Extended Testability Analysis Tool User Guide

Abstract

This paper provides an overview of the analysis and reporting capabilities of the Extended Testability Analysis (ETA) Tool which is currently being prepared for release by researchers at the NASA Glenn Research Center. The ETA Tool is a software tool that augments the analysis and reporting capabilities of a commercial-off-the-shelf (COTS) testability analysis software package. An initial diagnostic assessment is performed by the COTS software using a qualitative, directed-graph model of the system being analyzed. The testability analysis from the COTS software provides failure effect detection and fault isolation metrics, and generates a dependency matrix that correlates the system failure modes with the tests available to detect those failure modes. The ETA Tool accesses system design information captured within the COTS-based diagnostic model, along with testability analysis output from the COTS software, and creates a series of six reports for various system engineering needs. The ETA Tool also allows the user to perform additional studies on the testability analysis results, by determining the detection sensitivity to the loss of certain sensors or tests. The ETA Tool was developed to support the NASA Ares I Crew Launch Vehicle design and development. The Ares Functional Fault Analysis (FFA) group was tasked to develop a diagnostic model that would become part of the Ares ground-based diagnostic system. The FFA group selected the COTS software to build a collection of subsystem models. These models were developed independently, while adhering to a set of FFA project-defined modeling conventions. The subsystem models were subsequently integrated into a vehicle-level diagnostic model. The diagnostic models have proven to be valuable system engineering tools, providing consistency in the verification of system engineering requirements and of results from various design studies. In addition to being requested by the Upper Stage Thrust Vector Control Design Team for off-nominal analysis and analytical verification of recoverable fault requirements, analysis reports from the ETA Tool have been requested by several Ares System Engineering groups, including: Ascent Risk Analysis, Launch Commit Criteria and Ground Logistics and Supportability.