Analysis of the motion of spinning, thrusting spacecraft
Abstract
The primary objective of this research is to develop analytic solutions of motion for spinning, thrusting spacecraft. Analytic solutions for rigid body motion have a number of useful advantages. Some of these include giving fundamental insight into the dynamic behavior of the spacecraft. In particular, we can use analytic solutions to identify secular terms which drive the solutions as time goes to infinity. Asymptotic expressions can help us to identify limiting behavior of the motion and first order effects. In addition, analytic solutions provide us with a basis for solution algorithms, allowing for straightforward computation and numerical calculation of the ensuing motion. These algorithms are ideal for onboard (autonomous) computations of spacecraft maneuvers. They also facilitate parametric studies which can enhance our understanding of a particular maneuver. Analytic solutions can also lead to the development of simple control laws. For example, during a standard spinning up maneuver, a spacecraft can accrue a transverse velocity bias due to thruster couple mismatch or (as in the case of the Galileo spacecraft) due to the fact that there is only one spin-up thruster. This undesired velocity bias can be annihilated by a simple two-burn maneuver. An open-loop control scheme may be employed which is remarkably simple to implement because it only requires knowledge of the initial spin rate and the angular acceleration to provide the necessary control parameters. Floquet theory provides attitude solutions for large angle motions when a principal-axis torque acts on an asymmetric rigid body. These solutions are accurate for any torque level. For typical spacecraft torque levels, only a few Fourier terms are needed. The solutions obtained may find application in onboard (autonomous) computations of spacecraft maneuvers, where speed, accuracy, and memory place severe constraints on numerical algorithms.
Degree
Ph.D.
Advisors
Longuski, Purdue University.
Subject Area
Aerospace materials|Mechanical engineering|Mechanics
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