Achieving load relief with minimal change in conventional control law of a launch vehicle

This article is about managing the structural load due to winds on a launch vehicle during its atmospheric flight. Wind generates aerodynamic force on the vehicle. The other sources of force on the vehicle are thrust and weight. These forces generate moment on different structural members of a launch vehicle, depending on their point of application with respect to the location of a particular structural member. Together these forces and moments generate tension, compression, shear and bending loads at different locations on the launch vehicle. If the in-flight loading exceeds the structural limit of any member, the vehicle would break. In this paper we have explored the possibility of achieving load relief without using any additional sensor or scheduling of any additional gain. This methodology is useful if the requirement for achieving load relief comes very near to the launch date. In this scenario, the control designer will not have enough freedom to go for wholesale changes in the already existing onboard software of a prevailing conventional control law. This restriction is due to the necessary time required for verification and validation of modifications in code.