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posted by martyb on Thursday April 21 2016, @11:29PM   Printer-friendly
from the imagine-the-possibilities dept.

The proposed radio frequency (RF) resonant cavity thruster is unlike conventional thrusters and uses no reaction mass and emits no directional radiation. Designed using principles that are not supported by prevailing scientific theories, it apparently violates the law of conservation of momentum. The EmDrive, has roiled the aerospace world for the several years now, ever since it was proposed by British aerospace engineer Robert Shawyer. The essence of the claim is that by bouncing microwaves in a truncated cone, thrust will be produced out the open end. Most scientists have snorted at the idea, noting correctly that such a thing would violate physical laws. However, prestigious organizations like NASA have replicated the results showing thrusts.

MIT Technology Review has some reasoning on the subject, (possibly pay-walled) with a picture of the device. It's supposedly the so called unruh effect at play. When NASA tested the device, they measured with input of 17 W an average thrust of 91 µN (5.4 µN/W). A Chinese team used 2500 W and measured a thrust of 720 mN (288 µN/W). The expected radiation pressure is closer to 0.003 µN/W.


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  • (Score: 3, Insightful) by mcgrew on Friday April 22 2016, @02:28PM

    by mcgrew (701) <publish@mcgrewbooks.com> on Friday April 22 2016, @02:28PM (#335736) Homepage Journal

    Indeed. I read all 28 volumes of the Encyclopaedia Britannica when I was 12 (1964). Half of what I'd learned was obsolete by the time I was 40.

    A couple of years ago I picked up a fat book at the local library's annual book sale, about writing. The book, 8x10 and an inch and a half thick, had a copyright date of 1973 and every single thing in it was completely obsolete. The first quarter of the book was about typewriter maintenance, carbon paper, SASEs, and the like. Not only has the technology changed, but so has publishing itself. For example, the book said it was hard to get a book of more than 65,000 words published. These days most publishers demand at least 100,000.

    --
    mcgrewbooks.com mcgrew.info nooze.org
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  • (Score: 3, Insightful) by opinionated_science on Friday April 22 2016, @02:42PM

    by opinionated_science (4031) on Friday April 22 2016, @02:42PM (#335747)

    this could be why elderly folks that are not actively researching, get set in their ways? There are some studies that suggest it is loss of neuronal plasticity, but perhaps this can be offset by active learning processes?

    My point about this topic, is that we expect this of science. Bad ideas get entrenched, when small things are not tested.

    The specific point about "astrophysics" (in quotes, hangon!), is that we have physics already. Not sure that scale matters. So then you have this invention of "dark matter", which gets popularised as "mysterious" when it is really unexplained, so far.

    This Emdrive is a magnet for cranks who look for the label unexplained, where they can inset their own dogma, so getting some solid theoretical analysis to support the experiments is reassuring.

    It is disturbing that the dogma in modern science is just as entrenched as it was at the turn of the 20th century - "no new physics to discover"....!