A.: X-33 Hypersonic Aerodynamic Characteristics

Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will build and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit (SSTO), reusable launch vehicle (RLV). A 0.007-scale model of the X-33 604B0002G configuration was tested in four hypersonic facilities at the NASA Langley Research Center to examine vehicle stability and control characteristics and to populate an aerodynamic flight database i n the hypersonic regime. The vehicle was found to be longitudinally controllable with less than half of the total body flap deflection capability across the angle of attack range at both Mach 6 and Mach 10. At these Mach numbers, the vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 degrees) hypersonic flight attitudes. This configuration was directionally unstable and the use of reaction control jets (RCS) will be necessary to control the vehicle at high angles of attack in the hypersonic flight regime. Mach number and real gas effects on longitudinal aerodynamics were shown t o be small relative to X-33 control authority. Nomenclature Bref lateral reference length CA axial-force coefficient CD drag-force coefficient CL lift-force coefficient CL0 lift-force coefficient at 0 deg angle of attack Cl rolling-moment coefficient Clb rolling-moment derivative Cm pitching-moment coefficient Cn yawing-moment coefficient Cnb yawing-moment derivative CN normal-force coefficient CY side-force coefficient Lref longitudinal reference length p ¥ static pressure of free stream, psia pt tunnel stagnation pressure, psia q ¥ free stream dynamic pressure, psia Re/ft free stream unit Reynolds number Sref reference area T ¥ static temperature of free stream, ¡R Tt tunnel stagnation temperature, ¡R a angle of attack, deg b angle of sideslip, deg dbf body flap deflection, deg del elevon deflection, deg DC m increment in pitching-moment coefficient g ratio of specific heats r2/r ¥ shock density rati