X-33 Hypersonic Aerodynamic Characteristics

Lockheed Martin Skunk Works, under a cooperative agreement with NASA, will design, build, and fly the X-33, a half-scale prototype of a rocket-based, single-stage-to-orbit, reusable launch vehicle. A 0.007-scale model of the X-33 604B0002G configuration was tested in five supersonic/hypersonic facilities at the NASA Langley Research Center to examine vehicle aerodynamic characteristics and to establish the aerodynamic flight database for the hypersonic regime. Effects of Mach number and specific heat ratio on hypersonic aerodynamic characteristics were also studied. These results were complemented with computational aerodynamic data, experimental configuration buildup information, and various types of surface and flowfield visualizations to enhance the understanding of experimentally observed aerodynamic trends. Data at both Mach 6 and Mach 10 show the baseline configuration achieves a maximum hypersonic L/D of approximately 1.2 between 20 and 30 deg angle of attack. With the center-of-gravity location at 66% of vehicle reference length, the configuration 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. The vehicle also was shown to be longitudinally stable or neutrally stable for typical (greater than 20 deg) hypersonic flight attitudes. At Mach 6 and Mach 10, the baseline configuration demonstrated positive dihedral effect (roll stability) but was directionally unstable. Effects of Mach number on longitudinal aerodynamics were shown to be small relative to X-33 control authority. Effects of specific heat ratio on vehicle pitching moment characteristics were shown to be significant at higher angles of attack, but with a maximum flight Mach number of approximately 10, real-gas phenomena are not expected to occur for the X-33's suborbital flights.