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Full Version: The Emthruster: Thrust without reaction?
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I just came upon this paper, which describes an eight-day experiment at the Johnson Space Center on a device that uses microwaves in a resonant cavity to generate (a very small) thrust without propellants. If this report is taken at face value (apparently, the experiment had previously been conducted in China; see attached PDF), this could lead (after much improvement, of course) to a reaction-less drive. Articles describing the experiment are available here and here.

Yes, I'm watching this with interest too. Most commentators think it is another experimental error. like the FTL neutrinos; but some think it could be the start of something big.
IF (and that's a big if) this turns out to be as advertised, then it could be developed into a modo version of a reactionless drive, one that doesn't need void bubbles or the like. Hopefully, that will prove to be the case (the existence of the two independent papers cited in the OP help, IMO, to strengthen the case somewhat).

I don't see how this is suppose to be a reactionless drive.

(If it generates and puts out microwaves isn't it a photon drive in the microwave freqency? I understood it was propellent-less using light momentum like solar sails do, after all the EM spectrum includes visibile light,microwave and RF) Given that it gives out 50 millinewtons or whatever compaerd to the 200 odd of a ion drive I guess it would have a diffrent regime than big thrust drives much like ion.
Perhaps it is not a "true" reactionless drive, since it seems to act on the quantum vacuum (I think). However, the engine is a sealed unit with no exhaust ports, unlike an ion thruster. Nor is it reacting to external forces, as does a lightsail or a magsail. Since its thrust is created and exerted within the device itself, rather than through interactions with the surrounding medium, I think it might qualify as a reaction-less drive for all practical purposes. [NOTE: The above statements assume the emthruster actually performs as advertised Smile]

My bet is on experimental error. However if the experiment is replicated by another independent institution we might be onto something.
(08-03-2014, 07:40 PM)Dalex Wrote: [ -> ]My bet is on experimental error. However if the experiment is replicated by another independent institution we might be onto something.
The Chinese paper cites the results of Mr. Shawyer's (the inventor) tests conducted in Britain, while the NASA report (which does not acknowledge any prior efforts) describes a test of the same type of apparatus. This implies, to me at least, that Shawyer's claimed results have been replicated by researchers from both China and the United States.

Certainly something we should keep an eye on. Even if this is only a very weak thruster, it might have application for either small craft, stationkeeping on satellites or stations, and low accel, long duration missions, either long term probes or something to replace the drive sail.

That's a very good point. The term "reactionless drive" is often used to mean a drive that doesn't need any physical propellant; typically, this would involve a source of very large amounts of power which is converted into some variety of photons. Which, for many purposes, would be just as useful as a true reactionless drive.

Of course, a photon drive leads to the availability of the Kzinti Lesson...
My money is on experimental error given that they report that their negative control also produced thrust:

Quote:Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article)

Original conference paper here:
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