"All of the books in the world contain no more information than is broadcast as video in a single large American city in a single year. Not all bits have equal value." -Carl Sagan
For every action, there’s an equal and opposite reaction. While Newton may not be the final word in mechanics anymore since the development of relativity and quantum physics, this law -- better known as the conservation of momentum -- has held up from the 17th century through the 21st in every interaction ever observed. Unless, that is, the EMdrive is everything it claims to be.
The surface magnetic field of an active EMdrive, during the NASA test. Image credit: NASA Spaceflight forums, via Chris Bergin.
A propulsion-less device that results in thrust would be revolutionary, regardless of its efficiency. The tests done by NASA Eagleworks on this device have allegedly just passed peer review, meaning these results of a positive thrust with no observed exhaust (of an action with no reaction) are about to be published. But does that mean these results are real, and the laws of physics can now be considered broken? Or does passing peer review mean something else?
Inventor Roger Shawyer with a prototype of his EMdrive. Image credit: Roger Shawyer, Satellite Propulsion Research Ltd.
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I'm looking forward to many others testing it at larger scales. I don't think it'll work as a rocket, but I also don't expect that it's fraud. I'm particularly curious to know if changing the cavity material will impact the effect, as my first guess is all that RF is causing some sort of thermal expansion or vibration, or some other effect related to the device's walls. That's really nothing but a guess though.
The other true test will be scaling it up and seeing if the signal scales with the experiment. If its a real effect, it should. If the effect's size remains constant and just above the limit of detection though, that would be a very strong sign of us 'fooling ourselves.'
If this device were emitting directional EM waves, we would expects "thrust" equal to (but opposite) the energy in the photons. But without playing with units, I suspect this is much lower than the claimed thrust over energy ratio.
One also wonders about induced forces on its surroundings, magnetic fields interacting with conductors and/or magnetic objects can do that.
There's actually a recently published paper that gives a theoretical framework for how the EM Drive could produce thrust without violating Newton's 3rd Law. Not an expert in these matters to evaluate the possibility, but I know enough to know that there's a testable hypothesis here that can be validated or refuted.
http://www.extremetech.com/extreme/227146-a-new-theory-of-inertia-could…
A working device will get science away from their particle accelerators and looking at low energy experiments to find new particles. In this way, engineers usually call the ture for science.
Potential subject matter refecting theory include, negative and positive vacuum energy separation and associated virtual particle generation, the fifth force, and supercharge.
I can think of an experiment that might be able to answer the question.
Every year, we launch satellites into space. Why not take one that's going to be launched and fit it with an EM Drive as a directional thruster? I realise that such an experiment would likely not be cheap, but it would resolve the issue once and for all.
Just to be clear, I'm sceptical too. I'd love this to work but I can't see how it could.
@5: I'm as skeptical as you, but you don't test something at the operating principle + lab prototype stage by moving immediately to satellite launch and then declaring it can't work if it doesn't work the first time. A few independent reproduction tests using first exact duplicates, then scaled-up models varying some of the parameter slightly, is a reasonable next step (IMO).
Besides which, 1 Newton per megawatt means its unlikely to lift anything into orbit any time soon. AFAIK the most compact way to produce megawatt-level electricity is probably with a military naval nuclear reactor. This page notes that the most recent (i.e. advanced) generation of sub reactor, the S6G, produces 176 MWth (MW thermal; which translates into about between a third and a half of that electric) and weighs 1,680 tons. Plugging all that in and using 0.4 as a SWAG for the thermal-to-electric efficiency, I get that this technology could push its own motor - but nothing else, no cargo - at a rate of 0.05 mm per second. Thus this launch vehicle could reach LEO in...3.1E9 seconds. Which is about 100 years. So no, it's not going to lift any satellite into orbit, even if it works. At least not any time soon. :) OTOH, if it did work, this might be fine for an interstellar satellite, because that miniscule level of constant thrust is probably still a heck of a lot better over very very long distances than anything we can achieve with chemical rockets.
@Julian Frost more info on EMdrive
The title is: "Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum"
"Thrust data in mode shape TM212 at less than 8*10^6 Torr environment, from forward, reverse and null tests suggests that the system is consistently performing with a thrust to power ratio of 1.2 +/- 0.1 mN/Kw (*)"
http://cannae.com/press-release-from-cannae/
Another EMdrive provider
[quote]AUGUST 17, 2016
PRESS RELEASE FROM CANNAE
Cannae Inc. is demonstrating its proprietary thruster technology on an upcoming satellite mission. Cannae’s technology requires no on-board propellant to generate thrust and will provide station-keeping for a cubesat flying below a 150 mile orbital altitude. The demonstration satellite will remain in this orbit for a minimum of six months.
Cannae formed Theseus Space Inc. to work with its commercial partners to execute the technology demonstration mission. LAI International of Tempe. AZ continues to provide manufacturing and project support. SpaceQuest Ltd. of Fairfax, VA is providing system integration, technical support and program management for the satellite mission.
Please visit our website www.cannae.com for more information[/quote]
seriously.. this again?
@Sinisa Lazarek #8
Don't scoff. This could totally work if only they'd pair the EMdrive with a LENR eCat. We might be able to use that combo for interstellar travel as both technologies have proven, at least on the interwebs, to go on and on and on and on. ...And when you think one or the other had died, it roars back to life and goes on and on some more.
eric @6, hence my comment about using it as a directional thruster, not a lifting engine.
#7:
What energy source are you using? Even if you're not using propellant, you need something to provide energy.
It has been confirmed by the AIAA that a paper on the EmDrive is being published in December 2016. They said:
“The American Institute of Aeronautics and Astronautics (AIAA) Journal of Propulsion and Power has accepted for publication a paper in the area of electromagnetic propulsion. However, it is AIAA’s policy not to discuss the details of peer reviewed papers before/until they are published. We currently expect the paper in question to be published in December 2016.”
Both Michio Kaku and Kip Thorne think it can be done, but you need rotating black holes with ring singularities, which evacuate gravity from the center, thus creating an "eye"- then you'll have a traversable wormhole. Can't call anything "impossible" when our science is so primitive.
I prefer Max Planck to Albert Einstein myself. Einstein was wrong about quantum mechanics. Planck said that a new scientific theory only gains traction when the old generation dies off and a new generation grows up that is familiar with it.
@Alex Reynolds
There is a principle in physics call duality where two completely dissimilar processes follow the same physical laws and math. Quasiparticles are and example of dual nature of systems.
A dual of the black hole is the Bose condinsate. The condensate follows the behavior of the black hole in that it is non energy radiating except for hawking radiation.
See
http://phys.org/news/2016-08-physicist-quantum-effects-hawking-lab.html
Abstract
We observe spontaneous Hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole in an atomic Bose–Einstein condensate. Correlations are observed between the Hawking particles outside the black hole and the partner particles inside. These correlations indicate an approximately thermal distribution of Hawking radiation. We find that the high-energy pairs are entangled, while the low-energy pairs are not, within the reasonable assumption that excitations with different frequencies are not correlated. The entanglement verifies the quantum nature of the Hawking radiation. The results are consistent with a driven oscillation experiment and a numerical simulation.
Read more at: http://phys.org/news/2016-08-physicist-quantum-effects-hawking-lab.html…
Ethan should post on this.
Eric @ 1 makes sense and should be doable: scale up the device and see if or how the effect scales. Straightforward experiment that should produce clear measurements. Also Julian @ 5 once we've got something that can be sent up as a payload.
This is starting to look less like measurement error and more like some kind of real effect, though it may still turn out to be less than useful. OTOH look at the history of any technology: early examples were crude, theory & practical experiments produced better ones, etc.
Launching robotic interstellar probes powered by fission reactors seems like a not-good idea. I'm all in favor of fission for clean energy on Earth, but the risk of a long-dead but still radioactive device floating around until it finds a planet to crash into, strikes me as the kind of thing that would have the Vulcans suing us for negligence;-)
I find it absolutely amazing that no one seems to have watched the programme where roger sawyer clealy states that his invention does not contravene Newton's third law but functions within its parameters. He didn't specify the details because quite rightly he wants to tie down the patent before the Americans or Chinese steal it from him. And the Italians are due to launch a demonstration of the engine within 6 to 8 months so clealrly its well past the peer review stage
A spherical warm black body will radiate infrared photons uniformly in all directions.
But what if you have a black body shaped like a mirrored resonant cavity with a "rear window" on one end (like a cylindrical laser) where the photons escape in a beam out the rear "exhaust port"?
Since photons have momentum, p = h / λ, where the momentum of a photon, p, measured in kilogram-meters per second, is equal to Planck's constant, h, divided by the de Broglie wavelength of the light, λ, measured in meters, the "equal and opposite reaction" is to push the mirrored resonant cavity in the opposite direction from the "exhaust beam" of infrared photons.
Does this not preserve Newton's Conservation of Momentum in the same way as a pure photon "solar sail" where the only thing impinging on the solar sail are photons from the sun?
The image showing magnetic field intensity shows it to have peak strength on the wide circular end of the EMDrive. Therefore, the microwaves impinging there would heat up that end much more than the other end, resulting in re-radiation in the form of infrared waves on the outside of the metal endplates. Perhaps this differential in infrared radiation between the two ends of the cavity is the source of the tiny thrust reported by NASA.
Hmmm, megawatts in for fNewtons out ...... ??
"Does this not preserve Newton’s Conservation of Momentum in the same way as a pure photon “solar sail” where the only thing impinging on the solar sail are photons from the sun?"
Yes, Barry, it does.
This drive isn't doing that, because they've attempted to determine if it's just photon anisotropy. Apparently they have ruled that out.
"He didn’t specify the details because quite rightly he wants to tie down the patent before the Americans or Chinese steal it from him."
Uhm, he'd still get the patent. Unless someone is within a year of providing their OWN patent on this (in which case it can hardly be called obvious or even "his" patent, see Newton/Leibniz on differentiation), they'd still be going.
Proclaiming this patent scare is a sure fire indicator of someone scamming.
IOW even if it works, they haven't a damn clue why and are just hoping like hell nobody notices this could be wrong.