One of the biggest challenges of working and living in space is the threat posed by radiation. In addition to solar and cosmic rays that are hazardous to astronauts’ health, there is also ionizing radiation that threatens their electronic equipment. This requires that all spacecraft, satellites, and space stations that are sent to orbit be shielded using materials that are often quite heavy and/or expensive.
Looking to create alternatives, a team of engineers came up with a new technique for producing radiation shielding that is lightweight and more cost-effective than existing methods. The secret ingredient, according to their recently-published research, is metal oxides (aka. rust). This new method could have numerous applications and lead to a significant drop in the costs associated with space launches and spaceflight.
The research team’s study appeared online and will be included in the June 2020 issue of the scientific journal Radiation Physics and Chemistry. The study was conducted by Michael DeVanzo, a senior systems engineer at Lockheed Martin Space, and Robert B.Hayes, an associate professor of nuclear engineering at North Carolina State University.
Put simply, ionizing radiation deposits energy onto the atoms and molecules with which it interacts, causing electrons to be lost and producing ions. On Earth, this type of radiation is not an issue, thanks to Earth’s protective magnetic field and dense atmosphere. In space, however, ionizing radiation is very common and comes from three sources – galactic cosmic rays (GCRs), solar flare particles, and Earth’s radiation belts (aka. Van Allen Belts).
To protect against this type of radiation, space agencies and commercial aerospace manufacturers will typically encase sensitive electronics in metal boxes. While metals like lead or depleted uranium provide the most protection, this kind of shielding would add a significant amount of weight to a spacecraft.
Hence why aluminum boxes are preferred, since they are believed to provide the best tradeoff between a shield’s weight and the protection it will provide. As Prof. Hayes explained, he and DeVanzo sought to investigate materials that could provide better protection and reduce the overall weight of spacecraft further:
“Our approach can be used to maintain the same level of radiation shielding and reduce the weight by 30% or more, or you could maintain the same weight and improve shielding by 30% or more – compared to the most widely used shielding techniques. Either way, our approach reduces the volume of space taken up by shielding.”
The technique he and DeVanzo developed relies on mixing powdered oxidized metal (rust) into a polymer and then incorporating it into a common coating that is then applied to electronics. Compared to metal powders, metal oxides offer less shielding, but are also less toxic and don’t pose the same electromagnetic issues that could interfere with a spacecraft’s electronics. As DeVanzo explained:
“Radiation transport calculations show that inclusion of the metal oxide powder provides shielding comparable to a conventional shield. At low energies, the metal oxide powder reduces both gamma radiation to the electronics by a factor of 300 and the neutron radiation damage by 225%.”
“At the same time, the coating is less bulky than a shielding box,” Hayes added. “And in computational simulations, the worst performance of the oxide coating still absorbed 30% more radiation than a conventional shield of the same weight. On top of that, the oxide particulate is much less expensive than the same amount of the pure metal.”
In addition to reducing the weight and cost of space-based electronics, this new method could potentially reduce the need for conventional shielding on space missions. Looking ahead, DeVanzo and Hayes will continue to fine-tune and test their shielding technique for various applications and are looking for industry partners to help them develop the technology for industry use.