Slashdot Mirror
Thrust from Microwaves - The Relativity Drive
dfenstrate writes "The latest New Scientist has an article about an engine that exploits relativity and microwaves to generate thrust. There is a working prototype." From the article: "Roger Shawyer has developed an engine with no moving parts that he believes can replace rockets and make trains, planes and automobiles obsolete ... The device that has sparked their interest is an engine that generates thrust purely from electromagnetic radiation — microwaves to be precise — by exploiting the strange properties of relativity. It has no moving parts, and releases no exhaust or noxious emissions. Potentially, it could pack the punch of a rocket in a box the size of a suitcase. It could one day replace the engines on almost any spacecraft. More advanced versions might allow cars to lift from the ground and hover."
"The latest New Scientist has an article about an engine that exploits relativity and microwaves to generate thrust.
That sounds a bit more advanced than these two guys, who exploit explosives and a microwave to generate thrust.
The theory of relativity doesn't work right in Arkansas.
It also warms soup, and is great for reheating food.
Roger Shawyer has developed an engine with no moving parts that he believes can replace rockets and make trains, planes and automobiles obsolete ... The device that has sparked their interest is an engine that generates thrust purely from electromagnetic radiation
Of course, his first effort was to create a drive that ran purely on improbability, but you could never be sure where you'd end up or even what species you'd be when you get there.
The theory of relativity doesn't work right in Arkansas.
Seriously, we were supposed to have these things *years* ago. The scientific community should be ashamed of themselves.
( yes, this is a joke )
Mod me down with all of your hatred and your journey towards the dark side will be complete!
The complete and utter bogosity of this story has prompted Greg Egan to try to start a movement to save New Scientist. Anyway, check out this story.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
I think you're forgetting that it involves relativity, therefore doesn't need to make sense. Plus I seem to remember that conservation of momentum was a by product of that 4-vector thing, so maybe something funny happens. Maybe.
"In this house we obey the Laws of Conservation of Momentum!"
you can have it for free:
</i>
If you don't know what AltaVista is (was), get off my lawn.
Because that would be a photon drive. And we already know how well those work - the amount of energy you need to input to get even a tiny amount of thrust out of them is astronomical (pun not intended). We've had the basic idea of light propulsion for at least fifty years, and it's been a major cornerstone of hard science fiction. But it just isn't workable with modern power generation.
You could describe either a photon drive, or it's passive counterpart, the light sail, as a "relativity drive", since they too operate on the oddities of conservation of momentum as it applies to light. Doesn't mean we're going to be using them in lieu of rockets anytime in the next few centuries.
Either this guy has found a revolutionary new way to build a photon drive (and I'm more than a little skeptical), or else the device doesn't actually work. I'm more optimistic about this than I am about the usual lot of crackpot science, since from TFA it sounds like this guy is applying good scientific procedures to his work (documenting, trying to get outside review), but I'm not exactly holding my breath.
Erotic is when you use a feather. Exotic is when you use the whole chicken.
Comment removed based on user account deletion
The benefit of the multiple bounces is that they never leave the chamber. The chamber is shaped like a horn, and he's claiming that the force on the big part of the horn is greater than the forces towards the little side of the horn. An imbalanced force inside the chamber result in a net force from a closed system. Plus side, no moving parts and sealed. Minus side, current physics indicate this to be impossible. I know of no theory, even including the magical "relativistic" physics that allow for or predict unbalanced forces in a closed system. I'll believe it when I see it demonstrated to move a satellite in space. If he can do that, I'll drink the cool-aid.
Learn to love Alaska
I hope his invention is better than his explanations for why he has no investors (I know, I know, it's not).
"'Yrch!' said Legolas, falling into his own tongue."
Now I can have what I've always dreamed of, a flying car with a Phantom game console running Duke Nuke'em Forever on HURD with Copland running in virtualization on a BitBoys Oy Glaze3D graphics system whose driver was programmed in Perl 6 running on top of Parrot!
I love it when dreams come true.
I'm rolling on the floor laughing at that article, but have to remind myself that it's probably an ignorant reporter and (not necessarily) Shawyer.
"Since the microwave photons in the waveguide are travelling close to the speed of light"... no, the microwave photons ARE light and are, by definition, moving at the speed of light at that point. I'm not really weaseling -- 'c' is the speed of light in open vacuum and is the same thing for all photons, but a waveguide is only a few multiples of the photon's wavelength and various weird things (to us) happen. See also the (Shamir?) pressure you can get when you hold two conductive plates close together. Longer wavelengths can't exist between the plates but can exist outside of them so you get a very slight net force pushing the plates together.
"any attempt to resolve the forces they generate must take account of Einstein's special theory of relativity."... no, standard EM theory will suffice. (Well, you might need some QM in there, but definitely not special relativity.)
and my favorite
"by mounting it on a sensitive balance, he has shown that it generates about 16 millinewtons of thrust, using 1 kilowatt of electrical power."
Let that sink in. This is as much power as a hair dryer or stove element, and it generates 16 mN of thrust. Could it be, oh, Satan?! I mean, thermal?!
This is particularly ironic since the article referred to the discovery of light pressure earlier. Everyone knows those little bulbs with white and black fans that "demonstrate" this effect. What most people don't know is that it isn't a perfect vacuum in there and, gosh, the dark side gets slightly hotter than the white side. That means the gas heats up on one side, expanding, you know the rest. IIRC they spin leading with the white side. It should be the other way since you have twice as much momentum transfer to reflect light (white) than to simply absorb it (black).
(BTW, I agree 100% with everyone who's pointing out that the walls of the cavity account for the rest of 'thrust' and that the device will just sit there driving up your power bill.)
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
Tue Sep 19 17:56:42 PDT 2006
Russell McMahon wrote:
I don't know that a reactionless drive can't work - although I don't know how to build one
Without having gone into it in detail, his math seems okay up to eq 6 (when he is quoting well-known math), but thereafter he veers into the realms of error and fantasy.
Eqation 7 is incorrect in so far as it purports to describe the total forces on the waveguide - while it does correctly describe the sum of the forces on the ends of the waveguide, it does not take into account the forces produced on the sides of the tapered waveguide.*
All by itself that is enough to blow the conclusions of the paper completely out of the water. It is simply wrong. It doesn't work. You can stop reading here.
Now we get into the rather more dubious portion of the paper.
Eq. 8 is also in error - it is based on the incorrect statement "...as the two forces Fg1 and Fg2 are dependent upon the velocities vg1 and vg2, the thrust T should be calculated according to Einsteins law of addition of velocities." - but the conclusion does not follow, and use of Einstein's equation is inappropriate. There is no real-world summing of velocities, it is a mathematical trick (and there is an error int the math too). The ends of the waveguide are stationary relative to each other.
That is an elementary schoolboy (or snake-oil salesman's) mistake.
There are several other obvious mistakes in the paper, and he frequently states as fact things that are unjustified and on occasion untrue. There are also parts of it which seem to be meaningless.
For example, this is also incorrect: "The second effect is that as the beam velocities are not directly dependent on any velocity of the waveguide, the beam and waveguide form an open system."
The conclusion does not follow.
This is actually very confused - I don't think he even knows what he is saying. Relativity theory does not (directly) come into it at all.
I stopped looking for more errors about here.
Snake oil or error?
There was some mention of licencing the technology, but as it is in the UK patenting it here would be impossible - it is, after all, a perpetual motion machine (or it would be if Q approached infinity, which there seems no theoretical reason to suppose impossible), and you cannot patent a perpetual motion machine in the UK.
Even if it worked.
The question of how he got a grant is still
To the DTI, NASA etc: Please can I have half his grant for pointing out his mistakes? I promise I will use it do space r+d.
*Of course if you want to consider the waveguide as two pieces, forces on the tapered walls do not affect the result - but the math in eq7 would be wrong if you are looking at it that way, eg the lambda-g1 and lambda_g2 figures are for the ends of the waveguide, not the middle.
I think he first went wrong in his mind here - in fig 2.4 there is a vertical line in the middle of the diagram, implying that he was looking at the waveguide as two pieces, rather than as two ends and a tapered middle. You can of course look at it in either way, but in his analysis (even before we get into the error-full "relativity" stuff) he is trying to do both at once, and that will and has lead to error.
--
Peter Fairbrother
--a different AC
By the way, this engine would violate conservation of momentum, and is thus incredibly dubious. On top of that, the "working" prototype was measured to generate an incredibly tiny force, a measurement which was given without error bars in the only numbers I've seen, so he's probably just measured his noise floor. It has never been published in a peer reviewed journal. Because of this article, John Baez has posted an open letter from Greg Egan to the editors of New Scientist, which includes gems like "I really was gobsmacked by the level of scientific illiteracy in the article".
In other words, reader beware. Crackpots abound.
I'm very surprised that this is being reported on. There's nothing to this.
What's probably happening is that the microwaves are leaking out heating up one side of the thruster more than the other causing the air on that side to warm up and become bouyant which is whats creating the apparent thrust. I could make a lot more thrust with a 700 Watt fan than 88 millinewtons.
I'm starting to dispair over the state of science in this so called modern world when I see articles like this. Maybe next we could have an argument over whether sidereal or tropical based astrology is more accurate at predicting the future.
It was a really bad article. It was clearly a dodgy claim and you would think they would have an expert in the area totally vet the article, but alas no.
/ YaBB.pl?num=1157719780/0)
There are some other worrying things in the article. For example, the author says...
What of the impact of such a device? On my journey home I have plenty of time to speculate. No need for wheels, no friction.
Yet it is precisely the friction between the wheels and road which make a car go forward. Friction with the car wheels is not bad, you need it. Friction with the air is bad, but not the wheels.
If I had do the EM Drive story, a story which sounds highly suspect, I would have looked at some critiques of similar schemes. Within a few minutes of searching I found similar "Reaction-less Drive" schemes which all turned out to be Oscillation drives. It's the same phenomena as when you move across the room in a swivel chair (without touching the floor) by shifting your body-weight around. When you do that you are exploiting the non-linear nature of friction between surfaces. A similar thing can happen with these reaction-less drives interacting with air, water or other surfaces. So it's quite possible that a prototype drive would appear to work. So I would have asked for some kind of proof that this was not an oscillation drive.
Another issue is that it's not clear that this Em Drive prototype has been tested in a vacuum. In one of the other articles on it, it says that the thrust only reaches the maximum after a few seconds. Now that sounds much more like a mechanical oscillation effect (building up to maximum amplitude) than a photon/microwave effect.
Some of what I have said here is re-posted from a discussion I had on the Elmurst Solutions Science forums. (http://www.elmhurstsolutions.co.uk/cgi-bin/yabb2
Assuming that part of TFA is true, then he's already way ahead of the usual "free energy" crowds.
Typically when somebody's claims violate the laws of physics, the usual challenge is for them to provide a repeatable experiment for others to test the theory in question with. This challenge is most often met with weaseling or silence. When such theories are tested from outside, they most often do not pan out (see the cold fusion experiments as an example).
If he's willing to get outside review already, then I at least will acknowledge that he is an honest crackpot rather than a snake oil salesmen. And it's always better to actually test the blue sky ideas than it is to dismiss them out of hand.
Erotic is when you use a feather. Exotic is when you use the whole chicken.
It's possible that it's covered more accurately in his paper, I haven't got around to reading that yet, but TFA is certainly not the place to go for a serious treatment of this information.
Yes, that's the part where you should finally realize the whole thing is nothing but bullshit.
He's claiming that the effect depends on the absolute velocity of the engine - a concept that has been meaningless ever since we did away with the coelestial aether and Maxwellian electrodynamics.
He's not using relativity, he's using the exact opposite.
It is, in fact, possible to this Bugs Bunny trick, but by positioning the fan airflow perpendicular to the keel, then setting sail plane oblique to the airflow. It is somewhat similar to sailing against the wind
It is also possible to accelerate a rocket by shining a beam of light off it...
While in both cases there are much better ways to achieve same result, these will certainly work.
Obama likes poor people so much, he wants to make more of them.
Yet it is precisely the friction between the wheels and road which make a car go forward. Friction with the car wheels is not bad, you need it. Friction with the air is bad, but not the wheels.
I thought it was the exhaust coming out of the back that propelled the car forward.. I mean, if electromagnetic radiation can propel something forward surely gaseos exhaust can?
// MD_Update(&m,buf,j);
If he's willing to get outside review already, then I at least will acknowledge that he is an honest crackpot rather than a snake oil salesmen. And it's always better to actually test the blue sky ideas than it is to dismiss them out of hand.
Oh, there have been any number of people who have put forward various intertialess drives for independant review. You are right, there is a difference between the honest crackpot and the snake oil salesman (thank god, or I might be in real trouble myself), but sometimes tests actually just waste time and resources when the theoretical failures can be defined without actual test.
And my point was that he hasn't actually built anything legitimately testable in a lab yet. The forces are so small that we'll need to fly the puppy to judge it at all. This is different from the solar sail which already know could work by theory and ground based test.
I can build you three or four mechanical variations on the theme that will even stand up to review in the sense that they seem to work perfectly well in the lab, much better than this one does because they'll actually scoot across the airtable, but the reason why they won't work in space are well enough understood that no one is going to waste a bird to send one up.
It's perfectly possible to become an honest crackpot by simply getting a bit of the equations wrong and have that failure perfectly obvious to other people.
KFG
Comment removed based on user account deletion
But, he does claim to have a working prototype, and it will be interesting to see if anything does come of it. I've been known to be wrong in the past, after all.
A photon's own reference frame? I didn't think you could consider things from the perspective of a photon and still achieve physical results. In a photon's frame of reference, it and all other photons would constantly be at rest, since they all move at the same speed. That doesn't make any sense, though, since photons always travel at the speed of light and can never rest.
Is anyone else reminded...of those cartoons where Bugs Bunny or someone is sitting in a sailboat, pulls out a fan, aims it at the sail... ...and the boat moves?
That actually works. A little bit.
But it works MUCH BETTER if you just point the fan to the rear.
The fan sucks air from a lot of directions and ejects it in one direction, creating a net thrust (and reaction - backward - on the boat via the person holding the fan) and a net wind.
Diverting that wind to the rear via the sail produces somewhat more reaction forward on the boat via the sail and the mast than the reaction backward from the fan - IF the trim is good enough that the diverted wind ends up going backward rather than just off to the sides. Result: Slight net forward thrust on the boat.
But pointing the fan to the rear - using it as a jet - eliminates the inefficiencies of using the sail in this way, putting the fan's whole reaction into moving the boat forward.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
He then proceeds to derive a maximum speed this engine can attain, relative to this arbitrary stationary frame, to illustrate the consequences of this idea. He has, as far as I can see, recreated the ether in his attempt to justify the machine using relativity.
Um, I have to ask. What about the air being deflected off the fan? Doesn't it create thrust in the opposite direction from the sail? In fact, I'd expect the boat to move backward, because most of the air from the fan would disperse and not hit the sail.
Currently hooked on AMP
The radiation pressure does exist, but it has nothing to do with Lorentz force. And you can, actually, propel yourself by shining a flashlight away from you. The matter annihilation engines work on this principle, for some decades by now.
The only problem with this propulsion method is that you need an awful number of photons, and you wouldn't like to be in a spot that they hit. Some writers theorized that the Solar system would need an energy shield before it can launch a photon-driven starship from anywhere close to it.
If there is a sustained, measurable deviation not explained by known physics, the guy will get a Nobel. That's 1.1 million dollars. If I was sure I had a winner for getting a million, I'd certainly be ready to invest into a vaccum chamber and build a prototype.
If we don't see this happen, then the drive doesn't work. End of story.
--
Mad science! Robots! Underwear! Cute girls! Full comic online! http://www.girlgeniusonline.com/
The only problem with this propulsion method is that you need an awful number of photons...
Hmmm, I'd always thought the major problem with matter-annihilation drives was the lack of antimatter deposits in the Earth's crust from which the fuel could be mined...
But what really got me fuming wasn't the author's total failure to notice that any of these were an issue - which I'll grant got me quite livid, being as bad as a football report from someone who doesn't know the offside rule. That it violates basic physics is bad, and should certainly have been seriously raised as an issue in the article, but if it works then that's just too bad for basic physics.
What upset me most of all was the lack of imagination. What if this thing works as advertised? Oh, then we can have planes that work a bit differently. Hovercars, perhaps. For the love of God, man, it's a reactionless drive! Strap a few to a nuclear reactor and go to Saturn and back in a week! A rocket that doesn't have to carry vast tanks of reaction mass around with it? The whole galaxy would open up!
I'll buy this week's New Scientist in the hope of some sort of grovelling apology for this appalling mess of an article. Or at least of a proper flaming of the editors in the letters pages. And then I think I'll see if I can't get a reliable supply of Scientific American - it's quite scarce in UK newsagents but always has some really solid science in it.
Real Daleks don't climb stairs - they level the building.