Radiation Shielding in Space
12.22.21 | Wednesday | Liv Weiner
Blocking space radiation is one of the critical concerns for the continued human presence in space. This is especially pronounced in deep space.
Outside of low earth orbit (LEO), Earth’s protective magnetosphere no longer operates, resulting in a much higher flux of radiation. The deep space radiation environment consists of two major contributors: low-flux but highly energetic galactic cosmic rays (GCRs) and random bursts of energetic particles from the Sun, known as solar particle events. These bursts range in intensity, from benign to extremely dangerous (i.e. entering the Chernobyl turbine hall after meltdown).
This combined space radiation environment can cause acute effects, such as radiation sickness, as well as long-term consequences including cardiovascular disease, central nervous system disorders, and cancer.
Radiation from Solar Particle Events
Solar particle events (SPE) are unpredictable and occur at a frequency that is dependent on the 11-year cycle of the Sun. Because of their unpredictability, it is important that there is always protection nearby- either in the form of a heavily shielded area of a spacecraft or in the form of protective equipment. If on the lunar surface, even a lava tube might do.
There are many methods of blocking space radiation. They include active and passive methods of radiation shielding. Active methods of space radiation shielding employ electric and magnetic fields to deflect the charged particles away from the crew volume before interacting with the spacecraft material. The result is very similar to the protection we enjoy due to Earth’s magnetic bubble.
Theoretically, active shielding is the best possible solution since it reduces the likelihood of secondary particle generation. However, the application of active shielding in space-like conditions is challenging from an engineering point of view: the amount of electric and magnetic fields required to deflect highly energetic charged particles is in the range of hundreds of megavolts.
Although some advanced research is ongoing to reduce the requirements for such fields to be effective, active shielding is not yet a reality, leaving us with passive shielding for now.
Shielding Material of Choice for Space Radiation: Not Lead
For space radiation shielding, low-Z materials with a low density of neutrons and the highest density of electrons per atom are preferred. Hydrogen, for example, is the best material for shielding against space radiation as it has the highest density of electrons per nucleon and no neutrons.
An effective radiation shielding material should be stable, nontoxic, and able to withstand impacts that can be encountered in space. Therefore, the materials of choice are hydrogenous materials such as structurally stable polymers (e.g. polyethylene).
With that said, radiation protection requirements differ between proton- and heavy-ion-dominated environments (like deep space) and electron-rich environments (such as Jupiter’s atmosphere).
There have also been some concepts for using regolith of the Moon and possibly lava tubes there or on Mars as temporary habitats.
These ideas may soon become a reality for the sustenance of human lives on the surface of such celestial bodies.
Space Radiation Vests
Radiation protective vests are also being developed to shield astronauts from large solar particle events, both in spacecraft and on the surfaces of Mars or the Moon when outside habitat protection.
These radiation protective vests can provide protection to the astronauts and allow them to perform critical mission-related tasks outside the protection of a heavily shielded environment such as a storm shelter or other confined areas.
The AstroRad radiation vest is an example of such a solution. Its shielding components are composed of high-density polyethylene – one of the most effective and safe low Z materials. Another advantage of these vests is that they conform to the body’s anatomy, being thicker in areas requiring more shielding (i.e. selective shielding).
The drawback with a material such as polyethylene is its rigidity. This is overcome in the AstroRad solution by hexagon-based assemblies composed of thousands of independent hexagonal columns embedded in an elastic textile, as shown in the image below.
Additionally, this structure allows for accounting of the body’s self-shielding attributes by implementing hexagons of specific lengths for each point on the torso, based on the thickness and density of the underlying tissue at that point.
So- we know vests are an option. But where is the proof that they actually work? Well, in the case of AstroRad, it has already flown to the International Space Station and, separately, around the Moon aboard Artemis I. These studies have demonstrated the comfort and efficacy of the solution.
So, next time you consider a trip to deep space, know the options. There is no complete solution to this challenge, but tools do exist that can make your trip reasonably safe.
Liv is a content writer and scientific intern at StemRad, where she helps communicate complex scientific topics to diverse audiences. A graduate of Los Altos High School, she excelled in advanced life science coursework, conducted hands-on research, and mentored peers in STEM. Liv aspires to a career in biomedical research to advance human health.
