Aboard the starship Enterprise, a fabled craft from the Star Trek series, the warp drive is powered by a sophisticated power source that uses antimatter to produce incredible amounts of energy.
Naturally, such a power-plant is the work of science fiction. But could this concept one day be used to power interstellar space craft? Actually the science is quite sound, but there are definitely some hurdles that stand in the way of bringing this dream to reality.
What is Antimatter?
The reaction is really quite simple. Antimatter is comprised of particles that are, individually, antiparticles of the various building blocks of matter -- such as positrons (the antiparticle to the electron) and the antiproton (the anti particle to the proton). These antiparticles are identical in most ways to their regular matter counterparts, except in that they have the opposite charge.
How is Antimatter Created?
Antiparticles (and therefore antimatter) are created by various means by a number of naturally occurring processes of nature, but also through experimental means such as in large particle accelerators on Earth.
Recent work has found that antimatter is created naturally above storm clouds, providing the first means by which the substance is produced naturally on Earth. Usually, antimatter is generated in artificially in labs using high energy particle collisions.
Otherwise it takes massive amounts of heat and energy to create antimatter, such as during supernovae or inside main-sequence stars.
How Antimatter Power-plants Work
In theory the design is quite simple, matter and its antimatter equivalent are brought together and immediately, as the name suggests annihilate each other.
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 over the next best reaction mechanism, fusion, it still is not possible to fully capture the released energy. A significant amount of the output is carried away by neutrinos which are 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
The primary difficulty with such devices is obtaining a significant amount of antimatter to sustain a reactor. While we have successfully 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 you were to gather all of the antimatter that has ever been artificially created it would scarcely be enough to, when combined with normal matter, light a standard lightbulb for more than a few minutes.
Furthermore there is the cost consideration. Particle accelerators much to run at very high energy even to produce a small amount of antimatter in their collisions. Running the accelerators in this way is quite expensive.
In the best case scenario it would cost on the order of $25 billion to produce one gram of positrons. While researchers at CERN point out that it would take 100 quadrillion dollars and 100 billion years of running their accelerator to produce a single gram of antimatter.
Clearly, at least with technology currently available today it does not look promising that we could manufacture enough antimatter to make antimatter reactors viable. However, NASA is looking for ways to capture antimatter that is created naturally by mother nature.
The Van Allen radiation belts (donut shaped regions that surround the Earth in its magnetic field) contain significant amounts of antimatter that were created as very high energy charged particles from the Sun interacted with Earth's magnetic field. So it may be possible, though not currently so, to capture this antimatter and preserve it in magnetic fields.
There are other phenomenon in our solar system that give rise to antimatter production. So, while it would still be quite expensive, it may be possible to develop a technology that could collect antimatter from the space around us at a cost less than artificial creation on Earth.
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.
The Future of Antimatter Reactors
While a highly efficient and simple means of producing energy, antimatter reactors are a long way off from becoming a reality. Mainly because obtaining enough antimatter to make a reasonable amount of power is proving beyond our technological understanding.
However, as technology advances and we begin to understand better how antimatter is created, we can begin to develop ways of capturing the elusive particles that are naturally created. So while improbable, it is not entirely impossible that we could one day have energy sources like those depicted in science fiction.