by Mark Aragona
As the Mars rovers have shown, planetary explorers such as these encounter several tough challenges to their design. Their weight can get them bogged down in sinkholes or sand traps, as in the case of Spirit, which ended up stuck in Gustav crater. Dirt and grit can jam their wheels or treads, stranding them. And there’s always the problem of their batteries running flat when there’s not enough sun to charge them—a real problem during long, extraterrestrial winters. With all of that and the soaring cost of building and sending another rover (another $2.5B according to NASA), the question of exploring planets becomes as much economic as it is scientific—what’s the most cost-effective way to explore a planet’s surface?
The answer, as it turns out, is blowing in the wind. Scientists are turning to a possible new design which can avoid most of these problems AND scour wide areas of the planet—the tumbleweed rover. Imagine a giant beach ball-shaped robot made of lightweight metal and plastics. Instead of trundling along on treads, this 6 meter-tall ball would roll along at the speed of the wind.
Because of their design, tumbleweed rovers can explore a planet’s surface with little regard to the terrain. NASA’s experiments in Greenland and Antarctica showed that the rover could cover hundreds of miles without stopping. There wouldn’t be a need to halt and recharge, and in fact the rovers could use their own kinetic energy to power the instruments they carry.
The tumbleweed’s simplistic design means that there won’t be joints or spaces for dirt to clog up. Sand traps won’t bog it down, and it wouldn’t get caught between rocks or crevices. NASA’s experiments in the Mojave Desert showed that a tumbleweed rover can climb over slopes of 25 degrees or more, and roll over or around rocks as high as a meter.
It may even float on water.
Imagine building an entire fleet of these robotic tumblers and setting them loose on a planet’s surface. Even if one is lost or stuck, it would be an acceptable loss considering how much data it would have collected compared to its production cost. If it finds an area of interest, it gathers data on demand and moves on afterwards. Scientists are also testing if the tumbleweed can be its own parachute, so that they can be dropped straight from a satellite without having to use a lander.
Of course, there are limitations to the tumbleweed design. You can’t put heavy equipment on the rover, so each one may have to specialize for certain tasks—looking at the soil, the weather, etc. Moreover, it can’t explore areas that have no wind—caves, underground areas, or any planet without an atmosphere. But it can be used in tandem with other rover designs. Once the tumbleweeds have found areas of interest, other types of rovers may come and do the heavy-duty work, such as digging, probing, and collecting samples. Tumbleweeds can save space explorers a lot of time, effort, and certainly money.
The tumbleweed design is still in its early stages and needs more funding and miniaturized technology before it can see use, but its future is looking very bright. And while it’s not being used in real life just yet, it can certainly roam the wilderness of science fiction.