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
This story from a Wired article: NASA is a major player in space science, so when a team from the agency this week presents evidence that "impossible" microwave thrusters seem to work, something strange is definitely going on. Either the results are completely wrong, or Nasa has confirmed a major breakthrough in space propulsion.
British scientist Roger Shawyer has been trying to interest people in his EmDrive for some years through his company SPR Ltd. Shawyer claims the EmDrive converts electric power into thrust, without the need for any propellant by bouncing microwaves around in a closed container. He has built a number of demonstration systems, but critics reject his relativity-based theory and insist that, according to the law of conservation of momentum, it cannot work.
NASA states... "Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma"
An article at NasaSpaceFlight.com is claiming that the superficially reactionless EmDrive has again been tested at NASA Eagleworks, this time in hard vacuum, and the anomalous thrust is still being detected:
A group at NASA's Johnson Space Center has successfully tested an electromagnetic (EM) propulsion drive in a vacuum – a major breakthrough for a multi-year international effort comprising several competing research teams. Thrust measurements of the EM Drive defy classical physics' expectations that such a closed (microwave) cavity should be unusable for space propulsion because of the law of conservation of momentum.
With the popular explanations of thermal convection or atmospheric ionization being ruled out by operation in vacuum, and thrust thousands of times greater than expected from a photon rocket, is it time to start taking the EM Drive seriously as a fundamentally new form of propulsion, and possibly a door to new physics?
The proposed radio frequency (RF) resonant cavity thruster is unlike conventional thrusters and uses no reaction mass and emits no directional radiation. Designed using principles that are not supported by prevailing scientific theories, it apparently violates the law of conservation of momentum. The EmDrive, has roiled the aerospace world for the several years now, ever since it was proposed by British aerospace engineer Robert Shawyer. The essence of the claim is that by bouncing microwaves in a truncated cone, thrust will be produced out the open end. Most scientists have snorted at the idea, noting correctly that such a thing would violate physical laws. However, prestigious organizations like NASA have replicated the results showing thrusts.
MIT Technology Review has some reasoning on the subject, (possibly pay-walled) with a picture of the device. It's supposedly the so called unruh effect at play. When NASA tested the device, they measured with input of 17 W an average thrust of 91 µN (5.4 µN/W). A Chinese team used 2500 W and measured a thrust of 720 mN (288 µN/W). The expected radiation pressure is closer to 0.003 µN/W.
A new peer-reviewed paper (open, DOI: 10.1063/1.4953807) on the EmDrive from Finland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting into photons that leak out of the closed cavity, producing an exhaust.
So how could something come out that you can't detect? Well, the photons bounce back and forth inside the metal cavity, and some of them end up going together in the same direction with the same speed, but they are 180 degrees out of phase. Invariably, when travelling together in this out-of-phase configuration, they cancel each other's electromagnetic field out completely.
That's the same as water waves travelling together so that the crest of one wave is exactly at the trough of the other and cancelling each other out. The water does not go away, it's still there, in the same way the pairs of photons are still there and carrying momentum even though you can't see them as light.
If you don't have electromagnetic properties on the waves as they have cancelled each other out, then they don't reflect from the cavity walls anymore. Instead they leak out of the cavity. So we have an exhaust – the photons are leaking out pair-wise.
Multiple sources have reported that a paper about EmDrive has cleared peer review and will be published in December, although there is no certainty yet about whether NASA scientists have found evidence to support thrust apparently in violation of the law of conservation of momentum (and not within experimental error):
Long thought to be nothing more than a space dream, the EmDrive, a rocket propulsion technology that requires no propellant, has cleared peer review, the International Business Times reports. The new engine, first proposed 17 years ago, relies on microwaves for its thrust, which are fired into a metal cone, causing acceleration. The latest design, which will be published in the Journal of Propulsion, was the brainchild of scientists at NASA's experimental lab, Eagleworks Laboratories.
Also at Inverse.
Meanwhile, a company formed by Cannae Inc. has announced that it will launch a similar propulsion device into space to prove that it works:
On August 17, Cannae announced plans to launch its thruster on a 6U cubesat. Each unit is a 10-centimeter cube, so a 6U satellite is the size of a small shoebox. Approximately one quarter of this will be taken up by the drive. Fetta intends the satellite to stay on station for at least six months, rather than the six weeks that would be typical for a satellite this size at a altitude of 150 miles. The longer it stays in orbit, the more the satellite will show that it must be producing thrust without propellant.
Cannae has formed a company called Theseus with industrial partners LAI International of Tempe, AZ and SpaceQuest Ltd. of Fairfax, VA to launch the satellite. No launch date has yet been announced, but 2017 seems likely. "Once demonstrated on orbit, Theseus will offer our thruster platforms to the satellite marketplace," says the optimistic conclusion on their website.
The man behind the disputed thruster technology EmDrive has published a presentation detailing the third generation of the device. Roger Shawyer envisions EmDrive 3.0 enabling personal flying vehicles and a "space elevator without cables":
[Although] the second generation of the EmDrive can theoretically produce 3 tonnes of thrust for 1 kilowatt of power, it isn't able to move very far, so it is only useful for marine applications or for diverting asteroids, like in the new CBS sci-fi TV drama Salvation.
Shawyer has long said that his aim for inventing the EmDrive was to help get satellites into space cheaply, to enable more applications and new ways for the human race to combat global warming and the energy crisis. Essentially, the EmDrive needs to be able to move and work as well as a conventional rocket, in order to be a viable solution.
To negate these shortfalls, Shawyer's firm Satellite Propulsion Research Ltd (SPR) has also been researching a third generation of the EmDrive, which solved the acceleration problem by reducing the specific thrust.
So instead of getting 3 tonnes of thrust for every kilowatt, substantially less thrust is produced – but it can be used to accelerate the device (more about this theory can be read in a paper Shawyer presented in Beijing in 2013).
Speaking of that TV show, Roger would like some credit please.
Previously: Finnish Physicist Says EmDrive Device Does Have an Exhaust
It's Official: NASA's Peer-Reviewed EmDrive Paper Has Finally Been Published
Space Race 2.0: China May Already be Testing an EmDrive in Orbit
Physicist Uses "Quantised Inertia" to Explain Both EmDrive and Galaxy Rotation
[Researchers] in China have announced that they've already been testing the controversial drive in low-Earth orbit, and they're looking into using the EM Drive to power their satellites as soon as possible.
Big disclaimer here - all we have to go on right now is a press conference announcement [archive.is] and an article from a government-sponsored Chinese newspaper (and the country doesn't have the best track record when it comes to trustworthy research).
[...] But what the China Academy of Space Technology (CAST) team is saying also corresponds with information provided to IB Times from an anonymous source. According to their informant, China already has an EM Drive on board its version of the International Space Station, the space laboratory Tiangong-2.