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NASA Researching Antimatter Engines
dbolger writes: "CNN has a story about how scientists at NASA's Marshall Space Flight Center in Huntsville, Alabama are researching ways to use antimatter to fuel missions to Mars and beyond within the next 50 years. It very light on technical details, but does give an interesting look at current and future potential uses of antimatter."
I've never understood exactly how you would contain antimatter until it is used...Is it contained in some kind of electromagnetic field, or is this all still theoretical? I thought that antimatter was immediatly annilihated due to its inherently volatile nature when it is produced.
Anyone know any more details on how one would actually build up a gram of isolated antimatter?
I was at MSFC on a business trip a while back, and talked to the guys working on Gen2, Gen3 and later RLV design. Basically what the lead engineer told me they do is "assume we have really cool technology that meets certain specifications" and work backward from there to figure out how the rest of the vehicle be designed.
While I'm sure there might be one or two people actually doing research into antimatter, most of the work they do is just assuming *someone* will come up with the necessary technology by the time they have to build something.
Cell phones = communicators
Babelfish = universal translator
Taser(tm) = Phaser on stun
2-way videophone = Screen on the bridge
PC = Enterprise computer terminal
Now antimatter propulsion.
Was this guy good or what?
Computer Science is no more about computers than astronomy is about telescopes. --E. W. Dijkstra
Containment depends on what form it's in. Slashdotters have been referring to Penning traps here. Well, a Penning trap only works for charged particles, not neutral atoms, and it only traps one sign of charge -- you can't trap both + and - particles in the same Penning trap. Therefore, I don't think a Penning trap would be suitable for storing even microgram quantities of bulk matter; if you have matter or antimatter in bulk quantities, it has to be electrically neutral. I think the posters were confused between containment of plasma and containment of antimatter.
Containing antimatter, if you had it in bulk quantities, would be much easier than containing a plasma, since it doesn't have to be superhot like a plasma. You have to have an extremely good vacuum, however, because any matter that finds its way in will annihilate with the antimatter. I doubt that even the vacuum of interplanetary space would be good enough.
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Of the amount of energy created by matter/animatter annialation, consider the amount of energy that goes into creating the antimatter in the first place. The size of the accellerators and all the energy it takes to operate, just to produce a single particle of antimatter.
What you get out of this, is the energy potential equivalent of accellerating a single particle to near the speed of light. Thats a LOT of energy and it can be stored within two particles. Its no wonder that we need a very small amount of it to accomplish great things.
However, its extremely costly and time consuming to create, and without drastically improving the effiency of the creation process, this is not going to change anytime in the near future.
Also, don't forget about the potential arms race here. Antimatter doesn't occur naturally in nature like nuclear elements (such as uranium) do (at least not in a form that can be collected easily). Right now nobody has the capability of creating enough antimatter to do any significant damage. But if we are able to create enough to be useful, a few grams of antimatter could be used to make a weapon that is significantly more powerful than a nuclear weapon. And although tactical nukes come in briefcases, imagine a bomb of equal power that fits inside a watch.
Another issue to consider is that antimatter needs to be stored. If a chemical fuel tank leaks, no big deal. If a nuclear fuel tank leaks, you might get radiation poisoning, but the effect will be limited. If a gram of antimatter gets loose. WATCH OUT.
Still, if we plan to travel great distances, its a necessary step.
-Restil
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The job of a rocket is to create a stream of really fast particles moving in a particular direction. The faster, the better. Newton's Third Law and all that.
Those particles could be gas, accelerated with good old heat, ions accellerated with an electric field, or plasma.
Here's the rub: matter-antimatter reactions produce really energetic particles. Gamma rays, like. They kind a whiz right through the fuel you want to heat up. And the "combustion chamber." And the crew, and . . .
I read up on antimatter and fusion propulsion at grad school. (There's a suprising amount of good material out there; do not rely solely on the word of popularizers like Robert Forward!) The most-fully-realized antimatter rocket was kind of clunky. In the middle of the "combustion" chamber would be a cylinder of dense tungsten alloy full of tubules. A slow but steady stream of antiparticles are shot into the cylinder, which heats up. Hydrogen in pumped into the tubules; it heats up and "whoosh."
The disappointed bit: The specific impulse would "only" be about 5,000 seconds. This is about ten times what a liquid-fueled motor is capable of, and about 50% better than the little ion motor tested out on Deep Space One, but it's not amazing.
The most promising use for animatter: Using it as part of a fusion drive. A antimatter-catalyzed fusion drive described in the text I read was predicted to have a total impulse of something like 130,000 seconds. THAT is impressive. The thrust wouldn't be high, but you could keep it up for months and months.
What we might see are ships that use the direct-thermal sort of antimatter motor for getting a ship going (e.g., reaching escape velocity out of the Earth / moon system), then the fusion drive would be used to provide constant acceleration to speed up the trip.
Stefan
You could probably engineer something like a constant inflow of anti-matter to make for continous thrust. The only problem is the back flow on the fuel lines. this would be a lot easier than having a continous atomic fission explosion for thrust.
Strangely enough, this also works as a method fo moving asteroids around, since you could have atomic fuel lines running to a convenient crater. A trickle feed would create a continous nuclear reaction that would push the asteroid to a new course.
Alot of this stuff would need to be NOT engineered in low earth orbit, for obvious reasons.
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Star Fleet entrance exams may say this is a "trick question," but you really don't want to use a 1:1 matter/antimatter mixture.
The core issue is that energy, per se, is irrelevant in spacecraft propulsion. What matters is momentum transfer.
Kinetic energy scales as mv^2/2. Momentum scales as mv. So the "ideal" system would make a lot of mass move slowly... but that would require you carry around a lot of mass so you can throw it overboard.
Matter/antimatter is on the other extreme. Lots of energy, very little momentum transfer. If it were a sports car, the driver would be spinning his wheels and burning rubber, but barely moving because the tires aren't gripping the road.
I vaguely recall ideal matter/antimatter ratios being something like 10:1 to 20:1. If you assume the amount of junk thrown out goes up by a factor of 16 or so, the velocity will drop by a factor of 4. However the momentum transfer will be bumped by a factor of 4. You have to carry more reaction mass, but if you're talking about a less than an ounce of antimatter, a 16:1 ratio means a whopping pound of reaction mass.
A more advanced version of this gives you variable thrust engines. If you're in a deep gravity well, you toss in more mass so you burn more consumables but have better momentum transfer where it's critical. When you're in deep space, you use less reaction mass for the same amount of fuel.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
What about the theoretical exotic matter?
Antimatter is matter with a reversed charged.
When matter meets antimatter, both are annihilated and energy is released (a lot of it, based on E=mc^2).
Exotic matter, which isn't generally considered possible under Newtonian physics but which might be possible under quantumn physics, is matter that has a negative mass, and negative energy density. It has the opposite gravitational effect in relation to normal matter. A body of exotic matter would repel other bodies of both exotic and normal matter, AFAIK. Exotic matter, if it could really exist, would probably spread out equally across space, since it repels, rather than attracts other matter. If it came in contact with normal matter, it would annihilate it, but, unlike antimatter, it would release no energy whatsoever.
In general, the idea of exotic matter is very appealing, because it allows:
1.) The stabilisation of Einstein-Rosen gates, allowing an effective portal to another universe, should one exist. An Einstein-Rosen gate can be created by a spinning black hole, but is extremely unstable, to a point where even a boson would cause it's collapse.
2.) Construction of wormholes. (You need a great deal of exotic matter for this one, probably more than is practically attainable, even with very advanced technology)
One design suggests a wormhole that creates it's own exotic matter, eliminating the need for it's production.
3.) Construction of 'warp drives'. Alcuberre's warp drive (do a search on Google if you want to know what that is) violates certain conditions of quantumn physics and required an absurdly large quantity of energy. However, Chris van den Broeck, suggested an alteration of the design, whereby the 'warp bubble' would be extremely small (smaller than a proton) and the starship/object to be warped would be in another bubble which a larger internal volume than it's external volume. In principle possible, perhaps, but it's not known if the idea would work in reality, especially since the author of the paper has since published another paper listing problems with his proposal.
Still, the idea is kind of interesting.
Nobody knows if exotic matter is possible at all, let alone whether it's mass production is feasible.
First, you seem to have the misconception that NASA is entirely devoted to the manned exploration of space, and that moreover, they haven't done anything new since Apollo.
You are simply misinformed. You're just plain wrong.
Take a look at some of the projects that NASA has been up to recently, and then see if you can still claim they are "living in the past" :
Space Observatories
Chandra X-Ray Observatory
Hubble Space Telescope
Earth Observatories
Advanced Spaceborne Thermal Emission and Reflection Radiometer"
Solar System Missions
Mars Rovers
Astrophysics Research
Origins Program
And a sampling of the slate for future missions :
The Terrestrial Planet Finder
Deep Impact Comet Mission
Dawn Asteroid Flyby"
As you can see, NASA is not just about flying shuttle missions. They are actively sponsoring research in the space sciences and astrophysics across the board... from the study of our own planet, to the solar system, other stars and galaxies, and the cosmos as a whole. Their missions support the development of new technologies (which, unlike the previous poster seems to believe, are not limited to propulsion technologies, but include a wide array of telescopes and detectors across the entire spectrum). And NASA also actively supports scientists at all levels -- from graduate students through postdocs and faculty.
I think we live in a unique time where we as a species are really beginning to understand what makes up the universe, and how it works. I'm quite
confident that when the history of science of the 20th and 21st centuries is written, NASA will have played an enormously significant role in that process of discovery.
Bob
Science, like Nature, must also be tamed, with a view turned towards its preservation.
If you ever followed the research of Richard P Feynman and his like it's interesting to note that a matter/antimatter annihilation could simply be viewed as ordinary matter travelling normally one way, emitting huge amounts of energy, then travelling back the other way but backwards in time. It is well established that subatomic particles pay no attention to time whatsoever. We know matter contains lots of energy anyway. [E=mc^2, where c is lightspeed. Lightspeed squared = lots and lots of energy.]