An Investigation On The Tangentialthrust Orbit Interception And Orbit Rendezvous Problem

Tangential thrust indicates that the thrust direction is in the tangential direction of the trajectory, i.e., is aligned with the current velocity vector of spacecraft. From the expression of orbital mechanical energy, tangential thrust is the most efficient direction strategy since it changes the mechanical energy of the orbit(and also the orbital semimajor axis) at the maximum rate. Tangential thrust has many merits, e.g., simpler thrust direction, less energy consumption and significant improvement in transfer-trajectory safety. According to the magnitude of the thrust, tangential thrust can be divided into two categories: impulse tangential thrust and continuous tangential thrust. Classical Hohmann transfer is a two-impulse cotangent transfer between coplanar circular orbits, and it is the minimum-energy transfer among all the two-impulse orbital transfers. For elliptical orbits, this dissertation studies the impulse and continuous tangential-thrust orbit interception and rendezvous problems. The main contributions are as follows:The tangent-impulse coplanar orbit rendezvous problem is solved based on the linear relative motion for J2-perturbed elliptic orbits. Recent most studies about tangent orbit are based on the two-body absolute orbit dynamic model. This causes large terminal position error under the earth’s oblateness. In this problem there are three cases:(1) only the first impulse is tangent;(2) only the second impulse is tangent;(3) both impulses are tangent. For a given initial impulse point, analytical expression for relative velocity is obtained by using state transform matrix(STM) of the linear relative motion, and then the first two problems can be transformed into finding all roots of a single variable function about the transfer time, which can be done by the secant method. The cotangent rendezvous problem requires the same solution for the first two problems. By considering the initial coasting time, the cotangent rendezvous solution, which requires the same solution for the first two problems, is obtained; in addition, the minimum-fuel solution for the first two problems is also obtained. This method is valid for both twobody and J2 perturbed relative motion models.The singe-impulse minimum-time interception problem with an upper-bounded tangent impulse for a non-maneuvering coplanar target is studied. This problem requires the same flight time for both interceptor and target spacecraft and a transfer orbit tangent to the initial orbit. The true-anomaly range of the target orbit is derived for an upper bound on the magnitude of the tangent impulse. For hyperbolic target orbit, there are four non-continuous points whose velocity vectors are parallel to either of the lines of asymptotes. For a given impulse point, the transfer time for any conic orbit is a function only of the true anomaly of the target orbit. Then, all feasible solutions are obtained by the secant method in the range of solution existence. For different impulse points, the transfer trajectories can be elliptic, parabolic and hyperbolic. Finally, the global minimum-time solution with initial coasting time is obtained by numerical optimization algorithms. The proposed method is valid for all feasible solutions with given impulse point and for the global minimum-time solution with free impulse point.For continuous tangential low thrust coplanar circular orbital transfer and rendezvous problems, the shape-based approximation method with modified inverse polynomials(IP) is studies by considering the thrust-acceleration-magnitude and radius constraints. The shape-based original inverse-polynomial approximation is an analytical method, but the thrust magnitude and radius constraints are not considered such that it may not be used in engineering application. For the time-free transfer between circular orbits, the radius monotonously changes, and the minimum revolution number is analytically derived for a given maximum thrust acceleration. For the time-fixed rendezvous between circular orbits, the seventh parameter is obtained considering the radius constraints, and then the feasible shape-based trajectories for a given maximum thrust are obtained. The maximum thrust acceleration by the modified IP method is less than that of the original IP method for both the transfer and rendezvous problems, even though their energy consumptions are close.