Aerodynamics of Launch Vehicles

Abstract

Aerodynamics plays a vital role in STS design process. The steady and unsteady aerodynamic loads generated due to the relative motion between vehicle body and surrounding air during the atmospheric flight phase of the vehicle, its aerodynamic characteristics, external environment and flow characteristics are the major inputs for the vehicle systems design. The aerodynamic axial force is used for the mission design and vehicle performance evaluation. The steady aerodynamic disturbance moments and loads acting on the vehicle are required for vehicle control and structural systems design. Further the aerodynamics-related issues become complex since the maximum dynamic pressure, maximum aerodynamic force and moment coefficients, unsteady loads, maximum wind velocity, large wind shear and measured uncertainties of wind occur almost simultaneously. The vehicle sizing with clustered propulsion systems complicates the aerodynamic flows with unfavourable additional aerodynamic loads. The unsteady pressure fluctuations are due to shock oscillations during the transonic regime and local aeroacoustic loads due to flow separation because of protrusions form a major input for the qualification of structural and other sensitive systems. This chapter presents the aerodynamic characteristics of a launch vehicle during various phases of its atmospheric flight, different types of aerodynamic loads acting on the overall vehicle/its subsystems and their importance for the launch vehicle systems design. Methods of estimating these loads under different conditions are also outlined. Subsequently, aerodynamic force and moment on overall vehicle, its impact on the vehicle systems design and the methods of aerodynamic characterization using the computational fluid dynamics and wind tunnel studies are briefly covered. The salient features of aerodynamic configuration design of a launch vehicle are also included.