Pressure Sensitive Paint Measurements on a Space Shuttle Model with the Luminescence Lifetime Technique

The luminescence lifetime technique was used to make pressure-sensitive paint (PSP) measurements on a 3% Space Shuttle model in the NASA Ames 9x7ft Supersonic Wind Tunnel. This work was done in support of the Space Shuttle "return to flight" activity. In order to reduce the risk of foam shedding from the Space Shuttle External Tank (ET) and striking the Orbiter, design changes were made to the area surrounding the forward Orbiter attachment point (referred to as the Bi-Pod). PSP was used to investigate the pressure field on the modified ET, both to verify that pressures did not exceed safe limits and to validate CFD (Computational Fluid Dynamics) calculations. PSP data were obtained on the top forward portion of the ET and the Orbiter forward fuselage. Data were taken for several model attitudes of interest at Mach numbers between 1.55 and 2.5. Image data were mapped onto a three-dimensional surface grid both for comparison with CFD and for integration of pressures to determine forces on individual components of the ET. Luminescence lifetime measurements were made using strobed LED (light-emitting diode) lamps to illuminate the PSP and fastframing interline transfer cameras to acquire the PSP emission.