Solar sails have some major advantages over traditional propulsion methods—most notably, they don't use any propellant. But, how exactly do they turn? In traditional sailing, a ship's captain can simply adjust the angle of the sail itself to catch the wind at a different angle. But they also have the added advantage of a rudder, which doesn't work when sailing on light. This has been a long-standing challenge, but a new paper available on the arXiv preprint server by Gulzhan Aldan and Igor Bargatin at the University of Pennsylvania describes a new technique to turn solar sails—kirigami.