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Thread: Chinese Say They're Building 'Impossible' Space Drive

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    Chinese Say They're Building 'Impossible' Space Drive

    Chinese Say They're Building 'Impossible' Space Drive

    Chinese researchers claim they've confirmed the theory behind an "impossible" space drive, and are proceeding to build a demonstration version. If they're right, this might transform the economics of satellites, open up new possibilities for space exploration –- and give the Chinese a decisive military advantage in space.

    To say that the "Emdrive" (short for "electromagnetic drive") concept is controversial would be an understatement. According to Roger Shawyer, the British scientist who developed the concept, the drive converts electrical energy into thrust via microwaves, without violating any laws of physics. Many researchers believe otherwise. An article about the Emdrive in New Scientist magazine drew a massive volley of criticism. Scientists not only argued that Shawyer's work was blatantly impossible, and hat his reasoning was flawed. They also said the article should never have been published.
    "It is well known that Roger Shawyer's 'electromagnetic relativity drive' violates the law of conservation of momentum, making it simply the latest in a long line of 'perpetuum mobiles' that have been proposed and disproved for centuries," wrote John Costella, an Australian physicist. "His analysis is rubbish and his 'drive' impossible."
    Everything I need to know I learned through Googling.

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    Yeesh. It doesn't take any great effort to see how it's flawed. If it worked, any asymmetrical container would experience constant thrust. Take an empty water bottle...internal pressure is equal on all surfaces, and the bottom has more area than the cap...by his analysis, if tossed into vacuum with some air inside, it would accelerate bottom-ward. It doesn't, of course, because the bottle also has sides which can not be entirely vertical...

    So...what could the Chinese possibly be thinking?

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    The last link in ToSeek's post is a good explanation of what's wrong.

    I suspect this is a case of someone with more authority than scientific knowledge declaring this a funded project, while ignoring the closed-minded scientists who tell him it won't work. Either that, or "we must do this in case it works, before the evil Americans do it".

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    Nothing at all wrong with letting them build it.

    Let 'em dump a whole bunch of money in it and PLEASE let them publish the results if it doesn't work (the Chinese are notorious for not admitting to failures).

    Then we can put the whole thing to bed as a blind alley....

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    Typical of communist countries. The Soviets dabbled in all sorts of woo woo stuff.

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    Does it run on melamine?

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    Quote Originally Posted by Superluminal View Post
    Typical of communist countries. The Soviets dabbled in all sorts of woo woo stuff.
    This statement strikes me as unnecessarily political and in fact downright wrong.

    There are plenty of foolhardy perpetual motion machine and cold fusion inventors right here in the U.S. merrily wasting their lives in pursuit of the impossible.

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    Yeah, but the US only started trying to train telepathic spies when when the powers that be became worried about an ESP gap.

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    Quote Originally Posted by cjameshuff View Post
    Yeesh. It doesn't take any great effort to see how it's flawed. If it worked, any asymmetrical container would experience constant thrust. Take an empty water bottle...internal pressure is equal on all surfaces, and the bottom has more area than the cap...by his analysis, if tossed into vacuum with some air inside, it would accelerate bottom-ward. It doesn't, of course, because the bottle also has sides which can not be entirely vertical...

    So...what could the Chinese possibly be thinking?
    I confess to believing that a water bottle, tossed into a vacuum with some air inside, would in fact accelerate bottom-ward, as the air escaped out the back.

    Quote Originally Posted by tdvance View Post
    The last link in ToSeek's post is a good explanation of what's wrong.
    Also, I'm not sure how good this explanation is. It's certainly an angry explanation, and it certainly insists that advanced theoretical understanding isn't necessary to debunk the original claims, but I'm having trouble figuring out exactly where the problem is.

    You have a microwave generator, it pumps microwaves into a cone-shaped vessel, and then the waves vent out the back. How is this any different, in principle, from any other rocket, other than in the nature of the reaction "mass" being used?

    And where's the violation of conservation laws? It's not like the SSME violates conservation laws by venting exhaust product out the mouth of its nozzle, right?

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    Quote Originally Posted by stutefish View Post
    I confess to believing that a water bottle, tossed into a vacuum with some air inside, would in fact accelerate bottom-ward, as the air escaped out the back.
    Put the cap on first. Yes, many real water bottles would have issues with containing an atmosphere of pressure, but that's entirely aside from the issue.


    Quote Originally Posted by stutefish View Post
    You have a microwave generator, it pumps microwaves into a cone-shaped vessel, and then the waves vent out the back. How is this any different, in principle, from any other rocket, other than in the nature of the reaction "mass" being used?
    His "space drive" doesn't vent the microwaves anywhere. Doing so would make it a photon drive, which is entirely possible, if very low thrust. The cavity is closed...microwaves go in, but don't exit. His claim is that photon pressure in a closed cavity in the form of a truncated cone results in a net force toward the larger end.

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    Originally Posted by Superluminal
    Typical of communist countries. The Soviets dabbled in all sorts of woo woo stuff.

    This statement strikes me as unnecessarily political and in fact downright wrong.

    There are plenty of foolhardy perpetual motion machine and cold fusion inventors right here in the U.S. merrily wasting their lives in pursuit of the impossible.


    Inventors working on their own is one thing. All they do is delude themselves and whomever is foolish enough to invest in them.

    When a government adopts something radical in the name of ideology, a lot of people can suffer. China under Mao did things (e.g. Great Leap Forward and Cultural Revolution) in the name of ideology that resulted in the deaths of millions of people (I've heard figures of over 40 million deaths). Likewise, the Soviet Union adapted a formal theory of agriculture and genetics based on communist ideology (such as the work of Trofim Lysenko set back their biological and agricultural efforts for decades.

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    Quote Originally Posted by cjameshuff View Post
    Put the cap on first. Yes, many real water bottles would have issues with containing an atmosphere of pressure, but that's entirely aside from the issue.




    His "space drive" doesn't vent the microwaves anywhere. Doing so would make it a photon drive, which is entirely possible, if very low thrust. The cavity is closed...microwaves go in, but don't exit. His claim is that photon pressure in a closed cavity in the form of a truncated cone results in a net force toward the larger end.
    Oh!

    Yes, I see the problem quite clearly now.

    How did the Chinese government ever fall for this? Or, how did they think they would gain face by publically endorsing it?

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    Quote Originally Posted by stutefish View Post
    Oh!

    Yes, I see the problem quite clearly now.
    Given how utterly wrong it is, your confusion about what they meant is quite understandable...

    Any asymmetrical stray emissions will produce an uneven force, though. It would be far less than predicted, but perhaps enough to convince an official eager for some great accomplishment he can take credit for, or allow them to claim "promising" results and get further funding. The un-leaked RF energy will be lost as heat, which they could blame on losses in the resonant cavity due to shape and materials, or the method of injection...something that could surely be corrected with further development. Also, if the microwaves are produced in stationary equipment, there will be net photon pressure on the drive, allowing it to accelerate away from the microwave source...exactly countered by the recoil on the microwave source, of course.

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    Hey, just a thought:

    They could team up with Mythbusters and make it a planetary pay-per-view.

    ....they might even make a load of bucks off the experiment and this could be a way to help finance real missions.....

    ;-)

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    Quote Originally Posted by stutefish View Post
    Also, I'm not sure how good this explanation is. It's certainly an angry explanation, and it certainly insists that advanced theoretical understanding isn't necessary to debunk the original claims, but I'm having trouble figuring out exactly where the problem is.

    You have a microwave generator, it pumps microwaves into a cone-shaped vessel, and then the waves vent out the back. How is this any different, in principle, from any other rocket, other than in the nature of the reaction "mass" being used?

    And where's the violation of conservation laws? It's not like the SSME violates conservation laws by venting exhaust product out the mouth of its nozzle, right?
    I found it a humorous, not angry, explanation. Nothing more than high-school physics plus a tiny amount of vector arithmetic is needed to understand it. The paper being debunked doesn't argue that the thrust is from escaping microwaves (and you'd need an awful lot!!!). The paper argues that an enclosed container with microwaves bounding around inside will somehow put more pressure one one side than the others, all because of the conical shape of the container. The link I referenced explains why that is not the case.

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    It took me a moment to visualize what the paper was trying to explain, too. I think it would have been easier to understand if he had included some visual aids of his own. That or maybe I should have read the paper it was debunking first.

    ETA: Now the only nagging question left in my head is, why is the chamber flat at both ends? According to the principle that's supposed to make it work, it seems you'd get a much more efficient design by having it taper to a point. That way you don't have microwaves bouncing off the small end and creating a drag force (Fg2 in the figure on page 2 of Shawyer's paper.

  17. 2008-Sep-25, 11:54 PM

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    Quote Originally Posted by tdvance View Post
    The paper being debunked doesn't argue that the thrust is from escaping microwaves (and you'd need an awful lot!!!).
    Off on a tangent...one interesting thing about photon drives is that because the momentum of a photon is directly proportional to its energy, all that matters is the power output...a watt of UV, a watt of IR, and a watt of microwaves give the same thrust. A laser or maser and reflectors to redirect its waste heat won't do any better than a big tungsten filament (or nuclear lightbulb) and parabolic reflector.

    (Technically, there'll be a small difference due to differences in collimation, but considering the inefficiencies in highly collimated photon sources and resulting difficult-to-collimate waste heat radiation, I don't think it makes a practical real-world difference.)

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    Might I ask a silly question about this trick? I am trying to figure out how you could get enough of a result to make someone want to pay for it.

    Could a system like this move the bottle, make it rattle around but not really go any where? Sort of like a rocking chair?

    Take a balance and press down on one side. It moves. Now press the other side. It moves again. It seems to me this device would do the same if you pulsed the energy; the bottle should move with the firing and then in the other direction when the wall is struck just like the balance.

    With the balance you are not fooling anyone; it moves when you touch it. This device seems like it would move, but obviously won't go anywhere. You could claim that it moves and it is just a matter of getting it to go in the one direction all of the time.

    Is that correct or really bad logic?

    Solfe

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    It'd take one heckuva pulse of photons to get the device to move perceptibly. More likely he's just duped people into investing without ever having seen it.

    Given that it's been two years since the emdrive made the cover story of New Scientist there still hasn't been anything along the lines of independent confirmation of what Shawyer has claimed (namely, .1N of thrust), it's probably safe to assume that nobody on the planet has ever seen it do anything interesting. I might be willing to briefly entertain the idea that he has been keeping such demonstrations behind closed doors if not for the fact that he put it on the cover of New Scientist and has a paper on the Web describing exactly how the thing is supposed to work even though the device is covered by absolutely no patent protection. It's hard to imagine that anybody would be so open and so secretive about something like this (unless they're just playing games).

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    Quote Originally Posted by Solfe View Post
    Could a system like this move the bottle, make it rattle around but not really go any where? Sort of like a rocking chair?
    There might be an impressive hum from transformers, anything else will be special effects added by them. The device won't produce any thrust, but if the microwave source is stationary (by which I mean not rigidly attached to the device), there will be a detectable force on the device. A very tiny one, due to simple photon pressure...3.33 micronewtons per kilowatt, assuming the microwaves are absorbed completely rather than reflected back out...but measurable, and with sufficient ingenuity they could spin that into "positive results". Like I said...they could claim the Q of the resonator isn't good enough, and that the reason the thrust is so low is that it's absorbing the microwaves, and that all they need is a little more time and money to make better resonators...or maybe something's wrong with the microwave source, etc...

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    It isn't impossible that this conic design is coupling with air molecules outside the chamber, and creating a measurable thrust when the system is not in a vacuum. (I don't see why it would, but I can see that a demonstration could fool an observer who is not critical enough to assess this possibility.) Is the 'nozzle' conductive or not?

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    seems to me that this is a bit like mounting a fan at the back of a sailboat pointed up at the sail to provide thrust.

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    Quote Originally Posted by Jerry View Post
    It isn't impossible that this conic design is coupling with air molecules outside the chamber, and creating a measurable thrust when the system is not in a vacuum. (I don't see why it would, but I can see that a demonstration could fool an observer who is not critical enough to assess this possibility.) Is the 'nozzle' conductive or not?
    Also, the interior of the resonator may not be airtight. If they can only run it for brief pulses (due to overheating caused by the "poor geometry of the resonator" or something similar that could surely be solved with a bit more time and money...certainly nothing to do with the fact that there's just nowhere else for the microwaves to go), it might simply eject heated air and achieve a measurable thrust.

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    "All ahead, full impulse, Mr. Sulu."

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    Personally I hope this thing does work, just to knock some of the smug off some people.

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    All I will say is idiots... and in the event it works, I can delete this reply, and thus write history

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    Quote Originally Posted by Professor Tanhauser! View Post
    Personally I hope this thing does work, just to knock some of the smug off some people.
    I wish that we could develop some kind of reactionless drive, too. Unfortunately, the results of physics experiments that I've seen (including many that I've done myself) from numerous subfields leave me no doubt that conservation of momentum is one of those rules that we're not going to get around.
    Conserve energy. Commute with the Hamiltonian.

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    Even if we do assume that this thing works, it's even harder to see why it should be any more efficient than a straight photon drive.

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    Quote Originally Posted by Grey View Post
    I wish that we could develop some kind of reactionless drive, too. Unfortunately, the results of physics experiments that I've seen (including many that I've done myself) from numerous subfields leave me no doubt that conservation of momentum is one of those rules that we're not going to get around.
    Laser light sail propulsion is almost as good, perhaps even better since you no longer have to make compromises to reduce the mass of the power plant, and can reuse it for other launches. Be nice if you could avoid the complication of deploying huge reflective film sails, though. And while the drive lasers would be reusable, they would not be cheap.

    One concept I've seen that could work at short ranges is a variation on light sails in which a reflector on the craft an another on a base station form a cavity in which light bounces multiple times before escaping, applying more momentum to the craft (and the base station, of course, which presumably has other ways to handle it, or is just massive enough for it not to matter much) from the same energy input. If you can make big and lightweight mirrors with the required precision, this would at least give an initial boost out of orbit. If only the diffraction limit didn't exist...

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    Quote Originally Posted by nauthiz View Post
    Even if we do assume that this thing works, it's even harder to see why it should be any more efficient than a straight photon drive.
    A photon drive is hideously inefficient. If the numbers from Shawyer's site were correct, this would be more than 5,000 times more efficient than a photon drive. Which is a good reason to suspect that he's made just a teensy mistake somewhere along the way.
    Conserve energy. Commute with the Hamiltonian.

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