Experimental Aerodynamic Investigation of NASA Orion Forward Bay Modifications

Abstract

The design of the Orion Crew Exploration Vehicle (CEV), under development by NASA as the next manned space capsule, relies on staged parachute deployments during atmospheric re-entry in order to decelerate sufficiently for a safe water landing. The parachutes are housed in a compartment on the capsule known as the forward bay. Due to parachute packing density limits and projected CEV weight increases during the design effort in 2009, the size of the forward bay had to be increased, resulting in an adjustment of the CEV’s outer mold line (OML) to accommodate the extra volume. In order to ensure safety of flight, the effect of this change on the aerodynamic characteristics of the CEV had to be evaluated for such an adjustment. The NASA Johnson Space Center (JSC) Applied Aeroscience and CFD Branch tasked the Air Force Academy Department of Aeronautics to accomplish wind tunnel testing and computational fluid dynamics analysis to support the investigation of an OML change at the forward bay on the CEV’s aerodynamic characteristics. The Academy’s subsonic wind tunnel was used to experimentally evaluate these effects. In addition, high-performance computing (HPC) resources at Johnson Space Center were used for computational fluid dynamics (CFD) analysis. Three different OML configurations were tested at varying Mach numbers and angles of attack to determine the effects of OML modification on the aerodynamic characteristics of the CEV. The aerodynamic effects of wind tunnel wall and sting interference were included. Results show that OML modification had only minimal impact on CEV aerodynamic coefficients for 0° to 30° angle of attack. At larger angles of attack, modifications to the forward bay had a greater impact. A larger degree of OML modification from the baseline nominal configuration amplified this effect. Sting/wall effects were found to be primarily dependent on CEV angle of attack. Sting correction curves were determined for and applied to each of the aerodynamic coefficients, improving the prediction of free-air aerodynamics.