An article at NasaSpaceFlight.com 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
From testing, it appears that they may have thought of this:
The following independent tests have been performed for the EmDrive.
A test at 2500 W of power during which a thrust of 750 millinewtons was measured by a Chinese team at the Chinese Northwestern Polytechnical University.
A test at 50 W of power during which a thrust of 50 micronewtons was measured by Eagleworks at the Johnson Space Center at ~760 Torr of pressure. (Summer 2014)
A test at 50 W of power during which a thrust of 50 micronewtons was measured by Eagleworks at the Johnson Space Center at ~5.0×10−6 torr or pressure. (Early 2015)
A test at 50 W of power during which an interferometer (a modified Michelson device) was used to measure the stretching and compressing of spacetime within the device, which produced initial results that were consistent with an Alcubierre drive fluctuation.
All these tests were conducted with a control device that did not produce thrust.
NOTE: a better source was found for the Chinese results, and I have changed this section to reflect that.
Test #1 was conducted at the direction of lead researcher Juan Yang. She tested the device at several power levels and frequencies using the same equipment used to test Ion Drives. The given result above was the largest result produced. Her team estimated that the total measurement error was less than 12%. Source 1 | Source 2
Tests number 2 and 3 were performed multiple times, changing direction of the device and observing a corresponding change in the direction of force. They were not especially careful about controlling for ALL variables however, mostly owing to the lack of funding for the project. The positive tests have resulted in more funding becoming available, although it is still very, very little, and possibly not enough to explain where the error occurred if the measurement is error of some kind.
Test #4 was performed, essentially, on a whim by the research team as they were bouncing ideas off each other, and was entirely unexpected. They are extremely hesitant to draw any conclusions based on test #4, although they certainly found it interesting.
The Eagleworks team has been able to dedicate very little hardware towards this experiment, as there has been almost no dedicated funding for this experiment. The lack of funding is related to how outlandish the claims are to those who understand physics very well, and the lack of adequate explanation on the math behind the devices from the inventors.
Forgot to add the link to the source: https://www.reddit.com/r/Futurology/comments/34cq1b/the_facts_as_we_currently_know_them_about_the/ [reddit.com]
results that were consistent with an Alcubierre drive fluctuation
Wish I could find the original source for that and verify that it's from the experiments and not just something that has got added by the internet.
If true, then I guess it neatly provides a theoretical way for this to work without propellant, and um, wow. Alcubierre has always been interesting mathematically but impossible practically due to requiring things like negative mass. If it turns out all we've got to do is bounce some microwaves around in a tin can to get a warp field then, f**k. Off to sell all my shares in dilithium crystal prospectors...