Validation of a Simulation Model for a Planetary Entry Capsule

Subsonic static and oscillatory aerodynamic coefficients were measured at Politecnico di Torino for a planetary entry capsule model. The experimental data set was included in a mathematical model of payload-decelerator system, and the results of simulations were compared with flight-test data. The frequency-domain attitude response of the capsule was reproduced during the main parachutesʹ deployment, and discrepancies for the drogue opening phase were observed. The impact on simulations of atmospheric turbulence and asymmetries in the parachute suspension system was also considered. The results suggest that several factors may affect the fidelity of simulations such as correct modeling of suspension system geometry and flexibility, parachute aerodynamics, accuracy of payload inertial data, and accurate matching of real flight external perturbations. The effect of some design parameters on capsule attitude dynamics was evaluated. The artificial increase of capsule damping coefficients produced observable effects on attitude time histories for large perturbations of the aerodynamic derivatives only. The dynamic stability of the system is reduced for large increase of riser length and parachute added mass.