Damage Propagation Assessment - A Causal Model Approach for Design and Operations

Qualtech Systems, Inc. (QSI) in collaboration with Dr. Stephen B. Johnson of Dependable Systems Technologies (DST) proposesa novel, causal graph-based model and a systematic modeling methodology for assessing damage propagation due to one or multiple originating faults and how the propagation affects and damages other components. In fault propagation, downstream components from the root-cause fault which rely on its function, may also fail. When the root cause is mitigated, those downstream components resume their normal operating behavior. During damage propagation, the originating faults damage, leads to the failure effects in which physical damage to downstream components is a consequence, such that those components can no longer function nominally. Even if the originating fault recovers or is replaced or bypassed, the downstream damaged components do not recover and continue to remain in a failed state. This proposal aims to create a new software module for QSIs TEAMS tool suite that incorporates component damage as a failure cause and can identify the differences between components in which failure effects pass through or cause only functional impairment versus those that can cause physical damage. This new capability will enable the modeler to represent damage induced component failure modes and their interaction with functional failure modes. Distinction between the two, where the functional failure mode can be caused by damage or bad inputs from impairments upstream, will allow TEAMS to generate a more comprehensive and accurateassessment of the health of the components of the system and facilitate appropriate mitigation actions. In the last two decades, fault management has evolved to a model-based engineering discipline. Key to these model-based approaches is the capability to model the spread of failure effects from initial causes (internal failure modes or external causes such as micrometeorite strikes or radiation effects in space). In various NASA Safety and Mission Assurance (S&MA) methodologies such as failure modes and effects analyses (FMEA), hazard (system safety) analyses, and probabilistic risk analysis (PRA), assessing the effects of failures are one of a kind, constructed manually and are explicit. Qualtech Systems, Inc. (QSI) in collaboration with Dr. Stephen B. Johnson of Dependable Systems Technologies (DST) proposes a novel, causal-model based, systematic methodology for assessing damage propagation due to one or multiple originating faults and how the propagation affects and damages other components, thereby facilitating improved system design for fault tolerance and onboard fault management decision-making especially for autonomous missions. This proposal aims to create a novel capability for QSI’s TEAMS® tool suite that allows incorporation of damage modes as part of component failure modes supported by causal graph-based AI methods for comprehensive determination of the equipment health that includes both functional failures as well as damage induced failures. The novel technology will help distinguish between components in which failure effects ‘pass through’ or cause only functional impairment versus those that can cause physical damage for improved decision-making during system design and operations. The key technical objectives are the following: 1) Determining potential damage effect propagation from faults and help determine fault (damage effect) containment zones during vehicle design, and, 2) Runtime determination of component-level damage effects from root-cause faults and the consequent impacts on vehicle function that can improve vehicle-level decision-making especially for missions with significant needs for autonomy. The proposed deliverable at the end of the Phase 2 contract is a new TEAMS damage assessment product module that will work seamlessly with QSI's COTS TEAMS tool suite. For the final Phase 2 review, a comprehensive demonstration using realistic failure scenarios, of the new capabilities using a section of the Lunar Gateway fault model with damage modes incorporated will be provided.
Benefits: The proposed technology is aimed at facilitating effective usage of model-based systems engineering for improving fault tolerance and mitigation response capability during design, and the concomitant software tool for supporting its implementation, will allow NASA to better design, plan and execute future Science Missions. The proposed technology is positioned for direct applications for NASA missions that deploy complex equipment such as the Lunar Gateway, the Space Launch System, the Human Lander, Europa Clipper and rovers such as the VIPER. We envisage the proposed technology to be of significant interest for DoD’s Mission planning and Rapid design of space missions/satellites where model-based design processes will be used for supporting infrastructure Space services capabilities. QSI is currently working with the Army for fault management design of the Remote Combat Vehicle (RCV) and plan to apply this technology for that effort.