When it Comes to Martian Rovers, Let’s Just Roll with It

As was recently reported regarding the Martian rover Spirit, wheeled robots have a propensity for getting mired in alien landscapes. As any mud bogging redneck will tell you, getting stuck is part of off-roading in unfamiliar territory. Spirit can’t call its third cousin (you know, the one with the monster truck) to come wench it out, which makes getting stuck on Mars a life-threatening mistake. Spirit performed for over twenty times its life expectancy, so few cried foul when the rover finally dug into a portion of soft Martian silt and got stuck. Despite rocking Spirit back and forth for several days (perhaps per the advice of some Houston and Cape Canaveral natives), it became clear that there was little hope for any roving in the future.

Given the many layers of difficulty already present when controlling a robot from up to hundreds of millions of miles away, minimizing any potential points of failure is critical. This led NASA to reconsider the ideal means of locomotion for any future robot used to scour extraterrestrial surfaces. Partly inspired by dust devils seen whipping across the Martian surface, scientists propose that Spirit’s predecessors may more resemble tumbleweed than the Battlebots-esque rovers of the past.

This is not a new idea, wind-driven Martian rovers were first discussed as early as 1977, but it took over thirty years for the technology to catch up with the inspiration. These tumbleweed rovers, as they are colloquially called, would do many of the same things as modern rovers. They would perform analysis on soil, air, and rock samples, map the terrestrial surface, and communicate images and data back to Martian orbiters. The robots would do these things without the benefit of tracks or wheels, being entirely guided by Martian winds. Operators back on Earth would have some flexibility to steer and manipulate the speed of the device by controlling the extent of its inflation. Totally deflating the robot would cause it to become temporarily stationary, permitting analysis of a particularly neat rock or bit of soil. Creative use of nonuniform inflation and positional weights could steer the robot over long distances. Other than that, however, the path of these robots would be somewhat random, trading off controllability for range. Spirit’s means of locomotion limited it to travelling only several miles during its life on Mars, but these tumbleweed rovers could potentially cover hundreds. Considering the light weight of these robots, the cost to deliver them to Mars would be relatively low. As a result, their application would consist of packs of dozens, or even hundreds of these rovers crisscrossing the planet. While some would get stuck in craters and become sedentary scientific platforms, the belief is that most would remain mobile for years. The low gravity and high winds on Mars suggests that they will easily bound over Martian rocks and up slopes. By generating power from kinetic energy and Martian wind, these robots could operate in areas with insufficient sunshine to permit solar-powered travel. This may permit the exploration of perpetually shaded craters and polar icecaps, where some of the most fascinating science remains to be done.

Testing of these tumbleweed rovers on the desolate and forbidding surfaces of Greenland and Antarctica demonstrate that they could travel for hundreds of miles without issue, all the while broadcasting location specific telemetry. Debates still exist as to the ideal shape and design of these rovers, but their inherent simplicity makes them so tantalizing an option for the exploration of planets and moons that they will almost certainly play a role in the future of space travel.

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~ by Wil Finley on March 7, 2010.

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