optimal transfer of spacecraft with nuclear thermal propulsion to the earth sphere of influence

Paper number

IAC-08.E2.1.2

Author

Mr. Oleksandr Dekhtiar, National Taras Shevchenko University of Kyiv, Ukraine

Year

2008

Abstract

In modern space flight mechanics calculation and optimization of high thrust propulsion spacecrafts (SC) maneuvers as a rule are executed by the impulse (burn) approximation of active arcs of trajectory. However, this method does not allow to optimize the spacecraft thrust control and to perform optimization of parameters of an active arc of trajectory, because the method is based on assumption of unlimited thrust. That is why it is important to optimize SC movements by methods adjusted for limited thrust propulsion with relatively small maximum reactive acceleration, especially for nuclear thermal propulsion (NTP).
The main goals of this research are development and actual usage of an alternative way to optimize active arcs of interplanetary trajectories that are calculated according to the modified method of sphere of influence adjusted for NTP thrust limitation. This research targets following tasks: a) optimization of maneuver of SC insertion to the Earth's sphere of influence by means of optimizing NTP thrust control, an active arc extension and a transition hyperbolic orbit's pericenter radius adjusted for NTP specificity on a stage of setting up and integration of a differential equation system of motion, b) comparing the results of application of obtained thrust control with the results of application of the impulse (burn) approximation approach and c) determining problem parameter ranges, for which usage of both methods of optimization is correct.
Task of trajectory optimization of SC insertion to the sphere of influence is presented as a problem of SC transferring from a given initial circular orbit to a hyperbolic orbit specified by hyperbolic excess velocity. Gravitational influence at an active stage is calculated by means of the central uniform gravity field model. The problem is formulated as the Mayer's variational problem for which edge point angle coordinates of an active arc beginning and end, transition hyperbolic orbit's pericenter radius and thrust vector direction's program of control are subject to optimization. Analysis of optimal control has been carried out based on the Pontrjagin’s maximum principle and brought to task of finite-dimensional optimization that has been numerically resolved.
The given research results in a new approach for optimal trajectories designing of SC with NTP transferring to the Earth's sphere of influence, definition of the problem parameter ranges where an approach is correct, comparative analysis of the suggested approach and the traditional burn approach.

Abstract document

IAC-08.E2.1.2.pdf

Manuscript document

IAC-08.E2.1.2.pdf (🔒 authorized access only).

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