Oscillations of the Payload Fairing Body of the Cyclone-4M Launch Vehicle during Separation

Dynamic processes in the payload fairing body of the Cyclone-4M launch vehicle under the influence of impulses from pneumatic pushers during separation are modeled. The complex honeycomb structure of the fairing body during modeling is replaced by a simpler composite structure, which is equivalent in mass and stiffness characteristics. Instead of a regular system of reinforcements in the composite model, anisotropic layers are introduced, the characteristics of which are determined. The number of anisotropic layers corresponds to the number of cylindrical and conical fairing sections. A special method for calculating the anisotropy characteristics of layers in the circumferential and meridional directions by the criterion of equivalent bending stiffness of the initial and modeled structures has been developed. Nonlinear relations with respect to the stiffness characteristics of anisotropic layers, which are defined by the iteration method, are obtained. The discretization of the composite model is carried out by the finite element method, while the time problem was obtained by the Wilson finite-difference method. The peculiarity of the problem is the combination of the rotational motion of the flap as a solid body and the oscillations caused by the deformations. The standard formulation for solving a dynamic problem allows us to calculate correctly the amplitudes of radial oscillations of the flap, which determine the dynamic zone of the fairing, and the stress. The characteristics of the natural oscillations of the flap were previously determined. Calculations have shown that the oscillations of the flap occur mainly with the frequency of the main tone. The calculated data for the maximum amplitudes of radial displacements are compared with the experimental values obtained during ground tests. The agreement of the results is quite satisfactory, especially for the lower flap flange, where displacements are maximum. Dynamic stresses are insignificant and do not exceed 15% of the yield stress. The task was to optimize the shape of the impulse from the pneumatic pushers to reduce the dynamic response of the flap during oscillations. Under the condition of preserving the value of the impulse required to deploy the flap during rotation, the distribution of the impulse in time, in which the maximum dynamic displacements are reduced by 1.5 times, was obtained. The change in the impulse shape can be achieved through a programmable pressure supply in the pneumatic