섭동을 고려한 실시간 우주비행체 요격

Abstract

This paper deals with spacecraft interception problem considering perturbation. The Earth is not perfectly spherical, so it has gravity imbalance. Therefore, spacecraft rotating around the earth will under perturbation due to gravity imbalance. The effect of perturbation is included in the equation of motion using 2nd zonal harmonics, J2.

Interceptor require active control to intercept the target in consideration of perturbation. In this paper, active control using a thruster is assumed. Likewise, the thrust equation are included in the spacecraft equation of motion to account for thruster.

In order to intercept the target using xed thrust, the direction of thrust is required. Optimization technique can be used to determine the direction of thrust. In this paper, the lagrange coecients and universal variable are used to construct the optimization problem in order to deal with not only coplanar circular orbit, but also non-coplanar elliptic orbit. The optimization problem is solved by numerical analysis. However the spacecraft intercept problem has strong nonlinear system, so it includes many local solutions. Therefore, it is important to guess the initial value. In this paper, a genetic algorithm is used to guess the initial value.

The optimization problem nds the optimal solution based on impulse. This mean that there is no change in position during the orbit transfer of the interceptor. Therefore, if this optimal solution is used for the equation of montion including perturbation and thrust, the interceptor can not intercept the target at the nal position.

In order to solve the position error in the nal position, this paper proposes real-time guidance. the optimal solution as the propulsion direction will be used, but calculate the optimal solution at every moment and continue to change the propulsion direction. In this paper, the simulation is carried out considering various situations in order to verify this method.