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.
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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, Insightful) by isostatic on Friday April 22 2016, @12:05AM
At very small accelerations, the wavelengths become so large they can no longer fit in the observable universe
Awesome.
The summary states
McCulloch’s theory could help to change that, although it is hardly a mainstream idea. It makes two challenging assumptions. The first is that photons have inertial mass. The second is that the speed of light must change within the cavity. That won’t be easy for many theorists to stomach.
But correctly leaves us with the question
If not McCulloch’s explanation, then what?
I love it when practical experiments prove theoretical physicists don't have all the answers, and this doesn't seem dirty-cable speed-of-light related. But the xkcd 955 usually applies.
(Score: 0) by Anonymous Coward on Friday April 22 2016, @12:57AM
Listen, dumbass, they wouldn't have their jobs if they actually had all the answers, would they?
(Score: 3, Informative) by Runaway1956 on Friday April 22 2016, @01:35AM
GP's attitude toward theorists is on target. There are a lot of very smart people out there, who THINK that they are much smarter than they are. Although you're right, some of those smart people forget that they don't know it all.
NASA couldn't figure out why the Voyager craft were so far out into deep space. According to calculations, they are a little bit further away from the sun than they should be. They finally settled on the "solar wind". If photons had no mass, then it would be very hard to explain how a spacecraft was going faster than it should be.
http://www.space.com/17456-voyager-1-spacecraft-solar-system-edge.html [space.com]
(Score: 1, Funny) by Anonymous Coward on Friday April 22 2016, @01:42AM
> smart people forget that they don't know it all.
I know. It's called the Dunning–Kruger effect.
(Score: 2) by Bobs on Friday April 22 2016, @02:07AM
> smart people forget that they don't know it all.
I know. It's called the Dunning–Kruger effect.
Well, maybe you know but not all of us so-called smart people do.
(Score: 0) by Anonymous Coward on Friday April 22 2016, @10:23PM
I don't get the Dunning-Kruger effect. It seems like if you invoke it on someone then it is you who thinks they know more than they do. So it is self defeating.
(Score: 4, Interesting) by Absolutely.Geek on Friday April 22 2016, @02:08AM
Agreed but as the saying goes "extraordinary claims require extraordinary evidence"
Basically this is going against some fairly well established physics; so whilst it seems like conservation of momentum is being violated; I bet it is not. I bet we will find something that explains the findings and knowledge will have illuminated a little more of the darkness.
This could be one of the most significant discoveries of this century if it is shown to be accurate; producing thrust from seemingly nothing will allow much greater freedom in exploring the solar system / universe.
Just think a 1200 or so of those cones on the back of a large space craft = approx 1g of acceleration for an energy input of around 3MW.
Don't trust the police or the government - Shihad: My mind's sedate.
(Score: 2) by bitstream on Friday April 22 2016, @07:57AM
3 MWe far out in space means either dangerous fuel or fusion reactor (He3?) that don't work yet. So neat concept but not feasible. But orbiting between the asteroid belt and the sun, probably works. And unlike that ion drive, no refueling should be needed.
But if we get any Polywell reactor or similar to work.. then... Here we come! ;)
I wonder how fast Mars can be reached with these things pushing constantly?
(Score: 3, Insightful) by jcross on Friday April 22 2016, @03:30PM
I'ts also possible that the design under test is way less efficient than it could be. Perhaps if we understood why it worked, we could get more thrust for the power. The car analogy would be seeing a Newcomen engine (https://en.wikipedia.org/wiki/Newcomen_atmospheric_engine) and saying there's no way that's efficient enough to power the horseless carriages of the future, you'd need a massive and dangerous boiler, etc.
(Score: 0) by Anonymous Coward on Saturday April 23 2016, @12:40AM
"Agreed but as the saying goes "extraordinary claims require extraordinary evidence""
That saying, popular as it is, is false.
The problem with this statement is that science does not require extraordinary evidence for its extraordinary claims. Big Bang theory may be the most extraordinary claim in the history of science. Here we have an idea that can be neatly encapsulated in eight words: "At first, there was nothing...then it exploded." But how can NOTHING explode? Big Bang theory "defies gravity" and violates innumerable laws of physics, it remains a HYPOTHETICAL mathematical model, yet it is promoted as truth by NASA and institutions of higher learning around the world.
(Score: 2) by opinionated_science on Friday April 22 2016, @02:17AM
I must confess, that after reading Prof. McC's papers and checking the maths, I was somewhat surprised by the spacecraft stuff.
Then I remembered that a few months back I was telling an elder colleague how much of what he learned at school was wrong.
"Like what?". Says the prof. I picked the easy one - size of the universe. There's plenty in physics, maths , biology etc...
What gives Prof. McC's approach the *most* credibility, is the lack of parameters to fit the data. If you see the pile of approximations used to avoid quantum physics, you'll know what I mean.
We need more experiments to make sure there's no cracks - maybe in space now that's getting cheaper.... A good time to be alive, no?
(Score: 3, Insightful) by mcgrew on Friday April 22 2016, @02:28PM
Indeed. I read all 28 volumes of the Encyclopaedia Britannica when I was 12 (1964). Half of what I'd learned was obsolete by the time I was 40.
A couple of years ago I picked up a fat book at the local library's annual book sale, about writing. The book, 8x10 and an inch and a half thick, had a copyright date of 1973 and every single thing in it was completely obsolete. The first quarter of the book was about typewriter maintenance, carbon paper, SASEs, and the like. Not only has the technology changed, but so has publishing itself. For example, the book said it was hard to get a book of more than 65,000 words published. These days most publishers demand at least 100,000.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 3, Insightful) by opinionated_science on Friday April 22 2016, @02:42PM
this could be why elderly folks that are not actively researching, get set in their ways? There are some studies that suggest it is loss of neuronal plasticity, but perhaps this can be offset by active learning processes?
My point about this topic, is that we expect this of science. Bad ideas get entrenched, when small things are not tested.
The specific point about "astrophysics" (in quotes, hangon!), is that we have physics already. Not sure that scale matters. So then you have this invention of "dark matter", which gets popularised as "mysterious" when it is really unexplained, so far.
This Emdrive is a magnet for cranks who look for the label unexplained, where they can inset their own dogma, so getting some solid theoretical analysis to support the experiments is reassuring.
It is disturbing that the dogma in modern science is just as entrenched as it was at the turn of the 20th century - "no new physics to discover"....!
(Score: 2) by bitstream on Friday April 22 2016, @08:42PM
It's called human nature. Most humans fall for it.
(Score: 2) by maxwell demon on Friday April 22 2016, @05:31AM
I don't see a direct connection here.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 3, Insightful) by Hairyfeet on Friday April 22 2016, @05:38AM
“The Universe is under no obligation to make sense to you.” Neil deGrasse Tyson
ACs are never seen so don't bother. Always ready to show SJWs for the racists they are.
(Score: 2) by bitstream on Friday April 22 2016, @08:40PM
I will immediately sue the Universe for not explaining itself. Won't it respect diversity?? :-)
(Score: 2) by q.kontinuum on Friday April 22 2016, @05:13AM
Nice comment, but since I (currently) read on a (not that)smart-phone I'd really appreciate links as reference to the xkcd 955 [xkcd.com] instead of typing on this pesky little display...
Registered IRC nick on chat.soylentnews.org: qkontinuum
(Score: 2) by isostatic on Friday April 22 2016, @07:32AM
Well I wrote the post on a phone and doing html is a pain.
When it comes to xkcd I assume people have a photographic memory and don't need a link :D
(Score: 2) by Gravis on Friday April 22 2016, @12:32AM
when are they going to put one of these things on something like a satellite and see if it really works?
(Score: 2) by Gaaark on Friday April 22 2016, @12:49AM
Their last update: July 2015... maybe they're already gone!
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 4, Insightful) by takyon on Friday April 22 2016, @03:55AM
I don't see why they need to (I see this argument made on almost every emdrive story). If they figure out how to reliably build the thing, and they scale up the power to meet or exceed the N/W that the Chinese team or Sawyer himself claim it can reach, then it will be quite obvious that the thing works. There is no such problem with ion drives where they aren't even sure that the thing is producing thrust.
Let them thrust first, then they can stick it to a satellite.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0, Interesting) by Anonymous Coward on Friday April 22 2016, @01:11AM
Perhaps this EM charged body is interacting magnetic field of the planet and demonstrating a small degree of electromotive force.
The MIT link: McCulloch says there is observational evidence for this in the form of the famous fly by anomalies. These are the strange jumps in momentum observed in some spacecraft as they fly past Earth toward other planets. That’s exactly what his theory predicts.
Interaction with planetary magnetic fields is also a MUCH simpler explanation for fly-by anomalies (which only happen near a planet, in its magnetic field)...
Whatever happened to rationality in science? Do they not teach that one should at least ATTEMPT to disprove the null hypothesis via disproving the alternate hypotheses anymore?
(Score: 2) by wonkey_monkey on Friday April 22 2016, @07:19AM
Interaction with planetary magnetic fields is also a MUCH simpler explanation for fly-by anomalies (which only happen near a planet, in its magnetic field)...
Is it? What do you mean by "interaction"? Has anyone actually done the numbers or this just a vague "hmm, might be some kind of interaction" thing?
Do they not teach that one should at least ATTEMPT to disprove the null hypothesis
What's the null hypothesis here? We know there's something weird going on with probes; we don't know what's causing it yet. Is it normal to set the "most likely" explanation we have so far as a null hypothesis?
systemd is Roko's Basilisk
(Score: 0) by Anonymous Coward on Friday April 22 2016, @01:15AM
Maybe it releases "anti-gravity waves". In a sense when it takes off it 'pushes' against any objects around it just like gravity 'pulls' against you. There is both an action and a reaction.
How fast is the gravitational signal. When you move from one location to another the gravitational force you exert on a distant object, such as the moon, changes. How long does it take for the change in gravitational force due to your movement to take effect on the distant object?
(Score: 3, Funny) by isostatic on Friday April 22 2016, @01:34AM
Sadly gravity moves at the speed of light (or rather distortions in space time propagate at the speed of light)
It's all relative though.
(Score: 0) by Anonymous Coward on Friday April 22 2016, @12:42PM
Sadly gravity moves at the speed of light (or rather distortions in space time propagate at the speed of light)
Doesn't light and fluctuations in space-time propagate at the speed of causality? The Speed of Light is NOT About Light [youtube.com]
(Score: 2) by GreatAuntAnesthesia on Friday April 22 2016, @08:58AM
Your ideas put me in mind of this:
-- The first men in the moon, H G Wells, 1901.
Of all the science fiction I've ever watched or read, I don't think any one of them has come up with such a beautifully simple, effective and entertaining fictional technology for space travel than Wells' Cavorite. If such a thing existed we could be eating McDonalds on Mars within a decade.
(Score: 0) by Anonymous Coward on Friday April 22 2016, @03:38AM
The following makes me wonder if the effect has an orientational dependence:
|a| is the magnitude of the relative acceleration of the object relative to surrounding matter.
...
Eq. 1 predicts that for terrestrial accelerations (eg: 9.8m/s^2) the second term in the bracket is tiny and standard inertia is recovered, but in low acceleration environments... the second term in the bracket becomes larger and the inertial mass decreases in a new way so that MiHsC can explain galaxy rotation without the need for dark matter (McCulloch, 2012) and cosmic acceleration without the need for dark energy (McCulloch, 2007, 2010).
/AC because I feel like this should be obvious
(Score: 2) by bitstream on Friday April 22 2016, @09:07AM
MIT Technology review:
McCulloch’s idea is that inertia arises from an effect predicted by general relativity called Unruh radiation. This is the notion that an accelerating object experiences black body radiation. In other words, the universe warms up when you accelerate. /../ inertia is simply the pressure the Unruh radiation exerts on an accelerating body.
Does that possibly implicate that inertia possibly changes on a small scale with time?
The idea is that if photons have an inertial mass, they must experience inertia when they reflect. But the Unruh radiation in this case is tiny. So small in fact that it can interact with its immediate environment.
If the sent particles are even smaller than photons, then the thrust becomes larger? or just thrust internally?
If there's no exhaust velocity in the traditional sense. What maximum speed can it achieve? The ion engine can manage circa 0.1c. (Hopefully NASA or SpaceX will test the EmDrive in space..)
Are there any interesting implications that this new theory and experiment predicts?
DOI 10.1209/0295-5075/111/60005 - Testing quantised inertia on the emdrive [arxiv.org]
(Score: 1, Interesting) by Anonymous Coward on Friday April 22 2016, @09:23AM
Most scientists have snorted at the idea, noting correctly that such a thing would violate physical laws.
What kind of BS is that?
a. They certainly didn't note anything "correctly". That's akin to say, in 1915, "Newton's fanbois snorted at the idea of relativity noting correctly that such a thing would violate physical laws".
b. There is no such things as "violating physical laws". An experiment can only ever agree with or contradict a physical theory, for the latter we either find what's wrong with the experiment or adjust the theory (or we dump it altogether and write a new one). The former just shows "alright, for this experiment the theory applies fine" but it doesn't prove the theory globally.
(Score: 3, Insightful) by maxwell demon on Friday April 22 2016, @01:05PM
Of course there is. If such a violation is found and confirmed, you know that the law has only a limited range of applicability, and you've found a phenomenon beyond that range.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by bitstream on Friday April 22 2016, @02:40PM
The validity of laws seems to also depend on scale. Or rather their influence only have significant impact at a certain scale.
(Score: 2) by Capt. Obvious on Friday April 22 2016, @10:12PM
To use your 1915 example. It would be correctly noted that relatively violated [implictly implied: our codification of] physical laws (which it did, which is why they added that Newton's laws start breaking down when you go really fast. It would incorrectly noted that it violated physical laws because light moved at infinite speed. That is, it was already known to move at a finite speed.
(Score: 2) by bitstream on Friday April 22 2016, @09:25AM
The table on page 6 and the Chinese results as last row from DOI: 10.1209/0295-5075/111/60005:
850 W 16.00 mN 18.82 µN/W
1000 W 147.00 mN 147.00 µN/W
10.5 W 9.00 mN 857.14 µN/W
16.9 W 0.09 mN 5.38 µN/W
16.7 W 0.05 mN 2.99 µN/W
2.6 W 0.06 mN 21.15 µN/W
50 W 0.03 mN 0.60 µN/W
700 W 0.07 mN 0.09 µN/W
1290 W 395.00 mN 306.20 µN/W
Any uncertain input data have been averaged so as to get an estimate.
For the most efficient EmDrive:
Experiment=C1 Fetta, 2012 [aiaa.org] (DOI: 10.2514/6.2014-3853)
P = 10.5 W
Q = 11*10^6
L= 0.03 m
wbig/wsmall = 0.22/0.2
F1d = 5.3 mN
F3d = 7.3 mN
Fobs = 9 mN
Now we just need a test in space.