Space

Curiosity's wheels are breaking down as the mileage adds up

Curiosity's wheels are breakin...
Two of the raised treads, called grousers, on the left middle wheel of NASA's Curiosity Mars rover broke during the first quarter of 2017
Two of the raised treads, called grousers, on the left middle wheel of NASA's Curiosity Mars rover broke during the first quarter of 2017
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Two of the raised treads, called grousers, on the left middle wheel of NASA's Curiosity Mars rover broke during the first quarter of 2017
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Two of the raised treads, called grousers, on the left middle wheel of NASA's Curiosity Mars rover broke during the first quarter of 2017
A Curiosity wheel on display at the 2015 DARPA Robotics Challenge
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A Curiosity wheel on display at the 2015 DARPA Robotics Challenge
A comparison of the Curiosity wheel with those of two other NASA Mars rovers at the 2015 DARPA Robotics Challenge
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A comparison of the Curiosity wheel with those of two other NASA Mars rovers at the 2015 DARPA Robotics Challenge

NASA's Curiosity rover has been driving across Mars for over four-and-a-half years without an overhaul and it's starting to show. According to the space agency, the six aluminum wheels that support the unmanned explorer are starting to show significant signs of wear, with two new small breaks in the metal treads of the left-side middle wheel. However, it's expected the wheels will go the distance to allow the rover to complete its planned mission.

The wheels on the Curiosity are the largest ever to roll on the sands of the Red Planet. Built by Tapemation in California, the aluminum wheels are 20 in (50 cm) in diameter and 16 in (40 cm) across, with 19 zigzag treads, called grousers, projecting out about a quarter inch to provide traction. Inside the wheels, there are curving titanium spokes for support.

So far, Curiosity has traversed almost 10 mi (16 km) and the damage to the wheels and treads was noticed during a routine check on March 19 – the first check since January when the breaks hadn't appeared. Previous dents and holes in the soft metal wheels were seen in 2013 and NASA became concerned because the wear was occurring faster than had been anticipated. Tests have indicated that when three treads on a wheel have broken, it has reached 60 percent of its service life.

A comparison of the Curiosity wheel with those of two other NASA Mars rovers at the 2015 DARPA Robotics Challenge
A comparison of the Curiosity wheel with those of two other NASA Mars rovers at the 2015 DARPA Robotics Challenge

NASA says that Curiosity is exploring the sand dunes of the Murray formation on the slopes of Mount Sharp as it climbs higher in search of younger geological formations to find signs of climate change billions of years ago. The rover has traveled 9.9 mi (16 km) since landing in August 2012 and needs to cover another 3.7 mi (6 km) to reach its final destination. To help it achieve this, mission control is choosing routes that avoid as many sharp rocks as possible.

"All six wheels have more than enough working lifespan remaining to get the vehicle to all destinations planned for the mission," says Curiosity Project Manager Jim Erickson at NASA's Jet Propulsion Laboratory, Pasadena, California. "While not unexpected, this damage is the first sign that the left middle wheel is nearing a wheel-wear milestone."

Source: NASA

9 comments
Bob Stuart
NASA is deathly afraid of flat tires, but seems ignorant of the recent history of wheels. Farm tractors used to have huge steel wheels, but when rubber tires came in, the horsepower kept going up despite a much smaller OD on the newly compliant surface. They don't seem to have a single off-road car nut on staff to give advice.
DickKennedy
I would like to know the cost of one wheel , I have four rubber tires as well as four metal rims with around 250.00 per wheel including the rims and I already have well over 50,000 miles on them , I would like to put my tires against yours in a test in our hottest desert on Earth and see if mine will last longer ( a trump least say 20 miles ) and if mine hold up longer that yours I would like to talk to the person who made out the purchase order on your tires . 🍀 Ten miles ? Ten miles ? I'm almost positive Foose or West Coast Custom could have done better .
Leonidas
Here are some potential answers to your question, Bob: http://space.stackexchange.com/questions/3187/curiosity-why-did-they-reinvent-the-wheel-instead-of-using-pressure-tires It sounds like it really may have to do with the temperatures on Mars, not that NASA ignored earth tire advancements.
Madlyb
About the only place on Earth that comes close to the environment on Mars is probably Ojos del Salado when you factor in Temps, Atmospheric Pressure, and UV and then remember that every gram of weight that goes to wheels, takes away from actual tooling. So, everyone in this thread Armchair quarterbacking should better understand the challenges the team at NASA overcame before making snarky comments.
DavidIngram
If they had jbought the AAA Plus or Road Hazzard coverage we wouldn't have to worry about this.
Douglas Bennett Rogers
The delivery cost is almost the entire cost of the wheels. They require a high probability of lasting through the mission. The money is spent on getting the mass low to save on the delivery cost.
chase
FYI posters, Average temp on Mars is suppose to be 70F during the day near the equator. It's the cold not the heat. Which can plummet to around minus 100F at night. According to a few sources. Still... 10 miles ain't squat. Not at the cost of the Rover. Not with all the R&D and time spent developing it. Especially not for where it was designed to go. And years of planning and testing. They didn't overcome squat... in my opinion, with all that was put into it. They fell horribly short.
Nik
Aluminium? That would seem to be a poor choice. Why not titanium? Its tougher, and the weight difference could be offset by using less of it. The extra cost wouldn't be a significant factor, given the overall cost of the mission.
Gaëtan Mahon
Maybe for the next mission have some spares with you? Stop laughing! They could have had spares integrated into the tire itself in the form of a second, smaller set inside the first one. Once unusable have 5 of the 6 tires turn 90° for a crab like sideways motion, unlock the broken outer tire, start moving sideways to scuttle the outer one while the inner one emerges as a brand new one. Finish procedure while realigning the 5 other tires and applying the necessary settings required for the size difference of the smaller one.