The riders all lined up in their zorbs on an embankment ahead of an undulating field marked with pairs of small hills. The hills contain near field communications to detect the passing riders and count their progress. As the countdown tones began, the zorbs spun up their reaction wheels to get maximum
The zorbs are made similar to existing zorbs with two bouncy spheres one inside the other separated by plastic ties (pillars). The difference in this case is that the sides of the inner sphere are toughened to mount a central axis on which to hang the gyros, rider etc.
The rider sits in a harness so that the central pivot bar runs just behind their shoulders.The harness can be driven around the pivot bar (more on this later). Behind the bar is a reaction wheel* with its axis front to back of the zorb. The two main reaction wheels spin either side of the rider on the central axis driven by some beefy electric motors. The batteries and control system hang below the pivot behind the driver but can be adjusted to balance the driver such that when the zorb is powered down the driver is looking horizontally.
The control computer would need to be as sophisticated as a sports drone or combat helicopter taking many dynamic inputs into consideration when rolling out an actuator response. At its disposal are various drives -
1) The side reaction wheels. Accelerating these will cause an equal and opposite turning torque. Accelerating one and decelerating the other will cause the zorb to turn. This input can impart huge acceleration up to a maximum total energy store. At this point the flywheels are spinning at maximum speed and can only provide impulses in one direction. The control computer seeks to have all reaction wheels at rest when moving at an average speed such that sudden braking and acceleration is possible.
2) The entire inner payload sits below the centre of gravity so that rotating the payload around the central axis will cause the zorb to accelerate forwards or backwards. The limit of this acceleration is when the driver is looking uncomfortably downwards or upwards to stay in control of the vehicle. At average speed the control box is spinning the payload to match the speed of the zorb so that the driver is looking horizontally. This is particularly the case when the main reaction wheels (1) are active.
3) The back reaction wheel can compensate for tilt due to terrain or precessional turning artefacts.
* Reaction wheel [link]s.
Larger zorbs could play around with the number of elements hanging from the central pivot bar The rider could be independent of some side weights. In fact, you could arrange it so that with a small cost to balance, the driver tilts the opposite way to that needed e.g. legs forward when braking. For that cost you get the feeling of 'flying forward' when accelerating or sliding into a base in a cloud of dust when decelerating.