663. Mass Properties by Computerized Building Blocks

Paper

Abstract

A computer program has been developed that affords rapid, accurate mass property data for use by engineering groups in the design evaluation of stability, strength, and vibration characteristics of an aerospace vehicle.
The program determines the mass properties of a vehicle by a method similar to manual calculation. By the manual method, mass properties of a structure are calculated component by component; the component mass properties are then added to determine the mass characteristics of the complete assembly. In this paper, the geometric shapes, or ‘building blocks, ‘ and associated equations have been programmed for computer calculation. The weight engineer can select shapes of various orientations, add them together to make an assembly, and add the assemblies to obtain the mass properties of a total vehicle.
The final output of the program includes data that completely define the mass characteristics of a vehicle. These data are weight, center of gravity, moments of inertia, products of inertia, location of principal axes, radius of gyration, and moment of inertia and product of inertia about the principal axes.
This paper describes a sample computer run with instructions and gives the basic equations formulating the computer program. The program allows the weight engineer to perform other important work while the computer laboratory keypunches and runs the program. Design changescan be made quickly, and mass property data can be keptcurrent with little effort. An average run takes from 40 to 60 sec on an IBM 360 Model 40 computer.
The program was developed for small aerospace vehicles; however, it has been used for a large space station, a large space antenna ,and an airship envelope. The program can be expanded by adding geometric shapes and associated equations a sneeded.