O(3P) is a highly reactive species which may cause damage to materials on contact. In low Earth orbit (LEO), high-energy collisions (similar to4.5 eV) of O(3P) with spacecraft materials can lead to extensive degradation. In this study, we use ab initio molecular orbital calculations to investigate the possibility of chain breaking in polyethylene caused by a single O(3P) attack under LEO conditions, because the occurrence of such reactions could greatly accelerate the erosion. The smallest alkanes (n = 2, 3, 5, or 7) serve as models of polyethylene. For the case of ethane (n = 2), we explore the triplet potential energy surface of the following reaction: O(3P) + CH3-CH3 --> O-CH3 + CH3. Analogous reactions, in which O(3P) attacks a central carbon atom, are studied for the higher alkanes. Results obtained using the Hartree-Fock method, density functional theory, and, in the simplest case (i.e,, ethane), second-order Moller Plesset perturbation theory, Gaussian theoretical models (G1, G2, and G2MP2), and complete basis set (CBS-QB3) approaches are reported. We conclude that conditions in LEO are conducive to chain breaking in polyethylene caused by a single O(3P) attack.