Since the 1960s and the first Star Trek episodes, the concept of antimatter as a power source has been in the main stream. How many times did we hear a line including loss of antimatter containment? Antimatter became synonymous with great power. In the Dan Brown novel Angels and Demons, the destructive capability of antimatter was exhibited when it was used to make a bomb to blow up the Vatican. To be sure, it’s very potent stuff. Less than a gram can unleash the power of the Hiroshima bomb. Surely something with such capability could be harnessed for such things as power generation and space propulsion.
A few days ago I interviewed Kurt Riesselmann of the Fermi National Accelerator Laboratory, an antimatter production and study facility . The primary purpose of the interview was to make sure that the science depicted in my second novel is correctly depicted, but the interview was so interesting that I decided to write a post about it as well.
What is Antimatter?
The simple answer is that antimatter is the opposite of matter. The more complex answer is that matter is made up of atoms. Atoms of matter are made up of protons, neutrons and electrons. Atoms of antimatter are made up anti-protons, anti-neutrons and anti-electrons, or positrons, which each have an opposite charge from their matter counterparts. When matter and antimatter meet, they annihilate each other, creating a bunch of energy in the process. That energy is what Gene Roddenberry used to power the star ship Enterprise and Dan Brown used in his bomb.
Is it Dangerous?
Surely something so potent that a capful could decimate a city must be incredibly dangerous. It would be if a capful of the stuff had ever been made. To date, the total produced by humanity is measured in nano grams – that’s billionths of a gram. Antimatter occurs naturally in cosmic rays and in the upper atmosphere, and is a component of a PET scan.
How is Antimatter Produced?
A whole bunch of it was created at the beginning of everything. Theoretically, equal parts of matter and antimatter should have been created when the big bang occurred. If that was the case, then they both should have obliterated each other. Yet somehow all the antimatter is gone. “Somewhere along the line, some process slightly favored matter over antimatter,” Riesselmann said. So matter won out. What ‘little’ matter won the war is what makes up the universe as we know it. If we want to produce it artificially, how is it done? At Fermilab, they produced anti-protons until 2011 and still produce other types of antimatter. For anti-protons they used a particle accelerator to speed up protons to nearly the speed of light and slam them into a substance like graphite. As Mr. Riesselmann put it, “it’s like when you smash a Swiss watch with a hammer. Pieces go flying off in all directions.” One of those pieces is an anti-proton, a form of antimatter. Left to its own devices, that anti-proton would soon find some matter and be obliterated. To stop that from happening, magnetic fields are employed to capture the anti-protons and direct them to a storage mechanism. At Fermilab, scientists used a storage ring, actually two of them. They operated one ‘small’ pre-storage ring that is about 1,500 feet in circumference and a much larger one that is 2 miles in circumference. The anti-protons traveled around the ring at near light speed, and were kept from striking the walls (which are made out of matter, of course) by more magnetic fields. When anti-protons were needed for research by the lab, the magnetic fields were altered with what are called kicker magnets to “create an exit ramp” off the ring.
Can Antimatter Create Power?
The mechanics of antimatter power generation are fundamentally the same as other nuclear reactions. The theory behind the process is that you use one of those off ramps mentioned above to direct a stream of antimatter from its storage ring into a reaction chamber where some form of regular matter is waiting to meet its opposite and get obliterated. That obliteration creates energy which can get converted into heat that can then be used to create power in any number of ways.
However, it takes energy to produce antimatter, and there is no efficient way to produce lots of it, much less store and transport it. Unless you’ve got a particle accelerator at every power reactor, you’ve got to have a way to move the antimatter – and you can’t exactly carry around a 1,500′ circumference ring. Antimatter can be slowed down to a halt, which reduces the magnetic force required to store it and keep it from getting in touch with regular matter. Doing so could allow for a portable magnetic field mechanism to transport it, but the technical issues with such a device are daunting.
Key issues with using antimatter to create power:
Issue #1: Efficiency
I wrote about how antimatter is created earlier in the article. What I didn’t mention is that Fermilab needed about one million protons in a particle accelerator to create one anti-proton. Once you’ve created antimatter, then you’ve got to spend energy maintaining the magnetic fields that keep antimatter from striking the walls of the storage ring and obliterating itself. Riesselmann estimated that you would only get “less than a billionth of a percent” of the energy back that you put into creating anti-matter with a particle accelerator in the first place.
Issue #2: Safety
It is significantly more difficult and dangerous to store and use antimatter than any other energy source, including fissile material, high explosives, gasoline… In fission reactor, you can drop in control rods and shut down the reaction. In a fusion reactor, if you lose magnetic containment, the pressure required to keep the reaction going is lost and the whole thing safely shuts down. In an antimatter reactor, if containment goes away, all that antimatter gets let loose, hits some matter and you get a big boom.
Issue #3: Quantity of Fuel
With current technology it takes a long time to make sufficient amounts of antimatter. At Fermilab, they created less than one nanogram of anti-protons per year. Obviously it would take a lot more for viable power generation.
Does Antimatter Power Make Sense?
Unless antimatter can be found naturally and collected, using it as a power source doesn’t seem to be viable, at least with foreseeable technology. Anything that takes so much more power to run than you get out of it is a losing proposition. Yet, antimatter as a power source could have its uses. If the cost of production can be brought down, antimatter could make sense in uses where significant power is needed in a remote setting such as on a spacecraft. It has a very high energy density, meaning the amount of energy capable of being produced is high for the mass, and volume, of the material supplying it. Antimatter reactions are millions of times more powerful than chemical reactions like burning hydrogen, and as much as a thousand times more than nuclear fission. This could make it a favorable mechanism to provide a lot of energy for propulsion on long journeys.
Antimatter can also can provide that energy more quickly, enabling higher thrust engines that can rapidly accelerate spacecraft to very high speeds, cutting travel time to the outer reaches of the solar system from years to weeks, or even days.
So, is antimatter power practical? For traditional power, the answer seems to be no. For something like a spacecraft engine, the answer is maybe. There is enough promise behind the concept that NASA and others are researching the possibility. Perhaps someday we will be speeding toward Jupiter and Saturn on antimatter powered spaceships.
Photo credit: VASIMR thruster, NASA JPL