Prevention of Flutter Instability in Control Surface of a Test Vehicle Through Parametric Studies

Abstract

This paper mainly deals with the prevention of flutter instability in fin with shroud of a typical Rocket body through parametric studies. Flutter is an aeroelastic instability which occurs when aerodynamic loads cause deformation of the body which in turn initiates an oscillation in the body and further interacts with aerodynamics. The crew escape system is an emergency escape structure designed to swiftly pull the crew module along with the astronauts to a secure distance from the launch vehicle during launch abort. For the control of crew escape system during the ascent phase of trajectory, sweep back fins are used at the bottom of the vehicle. Finite element modelling of the fin was done using MSC/PATRAN software. Flutter analysis is carried out in MSC/NASTRAN using in-built aerodynamics. MSC/NASTRAN uses plate theories such as Doublet Lattice Method for subsonic Mach number, ZONA51 for transonic and low supersonic Mach numbers and Piston theory for high supersonic Mach numbers to generate the aerodynamic force within NASTRAN. MSC/PATRAN is a software developed to provide a systematic approach towards making finite element modeling fast and accurate; MSC/NASTRAN is a general purpose finite element analysis computer program that addresses a wide range of engineering problem and is also capable to focus on particular types of analysis. In this work, initially normal mode analysis was carried out for the modeled fin and flutter analysis was performed. It was observed that flutter instability occurred in most of the Mach numbers. In order to prevent flutter, the method of mass redistribution is adopted. Mass addition is carried out on leading edge and trailing edge to see the effect of movement of C.G with respect to the shaft axis. By carrying out various mass redistribution studies, the flutter instability in the fin is alleviated. This effort will be helpful for flutter prevention in control surfaces of upcoming vehicles also.