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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: 2) by bitstream on Friday April 22 2016, @09:07AM

    by bitstream (6144) on Friday April 22 2016, @09:07AM (#335636) Journal

    MIT Technology review:

    McCulloch’s idea is that inertia arises from an effect predicted by general relativity called Unruh radiation. This is the notion that an accelerating object experiences black body radiation. In other words, the universe warms up when you accelerate. /../ inertia is simply the pressure the Unruh radiation exerts on an accelerating body.

    Does that possibly implicate that inertia possibly changes on a small scale with time?

    The idea is that if photons have an inertial mass, they must experience inertia when they reflect. But the Unruh radiation in this case is tiny. So small in fact that it can interact with its immediate environment.

    If the sent particles are even smaller than photons, then the thrust becomes larger? or just thrust internally?

    If there's no exhaust velocity in the traditional sense. What maximum speed can it achieve? The ion engine can manage circa 0.1c. (Hopefully NASA or SpaceX will test the EmDrive in space..)

    Are there any interesting implications that this new theory and experiment predicts?

    DOI 10.1209/0295-5075/111/60005 - Testing quantised inertia on the emdrive [arxiv.org]

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