Low-density Flexible TPS Materials for Hypersonic Vehicles

The innovation of this proposal “Low-Density Flexible TPS Material for Hypersonic Vehicles” is a new class of flexible thermal protection system materials using the best-of-its-class UHTR resin. Building a new ablative system from the ground up can take upwards of a decade, requiring substantial funding and resources. One of KAI’s strengths is its ability to use system integration to unify the best aspects of existing technology into a novel and superior technology. KAI proposes the integration of two well-matured systems, NASA’s flexible PICA ablative, and Techneglas’ polysiloxane resin. The foundation for this new class of low-density flexible TPS is currently being built, with (i) KAI, Techneglas, and NASA Ames set to sign a Space Act Agreement and (ii) the pending approval of a KAI NASA ACO proposal to push this technology from a TRL 4 to a TRL 5 status with arc jet evaluation. Many modern ablators continue to use phenolic resin, the world’s first synthetic polymer which has been in use for over a century. A major advantage that comes with being the first to market, is that phenolic resin is perhaps the most characterized resin system. This makes it a convenient choice when time and funding are unavailable to characterize a new resin system. However, when compared to modern resins in metrics critical to ablatives, phenolics generally underperform. Char yield is one of the most important metrics used for qualifying a material’s ablation performance. NASA defined char yield as a material’s mass remainder at 1,000ºC after TGA evaluation in nitrogen with a heating rate of 20ºC/min. When a resin ablates it releases hot gas and leaves a carbonaceous char structure on the material surface. This char layer plays an integral role in the ablation performance of the material, serving protective and insulative functions. The KAI team has been studying this phenomenon for over 40 years and holds an extensive and proprietary library of char characteristics for today's’ leading high-temperature resin systems. UHTR resin has by far the highest char yield of any material studied by KAI with a value of 88-89% (compared to 62% for phenolic). KAI has been studying the performance of these UHTR composites for 5 years and is continuing to push towards its commercialization as a versatile ablative material. For Phase I, KAI will formulate and screen 12 flexible ablators using the UHTR system. These flexible ablators will use infiltration of a cured resin powder into high-performance felts, allowing the system to retain the flexibility of the fiber while obtaining the well-balanced ablation properties of the UHTR resin. For Phase II, KAI will validate its top-performing flexible ablators at the NASA Ames Arc Jet Complex and use the data to validate the predictive material response ablation model. Throughout this proposal, KAI will continue to advance its collaboration with interested government agencies and related contractors, such as Lockheed Martin and Raytheon. Approved for Public Release | 20-MDA-10643 (3 Dec 20)