RAREFIED-FLOW TRANSITION REGIME ORBITER AERODYNAMIC ACCELERATION FLIGHT MEASUREMENTS

Acceleration data taken for the first time from the orbital accelerati on research experiment during re-entry on Space Transportation System- 62 have been analyzed using in situ calibration factors, The re-entry data include the flight regime from orbital altitudes down to about 90 km, which covers the free-molecule-flow regime and the upper altitude fringes of the rarefied-flow transition into the hypersonic continuum , Ancillary flight data on Orbiter position, orientation, velocity, an d rotation rates have been used in models to transform the measured ac celerations to the Orbiter center of gravity, from which aerodynamic a ccelerations along the Orbiter body axes have been calculated, Residua l offsets introduced in the measurements by unmodeled Orbiter forces a re identified and removed, The resulting aerodynamic acceleration meas urements along the Orbiter's body axis and the normal to axial acceler ation ratio in the free-molecule-flow and transition-flow regimes are presented, and there is excellent agreement when compared with numeric al simulations from three direct simulation Monte Carlo codes, Also, t here is good agreement with a direct comparison between the experiment flight data and an independent microgravity accelerometer experiment, the high-resolution accelerometer package, which also obtained flight data on re-entry during the mission down to about 95 km.