AbstractViscoelastic damage properties of NEPE (Nitrate Ester Plasticized Polyether) solid propellant have been studied in this work. This work focuses on the creep and fatigue damage evolution. Cyclic loading tests for NEPE solid propellants are conducted with different stress ratios. Then a modified model incorporating viscoelasticity and damage evolution is presented and used to fit the experimental data. The fitting results show that the model is suitable to characterize the viscoelastic damage properties of NEPE propellants with different stress ratios. Based on the model with parameters for NEPE propellants, the damage parameter D are obtained. The damage evolution curves under different loading conditions are given. It is shown that, from the predicted damage evolution curves, the critical damage parameter Dcr at the fracture points can be used to predict the fatigue lives under different loading conditions.