Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: Fineus on September 13, 2006, 08:28:27 am
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http://www.newscientist.com/channel/fundamentals/mg19125681.400-relativity-drive-the-end-of-wings-and-wheels.html
Roger Shawyer has developed an engine with no moving parts that he believes can replace rockets and make trains, planes and automobiles obsolete. "The end of wings and wheels" is how he puts it. It's a bold claim.
Of course, any crackpot can rough out plans for a warp drive. What they never show you is evidence that it works...
Here's the full article since you need to pay to see it at the site itself.
The trip from London to Havant on the south coast of England is like travelling through time. I sit in an air-conditioned train, on tracks first laid 150 years ago, passing roads that were known to the Romans. At one point, I pick out a canal boat, queues of cars and the trail from a high-flying jet - the evolution of mechanised travel in a single glance.
But evolution has a habit of springing surprises. Waiting at my destination is a man who would put an end to mechanised travel. Roger Shawyer has developed an engine with no moving parts that he believes can replace rockets and make trains, planes and automobiles obsolete. "The end of wings and wheels" is how he puts it. It's a bold claim.
Of course, any crackpot can rough out plans for a warp drive. What they never show you is evidence that it works. Shawyer is different. He has built a working prototype to test his ideas, and as a respected spacecraft engineer he has persuaded the British government to fund his work. Now organisations from other parts of the world, including the US air force and the Chinese government, are beating a path to his tiny company.
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. It could even lead to aircraft that will not need wings at all. I can't help thinking that it sounds too good to be true.
When I meet Shawyer, he turns out to be reassuringly normal. His credentials are certainly impressive. He worked his way up through the aerospace industry, designing and building navigation and communications equipment for military and commercial satellites, before becoming a senior aerospace engineer at Matra Marconi Space (later part of EADS Astrium) in Portsmouth, near where he now lives. He was also a consultant to the Galileo project, Europe's satellite navigation system, which engineers are now testing in orbit and for which he negotiated the use of the radio frequencies it needed.
Dangerous idea
With that pedigree, you'd imagine Shawyer would be someone the space industry would have listened to. Far from it. While at Astrium, Shawyer proposed that the company develop his idea. "I was told in no uncertain terms to drop it," he says. "This came from the very top."
What Shawyer had in mind was a replacement for the small thrusters conventional satellites use to stay in orbit. The fuel they need makes up about half their launch weight, and also limits a satellite's life: once it runs out, the vehicle drifts out of position and must be replaced. Shawyer's engine, by contrast, would be propelled by microwaves generated from solar energy. The photovoltaic cells would eliminate the fuel, and with the launch weight halved, satellite manufacturers could send up two craft for the price of one, so you would only need half as many launches.
So why the problem? 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. By the same token, a company that offers more for less usually wins in the end, so Shawyer's idea may have been seen as too speculative. Whatever the reason, in 2000, he resigned to go it alone.
Surprisingly, Shawyer's disruptive technology rests on an idea that goes back more than a century. In 1871 the physicist James Clerk Maxwell worked out that light should exert a force on any surface it hits, like the wind on a sail. This so-called radiation pressure is extremely weak, though. Last year, a group called The Planetary Society attempted to launch a solar sail called Cosmos 1 into orbit. The sail had a surface area of about 600 square metres. Despite this large area, about the size of two tennis courts, its developers calculated that sunlight striking it would produce a force of 3 millinewtons, barely enough to lift a feather on the surface of the Earth. Still, it would be enough to accelerate a craft in the weightlessness of space, though unfortunately the sail was lost after launch. NASA is also interested in solar sails, but has never launched one. Perhaps that shouldn't be a surprise, as a few millinewtons isn't enough for serious work in space.
But what if you could amplify the effect? That's exactly the idea that Shawyer stumbled on in the 1970s while working for a British military technology company called Sperry Gyroscope. Shawyer's expertise is in microwaves, and when he was asked to come up with a gyroscopic device for a guidance system he instead came up with the idea for an electromagnetic engine. He even unearthed a 1950s paper by Alex Cullen, an electrical engineer at University College London, describing how electromagnetic energy might create a force. "It came to nothing at the time, but the idea stuck in my head," he says.
In his workshop, Shawyer explains how this led him to a way of producing thrust. For years he has explored ways to confine microwaves inside waveguides, hollow tubes that trap radiation and direct it along their length. Take a standard copper waveguide and close off both ends. Now create microwaves using a magnetron, a device found in every microwave oven. If you inject these microwaves into the cavity, the microwaves will bounce from one end of the cavity to the other. According to the principles outlined by Maxwell, this will produce a tiny force on the end walls. Now carefully match the size of the cavity to the wavelength of the microwaves and you create a chamber in which the microwaves resonate, allowing it to store large amounts of energy.
What's crucial here is the Q-value of the cavity - a measure of how well a vibrating system prevents its energy dissipating into heat, or how slowly the oscillations are damped down. For example, a pendulum swinging in air would have a high Q, while a pendulum immersed in oil would have a low one. If microwaves leak out of the cavity, the Q will be low. A cavity with a high Q-value can store large amounts of microwave energy with few losses, and this means the radiation will exert relatively large forces on the ends of the cavity. You might think the forces on the end walls will cancel each other out, but Shawyer worked out that with a suitably shaped resonant cavity, wider at one end than the other, the radiation pressure exerted by the microwaves at the wide end would be higher than at the narrow one.
Key is the fact that the diameter of a tubular cavity alters the path - and hence the effective velocity - of the microwaves travelling through it. Microwaves moving along a relatively wide tube follow a more or less uninterrupted path from end to end, while microwaves in a narrow tube move along it by reflecting off the walls. The narrower the tube gets, the more the microwaves get reflected and the slower their effective velocity along the tube becomes. Shawyer calculates the microwaves striking the end wall at the narrow end of his cavity will transfer less momentum to the cavity than those striking the wider end (see Diagram). The result is a net force that pushes the cavity in one direction. And that's it, Shawyer says.
Hang on a minute, though. If the cavity is to move, it must be pushed by something. A rocket engine, for example, is propelled by hot exhaust gases pushing on the rear of the rocket. How can photons confined inside a cavity make the cavity move? This is where relativity and the strange nature of light come in. Since the microwave photons in the waveguide are travelling close to the speed of light, any attempt to resolve the forces they generate must take account of Einstein's special theory of relativity. This says that the microwaves move in their own frame of reference. In other words they move independently of the cavity - as if they are outside it. As a result, the microwaves themselves exert a push on the cavity.
“How can photons confined inside a cavity make the cavity move? This is where relativity and the strange nature of light come in”
Each photon that a magnetron fires into the cavity creates an equal and opposite reaction - like the recoil force on a gun as it fires a bullet. With Shawyer's design, however, this force is minuscule compared with the forces generated in the resonant cavity, because the photons reflect back and forth up to 50,000 times. With each reflection, a reaction occurs between the cavity and the photon, each operating in its own frame of reference. This generates a tiny force, which for a powerful microwave beam confined in the cavity adds up to produce a perceptible thrust on the cavity itself.
Shawyer's calculations have not convinced everyone. Depending on who you talk to Shawyer is either a genius or a purveyor of snake oil. David Jefferies, a microwave engineer at the University of Surrey in the UK, is adamant that there is an error in Shawyer's thinking. "It's a load of bloody rubbish," he says. At the other end of the scale is Stepan Lucyszyn, a microwave engineer at Imperial College London. "I think it's outstanding science," he says. Marc Millis, the engineer behind NASA's programme to assess revolutionary propulsion technology accepts that the net forces inside the cavity will be unequal, but as for the thrust it generates, he wants to see the hard evidence before making a judgement.
Thrust from a box
Shawyer's electromagnetic drive - emdrive for short - consists in essence of a microwave generator attached to what looks like a large copper cake tin. It needs a power supply for the magnetron, but there are no moving parts and no fuel - just a cord to plug it into the mains. Various pipes add complexity, but they are just there to keep the chamber cool. And the device seems to work: by mounting it on a sensitive balance, he has shown that it generates about 16 millinewtons of thrust, using 1 kilowatt of electrical power. Shawyer calculated that his first prototype had a Q of 5900. With his second thruster, he managed to raise the Q to 50,000 allowing it to generate a force of about 300 millinewtons - 100 times what Cosmos 1 could achieve. It's not enough for Earth-based use, but it's revolutionary for spacecraft.
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 and in measuring the forces involved. "It's not easy because the forces are tiny compared to the weight of the equipment," he says.
Optimising the cavity is crucial, and it's as much art as science. Energy leaks out in all kinds of ways: microwaves heat the cavity, for example, changing its electrical characteristics so that it no longer resonates. At very high powers, microwaves can rip electrons out of the metal, causing sparks and a dramatic loss of power. "It can be a very fine balancing act," says Shawyer.
To review the project, the UK government hired John Spiller, an independent space engineer. He was impressed. He says the thruster's design is practical and could be adapted fairly easily to operate in space. He points out, though, that the drive needs to be developed further and tested by an independent group with its own equipment. "It certainly needs to be flown experimentally," he says.
Armed with his prototypes, the test measurements and Spiller's review, Shawyer is now presenting his design to the space industry. The reaction in China and the US has been markedly more enthusiastic than that in Europe. "The European Space Agency knows about it but has not shown any interest," he says. The US air force has already paid him a visit, and a Chinese company has attempted to buy the intellectual property associated with the thruster. This month, he will be travelling to both countries to visit interested parties, including NASA.
To space and beyond
His plan is to license the technology to a major player in the space industry who can adapt the design and send up a test satellite to prove that it works. If all goes to plan, Shawyer believes he could see the engine tested in space within two years. He estimates that his thruster could save the space industry $15 billion over the next 10 years. Spiller is more cautious. While the engine could certainly reduce the launch weight of a satellite, he doubts it will significantly increase its lifetime since other parts will still wear out. The space industry might not need to worry after all.
Meanwhile Shawyer is looking ahead to the next stage of his project. He wants to make the thrusters so powerful that they could make combustion engines obsolete, and that means addressing the big problem with conventional microwave cavities - the amount of energy they leak. The biggest losses come from currents induced in the metal walls by the microwaves, which generate heat when they encounter electrical resistance. This uses up energy stored in the cavity, reduces the Q, and the thrust generated by the engine drops.
Fortunately particle accelerators use microwave cavities too, so physicists have done a lot of work on reducing Q losses inside them. The key, says Shawyer, is to make the cavity superconducting. Without electrical resistance, currents in the cavity walls will not generate heat. Engineers in Germany working on the next generation of particle accelerators have achieved a Q of several billion using superconducting cavities. If Shawyer can match that performance, he calculates that the thrust from a microwave engine could be as high as 30,000 newtons per kilowatt - enough to lift a large car.
This raises another question. Why haven't physicists stumbled across the effect before? They have, says Shawyer, and they design their cavities to counter it. The forces inside the latest accelerator cavities are so large that they stretch the chambers like plasticine. To counteract this, engineers use piezoelectric actuators to squeeze the cavities back into shape. "I doubt they've ever thought of turning the force to other uses," he says.
No doubt his superconducting cavities will be hard to build, and Shawyer is realistic about the problems he is likely to meet. Particle accelerators made out of niobium become superconducting at the temperature of liquid helium - only a few degrees above absolute zero. That would be impractical for a motor, Shawyer believes, so he wants to find a material that superconducts at a slightly higher temperature, and use liquid hydrogen, which boils at 20 kelvin, as the coolant. Hydrogen could also power a fuel cell or turbine to generate electricity for the emdrive.
In the meantime, he wants to test the device with liquid nitrogen, which is easier to handle. It boils at 77 kelvin, a temperature that will require the latest generation of high-temperature ceramic superconductors. Shawyer hasn't yet settled on the exact material, but he admits that any ceramic will be tricky to incorporate into the design because of its fragility. It will have to be reliably bonded to the inside of a cavity and mustn't crack or flake when cooled. There are other problems too. The inside of the cavity will still be heated by the microwaves, and this will possibly quench the superconducting effect. "Nobody has done this kind of work," Shawyer says. "I'm not expecting it to be easy."
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. A fan or turbine attached to the back of the vehicle could then be used to move it forward without friction. He hopes to demonstrate his first superconducting thruster within two years.
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. Shawyer suggested to me before I left that a hover car with an emdrive thruster cooled and powered by hydrogen could be a major factor in converting our society from a petrol-based one to one based on hydrogen. "You need something different to persuade people to make the switch. Perhaps being able to move in three dimensions rather than two would do the trick."
What about aircraft without wings? I'm aware that my feeling of scepticism is being replaced by a more dangerous one of unbounded optimism. In five minutes of blue-sky thinking you can dream up a dozen ways in which the emdrive could change the world. I have an hour ahead of me. The end of wings and wheels. Now there's a thought.
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Summarise it in one word.
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Alakazam!
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Summarise it in one word.
How about three?
"Infinite Improbability Drive"
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Interesting, but unless he can improve it to out-perform the new ion drives it probably won't have much impact.
Worth pursuing though.
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Summarise it in one word.
How about three?
"Infinite Improbability Drive"
"Oh no, not again" - Bowl of Petunias
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Summarise it in one word.
How about three?
"Infinite Improbability Drive"
Awesome.
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Summarise it in one word.
Impossible, though "Alakazam!" was quite close.
Simply put:
The guy claims he has invented a propulsion technology which alters momentum of the object it is attached to, without ejecting anything into opposite direction.
If we discount the fact that this is in blatant violation of all physics (mainly the conservation of momentum, which in many way is the physics, this kind of technique would have several major advantages in space traveling, compared to rocket engines or ion engines or anything that uses propellant to create equal and opposite force. This law says that the momentum of a closed system is constant, period. This means that a rocket and its propellant can be seen as a closed system. If all propellant stays in rocket - or if the rocket runs out of propellant - the rocket cannot alter its own momentum. But if the rocket engine gives some of the propellant a momentum to negative direction, rocket itself gains equal momentum to positive direction.
A space ship equipped with this claimed, new kind of drive system would only need a way to produce ****loads of energy; it wouldn't need to transport propulsion matter within it. Obviously a fusion reactor would be ideal solution for energy production in space ship; it would allow the ship to carry the least amount of fuel. Of course, it the reactor was also Helium compatible, the helium could also be fused, but let's just get Hydrogen fusion working first... :lol:
The advantage in ship building costs would be awesome, since there would be no need to carry vast amounts of propellant with the space ship in equally gigantic tanks.
But the greater advantage would be that there would be no maximum reached impulse, as there is with engines ejecting stuff backwards at velocity v. Normally, the maximum impulse a space ship can get is
I = d m * v
in which I is obviously impulse, d m is the mass change of the ship (ie. how much propellant it uses in mass units) and v is the ejection speed of the propellant.
If impulse change was possible without mass change, the ship could keep accelerating as long as it had energy to produce. This would enable ship to use the fastest way from A to B; accelerate to halfway at constant acceleration a and then decelerate the rest of the way with -a acceleration.
In short, if this thing really works, the conservation of momentum is screwed, which will require some pretty damn heavy modifications (read: scrapping and building from scratch) to every single bit of physics ever built, starting from classical mechanics and proceeding to General Relativity and Quantum Mechanics.
It will also open new space traveling era if it really works and can be yielded (and if it works, why couldn't it be...)
Even as unlikely this is to really work, I find it intriguing nevertheless.
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It's a flight of fancy, nothing else......
Although he could sell it to americans, They'll buy anything, *cough London bridge cough*
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I think dismissing it as a flight of fancy is a little off.
This is clearly a working technology, and while it won't become the core of a double decker bus tomorrow it does have potential to be developed.
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sweet i hope it works, hovercars ftw
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"Oh no, not again" - Bowl of Petunias
"I shal call this wind." - Whale.
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if the prototype model works as the article mentioned, it at the very least would be a replacement for the fuel based reaction control systems cuttently in use. according to the article the engine looses energy as you accelerate, so youd have to keep your acceleration to a minimum otherwise the engine becomes an ineffieteint piece of crap.
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I think dismissing it as a flight of fancy is a little off.
This is clearly a working technology, and while it won't become the core of a double decker bus tomorrow it does have potential to be developed.
Ditto. The lot of you who are quick to dismiss something as bollocks are what's holding back a lot of potentially revolutionary discoveries. Just as radical thought is dangerous, such also is conservative.
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I think dismissing it as a flight of fancy is a little off.
This is clearly a working technology, and while it won't become the core of a double decker bus tomorrow it does have potential to be developed.
Ditto. The lot of you who are quick to dismiss something as bollocks are what's holding back a lot of potentially revolutionary discoveries. Just as radical thought is dangerous, such also is conservative.
... And we have seen how many of these threads, 5013, and how many have turned out to become actually working technology? We're lucky if even one.
The burden of proof is on the inventor to prove his concept right and working, and as the concept sounds wacky I will find skeptism very healthy.
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ok, so I'd like to ask one of the more physics minded people a conservation question.
if I have a nulcear submarean that has suddenly been transported into outer space (and for some irrelivent to the larger point of the question reason the design of the sub allows it to continue functioning in a vacume). it is moveing at a constant velocity, yet inside it has a nuclear reactor wich is breaking apart uranium atoms for energy, as it does this the mass of the uranium and by extention the mass of the whole system (sub) it'self decreases (if I understand my nuclear physics properly). yet it's velocity remains the same, the propellers might spin in one direction or the other, but the velocity of the whole system remains constant yet the mass does not, by conservation of inertia, isn't this imposable? because I=M*V, the inertia of the system is going down, because the mass of the system is going down and the velocity isn't going up to counter this.
could it be posable that this situation is something similar?
I'll ask my physics teacher about this tomarrow and see if there is some odd thing in relitiveity that might allow this.
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In the situation above, it still loses energy through heat radiation even if nothing else leaves the sub.
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For the mass of the reactor to be dropping, it'd need to be converting matter to energy - which would increase the overall energy of the system.
Conservation of inertia, mass and whatnot are all about energy, not their individual components.
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well the argument so far is that inertia must always be conserved, not that energy must always be conserved, in this system energy couldeasily be conserved, even if inertia isn't.
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well the argument so far is that inertia must always be conserved, not that energy must always be conserved, in this system energy couldeasily be conserved, even if inertia isn't.
The voyager probes have plutonium to power their systems, ask NASA.
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ok, so I'd like to ask one of the more physics minded people a conservation question.
if I have a nulcear submarean that has suddenly been transported into outer space (and for some irrelivent to the larger point of the question reason the design of the sub allows it to continue functioning in a vacume). it is moveing at a constant velocity, yet inside it has a nuclear reactor wich is breaking apart uranium atoms for energy, as it does this the mass of the uranium and by extention the mass of the whole system (sub) it'self decreases (if I understand my nuclear physics properly). yet it's velocity remains the same, the propellers might spin in one direction or the other, but the velocity of the whole system remains constant yet the mass does not, by conservation of inertia, isn't this imposable? because I=M*V, the inertia of the system is going down, because the mass of the system is going down and the velocity isn't going up to counter this.
could it be posable that this situation is something similar?
I'll ask my physics teacher about this tomarrow and see if there is some odd thing in relitiveity that might allow this.
Well, easiest answer is that an object traveling at constant speed is in the middle of its own reference co-ordinate system, and if its mass is reduced by, say, slicing a piece of it away, the speed of the main body has no reason whatsoever to accelerate (change speed in any direction). Its momentum is reduced, but the sliced part of the body gets that momentum.
In a space ship, the "sliced" bit is fotons emitting at statistically every direction from the ship. The fotons have momentum, and they "steal" some momentum from the ship.
However, if we have a theoretical space ship that we all love, that does not emit anything and absorbs everything that the reactor produces, things become more interesting... but not that much.
In this scenario, particles and fotons radiated in the reactor core all absorb into the ship surrounding it, nothing escapes into space.
Thus, the energy of the ship-reactor system remains the same, and so does momentum. The thing which is important to notice here is that when nuclear reactions reduce mass of entire system, the momentum that these particles gained is absorbed into the surrounding hull. Again statistically, photons and mass particles are emitted into every direction from the reaction, so all parts of the ship get even dose of radiation (energy and momentum).
From this on, things become interesting.
If we consider the ship-reactor system on time t=0, the system has mass m, energy E = mc^2 and momentum p = mv... however, the momentum also has relation to ship's overall energy via the mass-energy relation, so momentum can equally be annouced as
p = v*E/c^2
At t=1, N amount of nuclear reactions occur in the reactor. They release particles and fotons at even directions. Now the reactor has less energy, less mass and less momentum than at t=0, but the velocity remains same - because it gave momentum to even directions.
At t=2, the radiation hits the spherical core around the reactor... mass particles come a bit later, but they have the same effect as fotons so it's no use to handle them separately.
What happens here is that the momentum of the fotons is transferred to ship's particles. The momentum of particles is then transferred to other particles that are close, and then to others... and others... And lo behold, the momentum originated in the reactor takes place as thermal energy in the core of the ship.
So, in a "closed ship" scenario the momentum of the system does conserve; it just changes form and becomes not-so easily noticeable. The ship heats, the heated matter has particles that have kinetic energy, which means that they have momentum... the very same momentum that came from the reactor.
So, all in all the energy of the ship remains the same, if nothing is removed from it, and thus the momentum and speed also remain same. Momentum is just dispersed along the ship so every bit of momentum pointing to direction is negated by other, random directed momentums. The sum of momentum is still the same that it was at t=0.
At least this is how I would handle this subject. Though my knowledge of physics is yet quite limited... :D
Of course, this kind of ship would be a death trap to all inside it, as it would rather quickly reach rather higher temperatures. In truth, most of thermal energy produced must be radiated out of a ship to retain the thermal equilibrium. To keep the crew quarters at static temperatures, the heating system must only work at same rate that the ship absorbs to space. Most reactors produce way more thermal energy... and when thermal energy is radiated away from the ship, it steals some of the ship's energy - most being energy from the reactor, energy which was converted from matter to radiation. And this does indeed reduce the momentum of the ship itself, even though the vvelocity remains the same.
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I thought photons had no mass? if they have no mass how can they have (or 'steal') momentum? I can understand loseing energy, but not momentum.
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That's because mother nature is a *****.
Photons have zero mass but carry momentum anyway.
To be more exact, they have zero rest mass, but like any moving particle they have a relativistic mass (or just energy, depending which nomenclature you're using)
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Dear God he's right (http://en.wikipedia.org/wiki/Photon)
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I think dismissing it as a flight of fancy is a little off.
This is clearly a working technology, and while it won't become the core of a double decker bus tomorrow it does have potential to be developed.
Ditto. The lot of you who are quick to dismiss something as bollocks are what's holding back a lot of potentially revolutionary discoveries. Just as radical thought is dangerous, such also is conservative.
... And we have seen how many of these threads, 5013, and how many have turned out to become actually working technology? We're lucky if even one.
The burden of proof is on the inventor to prove his concept right and working, and as the concept sounds wacky I will find skeptism very healthy.
So? By restriction spread of the idea and immediately writing it off as bollocks, you potentially crush the one in five thousand that does work.
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ok, so as far as the subject of this propulsion system is concerned, is it posable for a photon to bounce off an particle without imparting momentum to it? since it seems to have momentum defined diferently for it. I'm guessing the answer is no, but if it's yes, then this might work.
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[tangent]wait a sec, what about gravity? if we had some insainly huge black hole level gravity well (event horison about the size of a marble) and we fired a photon beam at it in just the right angle so that it would slingshot around and hit a reflecting surface, and back again forming a roughly u shaped path, would that do it? photons have no mass and thus nothing can be atracted to them but they can be diverted by gravity without effecting the masses involved (right?), so every interaction with the reflective surface would impart momentum and then it would get wiped around and hit the surface again. the momentum is haveing it's direction changed by gravity without induceing a opposite reaction.[/tangent]
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ok, so as far as the subject of this propulsion system is concerned, is it posable for a photon to bounce off an particle without imparting momentum to it?
No.
When an object reflects a photon, it actually first receives the momentum of the photon; then, when it sends it back on its journey, it gives the photon some momentum and gains itself equal opposite momentum, so in reflection situations, the reflector gains two times the momentum of the actual photon... that might seem weird at first, but if you want to, take a closer look at what happens in reflection situation.
When a photon "bounces" off from a particle, what happens is that it briefly absorbs to the particle, and then the particle emits a new photon to a direction defined by the particle's effect on electromagnetic wave frontier. Or, the photon may stay absorbed...
Reflective surfaces are interesting thing. They have uniform surface structure, which causes the impacting EM-waves to behave jsut like any other wave hitting straight surface. But the photons that are reflected are not the "same" photons that hit the reflector...
You see, a photon is a seemingly anomalous little bastard, though the strangeness fades a bit when you get to know the things behind phenomena (only to get new strangenesses to ponder).
A photon always travels at speed of light, related to any and all reference frames. That means that the photons experience no time, and thereby they also cannot change. From photon's point of view, the start of its life and journey and the end of them are the same.
That is also because a photon does not, and indeed cannot have rest mass - a photon cannot be at rest.
It a photon would be at rest compared to an object, it would not exist. Maxwell's electrodynamics contain this anomality, and that lead Einstein to state that every observer measures speed of light to be constant in all situations.
So, if a photon cannot be at rest and it always has constant speed, it also cannot change its direction during its life. Bouncing off a surface would involve changing the speed vector, which a photon cannot do as a particle. However, if the conditions are good enough to keep the wave front intact and the photon's energy is immediately emitted from an electron that absorbed it, the result is that the bouncing electromagnetic wave front gives some of the original photon's properties to the new one; most important being the direction, which follows Huygens' principles. That gives an impression of a reflecting photon; it's not really the same photon but it has the same wave length, same energy and logical reflection direction, so it can be handled as the "same" photon.
A good mirror reflects more than 90 % of all the photons that hit the electrons on its surface, and the reflection always has some scattering on it - the amount is inversely relative to quality of the mirror. The smoother it is, the less scattering. Matt surfaced objects reflect very scattered light; mirrors reflect very little scattered light.
Um... where was I? Yes, momentum.
A photon has momentum because it has energy; the momentum of photon is not, however, relative to the speed of it due to the fact that all photons have exact same speed regardless of their energy. As was already said, photons have a momentum mass because they have energy; the amount of mass used in momentum calculations is
m = E / c^2
The energy of a photon is
E = hf; thus the momentum of a photon is directly proportional to its frequency... and inversely proportional to its wave length:
p(f) = m*v = hf/c^2 * c = h f/c
...oh, and h is the Planck's constant, should it mean something to you. Whatever. Photon has momentum, always, period.
When the photon hits an object, it is absorbed into matter... usially the particle being an electron.
If the electron happens to be in stable state, it almost instantaneously emits a new photon back; this happens so fast that the quantum wave front of the photon is still there. If a new photon is emitted fast enough, it takes the reflection direction of the original photon's wave front.
Some photons don't reflect; that's because the poor buggers are absorbed more permanently by the mirror surface and their energy is used to heat the mirror.
since it seems to have momentum defined diferently for it. I'm guessing the answer is no, but if it's yes, then this might work.
Huh?
The momentum of a single photon is always defined by
p = hf/c.
In reflection situation, the reflecting body gains two times the momentum of a photon; first time at arrival, second time at departure.
The weird thing in this particular claimed physics-breaker is that the photons are bouncing inside a confined space. It should be theoretically impossible for them to excert greater force on one end of a chamber than on other end, because statistically, they do not exit the chamber (except the occasional few), so the conservation of momentum is not valid if there indeed is a measurable force produced by this device.
It all boils down to whether or not the prototype works. If it works, it will become a subject of wild research, while it also can be of course used in applications even if it's not completely understood. People have done it before. Fire is a good example of that... :)
Oh, another message...
Well, gravity doesn't have effect on reflections, it's all wave motion principles and the fact that light have wave motion characteristics.
And, insanely huge black holes wouldn't be the size of a marble. They would be (and are) kilometres wide in event horizon apparent diameter.
I really can't say everything I know about black holes here and now, so sufice to say that if a photon hits the event horizon tangentially, it will forever and ever go round and round the event horizon's surface. If it goes in, it will forever spiral towards the nonexistent center of infinitely deep gravity well; if it swoops past the event horizon, it will not be emprisoned by the hole, but instead the straight path (geoide) in this area of space will take the photon onto journey around the black hole, much in a way you described.
Keep in mind though that if you apply General Relativity to matters, you have to apply it to all of them. The momentum of a photon diverted by gravity does not change, because its direction does not change and no forces are exerted upon it.
...As the annoying child in Matrix said "the spoon doesn't bend, you do" or something like that. The photon travels straight, period. What little disturbances there might be on the way, it just goes along them. Straight, no Chaser, as they say...
So the seemingly radical direction change around the black hole does not actually require change of momentum... ;)
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hitting some relitively minor things you seem to have misunderstood:
"huh?"
photon's momentum is defined as p = hf/c, matter's momentum formula I was always taught to be p = mv. so momentum for a photon is deined diferently... than it is for mater, is what I meant.
"And, insanely huge black holes wouldn't be the size of a marble."
I said insainly huge mass, I was thinking something the size that could fit on a table top, a black hole with a EH of a half inch across would have the mass somewere around that of the earth wich for something sitting on a table is insainly huge, though by blackhole standards is rather pathetic.
that hole post was a tangent thought about a relitivly diferent situation, trying to break conservation of momentum.
so if I were to fire a hypothetical laser at a hypothetical black hole in such a path that it were to make a pass around it and hit my laser (wich is made from some hypothetical substance that would reflect all light, thus not blow it'self up). when the beam comes back around and hit's the laser what would happen? both to the laser and the black hole.
sence the photon has no mass and thus no gravity, it's just folowing the bends in space, so it should have no effect on the black hole, at all, if I fired a quatrillion yattawatts worth of energy in the form of photons past an object you would not be able to tell unless the beam hit the object (in wich case it would probly explode), there would be no gravitational effects, and there would be no visable change to the object so long as none of the photons hit the object. right?
so a photon going around a black hole will not effect the black hole in even the slightest degree. but when it hits the laser wouldn't it interact with the atoms of the laser get absorbed and reemitted imparting momentum in what would seem the opposite diretion that wich it was fired from?
isn't this a loophole here?
the geometry of space is deformed such that it twists back over it'self but in a diferent direction when the photon travles strightly through this deformed space it will end up going through the same reagon of space but in the opposite direction. the beam did not bend, truely, but it is hitting it's own emmiter, and imparting momentum in a direction that is, from the emmiter's point of view, in the opposite direction that it had fired the beam earlier. right?
now consiter a similar situation on a smaller scale were you have a small black hole in some sort of containment feild (held in place with electrostatic forces or something) inside a machine and a powerful laser is fired to just miss the event horison causeing the beam to double back (note: I understand the bending of space/photon travleing straight through non-straight space thing, but to simply describe it as it would be seen from an outside observer makes explaining the situation a lot clearer), like before, hitting the laser (without destroying it) this is just like the previous situation exept the black hole and the laser are held together so they move with each other.
from what you were saying it sounded like when the beam hit it would pull the laser in the direction opposite the beam was travleing, which makes me think I didn't follow you properly.
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It's like what I said about the Perpetual motion machine: I'll have to see it to believe it.
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I think dismissing it as a flight of fancy is a little off.
This is clearly a working technology, and while it won't become the core of a double decker bus tomorrow it does have potential to be developed.
Ditto. The lot of you who are quick to dismiss something as bollocks are what's holding back a lot of potentially revolutionary discoveries. Just as radical thought is dangerous, such also is conservative.
... And we have seen how many of these threads, 5013, and how many have turned out to become actually working technology? We're lucky if even one.
The burden of proof is on the inventor to prove his concept right and working, and as the concept sounds wacky I will find skeptism very healthy.
So? By restriction spread of the idea and immediately writing it off as bollocks, you potentially crush the one in five thousand that does work.
No I do not. My skeptism is just skeptism - it does not define reality, it does not restrict the spread of idea. Only thing it - combined with others' skeptism - is to place a burden of proof on this guy. If he can prove it, fine - then this guy is a genious and I am wrong. If he can't, well - no one has lost anything.
However, I don't take Superb Science Breakthrough Science Magic Threads any more seriously than Homeopathy, Body Toxins and stuff like that, because 99,9% of time it's just complete crap and the rest just suits the margin of error. If someone told you that this very night you can observe UFOs and he had told you that 1000 times earlier and every single time he had been wrong, would it really be dumb to write him off this time? Bad analogy but still.
Edit: I see
VVVV
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Well, the business with existing particle accelerators proves that the theory behind this engine needs investigating. Whether it actually works or not in a practical sense has yet to be seen.
What's happening in this engine is that kinetic energy is imparted to the cavity via microwaves. Energy is converted from electrical to kinetic with minimal intermediary stages. Conservation of energy is satisfied.
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Electric to Kinetic transfer is one of the most innefiecient transfers of energy though.
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hitting some relitively minor things you seem to have misunderstood:
photon's momentum is defined as p = hf/c, matter's momentum formula I was always taught to be p = mv. so momentum for a photon is deined diferently... than it is for mater, is what I meant.
Actually... If you want to get technical, the definition of momentum is the excact same for both photons and particles with mass.
For a particle, momentum is always
p = mv.
Photon's mass comes from equation E = mc^2 -> m = E/c^2.
Photon's energy is E = hf.
Photon's speed is c.
So, photon's momentum is
p = mv = E/c^2 * c = E/c = hf/c = h*lambda
lambda there is photon's wave length...
Alternately, because all particles have also characteristic wave length (deBroglie wave length), EVERY particle's momentum can also be defined as
p = h * lambda
where lambda is particle's deBroglie wave length.
"And, insanely huge black holes wouldn't be the size of a marble."
I said insainly huge mass, I was thinking something the size that could fit on a table top, a black hole with a EH of a half inch across would have the mass somewere around that of the earth wich for something sitting on a table is insainly huge, though by blackhole standards is rather pathetic.
Right. :)
that hole post was a tangent thought about a relitivly diferent situation, trying to break conservation of momentum.
so if I were to fire a hypothetical laser at a hypothetical black hole in such a path that it were to make a pass around it and hit my laser (wich is made from some hypothetical substance that would reflect all light, thus not blow it'self up). when the beam comes back around and hit's the laser what would happen? both to the laser and the black hole.
The laser would gain momentum backwards when it sent the photon on its way; then it would get the same momentum again when the photon, after going round the black hole, hits it and is absorbed.
However, as to whether or not the black hole is affected by photon through gravitation, well that's more difficult question. Theoretically, all energy bends space-time continuum - and since photon has energy, it should also do that... but I must admit that in this phase things are starting to get a little past my current knowledge. I have perceptions but not actual knowledge at this level. :)
sence the photon has no mass and thus no gravity, it's just folowing the bends in space, so it should have no effect on the black hole, at all, if I fired a quatrillion yattawatts worth of energy in the form of photons past an object you would not be able to tell unless the beam hit the object (in wich case it would probly explode), there would be no gravitational effects, and there would be no visable change to the object so long as none of the photons hit the object. right?
You must then remember that in fact every object in curved space time just travels along straight line.
An object seemingly under gravitational influence does not in fact feel any force excerted upon it in any situation. Gravitation force in general relativity is much similar to centrifugal force; it's an apparent force created by differences in co-ordinates... in centrifugal force, rotating reference frame causes apparent force; in gravitation, twisted reference frames (that appear to be straight!) cause apparent gravitational effects such as falling.
As Mr. E noticed: You don't feel your weight when you are falling...
so a photon going around a black hole will not effect the black hole in even the slightest degree. but when it hits the laser wouldn't it interact with the atoms of the laser get absorbed and reemitted imparting momentum in what would seem the opposite diretion that wich it was fired from?
isn't this a loophole here?
the geometry of space is deformed such that it twists back over it'self but in a diferent direction when the photon travles strightly through this deformed space it will end up going through the same reagon of space but in the opposite direction. the beam did not bend, truely, but it is hitting it's own emmiter, and imparting momentum in a direction that is, from the emmiter's point of view, in the opposite direction that it had fired the beam earlier. right?
now consiter a similar situation on a smaller scale were you have a small black hole in some sort of containment feild (held in place with electrostatic forces or something) inside a machine and a powerful laser is fired to just miss the event horison causeing the beam to double back (note: I understand the bending of space/photon travleing straight through non-straight space thing, but to simply describe it as it would be seen from an outside observer makes explaining the situation a lot clearer), like before, hitting the laser (without destroying it) this is just like the previous situation exept the black hole and the laser are held together so they move with each other.
from what you were saying it sounded like when the beam hit it would pull the laser in the direction opposite the beam was travleing, which makes me think I didn't follow you properly.
I suppose that the beam of light does in fact have effect to momentum of black hole, at least if the conservation of momentum holds... but the effect only is measured in laser's reference frame.
What happens is that when laser emits a photon, it gives photon momentum and gains itself same amount of momentum to opposite direction.
When the photon rotates the black hole, it does a loop in laser's reference frame, so from laser's point of view the black hole alters the photon's path; thus in laser's reference frame, the photon must also affect momentum of black hole. In black hole's point of view, the photon doesn't affect it; in photon's POV the black hole doesn't affect it. Only in laser's reference frame (and others, but we are on laser frame measuring things) there is an apparent interaction between two objects.
But, in photon's point of view it goes along straight path, the starting point and ending point just happen to be the same ones in Laser's reference frame.
In GR, there are much of these seemingly paradoxal "physical loopholes", but eventually when matters are viewed from all co-ordinates, things usually sort out mathematically, even if they wouldn't do it logically... :D I've not yet had the pleasure to actually familiarize myself with actual mathematics of general relativity, and I suspect it won't be just dancing on the roses... :nervous:
AS I said, it gets muy complicado at these levels of physics, even if the basic principles are quite simple... :shaking:
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it looks like he found a way to exploit one of theese physics loopholes. this device might be the first of many usefull devices that will exploit them. we must find them all and use them to our advantage, and hope we dont break the laws of physics in the process. :D
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it looks like he found a way to exploit one of theese physics loopholes. this device might be the first of many usefull devices that will exploit them. we must find them all and use them to our advantage, and hope we dont break the laws of physics in the process. :D
Laws of physics can easily be broken.
Laws of nature can not be broken by definition. Never ever.
Physics is a composition of man-made concepts that try to describe actions and reactions occurring in nature... if it cannot describe something accurately, or something which obviously happens seemingly breaks the "laws of physics", than the obvious solution is that the particular "law" of physics was inaccurate... or downright wrong. ;)
In a way, quite a few applications use "loopholes" in old theories.
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but of course, contrary to popular belief, im not exactly stupid :D
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but of course, contrary to popular belief, im not exactly stupid :D
how would we know
BAMM ZINGG BURRRRN
j/k bro
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At first glance, it sounds like another cold fusion project. But, as im just a layman with pretty much 0 knowledge in physics besides basic stuff (if i trip there is this strange force that pulls me to the ground) i cant say one way or the other. It would be cool though... kind of like the fly-by-wire of propulsion.
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On the other hand, I wouldn't be too quick to judge this project... creating thrust from electricity isn't actually that new a discovery.
Biefeld-Brown effect in action (Jean-Louis Naudin's lifters) (http://jnaudin.free.fr/lifters/main.htm)
(http://jnaudin.free.fr/lifters/hexalifter/images/hexalift3.jpg)
(http://jnaudin.free.fr/lifters/maximus2/images/maximus260s.jpg)
That's something really intriguing.... The concept consists of an asymmetric capacitor that apparently generates lift when power is turned on to create a electric potential (charge, if you will) between upper and lower part of the capacitor... They demand about 30-40 kV voltage, but they really seem to be flying... :shaking:
I don't know how the hell it does it, really. It's apparently not even propelling air or anything downwards, it's just... lifting. :confused:
It feels like baron von Munchausen lifting himself by tugging his hair and thus saving himself from drowning in a swamp. I wonder if they have tested the effect in vacuum? At least they have proposed the use of asymmetric capacitors as maneuvering thrusters for satellites (http://technology.nasa.gov/tops_detail.cfm?pkey=2200095&category=TOPS)... They are in fact the same thing as those lifters. The same thing can be found here (http://jlnlabs.imars.com/lifters/act/html/omptv1.htm).
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Now that's interesting. Never heard of it before, but it's way cool. There's even instructions for building your own... almost makes me wish I was back in college so I could nag my physics teacher about spending some lessons building one :)
The really interesting thing is though, that as far as I could read noone really knows why it works, they just know that it does. And mysteries like that are what makes science worthwhile to keep up on.
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if theese things are so common, wtf arent we using them already?
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I'm thinking the fact that they require 30-40kV to work, and clearly need a lot of capacitors drawing that to lift just 60g. Kinda not very handy, having to lug around a nuclear powerplant just to make your car hover.
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remember folks, Feasable from a scientific perspective is one thing, Feasable from an Engineering perspective is another.
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after some research on those other devices i can understand why were not using them, we have motors that can do the job many times better, and they dont work in space because theres no atmosphere. still the emdrive, as its called, has some potential.
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sort of like an atmosphereic ion drive.
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A repulsive force between two plates is not quite the same thing as a force applied to the whole system. The emdrive is not in the same league as the capacitor-based lifter for this reason.
Also, simple magnetism is a more powerful lifter than capacitance. The difference is that an electromagnet requires current, while that capacitor just requires charge. if you can stop it leaking, it requires almost no actual power.
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after some research on those other devices i can understand why were not using them, we have motors that can do the job many times better, and they dont work in space because theres no atmosphere.
Um...
They do.
At least that's what is claimed on this page: This apparatus has been tested in June 2001 by Transdimensional Technologies in the vacuum chamber of the NASA Marshall Space Flight Center ( MSFC ) in Huntsville (http://jlnlabs.imars.com/lifters/act/html/2dacap.htm).
I suppose they really have tested it.
The thrust doesn't seem to be generated by throwing anything "backwards" in this case, despite the utter wierdness of that as concept. Like I said, these things are the true von Munchausens, lifting themselves in air by pulling themselves from hair. :confused:
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damn them things are cool. hook a bunch of those up to a nuke reactor and call it a space ship. :D
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Does that gizmo need a gravity field to repel against, If so do we need to tie a moon to the arse of the gadget?
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arr, this thread was already complicated and now in pirate talk :(
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this is now well funny thread :)
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Picture 3 Pirates sittin' round a table in a bar....
If we discount th' fact wot this 'ere 'ere is in blatant violation o' all physics (mainly th' conservation o' momentum, which in many way is th' physics, this 'ere 'ere kind o' technique would have several major advantages in space travelin', compared t' rocket engines or ion engines or anythin' wot uses propellant t' create equal an' opposite force. This 'ere 'ere law says wot th' momentum o' a closed system is constant, period...
:lol:
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after some research on those other devices i can understand why were not using them, we have motors that can do the job many times better, and they dont work in space because theres no atmosphere.
Um...
They do.
Disregard my last...
I have gotten information that suggest that these things indeed do not work in vacuum - unless you pour ionized gas into vacuum chamber, which kinda negates the whole idea of a vacuum.
Regardless of that qualm, it would be interesting to actually build a functional lifter... Hmm, I've got an old Sony Trinitron TV sitting right there... :drevil:
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Space isn't a perfect vacuum though, especially near the earth. I wouldn't be surprised if they could still be useful for stationkeeping and minor maneouvering for satellites, since those things can be done quite well with just miniscule amounts of constant thrust over several weeks or months.
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Not a chance. It's bloody well enough vacuum to have so little density that it wouldn't really generate any thrust.
So, effectively, these things are nothing more than a primitive ion engine - which was already utilized magnificently in Deep Space 1 probe, for example.
In atmosphere they just use the ionized air molecules as propellant - not unlike jet bypass engines (and traditional propellers of course) use mainly air as propellant, while rocket engines use only exhaust gases, and similarly ion engines have their own propellant ion source with them.
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It wouldn't need to generate any significant thrust to still be useful for stationkeeping. Consider that the ISS for example has a low enough orbit that it is constantly subjected to atmospheric drag, so there's definitely something there. Now, the ISS in particular doesn't need it since anytime a spacecraft docks, they spend their reserve fuel boosting it. But for satellites in a similar or lower orbit it might be workable, as they'd only need a couple of grams worth of thrust to counteract the drag if said thrust could be maintained for months on end.
It could definitely never be used for anything sudden, such as docking operations between the shuttle and the ISS, but stationkeeping is a different ballgame.
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I don't think they could be used in tat purpose even.
Even negating the effect of air drag with these lifters in mentioned air pressures would most likely need so much power that the ISS's panels wouldn't be able to produce that much energy.
If they really did work in vacuum with same lift capacity as they do in atmosphere, then it would be a different matter altogether. But, as things seem to be, you would need to give them ion supply (propellant) to use in the thrust-generating process, and ion engines would do the same thing more efficiently.
Anyway, it is actually easy to test whether or not these things are based on conservation of momentum or some currently unknown principle producing lift from electric potential.
1. build a functional lifter.
2. build a thin-walled box (ie. from light wire and plastic foil). Make sure that the lifter can actually lift the weigh of the box - just set the box on top of your lifter and if it can keep both of them aloft, it's time to do the actual experiment.
3. Place the lifter inside the box.
4. Turn on power. The lifter should rise to the roof of the box; what happens after that defines the quality of the thrust produced.
4a. If the lifter stops to the roof of the box and doesn't lift the box (remember that the capacity of the lifter would lift the box), then it's because of the fact that the box is sufficiently closed system that even though the lifter lifts itself inside the box, the box-lifter system doesn't propel anything downwards and thus doesn't rise.
4b. If the closed box rises with the lifter, then it is indeed some unclear principle causing thrust that makes it possible for the lifter to lift the combination.
Simple and easy experiment. Also applies to this new kind of thrust producing device mentioned in pening message of this thread.
It's simpler to arrange than a high quality vacuum chamber, too. And cheaper...
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after some research on those other devices i can understand why were not using them, we have motors that can do the job many times better, and they dont work in space because theres no atmosphere.
Um...
They do.
Disregard my last...
I have gotten information that suggest that these things indeed do not work in vacuum - unless you pour ionized gas into vacuum chamber, which kinda negates the whole idea of a vacuum.
Regardless of that qualm, it would be interesting to actually build a functional lifter... Hmm, I've got an old Sony Trinitron TV sitting right there... :drevil:
got a link? ive been curious about theese things sence you posted them and my research indicated they did work in a vaccume. am i missing something?
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Well.
I've actually gotten controversial information about these things.
Obviously, the web pages say they should work in vacuum as well as in atmospheric conditions. Otherwise, there's no clear experiment results seen that I could easily found.
However, Jean-Louis Naudin has apparently been behind multiple other... interesting... things that have turned up more or less fraudulous. Things like cold fusion, water fuel, the usual free-energy stuff that does not exactly invoke my trust. Thus, I have my doubts of whether it works or not.
So, some claim it works, some claim it doesn't work.
The only SURE way of knowing would be to conduct an experiment myself, and I might actually do just that some day.
It's simple really. The experiment I described earlier would define without a hitch whether the device uses conservation of momentum to produce thrust or takes advantage of som unknonw phenomenon.
Put the lifter into a closed box and measure the weight of the box when lifter is on, and when it's off. When the lifter is turned on, it should rise to the roof of the box.
However, if the device works along conservation of momentum, the box will still weigh the exact same as when the device is off.
This experiment would pretty well tell whether or not it would work in vacuum as well, because if it "lifts" the box (ie. reduces the weight of the closed box), then it seemingly breaks the conservation of momentum, and then it would also work in vacuum in this case - though I doubt this scenario.
This experiment would be relatively easy to do with a sensitive scale to measure weight. Only difficulty would be to aquire high-voltage supply. I'm not actually comfortable with meddling with CRT monitor/television PSU's... :nervous: But on the other hand, it seems that net pages really cannot be trusted in this kind of matter. I would have to do the experiment myself to be sure of the results in one direction or another.
And perhaps, perhaps I will, too.
It's getting into me... Perhaps I will build the device and perform the experiment in physics student laboratory in Otaniemi. I bet I could find a high voltage supply there - different thing is, would I be allowed to use it. :drevil:
Be assured that this forum will be one of the first places I'll post my experiment's results. I know how to make the experiment; the only thing I'm lacking is high-voltage PSU - that is, if I don't disassemble that television sitting on my desk one metre on my left. :shaking:
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the device doesnt seem like it would be hard or expensive to construct. i believe you could get the power requirements nessicary using a transformer to step up the voltage. alot of current isnt neccisary. the page was rather good at giving proper schematics/specifications to build off of. it would be intresting to see the expierement myself.
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Build one then :nervous:.....................
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BTW Did you guys see this article here (http://www.metro.co.uk/weird/article.html?in_article_id=19840&in_page_id=2)
Space travel could become a helluva lot cheaper! 8)
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1961.........
http://hypertextbook.com/facts/1997/CassandraEng.shtml
manned flight to outer whatsname......