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NASA Space Technology

New Test Supports NASA's Controversial EM Drive 480

An anonymous reader writes: Last year, NASA's advanced propulsion research wing made headlines by announcing the successful test of a physics-defying electromagnetic drive, or EM drive. Now, this futuristic engine, which could in theory propel objects to near-relativistic speeds, has been shown to work inside a space-like vacuum. NASA Eagleworks made the announcement quite unassumingly via NASASpaceFlight.com. The EM drive is controversial in that it appears to violate conventional physics and the law of conservation of momentum; the engine, invented by British scientist Roger Sawyer, converts electric power to thrust without the need for any propellant by bouncing microwaves within a closed container. So, with no expulsion of propellant, there’s nothing to balance the change in the spacecraft’s momentum during acceleration.
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New Test Supports NASA's Controversial EM Drive

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  • by MetricT ( 128876 ) on Friday May 01, 2015 @03:04PM (#49596017)

    I want a non-Newtonian drive as much as any other nerd out there, but it's still more probable that (assuming it works) it uses conventional physics, just in ways they haven't figured out yet.

    That said, I think this result is the point where NASA, DOD, Lockheed Martin, Boeing et al should turn on the money spigot for research. There's obviously something going on, even if it's just conventional physics in unexpected ways. And on the odd chance it *is* new physics, the results could change the world.

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      That said, I think this result is the point where NASA, DOD, Lockheed Martin, Boeing et al should turn on the money spigot for research. There's obviously something going on, even if it's just conventional physics in unexpected ways. And on the odd chance it *is* new physics, the results could change the world.

      The original "result" would never have made it past peer review and the people pushing it knew it. Their experimental methods had a ton of holes in it (as many people pointed out), and they didn't even have a theoretical basis for why it would work really (the supposed explanation based on White's quantum woo got torn apart by theorists). So they never even tried to publish - the most they did was talk about it at a conference.

      This new "result" comes from a post on an internet forum. I'm a bit skeptical

    • by tnk1 ( 899206 )

      Well, we know that conventional physics doesn't cover everything, obviously. I'm pretty skeptical of this myself, but I'm reserving my opinion.

      Virtual particles are definitely not a fringe understanding of the quantum mechanical realm, but they've always been representative of something... well... virtual. They would be generally expected to cancel out at macro scales. The only example I've heard of where they don't is Hawking radiation, and that's only because of the very specific consequences of anythin

    • Before we call this real, we need to put one on some object in orbit, leave it in continuous operation, and use it to raise the orbit by a measurable amount large enough that there would not be argument regarding where it came from. The Space Station would be just fine. It has power for experiments that is probably sufficient and it has a continuing problem of needing to raise its orbit.

      And believe me, if this raises the orbit of the Space Station they aren't going to want to disconnect it after the experim

      • by wiggles ( 30088 )

        Before we put it on the ISS, let's start by putting one on a cheap metal box with some dumb sensors and communication equipment on it. I'd rather test this on something that doesn't have somebody living in it.

  • If nobody knows how it works, how did the guy invent it?
    • Ah of course, as PvtVoid already posted:

      [T]he EM Drive’s thrust was due to the Quantum Vacuum (the quantum state with the lowest possible energy) behaving like propellant ions behave in a MagnetoHydroDynamics drive (a method electrifying propellant and then directing it with magnetic fields to push a spacecraft in the opposite direction) for spacecraft propulsion.

      So the recent test was trying to replicate the results in a vacuum to eliminate some unknown other factor as the explanation.

      • due to the Quantum Vacuum (the quantum state with the lowest possible energy)

        Does the battery look like a melted Tiffany lamp?

    • Re:inventor? (Score:5, Interesting)

      by ScentCone ( 795499 ) on Friday May 01, 2015 @03:21PM (#49596171)

      If nobody knows how it works, how did the guy invent it?

      Just like penicillin.

    • If nobody knows how it works, how did the guy invent it?

      LOTS of stuff gets invented without the inventor knowing HOW it works, underlying physics wise. All that's necessary is to notice THAT it works, work out some details of "if you do this much of this you get that much of that", and engineer a practical gadget.

      As they say, most fundamental discoveries don't go "Eureka!", they go "That's odd ..."

  • There is no law of physics that says physical propellant is necessary. Any light bulb and mirror can create momentum, with no propellant expended. SF writers have known for a long time that, in principle, electromagnetic effects like powerful lasers can create thrust. I need more details to make sense of this article.
    • Any light bulb and mirror can create momentum, with no propellant expended. SF writers have known for a long time that, in principle, electromagnetic effects like powerful lasers can create thrust.

      By expelling photons, which are then acting as a propellant.
      --
      JimFive

    • No, but we do know the momentum of photons having a given energy, and we're talking about a lot more apparent momentum change than can be accounted for by the energy used.

    • Leaving aside the fact that light has momentum and therefore is sufficiently "physical" a propellant for this example, and the fact that this thing produces orders of magnitudes more thrust than a few Watts worth of photons could impart, you're still missing a really key problem:

      You can impart momentum on a mirror by shining a flashlight on it, but you can't impart momentum on a sealed box by having a lit flashlight *inside* it!

      The EmDrive uses a sealed cavity. There's nowhere for any propellant to come out, even if there were any!

  • by DrJimbo ( 594231 ) on Friday May 01, 2015 @03:28PM (#49596237)

    They say one of the limiting factors (aside from violating the laws of physics) is the political will to launch a large nuclear power plant into space. The solution is obvious: use Cold Fusion to power the EM drive. There is great efficiency here because they can get two Nobel prizes with only one gadget.

  • by Anonymous Coward on Friday May 01, 2015 @03:29PM (#49596249)

    A lovely summary from the Physics StackExchange which sums up my thoughts:

    "The initial tests were at atmospheric pressure. To test the fan hypothesis, an easy way is to vary the pressure, another easy way is to put dust in the air to see the air-currents. The experimenters didn't do any of this (or at least didn't publish it if they did), instead, they ran the device inside a vacuum chamber but at ambient pressure after putting it through a vacuum cycle to simulate space. This is not a vacuum test, but it can mislead one on a first read.

    In response to criticism of this faux-vacuum test, they did a second test in a real vacuum. This time, they used a torsion pendulum to find a teeny-tiny thrust of no relation to the first purported thrust. The second run in vacuum has completely different effects, possibly due to interactions between charge building up on the device and metallic components of the torsion pendulum, possibly due to deliberate misreporting by these folks, who didn't bother to explain what was going on in the first experiments they hyped up. Since they didn't bother to do a any systematic analysis of the effect on the first run, to vary air-pressure, look at air flows with dust, whatever, or if they did this they didn't bother to admit their initial error, this is not particularly honest experimental work, and there's not much point in talking about it any more. These folks are simply wasting people's time."

    http://physics.stackexchange.com/questions/23725/is-the-emdrive-or-relativity-drive-possible

    In conclusion, they did a really really bad experiment and got a bad result. Wow!

  • Eddy currents (Score:2, Interesting)

    by Anonymous Coward

    The other thing you get when you generate RF is eddy currents in nearby materials, generating magnetic fields from nearby materials. Nothing to see here, move along...

  • This would be really awesome and exciting if it really worked, but, well, it's apparently challenging models of physics which have withstood a tremendously diverse battery of scientific tests. Smart money is on the measurements being a mistake with the experimental apparatus.

  • by frog_strat ( 852055 ) on Friday May 01, 2015 @03:56PM (#49596491)
    If you learn of an alleged unusual phenomenon, and you have an immediate rigid response, please stay away from science. Go into religion or politics. The only appropriate response is "Hmmm interesting, let's look into this". Human knowledge is always provisional. Careless, absolute, knowledge claims are the currency of religion.
    • There is an old saying that you should keep your mind open, but not so open that your brains leak out.

      When someone claims a violation of very well tested physical laws, AND that violation is not under some new unusual condition, it is very reasonable to be skeptical.

      It this was seen with TeV protons at LHC, or in ultra-strong electric fields, or in strong gravity, or other unusual conditions it would be different. Physicists paid attention to the (later dis-proven) FTL neutrinos from CERN because that exper

  • Seriously in the links provided there was absolutely nothing that made it possible to evaluate the claims.

  • by joe_frisch ( 1366229 ) on Friday May 01, 2015 @10:06PM (#49598565)

    Its not easy to measure 50 micro-newtons of force when you change a power level by 50 watts.

    Currents cause magnetic forces. Things get hot and outgas producing thrust. RF power cables get hot and distort causing a force.

    Think about it. The device weighs something like 5Kilos. That is 50 newtons gravitational force. So a 1 micro-radian tilt will cause a 50 micro-newton force. Walking across the lab floor could cause that amount of deflection. If the chamber is 1 meter across, a 0.1 degree temperature change on one side of the chamber (from a nearby power supply) could cause that much tilt.

    There of course could be force just from photons - but that is a simple and well understood photon drive - known for at least 50 years now - basically a light-sail.

    This is a very difficult experiment to do correctly, and they have not published in enough detail.

    Meanwhile: conservation of momentum has been tested under conditions ranging from ultra-cold gas atoms to 100GeV particle collisions, to orbiting neutron stars. The RF fields they use are very modest. At SLAC we run hundreds of megawatts, not 50 watts. We have superconducting cavities where we easily see the deflection caused by the momentum in the microwave fields - operating at many thousands of times higher power than this experiment - we see nothing unexpected.

    So: Difficult experiment. No unusual physical conditions. Apparent violation of one of the most carefully tested conservation laws in all of science.

    It it literally more likely that the sun will not rise tomorrow (since that is also based on conservation of momentum) than that this experiment was correct.

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