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posted by cmn32480 on Tuesday November 22 2016, @03:21PM   Printer-friendly
from the that-still-doesn't-mean-it-will-work dept.

After months of speculation and leaked documents, NASA's long-awaited EM Drive paper has finally been peer-reviewed and published [open, DOI: 10.2514/1.B36120] [DX]. And it shows that the 'impossible' propulsion system really does appear to work. The NASA Eagleworks Laboratory team even put forward a hypothesis for how the EM Drive could produce thrust – something that seems impossible according to our current understanding of the laws of physics.

In case you've missed the hype, the EM Drive, or Electromagnetic Drive, is a propulsion system first proposed by British inventor Roger Shawyer back in 1999. Instead of using heavy, inefficient rocket fuel, it bounces microwaves back and forth inside a cone-shaped metal cavity to generate thrust. According to Shawyer's calculations, the EM Drive could be so efficient that it could power us to Mars in just 70 days.

takyon: Some have previously dismissed EmDrive as a photon rocket. This is addressed in the paper along with other possible sources of error:

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.

[...] 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 3.33–6.67  μN/kW (or 0.0033–0.0067  mN/kW) range.

Previously: NASA Validates "Impossible" Space Drive's Thrust
"Reactionless" Thruster Tested Again, This Time in a Vacuum
Explanation may be on the way for the "Impossible" EmDrive
Finnish Physicist Says EmDrive Device Does Have an Exhaust
EmDrive Peer-Reviewed Paper Coming in December; Theseus Planning a Cannae Thruster Cubesat


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  • (Score: 3, Informative) by VLM on Tuesday November 22 2016, @04:57PM

    by VLM (445) Subscriber Badge on Tuesday November 22 2016, @04:57PM (#431331)

    "only" be a engineering problem

    There are some basic physics problems to solve such as a given dimension of waveguide can only carry X amount of power which even lowly humans decades ago could generate resulting in flash over inside smaller waveguide sizes. You can pull a hard vacuum (good luck maintaining that) or pump in sulfur hexaflouride or whatever, there's a really heavy decent dielectric gas that might gain you a factor of less than 10 of voltage. Or operate at high pressure, more atoms in the way of the big spark. Going higher freq means lower efficiency RF sources and smaller apparatus that flashes over at lower power. So higher freq is out.

    Meanwhile you can't just cheat and go low in frequency because first of all it gets big and really heavy really fast and the skin effect of conductors means at some power level if you don't cause a spark between voltage maximas you'll be conducting so much RF current in current maximas thru such a thin layer that you'll vaporize some off and obviously nothing conducts between voltage maxima better than air saturated with vaporized copper so things rapidly go downhill fast. Red hot waveguide is a non starter at current technology levels.

    Another second reason you can't cheat and go low is the ole surface area to volume ratio that at a fixed KW per unit volume its harder to cool something big than something small.

    Of course you can abandon single mode operation and run multimode. That is a lot of fun to model and control, like fusion research level of fun and games. But its at least theoretically possible? There is a certain interesting symmetry that fusion power plants try to control and maintain a plasma when pumping a GW thru a giant ass waveguide, while this EM drive thingie would seem to also pump a GW thru a giant ass waveguide while NOT creating or maintaining a plasma discharge. Both are kinda difficult and on bad days at work would likely wish they worked at the opposite facility!

    So in summary unfortunately electrical engineering is advanced enough that we're already operating near-ish basic material limits as understood by the physicists. Its quite easy to arc over a coaxial cable for example, and mankind hasn't invented the materials that a sufficiently lazy engineer or tech can't arc over. I've also melted cables while doing stupid things and yes you can "in theory" replace that low melting temp polyethylene foam or whatever with something like titanium oxide or beryllium oxide but those are a PITA to work with.

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  • (Score: 2) by bradley13 on Tuesday November 22 2016, @06:48PM

    by bradley13 (3053) on Tuesday November 22 2016, @06:48PM (#431404) Homepage Journal

    At the moment - assuming the effect is real - the device is at the stage of using a flame thrower to light a candle: lots of power for very little effect.

    My rough understanding of the device is that the geometry of the chamber is what causes the quantum effects. Assuming that this is the case, it may be possible to refine that geometry to increase the proportion of photons that experience the effect. It may be that no increase in power is required to achieve increased thrust.

    Or this may be cold fusion all over again. There's no way to tell for sure, except through further experiments.

    --
    Everyone is somebody else's weirdo.