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posted by takyon on Friday May 01 2015, @06:00PM   Printer-friendly
from the newtons-per-kilowatt dept.

An article at is claiming that the superficially reactionless EmDrive has again been tested at NASA Eagleworks, this time in hard vacuum, and the anomalous thrust is still being detected:

A group at NASA's Johnson Space Center has successfully tested an electromagnetic (EM) propulsion drive in a vacuum – a major breakthrough for a multi-year international effort comprising several competing research teams. Thrust measurements of the EM Drive defy classical physics' expectations that such a closed (microwave) cavity should be unusable for space propulsion because of the law of conservation of momentum.

With the popular explanations of thermal convection or atmospheric ionization being ruled out by operation in vacuum, and thrust thousands of times greater than expected from a photon rocket, is it time to start taking the EM Drive seriously as a fundamentally new form of propulsion, and possibly a door to new physics?

Roger Shawyer, the inventor of the EmDrive, claims that the device's efficiency will scale even further with greater levels of power, potentially enabling fast interstellar travel powered by a radioisotope thermoelectric generator or nuclear fission.

Previously: NASA Validates "Impossible" Space Drive's Thrust

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  • (Score: 2) by HiThere on Saturday May 02 2015, @01:54AM

    by HiThere (866) on Saturday May 02 2015, @01:54AM (#177722) Journal

    The thing is that there are certain kinds of "perpetual motion" that happen. What you can't (usually) do is extract energy.

    OTOH, there is a design for a nano-machine that should work as a perpetual motion where you can extract energy (though not much). Basically it's just a ratchet that's small enough that occasionally it will vibrate in a way that winds the ratchet. (But you can't have significant back pressure or it stops working, so you need to use the twist as you generate it.)

    There are lots of "edge cases" that don't fit into the way we normally think about physics. Every once in awhile one of them becomes important enough to require a detailed explanation, and then you get something like quantum theory. (That said, the nano-machine I described doesn't break any actual law of physics, just the way we normally talk about it. When you get small enough thermodynamics stops working because you aren't dealing with a large enough collection of "pieces" to make treating it statistically a valid approach. But quantum uncertain continues to work.)

    And *that* said, we know that the standard model of physics is incomplete. We just don't have a good idea of how to modify or extend it. Perhaps this will give us some clues. (And quite likely, if it proves out it will have limits that will restrict it's usefulness.)

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  • (Score: 3, Informative) by tangomargarine on Sunday May 03 2015, @05:32PM

    by tangomargarine (667) on Sunday May 03 2015, @05:32PM (#178160)

    Yes, it's called a Brownian ratchet [] and, although it took them a long time to do so, scientists finally figured out why it wouldn't work.

    The PM Wiki article is quite in-depth. It's a good read.

    The other "gotcha" they mention is that things that *appear* to be perpetual motion machines (e.g. something that gets its input from tidal energy or radioactive decay) may work for an extremely long amount of time, but they will eventually fail because of entropy (plutonium will eventually be totally decayed in millions of years).

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