Different from the other design parameters in general drogues, there are few studies about the parameter of Length-Width Ratio (LWR). Therefore, the fluid structure coupling model based on the Finite Element Method was used to study the deceleration characteristics and terminal trajectory stability of parachute system in this work. And the graphic transformation technology commonly used in Computer Graphics was used to realize the following of flow field with the trajectory movement. In this work, the cruciform parachutes with different LWR were taken as the research objects, and the above method was used to obtain the trajectory curves, deceleration characteristic curves, and stability curves of the cruciform parachutes under different external conditions. It was found that the deceleration performance was negatively correlated with the LWR when the other design parameters and working conditions remained unchanged, and the trajectory stability and the stability of the parachute were positively correlated with the LWR. Subsequently, the cruciform parachute with the LWR of 4.5 was used for airdropping test, and the accuracy of numerical method used in this work was verified. Then the deceleration processes of cruciform parachute (LWR: 4.5) under different dropping conditions were calculated. It could be found that the external launching conditions had a limited impact on the deceleration performance. The LWR was another design parameter that had a greater impact on the deceleration performance after the parameter of canopy area. Finally, the drag coefficient correction equation representing the deceleration performance was proposed for the first time.

Parachutes are used for aerial projectile deceleration and trajectory control in the military field. Although the existing multi-degree-of-freedom and multi-body dynamics model has a small amount of calculation, the external wind field in this model is simplified, and the influence laws of which on the terminal trajectory are not clear. Therefore, a projectile-parachute system is regarded as the research object in this work. A Fluid-Structure Interaction (FSI) model was used to analyse this system’s terminal trajectory. The cases with different wind velocity, wind directions, and initial trajectory angles were calculated. As a result, the external wind field has a great influence on the terminal trajectory of this projectile-parachute system. The difference in impact points in cases is positively correlated with the external wind velocity. At the same wind velocity, the trajectory in the upwind condition is easier to change than that in the downwind condition, and the difference in impact points is negatively correlated with the initial trajectory angle. While the external wind field has little influence on the projectile-parachute system’s deceleration, the swing angle, and the trajectory angle of the canopy. This system’s deceleration effect in the initial dropping process is more obvious under the upwind condition, and the deceleration effect will tend to be the same with the trajectory angle close to 90 degrees. Therefore, the influence of the external wind field on the terminal trajectory can be effectively reduced by increasing the initial trajectory angle, and the changes in canopy swing angle and trajectory angle will tend to be more stable in this situation