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, @04:05PM
Would this type of engine only work in space, or could you also use it on earth (e.g. on an aircraft or (hover)boat)?
(Score: 2) by MrGuy on Tuesday November 22 2016, @04:18PM
Short answer? Yes, but no. You could use it, but it's incredibly inefficient.
The amount of thrust is INCREDIBLY small. The devices being tested have thrust measured around 0.001 Newton per kilowatt of power. That's about enough thrust to life a grain of rice off a table, for a kilowatt of input power. That's many, many, many orders of magnitude less force than you'd get with an electric motor.
The big deal here is that this is force we can get in a vacuum, without propellant. The need to carry (and eventually exhaust the supply of) propellant is one of the hardest problems in rocketry. So the ability to generate thrust without carrying around propellant is a huge advance.
(Score: 2) by VLM on Tuesday November 22 2016, @05:12PM
That's about enough thrust to life a grain of rice off a table
If you could project that force or field, its interesting to consider that a commercial success on the ground might be a force thats un-noticable to anything bigger than a butterfly but covers an area the size of a back yard patio with a force stronger than a mosquito can fly against. Or a force that pisses off mosquitos so they fly away.
You can just use an electric fan like we did when we were kids and those keep the bugs away and on a hot summer night they keep you cool out on the deck/patio probably for less electrical power but a no moving parts gadget might sell to Dyson type customers.
Also you could make a tiny little hole in the thruster's waveguide and provide a couple KW so the kids could roast marshmelons (what maybe 1% of SN is going to get that reference? Thats an old movie now...)
(Score: 2) by MrGuy on Tuesday November 22 2016, @06:02PM
Yeah, but now you're talking about a completely different theoretical device.
One of the things that has people so flummoxed about this device is that it appears to produce thrust with no exhaust. It appears to violate conservation of momentum. So, there's no "force" from the exhaust to use like this.
Even if you did have a useable exhaust force, this method is an incredibly inefficient way to generate it. You're much better off using a physical device like a fan to produce the effects you're describing.
(Score: 2) by VLM on Tuesday November 22 2016, @09:26PM
Yes but it would be really, really cool...
(Score: 0) by Anonymous Coward on Tuesday November 22 2016, @04:24PM
Anywhere you can turn it on. But low thrust means space is likely where it would be useful.
(Score: 3, Funny) by DannyB on Tuesday November 22 2016, @04:31PM
What about practical low thrust applications on Earth, such as keeping ghosts out of your house?
(ducks, hides under desk)
People today are educated enough to repeat what they are taught but not to question what they are taught.
(Score: 0) by Anonymous Coward on Tuesday November 22 2016, @06:51PM
I'm pretty sure the desk doesn't protect you from ghosts.
(Score: 2) by takyon on Tuesday November 22 2016, @04:30PM
The version NASA is testing is comparable to an ion engine capable of making a sheet of paper flutter at best. Roger Shawyer claims that the second generation of emdrive would make a hovering electric vehicle possible:
http://www.ibtimes.co.uk/emdrive-roger-shawyer-paper-describing-space-propulsion-uavs-finally-passes-peer-review-1513223 [ibtimes.co.uk]
http://www.ibtimes.co.uk/emdrive-exclusive-roger-shawyer-confirms-mod-dod-interested-controversial-space-propulsion-tech-1586392 [ibtimes.co.uk]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]