The SMART Tire Company
Los Angeles, CA
www.smarttirecompany.com

Shape memory alloy (SMA) tires will empower the next generation of Mars rovers and other extraterrestrial vehicles to carry heavier loads over longer distances. Since the original Apollo missions, aluminum and steel tires have taken a beating from the terrain. Starting in 2026 with the Fetch rover using advanced materials like SMA, tire problems will be a thing of the past on NASA missions.

The SuperElastic Tire was originally developed by NASA for Moon and Mars Rover missions. Past rovers used thin aluminum tires that eventually developed cracks and holes due to the tough Mars terrain. While the Perseverance Mars rover’s aluminum tires are a bit stronger than previous rovers, future tires made from shape memory alloys will enable larger, longer lasting rovers that will no longer need six wheels, but only four.

The SuperElastic Tire — a NASA Glenn innovation — comprises a non-pneumatic, compliant tire utilizing SMAs (mainly NiTinol and derivatives) as load-bearing components. These SMAs are capable of undergoing phase transitions at the molecular level with significant reversible strain (an order of magnitude more than ordinary materials) before undergoing permanent deformation. Commonly used elastic-plastic materials, such as spring steels and composites, can only be subjected to strains on the order of ~0.3 to 0.5% before suffering plastic deformation.

The utilization of shape memory alloys provides enhanced control over the effective stiffness as a function of the deformation, providing increased design versatility. The tire can be made to soften with increased deflection, reducing the amount of energy transferred to the vehicle during high-deformation events. In addition, the use of SMAs in the form of radial stiffeners, as opposed to springs, provides even more load-carrying potential and improved design flexibility.

The SMART Tire Company is developing the first consumer application of NASA’s SMA tire technology. Shape Memory Alloy Radial Technology (SMART) superelastic tires are airless, durable, and will never go flat. The tire is made from NiTinol+, a shape memory alloy that’s elastic like rubber, yet strong like titanium.

This SMART Tire was born out of the extreme challenges NASA faces on Mars, where there are no roads, temperatures can reach -200 °C, and tire performance is mission-critical. The SMART Tire has a patented load-bearing design that takes advantage of the unique properties of SMAs. These special metals can expand, contract, bend, or unbend at a very rapid rate (like rubber) and with so much force that it can move heavy objects. Even with extreme deformation, the tire regains 100% of its shape through phase transitions at the molecular level.

The first commercial product based on the NASA SuperElastic Tire is an eco-friendly pneumatic bicycle tire called METL , an airless, lighter-weight tire for commuter, road, gravel, and eBikes. The final product will be coated/encased in a new, formulated poly-rubber material. The tire will last the life of the bicycle with no leaks, tears, punctures, or sealants.

SMART Tire Company has been developing shape memory alloy tires for traditional bicycles and is conducting R&D for e-scooters at Spin, a subsidiary of Ford Motor Co. The airless solution could minimize environmental impacts of traditional rubber tires.

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Tech Briefs Magazine

This article first appeared in the June, 2021 issue of Tech Briefs Magazine.

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