Theoretical Analysis for Long-Term Space Life Support Reliability

Space is characterized by many uncertainties, natural and human induced, for manned missions in hostile environments. Therefore, human operations in space require reliable Life Support Systems (LSS) capable to maintain functionality for long durations. However, the ultimate theoretical analysis of LSS reliability for space applications is very difficult due to many unknown and possibly undiscovered factors which might affect system functional performance.

In this work the conceptual approach for a complex LSS reliability analysis is reviewed. Methodology based on Fokker-Planck statistical equation is proposed and investigated. According to these preliminary considerations, a few critical variables are identified and determined: 1) average rate of material recirculation in LSS; 2) LSS and environment uncertainty level (level of material circulation rate fluctuations); and 3) human control level and its limitations. These variables are suggested for further iterations, more detailed analysis and modeling. The final conclusion can be formulated: certain balance between material circulation rate, mission development and LSS functioning uncertainty, and level of human control is required for overall mission reliability. Formula describing this conclusion quantitatively is provided.