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Ann Patterson-Hine Presents at the 2020 Virtual Systems Engineering Workshop
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Ann Patterson-Hine Presents at the 2020 Virtual Systems Engineering Workshop

Ann Patterson-Hine gave an invited presentation at the Model-Based Systems Engineering (MBSE) Exposition, a special session in the 2020 Virtual Systems Engineering Workshop on September 23rd. The presentation, Goal Function Tree applied to Space Launch System (SLS) Abort Analysis, described the methodology that is being utilized by SLS Mission and Fault Management (FM) in the development of the abort trigger suite for Artemis missions.

BACKGROUND: The Goal Function Tree (GFT) describes the goals that a system must achieve to meet mission and safety objectives, and the functions that must be performed in order to achieve those goals. Thus, a GFT is a top-down functional decomposition of system functions arranged by major system phase and configuration, which defines what functions the system must perform successfully. The GFT representation is not merely a functional decomposition, however, because it inherently integrates goals and functions together.

The GFT representation and its corresponding development methodology provide a means to represent, decompose, and elaborate system goals and functions in a rigorous manner that connects directly to design through use of state variables. The state variable-based approach provides the means to directly connect FM to the design by identifying the range in which state variables must be controlled to achieve goals, and conversely, the failures that exist if system behavior goes out of that range. This in turn allows for systems and FM engineers to determine which state variables to monitor to determine if a goal is not being achieved. The GFT representation provides a unified approach to early-phase FM detection development, and due to its rigor is also used to assist in requirements verification.

NASA PROGRAM FUNDING: Space Launch System

TEAM: Vijay Baskaran, David Greeson (MSFC), Stephen Johnson (MSFC/DSI), Ann Patterson-Hine, Greg Pisanich, Julian Rivera-Cruz, and David Teare (MSFC)

POINT OF CONTACT: Ann Patterson-Hine, ann.patterson-hine@nasa.gov

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