The starship Enterprise, familiar to fans of the "Star Trek" series, is supposed to use an incredible technology called warp drive, a sophisticated power source that has antimatter at its heart. Antimatter supposedly produces all the energy the ship's crew needs to warp its way around the galaxy and have adventures. Naturally, such a power plant is the work of science fiction.
However, it seems so useful that people often wonder if a concept involving antimatter could be used to power interstellar spacecraft. It turns out the science is quite sound, but some hurdles definitely stand in the way of making such a dream power source into a usable reality.
What Is Antimatter?
The source of the Enterprise's power is a simple reaction predicted by physics. Matter is the "stuff" of stars, planets, and us. It's made up of electrons, protons, and neutrons.
Antimatter is the opposite of matter, a sort of "mirror" matter. It's composed of particles that are, individually, antiparticles of the various building blocks of matter, such as positrons (antiparticles of electrons) and antiprotons (antiparticles of protons). These antiparticles are identical in most ways to their regular matter counterparts, except that they have the opposite charge. If they could be brought together with regular matter particles in some sort of chamber, the result would be a giant release of energy. That energy could, theoretically, power a starship.
How Is Antimatter Created?
Nature does create antiparticles, just not in large amounts. Antiparticles are created in naturally occurring processes as well as through experimental means such as in large particle accelerators in high-energy collisions. Recent work has found that antimatter is created naturally above storm clouds, the first means by which it is produced naturally on Earth and in its atmosphere.
Otherwise, it takes massive amounts of heat and energy to create antimatter, such as during supernovae or inside main-sequence stars, such as the sun. We are nowhere near being able to emulate those massive types of fusion plants.
How Antimatter Power Plants Could Work
In theory, matter and its antimatter equivalent are brought together and immediately, as the name suggests, annihilate each other, releasing energy. How would such a power plant be structured?
First, it would have to be very carefully built due to the huge amounts of energy involved. The antimatter would be contained separate from the normal matter by magnetic fields so that no unintended reactions take place. The energy would then be extracted in much the same way that nuclear reactors capture the expended heat and light energy from fission reactions.
Matter-antimatter reactors would be orders of magnitude more efficient at producing energy than fusion, the next best reaction mechanism. However, it still isn't possible to fully capture the released energy from a matter-antimatter event. A significant amount of the output is carried away by neutrinos, nearly massless particles that interact so weakly with matter that they are nearly impossible to capture, at least for the purposes of extracting energy.
Problems With Antimatter Technology
Concerns about capturing energy aren't as important as the task of getting enough antimatter to do the job. First, we need to have enough antimatter. That's the major difficulty: obtaining a significant amount of antimatter to sustain a reactor. While scientists have created small amounts of antimatter, ranging from positrons, antiprotons, anti-hydrogen atoms, and even a few anti-helium atoms, they haven't been in significant enough amounts to power much of anything.
If engineers were to gather all the antimatter that has ever been artificially created, when combined with normal matter it would scarcely be enough to light a standard light bulb for more than a few minutes.
Furthermore, the cost would be incredibly high. Particle accelerators are pricey to run, even to produce a small amount of antimatter in their collisions. In the best-case scenario, it would cost on the order of $25 billion to produce one gram of positrons. Researchers at CERN point out that it would take $100 quadrillion and 100 billion years of running their accelerator to produce a single gram of antimatter.
Clearly, at least with technology currently available, the regular manufacture of antimatter doesn't look promising, which puts starships out of reach for a while. However, NASA is looking for ways to capture naturally created antimatter, which could be a promising way to power spaceships as they travel through the galaxy.
Searching out Antimatter
Where would scientists look for enough antimatter to do the trick? The Van Allen radiation belts-doughnut-shaped regions of charged particles that surround the Earth-contain significant amounts of antiparticles. These are created as very-high-energy charged particles from the sun interact with Earth's magnetic field. So it might be possible to capture this antimatter and preserve it in magnetic field "bottles" until a ship could use it for propulsion.
Also, with the recent discovery of antimatter creation above storm clouds, it could be possible to capture some of these particles for our uses. However, because the reactions occur in our atmosphere, the antimatter will inevitably interact with normal matter and annihilate, likely before we have a chance to capture it.
So, while it would still be quite expensive and the techniques for capture remain under study, it might be possible someday to develop a technology that could collect antimatter from the space around us at a cost less than artificial creation on Earth.
The Future of Antimatter Reactors
As technology advances and we begin to understand better how antimatter is created, scientists can begin to develop ways of capturing the elusive particles that are naturally created. So, it's not impossible that we could one day have energy sources like those depicted in science fiction.
-Edited and updated by Carolyn Collins Petersen