Abstract: Unlike the conventional orbital debris shield with inert materials, the impact-initiation property of energetic materials under hypervelocity impact plays a fundamental role in improving the protection ability. For the fragmentation mechanisms of the projectile under hypervelocity impact are closely related with the impact-initiation property, it is very important to analyze the protection mechanism of the energetic materials and the shock pressure generated by impact and explosion. Firstly, the fracture characteristics of projectiles under the experimental conditions are determined through analyzing the damage characteristics of the rear wall. Then, based on the one-dimensional shock wave theory, the impact pressure of projectiles is obtained by combining with the thermal reaction model for the chemical reaction efficiency. From the experimental results, the critical impact velocities when the projectile produces the same impact pressure in both energetic and inert materials for the PTFE/Al energetic complete reaction and the fragmentation initiation threshold of the projectile are obtained.