Application of Diagnostic Analysis Tools to the Ares I Thrust Vector Control System

Abstract

The NASA Ares I Crew Launch Vehicle is being designed to send astronauts into Earth orbit in support of missions to the International Space Station, to the moon, and beyond. The launch vehicle is an in-line two-stage rocket with the crew vehicle, Orion, on top of the stack. The Ares I is undergoing design and development utilizing commercial-off-the-shelf tools and hardware when applicable, along with cutting edge launch technologies and state-of-theart design and development techniques to ensure a safe, reliable, cost-effective space transportation system. In support of the vehicle’s design and development, the Ares Functional Fault Analysis group was tasked to develop an Ares Vehicle Diagnostic Model (AVDM) and to demonstrate the capability of that model to support failure-related analyses and design integration. The AVDM is a directed graph model of failure effect propagation paths within the vehicle architecture and is a comprehensive representation of the system’s failure space behavior. The AVDM is intended to support system engineering activities during the design process, and to provide diagnostic support throughout the development and deployment of the Ares I Launch Vehicle. During the Ares I design phase, the AVDM has been demonstrated to be valuable in the systems engineering process for assessing the completeness of schematics, and improving quality of various system design documents and analyses. The AVDM, along with supporting tools, has provided detection and fault isolation information to determine which components meet the diagnostic requirements for launch pad replacement and to assess system response to off-nominal conditions. One important component of the AVDM is the Upper Stage (US) Thrust Vector Control (TVC) diagnostic model—a representation of the failure space of the US TVC subsystem. This paper first presents an overview of the AVDM, its development approach, and the software used to implement the model and conduct diagnostic analysis. It then uses the US TVC diagnostic model to illustrate details of the development, implementation, analysis, and verification processes. Finally, the paper describes how the AVDM model can impact both design and