NASA and The Goodyear Tire & Rubber Company have developed an airless tire to transport large, long-range vehicles across the surface of the moon.
The new “Spring Tire” with 800 load bearing springs is designed to carry much heavier vehicles over much greater distances than the wire mesh tire previously used on the Apollo Lunar Roving Vehicle (LRV). The new tire will allow for broader exploration and the eventual development and maintenance of a lunar outpost.
According to Vivake Asnani, NASA’s principal investigator at the Glenn Research Center in Cleveland, this was a significant change in requirements that required innovation. “With the combined requirements of increased load and life, we needed to make a fundamental change to the original moon tire,” he said. “What the Goodyear-NASA team developed is an innovative, yet simple network of interwoven springs that does the job. The tire design seems almost obvious in retrospect, as most good inventions do.”
The Spring Tire was installed on NASA’s Lunar Electric Rover test vehicle and put through its paces at the Johnson Space Center’s “Rock Yard” in Houston where it performed successfully.
“This tire is extremely durable and extremely energy efficient,” noted Jim Benzing, Goodyear’s lead innovator on the project. “The spring design contours to the surface on which it’s driven to provide traction. But all of the energy used to deform the tire is returned when the springs rebound. It doesn’t generate heat like a normal tire.”
According to Goodyear engineers, development of the original Apollo lunar mission tires, and the new Spring Tire were driven by the fact that traditional rubber, pneumatic (air-filled) tires used on Earth have little utility on the moon. This is because rubber properties vary significantly between the extreme cold and hot temperatures experienced in the shaded and directly sunlit areas of the moon. Furthermore, unfiltered solar radiation degrades rubber, and pneumatic tires pose an unacceptable risk of deflation.
According to Asnani, the Spring Tire does not have a “single point failure mode. What that means,” he said, “is that a hard impact that might cause a pneumatic tire to puncture and deflate would only damage one of the 800 load bearing springs. Along with having this ultra-redundant characteristic, the tire has a combination of overall stiffness yet flexibility that allows off-road vehicles to travel fast over rough terrain with relatively little motion being transferred to the vehicle.”
NASA has been so impressed with the tire that it decided to highlight the project during NASA’s recent “Day on the Hill” exhibit at the Rayburn House Office Building in Washington, DC. “I spoke with 10 to 15 members of Congress and about sixty staffers,” noted NASA’s Asnani. “Virtually everyone I spoke with was blown away by the idea that this technology may one day be used, not only for extraterrestrial vehicles, but also, perhaps, for vehicles here on Earth.”