As a spacecraft enters a planetary atmosphere at hypersonic speeds, it is subjected to extreme temperatures and pressure. A greater understanding of how spacecraft materials respond and the risks of failure during those critical minutes is vital to the continued success of space exploration missions.
In studying the response of materials to intense heat, aerospace engineering Ph.D. candidate Vishnu Oruganti is specifically studying the silicone filler that bonds together the tiles of a heat shield. The material exhibits a peculiar behavior; it slightly swells, then shrinks, softens, and bubbles. And under the harshest temperatures it transforms into a glassy char. This cascade of physics poses great challenges to thermal engineers at NASA who try to safely protect entry systems.
“The objective of my project is to build a physics-based model for pyrolyzing intumescent ablators that can capture the main elements of room temperature vulcanizing silicone,” Oruganti said. “This model will be implemented and tested in an ablator response toolbox under development at NASA and will be documented as a general formulation for testing in engineering design tools.”
Oruganti said the model will be built upon tailored experiments on material decomposition, on microstructure characterization, and calibrated using advanced numerical techniques. The project will culminate with testing and validating the model against flight data from Mars and Moon return missions and plasmatron experiments at the University of Illinois Urbana-Champaign.
“Modeling the complex phenomena that characterize the room temperature vulcanizing silicone behavior under entry conditions will help achieve better understanding of differential ablation that occurs at tile joints and predicting boundary layer transition of the entry flow. This model can then be used to optimally design the heatshield and embedded instrumentation for various entry missions,” he said.
Vishnu Oruganti received a NASA Space Technology Graduate Research Opportunities award. He is a Ph.D. candidate in aerospace engineering at the University of Illinois Urbana-Champaign working with Professors Francesco Panerai and Marco Panesi in the Center for Hypersonic and Entry System Studies group at UIUC. The NASA fellowship includes funding for four years of his graduate studies. It also supports visiting technologist experiences at NASA, an invaluable opportunity for students to get exposure to the Agency.
“This fellowship is a unique opportunity to continue our long-standing collaboration with the EDL community at NASA,” Panerai said. “We want to have an impact on their mission, and train our best and brightest to tackle their challenges. Vishnu definitely fits this profile and I am proud of his achievements so far.”
During the summer of 2021, Oruganti had a remote internship under Jeremie Meurisse at NASA Ames.
“It was always my dream to work for NASA and getting to intern with one of the most prominent groups in EDL made me extremely happy,” Oruganti said. “Through the internship, I was able to gain deep knowledge in hypersonics and material modeling. As part of my project, I tested numerical simulations against arcjet data, and real-flight MSL data. This unique opportunity to work across the full spectrum of computational, experimental, and flight data analysis was truly rewarding. And this summer, I get to do my second Ames internship, this time in person in California. I am thrilled to meet many rocket scientists and learn from them.”