Entry System Technology Readiness for Ice-Giant Probe Missions

NASA has successfully developed a new and innovative Heatshield for Extreme Entry Environments Technology, or HEEET, which, at a Technology Readiness Level (TRL) of 6, is ready for use in Ice Giant missions. HEEET is not just a replacement for the legacy full-density carbon-phenolic (FDCP) material, which was used in NASA's Pioneer-Venus and Galileo missions; it is also a more mass efficient and robust alternative, and a technology that has a sustainable manufacturing base. HEEET is a dual-layer, 3-dimensionally woven material. It has a dense outer layer, made of pure carbon fibers, that comes into contact with and protects against extreme entry environments. Below this layer is an integrally woven, lower density insulating layer, made of a blend of carbon and phenolic yarn, that reduces heat-conduction to the carrier structure. The present paper describes development of this material, its thermal, structural, and aerothermal testing, production of an engineering test unit at flight scale, and maturation for infusion into missions to various planetary destinations, with a focus on Ice Giant in situ missions. Finally, for representative entry velocities at Uranus and Neptune, and a range of entry masses and flight path angles, margined thicknesses of HEEET are computed. When the limits of heat fluxes and pressures that can be achieved in ground-test facilities, and loom limits, are imposed on these thickness estimates, it is shown that several atmospheric entry missions are possible at the two destinations.