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A NASA paper outlining work that appears to substantiate the EmDrive concept that involves the production of a thrust in a way that violates the laws of physics was leaked last week, and this story tries to figure out what has been learned.
To me, the key is this paragraph:
In essence, the NASA EmDrive in the paper consists of a closed copper cone, the inside of which is being bombarded with microwaves. To test the EmDrive, the researchers powered it with 40, 60, and 80 watts and found that it generated up to 58, 128, and 119 micronewtons of thrust, respectively. Given that this “anomaly” was still observed by White and his colleagues after accounting for error, this suggests that the results of the experiment show an EmDrive is indeed possible.
Based on these results, the researchers estimated that their contraption would be capable of generating approximately 1.2 millinewtons of thrust per kilowatt were they to scale up the power input. To put this in perspective, the Hall thruster—one of the most powerful in development and powered by ejecting plasma—generates about 60 millinewtons of thrust per kilowatt. [emphasis mine]
Interestingly , the article did not comment on how little thrust this EmDrive test produced. This tiny amount, however, to me suggests strongly that what they are measuring is some outside force acting on the drive that they have missed that would invalidate all the theories listed in the article. And even if the thrust drive does prove a new component of fundamental physics, as suggested in the article, the system simply doesn’t appear to produce enough thrust to make it practical.