Effects of Rotational Motion on the Ballistic Coefficient of Space Debris

Abstract

Accurate predication of the future states of operational spacecraft and space debris are necessary for conjunctional analysis. Prediction of the states of debris for a few orbital periods is possible with improved models of the upper atmosphere if the objects have spherical geometries. However, spacecraft and other objects with complex geometries that tumble throughout their orbit present a difficult problem because the rotational motion affects their orbital motion and vice versa. In this thesis, the coupled translational and rotational motions of objects, specifically space debris, are studied using a digital simulation based on a six-degree-of-freedom, rigid body model. In particular, focus is on variations due to rotation of an object's ballistic coefficient, which is the product of a coefficient of drag and a reference area divided by the object's mass. If the density is well modeled, the ballistic coefficient is the principal unknown in the drag force. The results of numerous simulations show a predictable relationship between an object's ballistic coefficient and its nodal regression. The simulation is also used to produce data for an orbit determination process in which the ballistic coefficient is estimated. Results are presented that show continuous estimation of the ballistic coefficient, which is fundamental to accurately predicting future states of debris.