Space-bound robots tend look like tanks and are about as flexible as the Tin Man after a rainstorm. Don’t get me wrong, the robots NASA sends to, say, Mars are very very smart. But their forms present some limitations; namely, snail-paced research, lumbering motions and proneness to injury.

Just imagine then, if there was a robot that had the brains of Curiosity but the nimbleness of a tumbleweed. That’s exactly what a group of scientists at NASA are looking to create with the Super Ball Bot, a tangle of rods and motors that could revolutionize the way robots work in space and here on Earth.

>By adjusting the length of the cables, this flexible robot can roll around.

The Super Ball Bot, currently deep in the research phase in NASA’s Innovative Advanced Concepts program, looks nothing like its robotic predecessors. The spindly sphere is a tensegrity structure, which means to move it relies on a system of rigid components that are connected by flexible joints and cables.

This allows the bot to evenly distribute stress and pressure over the entire structure, as opposed to concentrating it on specific joints. The idea is that by adjusting the length of the cables, this flexible robot will be able to roll around the surface of a planet or moon with more speed and resiliency than wheeled robots could even dream about.

An Idea That Sprung Up in Art

Though tensegrity is built into all sorts of natural systems, as a defined concept it has only been around since the late 1940s when artist Kenneth Snelson began exploring the idea with his flexible, tension-based sculptures (he preferred to call it "floating compression"). Of course, if you look around you’ll see the principles everywhere: baby toys, bridges, circus tents. Hell, even your spine is based on this model.

“Tensegrity systems are compliant without sacrificing rigidity,” explains Adrian Agogino, who along with Vytas SunSpiral is developing the Super Ball Bot. “They naturally kind of change shape as they’re touching things so they don’t break things, but things also don’t break them.”

You can imagine that when applied to robotics, this concept is very appealing to NASA. There are a few obvious benefits, beginning with the simple fact that sending a tensegrity robot into space will eventually be cheaper and safer. The researchers are eyeing Titan, one of Saturn's moons, for the 'bot's first mission. The goal is to use the Super Ball Bot's inherent resiliency to land on Titan without assistance, which frees up space usually taken up by bulky landing gear.

That same compliance will allow the robot to access areas of a surface that would normally be too risky for wheeled rovers. “Unfortunately, the very interesting scientific questions are at the most dangerous locations,” explains SunSpiral. “Edges of cliffs where rocks are exposed, where people can really see the geology and history.”

The thought of sending multi-million dollar robots to the cliff edges not only makes engineers shudder, but doing so would take the robot days. Agogino puts it into perspective: “Something that we could do in 20 to 40 seconds is an entire-day operation for robots,” he says.

>'This is a fundamentally new approach to building robots.'

So what's the hold up? SunSpiral says research has been ongoing in the field for more than a decade, but we’re just now at the edge of having the tools to make tensegrity robots a reality. Plus, the scientists add, these types of robots are not exactly first nature for engineers. “This is very not aligned with traditional engineering where you're trying to break down big parts into little part and compartmentalize them,” says Agogino.

“If you look at how robots have traditionally been made, the classic approach is you have some hunks of metal that you then attach motors to so it can move,” adds SunSpiral. “It’s a nice linear system; it’s easy to model how things will behave. This is a fundamentally new approach to building robots.”

Testing the Super Ball Bot.

It's fun to think about how this concept could be applied outside the realm of space exploration. Drawing on natural systems that adjust and adapt to environments is fascinating, and one that's already being explored in fields like architecture and art. While teaching a class at UC Berkeley, collaborator Alice Agogino asked students to come up with 50 potential applications for tensegrity robots and to rank them according to how useful they might one day be.

“The two highest fits were in home health care and the military,” he says. “Two extreme applications.” The point being, by its very nature a tensegrity robot is able to be both sturdy and resilient while still being gentle enough to interact with sick people. “This is really at the heart of what we’re getting at,” says SunSpiral. “Using a system that’s much more adaptable to its environment.”

As it stands, The Super Ball Bot won’t leave our atmosphere for at least 10 more years, which actually isn't very surprising when you watch the ball twitch and move. Technologies still need to be developed and controls worked out before the bot can function without direct supervision. SunSpiral sums up the challenge this way: “Lots of new design challenges come up when you turn the whole world upside down and do something different.”