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Antimatter: The Production Problem

Antimatter is so tantalizing a prospect for propulsion that every time a new slant on using it appears, I try to figure out its implications for long-haul missions. But the news, however interesting, is inevitably balanced by the reality of production problems. There’s no question that antimatter is potent stuff, with the potential for dealing out a thousand times the energy of a nuclear fission reaction. Use hydrogen as a working fluid heated up by antimatter and 10 milligrams of antimatter can give you the kick of 120 tonnes of conventional rocket fuel. If we could get the cost down to $10 million per milligram, antimatter propulsion would be less expensive than nuclear fission methods, depending on the efficiency of the design.

But how to reduce the cost? Current estimates show that producing antimatter in today’s accelerator laboratories runs the total up to $100 trillion per gram. But when I was researching my Centauri Dreams book, I spent some time going through the collection of Robert Forward’s papers at the University of Alabama-Huntsville, where several boxes of materials are stored in Salmon Library. Forward was constantly working in a number of different fields, always keeping his eye on the latest research, and as part of that effort he produced a series of newsletters on antimatter developments that he circulated among colleagues.

Image: A Penn State artist’s concept of an antimatter-powered Mars ship with equipment and crew landers at the right, and the engine, with magnetic nozzles, at left. Credit: PSU.

Reading through these materials, I came to see that when we quote the $100 trillion per gram figure, we’re talking about antimatter as produced more or less as a byproduct. Forward understood and appreciated the science requirements of particle accelerator labs but also saw that they were hardly the most efficient place to produce antimatter in any quantity. They were not, after all, in the propulsion business. He proceeded to do a study for the US Air Force looking at what might happen if an antimatter facility were actually designed for no other purpose than the creation of antiprotons, finding that the energy efficiency could be raised from one part in 60 million to a part in 10,000, or 0.01 percent.

The cost of building the factory, meanwhile, could be lowered dramatically, to the point where Forward believed our $10 million per milligram would be within reach. This is an interesting figure in several ways. As noted above, it makes antimatter feasible for certain kinds of space missions (assuming equivalent advances in our methods of antimatter storage. But as the price begins to drop, we can expect to find new applications in other areas of research, which should drive demand and spur further work on efficient production. It’s worth remembering that even at today’s prices, antimatter has proven its worth in scientific research and medical uses.

What about other ways of lowering the cost? One possibility is to look beyond slamming high-energy protons into heavy-nuclei targets. Writing with Joel Davis in a book called Mirror Matter: Pioneering Antimatter Physics (Wiley, 1988), Forward looked at options like heavy ion beam colliders, in which beams of heavy ions like uranium could be collided to produce 1018 antiprotons per second (with acknowledged problems in creating large amounts of nuclear debris). He also considered new generations of superconducting magnets to create magnetic focusing fields near the region where the beams collide, which should make tighter beams and greater antimatter production possible.

I bring all this up because the possibility of harvesting antimatter from natural sources in space, which we talked about last week, has to be weighed against boosting production here on Earth. But Forward’s ideas actually coupled the two notions. He wanted to move antimatter production by humans into space in the form of huge factories. Here’s what he has to say on this in an essay in his book Indistinguishable from Magic (Baen, 1995):

Where will we get the energy to run these magic matter factories? Some of the prototype factories will be built on Earth, but for large scale production we certainly don’t want to power these machines by burning fossil fuels on Earth. There is plenty of energy in space. At the distance of the Earth from the Sun, the Sun delivers over a kilowatt of energy for each square meter of collector, or a gigawatt (1,000,000,000 watts) per square kilometer. A collector array of one hundred kilometers on a side would provide a power input of ten terawatts (10,000,000,000,000), enough to run a number of antimatter factories at full power, producing a gram of antimatter a day.

We’re a long, long way from producing a gram of antimatter a day, of course, which is why studies like the recent one performed by Ronan Keane (Western Reserve Academy) and Wei-Ming Zhang (Kent State University) have such a futuristic air. But it’s important to learn the theoretical constraints on propulsion systems even if the required antimatter isn’t available, and on that score, Keane and Zhang are thinking ahead to the most advanced kind of antimatter of them all, a beamed core drive. To make it work, assuming you have the antimatter available, you need to inject protons and antiprotons into a magnetic nozzle, one that channels charged pions from the matter/antimatter annihilation into a focused beam of powerful thrust.

Although charged pions decay quickly, they can start out at 90 percent of the speed of light. Unfortunately, earlier magnetic nozzle calculations have proven inefficient at channeling these energies, dropping the exhaust velocity down to a third of this value. Tomorrow we’ll look at how a more efficient magnetic nozzle can produce better results, as Keane and Zhang have analyzed using CERN software to simulate what would go on in the hellish interior of a beamed core antimatter engine. But we also need to consider other ways of using antimatter for propulsion, assuming that Forward’s space-borne factories aren’t going to be coming online any time soon.


Comments on this entry are closed.

  • TomTom May 21, 2012, 11:08

    How about a steam engine in space. You could use anti-protons to heat H2O on a recon satellite so it can change orbits more efficiently. Then you could retire your fixed wing recon assets, like the SR-71. You would of course need a way to move the anti-protons around, from production site to launch facility, but the RFP’s for such a system are old news. I might even suggest that such a bird existed by 1997.


  • Joy May 21, 2012, 16:54

    Suppose friendly aliens showed up at the Chicago Mercantile Exchange offering to sell antiprotons in bulk in exchange for their mass in gold. Such a deal! The catch is that buyers have to provide their own antiproton container. Oh no! We are a long, long way from having a system suitable for safely carrying even milligram quantities of antiprotons around. Antiproton traps are leaky, not a major issue when you are storing only trivial masses, but a show stopper if one desires to transport significant antiproton masses.

  • David May 21, 2012, 18:36

    Joy the CME would still sell them and the big banks will sell soff market Credit Default Swaps on the antimatter container maker……and then it would work but the bansk having bet wrong would go broke again and we would have to cancel the realtivistic rocket because we would have to bail out the banks again!

    Seriouly I would like to see someone go over the Project Orion numbers again like we saw on the anti-matter rocket. I am sure that we can make anti-matter and contain it . I just dont see it this century but I hope I am wrong
    But there are things we can do in the meantime.

  • A.B. Samma May 21, 2012, 18:40

    I wonder how antimatter’s efficiency compares to fusion power?

  • Dan Ibekwe May 21, 2012, 20:29

    Was the SR71 not retired in 1989? (IIRC, three of them were returned to service briefly in the early 90’s).

    The politics of AM production might prove…challenging, given the anti-nuclear hysteria fashionable these days. Space based production would be the only acceptable way to go, with Robert Forward’s 100-square kilometer facility being constructed at the L5 point. Of Venus. Just to be sure.

  • Eniac May 21, 2012, 21:46

    How much antimatter would be required to blow up a Planet?

  • Alex Tolley May 21, 2012, 22:10

    Suppose friendly aliens showed up at the Chicago Mercantile Exchange offering to sell anti-iron in bulk in exchange for their mass in gold.

    Wouldn’t magnetic storage with regular matter then be a viable solution?

  • James Jason Wentworth May 22, 2012, 0:41

    Since we are still (unfortunately) in the position of beggars talking about how they will decorate their mansions when they become rich with regard to antimatter propulsion, have there been any fresh looks at Dr. Eugen Sänger’s matter/antimatter-powered photon rocket since the 1960s? Its thrust was, of course, very small, but its exhaust velocity of c was the highest obtainable. Also:

    Perhaps improvements in engineering and an increase in knowledge of the physics involved since then have brought us to a point where the services of only *one* sympathetic unicorn (as opposed to a blaze of such willing unicorns, in the 1960s) would suffice to make a photon rocket workable today? :-) Even if current (or recent) studies indicate that such an engine is still far over the horizon, any even slight lightening of our current ignorance of how to build a working unit would be worth the knowledge gained, for physics in general as well as for starprobe/starship propulsion. Many thanks in advance to anyone who can shed light on this.

    — J. Jason Wentworth

  • spaceman May 22, 2012, 1:03

    Has anyone read Charles Pelligrino’s “Flying to Valhalla”? If I remember correctly, in that novel the starship’s antimatter fuel was created in vast solar powered factories on the surface of Mercury. In the story these factories, which I believe were constructed largely by robots, regularly churned out the necessary tons of anti-hydrogen to fuel starships. Having antimatter factories far from Earth sounds like a good idea to me.

  • parmanello May 22, 2012, 4:22

    Great article. “Use hydrogen as a working fluid heated up by antimatter and 10 milligrams of antimatter….”

    Do you mean “matter and 10 milligrams of antimatter” or do you heat the hydrogen with direct antimatter exposure?

  • Paul Gilster May 22, 2012, 10:09

    parmanello writes:

    Do you mean “matter and 10 milligrams of antimatter” or do you heat the hydrogen with direct antimatter exposure?

    The latter — charged pions passed through liquid hydrogen would produce a hot plasma that can be ejected from a rocket nozzle. Or consider a solid-core design, where antiprotons are injected into a cavity in the center of a tungsten block and annihilate with hydrogen gas stored there. The tungsten is heated and cold hydrogen introduced into the heat exchanger emerges at high temperatures and generates thrust. Using tiny amounts of antimatter to heat tons of propellant helps us get around the antimatter production problem.

  • Mike Lockmoore May 22, 2012, 13:04

    Wild, irresponsible speculation here… if you buy-in at all to the notions that elementary particles are emergent phenomenon caused by stable patterns existing on a suitable matrix (strings, energy fields, aether, etc. etc.), then it may be possible someday to devise a “catalyst” that would alter the patterns of ordinary matter to convert them into the corresponding anti-particle patterns. For example, you “bounce” ordinary particles off a matter-antimatter converter catalyst plate that reflects each particle as a mirror-imaged pattern.

    Of course, it may be entirely possible that if we knew enough to develop and make an antimatter catalyst, we’d probably know a more direct way to interact with the fundamental substrate(s) to obtain massive amounts or energy and/or impulse much more efficiently and effectively, making the “smash matter and antimatter together” goal seem quaint. I can dream so at least. In the meantime, antimatter catalyst makes a pretty good comic book plot device, does it not? :-P

  • Ron S May 22, 2012, 15:50

    Mike, it’s been done in the sci-fi literature. Treating the attributes of elementary particles and fields as information that, if you understand the lock and have the key, can be altered, is used as a plot device in several books by Greg Bear (and others whose names I can’t recall just now).

    Thankfully this is purely fiction since, as you might imagine, and Bear does, particle attributes can be “hacked” with exceptionally unpleasant results.

  • ljk May 22, 2012, 16:08

    James Bickford’s “Extraction of Antiparticles Concentrated in Planetary Magnetic Fields” from NIAC in 2006:


    And a paper on all the potential uses for antimatter in addition to interstellar travel:


  • ljk May 22, 2012, 16:15

    Anyone know what has become of Penn State’s Antimatter group? Their Web site said it stopped updating back in 2001 and was to be transferred to another site, but the one they link to appears to be junk.


  • Eniac May 23, 2012, 7:20


    Using tiny amounts of antimatter to heat tons of propellant helps us get around the antimatter production problem.

    But, this way you would not really gain much above chemical rockets. If all you want is lots of propellant accelerated to a few km/s, a chemical rocket will do just about as good a job as an antimatter powered one. You get a substantial advantage for using pure hydrogen, similar to NERVA, but that is it. You will never be able to beat a nuclear electric ion engine in terms of terminal velocity, and interstellar is definitely out.

    The gains are not worth the trouble, in this case.

  • Greg May 23, 2012, 12:17

    “The gains are not worth the trouble, in this case.”

    Maybe not for interstellar travel for launch capabilities to orbit it would be ideal, since the weight eliminated using a smaller mass would then be used for payload.

  • Eniac May 23, 2012, 23:36

    It is also conceivable to react antimatter with, say, water and have the resulting ultra-high temperature plasma push against a magnetic nozzle. This would surmount the thermal limit I was talking about, and possibly provide very high thrust. Still, in terms of Isp even that is extremely wasteful. For interstellar travel we absolutely need the high burnout velocities that can only be achieved by direct use of annihilation products. Any significant addition of inert propellant would lead to impossible mass ratios.

  • Ole Burde May 24, 2012, 15:56

    “For interstellar travel we absolutely need the high burnout velocities that can only be achieved by direct use of annihilation products. Any significant addition of inert propellant would lead to impossible mass ratios.”
    Exactly . And thats just one realy good reason why a pure antimatter drive is way beyond the horizont of the predictable possibilities . It makes a lot more sense to concentrate on things INSIDE the horizont . Any Baby will tell you , the best way to learn to walk , is to learn crawling first . In our case , crawling must be designing an energy efficient fission rocket . And perhabs a more-or-less self sustaining lifesupport system that doubles up as part of the radiation protection …. hmmm .. could there be algae or bacteria living in the cooling waters of nuclear reactors after decades of operation ?

  • Bounty May 24, 2012, 19:43

    1. Effecient life support systems are probably the most important and nearest term goal. If we had a .5c spaceship, we still couldn’t visit stars with it with our current life support systems. However if we develop a sustainable life support system, we can go at whatever speed we can manage. Not to mention bases in the ocean, Antarctica, on the Moon, on Mars in asteroids etc.

    2. Power generation would probably be next in a realistic timeline, and in importance. Most inner solar system stuff will be sun powered. By the time we can get away from the Sun, we should have some decent power generation options.

    3. Going somewhere eventually if you fell like it. This step would basically be optional.

    The only thing I could see upsetting this order would be teleportation, wormholes and FTL, which I don’t think we’ll make any progress on any time soon.

  • Tom June 15, 2012, 19:17

    The funny thing about antimatter is its a ‘packaging’ solution… theoretically the biggest bang for the buck. Like terrestrial ‘fuel’ efficiency, its not all in the fuel that is utilized; rather how resources are used in a system. I imagine the an ion propulsion with a ‘positronic’ afterburner could get you reasonably good numbers and be easier to engineer? you could have higher operational lifespan with a ‘simpler’ system? Positron should be about 2000 Xs more easier to produce than anti-protons.

  • Jill December 31, 2012, 19:03

    Potentially we are on the cusp of a breakthrough with the Higgs particle research. If we can spontaneously get regular matter to flip to anti-matter then there is no need for the dangerous storage problem. We would just need to store enough for the immediate need and then generate more.

    Doesn’t an anti-matter drive require equal parts of normal and anti-matter to operate?

    I just did a napkin calculate if the Saturn V burned for 20 min at 190 million hp the equivalent gram equivalent would be 1.89g which means you would need 0.94 g of anti matter for the equivalent of a Saturn V launch.