Probabilistic Aeroshell Thermal Response Uncertainty Analysis for the LOFTID Technology Demonstration Mission

A probabilistic thermal margin process has been performed to design the flexible thermal protection system (FTPS) and select entry trajectory constraints given an acceptable risk level for the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) project. Uncertainties exist in atmospheric entry aeroheating environments and the predicted thermal response of thermal protection system (TPS) material. Entry vehicle TPS is typically oversized to mitigate uncertainty by combining conservative bounding reentry flight and TPS thermal response scenarios together. The probabilistic thermal margin process allows engineers to make informed aeroshell design, flight design, and FTPS performance reliability trades while preventing excessive FTPS margin from being applied. This paper describes the uncertainty analysis methodology used to carry out a probabilistic thermal margin process for LOFTID, which was done by running an end-to-end Monte Carlo simulation. The resulting calculated probabilities of critical aeroshell structures exceeding flight allowable temperatures are used to design the FTPS and establish flight design constraints. This probabilistic thermal margin process had never been applied to entry, descent, and landing design for a flown entry vehicle, and it is one of the LOFTID project’s goals to demonstrate its merits.