Integrating Model-Based Systems Engineering and Fault Management for Autonomous Space Missions

Achieving fully autonomous space missions hinges on the capability to autonomously detect and rectify faults without human intervention. To tackle this challenge and provide model-based support for both system design and operations, a crucial link must be established between fault management (FM) and model-based systems engineering (MBSE). This integrated approach was successfully validated by model-based generation of failure modes and effects analyses and fault trees, utilizing early design data from NASA's HelioSwarm mission.

As NASA advances its endeavors, such as the Artemis program and upcoming deep-space scientific missions, the demand for enhanced system autonomy and resilience has become paramount. Autonomous operations necessitate fault management (FM) software capable of identifying and mitigating anomalies in space without requiring human input. The development of autonomous missions demands a multidisciplinary strategy that merges FM with the model-based systems engineering (MBSE) framework, commonly employed in mission design. This integration ensures that resilient, fault-tolerant systems are architected, modeled, and incorporated from the initial design stages.

To meet this need, NASA has awarded a Phase II Small Business Innovation Research (SBIR) contract to Qualtech Systems Inc. (QSI). This funding supports the development of FM capabilities and enhancements to their commercial toolset, TEAMS®. This toolset, which emerged from earlier NASA-funded SBIR work, is designed to support the HelioSwarm mission and other NASA heliophysics initiatives.

The QSI Approach

A key aspect of this initiative was to integrate system health management (SHM) and FM directly into the systems engineering (SE) process. SHM/FM encompasses a suite of mechanisms aimed at achieving mission objectives by preventing failures or detecting and mitigating them if they occur. The SE process, in turn, coordinates, cross-checks, and integrates system components to fulfill mission goals, playing a vital role in the design, specification, and verification and validation (V&V) of systems. NASA frequently utilizes a model-based approach for its SE process, often employing the Systems Modeling Language (SysML) as its foundation.

Despite their practical interconnectedness with SE, SHM/FM practices have historically lacked tight integration. Often, SHM/FM is addressed only after a baseline system has been designed, essentially treating it as a reactive solution rather than proactively preventing issues. Furthermore, SE and SHM/FM frequently involve separate teams of subject matter experts with siloed knowledge, which can lead to inconsistent modeling methodologies and analysis outcomes, potentially causing inefficiencies throughout the mission lifecycle.

The approach developed by the QSI team, with NASA's funding, embeds SHM/FM directly within the MBSE process from the project's inception. This methodology allows for the evaluation of FM designs within an operational context by demonstrating how proposed SHM/FM strategies can mitigate the effects of simulated component-level physical and functional failures. This technique also facilitates trade studies to assess the advantages of different FM architectures during the design phase.

As part of this SBIR effort, QSI collaborated with the SysML v2 Submission Team (SST), a diverse group of end-users, vendors, academics, and government liaisons dedicated to developing specifications for SysML v2, the latest iteration of SysML. The QSI team incorporated FM concepts and modeling standards into SysML v2, subsequently demonstrating how these SysML v2 models could be translated into the failure space models generated by QSI's toolset.

This capability empowers systems engineers to leverage QSI's commercial modeling toolset to analyze the FM aspects of a system design documented in SysML v2. By capturing failure causes and impacts, QSI's toolset enables mission designers to conduct Failure Modes, Effects, and Criticality Analyses (FMECA) and Fault Tree Analyses (FTA) to evaluate, quantify, and enhance system diagnostics and availability. Moreover, the toolset offers recommendations for design improvements, such as optimal sensor placement on spacecraft, based on these analyses, and presents these recommendations in easily understood, industry-standard formats for seamless integration into the design.

During this SBIR project, QSI's toolset was also enhanced to interface with an MBSE framework, streamlining the creation, evaluation, and selection of FM concepts for mission designs. The toolset now allows FM concepts to be tested early in the design process, ensuring adequate detection and diagnosis are built into the system architecture. This can potentially reduce overall development costs, improve communication and coordination among mission team members, and mitigate development risks related to both cost and schedule.

The HelioSwarm Demonstration

HelioSwarm is poised to revolutionize our understanding of solar wind turbulence and the interconnected Sun-Earth system. The mission employs a constellation, or "swarm," of one hub and eight co-orbiting small satellites to conduct unprecedented simultaneous, multiscale measurements of magnetic field fluctuations and proton flows within the dynamic cislunar space environment. Due to plasma turbulence's ability to transfer energy across a wide range of scales, from fluid-scale motions to kinetic-scale particle dynamics, a comprehensive understanding cannot be achieved from a single measurement point or at only one scale. HelioSwarm's spacecraft will operate with separations ranging from tens to thousands of kilometers, enabling scientists to reconstruct the three-dimensional structure and dynamics of turbulent space plasma. These observations will illuminate how energy propagates through the solar wind, transforming our comprehension of fundamental plasma processes active near Earth, around the Sun, and across the universe.

Plasma turbulence is the mechanism by which energy within fluctuating magnetic fields and plasma motion cascades from larger to smaller spatial scales. As the cascade nears small spatial scales associated with kinetic dissipation, the energy is converted into particle heat. Without turbulent cascades in space plasmas, much of the universe would be significantly colder than observed. Given its fundamental thermodynamic role in fluids, including space plasmas, many scientists consider turbulent fluids to be the most significant unsolved problem in classical physics.

The QSI team developed a SysML v2 design model of HelioSwarm's subsystems and top-level mission requirements, effectively capturing the flowdown from mission objectives to the final design. They then utilized their enhanced toolset to translate the HelioSwarm SysML v2 model into an FM model. The HelioSwarm models encompass key subsystems of the hub spacecraft and the eight node satellites, including those for command and data handling; electric power; attitude control; propulsion; thermal systems; separation hardware; payload sensors; and ground and space communications. Using the QSI toolset, mission designers generated FMECA and FTA reports, which were then compiled into a standardized SysML report. Furthermore, these FM analyses yielded recommendations, such as optimal sensor placement, which were provided as proposed updates to the system design. This process will be instrumental in designing small spacecraft swarms with inherent redundancy to enhance scientific observations and support other NASA objectives, including providing mission support for lunar surface operations.

Relevance to Future NASA Missions and Non-NASA Applications

The technology developed through this recent SBIR effort holds significant potential value for future NASA missions, particularly those requiring autonomous operation. The QSI TEAMS® toolset has been designated as the baseline for Vehicle Systems Management functions on NASA's Gateway project and remains relevant for future human-rated spacecraft. System design engineers can employ this technology to integrate fault mitigation strategies, thereby enhancing designs with a deeper understanding of overall system resilience, right from the initial design phase.

This technology may also find applications beyond NASA. Comprehensive and efficient FM analyses and architecture trade studies are critical for complex and high-value military systems such as aircraft, naval vessels, submarines, and modern ground vehicles. Additionally, this technology could be applicable to emerging commercial space systems, civilian aviation and maritime systems, transportation, and power generation and distribution equipment.