Flat tires and AAA roadside assistance may soon be past memories. NASA Glenn Research engineers have just unveiled a new super-elastic tire constructed from nickel titanium, a shape memory alloy able to flex, conform, and then return to its original shape even after traversing the most punishing of terrains. While this latest invention is part of a larger, half-century-long effort to build a better tire for extra-planetary exploration, NASA engineers and materials scientists note they’ve already been testing a spinoff version for cars and trucks on Earth.
The design of NASA’s new tire takes cues from those used for the 1971 Lunar Rover, which was brought to the moon by Apollo 15. Unlike the common pneumatic tire propping up our electric cars, the Lunar Rover’s wheels used flexible wire mesh. Like rubber tires, the wheels could absorb shocks, but the mesh allowed them to “float” over the soft lunar soil (rather than sink into) and it also prevented over-deflection.
The Lunar Rover design was considered a major success and engineers used it as a model for future wheels that would later carry heavier loads. The tire is actually the basis for the award-winning Spring Tire, “an airless compliant tire that consists of several hundred coiled steel wires woven into a flexible mesh, giving the tires the ability to support high loads while also conforming to the terrain,” writes NASA.
Notably, the headline-making Mars Curiosity Rover, which touched down in 2012, uses aluminum wheels. The choice to use aluminum wheels was based on previous missions which forwent mesh tires without much issue. However, given the size and weight of the Curiosity (roughly that of a 4×4) mixed with the rough terrain, the soft metal alloy wheels began showing loose treads and holes after just a year. Not ideal for a vehicle that cost 2.5 billion USD to build.
In anticipation of the Mars 2020 launch, engineers and researchers are revisiting the Spring tire, but juicing it up for the red planet. The new tire improves on traction in soft sand, durability, and a reduced overall weight through the use of nickel titanium. The nickel titanium also gives the tires elasticity, as the metal’s shape memory alloys can rearrange at an atomic level to mold to rocks and bumps and then effortlessly snap its original shape. Indeed, tests conducted on simulated Martian terrain showed that the tires returned to form even when warped to the axle. The original Spring tire made of steel wire mesh stretched and deformed under the same conditions over time.
The hope is that the new tires will allow rovers to explore greater regions of Mars or the moon for longer periods, carry heavier payloads, and eventually be used on manned exploration vehicles that would move at much higher speeds.
On Earth, the tires would mean far less maintenance, no more flats, and a lot less landfill waste. Rubber tires deemed irreparable are ecologically problematic as they are durable, non-biodegradables that contain high levels of heavy metals and other pollutants.
Images via NASA