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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: 3, Interesting) by VLM on Tuesday November 22 2016, @04:11PM
If I did my math right (LOL) and if you skip the idea of a rocket engine and go for sound speaker, and you make the construction extremely light, I think the forces would be measurable although inaudible to human ears in a top quality anechoic sound chamber at sane-ish power levels. Feed in an AM modulated signal instead of CW and there you go, the worlds most exotic speaker. So it won't be replacing car subwoofers any time soon, but it should be able to almost generate audible (well, in theory) sound. Quiet sounds don't require much force.
This would explain why no level of casual screwing around in the microwave RF lab results in sounds, not just no movement. Just at the border under ideal conditions of almost making a sound before it melts.
Which is creepy because there's no reason it has to be that close in the physics, why not 1e-24 times too low. That could indicate scam like someone reverse engineered why a microwave RF lab can be silent yet the effect exist then worked backwards. Then again everything new that's discovered has always been just outta the noise level, just at the border of possible.
(Score: 2) by quintessence on Tuesday November 22 2016, @04:59PM
I had read they are making microphone transducers out of graphene. Only a skip and a jump to speakers. Just insane having a near translucent cone that strong.
Anyhoo, the transducer should be able to pickup even the slightest perturbation in the air. Even if not audible, it can be measured.
(Score: 2) by VLM on Tuesday November 22 2016, @05:06PM
Yup there you go. A graphene microphone and a graphene disk with the thruster attached as if a speaker cone. Maybe make the whole thruster out of graphene.
Stuff like slow thermal expansion should average out if you feed an ultrasonic 100 KHZ AM modulation of microwave power into the thruster, and the microphone should just barely be able to hear it.
Now good luck dumping kilowatts to megawatts into one thing and having no capacitance affecting the electronic transducer.. which is where the true brilliance comes in with this design, look at the phase of what you transmit vs what you hear because sound is immensely slower than light (microwave RF) so the signal you're wanting to listen to syncs up after sound travels 5 feet not after light travels 5 feet. You can subtract any signal that syncs up after light travels 5 feet. Heck you could hook up a white noise source to the thruster and correlate sonar style that the microphone heard sound from 5 feet ago, or 5 feet away, however you want to look at that..
(Score: 3, Informative) by JoeMerchant on Tuesday November 22 2016, @07:49PM
All too easy for the power cables to generate audio as the signals they carry modulate... the magic here is thrust without mass, it's not a big deal when you're swimming in mass, sucked down onto a giant ball of mass by its gravity... it becomes a big deal fast when you leave that gravity well.
🌻🌻 [google.com]
(Score: 2) by Scruffy Beard 2 on Wednesday November 23 2016, @06:32AM
You do get coil whine. The coils change shape slightly when you run current though them.