While Mr. Creager said the team found structural ways to adjust the tires and push the limits, it wasn't the answer they were looking for. Then one day, Mr. Creager ran into an old colleague, Santo Padula.
"It just happened by chance, really," Mr. Creager said.
Mr. Padula, a NASA materials scientist, was interested in seeing the team's lab and work.
"I showed it to him, and his eyes lit up," Mr. Creager said.
Mr. Padula was working with shape-memory alloys.
"I looked at (the tires) and said, 'aren't you having a problem with plastic deformation in this?'" Mr. Padula recalled in a nasa.gov video. "… He said, 'Yeah,' and I said, 'I have your solution.'"
Mr. Creager said, as mechanical engineers, they were looking at structural ways to increase the load, but changing the material wasn't something they had considered.
"This particular material doesn't deform like conventional material, where in those materials, when we put stress on them, we basically are stretching the bonds between the atomic structure," Mr. Padula said.
"This material has a unique characteristic that allows it to do an atomic rearrangement to accommodate deformation."
The nickel titanium alloy allowed the SMA Spring Tire to deform — and return to shape — 20% to 30% more than the previous version.
"We could actually deform this all the way down to the axle and have it return to shape," Mr. Creager said.