Careful driving helps reduce wear on Curiosity's wheels

Recent changes to the techniques used to drive Curiosity across the Martian surface have resulted in substantially less wear on the rover's wheels, NASA reported this week.  This is important because, with months of driving to go before the Mars Science Laboratory reaches its next destination, damage to the wheels had been building up much faster than anticipated.  By implementing changes in how the rover is routed across rough terrain, mission controllers have reduced the rate of this buildup by more than a factor of ten.

The undamaged wheels of Curiosity's twin here on Earth.  This exact copy was severed damaged to test the rover's performance in a worst-case scenario.  Recent results indicate that we shouldn't be worried.  (Image credit: Wikimedia user Z22)

Designing wheels for driving on another world is no easy task. With rocket payloads limited and no tune-ups available, rovers' wheels must be light, strong, and durable.  They must also provide sufficient traction over a wide range of known and unknown surfaces.  Curiosity's wheels and suspension system are an engineering marvel: six treaded wheels, independently controlled and cushioned.  The four corner wheels can be steered individually and the whole system is capable of stably supporting the rover on inclines of at least 50 degrees.  Even the pattern of the tread is useful - onboard cameras watch the pattern stamped out in the sand to estimate the distance travelled.

Most importantly, the wheels are capable of providing support and traction even when severely damaged.  With no spare tires available on Mars, this is a critical functionality.

Despite this rigorous and durable design, project engineers were concerned with the unexpectedly-high rate of wear and tear Curiosity's wheels were accruing during the first year of her mission.  The majority of this damage was in the form of punctures sustained when driving over especially sharp and hard rocks.  Since leaving Yellowknife Bay on her trek to Mount Sharp, the rover has been forced to drive over expanses of erosion-resistant capping layers of rock.  The sharp peaks of these rock formations poked holes in the wheels as the rover scrambled over them.

The change made was pretty simple: when possible, avoid driving over capping layers.  Sometimes this results in a longer route, but the result has been the rate of new wheel damage dropping to less than a tenth of the previous pace.  Not bad for simply looking where we're going!

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