Aero-Optical Demonstration Test in the AEDC Hypervelocity Wind Tunnel 9,

Abstract : Hypersonic endo-atmospheric interceptors must maneuver over a variety of flight environments. Generally, these interceptor missions require flight below Mach 8 for some portion of the mission. Hypervelocity intercepts can occur at high altitudes but are more stressing at the lower altitude, high Reynolds number conditions. To obtain the high accuracy needed for hit-to-kill, endo-atmospheric interceptors use optically based seeker systems. These optical seekers rely on precise knowledge of the interceptor position to select an aimpoint. Optical aberrations caused by hypersonic flight can distort or shift the image position on the focal plane enough to add uncertainty in the position and cause the interceptor to miss. These image distortions are typically referred to as aero-optical effects. To lower risk to the program, the thermal and structural response and the optical aberrations on the seeker window should be assessed through ground testing. This type of ground testing is dependent on duplicating flight parameters. In addition, thermal/structural testing requires long run times consistent with end-game scenarios. Evaluation of interceptor performance in a ground test facility that can provide full flight duplication for seconds of run time will greatly reduce risk to these programs. An aero-optics test capability has been demonstrated in Hypervelocity Wind Tunnel 9 (Tunnel 9) at the Arnold Engineering Development Center (AEDC). In this facility, flight aerodynamic conditions can be matched for run times of 6 seconds, thereby duplicating the aerothermal/structural response of the window. This facility creates an ideal environment to characterize and evaluate seeker system aero-optical effects. This paper outlines the significant verification and validation processes developed for feasibility demonstration. It provides an overview of the important aspects and results of the program to date.