Exciting advances in space exploration are underway as NASA tests revolutionary shape memory alloy (SMA) spring tires designed to tackle the harsh terrain of Mars .
This innovative tire, developed at NASA Glenn in collaboration with Goodyear, can withstand extreme deformation and return to its original shape, unlike traditional metal.
Exploring Mars: The Challenge of Mobility
Mars has fascinated scientists and explorers for centuries. The fourth planet from the Sun, it resembles a vast red desert with rugged and challenging terrain. Despite numerous robotic missions to Mars, NASA has only explored about 1% of its surface. In preparation for future human and robotic missions, NASA recently conducted rovers testing on simulated Martian terrain. The test uses a groundbreaking shape memory alloy (SMA) spring tire technology developed at NASA’s Glenn Research Center in Cleveland in collaboration with Goodyear Tire & Rubber.
Rovers – mobile robots designed to explore planetary and lunar surfaces – require extremely durable tires to effectively navigate their environment. The rocky and rugged terrain of Mars poses significant mobility challenges, making robust and flexible tires essential for successful exploration. Shape memory alloy (SMA) spring tires offer a promising solution to these challenges.
What is a shape memory alloy?
Shape memory alloys are special metals that can return to their original shape after being bent, stretched, heated, or cooled. While NASA has been using this technology in various applications for decades, its use in rover tires is a relatively new and exciting development.
“We at Glenn are one of the world leaders in bringing the science and understanding of how to change alloy composition, how to change material processing, and how to model these systems so that we can control and stabilize the behavior so that they can actually be used in real-world applications,” said Dr. Santo Padula II, a materials research engineer at NASA Glenn.
Padula and his team had experimented with several SMA applications, but his epiphany about the tire application came from a chance encounter.
Chance encounters spark innovation
As he was leaving the meeting, Padula ran into Colin Creager, a mechanical engineer at NASA Glenn whom he hadn’t seen in years. Creager took the opportunity to tell him about the work he was doing at NASA Glenn’s Lunar Simulation Operations Laboratory (SLOPE), which can simulate lunar and Martian surfaces to help scientists test the performance of rovers. He took Padula to the lab, where Padula immediately noticed the spring-loaded tires. At the time, they were made of steel.
Padula noted, “As soon as I saw the tire, I said, do you have any problems with the plasticizing process?” Plasticizing is the process of irreversible deformation of metal and can lead to damage or failure of the component.
“Colin said to me, ‘That’s the one problem we can’t solve.’” Padula continued, “I said, I have your solution. I’m developing a new alloy that can solve this problem. And that’s how SMA tires started.”
Nickel-Titanium SMAs: The Game Changer
From there, Padula, Creager and their team collaborated to improve NASA’s existing spring tires using a breakthrough material: nickel-titanium SMA. This metal can resist deformation despite extreme stress, allowing the tire to return to its original shape even after a strong impact, something that conventional metal spring tires cannot do.
Since then, much research has been conducted, and in the fall of 2024, NASA Glenn teams traveled to Airbus Defense and Space in Stevenage, UK, to test NASA’s improved SMA spring tires. The test took place at the Airbus Mars Yard — an enclosed facility designed to simulate the harsh conditions of Martian terrain.
“We went out there with the team, brought our motion tracking system and did a variety of uphill and downhill tests,” Creager said. “We did a lot of cross-slope testing on rock and sand, focusing on understanding stability because it was something we had never tested before.”
Test results and performance details
During the test, the researchers watched the rover as its wheels rolled over rocks, noting how much the tire rim shifted, what damage there was, and how it slid downhill. The team expected some slippage and movement, but very little, and the test met all expectations. The researchers also collected detailed information about the tire’s stability, maneuverability, and ability to overcome rocks.
As NASA continues to develop systems for deep space exploration, the agency’s Human Surface Mobility and Extravehicular Activities program has asked Padula to further explore ways to improve SMA properties for future rover tires and other potential uses, including the lunar environment.
“My goal is to extend the capabilities of SMA at operating temperature to applications like tires and look at using these materials for environmental protection,” Padula said. “We need new materials for extreme environments that can absorb the energy of micrometeorite impacts that occur on the Moon to enable things like habitat structures for large numbers of astronauts and scientists working on the Moon and Mars.”
Spring tires made of shape-memory alloy are just the beginning, researchers say.
