Canadian Nuclear Laboratories to Develop Radiation-Blocking Nanomaterials for Long-Term Space Travel

The Canadian Nuclear Laboratories has been awarded a contract to produce new radiation-resisting space-focused materials for the Canadian Space Agency. The two-year contract for $1 million, with an optional extension to a third year, is part of the Canadian Space Agency's (CSA) Space Technology Development Program. CNL will be looking into how to create new “nanomaterials” that durably protect against radiation while being lightweight enough to be feasibly launched into space. In an interview with SpaceQ, project director Zahra Yamani discussed the project and what they’re looking to accomplish. Radiation in Space She said that managing radiation is a serious concern in space, and is likely to become even more so as the space industry moves into cislunar space and farther. While radiation is an issue on Earth—it’s a growing issue in chip design—it’s far more of a concern in space. On Earth, we’re protected from solar particle events (SPEs) and galactic cosmic rays (GCRs) by the Earth’s atmosphere and magnetosphere. The atmosphere blocks harmful particles from entering, while the magnetosphere reflects and redirects potentially dangerous cosmic radiation. In space, none of those protections apply. Spacecraft in low Earth orbit may benefit slightly from the magnetosphere, but anything beyond it is exposed to the full brunt of cosmic particles and radiation. And while large geosynchronous satellites can be designed to mitigate these effects, it remains a significant concern for crewed cislunar and interplanetary spaceflight. On Earth, we also deal with terrestrially-produced radiation through other means, like the water used in nuclear power plants and the lead used by x-ray technicians. Those solutions are either difficult or unfeasible in space due to the weight; getting the necessary volume of lead and/or water into orbit would be prohibitively expensive. "Active" protection that uses magnetic fields, similar to Earth’s magnetosphere, is also not really an option; Yamani said that "the energy you need for replicating the magnetic fields around your spacecraft…is not feasible with current technology." Space travel requires a different solution. That’s what CNL is being paid by the CSA to explore, in the hopes that Canadian research can provide that solution to this pressing issue. Yamani said that the focus is on "advanced multi-functional nanomaterials" intended to tackle SPEs, GCRs, and whatever other radiation threatens the spacecraft and its crew. Interactions and integrity Yamani elaborated on how this issue is even more complex than it seems, pointing to two key dilemmas: secondary radiation and material integrity. The first problem is surprising, but the radiation that comes from the spacecraft itself can be as damaging as the radiation coming from outside of it. As cosmic radiation hits the spacecraft, it is possible—even likely—that materials found in the spacecraft will interact with that radiation. Some will produce radiation of their own. Protections that could work against the radiation coming from space may not work against the types being generated by these materials, and these second-order effects are difficult to predict. Any materials being developed will need to protect against these secondary sources as well. The other problem is less surprising, but will require a lot of work to resolve. Just as the heat shield on a re-entry vehicle is burned away as it passes through the atmosphere, materials exposed to space radiation can and likely will be affected by it. Any materials the CNL works with will not only need to be tested for their strength, weight, conductivity, flammability, toxicity and other factors, but will also need to be tested again and again as they’re being exposed to different types of radiation. Will the protective materials become weak, brittle, or toxic due to the radiation? Could they become radioactive themselves? Astronauts will need to know, and the CNL needs to sort out those issues before it’s put to use. Nanomaterials This whole process is slated to last two years, with an extra year as a possibility. Yamani admitted that it’s still early days yet, but as stated earlier, she said that their focus is on nanomaterials: materials where at least one dimension can be measured between 1 and 100 nanometers. Nanomaterials are getting a lot of attention—lattice-shaped carbon nanotubes are being hailed for their strength and excellent conductivity—as a new and potentially fruitful branch of cutting-edge materials science. In the case of radiation protection, carbon nanotubes wouldn’t work. Yamani said that a different type may, though. Through previous research with the National Research Council (NRC), they’ve discovered that Boron-Nitride Nanotubes (BNNTs), which include boron and nitrogen in their lattices, may have the properties they’re looking for. Their study discovered that while a composite material including BNNTs was degraded by gamma irradiation, the BNNTs themselves “did not show significant change”, as “the elastic modulus and the ultimate tensile strength of the nanocomposites did not exhibit significant change”. Boron is also, Yamani explained, potentially valuable in protecting against radiation. Cosmic radiation can produce destructive free neutrons which can do damage to a spacecraft and its crew. Boron can absorb slower “thermal” neutrons—she said it has “a very high absorption cross-section for thermal neutrons,” and she said that other lighter elements like hydrogen can neutralize “fast” neutrons. Yamani said that Lithium is also a good candidate for the composite, which was borne out by earlier research in 2019 into Lithium Hydride in shielding. And they’re looking at other kinds of radiation, like proton radiation and gamma rays. The CNL’s job will be to discover what composition of elements and materials can be incorporated with the nanotubes to block both cosmic radiation and the particles that it can generate. She said that even heavier materials like lead “could be interleaved into the fabric” of the lightweight boron nitride nanotubes, providing additional protection while still keeping the composite comparatively lightweight. In CNL’s press release, Yamani characterized it as “tactical elements and configurations.” When asked, she reiterated that framing of materials-science-as-strategy, and that “the choice of these tactical elements” will help dictate their ultimate choice of materials for testing. A Long Process Yamani granted that it’s still early days. While they’ve done the work with NRC on BNNTs, and there is some other research that they can draw on, they’re still at the beginning of a long process to develop these materials. She said that the project will start off with heavy and detailed computer modeling. While computer modeling is not going to capture all the idiosyncrasies of the material before, during, and after its irradiation, it can provide useful guidance on what’s working and what isn’t. Yamani said that CNL has access to “a variety of simulation models”, including MCNP (Monte-Carlo N-Particle Transport Codes), CERN’s “GEANT4” particle simulation toolkit, and the FLUKA (FLUktuierende KAskade) simulation package. All of these are used to simulate the transport of particles (like radiation) through various materials, including simulating the physics of each of the projectile particles’ collisions. CNL will use these tools to simulate different materials, iterating on what works, discovering these new “tactical elements and configurations” until they find appropriate candidates. Once that’s done, she said that "we will get [candidate samples] fabricated at nano-fabrication facilities at NRC." CNL will carefully test their physical characteristics, then they’ll begin living up to the “nuclear laboratory” moniker, exposing the candidates to all manner of different kinds of radiation. Yamani cautioned that no decision has been yet made on which facilities could be used for this, but she mentioned Chalk River Laboratories, the Reactor Materials Testing Laboratory at Queen’s University, and the Royal Military College’s SLOWPOKE-2 research reactor as possibilities. Owing to the heavy focus on simulation, Yamani said this irradiation process will likely only start sometime in the second year of the project. After irradiation, CNL will not only check to see if the material successfully blocked or scattered the radiation, but also repeat all the physical measurements they did earlier. They’ll be testing for how and whether the materials were degraded by the irradiation, to determine exactly how long they’ll last in space. Will they be long-lasting, or will there need to be consistent replacements? Is there a “sweet spot” of cost, weight, protection and durability? That’s their issue. If and when the proper materials are found, Yamani said that they will begin exploring where and how the materials can be used, and reaching out to NRC and its industry partners about mass production. She mentioned shielding for spacecraft as one example, but pointed to the non-conductivity of BNNTs as a possible way to use them in electronics. She also said they could be used in spacesuits, and perhaps even in clothing. Nothing is off the table for these nanomaterials and their “tactical elements and configurations.” They could change human spaceflight. For CNL, it’s just a question of finding the right ones.