Wheel Stalls Hinder Stuck Mars Rover Again

Wheel Stalls Hinder Stuck Mars Rover Again
This blink comparison aids evaluation of a drive by NASA's Mars Exploration Rover Spirit during the rover's 2,099th Martian day, or sol (Nov. 28, 2009). A stall by the right-rear wheel ended the drive partway through the first of two planned wheel spins. Most of the wheel movement was slippage. Click on the image to see the animated image. (Image credit: NASA/JPL-Caltech)

One of the wheels on the stuck Mars rover Spirit has stalledagain, once more causing a snag in NASA?s attempts to free the rover.


Spirit's right-rear wheel stalled again on Nov. 28 duringthe first step of a two-step extricationmaneuver. The wheel first stalled a week prior during another driveattempt, though engineers couldn't replicate the stall during diagnostic testslast week. Those tests showed a fully functioning wheel.


This mostrecent stall had some different characteristics than the new stall, a NASAreport said. It occurred more quickly and had a different signature to it.


Engineers think this new stall could be caused not by theMartian terrain, but might be internal to the pluckyrover?s right-rear wheel actuator.


Rover project engineers are developing a series ofdiagnostics to explore the actuator health and to isolate potential terraininteractions. These diagnostics won't be run before Wednesday and any futuredriving attempts will depend on the results of those tests.


Before the Nov. 28 drive ended, Spirit completed 4.5 feet (1.4meters) of wheel spin and the rover's center moved 0.02 inch (0.5 mm) forward,0.01 inch (0.25 mm) to the left and 0.02 inch (0.5 mm) downward. Since theeffort to free Spirit began, the rover has performed 31 feet (9.5 meters) ofwheel spin and the rover's center, in total, has moved 0.63 inches (16 mm)forward, 0.39 inches (10 mm) to the left and 0.20 inches (5 mm) downward.


The rover, and its sister robot Opportunity, have beenexploring different parts of Mars since January 2004.


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