Maintainability and Reliability of Environmental Control/Life Support Systems

Extensive maintainability (M) and reliability (R) studies of a number of manned spacecraft missions indicate that the Environmental Control/Life Support System (EC/LSS) generally requires more scheduled and unscheduled maintenance than any other subsystem. This paper summarizes the EC/LSS M and R analyses performed on some of these studies. The expected redundancy and spares required to achieve a desired reliability is discussed. The requirements for scheduled and unscheduled maintenance are evaluated in terms of expected spares usage, maintenance time, and potential problem areas.