Failure analysis of full-scale 76mm sounding rocket motor during static fire ground test

This report presents a failure analysis of a full-scale static fire ground test of a 76 mm solid rocket motor developed as a sustainer motor for a two-stage high-altitude sounding rocket. The test, intended to validate motor performance and structural integrity prior to airframe integration, resulted in a catastrophic failure shortly after ignition. The propulsion system utilized a high-energy, semi-pourable ammonium perchlorate composite propellant (APCP) formulation cast into five face-bonded grains with an aft finocyl geometry and a head-end ignition system. The failure event was rapid and complete, preventing nominal data collection. Post-test inspection revealed significant structural failure of the motor casing and expulsion of several test stand components. This analysis reconstructs the failure timeline using available video and photographic evidence, evaluates potential failure mechanisms—including over-pressurization, liner delamination, and ignition overdrive—and provides recommendations for corrective design actions. The findings contribute to future static fire protocols and motor development for high-impulse solid rocket motor propulsion systems.