It’s three in the afternoon, and in their Nasa lab in Silicon Valley, California, two engineers are playing with a toy designed for toddlers. The melon-sized plaything consists of a tactile lattice of brightly painted beads, connected by wooden rods and elastic cords. It twists and flexes as Vytas Sunspiral and Adrian Agogino crunch it in their hands and throw it between themselves across the room.
One online review describes the gadget as “great for sensory exploration,” but Sunspiral and Agogino are considering it for something way more ambitious: planetary exploration. This bundle of beads, rods and cords, they believe, could form the basis of a new generation of planetary rovers.
“The programme that funded this bit of research, I call it the crazy ideas programme,” exclaims the fast-talking Sunspiral, a towering figure whose name, long blonde hair, beard and glasses suggest a “crazy ideas” lab in Silicon Valley is his natural environment. For obvious reasons, Nasa prefers not to use the word “crazy” in its research but includes the project under its Innovative Advanced Concepts Program. “Here, in the intelligent robotics group,” says Sunspiral, “we do all sorts of advanced research on robots.”
The toy Sunspiral and Agogino are playing with uses what is technically known as a tensegrity system. “It’s a system where, unlike our buildings where everything’s held together rigidly, everything’s held together in tension,” Sunspiral explains. “So you end up with a network of cables that hold rods. You will often have seen artwork that looks like this – kind of crazy weird bars, floating in space.”
“The components are very simple,” adds Agogino, twisting the toy in his hands as he speaks. “They’re just rods and cables connected together, and rods never connect to rods and cables never connect to cables. A child can hit themselves over the head with it and they won’t get hurt. That happens to be great for what we want.”
To prove the point, Vytas encourages me to throw the toy on the floor. Hard. It slams into the floor, squashes together a bit and bounces. “Think of what’s happening when it bounces,” he says. “It’s absorbing energy when it’s going down and it’s releasing energy when it’s going up. It doesn’t break because the energy is distributed.”
Garage games
You can imagine that dropping one of these on the surface of an alien world would certainly be a lot easier than landing the existing types of robotic rovers with all their precision engineered wheels, motors and instruments. Past missions, such as the Spirit and Opportunity rovers, used airbags to cushion their landings. Because of its hefty size, Nasa’s Curiosity had to be lowered on cables using its elaborate sky-crane system. “Drop one of those rovers 30 feet,” says Agogino, “do you think it’s going to be very happy about it?”
But existing planetary rovers are shaped the way they are for a reason: they need wheels to move around, bodies to hold equipment and arms to deploy instruments or cameras. So how do you do that with a glorified bundle of beads, rods and elastic? “We get a lot of our inspiration from biological systems,” says Sunspiral, who suggests a mechanism that mimics how our own muscles expand and contract could offer one solution. “You could shorten and lengthen the cables to cause the whole thing to roll and move around.”
