Michelin showing lunar wheel prototype at Le Mans 24 Hours 2024

Michelin is revealing the airless lunar wheel prototype it has produced to meet the tender brief NASA’s Artemis programme at Le Mans 24 Hours 2024 . The objective of NASA’s Artemis programme is to explore the Moon’s south pole, where no human has ever been, in order to acquire scientific data and search for water in the form of ice.

The prototype photo looks like the latest incarnation of the tweel. But so far we know most about the brief, which is about as demanding as they come. The airless wheel for the Artemis rover will need to operate on the Moon for a decade, carry two astronauts, explore remote areas and take samples.
If that wasn’t enough, the details of this extreme mission reveal how high the bar is:

Gravity is one-sixth of that on Earth. It is hard climbing sandy slopes on Earth, but it’s harder on the Moon where the rover will face inclines of up to 20 degrees on loose, virgin ground. According to Michelin, this calls for “specific, durable wheels that provide grip on a wide spectrum surface types, aided by having the biggest contact patch possible in the same way that we wear albeit less flexible snowshoes to spread our weight when walking on snow.”

The Moon’s surface is not protected by an atmosphere. As a result, UV levels are much higher and therefore materials age faster. Furthermore, the rover’s wheels will be in permanent contact with the ground and subject to the effects of the sun and UV light.

According to Michelin, “it is vital to address [these points] through in-depth work on materials and their tribologic properties (frictional interaction), as well a thorough understanding of what it takes to function in such a hostile environment.”

Between manned missions, this vehicle will be expected to travel to the different landing points by its own means and function independently, a huge leap in comparison with NASA’s Apollo work over the period 1961 to 1972. Since the rover will spend much of its time in the shade and so won’t be able to recharge its batteries often via its solar panels, Michelin has to minimise energy needs in order to preserve the vehicle’s autonomy. In other words, the lower rolling resistance, the better.

Abrasion is another challenge. Sand at the Moon’s southern pole has been subject to very little erosion, which means it can be very aggressive and abrasive to surfaces that it comes into contact with it. To function reliably over 10,000km/10 years, and in addition to its all-terrain capabilities on sand, rocks and craters, the vehicle’s wheels will need to be made of particularly resilient materials.

Scientists hope to find water in the form of ice in temperatures that can fall to almost -250°C, but which climb to +100°C in places. Therefore only exceptional materials will be able to survive and perform.

Although samples of lunar rock have been brought back from previous missions, scientific publications are the chief source of reference for Michelin’s research experts. This is how they realised that France’s volcanic Auvergne region – not far from the firm’s Clermont-Ferrand’s headquarters in the Massif Central – bears certain similarities with lunar soil, making it ideal for testing purposes.

Motorsport tyres are not immediately comparable with lunar tyres. But over the years, Michelin’s grasp of materials has produced a long list of longevity-related records at race-tracks around the world. Since 2011, for example, Michelin tyres for endurance racing’s premier class have successfully covered more than 700 kilometres at the Le Mans 24 Hours while posting near-consistent lap-times. That’s equivalent to the distance of more than two Formula 1 grands prix. At the same time, Michelin has halved the number of tyres actually consumed in the race compared with the early 2000s.

“For 135 missions from 1995 until 2007, NASA entrusted Michelin with the design and production of the tyres for its space shuttle,” said Christophe Moriceau, Michelin’s Director of Advanced Research. “We have since carried out research for a variety of lunar vehicles and, in 2021, began a new collaboration with the Intuitive Machines design team and its partners: Northrop Grumman, Boeing, and AVL to develop wheels for the Artemis lunar rover. This is how we became involved in the programme after responding to a call for tenders launched by NASA.”