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China Claims Tests of 'Reactionless' EM Drive Were Successful (popsci.com)
An anonymous reader quotes a report from Popular Science: The "reactionless" Electromagnetic Drive, or EmDrive for short, is an engine propelled solely by electromagnetic radiation confined in a microwave cavity. Such an engine would violate the law of conservation of momentum by generating mechanical action without exchanging matter. But since 2010, both the United States and China have been pouring serious resources into these seemingly impossible engines. And now China claims its made a key breakthrough. Dr. Chen Yue, Director of Commercial Satellite Technology for the China Academy of Space Technology (CAST) announced on December 10, 2016 that not only has China successfully tested EmDrives technology in its laboratories, but that a proof-of-concept is currently undergoing zero-g testing in orbit (according to the International Business Times, this test is taking place on the Tiangong 2 space station). If China is able to install EmDrives on its satellites for orbital maneuvering and altitude control, they would become cheaper and longer lasting. Li Feng, lead CAST designer for commercial satellites, states that the current EmDrive has only a thrust of single digit millinewtons, for orbital adjustment; a medium sized satellite needs 0.1-1 Newtons. A functional EmDrive would also open up new possibilities for long range Chinese interplanetary probes beyond the Asteroid belt, as well freeing up the mass taken up by fuel in manned spacecraft for other supplies and equipment to build lunar and Martian bases. On the military side of things, EmDrives could also be used to create stealthier, longer lasting Chinese surveillance satellites.
>Reactionless
Certainly not reactionary. If it was, research chief would've been standing in from of firing squad by now
This is not an EmDrive. It's a drive of the same type as an EmDrive, resonant cavity thrusters, but EmDrive is a trade mark for one particular variant by Satellite Propulsion Research Ltd, which this isn't.
First, it's a drive, yes? And it's using electromagnetism, yes? Therefore, it's at best merely descriptive, and therefore not a protectable trademark.
Second, the ElectroMotive Designs company already has a registration on the EMDRIVE mark for converting cars and trucks to hybrids. So, Satellite Propulsion Research can go suck on the smaller end of a resonant cavity.
Not good enough for the spaceship, though. Adding a substantial amount of mass to gain a couple of millinewtons of trust isn't too helpful.
Those millinewtons can be applied over a very long time though, allowing significant speeds to be achieved. Moreover, missions to far-away objects would no longer have their lifetimes limited by running out of fuel.
If it works how some scientists think it works, that would indeed rewrite the laws of physics as we know them -- and this is scary
Why is it scary? The physical models we have now are good enough for all of the machines that we've built (indeed, many of them are fine with models a few centuries old). Stuff isn't going to break as a result of this, but stuff that we'd previously thought was impossible now might turn out not to be and physicists have a lot more work to do to create models that explain them. That's a pretty exciting, but not very scary.
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A major, major problem with the reports is that the results vary so much, and their error bars do not overlap.
If someone says "we have conclusively measured the height of Madonna, and she's 1.8m high +-0.1m" - that is one thing. If further investigation says "1.85+-.1" - then that's great, and is a confirmation.
If the next person to measure her comes out with 47m+-10m - then they have not meaningfully replicated the measurement, and disparity of measurements by various groups is a hallmark of something being wrong.
This, combined with the fact that some people don't get it to work at all leads to it being plausible that in fact nothing is happening.
The thrusts reported don't overlap.
It doesn't, it just changes the numbers at which breakeven occurs to ones not easy to achieve on earth.
Unless you get to 1N/300000000W (in which case it is a well understood photon drive)
Photons have no mass but they do have momentum. You could, in theory, make an engine by pointing a torch in the opposite direction to the way you want to go and turning it on. Such an engine would have no reaction mass but would not violate the law of conservation of momentum.
There are three possibilities as I see it:
1. The device doesn't work
2. Something with momentum is being ejected but we just haven't found out what yet
3. The law of conservation of momentum is wrong.
Of the three, I would happily bet my house that it is not the third one.
All I want is a secure system where it's easy to do anything I want. Is that too much to ask ~~ Randall Munroe
Because there is a lot more to cosmology than gravity and movement. There are several theories to explain the movement of the galaxies - some of which do essentially come down to gravity behaving differently in some situations (like over very long distances).
So when you have more than one explanation for an observation - how do you choose one ? Well you do some more maths - and figure out what ELSE would be observable if the theories are true - and then see if any of those things can be observed. All of the theories make a number of these "predictions" and they all turn out false.
Dark Matter's predictions have all turned out to be true. Predictions way beyond the speed at which galaxies rotate. The presence of that mass, and where it is concentrated, would affect other things - and those things we can look for, and we've found them. And gravity bends light, so if there's a huge clump of unobservable matter somewhere, it would bend light -and we should be able to see that the light was bent (we've known how to observe graviational lensing since Einstein's days). Again we can see distinct patterns of graviational lensing that fit the predictions of dark matter theory and goes against what is predicted by every competing theory.
Now it's possible that along the way we'll come up with a different theory that explains observations better - but some of the smartest people in the world are trying and of all the ideas they've had none has matched the observations better, none have made predictions that better fit the other things we can observe. Right now, dark matter is by far the single strongest theory we have for explaining the way galaxies move - and the only one where the other things you can predict would be true is ALSO being observed. It's an extremely strong theory backed up by a lot of solid observations.
There are also active experiments to try and find a way to detect dark matter - partly this is made difficult since we're not sure what to look for, some people think it's made of very large, heavy particles and others that it is made up of tiny particles (but lots more of them) called "Axions". The idea that the EM drive may be using dark matter for fuel is based on the Axion idea.
But since we don't know - and have no real way of theoretically saying one is more likely than the other - we are looking for both. Doing all sorts of complex experiments to try and create conditions where - if dark matter is present we can force it to interact with something else and reveal itself. We haven't succeeded yet, but considering how difficult it is to look - we aren't giving up yet either.
Unicode killed the ASCII-art *
I haven't googled it, but I've always wondered why physicists are so certain that dark matter is a thing
Dark matter is a placeholder. It isn't necessarily dark, nor matter, or even a thing. Its more of "We're not certain exactly why some aspect of the universe isn't what we think it should be.
So you could declare everything wrong, and go back to the caves, or put in a placeholder so you can do further research and eventually figure out what the placeholder "dark matter" is.
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
Actually we do, for reasons that have nothing whatsoever to do with the EMdrive. For one: General relativity and quantum mechanics are fundamentally incompatible - something about requiring different vacuum energy levels if I recall correctly. Which implies that there's a flaw in one or both of those theories. And there are other such situations as well. And then there's the various observational anomalies that we can't yet explain, which strongly suggest that either something in our current theories is wrong, or that there are other forces at work that we haven't yet discovered.
All of which is perfectly normal - such incompatibilities and unexplained anomalies are the guideposts that we use to probe deeper into the rules governing the universe, and improve our theories so that they better reflect reality. If the EmDrive does indeed work, which is looking increasingly likely, then it's simply one more unexplained anomaly. It's noteworthy only because (A) at first glance it seems to violate conservation of momentum, something that has gone basically unchallenged since Newton first formulated it, and (B) it has clear immediate applications.
And perhaps also because, given (B), we may for a time find ourselves in the situation of building and optimizing increasingly powerful and expensive engines without having any solid theory of the physics that governs their operation. Which has been extremely rare in recent centuries, though you could argue that much of modern pharmacology falls in that category. For example, we have only vague and overlapping theories as to how, exactly, hormonal birth control prevents pregnancy, and much the same can be said of many other medications - proving that they do work is far simpler than understanding exactly how they're interacting with the body's incredibly complex bio-chemical systems to achieve their results. On a more "technological" front gunpowder is the most recent example that springs to mind - it was used and optimized for centuries before chemistry even existed as a formal field of study, to say nothing of having a reasonably solid theoretical basis.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
I'm pretty sure I remember you have previous posts calling people "space nutters", and are pretty rabid in attacking anything outside mainstream NASA. The claim that CAST has nothing just because the English version has nothing means nothing...unless you've gone through the Chinese language version and can prove the two sites contain the same information.
I found another reference in English at http://spaceflight101.com/shijian-17-rendezvous-with-chinasat-5a/: "and debuting a Hall-Effect Thruster system for use on future Chinese GEO satellites"
Digging into this via Google Translate does provide far more information. The information your claiming doesn't exist actually DOES exist, on the stdaily.com article. It's just all in Chinese, so you have to put some effort in to translate it. My link is at translate.google.com and https://translate.googleusercontent.com/translate_c?depth=1&hl=en&rurl=translate.google.com&sl=auto&tl=en&u=http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357005.htm%3Fdiv%3D-1&usg=ALkJrhhkYPDNKL_9BxSu6OAkt5KIHsse9Q but I don't know if this link will work for anyone else.
Using Google page translation:
Chen Yue said: "We use the classic electromagnetics and electrodynamics to design several different shapes of thrusters, theoretical analysis can generate thrust thrust, and through the test of the thrust, the results in line with theoretical analysis. Science and Technology Daily Beijing December 10 " Roger Xiaoe in an interview was also asked this "eternal" problem, he made it clear that the EM engine does not violate Newton's law of mechanics: "EM engine in a direction to generate propulsion, if circumstances permit, will In another direction, the momentum of the whole process is conserved. "This explanation is considered ambiguous.
"We have successfully developed several specifications of several prototype principle, the establishment of experimental verification platform to complete the milli-level micro thrust measurement test, through several years of repeated tests and the corresponding interference factor investigation test, confirm that the type of thruster Thrust exists. "Chen Yue introduced that they have completed the test device can be used for flight test development, is in orbit verification.
"This technology is currently in the latter stages of the proof-of-principle phase, with the goal of making the technology available in satellite engineering as quickly as possible," said Li Feng, chief architect of the China National Space Technology Institute's communications satellite division. , The principle prototype volume, thrust is small, require special engineering methods, optimize the cavity design, improve the cavity quality factor, reduce the loss, the microwave energy is more effective for generating thrust. At present, the thrust is measured to micro-cow level to millennial level, at least to improve the level of 100 cents or even cattle-level satellite can be used for attitude control, orbit and so on.
A few reference points:
The big reason the EM Drive is attracting any interest at all is that it seems to be generating thrust per watt ratios at least an order of magnitude greater than theoretically possible with a photon rocket (i.e. shining a laser/flashlight/microwave/radio source out the back end), so there's no accepted theoretical basis for the thrust it's generating, unless maybe it's actually vaporizing itself and leaking pressurized metal gas out the back end
It would also seem to break conservation of momentum, which has gone basically unchallenged since Newton first formulated the laws of motion and kick-started physics as a mathematical science. If the engine thrust imparts momentum in one direction, then something else needs to gain an equal amount of momentum in the opposite direction (e.g. the exhaust from a rocket), and within our current understanding, that doesn't seem to be happening.
Finally, conservation of energy (Ein=Eout + heat) could also be broken by a reactionless thruster as it's heavily dependent on speed. If the EmDrive generates a constant thrust for a constant energy input as it accelerates (completely untested), then its kinetic energy will increase at a steadily increasing rate, since energy increases with the square of velocity. At some point the incremental increase in kinetic energy will be larger than the incremental consumption of electrical energy, at which point you could theoretically attach it to the rim of a wheel turning a generator to produce more energy than you're consuming. (normal rockets don't face this issue since the exhaust is being slowed down while the rocket accelerates, so the total kinetic energy change remains constant.)
--- Most topics have many sides worth arguing, allow me to take one opposite you.