Designing 'Tumbleweed' Rovers for Mars

Moving on the surface of Mars is notoriously difficult. Rovers roaming the Red Planet have found out the hard way that speed and maneuverability are limited, as evidenced by the case of the MER robot Spirit. The machine became entrapped in sand in May 2009, and experts were unable to set it free again. Under these circumstances, plans to create a “tumbleweed” rover are beginning to make a bit more sense. These are wind-powered machines, most often shaped like spheres, which simply drift under gusts of wind to wherever the Martian air moves.

The concept is not new at all. For more than a decade, researchers have been thinking about the challenges associated with sending such machines to Mars, but thus far no serious thought was put into this issue. Now, researchers at the North Carolina State University (NC State) develop a new series of computer models, which they use to assess various types of tumbleweed rover designs. This is done because actually constructing prototypes for testing in real-world conditions is expensive and time-consuming. Plus, the models allow for scientist to tweak rover traits on-the-fly.

“We wanted a way to determine how different tumbleweed rover designs would behave under the various conditions that may be faced on the Martian surface. The model that we've developed is important, because it will help NASA make informed decisions about the final design characteristics of any tumbleweed rovers it ultimately sends to Mars,” explains NC State associate professor of mechanical and aerospace engineering, Dr. Andre Mazzoleni. He is also the coauthor of a new paper describing the simulation-based findings.

“You can't just build hundreds of different rover designs to see what works – it's too expensive. This model allows us to determine which designs may be most viable. Then we can move forward to build and test the most promising candidates,” adds NC State PhD student and paper coauthor Alexandre Hartl. “We're optimistic that our model can serve as a mission design tool that NASA can use to choose appropriate design parameters,” Mazzoleni says. He adds that two NASA facilities, the Pasadena, California-based Jet Propulsion Laboratory (JPL) and Langley Research Center, in Virginia, are interested in the idea of sending tumbleweed rovers to the Red Planet.