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Antimatter Space Drive
sckienle writes "Space.com has an article on using anti-matter for propulsion in space. It isn't true Star Trek warp stuff, in fact it is a variation on an fusion based pellet design I saw in the late 70's, but interesting concept. The concept is still somewhat of a dream, as stated in the article: 'The real hub is the storage [of antimatter]. There's a lot of technology between here and there.' Later on it also mentions that we can't produce a lot of antimatter efficiently yet. Still it might be worth the effort if the theoretical acceleration proves out." The BBC has a story about studying antimatter in a lab.
...At least to provide thrust for a vessel of any kind since it costs more energy (incredibly more, with current technology) to produce than it actually stores. The only advantage to using an antimatter/matter reaction as a propellant is the sheer efficiency of the reaction. You get a lot more push out of a lot less 'fuel'. If you can get away with carrying less total mass, then you don't have to accellerate or decelerate as much.
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This is incorrect; the closest star is Proxima Centauri; 4.24 LY. Tau Ceti is 11.35 LY away (Source)
Actually, the majority of the science in Star Trek is based heavily on actual theories and practices. For pretty much every piece of technology that has ever been the show save for things relating to dieties and fantasy, someone somewhere has a viable theory as to making something like that work.
And the funny thing, I know all that while at the same time really not like the show at all.
Finally, math books without any of that base 6 crap in them.
Example: a dude sitting on a sled on a frozen pond, with a sackful of bricks. When he throws a brick off the sled in one direction, the sled moves in the other direction. Because there is very little friction between the sled and the ice, the sled keeps moving. Throw more bricks, and the sled will go faster.
To make everything clear: the sled is like a rocket, the bricks are like fuel, and space has even less friction than a frozen pond. Because the total momentum of the system must be conserved, as fuel is burned and exhaust is generated, the rocket moves forward.
My focus isn't particle physics, but maybe I can offer a correction for your approach. In #2 you presuppose that antimatter and matter are produced in equal amounts; actually, nature seems to favor production of matter over the anti counterpart. Look up CP violation for more on this. So at the Big Bang, all the antimatter annihilated with much of the matter, but since there was an imbalance in the initial production, there was still some matter left over. This is the stuff you and I are made of.
As far as difficulty in production, it happens that most of the particle-pair interactions that decay into antimatter particles only occur at very high energies compared to what our accelerators can achieve, and even then at low probabilities. Then there is the matter of containment. Current methods involve redirection with magnetic fields or trapping with lasers, both of which are extremely difficult and therefore expensive.
As usual, the big problem with this bit of physics is the funding. Going out on a limb, particularly in longterm scientifics, is not promoted as a safe or particularly clever business strategy. This leads to what is not exactly the most logical method of pursuing progress, but I digress in my bias.
"Loki, I think you picked the wrong god to use for a nick. Judging by your excitement over the possible use of antimatter in weapons of mass destruction, perhaps Shiva would have been more appropriate."
;)
Not at all true.
Loki would have loved to get his hands on something like this, if for no other reason than to scare the shit out of the other gods (explode a dozen simultaneously while the gods were asleep). Actually, getting more towards Ragnarok, he'd have gladly used these to blast his fellow gods into oblivion. I liked him more when he was a simple trickster.
-- "Government is the great fiction through which everybody endeavors to live at the expense of everybody else."
1. The problem is, there just simply isn't a large enough sample size at different frequencies of gamma radiation to make any sort of determination about the distribution of antimatter. The number of particles detected varies based on solar activity levels, etc...
2. I believe the most popular theory now is that the distribution of antimatter galaxies is in other galactic clusters... therefore, we don't see much evidence in our immediate neighborhood.
3. There are actually many different ways of decaying matter to produce antiparticles... the problem is most of these take place in the nucleus, where they are quickly annihilated, and most of these are at higher energies than is common today.
Romeo & Juliet for 1337 hax0rz! http://www.redcoat.net/pics/romjul.swf
Absolutely. Interactions and decays are governed by probabilities, where the only constraints on the results are conservation laws such as charge and angular momentum. I can't support anything on just how probable any decay is, so consider that an extrapolation, but I can give an example of a specific decay. The W boson decays into (or is produced by collision of) an antilepton and a neutrino, or an antineutrino and a lepton (total net charge must be plus or minus 1). I checked lanl for something moderately understandable and didn't find much ("Schwinger-Dyson Analysis of Dynamical Symmetry Breaking on a Brane with Bulk Yang-Mills Theory", "Charmless Exclusive Baryonic B Decays"); however, this is more common and semi-popularized physics so you might try just general googling for particle decay and collision production charts.
I think the idea is this: for short journeys, you accelerate until you're half way there, then you turn the ship around and decelerate. This has the added advantage of providing you with some sort of gravity (how much depends on your acceleration) for the duration of trip (aside from when you're flipping over). For longer trips, you'll accelerate until you're cruising along nicely, then turn the engines off. You'll have to flip over and decelerate for the same amount of time you spent accelerating tho...
You very quickly pile up speed too. If you accelerate at 1g for a year, you get rather close to c. If you ever want to return home tho, you'll have to be careful: at 0.99999999996c, you can cross the galaxy in 12 years of your own time, but 113 000 years will pass for us back here.
First, antimatter "explosions" are actually fizzles, because P-barP reactions at rest tend generate neutral and charged pions and kaons, and neutrinos.
Neutrinos don't interact significantly with matter, so that energy is effectively lost. The neutral pions and kaons interact with the weak force only, and hence carry energy away for quite a distance (kilometers for pions) before they decay into something that does interact with matter. 50% of the time for every charge particle you get m neutral particles, where m>2 (see references
That means that most of your energy is carried kilometers or more away (for the relativistic ones) before decaying into energetic particles that DO cause things to go boom. The energy of the antimatter tends to be dispersed through a rather large volume.
Antimatter is, however, extremely valuable for rockets, due to a unique advantage. The general Hohman-transfer equation, which governs interplanetary flight, has a term exp{V/V0}, where V is the exhaust velocity and V0 is the "mission velocity", defined to be the delta v necessary to achieve a particular orbit.
For example, V0=11.2km/sec for orbit, and ~29km/sec for Saturn. Note that getting into Earth orbit gets you almost halfway to anywhere.
The propellant/load ratio, which is how much propellant per unit of mass you need to get somewhere, therefore depends (exponentially) upon the ratio of V/V0. Now, V is limited in chemical rockets to be at best 7.4 km/s for O1/LH2, so you have a built-in, exponentially growing ratio of rocket fuel you must carry per kilogram of payload. This makes manned flights to Saturn impractical with chemical rockets.
However, an antimatter rocket has no built-in limit on exhaust velocity. Solving the equations, that means that you can get to anywhere on an antimatter rocket with a fuel/payload ratio of 5:1. That doesn't sound great, but it's much better than 100:1 for orbit or 300:1 for interplanetary flights.
And, in fact, with antimatter rockets you can start *thinking* about not using Hohman transfers (which minimize the necessary energy) to get someplace, and can consider minimizing your time instead. You'll need the same fuel ratio, just more antimatter to increase your exhaust velocity V. Forward has a design for a basic antimatter rocket he did research on for the USAF.
Finally, there are ways to store antimatter for weeks at a time, using Pfenning traps and other magnetic facilities.
Antimatter, however, makes a lousy energy source, as it must be fabricated, you get less out of it than you put into it (we're currently
But it's a wonderful rocket fuel.
--Adam
"Invincibility is in oneself, vulnerability in the opponent." --Sun Tzu
Some of the Russian Venera and Luna probes took the first approach--deliberately crashing into Venus or the Moon, respectively. NASA's Voyager craft did a tremendous amount of good science with just flybys. Galileo (the spacecraft, not the Italian scientist) dropped a probe into Jupiter's atmosphere and then settled into two years of orbiting the planet.
~Idarubicin
The magnetic containment doesn't have to be electromagnetic. Natural permanent magnets have nearly 0 chance of failure. The little plastic fruits have been sticking to my grandmother's fridge for 50 years now.
Depends on how the magnetic containment works. Faraday proved that no static assemblage of magnetic, gravitic, and electric fields can be stable; in other words, a non-dynamic system that depends on only the above three fields will fall apart.
Faraday did not know about two things, though, and that's diamagnetics and antimatter. All materials are either ferro-magnetic, meaning they can take and hold a magnetic field, paramagnetic, meaning they attract magnets, or diamagnetic, meaning they repel magnets. A google search will tell you more.
Faraday's proof doesn't work for diamagnetic materials. However, most materials are only very slightly diamagnetic. Water, bismuth, and a certain kind of graphite are the most diamagnetic. I have succesfully levitated a very small slice of graphite using permanent magnets.
Someone once levitated a frog. That magnet was a 10 Tesla magnet, though; there are no permanent magnet technologies that can get anywhere close to that magnetic strength.
The only way you could do it with permanent magnets is if antimatter happens to be diamagnetic. This would be the case if, for instance, we find that antimatter's magnetic fields respond oppositely to that of normal matter; anti-steel, for instance, would not be paramagnetic but strongly diamagnetic.
If that's not the case, then you HAVE to use big honking electromagnets.
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