Design of high-temperature multi-layer insulation for reusable launch vehicles

Heat transfer through high temperature multi-layer insulation for application in metallic thermal protection systems for reusable launch vehicles was modeled based on fundamental principles. The combined radiation and conduction heat transfer through fibrous and multi-layer insulations was modeled numerically using a finite volume approach and a two-flux formulation for radiation heat transfer. A steady-state thermal testing apparatus was used to measure effective thermal conductivity of fibrous and multi-layer insulations over the temperature range of 20 to 1000°C and an environmental pressure range of 1 × 10−4 to 760 mm of Hg. A transient thermal testing apparatus was used to simulate re-entry aerodynamic heating conditions for fibrous and multi-layer insulation. The steady state and transient measurements were used to validate the computational model for combined radiation and conduction heat transfer in both fibrous and multi-layer insulations. A design of experiment analysis was used to optimize the design of multi-layer insulation subject to a typical atmospheric re-entry heating profile. The research showed that using a 2 mm reflective foil spacing and locating the foils 2 mm away from the hot boundary is the optimum design for multi-layer insulations. The research showed that insulation mass savings of 12 percent may be achieved by using the optimized multi-layer insulation design with eight foils instead of fibrous insulation.