Johnson Space Center’s Reliability and Maintainability (R&M) program is working on a new system that helps engineers and mission managers make better risk-informed decisions.
The Testability, Engineering and Maintenance System (TEAMS)-based approach, developed by Qualtech Systems Inc. (QSI), incorporates engineering data, field maintenance information and expert knowledge to build a complete graphical model of a system. For example, systems and R&M engineers are using the tool to virtually build a systems engineering model of the Orion spacecraft, which is part of the Multi-Purpose Crew Vehicle Program, and then analyze the spacecraft’s reliability.
Using an approach like TEAMS to model systems is called Model-Based Systems Engineering (MBSE). Applying MBSE to the assurance disciplines is called Model-Based Mission Assurance (MBMA). Johnson remains one of the most active and innovative centers in developing MBSE and MBMA concepts with researchers and practitioners, exploring a range of MBSE applications ranging from Systems Modeling Language (sysML)-based fault management to automated code generation.
TEAMS is a promising MBMA approach used in the aerospace industry by companies such as Pratt & Whitney, Sikorsky, and Boeing.
“TEAMS is one of the viable MBMA tool sets and represents one solution for MBMA implementation,” said Dr. John Evans, R&M program manager who supports MBMA development across NASA.
Now, Johnson plans to advance this system to perform quantitative risk assessment in real time.
“We’re just starting and still need to take a system and build it all the way,” said Vuong Pham, chief of the Space Systems and Technology Branch at Johnson, who has been working on TEAMS for several years.
R&M analyses such as the Failure Modes and Effects Analysis (FMEA) are document-based analyses like many assurance products. This process is labor-intensive, time-consuming and error-prone and often inhibits the design. MBSE and MBMA offer the opportunity to automate FMEAs and other R&M analysis. They also offer assurance disciplines the opportunity to be upfront in the design process.
“We’d like to get away from a manual process to an automatic one,” said Chris Noyes, vehicle system engineer in the Space Systems and Technologies Branch. “The difference is like moving from a slide rule to a calculator. The accuracy is much greater, and it is much more dependable.”
R&M engineers’ desire to decrease the time it takes to review document-based assurance products, such as FMEA, was another motivation for adopting TEAMS. Currently, R&M engineers receive these documents from a contractor about two weeks before a project’s milestone review. They then often spend the majority of their time up until the review cutoff time examining thousands of paper pages to evaluate the accuracy and completeness of the analyses.
“We don’t think this is a good way to continue,” Pham said. “If it takes too long to review, we would expect the quality to decrease. So we want something quick and easy that an engineer can review thoroughly in a short turnaround time.”
TEAMS allows R&M engineers to model various scenarios without building physical models. For example, they can model what would happen to a spacecraft given a failure or if it had multiple failures instead of just one. These models aid not only in design but also crew training programs and mission support.
The application of MBSE tools also has the potential to eliminate lost time due to design changes. Typically, systems and discipline engineers evolve the design configuration and product developers generate the design. The product developers may also make their own tweaks. If R&M engineers want to analyze the design, they often are not working with the most recent version of that design.
An MBSE model can contain the latest configuration available in real time and be readily accessible to R&M engineers. This, along with automated product generation, facilitates up-to-date analysis thereby eliminating duplication of effort and improving effectiveness.
Future Goals and Partnerships
The goal at Johnson is to continue to partner with QSI, as well as Montana State University, to develop a probabilistic tool, such as the Continuous Hazard Analysis and Risk Mitigation (CHARM) tool, and integrate it with TEAMS to quantitatively determine the real-time risk of loss of crew, loss of vehicle or loss of mission given component or subsystem failures.
TEAMS is not only used at Johnson but also other NASA centers. Other R&M engineers aid Johnson by testing TEAMS. A working group comprised of members from Ames Research Center, Glenn Research Center, Marshall Space Flight Center, Kennedy Space Center and the Jet Propulsion Laboratory, meets once a month to share knowledge, techniques and solutions.
“While their goals are not the same as ours and they may use the tool differently, we’re learning much from each other,” Pham said. “We talk about who’s doing what and what’s beneficial or not.”
The next steps for TEAMS will include further tests and modifications. The goal is to have the tool operational to support Exploration Mission-2, Orion’s first human exploration mission, in 2021.
“As more Safety and Mission Assurance [SMA] engineers and professionals learn about the system, we’re seeing more excitement and interest in the tool,” Noyes said. “It’s getting a lot of support.”
Moving MBMA Forward
The Office of Safety and Mission Assurance continues to evaluate and promote model-based engineering concepts for the agency. MBSE is gaining significant momentum with the widespread open application standards for sysML. TEAMS is one MBSE that has been in use and offers a solid potential for MBMA.
As the engineering community continues to develop model-based engineering, more than one viable approach will emerge for MBMA in the assurance community. This will be driven by each center’s needs and practices across NASA.
“Success for any given tool will depend upon interoperability in the larger design framework,” Evans said.