This dissertation is concerned with finding the values for the nuclear cross sections used in the Boltzmann equation for space radiation transport and dose estimates. An extraordinary number of cross sections are required because of the large number of ion types and their extensive energy range, The Lippmann-Schwinger equation is numerically solved in momentum space for a first order optical potential (free space case) and calculations are made for the total and absorption cross sections for nudeus-nucleus scattering. Absorption cross sections are also calculated using a medium modified firstorder optical potential in the Lippmann-Schwinger equation and are compared with experimental values. Results are presented for the absorption cross sections for 4He-Nucleus and 12C-Nucleus scattering systems and are compared with experimental values below 100 A MeV. The use of the in-medium nucleonnucleon cross sections is found to result in a significant reduction of the free space absorption cross sections, in agreement with experiment. We have also reformulated the Glaubermodel of heavy-ion fragmentation to treat the cluster abrasion of alpha particles from a-cluster nuclei such as 12C, 160 , 20Ne, 24Mg, 28Si, 36Ar, and 40Ca. Comparison of the calculated values is made with recent experimental data and good agreement is found. The energy dependence and the target mass dependence of cluster knockout cross sections for the 160 projectile are discussed. The inclusion of clusters knockouts is shown to significantly modify transport properties of space radiations
