Hedgehog robot. Animation showing the internal mechanism of the Hedgehog robot, followed by footage of a Hedgehog prototype performing a tumble. Researchers at NASA's Jet Propulsion Laboratory have developed the Hedgehog robot concept to explore the rugged microgravity environments of comets and asteroids. Instead of rolling around on wheels, the Hedgehog design has three flywheels on the inside of a cube. By spinning these flywheels and then very quickly applying the brake, momentum is transferred from the fly wheels, causing Hedgehog to either hop, or tumble, or perform small adjustments. The robot can function irrespective of orientation, and can negotiate irregular terrain in microgravity where conventional wheeled rovers would fail.