Design And Analysis of Intertank Structure For Cryogenic Stage

Abstract

In cryogenic stages of ISRO, Liquid Hydrogen (LH₂) is used as fuel and Liquid Oxygen (LOX) is used as the oxidiser. Both are stored in propellant tanks at cryogenic temperature. These propellants tanks are arranged in tandem with the intertank structure in the middle which at ambient temperature. Tanks being at cryo temperature contract radially imparting large thermal stresses on intetank. Hence the design of intertank structure requires special attention to nullify this thermal stresses. Currently, intertank structures are made of truss rods which allow radial contraction through spherical joints at both ends. However this configuration introduces large concentrated loads at truss interfaces resulting at higher structural mass. A more plausible approach is to design a stiffened cylindrical structure with provision for radial sliding to minimize thermal stresses. The joint is inserted radially from the outer diameter of the two interfacing flanges. On the application of temperature gradient, it allows free radial movement and prevents stress built up on the account of temperature. This paper envisages the configuration, design and analysis of an intertank structure with cylindrical shell construction with provision for neutralizing thermal stresses which is planned to be introduced in future cryogenic stages of ISRO