Testability modeling and analysis of a rocket engine test stand

Abstract

This paper describes a testability analysis methodology that improves efficiency in maintainability and availability of a system, provides improvements in the overall capabilities of this system, and has historical verifiable data to compare the testability analysis metrics to the observed discrepancy reports. Here is a methodology that illustrates the use of a testability analysis tool to aid in the design and development of a health management system. Included is a brief discussion of how the model's testability output metrics can be used in conjunction with other types of model outputs for optimization purposes. Some top-level figures of merit are targeted here to verify that the testability analysis data is adequate and valid. It is shown here that this technology can improve maintenance efficiency, and aid in automating an integrated vehicle health management (IVHM) system, while reducing the need for human interaction for decision making, data acquisition and testing. The technology identifies critical components in the system, and prescribes a fast and accurate failure detection and isolation method that diagnoses faults to the lowest level of ambiguity. The safety, reliability and testability metrics identified here are used to reduce the test stand operator's stress levels by increasing the confidence in the operational state of the system, especially those related to critical components, before and during tests. Consequently, confidence in the test stand output data from the test article is realized. It is proven here that this technology also adds confidence in sustainability improvement of the test stand, which is above and beyond meeting just performance specifications. False alarms and false replacement concerns are also addressed here. The importance of using today's testability analysis tools for assessing and optimizing integrated vehicle health management systems is emphasized in this paper. With this technology we were able to model a rocket engine test stand and utilize the existing test stand sensors as a baseline for the testability analysis. We used the observed discrepancy maintenance reports provided by the test stand engineers to assign failure modes to the components.