LEGO MINDSTORMS Robot Inventor
Satellites in space use Reaction Wheels to keep them pointing in the right direction. Even though there is nothing external to the satellite for motors to push against in space, they can make directional adjustments by taking advantage of Conservation of Angular Momentum. This model balances on a low-friction stand to simulate this and turns a reaction wheel to change its angle.
Three different programs are provided, and they all allow you to turn the model by remote control. The simplest program just directly controls the reaction wheel motor power with a slider, to give you a feel for how the physics works and how hard it is to get an exact angle. The most complex program uses a mathematical control technical called a PID Controller to zero in on the desired angle positions.
The second and third programs use the hub's gyro sensor to sense the angle that the model is pointed, so see this note to make sure the gyro is properly calibrated before you start. You should remove the model from the stand and place it flat and motionless on the table to let it calibrate.