Tumbleweed rovers are inflatable balls with mechanical control structures. Rolling across the Martian surface like a mechanical tumbleweed, such a rover could move faster and cover more ground than a wheeled rover like the Curiosity Mars Science Laboratory, at much lower cost. NASA and a number of universities have built and tested prototypes. NASA has tested prototypes in the Mojave Desert and the frozen waste of Antarctica.

A tumbleweed rover would use the Martian wind for locomotion and shifting balance for control. According to previous work at JPL, tumbleweed rovers could achieve speeds of 20 miles per hour in typical afternoon winds, compared to a top speed of 0.1 miles per hour for Curiosity. A tumbleweed rover 6 meters in diameter could climb over one-meter rocks and travel up 20-degree slopes in moderate winds and 45-degree slopes in strong winds. A 6-meter diameter rover would have a mass of 44 pounds and a 44-pound science payload. (The Curiosity rover weighs over 1,980 pounds.) Additionally, the rover’s inflatable ball can function as both parachute and airbag for the landing, saving on overall system weight.

One challenge is controlling such high-speed rovers from Earth, but if control issues can be worked out, the potential payoff is enormous. A single mission could deploy an entire fleet of tumbleweed rovers, and because the rovers would be built in quantity, they would be significantly more affordable than one-off hardware like Curiosity.

Tumbling rovers may be applicable to other destinations besides Mars. Studies have shown that Pluto’s atmosphere doesn’t have enough wind, but Triton might possibly have winds that are high enough. Io, on the other hand, is expected to have supersonic winds due to volcanic eruptions, which should easily move a tumbleweed even in the thin atmosphere.

Wind-blown rovers won’t work on airless bodies, but mechanical tumbling is another possibility. A team headed Dr. Marco Pavone at Stanford University is studying an asteroid rover concept with funding from a previous NIAC grant. Dr. Pavone’s concept is not an inflatable ball but a spiked sphere which combines tumbling motion to short-range travel with hopping for longer distances.

Tumbling/hopping rovers for asteroids

The tumbleweed rover could significantly improve the cost-effectiveness of future Mars science missions. Unfortunately, NASA may not be able to take advantage of such breakthrough technologies due to the perverse incentives of government space missions.

 

Written by Astro1 on August 25th, 2012 , Innovation, Planetary science

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