Influence Of Partial Parachute Retracting On Parachute Trajectory And Airdrop Test

Parachute is a deployable aerodynamic deceleration device,which has the advantages of light weight,high deceleration efficiency,simple structure and reliable operation.Parachute has been widely used in the field of aerospace.For a long time,the application of parachute is mainly to achieve pneumatic deceleration through the parachute,while the control of drop point mainly relys on the realization of the drop points control.The parachute will be interfered by the airflow and its own characteristics during the descent process,the parachute landing point is more random,resulting in a large spread of parachute landing points.In order to improve this situation,taking active control measures to adjust parachute descent trajectory can effectively narrow dispersion scope of landing points.This paper puts forward a method to control parachute descent trajectory which relys on the partial parachute rope retraction.Starting from the analysis of parachute controllability mechanism,it sets up a six-degree-of-freedom parachute model with partial parachute rope retraction,carry out the airdrop tests to verify the model.The controllable mechanism analysis of parachute was carried out by CFD(Computational Fluid Dynamics)technology.In the study,it adopts CFD to simulate the different attitude drop process of parachute,and reveals the change of aerodynamic force after the length of partial parachute rope is changed.Then this paper carries out the force analysis to the partial parachute rope retractable parachute,proves the feasibility that the parachute descent trajectory can control.Based on the aerodynamic data calculated by CFD,the paper sets up the six-degree-of-freedom dynamic model of the parachute system under rigid body assumption.The influence of added mass on the parachute dynamics is considered in the model.For the added mass items in the model,it adopts the engineering empirical formula to obtain them.After the model is established,Matlab software is used to complete the dynamic simulation of the model.For the sake of proving the practicability of the parachute control by retracting partial parachute rope and the validity of the above kinetic equations,it carried out a large number of parachute airdrop test,the specific include: verification of parachute free descent test,verification of partial parachute rope retraction and descent test and so on.The paper gives the concrete design and system composition of the airdrop test.The results of the airdrop test show that: The parachute descent trajectory can be changed by changing the length of the partial parachute rope during the descending of the parachute,thus controlling the landing point.Through the comparison between the descent process and the numerical simulation results,the two show good regularity uniformity,which indicates the validity of the dynamic model established in this paper.