Hovering not hard if you're top heavy, NYU researchers find

Researchers at New York University’s Courant Institute of Mathematical Sciences and Department of Physics have found that top-heavy structures are more likely to maintain their balance while hovering in the air than those that bear a lower center of gravity. To gauge which types of structures best maintained their balance, the researchers created paper bugs with various centers of mass. Top-heavy bugs were made by fixing a weight above the pyramid, and low center-of-mass bugs bore this weight below. Surprisingly, their results showed that the top-heavy bugs hovered stably while those with a lower center of mass could not maintain their balance; the team showed that when the top-heavy bug tilts, the swirls of air ejected from the far side of the body automatically adjust to keep it upright. The lessons learned from these studies could be put to use in designing stable and maneuverable flapping-wing robots; they also illuminate design principles that could be used in the development of larger hovercraft.