In order to control the erosion rates of graphite nozzle at high operating pressures (up to 48 MPa), a nozzle boundary-layer control system (NBLCS) has been employed, which contains multiple center-perforated grains of ablative materials made of succinic acid (SA) and poly-vinyl acetate (PVA). This combination of the ablative materials is selected due to its relatively low pyrolysis temperature for generating fuel-rich gases. The pyrolysis product gases are supplied into the nozzle throat region slightly ahead of the throat location. This design not only introduces fuel-rich chemical species in the nozzle boundary-layer region but also helps to cool the nozzle throat surface. The fuel-rich gases can serve as scavengers for oxidizer-rich species produced in the rocket-motor combustor, thereby reducing the erosion rates of the graphite nozzles at high pressures. In order to control the nozzle erosion rate and perform a quantitative analysis on the effect of NBLCS, it is necessary to determine the pyrolysis behavior of SA/PVA grains. In this work, two separate experiments were conducted to determine the regression rate of SA/PVA grains under controlled heat flux or temperature conditions. One of these experiments involved the use of heated metal rod at known initial temperature for achieving conduction driven pyrolysis of SA/PVA grain and measurement of surface regression rate. These set of experiments provided data to form a correlation between heat flux and surface regression rate. In another experiment, rapid thermolysis of SA/PVA grain was performed with an FTIR diagnostics. It was found that when SA/PVA is heated, it melts and vaporizes without any noticeable chemical decomposition. The FTIR spectra of the gaseous products from SA/PVA grains showed no peaks of CO2, CO, H2O, and CH2O, which were expected in case of any chemical decomposition. The results of the latter experiment confirm that there is only melting and/or evaporation of SA/PVA grains during rapid heating by conductive heat transfer. These results were treated as empirical correlations and have been used in the computational simulation of nozzle throat erosion processes.