Collision probability evaluation of SRM slag during orbital lifetime

Abstract

At the end of combustion, a solid rocket motor (SRM) in orbit emits combustion products with relatively large particle sizes (slag). ISO 24113:2023 “Space debris mitigation requirements” defines criteria to limit debris emission 1 mm or larger in the LEO protected region. JAXA's “Space debris mitigation standard,” JMR-003E, sets out the same requirements. Hence, JAXA has begun an improvement study on SRM slag emissions as it develops the next generation of SRMs to conserve the orbital environment by significantly reducing SRM slag larger than 1 mm. However, ensuring the complete prevention of larger SRM slag emission is technically challenging. Thus, we are alternatively working to establish a risk evaluation method and criteria based on the collision probability (Pc) of SRM slag during its orbital lifetime. Based on ground firing tests, this study estimated the number and particle size of SRM slag in orbit emitted during the Epsilon and Epsilon S launch missions. The Pc per mission during the orbital lifetime was calculated and provisionally set to 10^–3 for currently operational spacecraft. This paper discusses its acceptability to JAXA.