Flight dynamics numerical computation of a sounding rocket including elastic deformation model

The atmospheric fight of an aerospace vehicle is, in general, subjected to high level of loads (propulsive, aerodynamics, etc.) acting over the vehicle structure which can deform it and, consequently, changes its dynamics during the flight. Depending on the geometry complexity, this deformation, which is associated to the structural elastic behavior, can be modeled by analytic or finite element methods (FEM). In the general case of rockets, which can be considered as a slender body, it is common to find in the literature modeling that assumes the vehicle as a free-free beam, following Euler-Bernoulli or Timoshenko approaches. Therefore, the aim of this paper is to present the development of a three degree-of-freedom (3-DOF) dynamic model of a sounding rocket that includes the elastic deformation parameters in the dfferential equations of motion solved during the trajectory computation. To accomplish this objective, the model assumes the vehicle as a mass-varying Euler-Bernoulli free-free beam whose modal parameters are solved by FEM code and, in the sequence, included in the set of differential equations written in a properly way. The verification of the results for elastic deformation obtained using this approach is made by comparison with results obtained from solving the static aeroelastic problem using an work ow CFD (computational fuid dynamics)/CSD (computational structural dynamics). The verification of the flight dynamic results consistency is performed by comparison with results obtained using a code for ROcket SImulation (ROSI). The preliminary analyzes have shown a good consistency between results, which indicates a reliable and stable solution when using the methodology developed in this paper.