Mechanical Engineering Magazine

TECH BUZZ

NASA is dedicated to futuristic vehicles and missions, but the agency is also setting about to reinvent the wheel. The new “superelastic tire“ developed at NASA’s Glenn Research Center in Cleveland is built to thrive on inhospitable planets such as Mars, where the rocky terrain is hard to maneuver and temperatures can reach -130 °C.

But the real advantage of the new tire is its ability to carry heavy loads without suffering permanent damage. For lunar and planetary rovers that are intended to explore for months or years with no hope of getting spare parts, that is a real benefit.

Tire damage became a concern for NASA engineers in 2013 after they

NASA’S ALIEN
noticed significant wheel degradation
on Curiosity, the car-sized rover that
explored Gale Crater on Mars. “We
wanted to ensure any wheels sent to
Mars never got damaged again,” said
Santo Padula, a materials research
engineer at Glenn.

A team led by Colin Creager, a mechanical engineer at NASA, had been developing tire prototypes based on a steel spring design. These springs could carry heavy loads but faced limits on the force and deformation they could handle. Too much, and the wheels would fracture due to excessive stretching of bonds between atomic structures.

Instead of steel, Padula recommended
fashioning a wheel from a nickel-
titanium shape-memory alloy, which had
a unique deformation mechanism that
could snap a tire back into its original
shape in case of deformities. The alloy
is able to reshape itself due to a unique
deformation method—rather than
expanding the bonds of a crystal lattice,
it rearranges the atomic structure
to another crystal lattice form. That
means that if the solid element needs
to bend or deform when hurdling over
an obstacle like a rock, it would come
back to its original shape instead of
separating or fracturing.

After several years of trials, the team believes it has hit on the right formula for the alloy. The nickel-titanium alloy can take a 10 percent to 12 percent strain, while the earlier materials had only a 0.3 percent strain.