Reliability-driven design of nuclear-powered spacecraft

An initial exploration of the safety and reliability of a nuclear thermal propulsion (NTP) system for a representative manned Mars mission is presented. The hypothetical mission goal, 0.95, is apportioned among 15 mission phases. Using optimistic and pessimistic assumptions yields an apportioned reliability goal for an NTP phase between 0.987 and 0.996. The reliability of the reactor and the LH₂ turbopump subsystems appear to be critical elements. The reliability of these subsystems is estimated using a variety of field data. It is credible that the NTP system can meet its reliability goal during active thrusting (3 cumulative hours). The dormancy period, 9120 hours between thrust phases, was studied using several models and data sources. It seems that the dormancy period reliability will be of equal or controlling importance in meeting the system reliability goal