29-04-2025
Michelin's Space-Spec Wheels Can Conquer Moon Craters in Extreme Temps
Michelin has developed what looks like a tire but is actually a wheel that's capable of surviving the moon's harsh environment.
The wild-looking wheels, which can withstand extreme temperatures and conquer craters, will be used on a lunar rover.
We spoke with Michelin's Cyrille Roget, who detailed the development process of the brand's unusual moon-spec wheels.
Picture a moon rover. You might imagine the very first one launched in 1971. Or maybe the one Matt Damon's character piloted in The Martian. But America's newest space vehicle is probably going to look much different. That includes the tires, which Cyrille Roget, Michelin's scientific and innovation communication director, says isn't a tire anymore—it's a wheel. It's round, but there is no air pressure, and it's made entirely of thermoplastic.
The demand is rigorous. The rover will reside on Earth's moon for a decade, exploring remote areas and taking samples on manned and unmanned missions. Each wheel had to be tested in extreme environments to ensure it could tough it out in temperatures above 212 degrees Fahrenheit and below -400 degrees Fahrenheit, stay intact even in the path of solar and galactic radiation, and maintain traction on very loose soil. The moon, in other words, is not a friendly place. A moon rover's wheels must be equally fierce.
Why bother with a project that has a high cool factor but is also extremely expensive? Michelin believes that its work will lead to technical and scientific advances that could lead to creative tire and wheel ideas here on Earth.
Last year, NASA announced it had selected three finalists to design the newest lunar rover: Lunar Outpost, Venturi Astrolab, and Intuitive Machines. The latter, a Houston, Texas-based aerospace company, picked Michelin, AVL, Boeing, and Northrop Grumman Corporation as its dance partners, and NASA ponied up $30 million for the team to complete a Lunar Terrain Vehicle services feasibility assessment. In simpler terms, it's a show-and-tell report.
As Roget and his team considered how they would contribute to the rolling power of the lunar terrain vehicle, they considered what they already knew about tires.
'Of course, the first thing we thought about was rubber, because we have 130 years of experience with rubber,' Roget says. 'But the problem on the lunar surface is that we need something that is strong and robust, because there is a lot of abrasion.'
Factoring in the radiation, abrasion, and abrupt temperature changes between the bottom of the crater and the surface of the moon, rubber wasn't going to cut it. (Michiganders, in particular, will get this.) Michelin already knew from years of practice that rubber turns into a hard surface at -240 degrees. Instead, the company created a wheel composed of flexible thermoplastic S-shaped 'spokes' that connect the wheel to the outside 'tread' that makes contact with the soil.
The rovers cannot carry a spare wheel, either, so the original set has to be darn near perfect. That's where the spokes come in; even if one little spoke breaks, the wheel will still continue to function. It's not a catastrophic failure, as it might be if a tire is punctured. The mission won't be lost even if the wheels lose a few spokes.
The wheels are very soft and very flexible, Roget explains. They have to lose as little energy as possible while moving on the surface. In the laboratory, Roget says, they developed a means of testing thermoplastic at extreme temperatures to see if it's still flexible.
Gravity is also a factor, as the moon's gravity is one-sixth of what it is on Earth. The rover has to climb out of sandy craters with inclines of 20 degrees or more, so the contact patch for the space-spec wheels has to be as large as possible.
'A lot of people just focus on the fact that [the product] is going to the moon,' Roget says. 'For us, it's always about learning something.'
If you think about it, Roget points out, a tire is a composite, an assembly of materials that are not supposed to work together. Metal wheels, for instance, are rigid, and they're wrapped in soft rubber. When you combine these elements together, it creates something that works for millions of cycles. That's exactly what Michelin scientists want to learn on the lunar project: how wheels work in the harshest conditions they can find. The moon will be its own kind of laboratory for Michelin to test its theories of what is possible for its unusual wheels to achieve.
'We have a team of people that are very motivated and very passionate about what they're doing, because it's not every day that you work on a project that will go to the moon,' Roget says. 'We're also exploring solutions that we are developing for a lunar application, but also that we think could find a way to solutions that will be on Earth.'
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