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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 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.
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
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.
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.
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
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.