By Warren Miller, contributing writer
You’ve probably heard the old metaphor about the impossibility of reinventing the wheel, but NASA found themselves in the position of having to do just that — literally reinventing the wheels on their Mars rover to withstand the planet’s harsh terrain. The space agency’s engineers did so by devising a wheel made of a woven nickel-titanium alloy that “remembers” its optimal shape and springs back to it after being dented or misshapen by rocks on the surface of Mars. The team hopes that this new wheel will be the next step in planetary exploration, and perhaps it may change the way that tires on Earth are constructed, too.
NASA faced a similar conundrum in the 1960s during the Apollo landing missions — how to create wheels that could traverse tough terrains over long periods of time. The mesh wheels that they came up with performed admirably on the lunar surface, but Mars presented a different set of challenges. The terrain is more uneven, and the wild swings in temperature make anything filled with air unable to function. Long-term viability was also a necessity as solar and nuclear energy will power the rovers for over 10 years as they’re still mobile. Another factor to consider was weight: NASA spends approximately $30,000 per pound of material that it lands on Mars, so the lighter the weight, the lower the cost.
The woven mesh metal wheels they developed at the NASA Glenn Research Center in Cleveland, Ohio, are capable of bearing almost 10 times as much weight as the Mars Curiosity rover’s current wheels, as well as being capable of ascending grades up to 23% steeper. They can also function in temperatures ranging from −202°F to 194° F and have better traction on small rocks and sand. “We can actually deform this all the way down to the axle and have it return to shape, which we could never even contemplate in a conventional-metal system,” said Santo Padula, a materials scientist on the project, in a video released by NASA.
The woven mesh metal wheels are capable of bearing almost 10 times as much weight as the Mars Curiosity rover’s current wheels. Image source: NASA.
The new wheel has passed all of its tests to date, even managing to traverse 10 kilometers over simulated surface conditions — more than half the total distance covered by the Mars Curiosity rover on the planet’s surface so far — without any significant deterioration. There’s still a lot more testing left to do, however — it can be difficult to simulate the wild temperature fluctuations on the surface of Mars. The new wheel design probably won’t be adequately tested in time for the planned launch of the Mars 2020 rover, but it could be ready for the subsequent return mission in 2024.
The implications of this new technology on our exploration of other planets is obvious, but what about right here on Earth? The Glenn Research team is already collaborating with Goodyear on a similar design for terrestrial automobile tires. Colin Creager, an engineer on the team, sees potential applications in the commercial sector. “I could definitely see it being used for any application where you’re driving off-road, and the risk of a puncture and a flat is a big deal, like with a military vehicle,” he said. “But I would love to see this technology branching off to passenger vehicles.”
Popular culture has always imagined the possibility of flying cars doing away with the need for a spare tire and a jack in the trunk, but maybe woven metal wheels will save us from having to call AAA first.
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