Abstract:

This paper is a tutorial on the calculation of mass properties (moment of inertia, center of gravity, product of inertia). There are numerous text books on dynamics which devote a few pages to the theory of these properties. However, these text books quickly jump from a very brief description of these quantities to some general mathematical formulas without giving adequate examples or explaining in enough detail how to use these formulas. The purpose of this paper is to provide a detailed procedure for the calculation of mass properties for an engineer who is inexperienced in these calculations. Hopefully this paper will also provide a convenient reference for those who are already familiar with this subject.

This paper contains a number of specific examples with emphasis on units of measurement. The examples used are rockets and re-entry vehicles. The paper then describes the techniques for combining the mass properties of sub-assemblies to yield the composite mass properties of the total vehicle. Errors due to misalignment of the stages of a rocket are evaluated numerically. Methods for calculating mass property corrections are also explained.