Doctoral Dissertations

Nathan Harl

Abstract

"This dissertation presents a method for controlling the orbital elements of a spacecraft using continuous low-thrust systems. The method involves the use of a general performance index, which is designed to minimize the difference between the instantaneous orbital elements of a spacecraft and some desired set of orbital elements. Due to the generality of the controller design, the resultant controller can be applied to a wide variety of scenarios about various bodies in space. To minimize the designed performance index, a shooting method and a Sequential Quadratic Programming algorithm are utilized and compared.

The primary application of the general controller design in this study is the problem of generating and maintaining low-altitude, polar, Sun-synchronous orbits about the Moon. Such orbits are useful for lunar mapping missions, such as with NASA's Lunar Reconnaissance Orbiter (LRO) mission which began in June of 2009. While Sun-synchronous orbits are known to exist naturally about Earth, lunar Sun-synchronous orbits do not exist naturally and instead require a set of continuous low-thrust control actions for stationkeeping. In this dissertation, it is shown that Sun-synchronous orbits can be maintained for extended periods of time using low out-of-plane thrust levels. The steering profiles necessary for stationkeeping these orbits are shown to follow simple periodic profiles. From a literature search, this is the first known work which has studied the techniques required for maintaining Sun-synchronous orbits about the Moon.

In order to demonstrate the effectiveness of the general controller design, it is also applied to two additional astronautical problems of interest. In particular, the controller design is applied to the problem of an orbit transfer between two inclined geosynchronous orbits about Earth and the problem of low-thrust asteroid deflection"--Abstract, page iii.

Advisor(s)

Pernicka, Hank

Committee Member(s)

Rovey, Joshua L.
Balakrishnan, S. N.
Landers, Robert G.
Bohner, Martin, 1966-

Department(s)

Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Aerospace Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2010

Pagination

xi, 157 pages

Note about bibliography

Includes bibliographical references (pages 149-156).

Geographic Coverage

Moon

Rights

© 2010 Nathan Robert Harl, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Orbit determinationSpace vehicles -- Control systems -- DesignSpace vehicles -- Propulsion systems

Thesis Number

T 9696

Print OCLC #

749930680

Electronic OCLC #

908693945

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