The Validity of the Straightahead Approximation in Space-Vehicle Shielding Studies—Part II

The straightahead approximation, i.e., the approximation that the secondary particles from nucleon-nucleus collisions are emitted in the direction of the incident nucleon, is often used in space-vehicle shielding studies. The validity of this approximation has been tested by comparing calculations made with the angular distribution of secondary particles properly taken into account with calculations using the approximation. Comparisons between the calculations are given for both monoenergetic protons and a typical flare spectrum normally incident on slab shields followed by tissue. The results indicate that the approximation is sufficiently accurate to justify its use in obtaining estimates of the secondary-particle contribution to the dose behind thin shields.