How Wheel Damage Affects Mars Rover Curiosity’s Mission

Jul 22, 2014

By Leonard David

 

If there were mechanics on Mars, NASA may have taken the Curiosity rover into the shop by now.

The 1-ton robot has accumulated quite a bit of wheel damage since touching down inside Gale Crater in August 2012 to investigate Mars’ past and present potential to host microbial life.

“They are taking damage. That’s the surprise we got back at the end of last year,” said Jim Erickson, Curiosity project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “We always expected we would get some holes in the wheels as we drove. It’s just the magnitude of what we’re seeing that was the surprise.”

But the damage has not imperiled the rover’s mission, said Curiosity’s handlers, who are employing a number of troubleshooting measures to keep the robot rolling along. They’re confident Curiosity can still reach and explore its ultimate science destination: the foothills of the 3.4-mile-high (5.5 kilometers) Mount Sharp.

Bumps and bruises

Each of Curiosity’s six aluminum wheels is independently actuated and geared, built for climbing in soft sand and rolling over rocks. However, engineers eyeing rover-snapped imagery have been taken aback by the amount of wear and tear on the wheels.

This damage comes in several forms. For example, there are punctures in the wheel skin between what are called “grousers” — traction bars that take on the form of a zigzag pattern on the wheels. Grousers help improve wheel performance and provide a better grip on the Martian terrain, rover team members said.

“We are getting punctures through there. After a while, those punctures can begin getting cracks from the puncture in different directions,” Erickson told Space.com. The entire skin between two grousers could get punched out if there are enough cracks on both sides, he added.

The damage isn’t identical from wheel to wheel. The two front wheels have worn differently than the two middle wheels, Erickson said.

Troublesome caprock

It turns out that the tough-as-nails culprit playing havoc with Curiosity’s wheels is “caprock,” which is quite resistant to weathering and erosion.

“To the extent possible, we’re trying to avoid that particular kind of rock,” Erickson said. “Overall, we’re learning how to pick our poison … how to get to the right paths that are going to minimize — I repeat, minimize, not eliminate — the damage we’re going to get to the wheels. We have never encountered this kind of hard, embedded rock on Mars before.”

Lessons learned from the Curiosity wheel anxiety are expected to influence the design of NASA’s next Mars rover, which is scheduled to launch in 2020.

Choosing a path forward

Erickson told Space.com that the mission team is carefully picking Curiosity’s path forward, aided by images snapped by NASA’s sharp-eyed Mars Reconnaissance Orbiter.

“We’re looking for places that have a thin covering of sand,” he said. “If we have to drive on rock, we’re looking for areas that have softer rock types than what we’ve seen.”

This process has motivated the rover team to get better acquainted with the Martian landscape.

5 comments on “How Wheel Damage Affects Mars Rover Curiosity’s Mission

  • NASA had wheel problems with the earlier “Spirit” Rover.

    http://en.wikipedia.org/wiki/Spirit_%28rover%29

    On sol 2116 December 17, 2009, the right-front wheel suddenly began to operate normally for the first three out of four rotations attempts. It was unknown what effect it would have on freeing the rover if the wheel became fully operational again. The right rear wheel had also stalled on sol 2097 November 28 and remained inoperable for the remainder of the mission. This left the rover with only four fully operational wheels.

    This problem is the weakness of materials brought about by keeping down Mars Rover Curiosity’s weight.
    Aluminium is a soft metal which is not very resistant to abrasion or impacts from hard rocks. Mars’ dusty wind-blown sand will also be abrasive on moving parts.



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  • 3
    NearlyNakedApe says:

    Just what I was thinking. Also, judging from the picture, the wheel’s skin looks pretty thin to me. I’m wondering why the NASA engineers didn’t use make the wheels out of titanium instead. I know it’s heavier than aluminium alloy but it’s far stronger. Also, most of the weight is in the body of the rover. Couldn’t they have made some trade-off to save weight there instead?



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  • There is a similar rover scheduled for 2020 / 2021 with some new experiments.

    http://www.bbc.co.uk/news/science-environment-28582903

    Nasa’s next Martian rover will attempt to make oxygen on the surface of the red planet when it lands there in 2021.

    The rover will carry seven scientific projects, aimed at paving the way for future manned missions, seeking evidence of life and storing samples to be brought back in the future.

    Among them is a device for turning the CO2 that dominates the thin Martian air into oxygen.

    This could support human life or make rocket fuel for return missions.

    The rover will also carry an experimental weather station among the 88lb (40kg) of instruments.

    http://news.bbcimg.co.uk/media/images/76674000/jpg/_76674840_nasa-mars-2020-rover-instrument-selection-pia18405-br2.jpg



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  • Also on the same link:-

    Also on board the 2020 rover will be a ground-penetrating radar for analysing the planet’s geology, two arm-mounted gadgets for analysing the chemistry and structure of soil and rocks, and two cameras.

    In another first, the cameras are designed so that in a particular configuration they will be able to record 3D movies.



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