On 18 February 2021, a new rover landed on Mars with a mission to search for signs of ancient microbial life. When that day arrived, Timken senior application engineer John Renaud ventured a fist-pump and a “Yes!” The bearings for the descent brake that lowers the rover to the surface were his design, after all.
But Renaud says designing those bearings two years ago was all in a day’s work. His boss, chief engineer for aerospace John Lowry, clarifies. “John is a bit of a specialist for spaceflight,” he says. Designing precision bearings for applications like the Mars rovers is part of the job.
The Curiosity rover used Timken bearings in its descent to the planet, as did the two rovers before it, Spirit and Opportunity. Curiosity also had Timken bearings in the center hub of its carousel system, as it rotated to position sample cups for gathering and analyzing rock, soil, and atmosphere. In addition, two ¼ inch (6.35 mm) Timken bearings run its tiny vacuum pump, which supports the rover’s analytical equipment.
The value of a ¼-inch bearing
When you think about it, Renaud has a point—all this Mars rover business isn’t too surprising. Any rotating mechanism requires bearings, whether it operates in space or on Earth. Timken has been making bearings for nearly 120 years, so it’s no surprise we have a few on Mars.
What might be surprising is just how much is riding on those bearings. “A bearing is not just a bearing,” says Renaud. “Very small variations, ten thousandths of an inch (2.5 micron) one way or the other could be the difference between the part working or failing,” he says.
And failure is not an option. When a part fails in space, there’s no one there to fix it, so the entire mission could be unsuccessful. In the case of Curiosity, $2.5 billion and eight years of planning and development could have come to a halt shortly after landing on the Red Planet.
Instead, it glided gently onto the Aeolis Palus plain on August 6, 2012, and has been roving around, sending back pictures and analysis for the past six years—well beyond its projected 23-month lifespan—and making history with its discoveries.
Space application challenges
As an application engineer, Renaud solves a wide variety of problems. National defense projects, satellites, sensors, and yacht gyros have all crossed his desk. Often, he sees only the environmental factors and the load conditions—the external forces that the bearing needs to hold up against. “We get acronyms or a program name, but sometimes the projects are classified,” he says. “What does it go into? We can’t tell you.”
When it comes to space applications, a number of factors come into play that may not be as critical in Earthbound projects. First of all, says Renaud, you have to take the extreme heat, vibration, and acceleration of the launch conditions into account.
Typically, Timken engineers run customer-provided load conditions through Syber, Timken’s proprietary modeling software, “which simulates how the bearing will react to the load inputs and looks at contact stresses and shaft deflections to determine if there’s going to be a problem,” he says.
Bearings in space applications often operate in a vacuum environment, which tends to dry things out. To address that problem, Curiosity bearings were designed with a special grease-and-oil mix lubricant solution. Out-gassing can also be a concern in space. “If we’re working with an unstable material, it could contaminate all the components inside a satellite, including instruments,” says Lowry.
Bearings in space also have to be incredibly precise, especially when you’re pointing and focusing on something from orbit. If a bearing isn’t running smoothly, it can affect the ability to position a satellite accurately, and could transmit vibration to the rest of the satellite. That could mean it can’t get a clear image, for starters.
“If you’ve ever tried to zoom your camera onto the stage at a concert, you know how impossible it is to hold your hand still, to get a clear picture at that distance,” says Lowry. “Imagine that from a distance of outer space. The transmission of vibration when you’re trying to point a satellite or focus an instrument to gather data is critical. The requirements can be extremely challenging from that perspective.”
A culture that values collaboration
Renaud has been with Timken for 11 years, starting as a product engineer after he graduated from UMass Lowell with a degree in mechanical engineering. Lowry is coming up on his 20-year anniversary, taking the Chief Engineer of Aerospace job in 2011 after a career in R&D and program management.
“Just before I moved to aerospace, I worked on wind energy bearings that are 10-12 feet (3 m – 3.7 m) in diameter,” Lowry says. “Here, some are as small as a ¼ inch (6.35 mm).”
Both enjoy the variety of projects they get to work on. “Every day is different,” says Renaud.
Working on billion-dollar space programs means accuracy takes center-stage, though. Attention to detail is critical, as well as a team culture that puts a premium on open communication.
What advice do they offer young engineers looking for their next space project? “Ask a lot of questions,” says Lowry. “Be a sponge.”
Today, he says, “some of the original expertise in the field has started to turn over, and a younger generation is assuming those roles. Customers might lean on us more heavily for our support.”
Renaud agrees. “Learn from your coworkers,” he says. “Those people who’ve been doing the job for years are your greatest resource.”
At the same time, the space industry is evolving quickly. “Satellites are getting smaller and cheaper,” says Renaud. “When a company is sending up a constellation of relatively inexpensive, small satellites, sometimes it’s acceptable if a few fail.” That’s something Renaud and the Timken team are not accustomed to.
“It’s a different world than previous space flight,” says Lowry. But he looks forward to the challenge. Timken’s expertise and collaborative model, combined with the new ideas and ways of thinking that the next generation brings to the table, will undoubtedly play a big role in meeting the demands of smaller, more agile space companies.