天问一号着陆器大底分离触发条件设计方法

针对天问一号着陆器防热大底分离触发条件确定问题，利用数学仿真的方法分析气动特性、防热大底相对着陆器姿态运动等因素对分离安全性的影响，给出可安全分离的触发条件。不同分离触发马赫数的仿真结果表明，较大分离马赫数的碰撞风险较高，但防热大底长期运动趋势由弹道系数决定，相比着陆器下降更快。根据伞降过程着陆器姿态运动及伞绳力特点，建立了一套短期相对姿态运动分析模型，定量分析姿态摆动峰值角速度和分离时刻摆动相位对安全性影响，利用最危险分离相位确定了峰值角速度和分离马赫数与分离过程最近距离的关系，给出安全分离所需的峰值角速度-马赫数范围。利用着陆器姿态摆动峰值角速度随马赫数减小的规律，将峰值角速度约束转化为分离马赫数约束，从而确定了可安全分离的马赫数条件。

A Heatshield Separation Trigger Design Method for Tianwen 1 Lander

In this paper, the heatshield separation trigger for Tianwen 1 lander is determined through analyzing the aerodynamic characteristics and relative rotation effect on separation distance. First the results of the simulation with different separation Mach numbers indicate that the higher separation Mach number has a higher recontact risk, and the heatshield descents faster than the lander due to the ballistic coefficient difference. In order to obtain the quantitative relationship between the separation distance and the motion of the lander at separation time, an analysis model for the heatshield and the lander system is established according to the characteristics of the attitude movement of the lander and the force of the parachute. By using the analysis model, the separation distances at variations of lander swing phase are evaluated to figure out the riskiest separation phase (RSP). The restriction on the peak of lander angle velocity and separation velocity is determined for heatshield separation by the simulation at the RSP. Furthermore, according to the fact that the peak of lander angle velocity decreases with the Mach number, the restriction on peak angle velocity is replaced by the upper limitation of separation velocity which provides a very low recontact risk to heatshield separation.