Aerothermal–Structural Analysis of a Rocket-Launched Mach 8 Scramjet Experiment: Descent

Abstract

This paper reports on the methodology and results of a weak-coupled aerothermal–structural analysis on the exoatmospheric and descent phase of the Mach 8 SCRAMSPACE flight-test engine. The passively cooled short-duration test engine was manufactured from common engineering materials including a 5 mm-thick aluminum aeroshell, an 8–10 mm aluminum inlet and combustion chamber assembly, and a 4–8 mm-thick carbon-phenolic thrust nozzle. Aerothermal heating and aerodynamic pressure on the external and internal flowpaths, including pulsed (5 Hz) fueling and combustion, were first solved using two- and three-dimensional computational fluid dynamics models. Results from these simulations where then used as boundary conditions to a three-dimensional transient thermal–structural finite element analysis model. The external aeroshell was found to maintain temperatures and stresses to within acceptable limits. Elevated surface temperatures along the internal flowpath were observed; however, the median stresses remained below material failure limits. This analysis indicates that, although the structure weakens and becomes more plastic, the vehicle integrity was maintained until the specified end of the experimental window. Results from this study demonstrate that, with careful design, thin-walled structures made from common engineering materials are suitable for short-duration hypersonic airbreathing flight-test engines without the need of active-cooling technology.