Thermo Structural Integrity of a Closure Assembly for The Base Region of a Re-Entry Module

Abstract

Base heating is an important phenomenon in the design of re-entry capsules. The nature of reverse flow in the base region is largely decided by the conditions prevailing at the end of the fore body. For configuration like the re-entry module, the reverse flow is found to be supersonic near the base. It is therefore necessary to protect the base region as well as the internal components from base heating.

Suitable Thermal Protection System (TPS) of minimum mass that will protect the base thermally is to be designed for the base heating levels during re-entry. Low density ablative is selected as the TPS material.

The base region of the re-entry module consists of a closure assembly made up of structural elements which are thermally protected. The structural elements and TPS have different thermo-physical properties. It is necessary to qualify the closure assembly for re-entry loads. However, qualification of closure assembly is a challenging job as there is no facility in the world which can simulate all the time varying flight parameters simultaneously. Hence to study the integrity of the closure assembly during re-entry, detailed temperature mapping of closure assembly was carried out.

Thermal mapping of the closure assembly was carried out considering both axisymmetric and three-dimensional model using finite element package and the results are compared. Maximum temperatures attained at different locations of the assembly are discussed. Temperature distribution of the closure assembly at critical instants of flight was estimated. Thermo-structural analysis carried out showed the adequacy of the design, which was subsequently demonstrated by a successful re-entry flight.