Tires like the ones we use on Earth — made from rubber and filled with air — won’t work on the moon for a few reasons.
First, enormous temperature swings from up to 260 degrees Fahrenheit in the daytime down to -280 degrees at night makes an air-filled tire impossible. Air expands and contracts as temperature changes, so keeping an air-filled tire from going flat at night or exploding during the day would be extremely difficult.
Second, the moon is bathed in intense radiation that degrades rubber because there is no atmosphere.
Nevermind the fact that changing a flat tire on the moon wouldn’t be easy in stiff spacesuit gloves.
The challenges are even greater this time than they were 50 years ago, though. The original Lunar Rovers were, essentially, disposable. They were designed to work for a short time then, as planned, they were abandoned. The new Rovers — which are electric, like the originals, since internal combustion engines also wouldn’t work on the airless moon — can be recharged over and over so they can keep working for years.
Plans call for them to also operate autonomously so they could be up there driving around and doing things even when people aren’t around. This also means the rovers will be exposed to more extreme temperature changes for longer periods. A moon day and a moon night can be two weeks long, each. And, each sunrise and sunset, temperatures change from extreme hot to extreme cold almost instantly.
The partner companies are talking about allowing private firms, organizations, and international agencies, not just NASA, to use them for projects on the moon. Given the longer operational life expected from these new tires — and the fact that it’ll be a very long wait for “roadside assistance” on the moon — Goodyear is exploring new technologies.
“It’s more like an open weave or mesh with different types of three-dimensional features,” said Michael Rachita, senior program manager for non-pneumatic tires at Goodyear.
The tires will need to use special metal alloys to withstand the extreme temperature changes while still retaining flexibility and strength. Recreating the extreme cold of a lunar night is especially challenging on Earth because, at those temperatures, air would become a liquid. Tests must be done in a vacuum, said Kirk Shireman, Lockheed’s vice president for lunar exploration.
The moon’s surface is covered in fine super-abrasive sand. Because there’s no air or wind on the moon, the sand particles don’t get moved around and worn smooth, so each particle has sharp points. There are companies that make artificial moon dust based on samples brought back by the 1960s and ’70s Apollo missions, said Rachita, so Goodyear’s researchers are using that to test different tread patterns.
It can be glued to paper or board to make “moon sandpaper” to test abrasion resistance, he said.