The results of experimental study of ignition process of composite solid propellants based on ammonium nitrate and energetic binder containing aluminum powders of various particle sizes by CO(2)-laser radiation in air (with ambient pressure) are presented. Partial or complete replacement of micron-sized aluminum powder on Alex ultrafine powder as part of composite solid propellants leads to the reduction of ignition time by decrease the temperature of burning surface, thickness of reaction layer and by increase of the heating rate in condensed phase. It was found that the efficiency of ultrafine aluminum powder additives in formulations increasing with decreasing of laser radiation intensity. The temperature of the formulation's burning surface at the ignition moment was measured by usage of the thermal imager. The temperature of burning surface under ignition by radiant heat flux was 545-660 degrees C (formulations containing ultrafine aluminum powder) and 713-820 degrees C (formulations with micron-sized aluminum powder) for the radiation intensity 60 W/cm(2). (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.