EM Drive Paper Published By Eagleworks Team

There are one or two perennial scientific stories that sound just too good to be true, but if they delivered on their promise would represent a huge breakthrough and instantly obsolete entire fields. One example is so-called “cold fusion”, the idea that nuclear fusion could be sustained with a net energy release at room temperature rather than super-high temperature akin to that of the sun. We all wish it could work, but so far it has obstinately refused. As a TV actor portraying a space engineer of the future once said, one “cannae change the Laws of Physics“.

Another field of scientific endeavor that seems to push the bounds of credibility but is cautiously showing signs that it might deliver some of its promise is the EM drive. Take a metal cavity in the shape of a frustum (A cone with the point removed), and put a piece of dielectric material on the inside of the smaller circular end. Generate an RF field within the cavity, and there appears to be a small but measurable force exerted from its smaller end. This amounts to reactionless thrust, which is to say that there is no ejection of mass as you would see with a conventional thrust engine. Going back to those unchangeable Laws of Physics, either a process is at work that goes beyond current understanding of those laws, or people are being hoodwinked by things that are explainable through other means. Unsurprisingly, there is considerable work underway from teams of scientists around the world to investigate the phenomenon.

The most recent piece of this work that we can examine has just been published by a team working at NASA’s Eagleworks at Johnson Space Center. Their paper, “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum“, details their experiments with a frustum cavity on a low-thrust torsion pendulum in a vacuum. They present the interesting conclusion that their apparatus “is capable of consistently generating force at a thrust-to-power level of 1.2±0.1mN/kW1.2±0.1 mN/kW“. That’s a tiny amount of thrust for a lot of applied power, but for those wishing for a future in which EM drives might play a part it comes as an encouraging finding.

The paper is a fascinating read as it details the cavity, electronics, and experimental procedures before discussing some of the possible mechanisms. We are not quantum physicists here at Hackaday, so if there is anyone among our readership with a suitable background who would care to explain in our comments section some of the discussion, we would be very interested to read it.

We’ve discussed EM drives before, and one turned up as a Hackaday Prize entry. Will we be covering many more in the future, or do you think we’ll be writing one day about the paper that proves them to be a false hope?

131 thoughts on “EM Drive Paper Published By Eagleworks Team

  1. The comparison with LENR is apt. Yes something seems to be happening in both cases that is not easy to explain with current models. However neither case stands as proof that current physics is wrong and will not until absolutely every source of experimental error is tracked down and eliminated.

    1. Hackaday seems to consistently trash cold fusion, and yet 25+ years later, research is still being done in the LENR field. While it may not be fusion, it is difficult to dismiss all of the experimental results which often produce evidence of a nuclear reaction (e.g. transmutation, neutron production, helium production, excess heat).

      Scientific American has an interesting summary of the current research: https://blogs.scientificamerican.com/guest-blog/its-not-cold-fusion-but-its-something/

      1. The problem is not LENR per se – there are a number of these that are quite legitimate, like muon-catalyzed fusion that are being studied. The problem is with those that assume the Fleischmann–Pons experiment stands as definitive proof of fusion. Yes something is going on in these cells most likely explained by the Widom-Larsen theory which is consistent with existing physics and has nothing to do with fusion. However because of the hype and involvement of those with little scientific knowledge that were driven more by a desire that these results be true, as well as the mountebanks out to defraud them, real science was inhibited. Let us hope that this isn’t the case with this supposed thruster.

  2. The scope for error is just too great.

    Anything involving kilowatts of RF power is bound to induce currents in the device, which will create a magnetic field, which attracts other parts of the testing aparatus.

      1. Assuming 1kW (why 1.2kW?), and assuming full directionality (all photons emitted in the same direction) but assuming no reflection that results in: F=dp/dt=d(mv)/dt=c*dm/dt=c*1/c^2*dE/dt=P/c=1kW/3=(3*10^8 m/s)=0.0000033 N=3.3.. microNewton.

        allowing the photons to be shot in a wider cone of angles results in an even lower forces, but allowing reflections results in bigger forces (think of using a laser as a rocket, but recycling the photons with a certain efficiency by having a mirror as a launching platform…

        1. I would prefer to see the results of a non-torsion balance experiment, above a variable height RF retroreflector, and see a plot of the measured force as a function 2*height/wavelength (since lowering the retroreflector one unit of distance, displaces the device’s reflection 2 units of distance)

          1. Solar panels, a step-up transformer and a test engine. Radio for control & telemetry.
            The result is a SATELLITE and bypasses the lab to give real-world results.

            Put it in orbit : if it fails to produce thrust, eventually it gets dragged into the atmosphere. If it succeeds, it moves itself into higher orbits – and eventually breaks free. With a world of tracking dishes to verify the results either way.

        2. If enough expensive experiments turn out to be due to undocumented measurement apparatus internals interacting with the experimental setup, it will inevitably lead to future scientific papers explicitly naming brand and model of each device involved in the experiment, which in a sense form references to the measurement device design, available from the manufacturers paywalled internal “journal”.

    1. I agree. I want to believe this as well but having some experience with highly focused RF energy I have observed things moving by enduced fields of seeming unrelated objects at suprizing distances myself. At those frequencies and power levels our ability to conceptualize what is happening in real time gets a bit weak. I want somebody to actually build the propellantless satellite and really test this thing. If all we have is empirical evidence, and the physics is not fully fleshed out let’s cut straight to the practical and see if we can work backwards to reveal some possible avenues of investigation.

        1. Everybody seems to think they measured at 1kW of power…. Or thereabouts.

          They measured at 40, 60 and 80W. They got a nice linear relationship between the power and the measured force. They did a good job of trying to eliminate all sources of error. One of the easiest tricks in the book is: if you turn the device around does it want to go the other way. Answer: yes.

    2. those are however quantifiable and there is nothing that prevents it from being taken into account, i haven’t read the paper so i don’t know if they did.

      i also dont know if it is kilowatts of used power or kilowatts of rf power, makes quite a difference.

      1. I’ve read the paper. They accounted for current: twisted pair everywhere and between tests power cables were in the same position, just orientation of drive changed. They registered opposite force with opposite faced drive, there was no bias in one direction. Also drive pointed at pendulum axe did not register torsion.

        Also they used 80 watts of power. They measured em-fields in chamber to account for leakage from device and they were on the level of typical gsm phone.

        They have accounted for all known measurement errors, they have a result of 1.2mN/kW with 0.1mN/kW measurement error. They even saw error caused by heating of drive, but they could extract this effect consistently both in air and vacuum tests.

        1. NO. They BELIEVE they have accounted for all known sources of error. When anyone starts uttering absolutes in cases like this warning flags go up. There is still a long way to go here including having this experiment repeated from scratch by other, independent investigators.

          1. Any net-DC loop current around the resonator will produce a magnetic moment in the apparatus that will torque against the geomagnetic field (and other magnetic fields) and will show the observed reversal of torque when the resonator is in the reverse-thrust configuration.

            This net-DC loop current could be caused by, e.g, rectification in the joints between the segments of frustum. (Shottky junction from corrosion on the copper segments.)

            I am not saying that this is the cause of the anomalous torque, just that it is a source of error that is not explicitly addressed in the paper.

            (Yet another ‘report comment’ click while attempting ‘reply’.)

          2. The onus is not on any critic to provide evidence refuting these (or any claim) rather it is on those uttering them. “Prove me wrong!” is the cry of every crank and demonstrates only that they have no grasp at all of how science works. At any rate, in my original comment I wrote that this has to be verified independently and that would be the case regardless as the easiest person to fool in any experiment is the experimenters themselves.

          3. “The onus is not on any critic to provide evidence refuting these (or any claim) rather it is on those uttering them.”

            This is only true when someone only has a claim. The EM drive people have a claim based on observed effects in the real world. Critics have to deal with explaining how that exists just as they would have to explain that gravity doesn’t exist in the presence of falling apples. Physics doesn’t define the world, it explains it.

            At the same time their claims can’t be taken as gospel until tests are designed that satisfy all specific critiques. Im a fan of getting past all this earth bound stuff and flying one into space. Then we can see how the whole system reacts without having to imagine all the possible hidden force errors.

          4. @david palmer

            It’s not terribly difficult (though not cheap) to build a faraday-esque cage to cancel out the geomagnetic field. This is fairly common in materials study & some fields of geology. This should certainly be done for this study.

          5. @mystixa – No critics don’t have to explain anything at all until these results have been proven, ideally by third-party replication, and furthermore only after it has been firmly established that there is no other confounding errors or explanations that fall within the scope of standard physics. Nor, I might add is flying this apparatus going to prove it, doing so will only will only add to the experimental data. If there is anything at all to this effect it is going to be a long hard road.

          6. Laws of physics are quite robust and have been tested over and over again, the EM Drive hasn’t had the same rigorous testing. I’m not saying that it isn’t worth investigating because it should be investigated over and over again. I just think that the likelyness of an outside variable being to blame is more likely than this device breaking the laws of physics. With all that said I really hope it does work and isn’t some other variable to blame, It’s not everyday you get to rewrite the textbooks.

        2. Disregarding the fact that torsion is hardly mysterious, I find the way they use a torsion balance bizarre: they stop the pulses before the balance has been allowed to reach … balance!

    3. 60 or 80 watts of RF power is what they used; you’d realize this, if you’d actually bothered to read the paper. Don’t go throwing around “kilowatts of RF power” when they got valid data without using that power.

    4. >which attracts other parts of the testing apparatus,
      why should this be always in the same direction ? Those guys aren’t w.e. arduino makers

      Also magnetic field is about current, not power.
      100mA into a 100k resistor is 1kW with very low magnetic field

    5. I recall the regretful acceptance of our highly talented antenna design team when they tried to get a ‘perfect’ antenna. Seems that any real metallic construction will have some sort of rectification going on creating intermodulation between different signals in the antenna. They got to some pretty low levels of intermodulation, stopped there and wrote an internal White Paper for the guidance of future engineers.
      Kudos to the Eagleworks team, they have measured results and they have published them. Even if the effect turns out to be not what we all want they have advanced science.

  3. My knowledge of physics breaks down rather quickly at this level but one thing I’ve wondered is if there’s some heretofore unknown mechanism whereby EM energy is converted to momentum more effectively through the dielectric side of the cavity.

    If there’s some mechanism that allows for generation of photons (or some similar ‘particle’) within the cavity in all directions and then capture that momentum in all directions except the dielectric. I’m sure there’s something I don’t know that makes this possibility already excluded.

    The reason I am cautiously optimistic about this technology is because it has it’s origins in unexplained movement anomalies of satellites. Even if this doesn’t yield a new propulsion technology the explanation for the anomaly will benefit our scientific understanding.

    1. What you are describing is a photon rocket, which Error Sources 8 of the paper addresses:

      “The eighth error photon rocket force, RF leakage from test article generating a net force due to photon emission. The performance of a photon rocket is several orders of magnitude lower than the observed thrust. Further, as noted in the above discussion on RF interaction, all leaking fields are managed closely to result in a high quality RF resonance system. This is not a viable source of the observed thrust.”

      As another section puts it,

      “The 1.2  mN/kW1.2  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  μN/kW3.33–6.67  μN/kW (or 0.0033–0.0067  mN/kW0.0033–0.0067  mN/kW) range.”

      I think the Hackaday editors, for complex topics such as this, should force commenters to prove they’ve actually read the linked article before spewing useless physics memes into the comments.

      1. lol… “in the 3.33–6.67  μN/kW range” this is not really a range, but rather the theoretical value for 2 different cases:

        ideal emission of photons in one specific direction (cone of 0 degrees). for example a laser: value is 3.33μN/kW

        ideal reflection of a unidirectional stream of photons in the reverse direction (i.e. retro reflection) for example laser shining on a light sail: value is 6.67  μN/kW (exactly double the previous value)

        lower values are possible if the light source is not exactly unidirectional
        higher values are possible if a sizable fraction of the photons undergo multiple reflections, hitting the projectile multiple times from the same side…

  4. I don’t under stand what the problem is.
    You are putting energy in so yes you will get something happening coming out
    If it was a solid fuel or electrical power.
    I was tot that if we had the technology, you would be able to convert energy to matter then what is stopping you from turning it into thrust.
    For me its a no brainer and common sense.
    And I agree with the person earlier to just do it. And prove that it works.
    I believe we are at the point to try and stop wasting money on the ground trying to prove it.
    Sometimes you have to run before you walk.

    1. The problem is that they’re not merely trying to prove that -something- happens, but that a particular effect exists, which is supposed to prove some pseudoscientific theory behind the EmDrive.

      1. That’s not quite fair. Right now they are working the hypothesis and those can be framed outside standard theory. It only becomes pseudoscientific when it is asserted as true when in the face of no or countervailing evidence.

        1. You can easily spot pseudoscience:
          1) free energy/treatment/… for everyone…
          2) …but big oil/pharma/… are in a conspiracy to bury the technology for their own evil interests
          Give it a couple of years and see if the illuminati shuts it down…

          1. Well.. #2 is actually true occasionally of which the Auto Industry is a frequent example. Can’t think of anything that isn’t in the ‘Damnit, that’d be a nice feature’ category and we know they have it locked up because they patent the technology and make it public info, and just work the tech into their 15 year plan with the business logic of making sure there’s always a new feature of some sort for next year’s model. It definitely gets back into conspiracy theory territory when someone suggest the companies have the world changing discoveries being tucked away in some scientist/engineer’s notebook they bought up.

    2. The issue is that current physics requires conservation of momentum – in laymans terms you have to push against something.

      In air/water/space there is nothing solid to push against so every thruster we have ever built requires ejecting something out, and in space that means carrying around expensive and limited propellant. Even propellant-less systems like laser/photon drives eject photons which have momentum, but the efficiency is poor. This drive appear to eject *nothing at all*, but is two orders of magnitude more efficient than photon drives. It could revolutionise space travel, but we cannot explain the principle behind it’s action and how it circumvents known laws of physics.

      1. I keep seeing people bringing up conservation of momentum in this discussion, but I thought the prevailing theory behind the EM drive was that the emissions inside the box were hitting short lived virtual particles / quantum foam (see the Casimir effect), and losing momentum to them, resulting in a net difference between the force emitted at one end of the cavity and the force exerted on the other end.

        Am I misinformed and this couldn’t explain the thrust? Am I behind and this theory has been disproven? Or is this theory still a possible explanation?

        1. As far as I’m aware the underlying mechanisms are only a conjecture/hypothesis. From a macro/classical physics perspective it still seems to violate conservation of momentum, which is why it is so contentious.

    1. “The 1.2  mN/kW1.2  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  μN/kW3.33–6.67  μN/kW (or 0.0033–0.0067  mN/kW0.0033–0.0067  mN/kW) range.”

    1. Assuming it was in an atmosphere of the right pressure. A peltier element in a semi-decent (read not particularly high) vacuum would act a lot like the fin on a radiometer. Too good a vacuum though, and the radiometer doesn’t spin at all. Not that useful as a space drive.

      1. The total momentum p of a unidirectional stream of photons with a fixed total energy E is independent of wavelength/frequency:

        * 2 photons of frequency f have total energy E=h*f + h*f=2*h*f while a single photon of frequency 2f has energy E=h*2*f
        * 2 photons of frequency f have total energy E=h*k+h*k=2*h*k while a single photon of frequency 2f has energy E=h*2*k

        Another way of viewing it is: the speed of light in vacuum is fixed, so a segment of a directional beam of light has a fixed velocity c, and a mass E/c^2 hence a momentum of E/c, independent of frequency.

    1. From the paper, because you clearly can’t understand physics (or English) unless it’s provided in video format:

      The eighth error photon rocket force, RF leakage from test article generating a net force due to photon emission. The performance of a photon rocket is several orders of magnitude lower than the observed thrust. Further, as noted in the above discussion on RF interaction, all leaking fields are managed closely to result in a high quality RF resonance system. This is not a viable source of the observed thrust.

      1. The equations for photon rockets assume an approximate infinite vacuum, and recycling photons is cheating.
        Here RF photons could bounce back and forth between Test Article and Reaction Mass (Earth with static lab equipment). The same quantum of energy (photon) could provide multiple collisions between reaction mass and projectile..

        I don’t think we can rule RF interaction with environment out as a viable source of the observed thrust

    1. This is it. There may well be some interesting science that could come out of this and LENR research that might not break physics but be marginally useful just the same, but the overhype and involvement of the Free Energy cult will drive off many legitimate investigators who don’t want to be tarred by the nonsense.

      1. That in itself is a very dangerous precedent. Cults are easily drawn into any type of “magical” newly paradigms… it should not let science get distracted.
        The salty backlash against this from so called science minded people is bad, but not as bad as these types of people to tactically attaching cults to automatically dismiss ideas from peer review all together.

        The drive does something… deal with it.

        1. It has not been established that this drive does anything. Please try to understand that demonstrating an anomaly proves nothing in and of itself. This is an interesting result and it certainly bears closer examination, but based on the paper itself any claim that all potential sources of error have been accounted for, and all other explanations within the scope of the standard model can be eliminated is simply wrong.

          1. No serious critic, (and certainly not me) is suggesting that there isn’t an observed experimental effect here, the difference in our position is that this is all that can be stated with any assurance, and thus at best is a small step forward. It is those that feel this drive is ready to fly that are going off half-cocked here, and their desire to push this too fast is more likely to put this research in danger than it is to advance it. Testing this device in space is not going to be cheap, nor do you want it to be done cheaply because if it fails to show results FOR WHATEVER REASON, the whole project will effectively be dead. No one is going to risk their career supporting it after that and it is all but over. Particularly because it will become a cause célèbre with the fringe and legitimate researchers won’t go near it again.

            Yes something is there, yes it needs to be examined, but exactly like the excess heat anomalies seen in early cold fusion experiments, if people start making wild claims without support and whipping up a frenzy they risk damaging the project. Slow, steady work is the only way to go when you are swimming up current in science.

    2. Ah yes the free energy cult as bad as the cynics that can’t design an experiment that disproves the hypothesis and who resort to name calling and worn out cliche. I would think if you could design a non frustum that shows thrust it would provide significant evidence to this being BS. Or use different materials that show a more reasonable amount of thrust per energy input then it could be more likely to actually be working.

      I highly doubt anyone who points to the “laws of physics” as a counter theory actually understands them well enough to be more than a cultist themselves.

      1. Beyond the fact that there is a chorus of people whose status clearly indicates that they indeed understand the physics voicing doubts, consider what I wrote above: given the social politics that all science has to work in, too much hype too soon, and too much attention from cranks can kill an idea dead in the water regardless of how interesting it might be. The fact is this sort of attention drives researchers off, because it makes getting funded difficult and leaves them at risk of having their reputations tarred by the antics of charlatans, mountebanks, and nut-bars. If you really want to see progress continue in this field, the very best thing is to demand that everyone involved have their feet kept close to the fire, and demand that every result be scrutinized as closely as possible. Real progress is slow because it must be or there is a serious risk this whole line of inquiry will be dropped NASA or no NASA

        1. it doesnt help that anyone who has the reverse bias keeps shouting pseudoscience when as far as i can gather plenty of actual science is being done, remember that this is in principle a replication study and it found positive results, thrust was produced, now people need to stop the hyperbole in both directions and we need to find the error in the experiment or an explanation, personally i will believe it when i see it working in a practical sense, show thrust in space with no medium and in interplanetary space, since electrodynamic tethering works practically in a strong magnetic field we need to minimize the risk of that having an influence.

    3. It is hardly free, even if you pump a megawatt of energy into it you get the thrust equivalent of a punch in the face. See my comment above there is no magic required.

      Where it does matter is when you have it driven from a fusion reactor and you have enough fuel to run it continuously for decades. So assuming my back of the brain rough calculations are correct, even if your acceleration is a tiny 1 cm/s^2 after a decade your velocity is well over 10 million kilometres per hour and you have travelled almost a light year in the first couple decades. But why would you start from zero when you could launch it from an orbital railgun and start at 10,000 km/hr?

      i.e. if NASA get this working right we could see them launching AI controlled interstellar probes around 2050.

  5. While this is a potentially interesting scientific curiosity, I’m waiting for it to get out of the megawatts per micronewton range. If this can’t produce an easily seen, unquestionable effect with a reasonable amount of input power, it’s not the space drive of the future, even if it DOES turn out to be a real effect. The fact that the actual effect is below the threshold of the potential errors and only shows up when the errors are filtered away means we’re not there yet. No one had to worry about Goddard’s early rockets, even before they produced useful thrust, being potentially a bit magnetic, warmer on one side than the other, etc.

    1. Those rockets? It’s like a hot air balloon. That much heat has to heat the air which produces the lift. Can’t believe people are falling for this ‘reaction mass’ pseudoscience… ;p
      You can’t even repeat the experiments, the things burn themselves up to hide the evidence.

      1. I assume you mean ‘reactionless’ pseudoscience? The most common interpretations of physics maintain action-reaction forces, so to apply a force on a projectile an equal opposing force on a reaction mass is necessary (photons have mass/energy, but no rest mass, a photon at rest would have frequency 0, wavelength infinite).

        It’s like you were either thinking ” ‘reactionless’ pseudoscience” but instead typing ” ‘reaction mass’ pseudoscience” or you are quoting someone who said ‘reactionless’ which you understood as ‘reaction mass’?

    2. Megawatts per micronewton? You have, rather spectacularly, gotten the units backwards and the measurement off by a factor of a million.

      They measured 1.2 millinewtons per kilowatt, or 1.2 newtons per megawatt, or 1.2 micronewtons per watt, because you clearly don’t understand unit conversion.

      “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 0.0033–0.0067  mN/kW range.”

  6. My knowledge of physics is extremely limited. But I wonder if the device is not stripping material from itself, in extremely small quantities, So there would in fact be a propellant, the thruster body itself. It seems there is allot of energy being pumped into the device, aren’t high voltages capable of ripping material off of the anode?

    1. They accounted for that in the error analysis, and found that the total errors from all possible sources they could think of was an order of magnitude below the actual thrust. Besides, they tested with 40, 60 and 80 watts, and nothing got hotter than 90F. Not a lot of energy there.

  7. This leaves me with a few questions: Do photons leaving a light source result in a (equal and opposite) force against the source ? If so then couldn’t you have a “massless” drive just using a laser. On the other hand if there isn’t a force generated then point the photons a “solar sail” ( https://en.m.wikipedia.org/wiki/Solar_sail ) and tow the light source with the sail ? Surely its one or the other ?

    1. Those photons come from somewhere, and have mass, so it’s not massless if they leave the drive. In theory, the Em Drive contains it’s photons within a sealed cavity yet still generates thrust (no mass leaving the system).

    2. Yes, photon drives are real, but their thrust would be two orders of magnitude less than the effect they measured with the EM Drive. This was included in the error sources in the report.

  8. “Going back to those unchangeable Laws of Physics, either a process is at work that goes beyond current understanding of those laws, or people are being hoodwinked by things that are explainable through other means ”

    Explainable by other means could still be significant in itself though.
    A unknown effect – ie a “thing” present that is as yet not understood.
    Not necessarily the same as physical *laws* being wrong.

    Think how dark mater and dark energy are introduced to explain away differences between observation and predictions of gravitational laws.
    You still need good evidence, of course, but “this is something that breaks physics!” vs “this is nonsense” is too extreames with a world of something inbetween.
    Like me looking at a crystal radio when young and thinking “wheres it getting the power from?!?!”. I simply has missing information.

  9. The saying goes “Extraordinary claims require extraordinary evidence.” Well folks, here’s the extraordinary evidence. Respectable researchers, respectable institutions, rigorous experimental evidence.

    The only thing that can refute that it exists an even better experiment. The bar is quite high now. I wonder how high it will go?

  10. “…We are not quantum physicists here at Hackaday,…”
    Judging by the comments, your readers are?

    “Extraordinary claims require extraordinary proof.”–Carl Sagan

    “The weight of evidence for an extraordinary claim must be proportioned to its strangeness.”–Pierre-Simon de Laplace

    1. I will see your Sagan and Laplace, and raise you a Feynman.

      “It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.” — Richard P. Feynman

      I’m getting really tired of all the armchair physicists criticizing this paper by blindly and religiously citing misunderstood scientific “laws”, especially without understanding that a scientific “law” is not a fundamental requirement by the nature of the universe, but rather a useful mathematical description of some phenomenon that is approximately correct under a specific set of assumptions.

      I’ve seen all kinds of misused high school level equations thrown around to refute the claims, and someone above even makes a claim that photons have mass. I have yet to hear any comments from others who actually know and use physics correctly in their arguments.

      Here’s the state of the EM drive: someone makes a rather extraordinary claim of obtaining a reactionless thrust with an asymmetric microwave cavity. Crazy ideas (none any crazier than dark matter and dark energy, to be honest, since we have absolutely NO evidence they exist) were thrown around to explain it, while skeptics scoffed and insisted they were doing their science wrong. Outside research groups, meanwhile, try it themselves, improving on the experiment, and also claim to get thrust. Most recently, a group of NASA scientists do the same, also get thrust they can’t explain away, and do so at a level that passes peer review. The evidence for thrust is not going away, and no matter what you believe are the”laws” of science, they are no good unless they can explain what this experiment observes.

      Now, there may still be an explanation for the observation that precludes this drive working. Just as for the FTL neutrino case, there may be a subtle effect going on that everyone’s forgetting to check. But the significance of this paper is that they’ve addressed the obvious potential errors, and still have a resulting thrust. It’s fine if you want to believe it’s not real, but your explanation for why not darn well better explain why they get the observation and not just fallaciously appeal to authority in your poor understanding of scientific “law”.

      1. Because that isn’t the way it works, it has never worked that way in science, even when they were right those extending a novel theory have always had to run the gauntlet. You just can’t say “I see this, prove me wrong, or accept my explanation.” The fact of the matter is that you cannot heap enough insults on critics to make them change their minds, you have to prove that the explanation you are extending is a better one than any other, and frankly that is not the case here. That is not to say the whole thing is an illusion, but any assertion that this drive has been proven to work at this point is highly premature. Furthermore, as I have written several times in this thread, you are doing this research far more damage with this “I want to believe” boosterism than any critic could possibly do , because if there is one thing that will keep this from being taken seriously it is going to be a mob of cranks demanding that it be accepted as real as it stands.

        1. Wow! You’ve simultaneously missed my point and proved it! Way to go!

          The fact is, we now have a peer reviewed paper showing an observation of thrust in this system. Nowhere did I say you have to accept the crazy ideas that have been put forward to explain how it works; rather, my statement was that if you are going to claim that your (understanding of) classical theory is right and the thrust isn’t real, then you have to be able to use that theory to explain what they have observed. If you can’t, then I’m sorry, but your theory (or at least your understanding of it) is wrong. There are no sacred theories in science, and there never have been.

          What I’m frustrated by is the ubiquity of posts like yours that (implicitly) claim to be knowledgeable, but then demonstrate clearly to anyone who is actually a scientist that your shallow understanding only goes as deep as what is popularly espoused. Note, I’m jumping to conclusions here. I don’t know you; perhaps you are, like myself, a published, professional scientist. If so, then I’ll invite you to up your game and start behaving like one. If you truly believe that the thrust is an error in measurement, then put forward what you think may be the factor they missed and how it accounts for their observations. Then we can discuss that idea and, if it has merit, test it. Because THAT is how science works and has always worked.

          And for the record, I personally believe they have more to do to say anything more than that they have observed thrust. Whether that thrust is actually present needs more testing.

          Terminology useful for those who aren’t actually scientists:

          Law: a mathematical equation that describes an observation. Does not necessarily have any bearing on reality, other than being approximately accurate enough to be useful under certain certain conditions. E.g. Newton’s “law” of gravity: F = -G m1 m2/r^2. It’s not how the universe works, but it’s close enough to be useful at low speeds.

          Theory: a collection of observations, laws, and relationships that, collectively, describe a system’s behavior. Not an untested idea, but rather is generally well supported by rigorous scientific testing. E.g Darwin’s theory of evolution: while still reliant on approximations, it has proven robust enough to garner general acceptance by anyone who has given serious enough study to the topic to understand its evidences and implications.

          1. Part of the trouble here is that supporters are so hair-trigger defencive that they see criticism and denial where none exist – in other words I don’t think you understand the points I’ve been trying to make. Please read all of the posts I have made in this thread before the one you are going off on, I have not stood on a “shallow understanding only goes as deep as what is popularly espoused.” In fact I have gone out of my way and avoided any specific criticism of the paper in question, which as a a published, professional scientist yourself, must realize is not free from defect. In fact I believe I have given this report as much benifit of doubt as I can under the circumstances.

            Look I spent the better part of a forty year career being involved off and on in work concerned with hydrogen embrittlement of high nickel steels. Diffusion of hydrogen into metals is a huge issue in any number of technical domains, and it is not completely understood. Further exploration of some of the effects that were occasionally seen original electrochemical cell that was claimed as evidence of cold fusion might well have yielded some useful insights into hydrogen’s effect on intergranular structure. However the hype and wild claims based on some very marginal observations and assertions that we were only a few years from a new energy economy that were seen as excessive in the light of subsequent failures drove many to treat the whole subject as an anathema. Unfortunately some of that slopped over into hydrogen embrittlement research.

            All I am saying is that everyone needs to take a measured approach to the EM drive subject and watch that this well not get poisoned the same way. Let things take their course, the naysayers will be proven wrong, if they are by better, repeatable results, not by trying to shove one paper down their throats. Let the system work the way it is supposed to or it will be turned into a field that no one wants to be near and that is not what you want.

          2. Well, that we can agree on. =) I apologize; I certainly did not do my due diligence in reviewing your specific comments among the slew of the various overly-passionate statements I’ve seen here and in other places. (I’ll be fair–my comment is probably overly passionate as well.)

            We both seem to agree that people need to chill and take the results with a hefty kilo of salt. I would say that the people who are inclined to immediately jump on the science-quackery witch hunt need to chill too.

            This paper does have problems, but despite those problems it made its way through peer review. As such it deserves to be treated for what it is–a genuine observation that at this point is inexplicable. My reaction has been to the slew of comments that immediately dismiss the existence of this observation “because momentum conservation!” without making any effort to understand what conservation of momentum actually means and how it applies to this result. So many people (likely unknowingly) treat science as a religion, and present themselves as authorities when they couldn’t even take a derivative to save their life.

            In any case, I’m glad you stuck with me long enough for the two of us to come to a consensus. In the end, we are both right. This result is being media-spiked as more than it really is, and the loudest population of skeptics don’t know what they’re talking about. In the end, we all need to understand that experiment and observation always trumps theory (though it can take a great deal of effort to prove that an observation really does contradict a theory!).

          3. Apology accepted. I agree that the noise level has gotten so high that it is hard to sort out positions. I also agree that those that are being reflexively dismissive are not contributing to the conversation but, at least in my experience, they are not as great a problem going forward as those that so desperately wish these things to be true that they try to prevent disagreement. In other words there is no place in research for any doctrinaire approach from either direction.

      2. “I’ve seen all kinds of misused high school level equations thrown around to refute the claims, and someone above even makes a claim that photons have mass.”

        I think you are referring to one of my posts. It is a typical mistake by people to think energy can be physically converted into mass and vice versa. The conversion is not physical but numerical, all energy has mass.

        And yes photons have mass, or do you claim they do not carry energy? They just have zero _rest_ mass.

        About “all kinds of misused high school level equations thrown around”, people who have studied physics understand the utility of occam’s razor. Credibility does not stem from the advancedness or complexity of the arguments, but of the most minimalist complexity necessary so as to explain something _still_ correctly to the widest audience…

  11. Well at least there are some details, and it’s one step closer to something that is peer-reviewed and an experiment that somebody can independently try and reproduce. It’s a big step up from nothing being published at all.
    Unfortunately when you have a big, expensive, very specialised apparatus (giant vacuum chamber, lots of vacuum feedthroughs, microwave electronics and kilowatt-scale microwave PA, very sensitive torsion balance etc.) it’s very difficult to find somebody independent who will try and reproduce it.

    The discussion section seems very handwavy and full of snake oil red flags in the quantum mechanics. In particular, it seems to rest on one particular interpretation of quantum mechanics to make it work – what happened to “shut up and calculate”?
    The interpretation of quantum mechanics is largely a question of philosophy – the world of experimental physics and engineering of real devices should be invariant, regardless of whether you believe in Copenhagen, or relative state, or pilot wave etc.

    1. There’s also the issue of getting other people to EXACTLY replicate experiments. That’s one thing that put a damper on ‘cold fusion’, nobody would EXACTLY replicate the original experiments that produced the anomalous results.

      Find a copy of “Butter Side Up!” by Magnus Pyke and read the chapter on using water going down drains to observe the effect of Earth’s rotation. There were many researchers building tanks of various dimensions and using different procedures – but nobody EXACTLY reproducing another person’s experiment to see if they got identical results. So some said the Coriolis effect of Earth’s rotation was observable on a small scale, while others called it BS – because their procedures introduced effects that damped or overwhelmed the very slight effect at that small scale. The ones who got consistent results – the expected swirling in a counterclockwise direction in the northern hemisphere – allowed the water in their test tanks to settle for very long periods of time, shielded from drafts and temerature differentials. One even filled his tanks with the water flowing in a clockwise direction before letting it settle so there’d be no possibility of any residual counterclockwise current. When he pulled the plug he got a counterclockwise swirl.

      What seems to be especially prevalent is researchers who vehemently disbelieve experimental results and “replicate” an experiment with big alterations they claim are attempts to “improve” on the original test but are actually designed to ensure it cannot work, then write a paper “disproving” the other guy’s work.

      You cannot prove or disprove squat, or attempt to improve results, without first exactly replicating the original – especially when the observed results are very small.

      1. Nonsense. If an effect is robust it will show up as long as the underlying conditions are met. In fact slight changes are one way of exposing hidden experimental error. Furthermore the Fleischmann–Pons experiment was exactly duplicated (it wasn’t that complex) by many, many investigators in the first few weeks following the announcement with variable results being reported. It was the fact that calorimetry under these conditions is more art than science and is fraught with sources of potential error and that other evidence was falling inside their error bars that brought the initial results into question. In other words: repeating the same set of mistakes is not replication and does not verify anything of value.

  12. So if you want to power a huge ship using this system, you will require A LOT OF POWER, the EM drives will also produce magnetic fields and radiations – and this is how we enter the hazardous area. The solution is to power many (tens of thousands of) tiny EM drives in parallel in order to avoid trouble.

    1. “this is a bunch of fringe engineers playing physicists”
      oh wow, that does explain why they use a torsion balance as a hinge, instead of letting it settle to rest…
      like kids jumping on mechanical scales, so the dial overspins, to show they weigh heavy
      or standing on their toes to get on a theme park ride.
      I can understand engineers getting frustrated when the physics community refuses to take the measurements seriously, but if one wants to convince the skeptics then one has to use the measurement apparatus in the way it is designed to be used. Measure the torsion balance’s constant, and for each level of power input, let the torsion balance settle, only then write down the deflection as a function of power input.

      When the gravitational constant was first experimentally measured on earth with heavy weights on a torsion balance, and a nearby heavy weight fixed in the lab’s frame of reference, the experimenter did not do any antics in the style of quickly placing and then quickly removing the nearby static weight, and observing the effect on the torsion balance… no, the experimenter placed the weight at different distances, each time letting the torsion balance [noun] … balance [verb] before writing down the deflection…

        1. A torsion balance experiment… without measuring nor mentioning the measured torsion coefficient?

          Check out figure 8 for example, theres the calibration pulse, and then the RF ON, its supposedly starting to push against the torsion balance, the angle is increasing, and its still increasing steeply when it is turned RF OFF?? why don’t they keep it on until it settles? … or would it settle at 0 deflection at rest? who cares if the DUT expands a bit in size, even if it doubled in size, it would be more convincing to show the plot where the deflection settles to a stable value before shutting off the DUT. Half of the error sources could be excluded if the torsion balance had been used to balance the torsion with the supposed force on a lever…

  13. There’s really nothing new to see, and its no more proven than it was before: NASA and a testing group in Germany both argued that any sort of thrust output shown in the range Eagleworks is showing is easily explained as sensor error or induced Magnetic anomalies.

    And at the end of the day, right now, the EM drive is producing so little thrust (if it arguably is thrust at all) that is makes it a null point: It would provide less thrust than just the thrust provided by photons hitting the spacecraft itself.

    Its still an unproven, and frankly, tired subject. Because nobody has proven anything.

      1. To actually verify the force to be a 100 times greater than a photon rocket in vacuum, one would either have to repeat the torsion balance in walls of RF absorber optimized for the frequency in use, so that no reflections can occur… the force might decrease by about a 100 if the photons are immediately absorbed by the environment instead of reflecting a couple of 100 times between environment and DUT

  14. Yeah, so I’ll offer criticisms/suggestions. Honestly, some of these should’ve been mentioned by the reviewers. I’m really surprised they didn’t.

    1) Reverse thrust is consistently *less* (at equivalent power) than forward thrust, well outside of measurement error (33 uN vs 44 uN at 40 W, 64 uN vs 108 uN at 60 W, 71 uN vs. 104 uN at 80 W – measurement error should be between 4-6 uN on the average). This strongly implies an interaction with the chamber or setup apparatus. The fact that the reviewers didn’t have *them* address this is a serious failing on the reviewers’ part. The forward/reverse thrust measurements aren’t even close to consistent – that absolutely should’ve been addressed.

    2) Reading their statement regarding magnetic/electrostatic interactions really kinda suggests it *is* a magnetic interaction. They hard grounded everything to avoid electrostatic charging, but then they claimed they ran power via twisted pair. But twisted pair will only work if there’s no other ground path: if you provide an *alternate* ground path, then at some low frequency (where the extra impedance due to the distance of the signal to the return isn’t large enough to offset the lower resistance), you’ll have some small current flowing.

    Their claim that they ‘kept the power routing the same’ is obviously untrue from the pictures: the amplifier/heat sink is mounted on the back of the test article, which flips direction. So the power wiring can’t be the same. (And this would support the differing forward/reverse thrust measurements, because if a component of the loop current *was* in the same direction, it’d decrease the observed thrust).

    1. Side note, I wonder if anyone has contemplated making this thing inflatable. If it’s in space it could be made out of solar sail like material and inflated in the vacuum. Then you wouldn’t need to worry about the inertial effects of accelerating such a lot of mass. If the thrust was based on the exponent of the volume, then larger would be more energy efficient. A relatively large volume could therefore be packed into a small cheap cubesat.

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