The objective of Phase I is to design, fabricate, characterize, and test ultrasonically absorptive aeroshell materials that successfully damp the second (Mack) mode instability to delay boundary layer transition (BLT) on hypersonic boost-glide weapons during the pull-up and glide phases. HySonic Technologies, LLC will experimentally and numerically assess the complex acoustic absorption coefficient, S(omega), of existing porous carbon-carbon (C/C) composites manufacturable in the US (1st generation C/C). The desired S(omega), achieving optimal transition delay for the pull-up and glide phase of the hypersonic booster glider, will be determined via steady and unsteady numerical simulations for the tip geometry of interest (to be revealed by the DON). During the option phase, a 2nd generation C/C coupon-sized material will be designed and manufactured with a custom-made porous structure established during the base period to achieve the desired aerodynamic performance; new benchtop experiments will be carried out on 2nd generation samples, as well as preparatory numerical simulations for quiet tunnel testing at the Boeing Air-Force Mach 6 Quiet Tunnel (BAM6QT) at Purdue, scheduled for Phase II. Subject to availability of funds, a first generation conical-shaped C/C sample will be manufactured for testing in BAM6QT during the option period.
Benefit: The outcome of the project will be the design of a new aeroshell capable of integrating acoustic damping of second-mode waves with preexisting thermal and structural resistant capabilities. Potential customers to which this technology will be licensed are Raytheon and Lockheed Martin, for both missile and transport vehicle design. Similar technology developed in Germany (DLR) has proven to delay hypersonic transition by doubling the extent of the laminar region of a cone with C/C. Increasing the surface exposed to laminar flow by 300%, while allowing for additional forms of thermal control, e.g. active cooling via bleeding through the porous walls at the tip. This increases confidence that such methodology can improve the aerodynamic efficiency (lift-to-drag ratio) of hypersonic vehicles and be successfully brought to market.
Keywords: Impedance Boundary Conditions, Impedance Boundary Conditions, Hypersonic Transition Delay, Passive Flow Control, Carbon/Carbon Ceramics
