Passive hypersonic boundary layer control: The Potential of an Ultrasonically Absorptive Ceramic for HEXAFLY-INT

Abstract

The potential of ceramic matrix composites (CMC) for passive boundary layer transition control on the hypersonic flight vehicle HEXAFLY-INT is investigated. CMC can be manufactured as ultrasonically absorptive ceramic: for the presented numerical investigations carbon fiber reinforced carbon material (C/C) is used for the passive damping of acoustic second mode instabilities. The analyses are performed with the stability code NOLOT, NOnLOcal Transition analysis, of the German Aerospace Center (DLR). The boundary conditions of the NOLOT code are extended for the application of random porous surfaces and consider the acoustic properties of the C/C. In this paper a trajectory segment of interest for the application of ultrasonically absorptive ceramics on the HEXAFLY-INT hypersonic glider is investigated. For chosen flight conditions and a corresponding test condition of the DLR High Enthalpy Shock Tunnel Gottingen (HEG) detailed stability analyses with NOLOT are performed: this includes the investigation of the second mode damping due to the passive porous ceramic.