iceCube: a self-centered spherebot

Chief architect: Andrew Cavender

In the 1999 remake of The Avengers, John Steed and Emma Peel walk across the Thames enclosed in large plastic spheres (which are now available commercially from Waterwalkerz, Ltd). Though small hamster balls have been popular pet novelties for decades, the Rhino character from Disney's 2008 animation Bolt brought the idea to the forefront on the silver screen.

There have been several spherebots designed in recent years around this basic hamster-ball concept. Though engaging, all such vehicles suffer from a fundamental performance limitation: they can acclerate only as fast as a certain fraction of the acceleration due to gravity, as dictated by basic geometric arguments (related to the possible positions of the center of mass within the sphere).


The iceCube concept, completed CAD design (with upper hemisphere removed for clarity), and prototype.


iceCube takes the idea of spherebots to the next level, and is distinguished from all other spherebots we are aware of in that its center of mass is always at the center of the sphere. Rather than moving the center of mass, iceCube builds up angular momentum in four carefully-configured, internal gimballed flywheels (known in such applications as control moment gyros, or CMGs), then, when necessary, reorients these spinning flywheels to impart, quickly, large coordinated reaction torques on the sphere. This approach bypasses the fundamental performance limitation associated with the hamster-ball concept, and is limited only by the friction between the sphere and the ground, which can be enhanced by endowing the sphere with a rough surface. Note also that iceCube can be made lighter than water to make an amphibious vehicle that can swim by spinning, and can also be made with small pressure bladders to accurately control its buoyancy, thereby enabling it to float (and maneuver) just below the surface for stealth amphibious operations.

iceCube was built using the Technologic Systems TS-7250 and Arduino boards, and was programmed primarily using low-level coding in C.