X-38 aerodynamics during rapid pitch up

A series of experiments were conducted on the extreme high-angle-of-attack aerodynamics of a model of the X-38 reentry vehicle. These tests were conducted at the University of Illinois low-speed wind tunnel. The 4.7% scale model was constructed in three parts using stereolithography and was sting mounted with a 6-component strain gauge balance to measure the forces and moments. The model positioning system allowed the model to vary in angle of attack from -7° to 95° in three separate angle of attack ranges. The effects of Reynolds number, transition, and flow control were all investigated. Reynolds number, based on body length, was varied from 1.0 × 10⁶ to 1.5 × 10⁶. In addition to the force measurement, pressure data were collected using 99 taps on the body. Surface oil flow visualization was used to define the surface flowfield. The forces and moments collected in the analysis revealed a sharp change in the side force at extremely high angles of attack. Although the position and shape of the spike varied with Reynolds number and boundary-layer state, the change was always apparent. The single strake case demonstrated that the clean and tripped side force change was not insignificant. The dual strake case demonstrated that the phenomena could be controlled by controlling the separation on the side of the forebody.