Efforts to improve spacecraft reliability prediction method to evaluate the probability of successful disposal in ISO 24113:2019

Abstract

The new requirement in ISO 24,113:2019, "The probability of successful disposal of a spacecraft or launch vehicle orbital stage shall be at least 0,9 through to the end of life." is uneasy to show compliance because there is no accurate prediction method. This probability is usually calculated based on the reliability, but it is difficult to achieve 0.9 with the reliability prediction method applied to JAXA's spacecraft because it is based on MIL-HDBK-217F, with worst case temperature condition. Though the reliability of the JAXA's spacecraft can not achieve 0.9, they have survived soundly through the design life unless a specific failure occurs. It is recognized that the MIL-HDBK-217F based prediction method is conservative to the actual probability of successful disposal. Therefore, JAXA investigated the improvement of the prediction method to bring the reliability closer to the actual probability of successful disposal.