Manufacturing and Testing of a Purged Thermal Insulation Concept for Reusable CFRP Cryotanks

Abstract

The German Aerospace Center experimentally investigates the concept of a purged insulation system for reusable launch vehicles. The concept consists of a carbon composite corrugated core sandwich structure, a cryogenic insulation, a thermal protection system including attachment elements and a purge system. The purge system aims to minimize overall insulation layer thickness by transporting thermal energy into the system. Moisture accumulation and icing within the high-temperature insulation shall be hereby prevented when the tank is filled with cryogenic propellants during launch preparations, conforming to thermal design criteria. The purge system is integrated into the composite sandwich structure to keep the number of additional components low, hence reducing system complexity and overall mass. The full insulation and purging concept is realized as integrated test object and is cyclically tested in the thermomechanical test facility THERMEX. The cycles cover the thermal conditions of both the cold pre-launch tank filling case with active purge flow and the hot conditions of a booster reentry. Additionally, the test object is subjected to axial mechanical pressure loads. The present work describes the manufacturing and the sensor arrangement of the integrated test object and summarizes the testing procedure including preliminary test results.