A Knowledge-Based

The complexity of space systems and increased costs for construction and operation make it necessary to both evaluate these systems in advance and to provide crew members with adequate advisory facilities in flight to determine the impact of changes in operational parameters. Currently, it is difficult to provide these facilities because of the need to weigh multiple objectives against one another when making system operation decisions. Simulation has long been recognized as a useful tool for studying the behavior of complex systems which are conceptually difficult to understand and often mathematically intractable. Unfortunately, there are problems which limit its utility. Factors which influence its use include: the timeliness of results, cost, accuracy, lack of flexibility, and extensive programming requirements. However, combining simulation methodologies with A.I. techniques yields a practical approach to simulation known as knowledge-based simulation. The result is a tool which not only aids in model development but makes specific recommendations based on simulation analysis output. This paper will describe an architecture for a knowledge-based simulator. The task of scheduling represents an area in which such a tool might be applied. More specifically, scheduling for crew and ground support activities for the shuttle and space station would benefit from the application of knowledge-based simulation. The knowledge-based simulator would allow the crew and support personnel to schedule and reschedule activities in a timely and flexible manner to examine and test possible plans.