Building robots is hard. It's easiest if the robot has a dedicated function and environment. In those cases, you can create a design that works best within the robot's surroundings and is the most efficient use of energy. But as a robot's purpose and surroundings become more complex, building a machine that functions well gets pretty tough.
So imagine that your job is to design a robot to explore stuff like asteroids and comets. The gravity on these objects would be very low — wheels and legs wouldn't work very well. You can't even be sure what the topography will be like because you haven't had a close enough look yet. What would you do? Engineers at Stanford, together with colleagues from MIT and NASA's Jet Propulsion Lab, responded to this challenge by building a cube-shaped robot. They call it Hedgehog.
Hedgehog looks like a six-sided die. It has three internal flywheels that can spin and brake rapidly. This motion creates internal actuation, which translates into a small hopping motion. On Earth, this makes the cube wobble a little. On an asteroid with little gravity, it creates a hop strong enough for the cube to move but not so strong that it will eject itself into space.
The next stage in Hedgehog's evolution is autonomy. As Stanford scientists have pointed out, you can't maintain human control of robots in deep space. The communications delay alone makes it impractical. There needs to be a way for Hedgehog to go where scientists want it to without directing every individual hop. Hedgehog will have to find its own way out in the cold, dark reaches of space.
It will also need to carry sensors and other equipment to do more than just hop around on a comet's surface. Ultimately, exploring distant bodies whizzing around our solar system may help us with our own space travel. It can also be useful if we need to mine asteroids for resources or even nudge one out of a collision course with Earth. Not since Sonic have we seen a Hedgehog with such grand ambition.