Current state-of-the-art (SOTA) methods for the fabrication of thermal protection systems (TPS) for spacecraft is costly, labor-intensive, and limited to on-Earth production. To address these shortcomings, Mainstream, in collaboration with the Design, Research, and Education for Additive Manufacturing Systems (DREAMS) lab at Virginia Tech (VT), proposes to develop a large-format additive manufacturing (AM) system for the in-situ fabrication of a high-heat-flux ablative TPS. The Spacecraft Thermal protection system Additive Manufacturing (STAM) system will consist of a large robotic arm coupled with a direct ink write (DIW) printhead and integrated UV lamp for the large area deposition of a filled thermoset, such as cyanate ester, phenolic, or epoxy-based resin with carbon-based fillers and photoinitiator. This configuration will allow for the precise and reproducible deposition and in-situ curing driven by the curing of the photoinitiator and a secondary thermal reaction through frontal polymerization to cure the TPS layer fully. The STAM system will feature a 6 degree of freedom (DoF) robotic arm with one external axis (a turntable to rotate the spacecraft) to allow for conformal deposition over the entire surface of a spacecraft with up to a 5-m diameter base and a dual-chamber printhead to extrude the 2-part thermoset via a progressive cavity pump. The STAM system will autonomously fabricate a full-scale conformal TPS in-situ cured by two sequential reactions activated directly after deposition without a post-process thermal cure.
Missions involving a spacecraft that enters a planetary atmosphere and experiences the high heating associated with hypersonic flight would benefit from the developments produced in this program. Improving heat shield performance and lowering cost is critical to future missions, including manned missions to the Moon and Mars. The Human Exploration and Operations Mission Directorate (HEOMD), Science Mission Directorate (SMD), and commercial space programs would benefit from the innovation in TPS materials and manufacturing processes proposed.
Hypersonic vehicles currently being developed experience the high heat fluxes and temperatures associated with hypersonic flight. These vehicles would benefit from an improved thermal protection system as there is no existing solution for leading-edge materials that can operate in this demanding environment. This lack of capability is a limiting factor for future hypersonic vehicle development.