Backstage - OOC Forums
General Discussion => The Speakeasy: OOG/Off-topic Discussion => Topic started by: Esna Pitoojee on 31 Jul 2014, 19:04
-
Welp. They've apparently got a functioning model (http://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-drive) of an EmDrive, a kind of reactionless drive that works by projecting microwave radiation into a specifically-shaped cavity. This is the third independent confirmation after the original inventor of the device, who was widely discredited as a quack.
I'm hesitant to get hype for a physics-breaking discovery after the whole FTL neutrino thing turned out to be a fluke, but if this works? The engineering and physics implications are huge.
-
These things are hard to replicate, and the amount of thrust so tiny that the experiments are notoriously easy to generate false positives. Kudos if somehow everyone else was just getting some physics basics wrong, but it's more than likely experimental error.
Momentum, she no lika not bein' conserved.
:P
-
Exactly what Silas said. I would do naughty, naughty things to get our species access to a reactionless drive but the possibility of their existence is unfathomable given everything we know about the Universe. The tests we know about (especially the Chinese one which was run on equipment not geared even remotely to detect the small thrust of the engine) are probably the result of errors in measurement. Plus, Newton may have been a crazy bastard but Conservation of Momentum has a pretty solid track record.
If I'm wrong, however, I won't just eat my words, I'll eat my words with a giant word eating grin on my face. A reactionless drive that requires only electricity means that we are going to Kerbal Space Program the shit out of this solar system.
-
I always wonder why the standard reaction to some experiment that gives results that don't align with natural laws seems to be that the scientists denounce the experiment as not to be taken serious, instead of first doing the experiment themselves to check the purported results.
It reminds one of the oft-used repressive phrase to the effect that what is not allowed (in this case, by natural law) cannot happen and which the sciences nowadays so often put at the feet of religion, while apparently using it themselves just as often. It seems to be a human thing found in all human activities.
Anyhow, my rant won't change any of that. ^_^ Maybe now that Nasa got involved the broad scientific community will start to check the results instead of dismissing them out of hand as they are 'impossible'. Then we might find out if they are or not.
P.S.: It's good to see you guys here excited about that experiment and eager to see it tested! <3 I just read the linked article and got that gut reaction over the story of this fellow who designed this 'engine' having been denied the testing of his results by a third party for so long and even as the Chinese did, that western scientists apparently still dismissed this out of hand because the Chinese design was flawed, instead of doing better.
-
I guarantee that 99% of the propulsion scientists that see this would love it to be true. However, two centuries of experimentation has confirmed the Law of the Conservation of Momentum (which is not to say that scientists would eject that stubborn bastard just as soon as they could). If this engine works I will s*ck d*ck to fund it because it would revolutionize everything from satellite station-keeping to interplanetary travel but, frankly, a couple of hundred years of observational and mathematical confirmation of Newton's Second Law stack very much in the favor of this device being a fault in current understanding of space travel.
-
P.S.: It's good to see you guys here excited about that experiment and eager to see it tested! <3 I just read the linked article and got that gut reaction over the story of this fellow who designed this 'engine' having been denied the testing of his results by a third party for so long and even as the Chinese did, that western scientists apparently still dismissed this out of hand because the Chinese design was flawed, instead of doing better.
Personal guess, the dismissal of the Chinese experiment was out of similar reasons to why people are dismissive of the notion of North Korea being able to do anything but launch a rock into the ocean.
-
I see that people have reasons to dismiss the Chinese experiment. Still, that should be motivation to any true scientist to do better and make the experiment themselves, no?
I also see that there is a track record of the Law of the Conservation of Momentum being confirmed again and again. But maybe there are ways to harmonize that law with the results of that experiment?
Yah, probably the engine doesn't work and the positive results are due to some error in measurement or somesuch. Yet, that shouldn't stop one from actually testing if that's so. I see that there is also the problem of resource allocation and there are a lot of experiments that promise positive results and where resources are probably better spent on.
But all that is different from just saying that this micro-wave engine is impossible ('We have a law of nature that prevents that thing from working.') and thus don't deem it worthy of testing. For as improbable as it may be, we might be wrong about the Law of the Conservation of Momentum in some way.
-
http://ntrs.nasa.gov/search.jsp?R=20140006052 (http://ntrs.nasa.gov/search.jsp?R=20140006052) "Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure."
And their explanation goes straight for "..producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma," rather than, say, "we may have made a really inefficient jet engine."
Sigh, close tab.
-
P.S.: It's good to see you guys here excited about that experiment and eager to see it tested! <3 I just read the linked article and got that gut reaction over the story of this fellow who designed this 'engine' having been denied the testing of his results by a third party for so long and even as the Chinese did, that western scientists apparently still dismissed this out of hand because the Chinese design was flawed, instead of doing better.
Personal guess, the dismissal of the Chinese experiment was out of similar reasons to why people are dismissive of the notion of North Korea being able to do anything but launch a rock into the ocean.
Unlike DPRK, the Chinese are perfectly capable scientists and space explorers.
-
I was speaking less about belief in the individual scientists, but more the government that has a fairly firm stranglehold on what information goes in and out of the country.
-
Ya, until the test setup is at near vacuum, I remain skeptical of any result. I lack an understanding of the quantum mechanics, but I can recognize a test setup flaw.
-
The dismissal of the Chinese experiment isn't political, they did it in an industrial setting not tuned to the incredibly fine levels of measurement needed to test the device (not to mention overturn one of the most fundamental laws of the Universe as we understand it). I am not opposed to continued testing. I think every avenue, no matter how unlikely, should be pursued in the continuing quest of mankind to build me a vacation home on Mars. However, I just find it much more believable that instead of unraveling our understanding of how things can move some people have just got a few cases of bad test results. I'd love to be wrong but I really, really doubt that I am.
But, by all means, toss one of those things out of the ISS and see what happens.
"Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure."
Ridiculous. :|
-
Oh, sorry for the double post, but adherence to the Law of the Conservation of Momentum isn't a pseudo-religious faith. On top of hundreds of years of consistent experimental confirmation, it is further confirmed by common sense. The words "reactionless drive" should sound like gibberish. It might as well be "driveless drive" or "reactionless reaction". Things move, whether it be here on Earth or out in space because something imparts momentum to them. In other words they are pushed. A reactionless drive is a device which would move without any push. It creates momentum in a manner which would have to be described as magical. It is movement without movement. It's very name is contradictory.
-
It creates momentum in a manner which would have to be described as magical.
It is supposedly quantum mechanics; not Newtonian or Einsteinian. Most of quantum physics is best described as magically.
Not saying this device works, but that quantum physics is mindbendy.
-
It creates momentum in a manner which would have to be described as magical.
It is supposedly quantum mechanics; not Newtonian or Einsteinian. Most of quantum physics is best described as magically.
Not saying this device works, but that quantum physics is mindbendy.
For a device that might provide reactionless thrust by means of virtual particles in accordance with what we understand of quantum physics I would direct you to the quantum vacuum plasma thruster. Often confused with the EMdrive but on slightly better ground.
And I would like to emphasize again, I am not a naysayer out of some contrarian reasoning. If I am wrong and this sort of thing works I will be the most ecstatic and joyous supporter. However, the Universe as we know it does not care for these sorts of things at all. The bastard.
-
Oh, sorry for the double post, but adherence to the Law of the Conservation of Momentum isn't a pseudo-religious faith. On top of hundreds of years of consistent experimental confirmation, it is further confirmed by common sense. The words "reactionless drive" should sound like gibberish. It might as well be "driveless drive" or "reactionless reaction". Things move, whether it be here on Earth or out in space because something imparts momentum to them. In other words they are pushed. A reactionless drive is a device which would move without any push. It creates momentum in a manner which would have to be described as magical. It is movement without movement. It's very name is contradictory.
Depends on what you mean by 'reactionless'. If one just means that no chemical reaction is directly responsible for generating the thrust, I think it's easily imaginable. I mean, the movement of a steam locomotive is provided by mechanical means, wheels pushing against the rails. The chemical reaction is there to provide the energy required for the mechanical work. Motion isn't caused by a propellant being emitted. So, I don't think the name is contradictory, it's just elliptic. Maybe a better name would be 'propellant-free drive'.
I mean, from an engineering perspective, that's the idea, to get an engine that doesn't need to be provided with a propellant, but which works with energy provided through e.g. solar sails and works in a vacuum. No?
That said, if there was a device providing thrust by some interaction of it with the virtual particles of the vacuum, then it wouldn't really break the Law of the Conservation of Momentum either. It'd more like circumvent it cleverly.
-
Either on Earth or in space a movement requires this "push". A train can move by means of a reaction which takes place in its engine between water and heat which it then converts through mechanical means into a rotation of wheels against the track upon which it sits. In space the situation is much easier to understand because there are fewer steps in a vacuum, momentum must be imparted to one thing from another. The most costly thing about space travel is that there is nothing up here against which to push. In the terms of trains you must "bring your own rails" as it were. The explosion of a rocket fuel provides thrust in a vacuum because it causes material to be moving opposite the desired direction of the satellite or whatever against which that object can "push" (helpfully by the same expulsion that puts the material there in the first place). In a closed system an object cannot move without momentum. A solar sail is an object that does not carry propellant but can move via the physical force of the photons of the sun striking it, just in the manner of wind and a sail here on Earth. A reaction is occurring.
An object simply cannot gain movement, and therefor momentum, without a reaction. "For every action there is an equal and opposite reaction." In a reactionless drive there is action without reaction. It strains not only the credulity of those that consider it but the very idea of how movement in the Universe occurs.
EDIT: And as an aside, the Conservation of Momentum has been confirmed even in Quantum Mechanics and Quantum Electrodynamics. A device of this nature, if it worked, would require the wholesale scraping of not just traditional physics but also of quantum physics. It shouldn't work by rules of both levels. Now, this is not a reason to disbelieve it, but one must consider that this supposed invention works due to rules that literally undermine every experiment observed in the past two centuries and so judge the claims accordingly.
-
It's simple, really, if there's a device that can magic energy into existance everyone'd love to have it. The reason why reports like this are quickly dismissed isn't that no one wants to develop/research something new, but rather because it claims to have done the (metaphorical) impossible, and when you look at the reports you notice that they've measured nanoscale effects with the ruler you had in elementary school.
So, the prudent way is to assume that the established fundamental laws still apply and look for a new effect that comes into play. This is a million times more realistic than "the other stuff is wrong". ;)
-
Either on Earth or in space a movement requires this "push". A train can move by means of a reaction which takes place in its engine between water and heat which it then converts through mechanical means into a rotation of wheels against the track upon which it sits. In space the situation is much easier to understand because there are fewer steps in a vacuum, momentum must be imparted to one thing from another. The most costly thing about space travel is that there is nothing up here against which to push. In the terms of trains you must "bring your own rails" as it were. The explosion of a rocket fuel provides thrust in a vacuum because it causes material to be moving opposite the desired direction of the satellite or whatever against which that object can "push" (helpfully by the same expulsion that puts the material there in the first place). In a closed system an object cannot move without momentum. A solar sail is an object that does not carry propellant but can move via the physical force of the photons of the sun striking it, just in the manner of wind and a sail here on Earth. A reaction is occurring.
An object simply cannot gain movement, and therefor momentum, without a reaction. "For every action there is an equal and opposite reaction." In a reactionless drive there is action without reaction. It strains not only the credulity of those that consider it but the very idea of how movement in the Universe occurs.
EDIT: And as an aside, the Conservation of Momentum has been confirmed even in Quantum Mechanics and Quantum Electrodynamics. A device of this nature, if it worked, would require the wholesale scraping of not just traditional physics but also of quantum physics. It shouldn't work by rules of both levels. Now, this is not a reason to disbelieve it, but one must consider that this supposed invention works due to rules that literally undermine every experiment observed in the past two centuries and so judge the claims accordingly.
You seem to have a very wide notion of reaction, there. Wind or photons pushing against a sail isn't a chemical reaction. There is no transformation of chemical substances into other chemical substances. The explanation for the engine here seems to be that the Law of Conservation of Momentum isn't broken, nor that energy or momentum is created magically, but through an interaction of the device with the quantum vacuum virtual plasma. The empty space of the vacuum isn't empty after all and theoretically it is thinkable at least that the device uses the quantum vacuum virtual plasma as that against what it pushes, just like the locomotive is using rails and a car the ground that is already there.
So, really, the point I'm making is eaxactly that you shouldn't dismiss anything because 'they measured nanoscale effects it elementary school rulers', but that if that's the case you should do the experiment with the proper preperation and equipment and then look at the results.
Also, I'm not at all against looking whether there comes another effect into play, rather then throwing the old laws out of the window. As I said, I wouldn't suspect that if the device worked, we'd have to throw the old laws out of the window in it's entirety, anyway. Oftentimes it's just the scope of the law/theory that is modified and that's usually then explained by 'new effects'.
-
(http://endlesspicdump.com/original/the%20future%20starts%20now.gif)
-
You seem to have a very wide notion of reaction, there. Wind or photons pushing against a sail isn't a chemical reaction. There is no transformation of chemical substances into other chemical substances. The explanation for the engine here seems to be that the Law of Conservation of Momentum isn't broken, nor that energy or momentum is created magically, but through an interaction of the device with the quantum vacuum virtual plasma. The empty space of the vacuum isn't empty after all and theoretically it is thinkable at least that the device uses the quantum vacuum virtual plasma as that against what it pushes, just like the locomotive is using rails and a car the ground that is already there.
So, really, the point I'm making is eaxactly that you shouldn't dismiss anything because 'they measured nanoscale effects it elementary school rulers', but that if that's the case you should do the experiment with the proper preperation and equipment and then look at the results.
Also, I'm not at all against looking whether there comes another effect into play, rather then throwing the old laws out of the window. As I said, I wouldn't suspect that if the device worked, we'd have to throw the old laws out of the window in it's entirety, anyway. Oftentimes it's just the scope of the law/theory that is modified and that's usually then explained by 'new effects'.
I am using "reaction" in regards to physics which simply means "repulsion or resistance exerted in opposition to the impact or pressure of another body; a force equal and opposite to the force giving rise to it." If you want to move you need action and reaction. The quantum vacuum plasma thruster is not reactionless because it proposes to use particles of the quantum vacuum as the reaction mass. If this can be done, and like I said the theory behind its operation is on much better ground than that of the EM Drive, then we would effectively have a jet engine for space travel where the reaction mass (the fuel) is sucked in from the vacuum and accelerated out of an exhaust to produce thrust. The EmDrive proposed by Roger J. Shawyer does not have a coherent explanation on how it works and, frankly, the explanation is either 1) This guy has invented a device which undermines every scientific observation of classical physics, quantum physics, and electrodynamics ever, or 2) We have a small group of experiments that created anomalous results. There are several perfectly reasonable explanations as to how these readings could have been arrived at mistakenly (and, frankly, if you have a device that shows good results when you test it and good results when you sabotage it then that's pretty clear evidence that your readings are not caused by the device but by some external factors you did not consider).
-
I've read a lot about this and I don't understand the focus on this thing breaking the conservation of momentum law (apart from that being a great headline for popular science articles that want clicks, of course!). My understanding from the reading I've done is nobody really knows conclusively how this thing works (assuming for a moment that it does work - which we also don't know definitively).
If we don't know what's going on to cause the thrust, then how do we know it must be breaking a law of physics? I get that there are theories which suggest it might be, but they're just theories right? They could be completely wrong at such an early stage, yes?
Given that, it seems odd to discount the drive's credibility on the basis of it breaking a law. Better, in my mind, is to doubt its credibility on the basis that we've done only very limited testing to even verify it works. Once we have conclusive test results, then we should worry about the basic laws, in my mind. Anything else is premature, no?
The best analogy I can think of this, if you'll bear with me:
We've run an experiment with a device called a Crookes radiometer (http://en.wikipedia.org/wiki/Crookes_radiometer), in a world where we have no knowledge of radiation (don't ask why, in this hypothetical world, they named it that!). Someone has "proved" that the vanes inside it move when you shine a light source on them, but they've done this by taking still photographs. The experiment is inconclusive because it doesn't show enough information to make a definitive call, and obviously before we get too excited, we need to re-test with better equipment (like a video camera) to confirm that the vanes move when you shine a torch on them, and that the thing actually works as described.
Before any such test is done though, there is naturally already some speculation about the possible causes in a working device. Some scientists are like "I got nothing, man. This is fucking voodoo". Other scientists, going with the most intuitive observation, and using the best knowledge they have at the time, suggest that it might be some kind of interaction with photons hitting the vanes that isn't yet fully understood: that when they bounce off the vanes it causes the rotation, since photons have momentum. There's an immediate problem to the theory though. It can be proven elsewhere that the pressure exerted by photons is far too small to move them. The pop-sci magazines of the day, who all love a good headline, leap all over this and announce that the vanes in Crookes' device must be moving by some phantom force that defies the laws of physics! Pop-sci magazines around the world sell out overnight, while skeptical scientists cry themselves to sleep. Morning editions of newspapers talk about how this new discovery might flip the scientific understanding of photons on its head, and how this could all usher in a new dawn of science as physics is reinvented from the ground up. Speculation explodes, and people's imaginations go wild talking about potential applications in spaceship designs that are powered by photons! \o/
Despite the story blowing up, and still before the tests are confirmed (i.e. before anyone films it happening and confirms the rotations definitively) scientists and scientifically-literate people maintain their skepticism that the vanes in the device are actually being rotated, because they know that photons cannot be doing it. They say that this would overturn all the previous years of observation and experimentation that demonstrates how photons behave. Going further, they say that since photons couldn't do this, the whole idea is nonsense, since the vanes would not be moving without any force being applied. It would break the laws of physics! The vanes can't be moving, and physical laws cannot be broken. I want to believe, they say, but please staph the madness.
Eventually a proper test is done, and they confirm that the vanes really do move. Looking further into this unexpected result, the real culprit is discovered to be radiation, a phenomenon that was previously unknown to science. It's shown that there is a very reasonable explanation for why the vanes in the device move the way they do, and it turns out to be perfectly compatible with the laws of physics. No laws are broken, and there is no phantom force after all. Suddenly our dreams are realized and we really can apply this new knowledge to making awesome space toys like solar sails. They're not powered by photons after all, as we initially thought, but no matter. We've just opened the door on possibilities for space travel that we never thought possible. One day we might be going to Mars on a radiation-powered mirror, with no on-board fuel required! \o/
The skeptics are like "Okay I was wrong about the thing with the laws and such, but screw it let's go to Mars" and the believers are like "It's cool we were wrong about that too, and the whole photon thing, but yeah, save me a seat!" And everyone lives happily ever after in a world that understands radiation.
Granted, that's all one hell of a hypothetical, and a simplification, and an imperfect analogy, and I am not at all familiar with the science behind all this ... but that's kind of how I see this right now.
We're debating photographic evidence when we need video footage to advance the dialogue. When we assume for the sake of argument that this thing works, we're reliant upon current scientific knowledge to explain it, which may not turn out to be sufficient in doing so. Stranger still (to me) we're discounting the notion that it could work based on current scientific knowledge because that same knowledge suggests it breaks the laws of physics.
Meanwhile it's still perfectly possible (unless I am hopelessly out of my depth here, which is likely) that this thing could work, that we might not yet understand what makes it work, and that it might not break any laws after all.
tl;dr - We are dumb monkeys with a bad track record for dogmatism, we often analyze unexpected results poorly, we sometimes fling our poo prematurely.
-
I am using "reaction" in regards to physics which simply means "repulsion or resistance exerted in opposition to the impact or pressure of another body; a force equal and opposite to the force giving rise to it." If you want to move you need action and reaction.
Oh, I 100% agree there. If you use reaction in that sense, you can't have a reactionless propulsion device. I don't think that this is what any sensible person means by 'reactionless propulsion device'. I think what they mean is a device that creates propulsion without the need for a propellant that needs to be taken along and that is exhausted by a chemical reaction.
Other than that, I think I've been trying to express exactly what Ursa wrote up there much better then I was able to.
-
The photon hitting your solar sail has its energy from a chemical reaction. But 'cleverly circumventing' that would violate conservation of energy.
What the EmDrive proposes is channeling microwave thrusts inside a specifically shaped cavity to generate radiation pressure upon which the unit generates thrust outside without energy leaving the unit. Essentially, this would be the equivalent of pushing your car forward by pressing your butt back into the seat. Granted, we're talking about very small effects and in the quantum world fucked up things are possible. The proposed magnitudes of the effects is still very, very high.
Also the NASA test report got the same results for the tested device and a second device they've disabled. Or at least they believed they did, apparently magical space engines are pretty much indestructable.
Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article).1 (http://arstechnica.com/science/2014/08/dont-buy-stock-in-impossible-space-drives-just-yet/)
-
The photon hitting your solar sail has its energy from a chemical reaction. But 'cleverly circumventing' that would violate conservation of energy.
Of course it has it's energy from somewhere. Doesn't mean that the device involves a chemical reaction. The solar sail itself doesn't involve a chemical reaction directly, so in itself it is a 'reaction less device' in, say, comparison to a rocket engine.
What the EmDrive proposes is channeling microwave thrusts inside a specifically shaped cavity to generate radiation pressure upon which the unit generates thrust outside without energy leaving the unit. Essentially, this would be the equivalent of pushing your car forward by pressing your butt back into the seat. Granted, we're talking about very small effects and in the quantum world fucked up things are possible. The proposed magnitudes of the effects is still very, very high.
The proposed explanation is that the effect is a quantum effect. I think bringing up an everyday world examplelike pressing your butt into the drivers seat fails gravely to capture this. also, the claim isn'tthat energy doesn't leave the unit: Quite the contrary is the case, if you look at the Theory Paper (http://www.emdrive.com/theorypaper9-4.pdf), equasion 16. According to it momentum is conservated as well: the electromagnetic waves loose momentum as the hit the end walls of the cavity. new momentum is built up by spending energy. Thus, it's also not explained as a 'reactionless' enigne in the sense of physical reaction:he thrust is the result of the reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it.
Also the NASA test report got the same results for the tested device and a second device they've disabled. Or at least they believed they did, apparently magical space engines are pretty much indestructable.
Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article).1 (http://arstechnica.com/science/2014/08/dont-buy-stock-in-impossible-space-drives-just-yet/)
I think it's bad sport to call the NASA article out for not providing the necessary equipment to show that there is any effect and then again taking it up to say that because the 'null' test article showed results, too, the thing doesn't work.
Either you accept the experimental design, then you have to explain the effect measured in both cases: That is you have to identify the error or show why bot had an effect. Or you don't accept the experimental design as sufficent, but then you can't cite the results to cast doubt on the effect the device has.
Also, if you read the full paper, you will see that the 'null device' wasn't simply disabled, but merely lacked some extra slotting that were in Fetta's theory necessary for the production of thrust.
-
Hm...
Could you give me a little help with that paper and explain the equation and those used for it in a bit more detail please?
-
Essentially, this would be the equivalent of pushing your car forward by pressing your butt back into the seat.
This is exactly the kind of metaphor I've been searching for. The quantum vacuum plasma thruster might work but the idea of a ship or probe being powered by creating two different area's of density of microwave particles on the inside and therefor, for lack of a better word, continually "sucked" towards the area of lower density makes no sense. The system is closed and would simply even out without having budged.
Also, I think I have not properly conveyed what is meant by reactionless and we keep getting hung up on "reaction" as if we're referring to the chemical reaction of a conventional rocket. The reaction isn't referring to fuel or power or anything but to the simple proposition that you cannot move one thing forward while not pushing another thing back. Your "action" of moving forward must be conserved through the "reaction" of another thing moving back. i.e. Your gain in momentum must be met by something else's loss in momentum.
A reactionless drive violates Conservation of Momentum because if movement occurs momentum must be imparted in both directions. If it is not you are creating magic momentum. This is what is meant by every action involves and equal and opposite reaction. If I want my ship to go forward then I need to be pushing off of something and sending it away from me. It doesn't matter if I'm a rocket, a train, a bird or a guy on a bike. A reactionless drive is in the same league of impossible as a perpetual motion machine, literally. One violates the law of conservation of energy while the other violates law of conservation of momentum. They're right next to each other in every way apart from alphabetically.
They're the most annoying aspects of the universe but that's the way it is, you don't get unlimited movement and you don't get unlimited energy. When I design my universe all vehicles will be reactionless drives powered by perpetual motion machines. And there will be lightsabers.
-
But...a warp drive would circumvent the whole Con-o-Mom law, right?
-
The photon hitting your solar sail has its energy from a chemical reaction. But 'cleverly circumventing' that would violate conservation of energy.
Of course it has it's energy from somewhere. Doesn't mean that the device involves a chemical reaction. The solar sail itself doesn't involve a chemical reaction directly, so in itself it is a 'reaction less device' in, say, comparison to a rocket engine.
Photons hitting and reflecting off a materials is a Newtonian reaction. As in for every action, there is an opposite and equal reaction.
The photons carry momentum, despite being massless. (http://en.wikipedia.org/wiki/Photon#Physical_properties)
Change in momentum over time (dP/dt) is equal to some force (F). Thus as light reflects hits and reflects off the reflective sheet, it imparts a change in momentum over time pushing the reflective sheet (and whatever is attached to it).
Spacecraft ion and nuclear engines do not involve chemical reactions, but are most definitely rocket engines.
-
Ah, sure. maybe i should have written 'classical rocket engine'?
(https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcRWjiWnPFphoITnmxbEJaM3I97wUMLwHuPQeVkapdcukxIsacA4)
Also: Reaction is said in many ways. Thus it is possible to speak of a reactionless engine in one way (chemically), while not contradicting or denying that it is a reaction engine in another way (physically).One shouldn't get hung up with words like 'reactionless', which mean a lot of things depending on context.
Hm...
Could you give me a little help with that paper and explain the equation and those used for it in a bit more detail please?
Basically, the equation says that the input power of the device must equal the electrical loss of power plus the output power transferred to the vehicle (according to 16, ref. law of conservation of energy). Now, both the electric loss of as well as the tranferred amount of power are directly dependen on the input power, which is why it is eliminated from (16). I'm not sure what else to explain there. <,<
The thing is, this is based on the non-classicity of the system. It is not the case of an ass pressing back in the seat: the velocity of the ass is directly dependant on the velocity of the car it's sitting in. As the speed of the em waves is quite close to the speed of light - in distinction to the speed of you ass (at least I assume you are incapable to move your ass with the speed of light!), the velocity of the waves is not directly dependant on the velocity of the device and thus has to be dealt with as if it's open system where reaction happens between waveguid and beam. The momentum gained by the EmDrive plus the momentum lost by the electromagnetic wave equals zero. At least according to the theory of the em drives proponents.
In the end it's a question of how to place the relativistic reference frame(s). But there is at least some reason to assume that it is valid to place reference frames for both the wave and the waveguide. Whether that's actually the case has to be answered experimentally, imho.
Tl;dr: Newtonian mechanics are passé already, they are a mere special case of more encompassing theories which allow to explain effects that Newton can't.
-
(16) shows the relation between Q-factors and velocity, nothing more. The relevant assumptions - those I've asked you to explain - are a bit higher up. To answer my own question, however, as you're possibily a wee bit out of your depths here.
You see the net power loss directly being transformed into kinetic energy (velocity), essentially making this device magical. There is, of course, a correction factor for his device (Df), which is a bit concerning giving what he's trying to prove. All the complicated maths up and including this point are correct as far as I'm able to check them (I'm sure you did work through all of them on paper, too), and even some of his assumptions are reasonable.
There are some jarring mistakes, however, and anyone with some high school physics classes should've been able to spot them. To be fair, in his most recent version of the theory paper (9.4) they've been cut - not replaced or corrected, cut. So you might've missed the opportunity to reflect on them.
v9.3 [1] (http://www.newscientist.com/data/images/ns/av/shawyertheory.pdf) still has them.
So, all his fancy math proves that his EM waves push harder on the top than on the bottom if he uses the cone shaped apparatus. He, however, neglects a bit of the aforementioned high-school physics. Inelastic collisions always have a force component perpendicular to the resulting vectors. In other words, the EM waves do not just push on the top and bottom of the cavity, but also on the sides, resulting in a net downward push (do some vector analysis on a sketch to see it, it's really simple). You will see that this cancels the top/bottom difference out. He made the same mistake in his paper again, even in 9.4 p.4, when he imagines the system with a fluid instead of microwaves, discarding the push on the sides as a mere mechanical strain.
If you would've used your own head instead of quoting Shawyer's own FAQ you might've spotted that.
It's impossible to do a proper survey of Shawyer's own measurements as there's no documentation and/or data published, which is not a good sign, as
a proper publication has the supporting information providing enough information to properly judge the procedures used in testing. The Eagleworks lab shared a bit more information, which is still not very good based on a few reasons I've already given. Let's rehash them.
1) They've measured 3.6mN on a scale with a single digit mN resolution.
2) They've measured the same net force on the active and 'inactive' device, which despite the flaws in the setup, strongly suggest that they might've gotten the same results if they put a potato in their test chamber.
3) They've measured at ambient pressure. Even a very small temperature gradient between the device and the atmosphere will lead to air convection exerting tiny pressures (mN!), too.
4) The devices are bulky and use active water cooling for their magnetrons, also a lot of cables. We're trying to talk about mN effects - the FTL experiment's error was a bad plug/connector, not a groundbreaking effect.
The 'ass in seat' example was an attempt to make an easy to understand example why conservation of momentum is violated. Real-life examples don't hold up well with quantum mechanical systems, however, just saying "quantum" and wave your hand doesn't help either (neither does saying 'relativistic' or 'Einstein'). Conservation of energy/momentum holds up in QM, which just shows how passé Newtonian mechanics really are.
-
Having followed this thread for a while, I cannot like Desiderya's response enough. Do we have medals for good posting here?
-
Some questions about the tests answered (http://www.wired.co.uk/news/archive/2014-08/07/10-qs-about-nasa-impossible-drive).
Must. Resist. Urge. To. Get. Excited.
-
91 micronewtons of thrust for 17 watts of power, compared to the 40 micronewtons of thrust from 28 watts for the Cannae drive.
Takes forever to get anywhere. Small solar sails are as effective in the inner solar system.
People keep chasing "special" technology like there is a holy grail to open up space colonization/development, but keep forgetting that it isn't moving around space that is the problem. It is getting into space that is the challenge, but even that already has a brute force solution that works. The cost of space is not tied to the technology. It is tied to the number of engineers & technicians needed to do the work.
-
91 micronewtons of thrust for 17 watts of power, compared to the 40 micronewtons of thrust from 28 watts for the Cannae drive.
Takes forever to get anywhere. Small solar sails are as effective in the inner solar system.
People keep chasing "special" technology like there is a holy grail to open up space colonization/development, but keep forgetting that it isn't moving around space that is the problem. It is getting into space that is the challenge, but even that already has a brute force solution that works. The cost of space is not tied to the technology. It is tied to the number of engineers & technicians needed to do the work.
Keep in mind that this isn't EVE. Thrust =/= speed in the real world. Thrust is acceleration. That means this device, while not providing very much thrust, provides it for 'free' which would allow very long slow speed ups. It doesn't sound significant, but with the distances involved in space, it becomes rather awesome.
-
91 micronewtons of thrust for 17 watts of power, compared to the 40 micronewtons of thrust from 28 watts for the Cannae drive.
Takes forever to get anywhere. Small solar sails are as effective in the inner solar system.
People keep chasing "special" technology like there is a holy grail to open up space colonization/development, but keep forgetting that it isn't moving around space that is the problem. It is getting into space that is the challenge, but even that already has a brute force solution that works. The cost of space is not tied to the technology. It is tied to the number of engineers & technicians needed to do the work.
Keep in mind that this isn't EVE. Thrust =/= speed in the real world. Thrust is acceleration. That means this device, while not providing very much thrust, provides it for 'free' which would allow very long slow speed ups. It doesn't sound significant, but with the distances involved in space, it becomes rather awesome.
No, it is not Eve. And I am incredibly frustrated that you think that is what I said.
Thrust is not acceleration. Thrust is a force, which when applied to a mass creates an acceleration.
Solar sails and ion drives provide very low thrust, but have incredibly high Isp (infinite and ~8000 Isp respectively), how rocket efficiency is measured. They still take forever to get places - 1 year might become 6-8 months, but it still takes time.
Orbital mechanics gets more complicated with constant thrusting versus the relative impulse thrust provided by a low-efficiency, high-thrust chemical rocket. Don't get me wrong - low thrust drives let us do really cool stuff (http://dawn.jpl.nasa.gov/). Constant-burning to from Earth Orbit to Mars Orbit changes a lot with constant thrust; it can shorten the trip.
But even if this quantum-effect drive works and becomes the perfect drive for interplanetary and interstellar travel, it is meaningless if we do not solve the problem of climbing out the gravity well, Thrust-to-Weight greater than 1 is required.
It still does not break the economic hurdle of getting it into space - 1 kg in LEO of anything costs at least $4,600 today. That cost is not derived from the cost of the materials that go into the rockets (<$5M), it is the thousands of technicians and engineers that design, build, and launch the rocket.
-
Well actually Sawyer, the original creator of the EmDrive, has calculated that if superconducting materials were used to make the drive, it could produce enough thrust to push out of the gravity well.
-
Huh, I remember seeing something about this at the time that said that the initial nasa report was not a "Hey, look what we did!" but rather a "Hey, can someone figure out what we did?"
It wasn't presented as a reviewed paper, but rather as a sort of request for people to look it over. Reason being, they measured thrust when they turned it on... and also measured thrust when it wasn't supposed to be producing any. If you're not supposed to be producing thrust, and measuring it anyways, that doesn't lend a lot of credence to it when you then measure thrust when you should be.
... haven't really been following this since then.
-
2. Thrust was also measured from the 'Null Drive', doesn't that mean the experiment failed?
Lots of commenters jumped on this, assuming incorrectly that this was a control test and that thrust was measured when there was no drive.
In fact, the 'Null Drive' was a modified version of the Cannae Drive, a flying-saucer-shaped device with slots engraved in one face only. The underlying theory is that the slots create a force imbalance in resonating microwaves; the 'Null Drive' was unslotted, but still produced thrust when filled with microwaves. This may challenge the theory -- it is probably no coincidence that Cannae inventor Guido Fetta is patenting a new version which works differently -- but not the results.
The true 'null test' was when a load was used with no resonant cavity, and as expected this produced no thrust:
"Finally, a 50 ohm RF resistive load was used in place of the test article to verify no significant systemic effects that would cause apparent or real torsion pendulum displacements. The RF load was energised twice at an amplifier output power of approximately 28 watts and no significant pendulum arm displacements were observed."
Equally significantly, reversing the orientation of the drive reversed the thrust.