KY EPSCoR: Improving Heat Shields for Atmospheric Entry (Martin Scope)

The recent success of the SpaceX Dragon capsule marks the beginning of a new era in space exploration: technology necessary to safely land spacecraft returning from Low Earth Orbit (LEO) has reached a maturity and level of confidence for use by industry. However, as NASA sets goals for future solar system exploration, vehicles must travel at increasingly higher velocities, and enter planetary atmospheres with significantly different compositions or densities. Vehicles will need to decelerate considerably to land on a planet's surface, typically using "friction" generated by the planet's atmosphere. Kinetic energy of the vehicle is transformed into heat, which is transferred into the surrounding gas. Some energy reaches the vehicle surface and, to keep the vehicle intact, the exposed vehicle surface is shielded by way of a Thermal Protection System (TPS). Higher velocity entries required for interplanetary exploration require increasingly sophisticated TPS. Research pertaining specifically to the ablative materials used for TPS is key to NASA's technology development, with TPS mentioned in 7 of 14 space technology roadmaps for objectives including near- Earth asteroid and Mars missions as well as extreme-environment atmospheric entry. Although immensely successful, recent data from the Mars Science Lab entry confirms the need to better understand and model the complex aero-thermal environment of TPS material interaction with the flow field. The goals of the proposed study include developing the underlying high fidelity tools needed for detailed characterization of the near wall composition and flow. The proposed research activity will improve our ability to model and predict deterioration of TPS and associated effects on the surrounding flow field. Specifically, we seek to investigate surface reactions and spallation and their influence on near wall flow, including surface roughness and pyrolysis gas injection effects on boundary layer turbulence structure and transport. The chemical composition of the boundary layer will also be examined by taking into account effects of spalled particles ejected from the ablated surface. High-fidelity numerical simulations will be possible using a GPU-accelerated in-house aerothermodynamic CFD code coupled with particle tracking capabilities and material response. Research will be conducted with close collaboration between academic and NASA partners. Experiments will be conducted in a specialized wind tunnel at the University of Kentucky and the HYMETS facility at NASA Langley. NASA Ames researchers will collaborate with material response codes development and NASA Johnson researchers will collaborate with coupling methods, a key issue for integration of turbulence models into the numerical code. In Kentucky, we will develop important computational models of atmospheric entry, build a unique experimental infrastructure, leverage a new supercomputer facility, increase specialized knowledge of early career faculty, and generate collaboration with the state's HBCU. The new particle tracking system will be state of the art, providing a significant infrastructure investment that increases flow-field measurement capabilities and supports future funding success. The work complements Kentucky's recent investments in small satellite technology. All four NASA Mission Directorates benefit by advancing aeronautics and space launch capability, helping overcome high-priority technical challenges, and aiding scientific research via improved landing systems for heavier scientific instruments. It has potential to assist NASA Technology Demonstration Missions and commercial spaceflight partnerships, improve safety for future astronauts and space passengers, and enable potential spinoff technology for US industries. Alexandre Martin, Sc-I