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Mechanical Systems TDT Support Reaches Across NASA Programs

The NESC Mechanical Systems TDT provides broad support across NASA’s mission directorates. We are a diverse group representing a variety of sub-disciplines including bearings, gears, metrology, lubrication and tribology, mechanism design, analysis and testing, fastening systems, valve engineering, actuator engineering, pyrotechnics, mechatronics, and motor controls. In addition to providing technical support, the
TDT owns and maintains NASA-STD-5017, “Design and Development Requirements for Space Mechanisms.”

Mentoring the Next Generation
The NESC Mechanical Systems TDT actively participates in the Structures, Loads & Dynamics, Materials, and Mechanical Systems (SLAMS) Early Career Forum that mentors early-career engineers. The TDT sent three members to this year’s forum at WSTF, where early-career engineers networked with peers and NESC mentors, gave presentations on tasks they worked on at their home centers, and attended splinter sessions where they collaborated with mentors.

New NASA Valve Standard to Reduce Risk and Improve Design and Reliability
Valve issues have been encountered across NASA’s programs and continue to compromise mission performance and increase risk, in many cases because the valve hardware was not qualified in the environment as specified in NASA-STD-5017. To help address these issues, the Mechanical Systems TDT is developing a NASA standard for valves. The TDT assembled a team of subject matter experts from across the Agency representing several disciplines including mechanisms, propulsion, environmental control and life support systems, spacesuits, active thermal control systems, and materials and processes. The team has started their effort by reviewing lessons learned and best practices for valve design and hope to have a draft standard ready by the end of 2025.

Bearing Life Testing for Reaction Wheel Assemblies
The Mechanical Systems TDT just concluded a multiyear bearing life test on 40 motors, each containing a pair of all steel bearings of two different conformities or a pair of hybrid bearings containing silicon nitride balls. The testing confirmed that hybrid bearings outperformed their steel counterparts, and bearings with higher conformity (54%) outperformed bearings with lower conformity (52%). The team is disassembling and inspecting the bearings, and initial results have been surprising. The TDT was able to “recover” some of the bearings that failed during the life test and get them running as well as they did when testing began. Some bearings survived over five billion revolutions and appeared like new when they were disassembled and inspected. These results will be published once analysis is complete.

X-57 Design Assessment
The Mechanical Systems TDT was asked by the Aeronautics Mission Directorate to assess the design of the electric cruise motors installed on X-57. The team responded quickly to meet the Project’s schedule, making an onsite visit and attending numerous technical interchange meetings. After careful review of the design, the TDT identified areas for higher-level consideration and risk assessment and attended follow-on reviews to provide additional comments and advice.

CLARREO Pathfinder Inner Radial Bearing Anomaly
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder was designed to take highly accurate measurements of reflected solar radiation to better-understand Earth’s climate. During payload functional testing, engineers detected a noise as the HySICS pointing system was rotated from its normal storage orientation. Mechanical Systems TDT members reviewed the design and inspection reports after disassembly of the inner bearing unit, noticing contact marks on the bore of the inner ring and the shaft that confirmed that the inner ring of the bearing was moving on the shaft with respect to the outer ring. Lubricant applied to this interface resolved the noise problem and allowed the project to maintain schedule without any additional costs.

JPL Wheel Drive Actuator Extended Life Test Independent Review Team
A consequence of changes to its mission on Mars will require the Perseverance Rover to travel farther than originally planned. Designed to drive 20 km, the rover will now need to drive ~91 km to rendezvous and support Mars sample tube transfer to the Sample Retrieval Lander. The wheel drive actuators with integral brakes had only been life tested to 40 km, so a review was scheduled to discuss an extended life test. The OCE Science Mission Directorate Chief Engineer assembled an independent review team (IRT) that included NESC Mechanical Systems TDT members. This IRT issued findings and guidance that questioned details of the JPL assumptions and plan. Several important recommendations were made that improved the life test plan and led to the identification of brake software issues that were reducing brake life. The life test has achieved 40 km of its 137 km goal and is ongoing. In addition, software updates were sent to the rover to improve brake life.

Orion Crew Module Hydrazine Valve
When an Orion crew module hydrazine valve failed to close, the production team asked the Mechanical Systems TDT for help. A TDT member attended two meetings and then visited the valve manufacturer, where it was determined this valve was a scaled-down version of the 12-inch SLS prevalve that was the subject of a previous NESC assessment and shared similar issues. The Orion Program requested NESC materials and mechanical systems support. The Mechanical Systems TDT member then worked closely with a Lockheed Martin (LM) Fellow for Mechanisms to review all the valve vendor’s detailed drawings and assembly procedures and document any issues. A follow-on meeting was held to brief both the LM and NASA Technical Fellows for Propulsion that a redesign and requalification was recommended. These recommendations have now been elevated to the LM Vice President for Mission Success and the LM Chief Engineer for Orion.

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Meagan Chappell

NESC Assists in Heatshield Investigation

NASA’s uncrewed Artemis I mission launched from KSC on November 16, 2022. After a successful mission that included orbiting the Moon, the Orion spacecraft returned to Earth splashing down in the Pacific Ocean on December 11, 2022. While the spacecraft made a safe return to Earth, postflight inspection of Orion’s thermal protection indicated that the base heatshield did not perform as expected. The heatshield is composed of Avcoat, an ablative material designed to protect the crew module during the nearly 5000ºF temperatures experienced during atmospheric entry upon return from the Moon. Specifically, inspection revealed more than 100 locations where the charred Avcoat material chipped away from the heatshield.

The NESC formed a team of subject matter experts from across and outside of the Agency to assist the Orion Program team in the overall investigation. NESC team members are supporting or leading efforts in multi-physics analysis, material testing, fault tree and root cause analysis, aeroscience review, analysis peer review, nondestructive evaluation (NDE), as well as investigation of alternative heatshield concepts.

 The NESC works closely with the Artemis I Char Loss Team to ensure the observed material loss is thoroughly understood so that decisions may be made regarding use for upcoming crewed missions. To date, NESC contributions have included pathfinding NDE techniques for postflight heatshield inspection, investigation of key Avcoat material properties and behavior, and providing key inputs to the fault tree development and disposition to guide a thorough investigation of possible causes.

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Meagan Chappell

Laboratory Director Tawnya Plummer Laughinghouse

“When I transitioned from Spelman to Georgia Tech, it was probably the first time in my life that I had a professor that made me question if I belonged or had what it takes. Previously, I was always used as an example of how students should study, and now, in my first chemical engineering class, I would raise my hand for a question and wouldn’t get recognized, or my question would be followed by, ‘I’m not sure I understand what you’re saying, Miss Plummer.’

“I was struggling with imposter syndrome before I knew what that was, wondering, ‘Have I just been in some dream world up until now? Am I not as smart as I thought I was?’ I would be in my room just knocking out homework problems, no problem, but I would get in class, and it was almost like I’d freeze up. [My professor] would be walking around the room, and I could not make my brain work. I really struggled through that and did not pass that class – the first time I had ever not passed a class – and this was supposed to be my major!

“…Sometimes you look around and wonder why you don’t see a lot of [people of color] in some positions, and it’s probably because of situations like this where we have such high standards but feel we cannot meet them. We don’t give ourselves grace. We assume, ‘This obviously isn’t for me.’ 

“…But I knew I could do it. I had to, number one, get out of my head and, two, realize not everyone will be a fan or in your corner cheering for you… As a young college student, it was the first time I ever faced [this situation], and it buckled me. It set me back until I realized that I could do it and that my worth wasn’t based on what someone else thought of me or my abilities…I went back that next semester with a new mindset and determination, and I passed that class with an A and moved on through the rest of my engineering classes.

“That [experience] really informed the type of leader I am and taught me how to make sure that everybody has a voice and feels like they belong. Looking back, I thought it was the worst thing in the world when I was going through it, but now I see it was exactly what I needed at that point in my life to understand that I’m meant to be here doing what I am doing. I learned to give myself grace. If I had pulled myself out of that STEM major, I would never have been managing a technology demonstration program for NASA that launched ten technologies into space.”

– Tawnya Plummer Laughinghouse, Director of the Materials and Processes Laboratory, Engineering Directorate, NASA’s Marshall Space Flight Center

Image Credit: NASA/Charles Beason
Interviewer: NASA/Tahira Allen

Check out some of our other Faces of NASA. 

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Tahira S. Allen

Hang a Shining Star Upon the Highest Bough

This new view of the “Christmas tree cluster” NGC 2264, released on Dec. 17, 2024, combines data from NASA’s Chandra X-ray Observatory and optical data from astrophotographer Michael Clow’s telescope in Arizona. Chandra data is represented in red, purple, blue, and white, while optical data is in green and violet.

Located about 2,500 light-years from Earth, NGC 2264 is a cluster of young stars between one and five million years old. The stars are seen here as blue and white lights surrounded by swirls of gas—the “pine needles” of the tree—with green representing light in the visible spectrum.

Read more about the “Christmas tree cluster” – and the “cosmic wreath.”

Image credit: X-ray: NASA/CXC/SAO; Optical: Clow, M.; Image Processing: NASA/CXC/SAO/L. Frattare and K. Arcand

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Monika Luabeya