How NASA Drives The Mars Curiosity Rover: With Special Software

What is it like to drive on Mars? Every movement on the rough terrain risks damage to the wheels on NASA’s Curiosity rover, which would be stranded on the alien planet, a trip of several months away from any Earth help, should anything go seriously wrong. To avoid a terminal error, NASA has developed a new algorithm for driving its rover that changes the wheels’ speed based on what rocks are beneath them.

NASA’s Jet Propulsion Laboratory said the software was uploaded onto the rover earlier this year, following months of testing on the ground, and the space agency started using it in June. It’s geared toward traction control — stopping the six wheels from spinning at different speeds when one or more of them climbs over a rock.

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“When a wheel goes over uneven terrain, the incline causes the wheels behind or in front of it to start slipping,” NASA explained. “This change in traction is especially problematic when going over pointed, embedded rocks. When this happens, the wheels in front pull the trailing wheels into rocks; the wheels behind push the leading wheels into rocks.”

Because the wheel mounting the pointy rock may experience more force pushing it into the sharp edge, it could become cracked or punctured, particularly in the space between the wheel treads that are known as the grousers.

The rover hasn’t sustained any damage that spells imminent trouble, but the wheels have taken a beating. The new software responds to what the wheels are driving over, based on how the terrain is affecting their suspension system, and changes their speeds individually to improve traction and stop the rocks from causing damage. It also stops one end of the rover from leaving the ground — in a wheelie — as a result of uneven terrain.

“The wheel wear has been cause for concern, and although we estimate they have years of life still in them, we do want to reduce that wear whenever possible to extend the life of the wheels,” JPL’s Art Rankin said in the NASA statement.

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According to the space agency, the software reduces pressure on the front wheels by 20 percent and cuts the pressure on the middle wheels 11 percent.

NASA engineers have long had the rough Mars terrain in mind as they designed vehicles that would traverse its surface. In March, the space agency unveiled a robot prototype, which could one day be developed into a scouter that would accompany a Mars rover, that has special wheels and a tail fin to help it climb rocky obstacles. The tail fin on the PUFFER robot is used as leverage to propel the treaded wheels upward and onto higher surfaces.

That robot can also fold itself up to squeeze into tight places a larger rover could not reach.