CLEVELAND — When it comes to designing tires for worlds other than earth, forget elongation and rebound and instead think "stoichiometric" and "shape memory alloys."
Scientists at NASA's Glenn Research Center near Cleveland have developed a non-pneumatic, compliant tire made of a stoichiometric nickel-titanium mesh that they envision will be used on a possible mission to Mars.
Stoichiometry is defined a branch of chemistry that deals with the application of the laws of definite proportions and of the conservation of mass and energy to chemical activity.
The innovation, called the Superelastic Tire, is the latest evolution of the "spring tire" that NASA Glenn and Goodyear developed a few years back, inspired by the Apollo program's lunar-rover tires.
The latest version uses "shape memory alloys" capable of undergoing high strain as load-bearing components, instead of typical elastic materials, NASA Glenn said. This results in a tire that can withstand excessive deformation without permanent damage.
Using shape memory alloy as radial stiffening elements can also increase the tire's load-carrying capacity without a weight increase, NASA Glenn said.
The nickel-titanium alloy undergoes an atomic rearrangement to accommodate deformation, according to Santo Padula, a materials scientists at NASA Glenn. This allows a tire made of the alloy to deform up to 30 times more than one made of a more conventional material and recover its original shape without irreversible "plastic deformation."