German Scientists Confirm NASA's Controversial EM Drive 518
MarkWhittington writes: Hacked Magazine reported that a group of German scientists believe that they have confirmed that the EM Drive, the propulsion device that uses microwaves rather than rocket fuel, provides thrust. The experimental results are being presented at the American Institute for Aeronautics and Astronautics' Propulsion and Energy Forum in Orlando by Martin Tajmar, a professor and chair for Space Systems at the Dresden University of Technology. Tajmar has an interest in exotic propulsion methods, including one concept using "negative matter."
Looking more and more likely all the time... (Score:4, Interesting)
Maybe this will be one that turns out not to be a scam...
Re: Looking more and more likely all the time... (Score:5, Informative)
Well NADA is an unlikely source for scams and it doesn't fit the pattern. The science behind it is openly shared without any secret sauce claims. The physics are uncontroversial.
The only thing there could be scam in is whether our engineering can really cash in on it.
At it's best its also not claimed to provide much thrust. You can't leave earth with it. But once you do even a tiny bit of thrust goes a long way. It's not even the only known way to get thrust without fuel - solar sails do that too.
I never got why so many people are so sceptical of this one. Engineering scams are nothing new but this breaks every pattern and the science is genuinely sound.
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Even if it only works as well as the experiments, it can make satellites smaller and longer-lasting.
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I second that. /. crowd in our days calls everything new a scam ... pretty retarded!
The
Re: Looking more and more likely all the time... (Score:5, Interesting)
Everything that's generally accepted today went through similar amounts of skepticism at some point and was borne out by repeated studies to prove its validity. Anything less and you've got something more akin to a religion and articles of faith.
Re: Looking more and more likely all the time... (Score:5, Informative)
Neither Newton's nor Einstein's theory of gravitation were greeted with "extreme skepticism" by the general community.
Re: Looking more and more likely all the time... (Score:4, Insightful)
Re: Looking more and more likely all the time... (Score:5, Insightful)
It's worth noting that there's a big difference between those theories and this engine. With this engine, they're putting forward a piece of technology and saying, "We don't know how this works, but we're claiming it does." In the case of Newton and Einstein, they put forward a mathematical model that was internally consistent, and the question was whether it applied to reality.
So in one case, they're putting forward a technology without a real explanation as to how it works, and in the other case, they're putting forward a coherent theory that seems to explain phenomena that we have witnessed. Also, both Newton and Einstein's theories had the benefit of providing a clean explanation to phenomena that we were having a lot of trouble explaining.
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I mean do you really think the laws of physics are different in different places? Cus that has to be true for this to be true.
Conservation of energy? This is a over unity device if
Re: Looking more and more likely all the time... (Score:5, Insightful)
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You are very wrong, any competent physicist would tell you so. You have made a religion in your mind about science.
We already know our models such as quantum theory and general relativity are incorrect; they break down in certain situations.
We already know the useful "laws" we use are just approximations, e.g. ohm's law, hooke's law, boyle's law, etc.
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We already know the useful "laws" we use are just approximations, e.g. ohm's law, hooke's law, boyle's law, etc.
That's exactly what GP was saying. Modern physics does not pretend to be anything more than a series of useful approximate predictions. A hammer is neither right nor wrong, it is merely useful or not useful. Same goes for Newtonian mechanics, relativity, quantum theory, etc.
Re: Looking more and more likely all the time... (Score:4, Informative)
> Modern physics is never incorrect.
And you, sir, have just turned science into religion.
The whole reason science is superior to religion is that it openly admits that it may be incorrect, and allows for itself to be corrected. It is, as you correctly outline, an iterative process that approaches truth over time. But part of that process is accepting that any truth may be overturned by new evidence. And while Einstein didn't "disprove" Newton, he did show flaws in the theory which meant that it was, in a very small way, wrong. And that's fine. Claiming it was "extended" and not "wrong" is playing semantics and makes you sound like a religious apologist.
The more comfortable we are with being wrong, and the process of refinement, the better scientists we are. The more we claim that some aspect of science is "never incorrect", the more dogmatic we are and the science suffers.
The predictions of modern physics are phenomenally accurate in many domains. But we haven't run tests in nearly enough domains to claim perfection yet. And we've no need to be defensive about it. Science is the only way to the next truth, and that's good enough for me.
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Re: Looking more and more likely all the time... (Score:4)
How are we to know which of our theories are accurate?
You should read "the relativity of wrong". It explains this stuff well.
Newton's law is never going to be disproved, ever. It's been extended with relativity and will probably be extended again. It is never going to be proven wrong because it produces exceptionally accurate predictions is everything you personally can see (pretty much provided you're not a physicist or astronomer).
In order to be disproven, it will have to stop making accurate predictions.
Re: Looking more and more likely all the time... (Score:4, Insightful)
> Because they predict things up to the level of accuracy that we can currently measure, within the very limited energy and size domains we have access to. That's all there is to it.
Fixed that for you.
When you can predict particle behavior inside a black hole with planck-length precision, or you can model gravity at the galactic scale without relying on unobserved "dark matter", I might be as confident as you that our current understanding is rock solid.
Re: Looking more and more likely all the time... (Score:5, Informative)
But I'll still be willing to listen to reasonable follow-up experiments instead of dismissing out of hand. So we get to Martin Tajmar and his claims (also not peer reviewed, but at least it's at a conference). Tajmar is not the guy I'd choose as the most reputable source. He has a history of claims about...creative physics from poor experimental setups. That is, he claims to observe new physics, but people have consistently had a hard time reproducing his results. Go ahead and google the guy.
I did, and appearantly it was Martin Tajmar himself, who found the flaw in his gravitational gyroscope thesis, and published it: FiberOpticGyroscope Measurements Close to Rotating Liquid Helium [aip.org]. So whatever you think about the guy, a superficial Google result seems to put him at least as honest. If he makes a mistake, he is able to admit it.
Re: Looking more and more likely all the time... (Score:4, Insightful)
The crowd is skeptical because we're being told by everyone, including the researchers, that this should be scrutinized closely because while this might be entirely new science, that is a very high bar to jump over for a reason.
Humanity clearly doesn't know everything about physics, but we know enough that we've done some fairly amazing practical things with it. Recent scientists are not banging rocks together to get sparks, or even walking around poking radium in 19th Century dresses. That means we pretty much know where we think we need to look for new science, and until recently, this was not one of those places.
So yes, being skeptical is a good idea here, although dismissing it outright seems to be unwarranted at the moment.
Re: Looking more and more likely all the time... (Score:4, Informative)
You do know that a reactionless drive means not only that momentum is not conserved. But that the laws of physics are different in different places. Also that energy is not conserved. A reactionless drive is always a over unity device. Or are you just batting for your beloved germans. Perhaps if this was done properly i would take them more seriously. But a magazine and a talk (not peer reviewed) don't count.
Also you really don't know your physics all that well.
Re: Looking more and more likely all the time... (Score:4, Funny)
It's because we are tired from telling all them damn kids at reddit to get offa our lawn
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Re: Looking more and more likely all the time... (Score:5, Insightful)
Eh... The physics mechanisms proposed ARE very controversial! The classic physics mechanism simply shouldn't work and the quantum physics proposal are far off speculations that aren't likely to be true.
But the amount of experimental verification from separate sources indicates that either there is some factor they all forgot or that there are new physics at play. I hope for the last alternative :)
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Sorry, your post is complete nonsense.
EM dive "theory" is a "forward theory".
Some guy thought: "it should work like that", and now experiments are confirming: "it seems to work like that.
There is no The classic physics mechanism simply shouldn't work.
Actually the drive works exactly according classic physics ... as state before (in other posts): I have no clue why the /. crowd disagrees.
However I'm looking forward for a formula showing that the EM drive can't work.
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as far as I know the skepticism started when early reports included the word "reactionless". I doubt anyone would have a problem with "microwave-emitting thruster"; lord knows we've heard enough about photon drives for that to make sense. But the early reports I recall were more like "microwave-induced magic", where the microwaves weren't supposed to leave the unit, just generate more thrust bouncing off one end than the other.
Re: Looking more and more likely all the time... (Score:4, Interesting)
Yep, the microwave cavity is sealed. Nowhere for them to go.
Also, even in these early and probably very inefficient (assuming the thing really works) trials, the thrust/power ratio is something like three orders of magnitude beyond what you'd get from a photon drive. No "microwave-emitting thruster" operating at these power levels would come even close to the sensitivity threshold of the experimental apparatus, much less reach several times that threshold.
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I never got why so many people are so sceptical of this one.
I think some of the skepticism is not as to whether this might be an engine that produces some small amount of thrust. I mean, a little skepticism is a healthy response for any new scientific discovery, and it's not inappropriate to ask for proof. Since the thrust we're talking about is so small, the margin of error is large, and proving that it really works takes a bit of doing. I don't assume that it works, but I also don't really disbelieve it if NASA scientists say it does.
However, when this was rep
Re: Looking more and more likely all the time... (Score:5, Informative)
The physics are most certainly NOT uncontroversial.
If this thing were to truly work, it would have insane implications to some basic assumptions about the universe - namely about the very laws of physics themselves.
This device working means that the laws of physics do vary by translation, which goes against every single other observation ever made. The science behind it is most certainly not clearly sound. Skepticism is the only logical option for this thing.
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The physics are most certainly NOT uncontroversial.
If this thing were to truly work, it would have insane implications to some basic assumptions about the universe - namely about the very laws of physics themselves.
This device working means that the laws of physics do vary by translation, which goes against every single other observation ever made. The science behind it is most certainly not clearly sound. Skepticism is the only logical option for this thing.
IMO, as someone with a background in science, scepticism is the only logical option for science. I'm sceptical of all scientific results. Thats how progress is made, by not taking things at face value.
Re: Looking more and more likely all the time... (Score:5, Informative)
People are so sceptical of this one because if true the implications are universe-shaking. It would completely overturn not just modern physics but all of physics since Newton. The claim is that the device violates conservation of momentum. Then via Noether's theorem [wikipedia.org] this implies that the laws of physics are not independent of location in space. (Alternatively, the device is creating a beam of hard to detect particles via some completely unknown but low energy mechanism.)
Also, the device was first designed using a provably incorrect analysis - an analysis using standard physics determined that the device would produce thrust without reaction mass, violating conservation of momentum. As all the standard physics used in the analysis conserves momentum, the analysis must be incorrect. If someone adds up many even numbers and comes up with an odd total, we know they have made a mistake, even without examining their calculations to find out where. This case is exactly analogous. So if this device really does violate momentum conservation, it is a complete and utter fluke, and not by design.
Compare to the Higgs boson (Score:5, Informative)
Looking at this another way:
When LHC were looking for the Higgs boson - a particle entirely expected by modern physics - they required a five sigma signal before they were satisfied that they had really found something.
This is a result not only entirely unexpected, but contradictory to almost all known physics. A two sigma (NASA) and three sigma (Germany) signal is not remotely enough to be convincing. At best it is convincing enough for someone to spend the money to further and better test it.
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> The science behind it is openly shared without any secret sauce claims.
There is no 'science behind it'. At best there's some experimental data which is probably measurement error or a mundane effect that isn't being considered.
> the science is genuinely sound.
Actually, the claim of "thrust without reaction mass" is not only unsound, it's so far off the scientific deep end that it boggles the mind. You may not need to carry any propellant for this engine to work, but you sure as heck need to carry
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Re: Looking more and more likely all the time... (Score:4, Informative)
Not necessarily. Leading WAGs include that it is thrusting against dark matter or space itself. In those scenarios, momentum is still conserved.
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Noether's theorem doesn't "fall." In this context it says (roughly) that if the laws of physics are the same in all places then linear momentum is conserved. We believe that the laws of physics don't vary with position, but they could.
Also, there are various explanations for how the drive could work without violating conservation of momentum. They require some other interesting violations of things we currently believe to be true, but aren't necessarily.
Physics time! (Score:5, Interesting)
It appears to impart momentum to something without an opposite momentum imparted to anything else... you know, the basic concept of how every other propulsion system in the world works?
When you walk, your feet push against the ground, imparting a (tiny, relative to the mass of the Earth) amount of momentum to it at the same time that your feet impart momentum to your body.
When you sail a boat, the sails alter the momentum of the wind, and an opposite alteration is imparted to the momentum of the boat.
When a rocket engine fires, it releases exhaust with a lot of momentum going one way, and the rocket receives the momentum going the other way.
This model holds for any kind of propelling of anything. Even a flashlight projecting photons imparts a tiny, tiny bit of momentum to your hand, to your body, to the earth. Magnetic propulsion, chemical propulsion, ion propulsion... all of them operate on the principle of "we go this way, by making something else go that way".
The EM Drive appears to go one way without making anything else go the other way. It releases no exhaust, pushes against no solid or fluid, emits no photons, and interacts with no external magnetic fields. We don't know how it works (there are a number of theories, none of which are that widely accepted), and we still aren't 100% sure it does work (maybe it's still all experimental error... that becomes less likely with each independent verification, but extraordinary claims call for extraordinary evidence), but if it does work it does so in a way that is outside our current understanding of physics. That is a Really Big Deal.
One way or another, this is exciting!
Re: Physics time! (Score:3)
Ah so its like VMware?
Re:Physics time! (Score:5, Insightful)
A) That's one hypothesis among several, and many physicists claim it is, to use your term, "bollocks". I did mention there are multiple theories about how it works. They all have supporters, but they all have counterarguments too.
B) No, classical rocket engines push real particles one way and itself the other way. Unless you intend to claim that "virtual" and "real" particles are the same thing, it's not working "exactly the same way". Analogously, perhaps, but hardly "exactly the same".
Oh, and just for the heck of it:
C) To conclusively state that the EM Drive works according to your preferred theory is quite absurd unless you're an extremely well-educated theoretical physicist, and only slightly less even then. To even *claim* that I claimed anything about how the drive works, much less that my supposed idea is "bollocks", indicates a lack of reading comprehension, lack of understanding of the concept of scientific hypotheses, and lack of maturity.
Good day to you.
Re:Physics time! (Score:5, Informative)
Except it doesn't. The microwaves are not emitted anywhere. They are generated into a sealed chamber. There's nowhere they can go.
The formulae you listed would be useful to describe thrust from a photon drive (or light drive), but those need an open-ended emitter. Also, the results you get from them are about three orders of magnitude too low for the observed ratio of thrust to power. A 700W microwave photon drive wouldn't be detectable by the experimental apparatus.
Re: Looking more and more likely all the time... (Score:5, Informative)
It cannot be incomplete, it is a purely mathematical statement.
Particularly, for linear momentum, conservation of linear momentum is equivalent to the laws of physics being symmetric by translation.
If linear momentum is not conserved, the laws of physics are not the same throughout the universe and vice-versa.
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It will take a demonstration satellite accelerating through space before the physics community goes into party mode. Until you're in free fall and vacuum, there is too much scope for systematic errors to accept a result of this level of importance.
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"Maybe this will be one that turns out not to be a scam..."
It won't be a scam. It will be some tiny bit of unaccounted for noise in the experiment.
Excellent news! (Score:5, Insightful)
Fuel Efficiency? (Score:3, Funny)
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Depends on how much pressure it takes to compress them into a liquid.
Irony: Liquid Microwaves that won't cook yer Hotdog.
Not quite. (Score:5, Informative)
What more do I need to say?
Re:Not quite. (Score:5, Informative)
How about the very next sentence?
Nevertheless, we do observe thrusts close to the magnitude of the actual predictions after eliminating many possible error sources that should warrant further investigation into the phenomena.
Interesting, but still a lot of hype (Score:2)
This is really amazing and hopefully it is turning into a window into parts of our universe that we've never imagined.
But, reading the articles, I think we're a long way off from understanding what this phenomena is and how to exploit it practically. Going back over the previous articles, the measured force was for 50 uN from 50W of power - this doesn't seem like a very practical application as yet; the claims of round trips to Mars in less than a year are very exaggerated.
On that point, I thought we could
Believe it when I see it (Score:5, Informative)
I'm very hopeful this works. It's easy to be cynical, so I won't say "meh it's all bullshit!" Still, I won't be convinced until I see it provide thrust in a vacuum, away from Earth's magnetic field. It's still far, far too likely it's pushing off something terrestrial. So I'll give them a healthy "go, team, go!"
That said, quoth the article:
"This is the first time that someone with a well-equipped lab and a strong background in tracking experimental error has been involved, rather than engineers who may be unconsciously influenced by a desire to see it work," notes Wired referring to Tajmar's work.
I don't know about that. He is a real professor at a real university, but he also has filed for a patent on a gravity generator [wikipedia.org], using a process no one has duplicated. Somebody who thinks they've got a gravity generator, but gosh just can't prove it to everybody else, is definitely somebody who may be "unconsciously influenced by a desire to see it work."
Re:Believe it when I see it (Score:5, Insightful)
Skeptical != cynical.
From the published paper... (Score:5, Informative)
In the conclusion section:
The nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic
interaction of the power feeding lines used for the liquid metal contacts. Our test campaign can not confirm or refute
the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods
used so far. Nevertheless, we do observe thrusts close to the magnitude of the actual predictions after eliminating
many possible error sources that should warrant further investigation into the phenomena. Next steps include better
magnetic shielding, further vacuum tests and improved EMDrive models with higher Q factors and electronics that
allow tuning for optimal operation. As a worst case we may find how to effectively shield thrust balances from
magnetic fields.
Slashdotted (Score:2)
If somebody still has the article on their screen, please post a text copy-paste.
Full Text + links from Hacked.com (Score:5, Informative)
Scientists Confirm 'Impossible' EM Drive Propulsion
Science News, Space / July 27, 2015 / by Giulio Prisco/
Later today, July 27, German scientists will present new experimental results on the controversial, "impossible" EM Drive, at the American Institute for Aeronautics and Astronautics' Propulsion and Energy Forum in Orlando. The presentation is titled "Direct Thrust Measurements of an EmDrive and Evaluation of Possible Side-Effects."
Presenter Martin Tajmar is a professor and chair for Space Systems at the Dresden University of Technology, interested in space propulsion systems and breakthrough propulsion physics.
A Revolutionary Development for Space Travel
The EM Drive (Electro Magnetic Drive) uses electromagnetic microwave cavities to directly convert electrical energy to thrust without the need to expel any propellant. First proposed by Satellite Propulsion Research [emdrive.com], a research company based in the UK founded by aerospace engineer Roger Shawyer, the EM Drive concept was predictably scorned by much of the mainstream research community for allegedly violating the laws of physics, including the conservation of momentum.
However, NASA Eagleworks – an advanced propulsion research group led by Dr. Harold G. “Sonny” White at the Johnson Space Center (JSC) – investigated the EM Drive [nasaspaceflight.com] and presented encouraging test results in 2014 at the 50th Joint Propulsion Conference.
White proposes that the EM Drive’s thrust is due to virtual particles in the quantum vacuum that behave like propellant ions in magneto-hydrodynamical propulsion systems, extracting "fuel" from the very fabric of space-time and eliminating the need to carry propellant. While a number of scientists criticize White's theoretical model, others feel that he is at least pointing to the right direction. The NASASpaceFlight [nasaspaceflight.com] website and forums have emerged as unofficial news source and discussion space for all things related to the EM Drive and related breakthrough space propulsion proposals such as the Cannae Drive [cannae.com].
Shawyer has often been dismissed by the research establishment for not having peer-reviewed scientific publications, but White and Tajmar have impeccable credentials that put them beyond cheap dismissal and scorn. Physics is an experimental science, and the fact that the EM Drive works is confirmed in the lab. "This is the first time that someone with a well-equipped lab and a strong background in tracking experimental error has been involved, rather than engineers who may be unconsciously influenced by a desire to see it work," notes [wired.co.uk] Wired referring to Tajmar's work.
Hacked has obtained a copy of Tajmar's Propulsion and Energy Forum paper, co-authored by G. Fiedler.
"Our measurements reveal thrusts as expected from previous claims after carefully studying thermal and electromagnetic interferences," note the researchers. "If true, this could certainly revolutionize space travel."
"Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts," conclude the researchers. "Nevertheless, we do observe thrusts close to the magnitude of the actual predictions after eliminating many possible error sources that should warrant further investigation into the phenomena. Next steps include better magnetic shielding, further vacuum tests and improved EMDrive models with higher Q factors and electronics that allow tuning for optimal operation."
Contrary to sensationalist reports published by the sensationalist press, the EM Drive is not a "warp drive" for faster than
ah, Tajmar eh? (Score:5, Informative)
Tajmar made a lot of hoopla over ten years ago about making gravitomagnetic waves orders of magnitude more powerful than GR predicted; some were claiming we were on our way to artificial gravity or a warp drive by his bold claims. Of course, his experiments could never be duplicated. Since then, he's been trying to make waves (ha!) with other dubious claims of making gravity effects by electromagnetic means and such.
Take anything he claims "confirmed" with a one hundred pound bag pinch of salt.
Re: (Score:3)
Can't this be tested on a Cube Sat? (Score:5, Interesting)
Just thinking about this, how expensive would it be to create a small, simple satellite, with solar cells, some large LiPoly batteries, a transponder and an EM drive that fires up every time there is enough juice in the batteries to run it for a few minutes?
Sticking with the 50nN thrust level for 50W of input and assuming that a 1kg LiPol battery has 260Whr available (https://en.wikipedia.org/wiki/Lithium_polymer_battery), that is approximately 5hr of running time and assuming that the satellite is 5kg, there will be a 10nm/s^2 acceleration.
5 hours is 18,000s so there should be a delta-V imparted on the satellite of 1.8(10^-4)m/s which is tiny (I did say this is a pretty useless drive at the current time right now) but should be measurable or at least noticeable to its relative position to a control satellite that was launched along with it.
The /. title is bullshit (Score:5, Informative)
Here [aiaa.org] is the first page of the actual paper, including the abstract which says:
Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurement methods used so far.
So the /. title says pretty much the exact opposite of what the actual
paper says.
I am still extremely skeptical that there is any actual effect. They powered their device with a 700 watt magnatron and measured plus or minus 20 micro-newtons of thrust. To put this in perspective, one Newton is roughly the weight of an apple near the surface of the Earth. If the thrust scales linearally with input power then you would need 50,000 x 700 Watts = 35 Megawatts to levitate a single apple. Of course the inventor claims that the thrust to power ratio is highly non-linear so at these higher power levels you would get a lot more thrust. I have not seen any sensible theoretical model that explains why this would be so.
If you are using hundreds of watts to produce a handful of micro-newtons then it is extremely likely there is no actual effect and what is being measured is just some form of noise. This is especially true when the so-called effect violates a primary law of physics.
The Dean Drive is back (Score:4, Informative)
There was a similar set of claims roughly 60 years ago for the "Dean Drive" a "reactionless drive" that did not seem to use propellant. To casual review, and letting it push your hand, it seemed to work, and a great campaign for research and to ignore the sceptics of the time was headed by John W. Campbell, the editor of Analog magazine. Analog was, and remains, a science fiction magazine specializing in hard science and science fiction based on it, and it had many real scientists as readers and contributors, so the Dean Drive received quite a lot of attention.
The Dean Drive has since been pretty thoroughly debunked as an "oscillation thruster", a device that relies on tuned "slipping" on the floor it rests on to creep forward and even to provide a modest thrust, _pushing against the floor_. The designer was never willing to allow a full "pendulum" test, or careful testing outside of his own workshop, and there seem to be dozens more of similarly patented "reactonless drives". The ones that work at all also seem to be "isicllation thrusters", pushing against the floor or the mehanism in which they are mounted.
Yeah for EM Drive! (Score:5, Insightful)
I've been following this invention for years; since the first announcements from Shawyer through his being trashed by various physicists and wanna-bees, through his redemption through work in China and NASA. It used to be very difficult to get information, but since the burst of activity on the NASA Space flight forums, there's now too much information to digest, especially for someone like me who only has an undergrad level of schooling in it. If you want lots of details and discussion, check it out - but please don't post unless you really know what you're talking about, as there's already been a hell of a lot of noise. http://forum.nasaspaceflight.com/index.php?topic=37642.0
Stop calling it "NASA's" (Score:3, Insightful)
Re:Blimey (Score:5, Insightful)
A propulsion device that provides thrust without using reaction mass would be an earth-shattering advance, assuming the amount of thrust is non-negligible. I hope you do get that.
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This could provide a basis for a 'constant acceleration drive', that could travel interstellar distances without requiring a reaction mass
https://en.wikipedia.org/wiki/... [wikipedia.org]
Re:Blimey (Score:5, Funny)
Until you travel at 0.7c and you discover the batteries are dead because solar isn't working at this speed so you cannot slow down.
Re:Blimey (Score:5, Interesting)
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True, but this means your source of energy can be very compact and efficient.
For instance, you can employ a nuclear reactor. Still somewhat heavy and complex, but a lot lighter, and much more efficient than having to carry your reaction mass with you just so you can shoot it out the back. If we got reactor design compact and advanced enough, it could actually be fairly simple to operate.
Previously, the only way to make use of nuclear power was to basically accelerate the ship by throwing nuclear bombs out
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For outer system stuff you'd use a nuke.
"Fuel" in terms of energy isn't the problem in a rocket. The problem is the requirement to haul around reaction mass: stuff to throw out the back. If you don't need to do that, the tyranny of the rocket equation goes away and space travel suddenly becomes a much different proposition.
Re: Blimey (Score:3)
Even if it's negligible, if it's greater then zero then sone very fundamental things we thought we knew about the world are wrong.
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ANY non-zero amount of thrust requires reaction mass, even if the amount of thrust is 'negligible'. Sometimes the reaction mass is stored externally (e.g. light sails), sometimes it's a planet (orbital magnetic thrusters) but it's always there.
Either no thrust is being produced or there is reaction mass. You just have to find out what it is. If the reaction mass is not sufficient to explain the thrust, then it's bunk. Plain and simple.
Re:Blimey (Score:5, Informative)
Re:Blimey (Score:5, Insightful)
You aren't following what he is saying--the research is saying is that THERE IS NO REACTION MASS. Per current physics, this device can't exist. That is why this is so big. No current physics explains it. It is not the opposite of a solar said, since the microwaves don't actual exit the device. If this device works, it does change everything, if only to point to new physics.
Re:Blimey (Score:5, Insightful)
Re:Blimey (Score:5, Insightful)
I'm with you man, but this was exactly the same thing that people said when NASA confirmed the results. I was with you then too. Skeptisisism and all that.
The fact that the Germans now have also confirmed this is pretty huge. I'd say this moves out of the 'anomalous experiment' territory and more into the 'can we devise more and newer experiments to understand what the flaven is happening here' zone.
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There is a place for scientific skepticism, and what you are saying is all well and good. And pretty well articulated too-- that's unusual among the pure science worshippers.
But scientists do not advance our technologies. That is done by engineers. And engineers are grubby guys who don't care much about how a thing works, so long as it does work in a reliable way. That pragmatism is why we've got bicycles even though the physicists are still scratching their heads over the self-correcting stability of thes
Re:Blimey (Score:5, Insightful)
Conservation of momentum is more than "new physics". It's quite fundamental, thanks to Noether's Theorem [wikipedia.org]: conservation of momentum is mathematically equivalent to "the laws of physics don't vary with spatial coordinates", that is, the X, Y, and Z axes can be "zeroed" anywhere, the choice of coordinates are arbitrary as long as their consistent. The universe would be a very strange place indeed if this weren't true, and furthermore we'd have noticed by now.
So, whatever's going on here, momentum is being conserved. Just how that's happening is the curious bit. It wasn't obvious until the early 1900s that light had momentum - maybe there's something else we're missing, or maybe this really is an actual "warp" drive that locally changes the metric of space (in a way different from GR) and momentum really isn't conserved. Somehow I doubt the latter is true.
Re:Blimey (Score:5, Informative)
Photons have no rest mass. Their mass is entirely their energy. They do have mass.
This isn't new. They had to correct for Pioneers microwave thrust. Heat thrust is the accepted explanation for the Pioneer anomaly.
Re: (Score:3)
Existing electric propulsion devices (like ion thrusters) still use propellant, they're just really efficient.
The EM drive would appear to use no propellant, meaning the limitations would only be the amount of electricity that could be produced, along with how long the EM drive could operate before it degrades.
Re: (Score:3)
they're just really efficient in a vacuum.
Fixed that for you. Well, for your reader anyway - you probably understand it. Because of the way these things work, they are just about useless anywhere other than a vacuum. The only way you can spend a tiny tiny amount of energy accelerating particles to massive speeds is when there's nothing else in their way for them to bounce off of. But if you are not in any kind of rush for your delta v and are in near total vacuum this is almost a perfect engine.
Some clarifiications (Score:3, Informative)
A photonic rocket does not use reaction mass, and expels massless photons, i.e. radiation. You simply heat something, and the heat emissions generate opposite thrust. This generates thrust as photons lack mass but do have momentum, relating to the Planck length. The pr
Re:Blimey (Score:5, Informative)
It still has to drag all that reaction mass along, despite it's only real purpose being that it's thrown out like garbage just to provide thrust.
It takes thrust to push that reaction mass around the place, up until you actually throw it out the window, which is actually out the directed nozzle or whatever.
And what happens when you run out of reaction mass? You have no more thrust.
On the other hand, if you have a reactionless thruster, as long as you provide it with power, it will give you thrust. Slap on solar panels, or if it's a deep space mission, nuclear batteries or the like, and you are set.
As an added bonus, you can use that constant acceleration trick to really build up some speed. Something you can't do with reaction mass because you don't ever have enough, even for a tiny trip like to the moon.
Re:Blimey (Score:5, Interesting)
As an added added bonus, such a drive would accelerate faster at a given thrust, because of the absence of reaction mass. Conventionally, acceleration steadily increases at a given thrust as reaction mass is ejected, with maximum acceleration being reached just before reaction mass is exhausted.
We can dream, can't we?
Re: (Score:3, Informative)
Of course they do. Ions are simply an atom that has either gained or lost electrons and now has a net electric charge, either (+) or (-). As such, they are made up of protons, neutrons and electrons, all of which have mass.
Re:Blimey (Score:5, Funny)
A ion drive requires reactionary mass to work.
I've been quoting Evola and Metternich to this bowl of water for hours now, how much longer until it turns reactionary?
Re: (Score:3, Informative)
Ahem ... that would be an _ostensible_ propulsion device, the working principle for which is (according to mainstream physicists) poorly described and violates commonly accepted physical principles. OTOH, I hope it works. I'll believe it when they cram a couple of megawatts in, and get it to lift its own weight - or better, 100 times its own weight.
I note that the Dr. Tajmar, the researcher whose name is on the paper, is still using terms like "... if true ...". This is not yet a tried-and-true propulsio
Re:Blimey (Score:5, Insightful)
Lifting its own weight is irrelevant. Existing electric propulsion thrusters couldn't come remotely close to lifting their own weight, and yet are still in active use in space.
Re: (Score:3)
History is replete with examples of commonly accepted physical principles undergoing revision in response to unexpected discoveries. I expect, along with nearly everyone else, this is the result of bad experimentation. But you never know.
Re:Blimey (Score:5, Informative)
Bad example. Light does exert radiation pressure, yes - but it is far, far too weak to drive a radiometer. The spinning radiometer isn't due to radiation pressure. It's a more mundane effect: Imperfect vacuum. The black side is warmed more than the white, which heats up adjacent air, which exerts higher pressure, causing the spin. It's just a plain old heat engine.
Re:Blimey (Score:5, Informative)
Thank you for enlightening me. I read the wikipedia page on radiometers: https://en.wikipedia.org/wiki/... [wikipedia.org]
I learned that radiometers do NOT work by "light pressure" which was Crooke's, the inventor's, hypothesis. Radiometers do NOT spin in a perfect vacuum. The two mechanisms that explain why they spin were proposed by the likes of Einstein (relativity guy), Maxwell (equations guy), and Reynolds (number, not aluminum, guy).
Re: (Score:3)
Re: (Score:3)
It's one thing to question the very preliminary theory of operation for the thing, it's quite another to demand that it is doing nothing just because it would be inconvenient.
My gut feeling is that whatever it is, it won't violate conservation of momentum.
Re:I'll wait until (Score:5, Insightful)
MythBuster's is so full of junk science that I feel dumber after watching an episode and find myself wondering things like the will the great ball of fire in the sky rise tomorrow and is the earth flat.
Re: (Score:3, Insightful)
MythBuster's is so full of junk science that I feel dumber after watching an episode and find myself wondering things like the will the great ball of fire in the sky rise tomorrow and is the earth flat.
Or did you stop liking it when non-nerds started watching it, forcing you to find other ways to express your nerd-hipsterism.
Re:I'll wait until (Score:4, Insightful)
Mythbusters' pop skepticism is the very definition of junk science.
If you're waiting for confirmation from Penn Jillette or some other aging magician or Skeptical Inquirer, you missed out on a successful career as an economist.
Ooh Oopsie (Score:5, Funny)
Re:extracting "fuel" from the very fabric of space (Score:5, Informative)
something with a very long, low-thrust burn such as DS1's ion propulsion* and enough fuel to run for half a century maybe, Voyager 1 left the Sun's influence last year - nothing launched from Earth will ever catch it using gravity assists. New Horizons might be travelling at twice the speed of Voyager right now but it's not even 40AU out, by the time it gets to apoapse it'll be travelling slow enough to drop back - it's in a 100AU heliocentric orbit.
*the Dawn spacecraft, currently in orbit around Ceres, also uses ion propulsion - the same NSTAR 2100W engine as DS1, in fact.
Re: (Score:3)
I thought that was the Q thruster, it's this the one that bounces photons around in an asymmetric cavity?
The Q's thruster got Janeway all excited...
Re: (Score:3)
You're confused, an ion engine is a type of rocket. The problem with this type of drive is too much thrust is claimed for the amount of energy expended. You really can propel something with photons, whether microwave or light, since photons have momentum. But it's to the tune of a newton per 300 megawatts; in other words a fiendish amount of power to get a very small amount of thrust. Our universe is perverse like that.
This "physicist" Tajmar has made all kinds of absurd unreproducible claims and exp
Re:Why the controversy? (Score:4, Informative)
Note, for the record, that an ion thruster IS a rocket - it shoots mass out the back (ions, in this case, accelerated electricly) just like any other rocket.
Note that if this EM drive pushes photons out the back, it is also a rocket. However, what I've read on the subject says it doesn't push photons out the back (not even microwave photons), so it's either something unexpected, or a huge steaming pile.
I'll be interested in the first deep-space probe built to test this thing. Should be simple enough - solar panels for power, EM-Drive for push, a comm-channel or six, and something to announce its presence, so we can determine its velocity relative to Earth at all times. If it accelerates, we win. If not, we wasted the cost of a (small) satellite....
Physics time! You misunderstand ion drives (Score:4, Informative)
I wrote a comment on this up above, but just to help you understand...
1) No, the ion drive does not use electricity to produce thrust. Ion drives, as their name suggests, use ions to produce thrust. The ions are accelerated using fields generated via electric power, but that's no more a case of using electricity to (directly) produce thrust than an electric car is (the car pushes against the road, imparting momentum to the earth which balances the momentum imparted to the car).
2) Yes, it sounds like a free energy machine. If a given amount of electrical power produces a given thrust, constantly, without consuming any fuel, then you can generate unlimited energy by attaching this thing to a flywheel or rotor arm that drives a generator and it will produce more energy than it requires to drive the thruster. Some of the current theories about this thing claim that it won't do that, that its efficiency will go down the faster it's moving (relative to a given frame of reference).
3) No, electricity is not fuel. Electricity is not a thing. It is a process. Electricity is the motion of electrons. It is a form of energy. Fuel is a way to store energy, but it is not energy itself. You can generate electricity from many things, including fuel, and there are many forms of chemical devices with electrical potential energy - we usually call them batteries - but electricity is not, itself, fuel. Now, the energy still needs to come from somewhere (unless this drive does turn out to be usable to get more energy out than is put in, which would turn *all* of physics on its head) and that "somewhere" is usually fuel of some kind... but it can be things like uranium in a nuclear reactor that is usable for decades from a tiny amount of mass, or hydrogen in the sun producing photons as it fuses and those photons being captured and used to move electrons via the photoelectric effect (in layman's terms, solar panels).
Re: (Score:3)
I know this is Slashdot, but the abstracter of the paper is pretty clear:
"Our test campaign can not confirm or refute the claims of the EMDrive"
http://arc.aiaa.org/doi/10.251... [aiaa.org]
How did we get from that to the summary posted here? Why does the happen every single time an article about this appears on Slashdot?
Because that's what clickbait [reference.com] is all about!
Re:Just test it in space already (Score:4, Funny)