Load Testing of a Superelastic Tire Suited for Space Exploration

NASA’s Superelastic tire for Mars rovers was proposed to replace previous aluminum tires after the rough Martian terrain damaged Curiosity’s aluminum wheels within a year of use.1 A superelastic material is a smart material with the capability to deform under high stress and revert back to its original shape.2 Incorporating these materials as load bearing components in the rover tire enhances their ability to endure excessive deformation without sustaining permanent damage, making superelastic material ideal for the challenges of Martian regolith.2 By replicating this technology on a smaller scale, the mechanical properties of superelastic materials can be characterized and its effectiveness in different applications can be analyzed, such as its load carrying capability and shock absorption. Recent research and testing suggests that a ¼” coil diameter of superelastic Nitinol wire is a valuable baseline parameter that increases structural stiffness while maintaining a suitable tire footprint.3 After undergoing proper shape-setting processes to ensure uniform superelasticity, the springs were woven together to manufacture a full superelastic 8-inch tire prototype. Load testing was conducted to investigate how varying the circumferential tension and applying varying loads impacts the tire’s footprint. Reducing circumferential tension resulted in a wider tire footprint and thus increased the contact area of the tire with the ground. With a greater surface area of the tire in contact with the ground, the load is more evenly distributed, reducing the stress experienced on the superelastic material. This stress reduction increased the tire’s load-carrying capacity, improving the overall performance and durability of the tire. These experimental results compared to existing test results and models allow for expanded empirical characterization of the superelastic Nitinol material and can be used to increase the performance, versatility, and durability of Mars rover tires. References 1Premature Wear of the MSL Wheels (2017) NASA. Available at: https://llis.nasa.gov/lesson/22401 (Accessed: 21 August 2024). 2S. Padula II, J. Benzing, and V. M. Asnani. Superelastic Tire. U.S. Patent 10,449,804 B1, Oct. 22, 2019. https://science.nasa.gov/mission/msl-curiosity/ 3Veritasium. "How NASA Reinvented the Wheel," YouTube, April 29, 2023. Available: www.youtube.com/watch?v=vSNtifE0Z2Q.