Speaker
Description
In 2008, France adopted the French Space Operation Act (LOS), which regulates the space activities of French operators. Among many topics covered, the LOS act also addresses the reentry of spacecraft and their debris, by imposing a maximum acceptable probability of a fragment to survive and pose a risk to populations.
As the number of satellites in orbit continues to grow, the importance of accurately predicting debris behavior is also increasing. Thanks to all the extensive work performed by the scientific community, significant progress has been made in recent years in predicting the survivability of space debris during reentry. However, prediction of some aerothermodynamical phenomena remains challenging.
One of these phenomena is the aerodynamic stability, which has a high impact on the behavior of debris during their reentry and especially on their attitude. This, in turn, directly influences the heat flux distribution and ablation. Debris rotating at high rates has a different heat flux distribution compared to a fully stabilized body, which receives most of the heat on the side exposed to the freestream.
The aerodynamic stability is mainly characterized by pitching, yaw and roll moment coefficients and by corresponding moment damping coefficients. While the moment coefficients are well predicted with modern theories for capsules and other vehicles, some geometries like cylinders or rings show a noticeable disagreement when using simple models like modified Newton one. Moreover, the prediction of moment damping coefficients presents a significant challenge, due to the lack of related data and due to the dynamic aspect of damping.
The aim of this presentation is to share a methodology for analyzing the stability of reentering bodies and to highlight the limitations of Newtonian theories in predicting aerodynamic stability by comparing analytical solutions, CFD and available wind-tunnel data. The method was verified using a space capsule, and then the methodology was applied to a cylinder and a ring to analyze their stability. Finally, different functions of pressure distribution were tested to determine whether the prediction of moment and damping coefficients could be improved when using analytical models.