A SENSITIVITY INVESTIGATION ON THE AEROELASTIC DYNAMIC STABILITY OF SLENDER SPINNING SOUNDING ROCKETS Roberto Gil Annes da Silva 1 , J. Guido Damilano 2 and João Luiz F. Azevedo 3 Instituto de Aeronáutica e Espaço, Comando Geral de Tecnologia Aeroespacial Praça Mal. Eduardo Gomes, 50 – São José dos Campos – 12228-903 - Brazil rasilva@iae.cta.br 1 , damilano@iae.cta.br 2 , azevedo@iae.cta.br 3 ABSTRACT The present work addresses a sensitivity analysis investigation of the aeroelastic stability margins for the VSB-30 sounding rocket during the atmospheric flight phase. Parametric stability analyses are performed considering variations of the inertia properties of the modular payload. Such variations can be caused by different type and/or number of experiments (payload modules). The aerodynamic model is based on a supersonic unsteady potential aerodynamics method. The freestream conditions depend on the flight speed and atmosphere. An equivalent structural dynamic model of the rocket is represented by a beam-like structure. The objective of this investigation is to establish an aeroelastic model for aeroelastic stability and response analyses, as well as a procedure for the identification of stability margins for rockets. The resulting aeroelastic model should be further used in MDO processes for the improvement of the vehicle flight performance. The results of the present effort indicate that the flutter behavior of the VSB-30 sounding rocket is sufficiently robust inside the operational envelope, even considering the environmental and loading conditions. The spinning effect, in this case, does not play a significant role, because the flutter margins remain almost unaltered with and without VSB-30 body spin. 1. INTRODUCTION European research on micro–gravity required a new sounding rocket with a performance similar to the one delivered by the English rocket Skylark–7, whose production had been discontinued. Instituto de Aeronáutica e Espaço (IAE), in Brazil, took on the task of the rocket development and complete integration, in a joint effort with the Deutsches Zentrum für Luft- und Raumfahrt (DLR), responsible for the payload of micro–gravity experiments. Several modifications were performed on the previously developed VS-30 sounding rocket, in order to satisfy the required specifications for new scientific and technological experiments in micro-gravity environment. The resulting modified vehicle, named VSB-30, is a two-stage spinning-stabilized slender sounding rocket, with two sets of three fins on each stage, whose engines use a solid propellant [1]. The VSB-30 rocket flight operation is divided into two phases: the first stage flight (FSF) and the second stage flight (SSF). The engines accelerate the vehicle to a ballistic flight path towards the desired micro-gravity condition. A more recent application of the baseline VSB- 30 sounding rocket configuration is in-flight experiments on the aerodynamic behavior and thermal problems of an unconventional asymmetric shape for reentry vehicles comprising multi-faceted surfaces with sharp edges (SHEFEX) [2]. The aim of the experiment was the correlation of numerical analysis results with actual flight data regarding the aerodynamic effects and structural concept for the thermal protection system. Hence, the development of