Dynamic Ascent Loads Estimation of Winged Reusable Launch Vehicle: Formulation, Analysis and Post Flight Studies 2024-26-0452

A structural load estimating methodology was developed for the RLV-TD HEX-01 mission, the maiden winged body technology demonstrator vehicle of ISRO. The technique characterizes atmospheric regime of flight from vehicle loads perspective and ensures adequate structural margin considering atmospheric variations and system level perturbations. Primarily the method evaluates time history of station loads considering effects of vehicle dynamics and structural flexibility. Station loads in the primary structure are determined by superposition of quasi-static aerodynamic loads, dynamic inertia loads, control surface loads and propulsion system loads based on actual physics of the system. Spatial aerodynamic distributions at various Mach numbers along the trajectory have been used in the study. Argumentation in aerodynamic loads due to vehicle flexibility is assessed through the use of spatial aerodynamic distributions. Loads are estimated along vehicle trajectory using augmented vehicle states calculated by a flexible vehicle response solver integrated to 6-DOF trajectory solver. The technique enables quantification of augmentation in station loads due to structural flexibility prior to actual launch. Features to estimate augmentation in loads due to wind variability and atmospheric turbulence are incorporated into the load estimation methodology. This methodology was used to authorize the successful maiden launch of RLV-TD HEX-0l flight. The paper describes basic formulation of elastic load estimation technique and pertinent mission design simulation results. Subsequent to the successful flight demonstration studies on the assessment of in-flight measured loads with post flight simulations is also discussed. Close agreement between computed structural load and flight measured loads demonstrate technological maturity of the employed mathematical models and formulation.