A prototype expert system was developed for maintaining autonomous operation of a Mars oxygen production system. Normal operation conditions and failure modes according to certain desired criteria are tested and identified. Several schemes for failure detection and isolation using forward chaining, backward chaining, knowledge-based and rule-based are devised to perform several housekeeping functions. These functions include self-health checkout, an emergency shut down program, fault detection and conventional control activities. An effort was made to derive the dynamic model of the system using Bond-Graph technique in order to develop the model-based failure detection and isolation scheme by estimation method. Finally, computer simulations and experimental results demonstrated the feasibility of the expert system and a preliminary reliability analysis for the oxygen production system is also provided. Ash, Robert L. and Huang, Jen-Kuang and Ho, Ming-Tsang EXPERT SYSTEMS; FAILURE MODES; MAINTENANCE; MARS ATMOSPHERE; OXYGEN PRODUCTION; AUTONOMY; BOND GRAPHS; COMPUTERIZED SIMULATION; DYNAMIC MODELS; FAULT DETECTION; RELIABILITY ANALYSIS...