BNNT EDL/Aerocapture Tension Shell Concept

BNNTs are a uniquely well-suited material for a flexible strong fabric with high thermal stability. The ultralight flexible shielding fabrics proposed for the current IRAD program would consist of BNNT materials that have low density (1.4 g/cm3), excellent mechanical properties, exceptional thermal stability (> 800 °C in air and even > 1300 °C in a vacuum) and neutron radiation shielding capability. The BNNT-based shielding fabrics would benefit both of the existing and new effort in entry, descent, and landing (EDL) and advanced TPS system, enabling (1) reduced weight, (2) extreme thermal stability, (3) excellent mechanical durability, (4) excellent thermal emissivity, (5) RF-signal transparency, (6) radiation shielding against neutron, GCR and SPE, and (7) other multifunctional capabilities such as energy harvesting. We have developed and will continue to optimize nonwoven BNNT mats, nanotube alignment, fiber and yarn development, and material tests in a relevant planetary environment. A thermal shielding and flame-retardant BNNT-based fabric will be new to the industry, academia, and government. State-of-the-art thermal protection fabrics are heavy, brittle, multilayer composite systems. BNNTs are available in scalable quantities and are a lightweight alternative (1.4 g/cm2) to state-of-the-art SiC fiber (3.2 g/cm2). Leveraging the strength and flexibility of BNNTs, we are developing a deployable flexible fabric for thermal protection during EDL, and radiation shielding during space travel. The high strength and high thermal stability of BNNT materials are expected to reduce the surface recession rate of the thermal protection membranes. In addition, the high thermal emissivity of BNNT materials would also diminish a radiant heating component while its high thermal conductivity facilitates thermal dissipation throughout the structure. Such an F-TPS for EDL enables significantly greater payloads for inter-planetary journeys, including the journey to Mars. Our material research focus is on a flexible thermal protection fabric that can enable revolutionary EDL concepts and design, such as a single layer flexible thermal protection system. The next step of our research is to utilize our international SAA with NRC Canada (non-reimbursable) to fabricate and test large scale BNNT composites. This international SAA will enable accelerated development of BNNT composites for thermal protection and radiation shielding applications. We will continue research on the alignment of BNNT and BNNT composite mats for structural reinforcement and Hypersonic Materials Experiment Test System (HYMETS) studies with purified BNNT, thicker BNNT, and BNNT composite mats. We will also research the mechanical behavior of BNNT mats before and after HYMETS tests to understand combined thermal and mechanical load effects. We plan to extend the system analysis study with HIAD-2 Team for the tension shell design and continue our collaboration with the HIAD-2 team for understanding of overview, areas of development and leveraging of expertise. From our previously-funded collaboration with Rice University, we will conduct the scale-up study of the BNNT purification method to meet productivity goals for BNNT fiber/yarns. We will keep on academic leveraging with Georgia Institute of Technology to fabricate BNNT-Carbon hybrid fibers for EDL; we will continue microbullet testing for space environmental impact with Rice University; and with SUNY-Binghamton, we are determining high-temperature mechanical properties. The university collaborations are all leveraging and not funded. We have a SAA with BNNT, LLC (licensee of NASA's BNNT technology) to further develop and optimize synthesis production, science, composite fabrication, fiber or aligned material, and characterization and application of boron nitride nanotubes (BNNTs).