How To Build a Quantum Propulsion Machine 392
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."
Call me pedantic but... (Score:3, Insightful)
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.
Nadesico? (Score:2, Insightful)
This sounds a whole lot like the way the engines work in the anime Kidou Senkan Nadesico. There's even a helpful animation played to explain it all to the crew and passengers.
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.
Re:Reactionless drives (Score:3, Insightful)
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.
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.
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.
Re:Is this different from a photon drive (Score:1, Insightful)
OK, I officially don't know what I'm talking about. Carry on. :)
Smartest slashdot comment yet on this article. That should earn you a +5 insightful right there
Re:ATTENTION (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 kinetic energy proportional to the square. Good old KE=0.5mv^2
Re:Reactionless drives (Score:3, Insightful)
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 is a very big number. It's equal to about ten years worth of total planetary energy use. And every single joule of that you have had to generate and feed to your drive.
So I don't think we're going to see relativistic kill vehicles any time soon.
Re:ATTENTION (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.
Re:Call me pedantic but... (Score:2, Insightful)
So... you're saying that nothing's impossible? Or just that we ain't seen nothing yet?
Re:ATTENTION (Score:3, Insightful)
Well, that one again doesn't give you linear momentum.
But yeah, you can get linear momentum too if you have something to push on, like a magnetic field around a planet.
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.
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.
Re:Momentum Conservation (Score:3, Insightful)
Quite the opposite, in fact. The article explicitly states that it would be adding momentum to the ambient EM field.
It's possible the idea won't work, but as given it definitely does not violate conservation of momentum.
Re:Momentum Conservation (Score:3, Insightful)
Sorry, the "coolness" of this theory is hard to explain, which is also the reason the theory is so unlikely (but would be SO COOL if it's true!)
Currently, if I want to move an object, I need to receive and/or cause some sort of external reaction in the opposite direction to do it. Either I push against something or something pushes against me, or I eject mass in one direction at speed to move in another. Something in my surrounding environment is required for me to act against, or I need to change the environment by ejecting mass into it.
So an airplane can move because it's pulling air in from in front of it and shoving it out behind it very fast, and that force allows it to move forward. As the aircraft moves forward, a bunch of air is pushed backward to make it happen.
A rocket leaves a lot of mass behind, and even a car has an unmeasurably small effect on the rotation of the Earth (or shifts stuff around, which you can observe by spinning tires on gravel when the friction gets too low).
A ship built using this theory would use nothing in its surrounding environment, and would introduce nothing to that environment, at least as it relates to propulsion.
It could travel through a vacuum without leaving a trail of reaction mass behind it, so with a limitless supply of energy it could continue on for a limitless amount of time.
Currently, even the best mass-ejection drives are limited by energy AND mass storage capacity. True, in many cases, the fuel and mass are the same thing (explode the fuel into energy and the exhaust is the mass), but this allows you to take mass out of the equation, so you don't have to carry any reaction mass, you only need lots of energy.
I'm not saying this will create a particularly practical engine, though maybe it could. But the theory totally busts Newtonian physics (by busting the "Equal and Opposite" law) or expands our understanding of the Universe significantly (by introducing a new level of matter we are pushing against).
Re:Implications? (Score:3, Insightful)
And if other intelligent life has done this, then there would be space probes flying around through our solar system. Maybe we're just missing them.
There are literally billions of stars in the galaxy- even if a thousand civilizations spent a sizable portion of their energy lobbing (largely pointless) space probes all over the place, there're still no guarantees that one would be in the solar system during the (astonishingly brief) period that humanity have been looking for them.