antimatter sail concept
Photo Credit: European Southern Observatory (ESO)
The star nearest to Earth is Proxima Centauri at a distance of 4.244 ± 0.001 LY. Fortuitously, a confirmed planet Proxima b has been found orbiting that star in the habitable zone of that system. Recently another candidate exoplanet Proxima c has been identified that is too cold to likely harbor life. As of April 11, 2019 observations have confirmed 3940 exoplanets, of which 310 have been found to orbit within habitable zones. Of this population, 48 exoplanets exist within 25 LY of Earth, with 5 of these joining Proxima b as residing in habitable zones. One potential solution for reaching these destinations is the use of antimatter as fuel.
The basic concept involves the use of antiprotons to cause nuclear fission when they annihilate with the nucleons of Uranium-238 embedded in a “sail.” The absorption by the nucleus of one of the pi-mesons that emanate from this annihilation induces the nuclear fission. Over the past few years, improvements to the original design have brought this concept much closer to becoming a reality.
However, before this plan could be considered feasible, one very important problem with antimatter needed to be addressed: storing it. For those of you who aren’t familiar with antimatter, part of the reason it’s being studied for this application is because it annihilates with ordinary matter to generate large amounts of energy. The problem is, even in the best vacuums humans can create, there is still some matter left, which causes “sublimation” of the antimatter when the antimatter annihilates with the trace gases. One potential solution we recently came up with involves coating an antihydrogen “snowball” (cooled to prevent random collisions with matter) with a thin layer of antilithium. Imagine an open glass jar containing water. After a few days the water will evaporate. If instead the jar is sealed, the water will stay in the jar for centuries.
How to form antilithium-coated antihydrogen snowballs
IT's easy as one, two, three!
Though this is a gross oversimplification of the process, these are the general steps needed to prepare an antimatter snowball:
Step 1: Grow hot anti-H2 molecules
Step 2: Form anti-H2 snowballs
Step 3: Coat snowballs with a thin layer of antilithium
Photo Credit: NASA
Once the above steps are completed, the antimatter snowball can be stored. This will require a very good vacuum and some sort of levitation mechanism. Now, with levitation mechanisms, one has to consider the effects of vibration, cosmic rays, outgassing and potential mishaps. So far, no major roadblocks have been identified with electrostatic levitation (a technique that existed before the Millikan Oil Drop experiment).
