Investigation of Orion Re-Entry Drogue Chute Aerodynamic Characteristics

Abstract

The Orion Crew Module (CM) is currently under development by NASA and is scheduled to replace the soon-retiring Space Shuttle. During atmospheric reentry a staged parachute deployment system will provide the final deceleration for a safe water landing. Once deployed, dual drogue chutes reside in the wake of the CM. The separated unsteady nature of the CM wake reduces the drogue chutes’ ability to create drag. For safety of flight, the drogue chutes must be able to produce enough drag to decelerate the CM to the proper flight conditions before the main chutes open. Initial computational predictions by NASA Johnson Space Center (JSC) Applied Aeroscience and Computational Fluid Dynamics branch indicated approximately a 40% reduction in drag produced on the drogue chutes while in the wake of the CM when compared to freestream conditions. NASA JSC tasked the Air Force Academy Department of Aeronautics to experimentally evaluate the drag loss on the drogue parachutes due to the wake of the CM using the USAFA Subsonic Wind Tunnel. Additional flow investigation was performed using computational fluid dynamics and water tunnel testing. Although the CM utilizes dual drogue chutes, all testing was conducted on a single rigid drogue chute model in the wake of the CM model. Two different rigid drogue chute models were tested separately in the wind tunnel for both freestream conditions and in the wake of the CM. Using force and moment measurements obtained during testing, the drag loss on the drogue parachute resulting from the wake of the CM was defined. With the CM mounted at an angle of attack (AOA) of 180o, the maximum drag reduction when compared to freestream conditions was 6.13% for the “original” drogue chute model and 6.9% for the “new” drogue chute model. The maximum drag reduction occurred directly behind the CM. With the CM mounted at 160o AOA, the maximum drag reduction on the “original” drogue chute model was 11.3%, and 11.8% for the “new” drogue chute model when compared to freestream conditions. For this configuration, the maximum drag reduction occurred approximately 1 CM heat shield diameter offset to the left of CM centerline. Although the drag coefficient varied between the “new” and “original” models, the percent reduction in drag as a result of the CM wake appeared to be independent of the model configuration. Also, the results showed the importance of conducting freestream tests with no bluff body upstream of the test model for comparison to the “in wake” condition to account for possible blockage effects caused by the CM wake. Additionally, the wind tunnel testing suggests the actual drag reduction on the drogue chutes is much less than the 40% initially predicted by NASA CFD simulations. The results from this effort will be used by JSC engineers to help determine the proper size of the drogue parachutes in order to achieve the required deceleration for safe main parachute deployment.