High-fidelity Stability Analysis for Parafoil Descent on Titan

Abstract

This study explores the dynamics of parafoil systems under Titan's unique atmospheric conditions using a dual-framework approach. A 6-degree-of-freedom (6DOF) parafoil-capsule model served as a foundation for verification, enabling the development and analysis of a more detailed 9-degree-of-freedom (9DOF) model. The 6DOF model simplifies the system as a single rigid body, while the 9DOF model captures flexible coupling effects between the parafoil and capsule, modeled as two rigid bodies connected by a spring-damper hinge.

Thorough verification techniques, including energy conservation, angular momentum tests, and sensitivity analyses, validated both linear and nonlinear simulations. A novel quasi-linear eigenvalue analysis provided insights into rotational stability, identifying natural frequencies and damping ratios, while exposing the limitations of linearisation in capturing nonlinear dynamic coupling effects. Sensitivity analyses revealed key dependencies on aerodynamic, structural, and mass parameters. Wind studies evaluated stability under steady and gust scenarios, simulating Titan's zonal wind patterns across various angles and altitudes. Results highlight significant differences between 6DOF and 9DOF models, with the parafoil showing moderated oscillations and the capsule exhibiting amplified responses due to dynamic interactions. These findings emphasize the need to model parafoil and capsule dynamics independently for high-fidelity stability analyses.

The study demonstrates the potential of parafoil systems to enhance stability and precision during planetary descent, reducing reliance on propulsion-based corrections. By systematically comparing 6DOF and 9DOF models, the research underscores the importance of flexible coupling dynamics and detailed environmental modelling for designing robust guidance and control systems for planetary exploration.