Evaluating Spacecraft Radiation Shielding Using a Microcomputer-Based CAD Program

This paper describes a new microcomputer-based program that evaluates the radiation shielding of spacecraft or Space Station modules. This program runs on a computer-aided design (CAD) system that constructs and manipulates models of spacecraft. It uses the graphical and geometrical functions of the CAD system to analyse the radiation shielding provided by spacecraft models. The program has the following new features:

• It uses solid angles of equal size that are distributed uniformly over a sphere surrounding the point of interest;
• It computes the geometrical intersection of each solid angle with a specified layer of a spacecraft model;
• It computes the volume, centroid and average thickness of each intersection, along with the variance of its volume and the standard error of its centroid position;
• It writes computer files of both the solid model and its volume, centroid and average thickness for each intersection for a given dose point and shielding layer.

When combined with composition and density data, the results provide input to existing radiation analysis programs. The total radiation shielding in a spacecraft or Space Station model corresponds to a superposition of shielding for all of the layers comprising a model. The archived intersections help in detailed analyses of shielding distributions. The new program obtains average shielding thicknesses in each solid angle element. These average thicknesses represent shielding more accurately than shielding computations that use single rays to determine the thickness for each solid angle element. The program runs on microcomputer and CAD workstations, providing flexible and cost-effective evaluations of radiation shielding distributions.