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Comments: 392 + - Science: How To Build a Quantum Propulsion Machine on Friday December 11, @11:02AM
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KentuckyFC writes "According to quantum mechanics, a vacuum will be filled with electromagnetic waves leaping in and out of existence. It turns out that these waves can have various measurable effects, such as the Casimir-Polder force, which was first measured accurately in 1997. Just how to exploit this force is still not clear. Now, however, a researcher at an Israeli government lab suggests how it could be possible to generate propulsion using the quantum vacuum. The basic idea is that pushing on the electromagnetic fields in the vacuum should generate an equal and opposite force. The suggestion is that this can be done using nanoparticles that interact with the vacuum's electric and magnetic fields, generating the well-known Lorentz force. In most cases, the sum of Lorentz forces adds up to zero. But today's breakthrough is the discovery of various ways to break this symmetry and so use the quantum vacuum to generate a force. The simplest of these is simply to rotate the particles. So the blueprint for a quantum propulsion machine described in the paper is an array of addressable nanoparticles that can be rotated in the required way. Although such a machine will need a source of energy, it generates propulsion without any change in mass. As the research puts it with magesterial understatement, this might have practical implications."
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This can be done using nanoparticles (Score:5, Funny)
I bet this could be done even easier with cats, but the ASPCA people won't like it.
Re: (Score:3, Funny)
Not to mention the International Buttered Toast Society.
Re: (Score:3, Funny)
Dean drive?
Dean ... Venture?
Re: (Score:3, Insightful)
Without that, there's nothing to define how much you have accelerated, nothing the crafts own frame can relate to, so constant power into such a system ought to create constant force. With a fixed mass, that means that you're putting kinetic energy into the system linearly with respect to speed, but gaining kin
Re: (Score:3, Insightful)
Using gyros to change attitude of spacecraft is reactionless
It is not. The spacecraft is rotated one way, and as a reaction the gyro is rotated the other way.
If you have to put something into a system (like, say, electricity) to get something out (like, say, motive force), then that's not against the laws of physics, or even remotely technically difficult.
It doesn't matter how much you put into a system, you still have to balance momentum, or you're breaking very fundamental laws. You can not create momentum in one direction without also creating an equal momentum in the opposite direction.
So , , , (Score:3, Funny)
Vacuum doesn't suck, it pushes?
Re: (Score:3, Informative)
FTFY. Now queue the Spaceballs jokes.
Re:So , , , (Score:4, Funny)
Colonel Sandurz: It's Mega Maid. She's gone from suck to blow!
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Call me pedantic but... (Score:3, Insightful)
Re:Call me pedantic but... (Score:5, Funny)
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Re:Call me pedantic but... (Score:5, Informative)
It turns out that there is no such thing as a classical vacuum. Instead, you have a state where particle/antiparticle pairs are spontaneously created and destroyed with typically net zero force. So, the definition of vacuum has been reformed.
-l
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Re:Call me pedantic but... (Score:4, Funny)
So... you're saying that nothing's impossible? Or just that we ain't seen nothing yet?
Nothing is sacred! Bow down before it!
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Re: (Score:3, Informative)
Alternatively (if you're talking about the other particles), see the other response.
Those daring men in their quantum pushing machines (Score:5, Insightful)
Well.
A non-reaction mass drive. That makes my head hurt. It just gave a slight air of plausibility to a few million bad SF novels.
Re:Those daring men in their quantum pushing machi (Score:4, Funny)
With due apologies to the authors if this estimate turns out to be a gross underestimate.
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Momentum Conservation (Score:4, Interesting)
I call shenanignans!!
Re:Momentum Conservation (Score:5, Informative)
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Re: (Score:3, Informative)
Quantum fluctuations of the position or of the magneto-electric constant of particles do not affect the average value of their momentum, as a consequence of the conservation of momentum law. A propulsion engine may be designed by using for instance an addressable array of small magneto-electric particles or wires. Rotating (see Fig. 1) or aggregating (see Fig. 2) these particles will result in velocity:
He brings up attitude control of satellites as an example because, I think, it's a situation where very small amounts of momentum do useful work (you only need to rotate the satellite by a degree or so a day, he says). He's definitely talks about propulsion in the body, not just orientation.
As reactionless drives are very much Weird Science, not mentioning propulsion in the abstract could well be entirely deliberate to make the article more
Re: (Score:3, Informative)
If you would read the article (a high order, I know), you would realize that, with quantum mechanics taken into consideration, there is no such thing as a classical vacuum. Hell, you could probaby get that just from reading the summary.
Re:Momentum Conservation (Score:5, Informative)
The issue with the theory is that it violates the Newtonian rule of conservation of momentum.
No it doesn't. As Maxwell figured out long ago, EM field can carry momentum.
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Re:Momentum Conservation (Score:5, Informative)
An EM field can carry momentum, but this allows the momentum to go in only one direction.
If I emit an EM field, it is pushing back against me as it emits (albeit VERY gently). When the EM field hits something, it imparts some or all of that momentum to the object it hits. The conservation of momentum has been maintained, because there are equal and opposite forces.
Normally, drives do one of two things to move the object they are trying to move. They either eject mass at speed in the opposite direction (rockets) which involves the loss of mass or push against something like ground or air (wheels in a car, propellers on a plane) to pull themselves forward.
In a frictionless vacuum, the only known propulsion system that works is a mass-ejection system like a rocket. You have nothing to push against that a friction drive needs, so you have to bring your own mass and throw it out to gain momentum. As you use your propellant mass, you lose it, so you have to carry some sort of mass and some sort of way of throwing it out really fast so you make the most of every gram of mass you eject.
What this new theory is suggesting is that I can get the momentum for the cost of pure energy at one end, then use that momentum on the other end of the transaction for motion. Normally, I'd either have to have something to push against that would move back in the opposite direction as a result (or would be so huge that the opposing force would be negligible), or I'd have to eject mass.
This drive would do neither - it's like pulling yourself up by your own bootstraps (quite literally) then using the energy of your pulling to allow you to move through the air. The conservation of momentum, equal and opposite reactions, etc - poof - all gone. This is truly a non-Newtonian drive in that it appears to break fundamental laws of Newtonian physics.
Unless, of course, there is something that is "absorbing" the other side of the "equal and opposite" reaction, something outside our ability to perceive at this point, in which case this is a friction drive, we just haven't figured out what we are pushing against yet.
Or, alternatively, the theory may be complete crap. That's possible too. :)
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Re:Momentum Conservation (Score:4, Interesting)
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Re:Momentum Conservation (Score:5, Insightful)
Yes it does. The field is generated from the virtual particles in the vacuum, not from the ship. It is that field that they add momentum to -- the article explicitly mentions doing this -- adding equal and opposite momentum to their ship. They aren't trying to 'drag' the quantum vacuum field along with them. That would be impossible, not a method of propulsion, and violate conservation of momentum. The actual idea, however, does not.
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Re:Momentum Conservation (Score:4, Insightful)
It would be if Charlie Daniels is right. Or that that was what he was saying.
Maxwell says you can conserve momentum and still gain propulsion by emitting radio waves.
BTW, that isn't the laws of thermodynamics, more like the laws of motion. It's a momentum and energy not being the same thing and each having its own conservation law, sort of thing.
But take heart. Most jokes are funny not because they are right, but because they follow the syntactic and semantic patterns of jokes. Same deal with Republican political slogans. Total bullshit, but excellent clap-trap.
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Re:Momentum Conservation (Score:5, Insightful)
You can't change the momentum of the vacuum.
"You can't see moons around Jupiter. If there were, it would mean the Earth isn't the center of the universe." (Galileo's critics really said this.)
"You can't sail across the Atlantic to China. If you could, it would mean the Earth was round" (many, many errors on all sides of that statement!)
"Anyone who is talks about the practical uses of nuclear power is talking moonshine" (Rutherford in 1920, more-or-less.)
Scientific progress is the process of tearing down previously believed truths as well as discovering new, hopefully somewhat less contingent truths (although of course non-zero contingency always remains, which is a big deal to philosophers,mathematicians and other insane people, but not something anyone else cares very much about.)
People who have done actual calculations, rather than an arm-chair analysis on /., think that it is possible to change the momentum of vacuum modes, thereby making them non-vacuum modes (one would presume) by introducing asymmetries from rotating magneto-electric materials and in various other ways.
Introducing asymmetries has long been know to produce real particles from the vacuum. One of the most dramatic theoretical instances of this is a step-function potential with more than twice the electron mass. If you solve the Dirac equation in this situation you get weird phenomena like negative transmission and reflection coefficients that are negative or greater than unity.
The explanation is that such a large potential (so long as the step occurs over a scale of less than the Compton wavelength of the electron, which is about a pico-metre) has the ability to separate the virtual pairs that make up the "Dirac sea", thus turning them into actual particles (at the cost of the required amount of energy). If you could actualize this you could then accelerate the electron and positron to fire them off in the same direction, giving your apparatus a push in the process. At the most abstract level, what these guys are proposing is no different from that.
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Fourmilab (Score:5, Informative)
MOD PARENT UP (Score:5, Insightful)
This is exactly what they're saying. A quantum propeller.
You push off of stuff that already exists in space to move forward, instead of having to throw stuff backwards to move forward.
The KEY is that space is not a true vacuum. It is a "working fluid" in the sense that you can push at it with magnetic fields. It can be interacted with.
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Is this different from a photon drive (Score:5, Interesting)
Is dumping momentum into the quantum vacuum different from emitting photons carrying the same momentum? If not, this is just a photon drive, which is a well known concept, has brilliant specific impulse but is incredibly energy-inefficient except at high relatavistic velocities.
Re:Is this different from a photon drive (Score:5, Informative)
Red this short article about "vacuum propellers" (props to RedJesus for finding the article):
http://www.fourmilab.ch/documents/vprop/ [fourmilab.ch]
You don't have to "emit" anything, you just set up magnetic fields to push against the "vacuum" of space, which is not at all a true, classical vacuum (it contains little fields all over the place). It's like the ocean, a force that can be interacted with. A "working fluid".
And since we're talking electromagnetism, a really strong force in the grand scheme of things, maybe this will be a lot of energy efficient that simply throwing almost-massless particles out your rear.
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Re: (Score:3, Informative)
I did read that article. It didn't answer the question. The quantum vacuum consists of (at the energy levels we're dealing with) virtual photons. If we're giving net momentum to these virtual photons I think that is the same thing as there being real photons travelling in the appropriate direction. So, you move some charges and magnetic dipoles around, and you photons start moving -- how is this different from emitting something from an antenna?
And all electromagnetic forces are carried by photons so there
Re:Is this different from a photon drive (Score:4, Informative)
Since it is a momentum-transfer (hence, reaction) drive, it would seem to face the same constraints as any such drive imposed by conservation of energy, so in the ideal case, it would perform exactly the same as an ideal photon drive. Of course, engineering efficiencies might, in practice, favor one over the other, but even an ideal photon drives has an enormous input power to thrust ratio on the order of 300MW per Newton of thrust.
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Boy did I read that headline wrong (Score:4, Funny)
How To Build a Quantum Propulsion Machine
At first glance I thought it said How To Build a Quantum Popsicle Machine. Then I thought Quantum Popsicle would have been a great name for a hair band in the 80's.
You could have flavors like Lime Quark and Strange Berry, put the stand up outside the Hadron Collider.
Reactionless drives (Score:3, Interesting)
A reactionless drive would be nifty because it can gather kinetic energy very easily (that's what makes travel so cheap with one). However, there's a darker side to that coin. If you can accelerate a ship to near-c with little difficulty, there's not much stopping you from extorting the Earth by threatening to drop the ship (or for that matter, a bunch of tungsten telephone poles traveling at
Any propulsion system can be used as a weapon. Thus, the good news of the reactionless drive is that one can easily move about in space. The bad news is that one will have to.
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Considering most other forms of theoretical space propulsion are accomplished with either controlled explosions (the bigger the better) or exceedingly large lasers, this seems relatively safe. Besides, sending something up to .99c still takes an extreme amount of energy, even if the system were 100% efficient (which I highly doubt) getting any sizable object up to that speed is going to take a massive power supply; massive enough that it could probably have been used more directly if you wanted a weapon.
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Just out of interest:
A telegraph pole is ~10m long and about ~0.2m wide. Cross section: 0.03m^2. Volume: 0.3m^3.
The density of tungsten is 19300 kg m^-3, so your tungsten telegraph pole masses about 6000kg.
The relativistic momentum of an object is (m v) / (1 - v^2 / c^2)^-2: 13e13 Ns.
The relativistic kinetic energy of a mass is (p^2 c^2 + m^2 c^4)^-2, where p is the momentum: 4e21 joules.
Assuming I've got my maths right, which given that it's late on Friday afternoon is highly questionable, that i
Re: (Score:3, Interesting)
Uuum, wouldn’t it be more like a machine that constantly digs up some soil, and throws it behind itself, to accelerate?
Of course, here the “soil” constantly digs itself up. But you’re still “taking that “stuff”, and throwing it behind yourself. It just happens to zero itself out after this, if I understand it correctly.
I would bet money, that we will get some very interesting effects and new science out of even trying this.
Like finding out why it does not work. Or w
Why did noone tell me it was the future? (Score:5, Interesting)
Does it mean that I am old because I look around every day and it feels like I am living in a surreal sci-fi story?
Reactionless drives, energy weapons, smart phones, robotic killing machines, genetically engineered super species? At this rate I wonder if I would be surprised when practical AI or faster than light travel becomes an option.
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This isn't the future. There are no aircars.
The solution is simple... (Score:4, Informative)
Feigel's had this bee in his bonnet for years. (Score:3, Interesting)
See this item from 2004: [erols.com]
Something to consider: (Score:4, Interesting)
The paper is a one-author publication in a non-peer-reviewed journal and doesn't seem to be published anywhere else. The author's affiliation is an applied R&D institute not an academic institute with a strong theoretical background. I'm not saying that discredits it, but it certainly means that it should be taken with a grain of salt. I would suggest that anyone who wants to assess the merits should read through some of the references (which are good publications) and see if the present article appears plausible. Even without any technical expertise, the abstracts could probably provide a feel for the state of the art.
I couldn't be bothered to do that reading myself, but I would suggest that any momentum transfer to the vacuum would involve the production of real particles from the zero-point fluctuations. Conservation of momentum demands that there would be something carrying momentum in the opposite direction of the spacecraft and, by definition, it can't be an unexcited quantum field. There would have to be excitations of the field to carry the momentum (real particles).
Re:what are we talking here?! (Score:5, Informative)
That's not at all connected. What you are thining of is as velocity of an object increases its mass will increase (this is actually a little more complicated. This is only true for things with positive rest mass. If you have zero rest mass for example then this doesn't happen, but you will always be traveling at the speed of light anyways. If you are a tachyon and hus have imaginary rest mass and move faster than the speed of light in a vacuum then what happens as you change velocity is more complicated). This will still happen. The key to this sort of drive is that you don't *lose* mass as part of your reaction. Rockets, ion engines, and pretty much every other method of moving things requires you to push against something else to move. A rocket works by sending out particles from one end and so conservation of mass forces it in the other direction. An ion engine works the same way but instead of using hot fast particles uses little ions accelerated by a magnetic field.
The key to this sort of engine is that it doesn't do that, It can accelerate without throwing off mass. But the object will still gain mass as it accelerates nearer to the speed of light. In practice, the second part really won't matter for any practical engine since we will be moving so much slower than the speed of light. The key idea at some level is that you don't need to lose fuel to accelerate (you just lose energy).
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Re:what are we talking here?! (Score:4, Interesting)
Well technically the car is losing a slight bit of mass because of the energy change, but that's not relevant to the propulsion, a car isn't a rocket. The car is pushing against the earth and transferring that momentum to the earth.
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Re:what are we talking here?! (Score:5, Informative)
Thanks for the thorough information. How does this throwing off mass thing relate to electric cars? Do electric cars accelerate without loosing mass?
It's not about losing mass necessarily, it's about Newton's 3rd Law / Conservation of Momentum. For something to accelerate forward, something else (the surface of the earth) must accelerate in the opposite direction such that momentum is conserved.
The concept of Conservation of Momentum and rocket propulsion is often explained using the analogy of a boat on the lake with a bunch of rocks in it. If you throw rocks off the back of the boat, conservation of momentum means your boat will be propelled forward. Now, that's a pretty silly way to propel a boat when you can just use a paddle or propeller to push the water backwards and your boat forward.
Rockets in space don't have that luxury. So they pretty much have to carry a bunch of "reaction mass" with them and throw it at high speed out the ass end of the rocket.
This invention, if it pans out, would be more like a propeller for spacecraft, pushed by and pushing against the short-lived particles that spring in and out of existence in vacuum. I have to imagine that the amount of thrust would be miniscule, but not having to carry reaction mass would be a huge advantage.
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Re:Implications? (Score:4, Insightful)
Well you're not going to get to a decent fraction of light speed if you need to squirt stuff out of the back of a rocket. A propulsion system that doesn't depend on squirting stuff out of the back of the ship opens up all sorts of possibilities.
E.g. a spaceship that could accelerate at 1g would have all sorts of useful properties. Firstly 1g feels like gravity. Secondly you could zip around the solar system pretty quickly. Last but not least, due to time dilation you could circumnavigate the known universe in 50 to 100 years ship time. Of course back on Earth millions of years would pass so the trip would be one way. Still you could imagine making decades long (I guess, I'm too lazy to do the math) trips to a star like Sirius.
Actually I like the idea of sending out a plague of self replicating machines in devices like these, to bring the Word Of Dawkins to the stars and troll the inhabitants of other star systems.
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Re:Implications? (Score:5, Informative)
If a spacecraft carries reaction mass, the total mass of the spacecraft is increased by the amount it is carrying at any one time. This mass must also be accelerated and decelerated. So the more you carry, the more you spend because you're carrying it. There are various side effects too, for instance, since the vehicle's mass changes over time, course change calculations have to keep track of that. Also, for every bit of mass you have to carry that is fuel, that's less cargo you can move from point A to point B.
If you have an energy source that is relatively mass constant - a nuclear reactor, or a set of solar panels - and you can piddle along without any tanks full of "stuff", you're going to be able to carry more payload; you're going to be able to go a lot longer without "refueling"; you're going to have more freedom and more range. Headed for asteroid X? Something interesting over there on Asteroid Y? No bothersome fuel constraints, you just go and take a look. That's the kind of benefit that has very positive ramifications.
The reason reaction mass is used in space is because in a vacuum, one has to push against something in order to move. That's the role of the reaction mass. You spend energy in X direction and get sent off in the -X direction with the same amount of energy.
Think of how a nuclear sub works underwater. Because it has something to push against (water), its ability to move is constrained only by the degree of push it can generate - it doesn't have to carry anything to push against, it's surrounded by water that will serve the purpose. The reactor provides a lot of energy to push with, using a propeller, which is designed so as to create a forward vectored force when spinning in the water. That's what the article suggests for space craft; that there is something there to push against, and therefore, one doesn't need to carry reaction mass. Spaceships using this method would be very much analogous to that nuclear submarine.
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Re: (Score:3, Informative)
No. Think of the virtual particles as a loan that *must* be repaid. The more that is loaned, the quicker that it must be repaid. electron/positron virtual pairs exist for a loner time than say virtual proteon/antiproton pairs do. There is no way to use the creation of virtual pairs to create free energy or break the conservation laws.
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Your fuel source does not change its mass. The gas in your tank combines with the local air and releases pollutants into the air. Furthermore, it achieves actual movement by turning a wheel which interacts with the ground.
A spacecraft has no ground to interact with. Rockets produce movement by throwing away their mass. This engine (if it works) would not have to throw away its mass.
There are other ways to get around without throwing mass. Light sails produce it by interacting with photons that the sun (or
Re: (Score:3, Interesting)
Getting energy into space is easy. You can grab it from nearby stars, or you can carry a nuclear reactor with you. Because a nuclear reactor converts mass to energy via E=Mc^2, it produces a lot of energy from a small mass.
The real problem is reaction mass. You have to have something to push against in order to move. Getting a lot of reaction mass into space is difficult. If you can push against the vacuum of space, that problem is solved.
QED (Score:3, Informative)
The existence of particles in a vacuum? That sounds exactly like the aether, a scientific theory that was abandoned about 200 years ago! [wikipedia.org]
I suggest you read this book: QED The Strange Theory of Light and Matter [wikipedia.org]
As the author of the introduction, Zee notes: "According to Feynman, to learn QED you have two choices: you can go through seven years of physics education or read this book"
This is the best book there is that I know of that will give you the grounding to get Quantum Electrodynamics. You will discover that particles do in fact, exist in a vacuum. The quantum world does not work anything like the macro world that we are used to. You have