Optimization of Active and Passive Thermal Protection Systems for a Hypersonic Vehicle

The hypersonic vehicle model Michigan–AFRL Scramjet in Vehicle (MASIV) is used to optimize both the active and the passive thermal protection systems on a scramjet-powered generic X-43 waverider. The passive thermal protection system is the NASA ARMOR design; a silicon dioxide insulation layer is sandwiched between a radiation shield and the vehicle titanium skin. The active thermal protection system consists of a heat exchanger on the combustor wall; the coolant is the liquid hydrogen fuel. The portion of the fuel that is used for cooling (and not for propulsion) is recirculated back into the fuel tank, which causes the temperature of fuel in the tank to rise. Gradient-based optimization is performed to determine 1) the minimum insulation thickness distribution required and 2) the optimal coolant mass flow rate and its variation in time. Constraints are that surface temperatures cannot exceed the failure temperatures, and the volume of fuel in the fuel tank cannot exceed the tank volume. The hypersonic vehicle heat transfer model is adaptable and can handle new materials for thermal protection, as they are developed.