Boron Nitride Nanotube Reinforced Polyethylene Nanocomposite for Experimental Proton Radiation Shielding

Radiation in the space environment poses significant risks to humans and spacecraft electronics, driving the need for advanced shielding strategies to ensure mission reliability. High-energy particles from solar, trapped, and galactic sources cause cumulative damage, including total ionizing dose and displacement damage, as well as stochastic single-event effects that can disrupt or permanently degrade electronic systems. In Earth orbit, satellites are typically protected with approximately 6 mm aluminum shielding, a simple but mass-intensive solution. Reducing shielding mass lowers launch costs, motivating the development of more effective lightweight materials. Hydrogen-rich materials such as high-density polyethylene (HDPE) provide superior mass-specific radiation attenuation compared to aluminum due to hydrogen’s high charge-to-mass ratio, low secondary particle production, efficient energy absorption, and high interaction cross-section. Boron-rich materials, including boron nitride nanotubes (BNNTs), further enhance radiation protection, particularly for thermal-neutron absorption, while improving mechanical performance through high strength-to-weight ratios. However, incorporating high nanotube loadings into structural materials remains a manufacturing challenge. To address this, we developed a bulk nanocomposite laminate fabrication technique involving synthesis of millimeter-long vertically aligned BNNTs, densification to high volume fractions, and infusion with polyethylene under heat and pressure to create a BNNT–HDPE composite containing 35 wt% BNNTs. The material was evaluated using a 2.5 MeV proton beam and benchmarked against aluminum at equivalent areal density, demonstrating improved proton shielding based on mean energy reduction and peak broadening metrics. Results indicate a 25% reduction in shielding mass for proton protection in electronics applications. These findings complement prior results showing BNNT–HDPE performs 700% better in neutron shielding than equal-mass HDPE, the current state of the art for human-rated spacecraft. Together, these results demonstrate substantial improvements in shielding performance for both neutrons and protons, highlighting the potential of BNNT–HDPE as a multifunctional radiation protection solution for human spaceflight and spacecraft systems.