The plume flow and radiative base heating of a solid rocket have been important factors for rocket survivability in the modern battlefield, in which the standard of technology determines the dominant position. To enhance rocket survivability and reduce base heating, infrared (IR) signatures emitted from an exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics in the plumes exhausted from a solid rocket operating at Mach number of 1.6 and altitudes of 5km and 10km, respectively, are numerically examined to find the physics related to the plume flow and radiative characteristics. The plume flow and radiative characteristics are obtained using a pre-conditioning method and weighted sum of gray gases model (WSGGM) coupled with finite volume method for radiation, respectively, and the IR signature at each location is post-processed with the narrow band-based WSGGM after plume fields are developed. After validating models adopted in this work by comparing with other solutions, the plume flow field, IR signature, and radiative base heating characteristics are investigated by changing such various parameters as altitude and particle concentrations in the exhaust plume. As a result, it is found that the particular wavelength IR signature level has high spectral characteristics because of CO2 and H2O behaviors in the plume, and the radiative heat flux coming into the base plane decreases with higher flight altitude and longer distance from the nozzle exit.