MODELLING CAPSULE STABILITY ACCOUNTING FOR SHAPE CHANGE

Abstract

Earth return missions or exploration missions use mostly capsule-like shapes, which enter the atmosphere at very high velocities. Some of these missions, like sample return, do not use any parachute or other stabilizing aerodynamic or RCS devices. Therefore, the capsule stability has to be guaranteed solely by the spacecraft configuration from hypersonic conditions down to the subsonic regime at landing. This task is very challenging and requires reliable design tools. However, both experimental and numerical tools still have shortcomings in full simulation or modelling of the flight environment. Therefore, further improvement of these tools by means of complementary application is essential. Most of the exploration missions use an ablative thermal protection system, which experiences shape changes during the hypersonic flight regime. This may lead to a change of the pressure distribution and movement of the center of gravity of the vehicle. Since the vehicle does not have control devices, it can lose its aerodynamic stability and the situation may become critical. The prediction of the Thermal Protection System (TPS) recession over the complete surface with the existing tools is not possible. Therefore, the aerodynamic design should consider it in the margin policy and the flight qualities and risk analysis need to be performed accordingly. The ESA TRP MODSHAPE (Modelling Capsule Stability accounting for Shape Change) addresses the aforementioned challenges and this paper gives an overview of the planned activities and summarizes the main challenges and goals.