Coupled Loads Analysis of a Single Stage Launch Vehicle for Vibration test Level Generation

Gaganyaan is an important mission for the Indian space program to put humans into space. The success of the mission depends on the development of required technology and systems. A test vehicle is developed for the technological demonstration for all envisioned abort flight scenarios of Gaganyaan mission. This is new configuration of launch vehicle with single liquid stage and a number of flights are planned. Coupled Loads analysis of launch vehicle system is a standard practice to estimate response and loads for design of structures and generating sine vibration test levels. Usually a vehicle rests on the launch pad through base shroud with horizontal support and no vertical restraint. Upon ignition of the engine, thrust builds up and upon overcoming gravity the vehicle takes off. In the current analysis the launch vehicle is held in position using a holding / retracting mechanism and at a predefined time the vehicle is released. The boundary condition required a novel method to perform response analysis. The responses estimated from pre-flight analysis is correlated with flight response and a good correlation is observed. Additionally response analysis is performed at engine shut-off. Since being the first flight, no flight data was available of engine thrust. In the current work, using data from earlier flights response was estimated. The analysis also helped in generating levels for vibration test of various sub-assemblies and crew module.