EM Drive doesn't defy Newton's 3rd law after all

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Plazma Inferno!, Jun 17, 2016.

  1. Plazma Inferno! Ding Ding Ding Ding Administrator

    Messages:
    4,609
    A lot of space lovers are freaking out about the EM drive because of claims it could get humans to Mars in just 10 weeks, but just as many are sick of hearing about it, because, on paper at least, it doesn't work within the laws of physics.
    Physicists have just published a new paper that suggests the controversial EM drive - or electromagnetic drive - could actually work, and doesn't defy Newton's third law after all.
    Despite that not-insignificant setback, the EM drive shows no signs of quitting, and test after test - including trials by NASA scientists at the Eagleworks lab, and an independent researcher in Germany - has conceded that the propulsion system, somehow, does produce thrust, but it won't get us to Mars in 70 days.

    http://www.sciencealert.com/new-pap...drive-doesn-t-defy-newton-s-3rd-law-after-all

    Paper: http://scitation.aip.org/content/aip/journal/adva/6/6/10.1063/1.4953807
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Q-reeus Valued Senior Member

    Messages:
    2,603
    So the authors offer as 'explanation' that 'out of phase paired photons' exit preferentially from one end of the EM-drive cavity. What a joke. Actually a double joke.
    Firstly, out of phase means zero net energy-momentum. The supposed stream of 'anti-phased pairs' is thus in any useful sense nonexistent. Hence cannot offer any reaction to reported EM-drive action. Further, linearity holds and as such, the probability of either of the 'pair' exiting through the conducting shell is vanishingly small. Double whammy. How the hell did AIPP let that junk get into print?
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. exchemist Valued Senior Member

    Messages:
    6,618
    Have to say I rather agree. Two photons whose relative phase interfere destructively are not emitted photons: it just means there is no emission, surely? It appears ridiculous to suggest they can be there, carrying momentum and energy, and cancel one another out.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. The God Valued Senior Member

    Messages:
    3,546

    Anything can happen in our imagination ?
     
  8. Ultron Registered Senior Member

    Messages:
    182
    Personally I dont care much if there is some theoretical explanation. The main problem of EM drive is extremely small measured thrust, which is somehow near or overlapping with error bar of measurement. It is so small, that even if it is really there (which is still questionable), it is practically useless.

    And this "independent German scientist" who confirmed it in 2015, is Martin Tajmar, who produced several controversial experimental results in the past, which were never confirmed or repeated by anybody.
     
    exchemist likes this.
  9. rpenner Fully Wired Staff Member

    Messages:
    4,833
    http://scitation.aip.org/content/aip/journal/adva/info/about?section=Focus and Coverage
    They have chosen to emphasize speed over editorial review. Consequently, well-formatted bafflegab (and the references section is all over the chart) will occasionally get through.

    Example from paper, Figure 2's caption:
    Three waves with increasing lengths portray three photons (blue, green and orange) with decreasing curvature that relates to decreasing energy and momentum. It is worth noticing the total signed curvature over the wave vanishes because the two lobes are of opposite sign, and hence the photon is massless.​
    That's not how that works.

    Unsurprisingly, all three authors have no other published papers on "Scitation".
     
    Last edited: Jun 17, 2016
  10. Q-reeus Valued Senior Member

    Messages:
    2,603
    Even allowing for 'speed over editorial review', that above link begins with
    and a bit further down:
    Hmm... probably makes a pass on the 'original' criteria, but certainly not on the 'technically correct' one. Any referee with no more than secondary school education should have immediately spotted the various basic conceptual errors.
    Maybe all three authors are fresh graduates from uni. Regardless, their collective grievous errors are totally inexcusable given the three surely bothered to cross-check each other's input prior to submission. I suspect they may have won a bet. That it's possible to get a piece of superficially technical garbage past peer review and into publication. It's been done before. Risky in terms of their further career prospects, but maybe they figure a belated confession will be accepted as 'a bold if cheeky initiative illustrating current failings in peer review process'. If that is not the explanation, a sad example of farce upon farce.
     
    Last edited: Jun 18, 2016
  11. Plazma Inferno! Ding Ding Ding Ding Administrator

    Messages:
    4,609
    Researchers propose EM drive propulsion from emission of paired photons

    Recent reports about propulsion without reaction mass have been met on one hand with enthusiasm and on the other hand with some doubts. Namely, closed metal cavities, when fueled with microwaves, have delivered thrust that could eventually maintain satellites on orbits using solar power. However, the measured thrust appears to be without any apparent exhaust. Thus the Law of Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster’s cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagnetic fields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum, gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired-photon conclusion.
    The researchers began by asking: Is there any other phenomenon, besides that demonstrated with the EM drive, where photons, as carriers of the electromagnetic force, are ‘fed in’ but nothing seems to be ‘coming out’? Yes, when coherent rays of light interfere, a diffraction pattern emerges with bright and dark bands – and at a dark band we see nothing (Fig. 1). We see no light when two photons combine with opposite phases. Their electromagnetic fields cancel perfectly, but that does not mean that the photons themselves would have vanished for nothing
    Researcher propose the EM drive expels photons in pairs where the two co-propagate with 180 degree phase difference. These composite bosons have no net electromagnetic field, and hence they do not reflect back from the resonator’s metal walls, but escape to surroundings. The paired-photon efflux carries momentum, and hence the cavity experiences an equal but opposite reaction. Thus, they claim that the thrust of an EM drive is the action due to the paired-photon efflux.

    http://nextbigfuture.com/2016/06/researchers-propose-em-drive-propulsion.html
     
  12. exchemist Valued Senior Member

    Messages:
    6,618
    This serves to confirm that the authors are speaking ex ano, in my opinion.
     
  13. Q-reeus Valued Senior Member

    Messages:
    2,603
    NextBigFuture are late to the party with that one, which simply rehashes the OP article linked to there. I corresponded with two of the authors, pointing them to this thread, and invited a response. Nothing really useful came of it, but I was bemused by one of the author's comment that
    "In the case of the EM drive I don't see charges moving but potential being converted to vector potential as in Poynting theorem or Lorenz gauge."
    And somehow they can conjure up a non-zero Poynting momentum flow from exactly cancelling anti-phased 'photon pairs'?! Apart from that 'anti-phased pairing' cannot skirt linearity holding which means the probability of escaping the cavity is the same as for a single 'unpaired' photon - vanishingly small.
    Which points are just rehashed from post #2.
    Also, the anti-phasing argument could not work unless also propagation vectors k are in exact alignment, but a truncated cone cavity would not facilitate that.

    Keeping going; their dark band interference argument obviously fails since conservation of energy requires corresponding bright bands - but there are none exterior to cavity. As standard theory demands. Standard theory is missing that the momentum analogue to Poynting vector is best understood as an identity relation not a force/momentum density balance equation. Even though in almost all cases the latter works - but not always. As manifestly evident in certain long known field solutions - consequences of which are hidden in plain sight. One has to shift thinking from photons to EM interactions between moving charges. Nothing to do with 'vacuum virtual plasmas' or 'Unruh radiation experienced by cavity photons', or other such speculative nonsense.
     
    Plazma Inferno! likes this.
  14. paddoboy Valued Senior Member

    Messages:
    21,647
    http://www.popularmechanics.com/science/energy/a22678/em-drive-cannae-cubesat-reactionless/

    Enough argument. It's time to actually test this crazy thing.
    The EmDrive, a hypothetical miracle propulsion system for outer space, has been sparking heated arguments for years. Now, Guido Fetta plans to settle the argument about reactionless space drives for once and for all by sending one into space to prove that it really generates thrust without exhaust.

    Even if mainstream scientists say this is impossible.

    Fetta is CEO of Cannae Inc, and inventor of the Cannae Drive. His creation is related to the EmDrive first demonstrated by British engineer Roger Shawyer in 2003. Both are closed systems filled with microwaves with no exhaust, yet which the inventors claim do produce thrust. There is no accepted theory of how this might work. Shawyer claims that relativistic effects produce different radiation pressures at the two ends of the drive,leading to a net force. Fetta pursues a similar idea involving Lorentz (electromagnetic) forces. NASA researchers have suggested that the drive is actually pushing against "quantum vacuum virtual plasma" of particles that shift in and out of existence.


    Most physicists believe these far-out systems cannot work and that their potential benefits, such as getting to Mars in ten weeks, are illusory. After all, the law of conservation of momentum says that a rocket cannot accelerate forward without some form of exhaust ejected backwards. Yet the drumbeat goes on. Just last month, Jose Rodal claimed on the NASA Spaceflight forum that a NASA paper, "Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum" has finally been peer-reviewed and accepted for publication by the American Institute of Aeronautics and Astronautics, but this cannot be confirmed yet.

    THE BACKGROUND
    Given that the drive seems impossible, Shawyer's work was largely ignored in the West, although he did ship a copy to Boeing's Phantom works in 2007. A Chinese team led by Prof Yang at Xi'an Northwestern Polytechnic took up the challenge in 2008. They published a series of theoretical and experimental papers, and by 2012 claimed to have produced a device producing a few ounces of thrust for a few kilowatts of input, comparable to conventional ion thrusters.

    Propellantless drives next hit the headlines when NASA's maverick Eagleworks team tested several different versions, including two built by Cannae. They reported positive results to widespread disbelief and questions over their experimental techniques. Their work continues and is reportedly undergoing peer review, an essential process for scientific credibility; most believe that it will fail.

    Martin Tajmar, a physicist at the Dresden University of Technology, investigated the effect in 2015. Previously Tajmar had shown that claims that of "electrostatic torque"—the twisting force supposed to occur between charged spheres, was actually caused by the experimental setup, and that the alleged "gravitational shielding" was really due to an error in a gyroscope. Yet when Tajmar built his own EmDrive, he was surprised to find that it really did appear to produce thrust. He was not able to pin down any experimental error that might explain this.

    Various possible sources of error in these experiments—air currents, leaking microwaves, ionisation, photon thrust—have been ruled out. But given that the results appear to contradict known physics, it seems more likely that the experimenters have made a mistake than that physics is totally wrong. Hence all the of work into finding the flaw in the experiments.

    THE MISSION
    One way to cut through all the technical arguments about torque balances and eddy currents is to actually test the drive in space. If it fails, it fails. If it works, then physicists will have some explaining.

    A success would be a very big deal for the satellite business. Propellant is a limiting factor for low-altitude satellites, which need to produce thrust at intervals to counteract atmospheric drag, a process known as station keeping. Propellant can make up as much as half the launch weight of a satellites. Solar panels can provide power, but when a satellite's propellant runs it becomes useless.

    On August 17, Cannae announced plans to launch its thruster on a 6U cubesat. Each unit is a 10-centimeter cube, so a 6U satellite is the size of a small shoebox. Approximately one quarter of this will be taken up by the drive. Fetta intends the satellite to stay on station for at least six months, rather than the six weeks that would be typical for a satellite this size at a altitude of 150 miles. The longer it stays in orbit, the more the satellite will show that it must be producing thrust without propellant.

    Cannae has formed a company called Theseus with industrial partners LAI International of Tempe, AZ and SpaceQuest Ltd. of Fairfax, VA to launch the satellite. No launch date has yet been announced, but 2017 seems likely. "Once demonstrated on orbit, Theseus will offer our thruster platforms to the satellite marketplace," says the optimistic conclusion on their website.

    There is competition. In addition to the Chinese, and Shawyer himself, a lively open-source community of EmDrive enthusiasts has sprung up. They're building their own drives, and the online discussion is on nasaspaceflight.com now runs to many hundreds of pages of informed technical comment.

    Making a drive is cheap enough, although it does require a high degree of precision. Getting it into orbit is another matter. Engineer Paul Koclya of Aachen in Germany has built a miniature EmDrive which fits in a PocketQube cubesat. He believes he could get it into space on a commercial launch for less than $30,000, and has launched a crowdfunding campaign to raise the money. "If it works, it will bring Star Trek technology into real life," Kocyla says on his funding page.

    If.

    Meanwhile, theoreticians continue to make new suggestions to reconcile propellantless thrusters with known physics. Michael McCulloch of the University of Plymouth in the U.K. has suggested a solution involving "quantized inertia" which is based on a respectable if unproven phenomenon called Unruh Radiation. A Finnish team recently published a peer-reviewed paper proposing that such a drive could work because of an unseen exhaust of paired photons that cancel out each other's visible effects but still carry momentum.

    A good and easily-proven theory would certainly make it easier for the scientific community to take claims of propellantless drives more seriously. But what really matters is whether Cannae can really get the drive to work in space. The payoff would be impressive—but it would be a success against long odds.
     
  15. The God Valued Senior Member

    Messages:
    3,546

    Wave theory, "interference" is wave nature of light not particle (photon).
     
  16. The God Valued Senior Member

    Messages:
    3,546
    So Paddoboy, mainstream reputable scientists say that it cannot. Do you agree that EM Drive is nonsense?
     
  17. paddoboy Valued Senior Member

    Messages:
    21,647
    No known laws of physics will or are broken.
    The result of the experiment, we'll just have to wait and see, won't we?
     
  18. Q-reeus Valued Senior Member

    Messages:
    2,603
    Wrong. As I and many others elsewhere pointed out way back, any nonzero 'propellantless thrust' automatically violates energy-momentum conservation. Only someone grossly ignorant of SR implications would believe otherwise. Roger Shawyer is another such one.
     
  19. paddoboy Valued Senior Member

    Messages:
    21,647
    No correct my friend...Read again what I said. I said no known laws will be broken.
    If this thing doesn't work, I'm right:
    If this thing does work, than their is an as yet unknown reason, but no laws will be broken.

    Please Register or Log in to view the hidden image!

     
  20. paddoboy Valued Senior Member

    Messages:
    21,647
    http://scitation.aip.org/content/aip/journal/adva/6/6/10.1063/1.4953807

    On the exhaust of electromagnetic drive

    ABSTRACT


    Recent reports about propulsion without reaction mass have been met on one hand with enthusiasm and on the other hand with some doubts. Namely, closed metal cavities, when fueled with microwaves, have delivered thrust that could eventually maintain satellites on orbits using solar power. However, the measured thrust appears to be without any apparent exhaust. Thus the Law of Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster’s cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagneticfields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum,gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired-photon conclusion.

    Discussion:
    We reason that the thrust of EM drive results from the efflux of photons that have paired with opposite phases. The paired photons are without net electromagnetic field, and hence they will escape from the metal cavity. This loss of momentum, when anisotropic, produces the thrust. Thus, our explanation complies with conservation of momentum but departs from the current consent about photons by regarding photons as indivisible and indestructible basic building blocks of nature.

    We acknowledge that our proposal for the paired-photon exhaust is by no means an exclusive explanation. At the same time we recognize no observation and no measurement that would disprove it. Expressly, we recall that Lewis’ view of the photon57 as the elementary constituent was seen to be in conflict with an atom decay from a given initial state either directly due to the loss of a single photon or via two intermediate states due to the successive losses of three photons nevertheless ending up to its ground state with the specified number of quanta. However, this early rejection of conservation of quanta seems to us unwarranted because it does not keep track of quanta in the form of paired photons between the system and its surrounding vacuum.

    Our understanding about the EM drive’s thrust follows from comprehending the physical character of vacuum, and thereby also gravity and inertia. This insight could be useful in improving electromagnetic drives and help to examine other ideas of propellantless propulsion.
     
  21. Q-reeus Valued Senior Member

    Messages:
    2,603
    Without needing to rely on any formal 'proof' e.g. Noether's theorem, a simple gedanken experiment is sufficient to show energy-momentum conservation must fail if any nonzero thrust is present. Suppose an exceptionally effective emdrive can be made to hover against 1g gravity for x seconds. According to Shawyer there is only disssipative losses incurred, since no relative motion occurs. Now suppose the emdrive is horizontal on rails, initially motionless, then produces thrust of 1g for x seconds. It will accelerate to a final velocity of g.x m/s.
    Hence a gain of KE. Shawyer furnishes an 'equation' that predicts a concomitant extra power loss in the emdrive in latter case. However....

    By the equivalence principle the emdrive is incapable of distinguishing the two scenarios. Hence Shawyer and similar fools do not know what they are talking about.

    To add a pure SR twist to above, let the emdrive on rails have an initial velocity v before being switched on. The final per-unit-mass KE gain is now (g.x + v)^2 - v^2 which on expansion is easily seen to exceed the figure when starting from rest. An infinite number of alternate specific scenarios is possible and it's very doubtful any alternative weird non-relativistic theory concocted to avoid violation of energy-momentum conservation could do so consistently. Shawyer deludedly maintains otherwise.

    I just accept that such violation is a clear implication of certain well-established EM field solutions that have been in the literature for a long time.

    PS: I have already covered in #10 the failings of those you cut & paste quote in #17
     
    Last edited: Sep 5, 2016
  22. paddoboy Valued Senior Member

    Messages:
    21,647

    Please Register or Log in to view the hidden image!


    Let me repeat.........
    No known laws will be broken.
    If this thing doesn't work, I'm right:
    If this thing does work, than their is an as yet unknown reason, but no laws will be broken.
    If this thing is ever launched!
     
  23. Q-reeus Valued Senior Member

    Messages:
    2,603
    So paddoboy persistently pronounces ' no laws will be broken'. With such boldness and confidence, one should expect therefore an easy refutation of the simple arguments given in #18. What is your devastating refutation paddoboy? Repeating 'no laws will be broken' does not qualify.
     

Share This Page