Low-Speed Flight Dynamic Tests and Analysis of the Orion Crew Module Drogue Parachute System

Abstract

A test of a dynamically scaled model of the NASA Orion Crew Module (CM) with drogue parachutes was conducted in the NASA-Langley 20-Foot Vertical Spin Tunnel. The primary test objective was to assess the ability of the Orion Crew Module drogue parachute system to adequately stabilize the CM and reduce angular rates at low subsonic Mach numbers. Two attachment locations were tested: the current design nominal and an alternate. Experimental results indicated that the alternate attachment location showed a somewhat greater tendency to attenuate initial roll rate and reduce roll rate oscillations than the nominal location. Comparison of the experimental data to a Program To Optimize Simulated Trajectories (POST II) simulation of the experiment yielded results for the nominal attachment point that indicate differences between the low-speed pitch and yaw damping derivatives in the aerodynamic database and the physical model. Comparisons for the alternate attachment location indicate that riser twist plays a significant role in determining roll rate attenuation characteristics. Reevaluating the impact of the alternate attachment points using a simulation modified to account for these results showed significantly reduced roll rate attenuation tendencies when compared to the original simulation. Based on this modified simulation the alternate attachment point does not appear to offer a significant increase in allowable roll rate over the nominal configuration.

Drogue Parachute Effects on the Orion Crew Module Stability

“…Test data were gathered for the heatshield-forward condition, which is the orientation that the vehicle descends through the atmosphere. Strouhal number and angular rates for the forced oscillation testing were chosen based on dynamics observed in model freeflight tests of the CM with drogues 5 . The majority of the wind tunnel test was conducted at a dynamic pressure of 3 psf and a Reynolds number of 310,000 based on the CM diameter.…”

“…A 1/16 th -scale CM was modified from a free-flight model 3,5 to accept 6-component balance hardware. The model was built using an automated polycarbonate fabrication system in the NASA Langley (LaRC) rapid prototyping lab.…”