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Title:Automated planetary satellite tour planning with a novel low-thrust direct transcription method
Author(s):Ellison, Donald
Advisor(s):Conway, Bruce A.
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Genetic Algorithm
Sparse Nonlinear OPTimizer (SNOPT)
Automatic Differentiation
Nonlinear Program
Monotonic Basin Hopping
Mission Analysis Low-Thrust Trajectory Optimization (MALTO)
Abstract:Upon completion of the heliocentric leg of its mission, it is almost always the case that an interplanetary spacecraft has scientific objectives to accomplish. This is especially true if the spacecraft performs a planetary moon tour. Over the past decade, mission designers have started to consider the use of low-thrust electric propulsion systems on board the spacecraft to enable future tours. The optimal trajectory for a given mission profile using low-thrust may be highly non-intuitive. There are thus many challenging aspects to the design of multiple flyby, low-thrust trajectories. One of the most significant, from the point of view of a numerical optimizer, can be the characteristic time scale of the dynamical system. Trajectories in a setting with a short characteristic time scale (e.g. those occurring in the Jovian system) are more challenging to optimize than those with a longer time scale (e.g. heliocentric trajectories to the outer solar system) because the spacecraft must often perform many revolutions about the central body as well as several flyby maneuvers. In this work, a novel way of parametrizing a low-thrust trajectory is explored and results using this method are presented. In addition to this, methods are outlined to increase the speed of execution and robustness of a numerical optimizer employing the Sims-Flanagan transcription method. To illustrate the difficulty of low-thrust trajectory optimization in a dynamical system characterized by a short time scale, and to provide an example of a tool that would benefit from the previously mentioned improvements, an existing medium-fidelity interplanetary trajectory optimizer, the Evolutionary Mission Trajectory Generator (EMTG), is modified and used to revisit the preliminary design phase of the Jupiter Icy Moons Orbiter (JIMO) reference trajectory. The results of this analysis are presented and compared with the high-fidelity version of the JIMO reference trajectory generated using the software package Mystic.
Issue Date:2013-05-24
Rights Information:Copyright 2013 Donald Ellison
Date Available in IDEALS:2013-05-24
Date Deposited:2013-05

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