Publication

Abstract : The term interstage refers to a primary structure housed between two stages of a launch vehicle. It is configured to withstand the varying magnitudes of loads during the flight. In this study, an interstage cylindrical shell structure of a Launch Vehicle is designed with isogrid and orthogrid configurations, which are integral-rib-stiffened-skin configurations to have mass-optimised aerospace structures. Design based on closed form solutions, parametric optimisation and numerical analyses to validate the design are carried out for both the configurations and results are compared. Static - linear, static - nonlinear, linear eigen value buckling analysis and non-linear static riks analysis are the different kinds of numerical analyses carried out for estimating the load carrying capacity of the structural configuration under study. The objectives of this work include understanding different aerospace structural configurations, studying grided structures in depth, and using these two to model Orthogrid structures mathematically and design a typical launch vehicle interstage structure using this Orthogrid configuration. Abaqus, a general-purpose Finite Element software is used for the numerical validation. Study compares the results of both the configurations and concludes that orthogrid configuration can be designed with lesser mass for the interstage configuration, loads and kinematic conditions considered for the design problem. The least mass configurations corresponding to each configuration are obtained through parametric design iterations. Various numerical calculations are used to validate these results. The study's findings show that for the geometry, loads, and boundary conditions taken into account, orthogrid design provided superior mass optimisation than isogrid configuration.