The HZETRN code requires inclusive cross sections as input. One of the methods used to calculate these cross sections requires knowledge of all exclusive processes contributing to the inclusive reaction. Conservation laws are used to determine all possible exclusive reactions involving strong interactions between pions and nucleons. Inclusive particle masses are subsequently determined and are needed in cross-section calculations for inclusive pion production.Norbury, John W. and Blattnig, Steve R. and Tripathi, R. K.Langley Research CenterPARTICLE INTERACTIONS; PIONS; NUCLEONS; STRONG INTERACTIONS (FIELD THEORY); CROSS SECTIONS; CONSERVATION LAWS; PARTICLE MASS; PARTICLE PRODUCTION; COMPUTER PROGRAMS; EXTRATERRESTRIAL RADIATION...