[meteorite-list] Second Test Rover Added to Driving Experiments

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.cfm?release=2009-129  

Second Test Rover Added to Driving Experiments
Jet Propulsion Laboratory
August 21, 2009

A second, lighter-weight test rover has entered the testing setup at JPL
where rover team members are assessing strategy for getting Spirit out
of soft soil where it is embedded on Mars.

The rover team has begun using a test rover that does not carry a
science payload or robotic arm, as do Spirit and Opportunity on Mars,
and the primary engineering test rover at JPL. While the primary test
rover's weight on Earth is greater than Spirit's weight on Mars, the
second rover is even lighter on Earth and closer to the weight of Spirit
on Mars.

Making comparisons between motions of the two test rovers in duplicated
drives will aid the rover team in interpreting effects of differing
gravity on rover mobility. The testing team plans to run such
comparisons both in the soft, fluffy material being used to simulate the
soil at Spirit's current location and also on coarser, crushed rock that
offers better traction.

"There is no perfect Earth analog for Spirit's current situation," said
JPL's John Callas, project manager for the twin Mars Exploration Rovers.
"There's less gravity on Mars, little atmosphere, and no moisture in the
soil where Spirit is. It is not anything like being stuck in sand or
snow or mud on Earth. Plus, since the rover moves only about as fast as
a tortoise, you cannot use momentum to help. No rocking back and forth
as you might do on Earth."

The comparison experiments with the two test-rover siblings to Spirit
and Opportunity precede a planned "dress rehearsal" long-duration test
of driving as far in the test setup as the distance that Spirit would
need to achieve on Mars to escape its predicament at the site called
"Troy."

The team has also made further assessments of the position of a rock
underneath Spirit relative to the rover's center of gravity. Part of the
strategy for getting Spirit free will be to avoid getting in a position
with the center of gravity directly over a rock touching the rover.

For more updates, please visit the Free Spirit site:
http://www.jpl.nasa.gov/freespirit/