The problem of unsteady energy transfer during the expansion of a spherical mass of compressible, gray radiating gas at near-atmospheric pressure is analyzed. The gas is assumed to be perfect and in local thermodynamic equilibrium. Scattering of radiation as well as ionization and dissociation phenomena are neglected. Energy transfer by conduction is assumed to be insignificant compared to that by radiation or convection. The formulation of the problem is based on first principles of radiative transfer and gas dynamics and is thus valid for a medium of arbitrary optical radius. A finite difference scheme is employed to obtain a first approximation to the solution of the conservation equations. The numerical results are presented graphically for a wide range of parameters of physical interest.