Multistage Liquid Rocket Weight Estimation and Optimization for Early Design Stages

Abstract

An improved method was proposed to estimate the structural ratios of a multistage liquid rocket for the early design stages, for example, the preliminary sizing analysis, or mission design level. The method computes the optimal vehicle weight required for implementing missions using estimated structural ratios without any further detailed structural analysis at the corresponding design stage. An iterative process was established, consisting of weight estimation, mission velocity, and staging analysis modules. The process employs the ratio of engine mass to structural mass and an empirical formula that describes the relationship between engine mass and thrust to estimate the structural weight. The method was verified by comparing the estimated results with known rocket data of interest. Another comparison was made between the proposed method and the conventional method by implementing Monte Carlo simulations. Gradient-based optimization was implemented based on the established process to compare the results with KLSV-II as well. It was demonstrated that the proposed method has the capability to successfully estimate the structural ratios with high accuracy, and hence, the optimal weight of the respective rocket stages can be simply obtained with reduced computational efforts at the early design stages.