Spinning a solar sail pulls the sail material out tight and flat so it doesn't collapse when sunlight pushes on it. This is called centripetal acceleration, and is the same effect that prevents water from flowing out of a bucket that is being swung in a circle. Because the sail material itself is very lightweight, it needs to be reinforced with tension lines to carry most of the loads caused by spinning. This results in a sail that needs very little heavy structure, because tension lines are much lighter than the booms used in Three-Axis Stabilized solar sails. Thus, spinning sails have potential for being lighter and faster.