Abstract <p>Whether solid rocket motors (SRMs) under external fragmentation stimulation can meet the required response types has always been a concern for various countries. Understanding the response characteristics of propellant charges impacted by fragments and revealing potential reaction mechanisms are crucial to the safety evaluation of SRMs and developing high-energy and low-vulnerability propellants. In this study, a fragment impact experiment of GAP/RDX/TEGDN (GRT) propellant charge is designed using a 14.5 mm ballistic gun and high-speed camera to capture the time history images of charge response process under different ballistic behaviors. The relationship between the response characteristics of the charge, underlying reaction mechanisms, and the two ballistic limits was analyzed based on captured images and measured ballistic data. Resulting indicate that for tungsten alloy ball fragment with a diameter of 10.0 mm positive impacting GRT propellant charge with 3&#xa0;mm thick cylindrical steel shell, the ignition threshold velocity is consistent with the ballistic limit for penetration of the shell by the fragment, and below this ballistic limit value, the response type of charges is “No Reaction”. When there is a significant delayed response, caused by RDX crystals hotspot ignition rather than AP particles, the response type of charges under full-perforated is combustion. Only when many AP particles and RDX crystals participate in hotspot ignition simultaneously, and initial fragment velocity exceeds 2.2 times the charge ballistic limit, can the charge undergo more violent reactions than combustion.</p>