The decomposition characteristics of five candidate polysulfide (LP-33) based ramjet solid fuel formulations are evaluated using thermogravimetric analysis and differential scanning calorimetry. The formulations are variants on the polymer crosslink mechanism and the doping mass fraction of elemental sulfur. Four fuel candidates are oxidatively cured and one formulation is cured with isocyanates. Post-cure, the Shore-A hardness of each sample is measured followed by TGA and DSC analysis. The objective of this research is to develop a solid fuel ramjet formulation with thermal decomposition onset temperatures lower than conventional ramjet fuels while maintaining a Shore-A hardness of at least 30. The results show that polysulfide based formulations decompose at temperatures approximately 120 C lower than hydroxyl-terminated polybutadiene based fuels. Additionally, the results demonstrate that the decomposition onset temperature, and the heat of decomposition can be further reduced with the addition of elemental sulfur. Published by Elsevier Inc. on behalf of The Combustion Institute.