Pogo Stability Approaches for the Strap-On Launch Vehicle with Staged Combustion Cycle Engines

Abstract

According to the new characteristics of the solid–liquid strap-on launch vehicle and the liquid oxygen/kerosene staged combustion cycle engines, a finite element model of the launch vehicle propulsion–structure coupled system subjected to pogo was presented in this paper. In the model, the structure was represented by a longitudinal–lateral–torsional integrated finite element model with a three-dimensional tank and one-dimensional beam–spring–mass. The propulsion system was represented by a transfer matrix model, which was fitted by the vector fitting method and transformed into a second-order differential equation. By assembling the structure dynamic equations and propulsion system, the governing equation of the coupled system can be established. After that, pogo stability was analyzed by solving the complex eigenvalues of the governing equations. The method developed in this paper can also be expanded to other liquid launch vehicles.