Spherical Mini-Rover is a prototype of a miniature roving device for the exploration of planetary surfaces. This design was limited to demonstrating the mechanical and electrical drive.
Propulsion is by means of an interior mass.
The torque from an electric motor lifts the eccentric mass against gravity, inducing a rotation of the sphere. The rover's circuitry is able to determine when its motor has stalled for more than two seconds, reversing the current, and thereby the rover's path. This allows the rover to back-off and reverse course when stopped by an obstacle such as a rock.