only been a couple of decades that we've recognized that we're unable to even detect 85% (or maybe more) of the mass in the universe at less than the galactic scale. I think that there might be one or two things out there that we don't understand yet.
Re:If confirmed, does this make it realistic? (Score:4, Insightful)
Black holes emitted radiation back in the 19th century. Did you know that?
Oddly enough, nothing in pre-20th century physics allowed for that to happen.
It is just barely possible we're about to begin a 21st Century revolution in physics comparable to the one(s) in the 20th Century (Relativity, QM).
Or not. But till you run the experiment (noone is stopping you, you know), your repeated "it doesn't work" comes across rather like a child putting his fingers in his ears and chanting "I can't hear you" over and over....
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Just because you don't understand how it works doesn't mean it's instantly a "perpetual motion machine".
Do the math:
thrust = 1.2mN
power = 1kW
power = force * velocity
At what velocity does it go over unity?
I sincerely doubt it's creating energy from nothing.
Quite. It wculd if it worked. It doesn't work.
The paper does not state that the power to thrust ratio is constant at all speeds but simply that in the tests that were performed changing the power level changed the thrust in a linear manner. What if the cavity simply exhibits a force on dark matter? Understanding exactly how this works is going to be huge in revolutionizing physics if tests continue to verify the results.
Read the Paper (Score:3)
Understanding exactly how this works is going to be huge in revolutionizing physics if tests continue to verify the results.
I extremely doubt that. Read the paper. At no point do they consider charged particle emission. Instead they do worry about drive components becoming charged but they fix that by grounding...so if he drive was emitting charged particles it will not become charged which will let it continue to function. Since you cannot ground a space craft this explanation of the thrust would make the drive useless.
This is the problem with the paper, apart from the sloppy uncertainties, there is no investigation as to t
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This is the problem with the paper, apart from the sloppy uncertainties, there is no investigation as to the cause of the thrust. They focus only on measuring it.
How is that "the problem" ?
The first step in science is often to 'observe an effect' and then to start isolating it and measuring it.
By far the most likely outcome of this is that it will turn out to be particle emission of some sort which our existing physics can explain.
Perhaps, but then knowing precisely how much thrust is generated and along what vector etc will help us pinpoint the source and cause.
If they want to convince anyone of anything else they need to focus on investigating possible causes
So... are you still skeptical of gravity too? Because we haven't really pinned that down yet either. I mean ... we know a lot about measuring it, and its relationship to mass, and we can make predictions based on it... but (to my knowledge at le
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This is the problem with the paper, apart from the sloppy uncertainties, there is no investigation as to the cause of the thrust. They focus only on measuring it. By far the most likely outcome of this is that it will turn out to be particle emission of some sort which our existing physics can explain. If they want to convince anyone of anything else they need to focus on investigating possible causes and focus less on just measuring the thrust.
Very much so. Just measuring the thrust gives you zero indications whether you measure a real effect or an error. But this tactics of just measuring the effect without trying to explain it is an exceptionally well established characteristic of junk-science and scientific fraud. This tactics to get investor money for something that does not actually work is over a century old. And in many cases, it was not actually fraud, just very bad scientists with very big egos thinking the rules of proper scientific exp
Re:If confirmed, does this make it realistic? (Score:4, Interesting)
The paper does not state that the power to thrust ratio is constant at all speeds but simply that in the tests that were performed changing the power level changed the thrust in a linear manner.
That would be easy to test: the earth is moving continuously and changing direction all the time in a predictable manner.
What if the cavity simply exhibits a force on dark matter?
It's not dark matter if it interacts with the electromagnetic field, it's something else literally by definition.
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What does the speed of dark matter have to do with anything? As an analogy, an electric field exerts the same instantaneous force on a charged particle regardless of that particle's speed. Total force exerted on the particle will be less if the particle is moving past quickly, but if there's a continuous flow of particles arriving to replace the ones departing then that doesn't matter in terms of the reactive force on the field generator. All you really need to know is the average particle density within t
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Those worthless morons at NASA apparently disagree with you. As would the British, Chinese and Germans.
Define "work" (Score:3)
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And that is the kicker: It would have to overturn an exceptional amount of well-established physics and this effect must be tied to very special circumstances, because otherwise it would have been observed before. This makes for an exceptionally low probability of an actual effect and a very high probability of a subtle measurement error.
Hell, with the tiny thrust they observe, it could even be an effect of the current flowing into the grounding, maybe combined with a skin-effect or some resonance effect in
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The EM drive obeys the law of conservation of energy.
it does not. Consider the EM drive working as claimed, 1.2mN/kW. Now consider it travelling at 1000km/s. How much energy is going in (1kW), and how much is the kinetic energy increasing by at that point (force*velocity).
That's how and where it goes over unity.
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If it did, it implies perpetual motion machines are possible, because the EM drive goes over unity.
Does it? That looks like a lot of input power for not a lot of thrust.
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That looks like a lot of input power for not a lot of thrust.
The key though is that it's not enough.
Once you hit 1000km/s, the power increase (increase in kinetic energy per unit of time) is 1.2kW with a 1.2mN force. But the power in is only 1kW (it claims to get 1.2mn/kW), so it goes over unity.
Note that 1000km/s is fast, but it's not relativistic, so you can stick with classical mechanics and still get a decent answer. The reason for this is that k.e. depends quadratically on speed, but the power in is in
Re:If confirmed, does this make it realistic? (Score:4, Insightful)
You appear to have committed an error, here. That P=W/t converts to P=fv implies nothing about being over unity past a certain speed, or under unity below it. It's easy to see how a layperson's overreading of the words would yield such a view, however.
Considering your views on social issues, I'm unsurprised.
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Except that all objects in the universe are equally at rest.
Theoretically you could harness this to the rim of a wheel traveling that fast to generate power, except that we don't actually have much theory, nor even data as to how this operates, so essentially no basis to assume *anything* is possible until we've characterized it's behavior better.
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Re: If confirmed, does this make it realistic? (Score:2)
Only if you can somehow make a device to convert the motion into electricity with basically close to zero losses, which is well outside current or even believed to be possible engineering. You are making a classical physicists mistake of assuming a lot of real world effects can be put to zero when they can't. Basically at the moment it is impossible with the known devices to build a machine that could generate enough power from the generated motion to keep the device moving. That is q is still way less than
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Obligatory xkcd. (Score:2)
https://xkcd.com/669/ [xkcd.com]
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The current test article appears to be the size of a 10 gallon bucket. With all associated hardware to drive the chamber, all hardware could fit neatly inside the volume of a 50 gal barrel.
Minus the power supply, this is able to supply the stated specific impulse of the article.
The mass of the test article and associated hardware is not given, and above estimations for volume come from photos of the test apparatus.
Re:If confirmed, does this make it realistic? (Score:5, Funny)
What's the usual format of an EM drive?
NTFS.
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Yes and Yes. and if we find a way to make a LOT of electricity, 10,000,000Kw of power into one will produce 1000N of thrust assuming a linear scale up.
What is needed is to see if the drive will actually scale up.
The other thing is, now that it is proven to actually work, refinements can be made to the whole design to increase efficiency that may give us even more thrust per KW of electrical energy.
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I have a question: What the smurf does this mean? Seriously?
Are we talking about a ground-based laser pushing it? In which case, the idiocy of comparing a system that you have to lift into space, in which every gram is critical, versus something here that can be hooked up to the power grid, is beyond belief.
Are we talking about a solar sail
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"The 1.2mN/kW1.2mN/kW performance parameter is over two orders of magnitude higher than other forms of “zero-propellant” propulsion, such as light sails,"
I have a question: What the smurf does this mean?
They're talking about technologies that use no reaction mass, not that use no fuel.
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What's the usual format of an EM drive?
Half-assembled in a shed out back, because the fucking thing is total snake oil.
Re:If confirmed, does this make it realistic? (Score:5, Insightful)
It's Steorn all over again.
Apart from the open process and independently verified results
Not Verified At All (Score:4, Interesting)
Apart from the open process and independently verified results
This is the problem though the results are not at all verified. Have you actually read the paper? It shows an appallingly low level of scientific methodology for a paper claiming to observe a phenomenon which violates the currently know fundamental laws of physics. For example at one point it is quoting a fit to 7 significant figures without giving any uncertainty range which suggests a position accuracy of ~1nm which is less than the size of an atom. I am unconvinced that they measure the position this accurately. While this ultimately will not affect the result they claim it shows sloppy practice which is not a good for inspiring confidence.
However most importantly when considering errors at no point do they see to consider charged particle emission as a source of thrust. They do worry about the components becoming charged which they say they fix by grounding but if you are emitting electrons grounding the engine just ensures that there is no charge build up which will allow the engine to continue to operate. Since you cannot ground a craft in space the charge would build up their until the engine's thrust stops.
So it's great that they publish their results openly but what there is to see there in no way inspires any confidence that they have observed some new, fundamental physics phenomenon. Instead of engineers they need to get some scientists involved because the paper shows a total focus on simply measuring the thrust and zero scientific investigation to investigate the cause of the thrust.
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There's no problem with conservation of energy - the thing is plenty power hungry.
Re:Not Verified At All (Score:5, Informative)
Your entire post is nonsense. You're "not even wrong".
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Your constant-thrust assumption can be what is wrong here.
On the other hand, if thrust goes down when speed goes up, then what use is that drive?
I also wonder how the other 'fuel-less' thrust engines behave in this respect. Do those go into 'over unity'?
Clearly not, I would say. So why would this one...
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Can I suppose that you're not sure about the assumptions regarding:
Well...
constant thrust
They report thrust versus power. Either thrust decreases with speed which implies that absolute position exists or it decreases with time. That implies either that physics changes over time, or some consumable is being used up.
If it's the latter then it's just a rocket.
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which suggests a position accuracy of ~1nm which is less than the size of an atom
Might want to double check that, I'm pretty sure atomic radii are measured in picometers.
Re:Not Verified At All (Score:4, Insightful)
which suggests a position accuracy of ~1nm which is less than the size of an atom
Might want to double check that, I'm pretty sure atomic radii are measured in picometers.
They can be measured in any unit you like, but the typical size of an atom is in between 30 and 300 pm. So GP is wrong: 1 nm is greater (not less) than the size of an atom, but it's in the ballpark.
https://en.wikipedia.org/wiki/... [wikipedia.org]
Re:Not Verified At All (Score:5, Insightful)
Instead of engineers they need to get some scientists involved because the paper shows a total focus on simply measuring the thrust and zero scientific investigation to investigate the cause of the thrust.
Yeah I know. What an absurd thing to do in a paper titled: "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum"
Have you ever considered that there may be other teams doing research on this an this just happens to be the first paper out? Damn them for not doing everything at once and reaching all conclusion at the same time.
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Let's say that "usual" is a designation rather than reference to prior application. What would it look like based on current experiment, scaled up to a degree where it'd be useful outside of the atmosphere and fitted for space?
How big is an EM drive (Score:2)
What would a spacecraft operating an EM drive at peak efficiency look like? Say, a Star Wars Star Destroyer going from low-earth to geocentric orbit in 'reasonable' time (30 minutes). Would the relative size of EM engine to Star Destroyer body be 1:10? Or 100:1?
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At least a million times as big as the ship (Score:2)
> Say, a Star Wars Star Destroyer going from low-earth to geocentric orbit in 'reasonable' time (30 minutes). Would the relative size of EM engine to Star Destroyer body be 1:10? Or 100:1?
Without actually doing the math, the drive would be at least millions to trillions of times bigger than the ship. There is so little thrust that it's extremely difficult to tell if there is any thrust.
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What would a spacecraft operating an EM drive at peak efficiency look like?
Stationary.
vaporising metal? (Score:5, Interesting)
They say that they have looked at outgassing, and assumed that its not relevant due to slow temp rise not producing rising force. But that does not cover possibility that the electromagnetic resonances are somehow vaporising and ejecting structure at much higher speeds. At .0012N thrust with 1kW input (and 100% efficiency) a rocket would need exhaust velocity of 1.6e6 m/s and consume around 0.8ng per second - damned difficult to weight with required sensitivity and hard to spot except by looking for evidence in the gases within the chamber as metals will condense out quickly.
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But that does not cover possibility that the electromagnetic resonances are somehow vaporising and ejecting structure at much higher speeds.
Ah yes, the "I'm sure I thought of something the experts didn't" response.
Metal doesn't just vaporise. It takes a lot of energy to free atoms from a metal lattice, which would require the metal to be visibly glowing hot, which is not what happens in the drive.
Any idea how it works? (Score:2)
Do we have any idea how this works? And do we know if we will be able to optimize this at all to get better performance?
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One proposed theory is that it works by exploiting unruh radiation. That explanation relies on the premise that inertia is quantum in nature, and so there can be anomalies between discrete quantum levels of inertial interactions.
https://arxiv.org/abs/1604.034... [arxiv.org]
The author has proposed that this mechanism may also be responsible for some other observational anomalies.
http://phys.org/news/2011-07-g... [phys.org]
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Do we have any idea how this works?
It doesn't. It's a horribly difficult experiment to measure and IF EM drives worked then they are effectivly perpetual motion machines, in that you could build a free energy device out of one.
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The glib answer is "go fast".
power = force * velocity
So if v is high enough anf f is fixed (as claimed with the EM drive) then eventually the kinetic energy power will go over the power in, unless it's the much lower thrust of a photon drive.
It's not practical at 1.2mN/kW, but that's irrlevant to the physics.
Re:Any idea how it works? (Score:5, Interesting)
The fundamental problem with this experiment is that it appears to violate conservation of momentum. This violation is not something that can be discarded easily: it has been confirmed directly and indirectly in millions of experiments over decades.
Momentum conservation is also a cornerstone of quantum field theory (QFT) and it is a symmetry which survives quantization. The entire Standard Model (SM) is a momentum-conserving QFT. The SM has been confirmed to a high accuracy in particle accelerators for many years. Any violation of momentum conservation would have been quickly noticed. You cannot simply invoke 'quantum mechanics', 'zero point', 'vacuum fluctuations', etc. to explain excess thrust. Momentum conservation is fundamental, both classically and quantum mechanically.
So what about the EM drive results? There is a possibility that some new physics is at play, however it is vastly more likely that there is a systematic error which has not been eliminated. (If I had to guess I would imagine that because a large amount of RF energy is being pumped into large metal cavities, the apparatus is resting at the bottom of a standing wave potential.)
The way to finally confirm or refute this is to take the drive into space. In this case, it is almost certain that the net thrust would be equal to the momentum of the photon flux leaving the drive.
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The fundamental problem with this experiment is that it appears to violate conservation of momentum.
And conservation of energy---once it's going fast enough. It violates ALL the things.
IAATP working on quantum electrodynamics (QED) and other theories.
Out of interest, do the succession of reasons why it "works", you know: it's relativity! er no it's virtual particles! er no it's the Unruh effect! actually cause you physical pain?
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No. Those are what are called "speculation". As in "we see it working, but we have no idea why or how. But it could be..."
As to conservation of momentum/energy. They're not necessarily laws of nature, you know. As soon as something comes along that "violates conservation of...", those two rules become "special cases", just
Re:Any idea how it works? (Score:5, Informative)
It's difficult to convey to a non-physicist just how accurately and consistently quantum field theory describes nature. Physicists routinely make calculations which have lower uncertainly than the best experiments. For example the anomalous magnetic moment (https://en.wikipedia.org/wiki/Anomalous_magnetic_dipole_moment) is in agreement with theory to ten significant figures.
Physicists tend to be fairly cautious describing results, but when it comes to basic theory at energies up to a few hundred GeV we are confident that we have *all* physical effects well and truly nailed. This doesn't mean that we can always solve the equations perfectly: quantum mechanics is hard, but the equations themselves are almost beyond reproach.
It's not undeserved hubris: it's trillions of independent experiments, billions of dollars and hundreds of thousands of man-years working on the theory by lots of very smart people. The theory, quantum field theory (QFT), is simple, consistent and universal. It describes everything we can see around us, with the exception of gravity.
If you ask an actual physicist what he or she thinks of the EM drive, they will overwhelmingly say that is is highly likely there is an unresolved source of error because violation of moment conservation has never been observed and is inconsistent with QFT.
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Yes, yes it does so appear. The "math" is astoundingly simple: No matter how you state it (N's laws, in terms of Lagrangians or Hamiltonians or Stokes vectors or Grassmannian objects, and whether you use a classical or quantum mechanical basis), 4-momentum is expected to be conserved, and conserved locally. Either that deep, deep principle is wrong, in which case a gigantic new set of possibilities opens up (despite the principle appearing to work for every other observation and experiment thus far); or not
Next step NASA (Score:3)
put this on top of a rocket and have the thing move around upstairs: from low earth orbit round the moon and back should convince most people. It might take a few months to make the trip, that does not matter.
This is BIG news - If you want to know more.. (Score:4, Informative)
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Re:This is BIG news - If you want to know more.. (Score:5, Informative)
Besides your exclusion of relativistic mass increases, you are also assuming that more power isn't required as the drive accelerates. Marketing claims aside, nothing in the static testing so far indicates that, it will only show up when the drive actually continually accelerates something in a test. Acceleration without expelled reaction mass doesn't equal a violation of E=MC^2, it just means the opposite force is coming from something that isn't being expelled by the drive. What it is, is unknown now, but my guess will turn out to be something already predicted by physics.
With F=MA and E=MC^2, no matter what the source of the acceleration force, the accelerated object will start experiencing mass increasing effects and we will have to increase the thrust to maintain the same acceleration, requiring an increase in energy fed into the drive. The EM drive clearly shows a direct correlation between power input and thrust.
If your argument was valid physics, it would apply to all lower power drives including ion thrusters capable of long term acceleration. Hell, the drives on Dawn generate 80 times the thrust force for 10 times the energy of the EM drive. If anything this thing is more inefficient than the NSTAR drives.
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It's a new low, slashdot mods modding down a post like my previous one simply for stating the facts.
Besides your exclusion of relativistic mass increases,
Irrelevant at the speeds we're talking about.
you are also assuming that more power isn't required as the drive accelerates. Marketing claims aside, nothing in the static testing so far indicates that, it will only show up when the drive actually continually accelerates something in a test.
What you suggest means that relativity is very fundamentally wrong
Comment removed (Score:5, Interesting)
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> The actual methodology generating the thrust isn't clearly explained, 95% of this paper is about the testing conditions
Well duh, this paper is about proving existence. It's a physical test, it doesn't have to explain why it works. If the models don't fit reality then it is the models that are wrong, not reality. Hence the details about the test infrastructure. That results don't have to make sense, they just need to show that existing models are invalid.
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No, experimental data simply has to be consistent or anomalous. Anomalous requires investigation into possible errors. "Making sense" is a matter of interpretation, which is part of theoretical research, not empirical research.
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Later on we figure out it was magnetism and Ooge is awarded a patent for fire.
FTFY.
A nearly identical patent is awarded to Apple when they bang two iPhones together and append the phrsae "using the Internet" to their claims.
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Imagine (Score:5, Funny)
Just imagine this gizmo powered with cold fusion!
The great hope! (Score:2)
The explanations are plausible (exploitation of more of those weird quantum mechanical effects). If it works out, we get to cheat Newton, basically stealing momentum from the universe's underlying framework. Or the simulation engine, if that's what it is.
After that, it's an engineering problem to make it efficient. You'll still have to get out of the gravity well some other way, but after than, you can flit about anywhere nearly for free.
I'm trying to remain skeptical, but this really is what every sci-fi n
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You'll still have to get out of the gravity well some other way
Unless there is something about the gravity well that makes this thing work. Until we understand its principle of operation, its just a curiosity. Launch one out of the solar system and compare delta V with a continuous thrust model and see if it works. I doubt we are far enough along understanding it to make that kind of investment.
Numbers in perspective (Score:5, Informative)
Just to put the numbers in perspective. A force of 1.2mN/kW is equivalent of a force of 0.12 gram.
A Tesla SP85 has a maximum effect of 350KW. This would (in theory) produce a force of roughly 40 grams, the weight of 10 sugar cubes.
A Nuclear submarine is able to produce an effect of 100MW, giving a theoretical force of 10kg.
A medium nuclear power plant is producing roughly 1000MW, and a force of 100kg.
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Well, that's total gibberish. Who the hell modded it up? Slashdot really is on its last legs.
Some back of the envelope calculations. (Score:2, Informative)
Bearing in mind that all this is just a fun exercise, and there's no reason to believe that the 1.2 mN/kW thrust will scale to megawatts of power, here's how long it would take to get to Mars if this finding scales to a practical spaceship drive:
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If it works at all, then presumably the prototype didn't stumble on the most efficient possible design.
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That's what Mexicans often yell during hunting season in the state of New York. "Donald! Duck!".