Rapid trajectory planning of a reusable launch vehicle for airdrop with geographic constraints

Xing Wei,Lei Liu,Yongji Wang,Xuejing Lan

doi:10.1177/1729881418817971

Abstract

Online feasible trajectory generation for an airdrop unpowered reusable launch vehicle is addressed in this article. A rapid trajectory planning algorithm is proposed to satisfy not only the multiple path and terminal constraints but also the complex geographic constraints of waypoints and no-fly zones. Firstly, the lower and upper boundaries of the bank angle that implement all the path constraints are obtained based on the quasi-equilibrium glide condition. To determine the bank angle directly, a weighted interpolation of the boundaries is then developed, which provides an effective approach to simplify the planning process as a one-parameter search problem. Subsequently, three types of lateral planning algorithms are designed to determine the sign of the bank angle according to the requirements of waypoints passage, no-fly-zones avoidance, and terminal constraints in the airdrop process, and the convergence of these methods for passing over the waypoints and meeting the terminal conditions has been clarified and formally demonstrated. Considering the constraints in the actual airdrop flight missions, the planning trajectory is divided into several subphases to facilitate the application of corresponding algorithms. Finally, the performance of the proposed algorithm is assessed through three airdrop missions of reusable launch vehicle with different geographic constraints. Besides, the effectiveness of the algorithm is demonstrated by the Monte Carlo simulation results.

Highlights

In recent decades, owing to the advantages of quick support capability, ultra-long flight range, and high security in global strike and space transportation, the airdrop system of reusable launch vehicles (RLVs) has attracted widespread interest in both military and civilian applications.[1]
For some special flight missions, the RLV is required to precisely overfly some predetermined positions on the ground which are referred as waypoints, such as telemetry stations that can validate the navigation of the vehicle,[10] enemy targets that need to be destroyed, or disaster-hit area where relief materials should be airdropped.[1]
Some special regions on the RLV flight path should be kept away owing to geopolitical restrictions or security threats, such as large cities, fire blockade area, or military bases, which can be regarded as no-fly zones.[11,12]

Summary

Introduction

In recent decades, owing to the advantages of quick support capability, ultra-long flight range, and high security in global strike and space transportation, the airdrop system of reusable launch vehicles (RLVs) has attracted widespread interest in both military and civilian applications.[1]. A new online trajectory planning approach is proposed to rapidly generate a feasible trajectory satisfying the path, terminal, waypoint, and no-fly zone constraints for the airdrop RLV. The objective of the trajectory planning problem is to rapidly design a feasible trajectory from the initial position to the expected target, satisfying multiple flight constraints, including path constraints, terminal constraints, and geographic constraints for the airdrop RLV. It can be formulated as a feasible control problem, in which dynamics model is represented by equation (1), and multiple constraints are given in equations (3) and (11). The nominal angle of attack profile is selected as piecewise linear functions of velocity and is described as follows aðvÞ

TAEM À V 2

T ðiÀ1Þ f ðiÀ1Þ ðiÞ

10 Transtion point 36 40 45 50

Conclusions