In-Space Manufacturing Viability of Nanocomposites for the Extreme Space Environment

As human space exploration moves toward a permanent presence on the Moon and Mars, in-space manufacturing offers a pathway to reduce launch mass and cost while enabling customizable production for mission durability. Advanced materials capable of withstanding the extreme space environment are essential. Nanocomposites reinforced with carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) provide high strength-to-weight ratios and multifunctional properties, including the thermal emissivity, and electrical conductivity of CNTs and the radiation shielding capability of BNNTs. These attributes make them strong candidates for space-relevant applications, such as ablative thermal protection systems, ionizing radiation shielding, and lunar dust mitigation. Current state-of-the-art nanocomposites incorporate less than 15 vol% nanotubes, limiting performance due to agglomerations and voids. In contrast, the bulk nanocomposite laminating (BNL) process achieves${4 0 - 5 0} \text{vol} {\%}$aligned CNTs or BNNTs, yielding superior structural and functional properties. The BNL process synthesizes and densifies aligned nanotubes, infuses a matrix material, and applies heat and pressure to produce void-free nanocomposites. Polyethylene-matrix nanocomposites manufactured with$40 \text{wt} \%$BNNTs have been demonstrated to improve the neutron radiation shielding percentage by 7 X compared to a baseline of polyethylene. In-space manufacturing using BNL could enable mission-specific material customization and timely repairs, such as restoring heat shield integrity before re-entry. To assess its feasibility in reduced gravity, the gravity-dependent infusion step was investigated on a Zero-G parabolic flight using polysiloxane, an ablative ultra-high-temperature resin. In microgravity, infusion relies solely on capillary pressure rather than gravity-driven flow contribution. Post-flight characterization of CNT and BNNT nanocomposites by scanning electron microscopy and energy dispersive X-ray spectroscopy demonstrated successful resin infusion under microgravity, supporting the potential of in-space nanocomposite manufacturing for future exploration missions.