This paper examines afresh features of ammonium-perchlorate (AP) combustion. Here an AP model, which predicts most experimental observations, is proposed. The one-dimensional aero-thermo-chemical field is captured through the solution of mass, energy, and species conservation equations. The unsteady one-dimensional phase heat transfer accounting for regression is solved for in the condensed phase. The uncertain parameters for AP pyrolysis, gas-phase reaction, and extent of surface exothermicity are chosen so that the most certain of the measured parameters of AP combustion, namely, pressure index of stable combustion (0.77 between 2 and 7 MPa), initial temperature sensitivity of burn rate, σ p (about 0.0021 to 0.0015 K -1), range of surface temperatures measured and suggested in several studies (∼850 to 875 K), and low-pressure deflagration limit (LPDL) at 300 K (∼2 MPa), are correctly predicted. The results obtained show the pressure index of AP combustion to be 0.77 and σ p to be 0.0024-0.0023 K -1. The LPDL is caused by a combination of loss of liquid layer and transient conduction into the condensed phase and not by heat loss. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.