Model-based Diagnostics for Rocket Systems

A diagnostic software package is currently being developed at NASA Lewis Research Center that utilizes qualitative model-based reasoning techniques. These techniques can provide diagnostic information about the operational condition of the modeled rocket engine system or subsystem. The diagnostic package combines a qualitative model solver with a constraint suspension algorithm. The constraint suspension algorithm directs the solver’s operation to provide valuable fault isolation information about the modeled system. A qualitative model of the Space Shuttle Main Engine’s oxidizer supply components was generated. A diagnostic application based on this qualitative model has been constructed to process four test cases: three numerical simulations and one actual test firing. The diagnostic tool’s fault isolation output compared favorably with the input fault condition.