Abstract: Aiming at heatshield separation for Tianwen 1 lander, the separation dynamics are modeled and used to analyze the safety of heatshield separation, followed by the design of the heatshield separation trigger. Based on the heatshield separation dynamics model and the close proximity aerodynamics model, the relative velocity and attitude motion are analyzed. Then the minimum ejection velocity for heatshield separation is determined according to the positive separation requirement of the heatshield. Considering that the lander attitude motion affects the separation safety, angular rate damping with a minimum time limit is applied to the lander before separation. The available Mach number and available time for heatshield separation trigger are analyzed further in terms of the criteria for successful separation, leading to the trigger designed as accumulated velocity with a time constraint. The Monte Carlo simulation of the parachute descent for Tianwen 1 lander is carried out, and the simulation results show that the heatshield separation is safe enough, which is verified by the flight results of Tianwen 1.

Key words: Tianwen 1 lander, Heatshield separation, Safety analysis, Heatshield separation trigger