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By NASA
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.
NASA’s Perseverance Mars rover selfie taken in July 2024.
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s Perseverance Mars rover used its right-front navigation camera to capture this first view over the rim of Jezero Crater on Dec. 10, 2024, the 1,354th Martian day, or sol, of the mission. The camera is facing west from a location nicknamed “Lookout Hill.”NASA/JPL-Caltech NASA’s Perseverance Mars rover captured this scene showing the slippery terrain that’s made its climb up to the rim of Jezero Crater challenging. Rover tracks can be seen trailing off into the distance, back toward the crater’s floor.NASA/JPL-Caltech The road ahead will be even more scientifically intriguing, and probably somewhat easier-going, now that the six-wheeler has completed its long climb to the top.
NASA’s Perseverance Mars rover has crested the top of Jezero Crater’s rim at a location the science team calls “Lookout Hill” and rolling toward its first science stop after the monthslong climb. The rover made the ascent in order to explore a region of Mars unlike anywhere it has investigated before.
Taking about 3½ months and ascending 1,640 vertical feet (500 vertical meters), the rover climbed 20% grades, making stops along the way for science observations. Perseverance’s science team shared some of their work and future plans at a media briefing held Thursday, Dec. 12, in Washington at the American Geophysical Union’s annual meeting, the country’s largest gathering of Earth and space scientists.
“During the Jezero Crater rim climb, our rover drivers have done an amazing job negotiating some of the toughest terrain we’ve encountered since landing,” said Steven Lee, deputy project manager for Perseverance at NASA’s Jet Propulsion Laboratory in Southern California. “They developed innovative approaches to overcome these challenges — even tried driving backward to see if it would help — and the rover has come through it all like a champ. Perseverance is ‘go’ for everything the science team wants to throw at it during this next science campaign.”
A scan across a panorama captured by NASA’s Perseverance Mars rover shows the steepness of the terrain leading to the rim of Jezero Crater. The rover’s Mastcam-Z camera system took the images that make up this view on Dec. 5. NASA/JPL-Caltech/ASU/MSSS Since landing at Jezero in February 2021, Perseverance has completed four science campaigns: the “Crater Floor,” “Fan Front,” “Upper Fan,” and “Margin Unit.” The science team is calling Perseverance’s fifth campaign the “Northern Rim” because its route covers the northern part of the southwestern section of Jezero’s rim. Over the first year of the Northern Rim campaign, the rover is expected to visit as many as four sites of geologic interest, take several samples, and drive about 4 miles (6.4 kilometers).
“The Northern Rim campaign brings us completely new scientific riches as Perseverance roves into fundamentally new geology,” said Ken Farley, project scientist for Perseverance at Caltech in Pasadena. “It marks our transition from rocks that partially filled Jezero Crater when it was formed by a massive impact about 3.9 billion years ago to rocks from deep down inside Mars that were thrown upward to form the crater rim after impact.”
This animation shows the position of NASA’s Perseverance Mars rover as of Dec. 4, 2024, the 1,347th Martian day, or sol, of the mission, along with the proposed route of the mission’s fifth science campaign, dubbed Northern Rim, over the next several years. NASA/JPL-Caltech/ESA/University of Arizona “These rocks represent pieces of early Martian crust and are among the oldest rocks found anywhere in the solar system. Investigating them could help us understand what Mars — and our own planet — may have looked like in the beginning,” Farley added.
First Stop: ‘Witch Hazel Hill’
With Lookout Hill in its rearview mirror, Perseverance is headed to a scientifically significant rocky outcrop about 1,500 feet (450 meters) down the other side of the rim that the science team calls “Witch Hazel Hill.”
“The campaign starts off with a bang because Witch Hazel Hill represents over 330 feet of layered outcrop, where each layer is like a page in the book of Martian history. As we drive down the hill, we will be going back in time, investigating the ancient environments of Mars recorded in the crater rim,” said Candice Bedford, a Perseverance scientist from Purdue University in West Layfette, Indiana. “Then, after a steep descent, we take our first turns of the wheel away from the crater rim toward ‘Lac de Charmes,’ about 2 miles south.”
Lac de Charmes intrigues the science team because, being located on the plains beyond the rim, it is less likely to have been significantly affected by the formation of Jezero Crater.
After leaving Lac de Charmes, the rover will traverse about a mile (1.6 kilometers) back to the rim to investigate a stunning outcrop of large blocks known as megabreccia. These blocks may represent ancient bedrock broken up during the Isidis impact, a planet-altering event that likely excavated deep into the Martian crust as it created an impact basin some 745 miles (1,200 kilometers) wide, 3.9 billion years in the past.
More About Perseverance
A key objective of Perseverance’s mission on Mars is astrobiology, including caching samples that may contain signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, to help pave the way for human exploration of the Red Planet and as the first mission to collect and cache Martian rock and regolith.
NASA’s Mars Sample Return Program, in cooperation with ESA (European Space Agency), is designed to send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.
The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.
NASA’s Jet Propulsion Laboratory, which is managed for the agency by Caltech, built and manages operations of the Perseverance rover.
For more about Perseverance:
https://science.nasa.gov/mission/mars-2020-perseverance
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Last Updated Dec 12, 2024 Related Terms
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This artist’s concept shows interstellar object 1I/2017 U1 (‘Oumuamua) after its discovery in 2017. While itself not a dark comet, ‘Oumuamua’s motion through the solar system has helped researchers better understand the nature of the 14 dark comets discovered so far.European Southern Observatory / M. Kornmesser These celestial objects look like asteroids but act like comets now come in two flavors.
The first dark comet — a celestial object that looks like an asteroid but moves through space like a comet — was reported less than two years ago. Soon after, another six were found. In a new paper, researchers announce the discovery of seven more, doubling the number of known dark comets, and find that they fall into two distinct populations: larger ones that reside in the outer solar system and smaller ones in the inner solar system, with various other traits that set them apart.
The findings were published on Monday, Dec. 9, in the Proceedings of the National Academy of Sciences.
Scientists got their first inkling that dark comets exist when they noted in a March 2016 study that the trajectory of “asteroid” 2003 RM had moved ever so slightly from its expected orbit. That deviation couldn’t be explained by the typical accelerations of asteroids, like the small acceleration known as the Yarkovsky effect.
“When you see that kind of perturbation on a celestial object, it usually means it’s a comet, with volatile material outgassing from its surface giving it a little thrust,” said study coauthor Davide Farnocchia of NASA’s Jet Propulsion Laboratory in Southern California. “But try as we might, we couldn’t find any signs of a comet’s tail. It looked like any other asteroid — just a pinpoint of light. So, for a short while, we had this one weird celestial object that we couldn’t fully figure out.”
Weird Celestial Objects
Farnocchia and the astronomical community didn’t have to wait long for another piece of the puzzle. The next year, in 2017, a NASA-sponsored telescope discovered history’s first documented celestial object that originated outside our solar system. Not only did 1I/2017 U1 (‘Oumuamua) appear as a single point of light, like an asteroid, its trajectory changed as if it were outgassing volatile material from its surface, like a comet.
“‘Oumuamua was surprising in several ways,” said Farnocchia. “The fact that the first object we discovered from interstellar space exhibited similar behaviors to 2003 RM made 2003 RM even more intriguing.”
By 2023, researchers had identified seven solar system objects that looked like asteroids but acted like comets. That was enough for the astronomical community to bestow upon them their own celestial object category: “dark comets.” Now, with the finding of seven more of these objects, researchers could start on a new set of questions.
“We had a big enough number of dark comets that we could begin asking if there was anything that would differentiate them,” said Darryl Seligman, a postdoctoral fellow in the department of Physics at Michigan State University, East Lansing, and lead author of the new paper. “By analyzing the reflectivity,” or albedo, “and the orbits, we found that our solar system contains two different types of dark comets.”
Two Kinds of Dark Comets
The study’s authors found that one kind, which they call outer dark comets, have similar characteristics to Jupiter-family comets: They have highly eccentric (or elliptical) orbits and are on the larger side (hundreds of meters or more across).
The second group, inner dark comets, reside in the inner solar system (which includes Mercury, Venus, Earth, and Mars), travel in nearly circular orbits, and are on the smaller side (tens of meters or less).
Like so many astronomical discoveries, Seligman and Farnocchia’s research not only expands on our knowledge of dark comets, but it also raises several additional questions: Where did dark comets originate? What causes their anomalous acceleration? Could they contain ice?
“Dark comets are a new potential source for having delivered the materials to Earth that were necessary for the development of life,” said Seligman. “The more we can learn about them, the better we can understand their role in our planet’s origin.”
For more information about asteroids and comets, visit:
https://www.jpl.nasa.gov/topics/asteroids/
Small Body Research at JPL NASA Learns More About Interstellar Visitor 'Oumuamua Lesson: Comet on a Stick News Media Contacts
Ian J. O’Neill
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karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Dec 09, 2024 Related Terms
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NASA’s Swift Reaches 20th Anniversary in Improved Pointing Mode
After two decades in space, NASA’s Neil Gehrels Swift Observatory is performing better than ever thanks to a new operational strategy implemented earlier this year. The spacecraft has made great scientific strides in the years since scientists dreamed up a new way to explore gamma-ray bursts, the most powerful explosions in the universe.
“The idea for Swift was born during a meeting in a hotel basement in Estes Park, Colorado, in the middle of a conference,” said John Nousek, the Swift mission director at Pennsylvania State University in State College. “A bunch of astrophysicists got together to brainstorm a mission that could help us solve the problem of gamma-ray bursts, which were a very big mystery at the time.”
Watch to learn how NASA’s Neil Gehrels Swift Observatory got its name.
NASA’s Goddard Space Flight Center Gamma-ray bursts occur all over the sky without warning, with about one a day detected on average. Astronomers generally divide these bursts into two categories. Long bursts produce an initial pulse of gamma rays for two seconds or more and occur when the cores of massive stars collapse to form black holes. Short bursts last less than two seconds and are caused by the mergers of dense objects like neutron stars.
But in 1997, at the time of that basement meeting, the science community disagreed over the origin models for these events. Astronomers needed a satellite that could move quickly to locate them and move to point additional instruments at their positions.
What developed was Swift, which launched Nov. 20, 2004, from Complex 17A at what is now Cape Canaveral Space Force Station in Florida. Originally called the Swift Observatory for its ability to quickly point at cosmic events, the mission team renamed the spacecraft in 2018 after its first principal investigator Neil Gehrels.
Swift uses several methods for orienting and stabilizing itself in space to study gamma-ray bursts.
Sensors that detect the Sun’s location and the direction of Earth’s magnetic field provide the spacecraft with a general sense of its location. Then, a device called a star tracker looks at stars and tells the spacecraft how to maneuver to keep the observatory precisely pointed at the same position during long observations.
Swift uses three spinning gyroscopes, or gyros, to carry out those moves along three axes. The gyros were designed to align at right angles to each other, but once in orbit the mission team discovered they were slightly misaligned. The flight operations team developed a strategy where one of the gyros worked to correct the misalignment while the other two pointed Swift to achieve its science goals.
The team wanted to be ready in case one of the gyros failed, however, so in 2009 they developed a plan to operate Swift using just two.
Swift orbits above Earth in this artist’s concept. NASA’s Goddard Space Flight Center Conceptual Image Lab Any change to the way a telescope operates once in space carries risk, however. Since Swift was working well, the team sat on their plan for 15 years.
Then, in July 2023, one of Swift’s gyros began working improperly. Because the telescope couldn’t hold its pointing position accurately, observations got progressively blurrier until the gyro failed entirely in March 2024.
“Because we already had the shift to two gyros planned out, we were able to quickly and thoroughly test the procedure here on the ground before implementing it on the spacecraft,” said Mark Hilliard, Swift’s flight operations team lead at Omitron, Inc. and Penn State. “Actually, scientists have commented that the accuracy of Swift’s pointing is now better than it was since launch, which is really encouraging.”
For the last 20 years, Swift has contributed to groundbreaking results — not only for gamma-ray bursts but also for black holes, stars, comets, and other cosmic objects.
“After all this time, Swift remains a crucial part of NASA’s fleet,” said S. Bradley Cenko, Swift’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The satellite’s abilities have helped pioneer a new era of astrophysics called multimessenger astronomy, which is giving us a more well-rounded view of how the universe works. We’re looking forward to all Swift has left to teach us.”
Swift is a key part of NASA’s strategy to look for fleeting and unpredictable changes in the sky with a variety of telescopes that use different methods of studying the cosmos.
Goddard manages the Swift mission in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and Northrop Grumman Space Systems in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory in the United Kingdom, Brera Observatory in Italy, and the Italian Space Agency.
Download high-resolution images on NASA’s Scientific Visualization Studio
By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Claire Andreoli
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claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Nov 20, 2024 Editor Jeanette Kazmierczak Location Goddard Space Flight Center Related Terms
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