Complex-Trajectory Aerodynamics Data for Code Validation from a New Free-Flight Facility

A unique new capability to obtain unsteady aerodynamics data for configurations flying complex trajectories is presented. Supersonic free-flight aerodynamics data for conical frustum-shaped projectiles were obtained in a new aero-ballistic facility at NASA Ames Research Center. The projectiles simulated insulating-foam debris shed from the Space Shuttle's external fuel tank. The data were required by the Space Shuttle Program to validate, prior to the post-Columbia return-to-flight, the 6-DOF/CFD code used to characterize Shuttle ascent-debris aerodynamics and risks. Polyethylene frustums— nominally 3.56 cm in diameter, 0.71 cm long, and 4 grams in mass—were launched into 1- atm air at approximately M=2.8. Their rapidly-decelerating, often highly-lifting, and sometimes tumbling 6-DOF trajectories were recorded by arrays of top- and side-view ICCD cameras. The paper gives samples of the data and details of the substantial challenges and creative solutions associated with obtaining them.