With complicated dimensional modal characteristics, the propellant sloshing equations of strap-on launch vehicle with long boosters can not be deduced from the traditional simplified one-dimensional beam model. In this paper, the propellant sloshing model of long strap-on launch vehicle is simplified as a dimensional beam system composed of a single-dimensional central beam with several single-dimensional beams around it. On the basis of this beam system, a new propellant sloshing model is deduced, the force of propellant sloshing on the launch vehicle is also given. Finally, the new model is compared with the traditional propellant sloshing model of strap-on launch vehicle with short boosters which used to be simplified as one-dimensional beam model. Different from traditional model which only consider the core stage's mode and axial overload, both core stage and boosters' modes and axial, lateral, normal overloads are involved in the new model, so it is more coincidental with the actual dynamical characteristics and the state of loading. In addition, the formulas of sloshing force on the vehicle and its generalized force are also changed in the new model.%长助推捆绑火箭由于具有复杂空间模态特征,不能基于传统一维梁简化模型来推导其液体晃动方程.将长助推捆绑火箭简化为由芯级一维梁和多根助推一维梁组成的空间梁系模型,在此基础上推导了新的液体晃动方程,给出了晃动对箭体刚体运动和弹性振动的作用力,最后和传统的将捆绑火箭简化为一维梁模型下的液体晃动模型进行了比较.不同于传统液体晃动模型中只考虑芯级模态和轴向过载,新的液体晃动模型同时考虑了芯级和助推的模态以及轴向、横向和法向过载对晃动的影响,更加符合捆绑火箭实际动特性和受力状态.另外,新模型中晃动对箭体的作用力及其广义力计算公式也有所变化.本文的研究对未来新型捆绑火箭姿控系统的研制具有一定理论价值.
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