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from the that-still-doesn't-mean-it-will-work dept.
After months of speculation and leaked documents, NASA's long-awaited EM Drive paper has finally been peer-reviewed and published [open, DOI: 10.2514/1.B36120] [DX]. And it shows that the 'impossible' propulsion system really does appear to work. The NASA Eagleworks Laboratory team even put forward a hypothesis for how the EM Drive could produce thrust – something that seems impossible according to our current understanding of the laws of physics.
In case you've missed the hype, the EM Drive, or Electromagnetic Drive, is a propulsion system first proposed by British inventor Roger Shawyer back in 1999. Instead of using heavy, inefficient rocket fuel, it bounces microwaves back and forth inside a cone-shaped metal cavity to generate thrust. According to Shawyer's calculations, the EM Drive could be so efficient that it could power us to Mars in just 70 days.
takyon: Some have previously dismissed EmDrive as a photon rocket. This is addressed in the paper along with other possible sources of error:
The eighth [error:] photon rocket force, RF leakage from test article generating a net force due to photon emission. The performance of a photon rocket is several orders of magnitude lower than the observed thrust. Further, as noted in the above discussion on RF interaction, all leaking fields are managed closely to result in a high quality RF resonance system. This is not a viable source of the observed thrust.
[...] 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 μN/kW (or 0.0033–0.0067 mN/kW) range.
Previously: NASA Validates "Impossible" Space Drive's Thrust
"Reactionless" Thruster Tested Again, This Time in a Vacuum
Explanation may be on the way for the "Impossible" EmDrive
Finnish Physicist Says EmDrive Device Does Have an Exhaust
EmDrive Peer-Reviewed Paper Coming in December; Theseus Planning a Cannae Thruster Cubesat
(Score: 0) by Anonymous Coward on Tuesday November 22 2016, @05:19PM
Color me underwhelmed. For starters, I'm not going to run out and open my wallet based upon their Figure 19. The best possible outcome, in my mind, for these guys, is that this attracts enough attention for it to be tested by people who know what they're doing. This paper still keeps it at the cold fusion level and I'm sure, just like with cold fusion, there could develop a whole slew of garage labs (both literally, as well as the "using borrowed equipment and doing it on my own time at night at a research institution" like "Eagleworks") that pop up "confirmed" or "suggestive" results that will linger for decades.
(Score: 3, Interesting) by bd on Wednesday November 23 2016, @01:53AM
Fig. 19 is not that bad, considering they have a good explanation for it. They had thermal issues (the cavity changing shape and size)
due to the heat sources in a vacuum and those get worse when they increase power. They really should have motorized their three-stub
tuner, so that they could match the cavity to 50 Ohms while operating. Would have been like 100 $ of hardware if they bought expensive
stuff. Strange that they worked with such a shoe-string budget. They could have gotten higher power amplifiers for 50 bucks on ebay
if they were lucky... Beats me, I spend more money on my hobbies.
Or they could have, like, asked someone with serious power microwave stuff for a few hours of playtime. Guess it would be easyer to
measure the effect at 80 KW feed power as opposed to 80 W...
What really makes me sceptical though, is why this is not observed at optical frequencies.
For example, mode-locked disk lasers routinely have several orders of magnitude more energy in their cavities than this glorified
80 W microwave oven. Like, Gigawatt pulse powers and tens of kilowatts average. And beam diameter varies at the end mirrors,
just like the tapered waveguide expands.
Why do pulsed lasers then not disturb other experiments on the optical table, such as interferometric experiments?
(Score: -1, Troll) by Anonymous Coward on Wednesday November 23 2016, @02:03AM
"Color me underwhelmed. For starters, I'm not going to run out and open my wallet based upon their Figure 19. The "
No one's asking you to, cunt.