Dynamic analysis of falling rocket fairing considering rigid-body motion and flexibility

When descending from a high altitude, a rocket fairing is subjected to complex fluid–structure interaction (FSI) effects. This process can structurally damage the fairing or even lead to its disintegration, preventing its reuse and posing a threat to the safety of ground personnel and property. To study this novel FSI phenomenon, an FSI framework was developed that accounts for the rigid-body motion and elastic deformation of the fairing, capturing its dynamic responses during the falling process. The framework's effectiveness and accuracy were verified using a flying wing and a semi-cylindrical shell, respectively. First, a conventional aerodynamic analysis of the fairing was conducted without considering the rigid body displacement. Then, the fairing's falling process was calculated considering its elasticity and rigid motion, finding that the fluid–structure coupling effects cause the fairing's first-order asymmetric torsional mode to diverge. Subsequently, to address the issue of structural damage, two methods for strengthening the structural stiffness and adjusting the center of gravity were proposed. The X-shape reinforcement was found to more effectively inhibit deformation, while the forward shift of the center of gravity effectively mitigated structural failure. Finally, by combining these two fairing modification methods, using 78 kg of X-type reinforced structure and shifting the center of gravity forward by 0.3 m, the problem of fairing disintegration damage during the falling process can be avoided.