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Final NASA Eagleworks Paper Confirms Promising EM Drive Results (hacked.com)
An anonymous reader quotes a report from Hacked: Earlier this month Hacked reported that a draft version of the much expected EmDrive paper by the NASA Eagleworks team, had been leaked. Now, the final version of the paper has been published. The NASA Eagleworks paper, titled "Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum," has been published online as an open access "article in advance" in the American Institute of Aeronautics and Astronautics (AIAA)'s Journal of Propulsion and Power, a prestigious peer-reviewed journal. The paper will appear in the December print issue of the journal. The final version of the paper is very similar to the leaked draft. In particular, the NASA scientists confirm the promising experimental results: "Thrust data from forward, reverse, and null suggested that the system was consistently performing at 1.2 +/- 0.1 mNkW, which was very close to the average impulsive performance measured in air. A number of error sources were considered and discussed." The scientists add that, though the test campaign was not focused on optimizing performance and was more an exercise in existence proof, it is still useful to put the observed thrust-to-power figure of 1.2 mN/kW in context. "[For] missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2 mN/kW performance parameter is over two orders of magnitude higher than other forms of 'zero propellant' propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the 3.33--6.67 uN/kW (or 0.0033--0.0067 mN/kW) range."
In other words, a modest thrust without having to carry fuel can be better, especially for long-distance space missions, than a higher thrust at the cost of having to carry bulky and heavy propellant reserves, and the EmDrive performs much better than the other "zero propellant" propulsion systems studied to date.
What's the usual format of an EM drive? Does it go on a satellite for maintaining orbit instead of a chemical thruster that'll one day run out of fuel? On an interplanetary probe for long-term acceleration, like solar sails might? How big should it be for useful propulsion, and what levels of power does it require -- given that heat dissipation is a perpetual issue for small spacecraft?
They say that they have looked at outgassing, and assumed that its not relevant due to slow temp rise not producing rising force. But that does not cover possibility that the electromagnetic resonances are somehow vaporising and ejecting structure at much higher speeds. At .0012N thrust with 1kW input (and 100% efficiency) a rocket would need exhaust velocity of 1.6e6 m/s and consume around 0.8ng per second - damned difficult to weight with required sensitivity and hard to spot except by looking for evidence in the gases within the chamber as metals will condense out quickly.
I've been following this for a year or so - very interesting. Over at Nasa Space Flight board there are a lot of people making these EM drives in their back yard, with varying results. A lot of this comes from the original work by Roger Shawyer. He has stated that he will show a drone running EM drive in 2017. If that works ...that would change everything. Cheap access to space would mean space-based solar arrays for terrestrial use. Here's an article about his patent.
There's also some very strange results with laser timing through an EM drive cavity. Almost like spacetime is being warped.
... are more or less the same ones than before (= very unclear setup, situation very unlikely to represent the claimed break of the conservation laws, highly restricted conditions not telling much, etc.).
Summary of my impressions after quickly reading this paper:
- The actual methodology generating the thrust isn't clearly explained, 95% of this paper is about the testing conditions (measurements, sources of error, assumptions, etc.). Although I assume that detailed explanations on this front might drive to a level of clarity similar to the one of the tests, as explained in the next point.
- Complex testing setup which is very difficult to be adequately understood from outside. It seems that only people with actual experience under these specific conditions (and, ideally, with physical access to an equivalent setup) are in a position to critically analyse these tests and be specific about the (very likely IMO) source(s) of error.
- Even by ignoring the two aforementioned points, plainly believing that everything is fine and just analysing the results, there are various issues which are somehow against the reliability of this experiment and related out-of-proportion assumptions. Examples in fig. 9: a maximum displacement below 0.005 micrometres (extrapolating such a top performance to interstellar travels is sensible?!); assuming that the error in the measurements remain constant under different conditions (?!); testing just 3 different scenarios (40, 60, 80 W) and getting counter-intuitive results (30/40 = 0.75; 106/60 = 1.76; 76/80 = 0.95; 60 W delivering the best performance?!).
Fig. 19 is even more descriptive by showing a tremendous variability of the measurements; in the best-performing 60 W scenario, they vary from 130 to 45 micronewtons!! With only a few cases being similar enough (85 and 92); out of all the about 20 cases, there are only a few which are identical under the given conditions.
Custom Solvers 2.0 = Alvaro Carballo Garcia = varocarbas.
IAATP working on quantum electrodynamics (QED) and other theories.
The fundamental problem with this experiment is that it appears to violate conservation of momentum. This violation is not something that can be discarded easily: it has been confirmed directly and indirectly in millions of experiments over decades.
Momentum conservation is also a cornerstone of quantum field theory (QFT) and it is a symmetry which survives quantization. The entire Standard Model (SM) is a momentum-conserving QFT. The SM has been confirmed to a high accuracy in particle accelerators for many years. Any violation of momentum conservation would have been quickly noticed. You cannot simply invoke 'quantum mechanics', 'zero point', 'vacuum fluctuations', etc. to explain excess thrust. Momentum conservation is fundamental, both classically and quantum mechanically.
So what about the EM drive results? There is a possibility that some new physics is at play, however it is vastly more likely that there is a systematic error which has not been eliminated. (If I had to guess I would imagine that because a large amount of RF energy is being pumped into large metal cavities, the apparatus is resting at the bottom of a standing wave potential.)
The way to finally confirm or refute this is to take the drive into space. In this case, it is almost certain that the net thrust would be equal to the momentum of the photon flux leaving the drive.
> The actual methodology generating the thrust isn't clearly explained, 95% of this paper is about the testing conditions
Well duh, this paper is about proving existence. It's a physical test, it doesn't have to explain why it works. If the models don't fit reality then it is the models that are wrong, not reality. Hence the details about the test infrastructure. That results don't have to make sense, they just need to show that existing models are invalid.
Just imagine this gizmo powered with cold fusion!
Just to put the numbers in perspective. A force of 1.2mN/kW is equivalent of a force of 0.12 gram.
A Tesla SP85 has a maximum effect of 350KW. This would (in theory) produce a force of roughly 40 grams, the weight of 10 sugar cubes.
A Nuclear submarine is able to produce an effect of 100MW, giving a theoretical force of 10kg.
A medium nuclear power plant is producing roughly 1000MW, and a force of 100kg.
Now, does it work? No idea, frankly. I'm more inclined to believe the results of, you know, an actual test than someone who didn't do the test but insists it can't work in spite of the test....
It's difficult to convey to a non-physicist just how accurately and consistently quantum field theory describes nature. Physicists routinely make calculations which have lower uncertainly than the best experiments. For example the anomalous magnetic moment (https://en.wikipedia.org/wiki/Anomalous_magnetic_dipole_moment) is in agreement with theory to ten significant figures.
Physicists tend to be fairly cautious describing results, but when it comes to basic theory at energies up to a few hundred GeV we are confident that we have *all* physical effects well and truly nailed. This doesn't mean that we can always solve the equations perfectly: quantum mechanics is hard, but the equations themselves are almost beyond reproach.
It's not undeserved hubris: it's trillions of independent experiments, billions of dollars and hundreds of thousands of man-years working on the theory by lots of very smart people. The theory, quantum field theory (QFT), is simple, consistent and universal. It describes everything we can see around us, with the exception of gravity.
If you ask an actual physicist what he or she thinks of the EM drive, they will overwhelmingly say that is is highly likely there is an unresolved source of error because violation of moment conservation has never been observed and is inconsistent with QFT.
Apart from the open process and independently verified results
This is the problem though the results are not at all verified. Have you actually read the paper? It shows an appallingly low level of scientific methodology for a paper claiming to observe a phenomenon which violates the currently know fundamental laws of physics. For example at one point it is quoting a fit to 7 significant figures without giving any uncertainty range which suggests a position accuracy of ~1nm which is less than the size of an atom. I am unconvinced that they measure the position this accurately. While this ultimately will not affect the result they claim it shows sloppy practice which is not a good for inspiring confidence.
However most importantly when considering errors at no point do they see to consider charged particle emission as a source of thrust. They do worry about the components becoming charged which they say they fix by grounding but if you are emitting electrons grounding the engine just ensures that there is no charge build up which will allow the engine to continue to operate. Since you cannot ground a craft in space the charge would build up their until the engine's thrust stops.
So it's great that they publish their results openly but what there is to see there in no way inspires any confidence that they have observed some new, fundamental physics phenomenon. Instead of engineers they need to get some scientists involved because the paper shows a total focus on simply measuring the thrust and zero scientific investigation to investigate the cause of the thrust.