It's a machine that seems to produce a miniscule amount of thrust without a propellant. The laws of physics as we know them require that momentum always be conserved, but this thing seems to move without pushing on anything, which should be completely impossible.
Most likely what's happening here is a thermal effect or the machine pushing off the earth's magnetic field. Keep in mind that these things are very difficult to measure due to the tiny amount of thrust they may or may not produce. According to this study 1.2mN was measured, which is about the same amount of force as gravity exerts on 6-7 grains of rice (according to my back-of-the napkin calculation).
If this were real it would be absolutely huge, and destroy just about all of modern physics. It isn't just that we believe in conservation of momentum because we don't know of any way to break it, the equations we're using to describe things don't work without it.
This paper has a number of flaws. For example, the test really needed to be performed inside of a vaccuum to have any credibility at all, and whether that was the case was not made clear.
TL;DR It's most likely bunk, unfortunately, but it would be very revolutionary if true
The 6-7 grains of rice is an interesting comparison, but they actually they didn't get 1.2mN, they got 1.2mN/kW and they only tested the device with 40W, 60W and 80W and they got http://arc.aiaa.org/action/showPopup?citid=citart1&id=t3&doi... so they only measure a force of ~70uN, that is like 1/25 of a grain of rice, that's probably like a few grains of salt.
And then they use a "aggressive slope-filtering level" method (whatever it means) to get 124uN, that is still very small, like 1/10 of a grain of rice.
The results would be a great deal clearer if they could test it in a high vacuum at 2 to 4 kW. Measuring 3-4 millinewtons reliably is a lot easier to believe than a newton force equivalent to a tiny fraction of 1 grain of rice.
> the test really needed to be performed inside of a vaccuum
If I'm not mistaken they did, and the thrust was almost the same than the one in air. No perfect vacuum here, but still.
"Vacuum conditions are provided by two roughing pumps and two high-speed turbopumps, and all vacuum tests are performed at or below 8×10^−6 torr"
"The vacuum test data collected show a consistent performance of 1.2±0.1 mN/kW, which is very close to the average impulsive performance measured in air (also 1.2 mN/kW)"
According to Roger Shawyer, the inventor of the EmDrive, no physical laws are broken:
>What I would say is that the idea that EmDrive violates the laws of conservation of momentum is itself nonsense. Of course it doesn’t. It wouldn’t work if it did. All that EmDrive is a device for exchanging the momentum of the electromagnetic waves going up and down inside it, with the momentum of the thruster as it accelerates. It’s all actually elementary physics.
The tl;dr is that some scientists investigate some fringe technologies that violate the laws of physics and based on some preliminary studies it looks like there could be something. However it's still vastly more likely that the studies are flawed than that we'll have to rewrite the laws of physics.
I disagree. Even if this actually turns out to be producing thrust due to a reason other than thermal expansion, ablating material, interaction with the Earth's magnetic field, etc., that doesn't mean fundamental laws are wrong. It depends on why it's happening, right? There are...I can't even call them theories...musings that this may simply be an effect which we aren't aware of, but doesn't violate conservation of momentum.
We are so far away from being able to explain why, however, since we first need to determine if this is real and repeatable. I hope that other credible researchers attempt to replicate this.
I had the impression that the laws of physics are seldom rewritten, more of a fix here, another one there. OTOH, one can hardly say that it violates such laws while we don't know how it works.
Not really, because in this case it violates fundamental laws of physics, thereby the probability that the experiment has a source of error unaccounted for is extremely high.
"NASA’s impossible space engine, the EMdrive, passes peer review -- But that doesn’t mean it actually works as advertised."
"What it means to be peer-reviewed is that an independent scientist who is an expert in the particular field read and reviewed the work undertaken, and found it to be of sufficient quality to be a valuable contribution to the field. It does not mean that the results and conclusion of the paper are necessarily correct, or even the last word on that particular issue."
In short, the paper wasn't so amateurish to be rejected -- it "looks" acceptable enough to be published. But it doesn't mean "verified." It doesn't mean that its claims are even repeatable by anybody else but the author of the paper -- and until that happens, it's just the claim of him.
The same astrophysicist who wrote the previous article also specifies the criteria that have to be fulfilled:
- A detection of thrust that scaled with input power: the greater the power, the greater the thrust, in a predictable relationship.
- A thrust that was at least many standard deviations above the measurement error.
- An isolated environment, where atmospheric, gravitational and electromagnetic effects were all removed.
- A reproducible setup and a transparent device design, so that other, independent teams can further test and validate the device/investigate the mechanism.
- And finally, a detailed results report with the submission of an accompanying paper to peer review, and acceptance by the journal in question.
What we’ve got, unfortunately, doesn’t meet most of these criteria at all."
