Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Thrust from Microwaves - The Relativity Drive

Zonk posted more than 8 years ago | from the yay-for-science dept.

567

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."

Sorry! There are no comments related to the filter you selected.

a bit more advanced (5, Funny)

User 956 (568564) | more than 8 years ago | (#16164200)

"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 [youtube.com] , who exploit explosives and a microwave to generate thrust.

Re:a bit more advanced (1)

Tibor the Hun (143056) | more than 8 years ago | (#16164256)

It's great to see douches like that play with fireworks. I like to watch their pictures on ogrish.

Apparently they've never heard of remote detonators, or slow burning fuses...

Forgetting some things? (2, Insightful)

qbwiz (87077) | more than 8 years ago | (#16164202)

A) Any pressure from the microwaves on the walls.
and
B) Conservation of Momentum

Re:Forgetting some things? (5, Funny)

jonnyelectronic (938904) | more than 8 years ago | (#16164222)

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.

Re:Forgetting some things? (1)

Jack Pallance (998237) | more than 8 years ago | (#16164245)

What do you expect from a Rocket made by "HungryMan?"

Is anyone else reminded... (2, Insightful)

Kelson (129150) | more than 8 years ago | (#16164291)

...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?

Re:Is anyone else reminded... (0)

lelitsch (31136) | more than 8 years ago | (#16164433)

Joke well taken, but aiming a fan at a sail from the deck would actually work. The air gets deflected backwards by the sail creating thrust which propels the boat forward. The inertia--ok, it's Bugs Bunny, so lets call it recoil--from the fan goes into a closed system as long as Bugs doesn't fall of the bench or the boat gets pulled apart. For a non-cartoon, real world application, see thrust vectoring [wikipedia.org] .

The article is still fairly obvious nonsense. Obvious enough that New Scientist should have caught this very early in the editing process.

Re:Forgetting some things? (1)

bunions (970377) | more than 8 years ago | (#16164313)

it's addressed in TFA, if you'd care to read it.

Re:Forgetting some things? (1)

kfg (145172) | more than 8 years ago | (#16164320)

He notes as a 'problem to be solved' the fact that the faster the engine goes, the less thrust it produces. He also notes how essentially useless this would make the engine for propeling a car, positing only that it could be used make the vehicle hover so a fan could drive it -- so much for the "no moving parts" part. You'll need a conventional motor of some type anyway; and a power source.

He might also be neglecting the reasons why we don't all drive around in hovercraft today. It's a perfectly viable current technology already and fun to play with, but there are some real advantages in being rooted to the ground for ground travel.

KFG

Isn't that every engine? (0)

khasim (1285) | more than 8 years ago | (#16164341)

He notes as a 'problem to be solved' the fact that the faster the engine goes, the less thrust it produces.

Isn't that the same for every rocket engine? If you burn one unit of fuel to get 1/2 light speed, burning a second unit of fuel will not get you to lightspeed.

Re:Isn't that every engine? (2, Informative)

kfg (145172) | more than 8 years ago | (#16164424)

You are confusing nonlinearity of acceleration at a given thrust with nonlinearity of the thrust itself.

As a visceral example go ride a bicycle through air. Doubling your thrust will not double your speed, but you will experience directly that you have, indeed, doubled your thrust.

In the best case scenario, i.e. if this guy can solve the little problems such as pressure on the chamber walls, his engine, by his own calculations, does not simply run with nonlinear acceleration with a given thrust, but actually "runs out of juice."

In the colloquial, it stops working.

KFG

Re:Forgetting some things? (2, Interesting)

Pictish Prince (988570) | more than 8 years ago | (#16164435)

Seems to me you only need to incorporate this idea [slashdot.org] to reduce the inertial mass of the craft and then your radiation pressure can really make things happen. You then have... a flying saucer.

Re:Forgetting some things? (1)

codetwice (980018) | more than 8 years ago | (#16164444)

Good point on A)
There is thrust created when the ray bounces on the sides. Looking at the original diagram found in the published PDF, you can easily see that the thrust towards the narrow end created on the sides while the ray is traveling towards the narrow end is bigger than on the way back. I think these side force differences completely equalize the thrust gain you see on the main walls.
As for point B, I dont believe in conservation of momentum when it comes to photons and relativistic effects like frame of reference, constant c, time diletation and energy-dependent mass.

Aditional Features (5, Funny)

celardore (844933) | more than 8 years ago | (#16164212)

It also warms soup, and is great for reheating food.

Re:Aditional Features (1)

From A Far Away Land (930780) | more than 8 years ago | (#16164232)

"It also warms soup, and is great for reheating food."

Big deal, people have been cooking on the manifold of combustion engines for years now. ;-)

Re:Aditional Features (2, Funny)

ackthpt (218170) | more than 8 years ago | (#16164278)

It also warms soup, and is great for reheating food.

Yep. "To the moon, Alice, and don't spare the popcorn!"

Re:Aditional Features (0)

Anonymous Coward | more than 8 years ago | (#16164368)

warming soup IS reheating food

Re:Aditional Features (0)

Anonymous Coward | more than 8 years ago | (#16164380)

I was going to ask whether or not this device could cook my Ramen... I suppose if I set it under my hovercar for a few seconds...

Re:Aditional Features (1)

stefanlasiewski (63134) | more than 8 years ago | (#16164437)

It also detects missiles which are approaching you from behind, communicates with bluetooth devices and generates plasma for semiconductor etch-a-sketch devices--- and it's a floor wax, gargle and a hair tonic (You can feel the tingle)!

Will wonders never cease?

attempt #2 (5, Funny)

User 956 (568564) | more than 8 years ago | (#16164216)

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.

'bout damn time I get my flying cars (4, Funny)

grasshoppa (657393) | more than 8 years ago | (#16164218)

Seriously, we were supposed to have these things *years* ago. The scientific community should be ashamed of themselves.

( yes, this is a joke )

Re:'bout damn time I get my flying cars (1)

LunaticTippy (872397) | more than 8 years ago | (#16164241)

They've had flying cars [strangebirds.com] since the 50s.

Re:'bout damn time I get my flying cars (5, Insightful)

Azarael (896715) | more than 8 years ago | (#16164299)

Joke well taken, but in all honesty the bigger joke is that we technically could have had flying cars already. You know what the problem is? the general public couldn't be trusted not to crash the things left and right. In no time there would be more flying lawsuits than cars.

Easy solution (0)

Anonymous Coward | more than 8 years ago | (#16164338)

In no time there would be more flying lawsuits than cars.

Use really dark window tinting and dont' put your real license plate on the flying car! Also, use that rubbery bouncy paint.

Re:Easy solution (1)

rahrens (939941) | more than 8 years ago | (#16164472)

"rubbery bouncy paint"

Is that a technical term?

Re:'bout damn time I get my flying cars (2, Insightful)

Total_Wimp (564548) | more than 8 years ago | (#16164406)

Joke well taken, but in all honesty the bigger joke is that we technically could have had flying cars already. You know what the problem is? the general public couldn't be trusted not to crash the things left and right. In no time there would be more flying lawsuits than cars.
And exactly how is this different from cars with wheels?

TW

Re:'bout damn time I get my flying cars (5, Insightful)

Azarael (896715) | more than 8 years ago | (#16164443)

It's a bit harder to drive your car into the side of a highrise buidling.

Re:'bout damn time I get my flying cars (1)

jcr (53032) | more than 8 years ago | (#16164438)

we technically could have had flying cars already. You know what the problem is? the general public couldn't be trusted not to crash the things left and right. In no time there would be more flying lawsuits than cars.

This is true, but the solution is rapidly approaching, now that we have GPS and automated flight controls. When we have air cars that are fully capable of taking off, navigating and landing unattended (that is, an aircraft that a child or a drunk could safely use), then we'll see them move from being Moller's fantasies to products you can buy.

-jcr

Re:'bout damn time I get my flying cars (2, Insightful)

Pictish Prince (988570) | more than 8 years ago | (#16164463)

In no time there would be more flying lawsuits than cars.
Simple. Just shoot all the lawyers first and let natural selection have its day.

Re:'bout damn time I get my flying cars (1)

texaport (600120) | more than 8 years ago | (#16164394)

we were supposed to have these things *years* ago

When I read the part where it "can replace rockets and make trains, planes and automobiles obsolete" I also thought it is about damn time for something new. (I'm in the 35-44 demographic group)

My grandmother never drove a car, my grandfather didn't live to see rockets with chimps inside, my parents have never been on a plane, and I doubt my own kids will ever take a trip on an Amtrak train.

Save New Scientist! (5, Informative)

exp(pi*sqrt(163)) (613870) | more than 8 years ago | (#16164221)

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 [utexas.edu] story.

Re:Save New Scientist! (4, Insightful)

Morphine007 (207082) | more than 8 years ago | (#16164269)

It does seem rather bogus

His references include an undergrad level textbook on physics, as opposed to the usual slew of papers outlining new developments in the field. Undergrad physics books are geared towards undergrad courses... which is why you see things like: "assume no friction due to air" in trajectory problems. His second reference is Maxwell's treaty on electricity and magnetism... hardly a new work.

In short, odds are he picked up a textbook and started playing with simplified equations and figures he's made a "discovery" that no one else has noticed until now.... HUGE HUGE Kudos if it's true.... but the magic 8-ball's sayin "outcome not likely"

Re:Save New Scientist! (2, Insightful)

exp(pi*sqrt(163)) (613870) | more than 8 years ago | (#16164416)

odds are he picked up a textbook and...made a "discovery" that no one else has noticed until now.... HUGE HUGE Kudos if it's true.
It's not just unlikely, it's impossible. It's impossible to derive something that doesn't conserve energy and momentum from things like Maxwell's equations because the theory is an energy-conserving one. It may be that one day someone makes a drive like this using electromagnetism - but if they do, its principles won't be derived from Maxwell's equations, it'll have to utilize some completely new physics.

Re:Save New Scientist! (1)

QuantumG (50515) | more than 8 years ago | (#16164469)

Why does everyone keep saying this doesn't conserve energy and momentum? He's got mains power hooked up to a magnatron, he's expending a whole lot of energy and (he claims) he's getting a tiny output of momentum.

Re:Save New Scientist! (1)

Goaway (82658) | more than 8 years ago | (#16164434)

If you take the time to read through the article, you will find gems like:

Then there is the issue of acceleration. Shawyer has calculated that as soon as the thruster starts to move, it will use up energy stored in the cavity, draining energy faster than it can be replaced. So while the thrust of a motionless emdrive is high, the faster the engine moves, the more the thrust falls. Shawyer now reckons the emdrive will be better suited to powering vehicles that hover rather than accelerate rapidly.

That show the inventor is nowhere near understanding even special relativity, and is still stuck with Maxwell and the coelestial æther.

Re:Save New Scientist! (1)

tloh (451585) | more than 8 years ago | (#16164459)

don't forget:

Since the microwave photons in the waveguide are travelling close to the speed of light, .... (emphasis mine)

Re:Save New Scientist! (1)

SQL Error (16383) | more than 8 years ago | (#16164336)

It's about time. New Scientist started to go of the rails ten years ago, and has just been accelerating since then.

Save New Scientist from what, exactly? (0)

Anonymous Coward | more than 8 years ago | (#16164386)

It's always been a pseudo-scientific journal.

Perhaps we can save it from itself, and recreate it as something which doesn't promote every crank making metaphysical claims.

From the aRocket list... (1, Informative)

Anonymous Coward | more than 8 years ago | (#16164224)

Interesting post from the aRocket list, that basically blows up this guy's argument. At least, this guy SOUNDS like he knows what he's talking about... Peter Fairbrother zenadsl6186 at zen.co.uk Tue Sep 19 17:56:42 PDT 2006 Russell McMahon wrote: > As already noted on ARocket - it "*can't* work - but wouldn't it be nice if he > was right, even though he's not :-(. I don't know that a reactionless drive can't work - although I don't know how to build one :( - but I do know that this particular one doesn't work. > For those who haven't met the emdrive before - it's not your usual snake oil > and mirrors type device - the inventor is highly capable and has convinced a > number of substantial organisations, including the US Air Force, British Govt > research granters and NASA to be cautiously interested. All of which just > means that it's not yet obvious to all where the hole in his theory is. > 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 ... puzzling, but not totally unexpected. Grants are often assigned by managers and politicians rather than scientists or engineers. 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

Re:From the aRocket list... (0)

Anonymous Coward | more than 8 years ago | (#16164267)

Good god, man!

Paragraphs!

Use paragraphs!

The aRocket post with paragraphs... (5, Informative)

Anonymous Coward | more than 8 years ago | (#16164354)

Peter Fairbrother zenadsl6186 at zen.co.uk
Tue Sep 19 17:56:42 PDT 2006

Russell McMahon wrote:

As already noted on ARocket - it "*can't* work - but wouldn't it be nice if he was right, even though he's not :-(.

I don't know that a reactionless drive can't work - although I don't know how to build one :( - but I do know that this particular one doesn't work.

For those who haven't met the emdrive before - it's not your usual snake oil and mirrors type device - the inventor is highly capable and has convinced a number of substantial organisations, including the US Air Force, British Govt research granters and NASA to be cautiously interested. All of which just means that it's not yet obvious to all where the hole in his theory is.

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 ... puzzling, but not totally unexpected. Grants are often assigned by managers and politicians rather than scientists or engineers.

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

Re:The aRocket post with paragraphs... (0)

Anonymous Coward | more than 8 years ago | (#16164452)

Thank anonymous coward - the parent should be modded 'not anal enough to post on slashdot' :)
I nearly made your post myself!

Junk (1, Interesting)

Anonymous Coward | more than 8 years ago | (#16164225)

Slashdot never loses its appetite for junk science, it seems. Couldn't we at least file this crap under "humor"?

Re:Junk (1)

Kelson (129150) | more than 8 years ago | (#16164318)

Slashdot never loses its appetite for junk science, it seems.

"Junk Science!
How come you taste so good?"

Oblig comment (5, Funny)

QuantumFTL (197300) | more than 8 years ago | (#16164226)

"In this house we obey the Laws of Conservation of Momentum!"

Re:Oblig comment - RTFA (0)

Anonymous Coward | more than 8 years ago | (#16164446)

RTFA

Erm... I don't get it. (2, Interesting)

TheSHAD0W (258774) | more than 8 years ago | (#16164228)

What's the difference between letting the microwaves bounce around in a cavity and just shooting them out the back? Or if you must bounce them, just bounce them off a 45 degree reflector. What's the benefit of the multiple bounces?

Re:Erm... I don't get it. (4, Interesting)

RsG (809189) | more than 8 years ago | (#16164284)

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.

Re:Erm... I don't get it. (1)

kfg (145172) | more than 8 years ago | (#16164350)

. . .from TFA it sounds like this guy is applying good scientific procedures to his work. . .

The proof that his working model, well, works, are measurements taken at the limit of the ability to measure the effect. This is not good scientific procedure. You are right not to hold your breath.

KFG

Re:Erm... I don't get it. (4, Insightful)

RsG (809189) | more than 8 years ago | (#16164432)

I actually meant more that he was trying to get his idea reviewed from the outside, something the vast majority of crackpots fail to do.

One of the conditions of Shawyer's £250,000 funding from the UK's Department of Trade and Industry is that his research be independently reviewed, and he has been meticulous in cataloguing his work
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.

it's just a less efficient photon drive (1)

rubycodez (864176) | more than 8 years ago | (#16164421)

but that's the point, anything that spits out photons (microwave or any other frequency), can only be a photon drive, and bouncing the photons internally accomplishes absolutely nothing, it doesn't make more microwaves nor does it increase microwave energy (and I'd like to poke the writer of that article in the eyes just for speaking of near-light speed of microwaves). In short, this "invention" is a load of crap and a waste of time based on a lack of understanding of EM.

Re:Erm... I don't get it. (4, Informative)

AK Marc (707885) | more than 8 years ago | (#16164296)

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.

Re:Erm... I don't get it. (1)

jcr (53032) | more than 8 years ago | (#16164457)

I would have to surmise that whatever thrust he gets against the wide end will be offset against the force not only on the narrow end, but also against the oblique walls of the chamber!

-jcr

Re:Erm... I don't get it. (1)

Vandilizer (201798) | more than 8 years ago | (#16164360)

Simple example

Case 1: (Ion engine)

If you tossed something where there is no gravity (space) and it is a vacuum (you have nothing to push against (the earth)) you will gain the momentum that the object you tossed gained. (Conservation of energy thought you might have lost some due to the effort of the toss.)

Case 2: (This engine)
If you now build a box in space and toss something inside of it (dose not mater if it is a vacuum or not) you are going to go one way and the object is going to go the other. Now you will both hit the walls and transfer some energy to the box and you will probably bounce around a bit to. The thing is the over all energy transferred is zero. The box will vibrate, but will not really go anywhere.

So what dose this mean? For you to gain momentum you must expel something in the opposite direction you want to go. Rocks and jets don't push they throw partials out.

Now yes there will be heat lose and other energy but in these cases that is negotiable though in this engine could make a difference (heat is just another form of radiation). So assuming that the microwaves end up as heat and all that goes out the wide end of the tube instead of randomly dispersed. It could work.

This is the best I can do with out giving math examples if someone can do better please do.

Sorry I did not answer your question I just ended up saying that the bouncing should cause the engine not to work. Hummm... Oh well...

If I managed to figure out something like this.. (2, Funny)

QuantumG (50515) | more than 8 years ago | (#16164240)

I wouldn't tell anyone. I'd maybe show a few keen investors what my prototype could do, but that's it. Then I'd develop a flying car, a launch vehicle, whatever, and insidiously take over existing markets. "So, SpaceX has made you the best offer for launch services eh? I'll beat it." "What kind of safety guarentees can you give us?" "Err, umm, what kind of safety guarentee is SpaceX giving you, I'll beat it!" "Right.. hmm, ok. You don't even have a rocket do you?" "Look, do you want your satelite in orbit or what?" and so on. That's me though, could be this guy just doesn't have balls that big.

Re:If I managed to figure out something like this. (2)

Nephilium (684559) | more than 8 years ago | (#16164376)

I'm pretty sure that the Phantom gaming console has that business model patented...

Nephilium

It's not enough to be able to pick up a sword. You have to know which end to poke into the enemy. -- (Terry Pratchett, Lords and Ladies)

Uhhhh (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#16164243)

make trains, planes and automobiles obsolete ...

How about them Bears?

Dangerous? (1)

ultracool (883965) | more than 8 years ago | (#16164251)

More advanced versions might allow cars to lift from the ground and hover. Correct me if I'm wrong, but aren't microwaves dangerous? In space, hardly anyone is around so blasting microwaves all over the place doesn't hurt anyone, but on a crowded street, wouldn't it harm people?

here you go (4, Funny)

Tibor the Hun (143056) | more than 8 years ago | (#16164277)

you can have it for free:
</i>

Re:Dangerous? (0)

Anonymous Coward | more than 8 years ago | (#16164342)

Microwaves are relatively low-frequency (thus low-energy) radiation (just below infrared in the energy scale). The main issue is that these energy levels are close to the rotational and vibrational frequencies of many molecules (i.e. they can heat matter). Incidentally, that's why you can heat or cook food in a microwave, and also why being exposed to large amounts of microwave radiation can damage your body tissues.

Re:Dangerous? (0)

Anonymous Coward | more than 8 years ago | (#16164445)

Not dangerous, if you WANT to be cooked. Most people do, believe it or not, because we constantly keep putting these little things up to our ears (cel phones).

That's not a piece of string they're carrying their signals on, ya know...

Key points from TFA (2, Interesting)

PatrickThomson (712694) | more than 8 years ago | (#16164257)

Buried right at the end, it says that if the engine is allowed to actually accelerate, it consumes energy from the cavity, so this is NOT a perpetual motion device or some other bollocks. You can't get out more kinetic energy than the cost you put in - at best, this would be like using momentum from laser light.


However, it talks about hovering. There's nothing intrinsically unscientifically sound about two black boxes that exert a force on each other despite being physically disconnected (think maglev), effectively hovering one on the other - the transmission of force just doesn't happen via a physical carrier. I, for one, look forward to my hoverboard.

Re:Key points from TFA (2, Insightful)

RsG (809189) | more than 8 years ago | (#16164392)

I don't think anyone who read TFA assumed this was perpetual motion. What this claims to be is more of a reactionless thruster - a different beast. It's quite possible to put forward a theory that violates conservation of momentum without violating conservation of energy.

Now, admittedly, one is as much in violation of the laws of physics as the other. We have no theoretical basis for reactionless propulsion. In the case of two black boxes acting on each other without being physically connected, the laws of reaction still apply (ie, you can apply force to a maglev train and have it carry over to the rail, despite the fact they never come into contact with each other). I'm not sure how this hypothetical drive could hover without repelling the ground in some way.

Side note - as I mentioned in another post, we've known how to extract momentum from laser light for decades. Light sails and photon drives, both found in sci-fi and both supported by the laws of physics, use exactly that very principle. But the characteristics of these propulsion systems is nothing like what's described in TFA. Either this guy has found something new, or he's made a mistake. I would not give very good odds on the former, sadly.

The maths paper please (2, Informative)

Anonymous Coward | more than 8 years ago | (#16164259)

Would somebody please just go right ahead and post a scanned copy of Roger Shawyer's maths paper online after tracking him down and ordering the paper version from him? He says he has a maths paper, so let's cut out these waffling, nonsensically hand-waving explanations much loved by New Scientist that "relativity somehow causes microwaves to create thrust but we don't really know how it works but it does because I say so" and see the maths paper. Show us the maths and it will quickly become apparent whether he is a quack or a clever guy deliberately being a honeypot taggant for Chinese military procurement folks.

Re:The maths paper please (2, Informative)

helioquake (841463) | more than 8 years ago | (#16164382)

It's an interesting reading here:

  http://www.newscientist.com/data/images/ns/av/shaw yertheory.pdf [newscientist.com]

the link is provided by the article linked. It sounds interesting to me, though referring to the special "relativity" is a bit too much; basically one end of the tubes experience more normal force than the other (narrow end) would result in a net forward force, which drives the system.

Of course the key is the generation of the cavity and its material, and the magentron design.

Nontheless, it sounds interesting to me. Not an expert on these systems, though.

Re:The maths paper please (1)

helioquake (841463) | more than 8 years ago | (#16164453)

By the way I am sure the design, as it is, will fail.

Like I said, the key is to design a perfect cavity system.

Efficency? (1)

Anonymous Coward | more than 8 years ago | (#16164262)

1 kilowatt for 16 millinewtons of force.

He'd probably have better luck with an ion drive.

Not possible (1, Redundant)

Watson Ladd (955755) | more than 8 years ago | (#16164266)

  1. The law of conservation of momentum is never violated.
  2. The drive is a closed system.
  3. So it cannot accelerate.
Also he made a mistake in his calculations. The forces at the end might be different, but forces aren't only being exterted on the ends.

Re:Not possible (1, Funny)

Anne Honime (828246) | more than 8 years ago | (#16164328)

Mandatory : "Everybody said it was impossible, then a fool came who didn't knew and made it." It wouldn't be the first time in science history that something happens to work in spite of mathematics, not because maths are wrong per se but because the thing reveals an entirely unknown field of physics.

Re:Not possible (1)

alienw (585907) | more than 8 years ago | (#16164417)

First, can you provide an example of this? In all of the cases I looked at, the theory came decades before any practical implementation. Things before the 19th century don't really count, since science wasn't mainstream then. Second, his apparatus doesn't actually work -- as he admits, the measured force is less than the margin of error of his equipment.

Re:Not possible (1)

Anne Honime (828246) | more than 8 years ago | (#16164458)

"First, can you provide an example of this?"

There's an easy one to check : planes (generaly heavier-than-air) flight has been deemed impossible by the scientific community until the Wright brothers publicly demonstrated it, several years after the first flight of Clément Ader (who was treated like a lunatic). And in spite of the demo, it took again several years after the event for some scientists to actualy admit it !

And this didn't happened in the middle ages, but at the eve of the XXth century, the time of the triumph of science !

Microwave propulsion (0)

Anonymous Coward | more than 8 years ago | (#16164279)

Finally a use for microwave burritos!!

Power? (2, Funny)

misleb (129952) | more than 8 years ago | (#16164285)

Um, I didn't read TFA, but wouldln't this require a power source? Specifically, eletricity? How does one generate that much wattage? Flux capacitor?

-matthew

Re:Power? (0)

Anonymous Coward | more than 8 years ago | (#16164317)

Do you know how much power a kilowatt is?

Re:Power? (1)

lostngone (855272) | more than 8 years ago | (#16164401)

Ummm, Hello!?!?!? Ever hear of Warp Drive. Like Duh. :)

Re:Power? (0)

Anonymous Coward | more than 8 years ago | (#16164430)

To generate electrical power we tend to use some kind of GENERATOR. I have a compact unit in the front of my car that could generate around 200KW if suitably adapted. It uses fuel in the form of a petroleum distillate.

Re:Power? (1)

vanyel (28049) | more than 8 years ago | (#16164431)

The article specifically talks about solar cells in space or some sort of electrical generation here, though burning up your coolant hydrogen in the electrical generator seems counterproductive. And how much energy does it take to supercool the hydrogen? Not sure it's a mileage win.

One thing I'm curious about is the mechanism by which movement absorbs energy in the system. Absorption and conversion to heat would seem to the end product of the microwaves, but I don't see how movement affects that, at least until you reach speeds high enough to make a noticeable difference in the wavelength...

Slashdot - where science makes no sense (TM) (5, Insightful)

davidoff404 (764733) | more than 8 years ago | (#16164294)

Pity thee, dearest /. This New Scientist article has already received a lot of attention [columbia.edu] from the physics community, much of it bemoaning the abysmal standards to which New Scientist has slipped. Not only does the article suggest that this "drive" violates conservation of momentum, the author actually realises this but tries to sweep this (rather fundamental) point under the carpet with lots of handwaving and muttering about "frames of reference". Not only is this atrocious journalism, it's also a sad indication of the levels to which a once-great magazine has now sunk

In fact, the article in question is so bad, a petition has been started among scientists to save New Scientist from itself [utexas.edu] . On a somewhat related note, do /. editors even bother to read the submissions any more? Even a cursory glance at the article would have been enough to convince anyone that it's unintelligible garbage.

Slashdot - where science is just a word that goes before fiction.

Re:Slashdot - where science makes no sense (TM) (1)

naoursla (99850) | more than 8 years ago | (#16164364)

I've always thought "New Scientist" was mostly junk. If I see something on /. that is scientifically questionable it is usually from "New Scientist". I thought the name even sold itself as being on the fringe. "New Scientist" being a scientist working on new stuff on the fringe that may or may not be valid.

Re:Slashdot - where science makes no sense (TM) (1)

$RANDOMLUSER (804576) | more than 8 years ago | (#16164426)

The latest New Scientist... ...There is a working prototype...

My first reaction was: "you must be new here..."

Re:Slashdot - where science makes no sense (TM) (2, Interesting)

geekoid (135745) | more than 8 years ago | (#16164391)

"..much of it bemoaning the abysmal standards to which New Scientist has slipped. "

well.ets be honest here, scientist always have a habit of doing that when something they don't agree with is published.

". Not only does the article suggest that this "drive" violates conservation of momentum,"

There is nothing in Relativity that says this someone can't exploit the difference in frames.

Do I have my doubts? certianly, and strong ones at that. strangly, the article doesn't ring the BS meter.

Having a working prototype(alledgedly) is a good start. His credtionals seem good.
Agreeing to independent review is also good. Most people BSing about this stuff say things like 'the scientific community is keeping me down.' and won't allow third parties to review the work unless they are paid money in advance.

Re:Slashdot - where science makes no sense (TM) (4, Interesting)

MrSteveSD (801820) | more than 8 years ago | (#16164396)

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.

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/ YaBB.pl?num=1157719780/0)

Re:Slashdot - where science makes no sense (TM) (1)

rco3 (198978) | more than 8 years ago | (#16164407)

You seem to be under the impression that the poor science somehow disqualifies it from consideration by Slashdot editors. I think there's a flaw in your underlying assumptions. Perhaps you'd like to spell some of them out, and we could work together to find which assumptions are erroneous?

The Rocket Monopolist Conspiracy! (3, Insightful)

smclean (521851) | more than 8 years ago | (#16164309)

Shawyer argues that for companies investing billions in rockets and launch sites, a new technology that leads to fewer launches and longer-lasting satellites has little commercial appeal.
Yeah, those companies are just dying to spend as much money as possible trying to get their satellites in orbit. They are looking into purchasing rockets made from ground up hundred dollar bills.

I hope his invention is better than his explanations for why he has no investors (I know, I know, it's not).

Bad marketing name... (1)

curious.corn (167387) | more than 8 years ago | (#16164311)

I'd call it the em-motive... or e-motive (if it weren't for IBM's probable copyright for e-anything) e

Awesome! (5, Funny)

LewsKinslayer (87724) | more than 8 years ago | (#16164319)

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.

Re:Awesome! (1)

RatBastard (949) | more than 8 years ago | (#16164384)

What scares me is that I know what everything in your post is except Parrot.

Re:Awesome! (1)

curious.corn (167387) | more than 8 years ago | (#16164464)

??? what ???

journalist, at least, is totally clueless (3, Interesting)

coyote-san (38515) | more than 8 years ago | (#16164345)

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.)

low momentum (1)

orz (88387) | more than 8 years ago | (#16164348)

My understanding of the basic math suggests that a photon-creating drive will tend to be inefficient. The amount of light energy necessary to get a significant amount of momentum is simply enormous, which is why you don't feel flashlights, even very bright ones, pushing backwards perceptably when you turn them on.

The article makes this guys thing sound like some kind of perpetual motion machine limited only by his ability to build a perfecct cavity. I haven't read his paper yet, but I'm skeptical of his ability to get more momentum out of a photon that the photon itself contains, unless he has some other reaction mass. If his photons are transfering momentum to the cavity on each continually, then the photons should be losing momentum as they do so (in the form of dopler shift?), and therefore the total momentum gained should be no greater than merely shining a flashlight backwards.

Or at least, that's my understanding. I Am Not A Physicist.

Rocket the size of a suitcase? (2, Funny)

noidentity (188756) | more than 8 years ago | (#16164355)

Potentially, it could pack the punch of a rocket in a box the size of a suitcase.

That seals it. The terrerists could use this, so we must ban all further research!

This is complete bollocks (5, Informative)

LauraScudder (670475) | more than 8 years ago | (#16164356)

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 [utexas.edu] 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.

complete and utter nonsense (3, Interesting)

jonniesmokes (323978) | more than 8 years ago | (#16164388)

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.

Nuclear Wessals (1)

Drago Kith Somtaw (983110) | more than 8 years ago | (#16164389)

microwaves are interesting and stuff
but why don't we just use nuclear bombs for propellant.
After all the first man-made object that went into space was that giant manhold cover that the US was using in 1955 for underground nuclear weapons testing

Re:Nuclear Wessals (0)

Anonymous Coward | more than 8 years ago | (#16164477)

Manhold?

Have you never actually been to school?

Latest? (1)

Kaemaril (266849) | more than 8 years ago | (#16164399)

The latest New Scientist has an article about...

The New Scientist is a weekly publication. This article is from the Sept. 9th edition. In what way does this make it 'the latest', given that two subsequent editions (16th, 23rd) have been published?

BAHAHAHAHAHA (1, Funny)

Anonymous Coward | more than 8 years ago | (#16164404)

Hey, guys, while you are at it, I have this idea for an infinate power source! You see, you take an electric motor and you connect the axel to a lot of generators! You see one of the generators would power the motor and you could run the whole world on as many other generators as you tacked on! Use it! My gift to humanity! ;P

Seriously, all this guy is missing is the smoke.

It doesn't matter that one end of the frickin copper has a bigger diameter than the other, the walls are not normal to the surfaces and will absorb any force from the collisions with the photons as well. The 2 normal forces would be equal in each direction and thus would be 0 net force for the system. The only thing that would happen is the can would have a tendency to expand a very small amount more that what could be accounted for by thermal expansion alone at best.

Think about it. Otherwise conical objects would have a tendancy to rocket around on their own because of air pressure.

Pedestrians are cooked (1)

ChadL (880878) | more than 8 years ago | (#16164414)

Even if this did have a chance of working... I would love to be the one who walks on the sidewalk while the "floating cars" send out their microwaves to cook me...

Easy to test, no satellite needed (5, Interesting)

sehlat (180760) | more than 8 years ago | (#16164465)

Easy to test: no satellite needeed. From Jerry Pournelle [jerrypournelle.com] 's web site:
TESTS If anyone does have a candidate device for producing reactionless acceleration -- that is, linear acceleration without throwing mass overboard and without reacting with a medium such as air or water -- the first test is to suspend it on two wires attached so that the plane of the two wires is normal to the direction of thrust-- that is, make a swing and put your gadget on it facing in the normal direction of travel of the swing. Now turn it on. If it will hang non-vertically, get interested. Now cover it with a plastic garbage bag and see if it will still hang non-vertically. If it will still do so, turn it off, and if it settles to a vertical angle, and you can do this repeatedly, and it hasn't lost any mass during the experiments, call your local physics professor. Or call me. I'll take care of notifying the Swedish Academy. But until it will do that, I don't need to look at it...

No no no.. You have it all wrong (1)

cyberfunkr (591238) | more than 8 years ago | (#16164467)

He actually made the Infinite Improbability Drive [wikipedia.org] ! He just left a Brownian motion producer in the microwave when he turned it on creating a Really Hot cup of tea.
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?