Aerothermal Ground Testing of Flexible Thermal Protection Systems for Hypersonic Inflatable Aerodynamic Decelerators

ABSTRACT The Hypersonic Inflatable Aerodynamic Decelerators (HIAD) project has invested in ground tests to evaluate the aerothermal performance of various thermal protection system (TPS) candidates for use in inflatable high-drag, down-mass technology. A flexible TPS (FTPS) enables the deployment of large aeroshells which significantly reduce the ballistic coefficient of an entry vehicle allowing a greater mass to be delivered to the ground at higher landing altitude than with a conventional, rigid TPS. A HIAD requires a FTPS capable of surviving the aerothermal entry loads including demonstrate operation of HIAD systems. An overview heat flux, pressure, shear force, and total energy load. Flexible TPS development involves ground testing and analysis necessary to characterize performance of the FTPS candidates prior to flight testing. This paper provides an overview of the analysis and ground testing efforts performed over the last year at the NASA Langley Research Center and in the Boeing Large-Core Arc Tunnel (LCAT). In the LCAT test series, material layups were subjected to aerothermal loads commensurate with peak re-entry conditions enveloping a range of HIAD mission trajectories. The FTPS layups were tested over a heat flux range from 20 to 50 W/cm² with associated surface pressures of 3 to 8 kPa. performed in the 8To support the testing effort a significant redesign of the existing shear (wedge) model holder from previous testing efforts was undertaken to develop a new test technique for supporting and evaluating the FTPS in the high-temperature, arc jet flow. Since the FTPS test samples typically experience a geometry change during testing, computational fluid dynamic (CFD) models of the arc jet flow field and test model were developed to support the testing effort. The CFD results were used to help determine the test conditions experienced by the test samples as the surface geometry changes. This paper includes an overview of the Boeing LCAT facility, the general approach for testing FTPS, CFD analysis methodology and results, model holder design and test methodology, and selected thermal results of several FTPS layups.