Structural Optimization of Waffle Shell Sections in Launch Vehicles

A new approach to optimizing the waffle shell sections of the launch vehicle is proposed. The waffle cantilever cylindrical shells are considered under the action of the axial force that is lower than the critical load. The nonuniformity load coefficient is calculated based on the analysis of the static stress-strain state using the finite element method. Considering the calculation data and analytical relations that are successfully applied in the design of launch vehicles, the optimal parameters are chosen. For this purpose, the structural surface is conventionally divided into the main zones with the nonuniformity coefficients exceeding a certain predetermined value, and the weight reduction zones. Since the main zones are characterized by significant stresses, they are enhanced via the increase in finning and shell thickness. Low stresses are observed within the zone of weight reduction, therefore finning and shell thickness can be reduced, as well as the structure can be lighter. In this case, both the cross-sectional dimensions of finning and shell thickness are subjected to variation. The results of the optimization of the tail section of the Antares launch vehicle are presented. It has been established that the weight of the weight-reduced tail section is 188 kg less than the weight of the original structure, which is 18% of the total weight.