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中文核心期刊

重复使用火箭着陆结构稳定性分析

STABILITY ANALYSIS OF REUSABLE LAUNCH VEHICLE LANDING STRUCTURE

  • 摘要: 近年来,包括中国在内的诸多国家相继开展垂直起降重复使用火箭的研究,运载火箭在平台上垂直着陆时的着陆稳定性为实现运载火箭重复使用的关键问题. 由于在运载火箭设计初期结构设计尚未完成,不具有供着陆稳定性分析的详细的动力学模型,难以开展着陆过程动力学仿真,故对运载火箭着陆稳定性评估方法的研究尤为必要. 本文基于广义碰撞定律,对二维运动模式下运载火箭与着陆平台的多点碰撞过程进行了分析,切向采用库伦摩擦模型给出了切向运动学恢复系数的表达式. 本文首先通过机械能约束和接触碰撞中的单边约束给出了一般运动形式下广义运动学恢复系数的值域,再对两种典型运动模式,给出了该两种典型运动模式下广义运动学恢复系数的值域. 然后考虑着陆腿中缓冲器的作用,将运载火箭与平台的碰撞近似为完全非弹性碰撞,得到了其广义运动学恢复系数,并结合运动学分析和能量法提出了一种基于碰撞后速度的着陆稳定性的判别方法. 最后以某型运载火箭着陆样机的参数为例,分析了碰撞前速度、着陆腿跨距、摩擦系数对着陆稳定性的影响,结果表明,本文提出的稳定性判别方法较能量法更为精确,可以考虑触地速度、角速度、摩擦系数等参数间的耦合关系.

     

    Abstract: Many countries carried out the research on vertical take-off and vertical landing reusable launch vehicle (RLV) in recent years. The touchdown stability of the RLV when landing vertically on the platform is a key issue for the RLV reuse. Since the structural scheme of the RLV has not been completed in the initial stage of design, and there are no detailed dynamic models for touchdown stability analysis, it is difficult to carry out the dynamic simulation of landing process, therefore the research on estimation method of landing stability is needed. Based on the generalized impact law, this paper analyzes the multiple impacts between the RLV and the landing platform in a two-dimensional landing mode, and the tangential restitution coefficients is given by Coulomb friction model at the impulse level. Firstly, the admissible domain of restitution coefficients in the general motion mode is given through the energetic constraint and unilateral constraints, and the admissible domain of restitution coefficients in two typical motion modes is given as well. Secondly, considering the role of buffer in the landing leg, the collision between the RLV and the platform is approximated as a completely inelastic collision, and accordingly the kinematic restitution coefficients is obtained. Therefore, combined with the kinematic analysis and energy method, a touchdown stability criterion is proposed, which discriminates whether an RLV will fall or not after impacts the platform. In the end, taking an RLV landing prototype as an example, the effects of some key parameters on touchdown stability are analyzed, including the touchdown velocity, the span of supporting leg and the friction coefficient between supporting leg and platform. The results show that the touchdown stability criterion proposed in this paper, is more accurate than the energy method, and the coupling relationship between touchdown velocity, angular velocity and friction coefficient can be considered.

     

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