It’s a special kind of dressage: When Raffaello D’Andrea lifts his right arm, a plate-sized helicopter obediently starts its engine. When he moves his finger through the air, the device follows as if on a horse’s lead. D’Andrea is a drone trainer. The professor is standing in socks with his legs apart on the floor of a gymnasium-like building at the Swiss Federal Institute of Technology (ETH) in Zurich. The floor is covered with mats to soften the impact when the expensive devices crash to the ground. And lest any errant drones escape from the “Flying Machine Arena” in the Mechanical Engineering Department, the 10-by-10-meter (1,075-square-foot) interior space is also surrounded by a net. Read More