Returning to the Moon after five decades, and subsequently venturing to Mars, presents a significant technological challenge: reinventing the wheel for extraterrestrial environments.
The vast distances involved render a simple puncture a critical failure. “A flat tire is unacceptable,” emphasizes Florent Menegaux, CEO of Michelin.
The harsh Martian conditions are well-documented, as evidenced by the Curiosity rover. Within a year of its 2012 landing, its aluminum wheels showed substantial damage from punctures and tears.
The Artemis missions aim to return astronauts to the Moon, potentially by 2027, with later missions utilizing a lunar rover to explore the south pole, commencing with Artemis V in 2030.
These Artemis missions will significantly expand lunar exploration, exceeding the Apollo missions’ limited range of 25 miles (40km).
“The goal is to cover 10,000 kilometers in 10 years,” states Sylvain Barthet, head of Michelin’s lunar airless wheel program.
“We’re not talking about short missions; we’re discussing decades of operation,” adds Dr. Santo Padula, a NASA engineer at the John Glenn Research Centre.
A major hurdle is the extreme temperature fluctuations on the Moon, plunging to below -230°C at the poles—approaching absolute zero, where atomic motion ceases. This severely impacts tire performance.
“Without atomic motion, material deformation and recovery become extremely difficult,” explains Dr. Padula.
Tires must deform over obstacles and regain their shape for efficient rolling. Permanent deformation leads to power loss.
Furthermore, future rovers will carry heavier payloads, including “larger science platforms and mobile habitats,” increasing the demands on tire technology.
The challenge is even greater on Mars, with its double the lunar gravity. Apollo’s lunar rovers used zinc-coated piano wire, with a limited range of 21 miles.
Given the detrimental effects of extreme temperatures and cosmic rays on rubber, metal alloys and high-performance plastics are leading candidates for airless space tires.
“Metallic or carbon fiber-based materials are generally used,” notes Pietro Baglion, team leader of ESA’s Rosalind Franklin Mars rover mission.
Nitinol, a nickel-titanium alloy, shows great promise. “It’s a rubber-like metal with exceptional flexibility and shape memory,” says Earl Patrick Cole, CEO of The Smart Tire Company.
Dr. Padula hails nitinol as “revolutionary,” highlighting its energy absorption and release capabilities, potentially addressing heating and cooling needs.
However, Barthet at Michelin believes a high-performance plastic may be better suited for long-distance lunar travel.
Bridgestone’s biomimetic approach mimics camel footpads, using a felt-like material and flexible metal spokes to distribute weight and prevent sinking into lunar regolith.
Michelin and Bridgestone, alongside Venturi Astrolab, are presenting their tire technologies to NASA this month. A decision is expected later in the year.
Michelin tests its tires on volcanic terrain, while Bridgestone uses Japan’s Tottori Sand Dunes for simulations.
ESA explores the possibility of independent European rover development. The research has terrestrial applications.
Dr. Cole’s work on Mars rover tire technology is leading to commercial applications, including nickel-titanium bicycle tires this year.
Priced around $150, these durable tires are slated for motorbike applications in challenging terrains.
Ultimately, his ambition centers on contributing to humanity’s lunar return: “I want to tell my kids, ‘Look at the Moon—Daddy’s tires are up there!'”
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