Abstract: Systems and methods for limiting rotation of a supported object about an axis of rotation are provided. A system as disclosed includes a stop system that engages at a selected amount of rotation about an axis of rotation to provide a balanced force countering further rotation. The stop system includes one or more pairs of stop mechanisms, with one stop mechanism in a pair disposed to act from a first side of the axis of rotation, and a second stop mechanism in the pair disposed to act from a second side of the axis of rotation. Each stop mechanism can include stops that engage a flexure at a selected amount of rotation.

Abstract: A neutral buoyancy fuel bladder uses hydrogen and oxygen to power an airship. The neutral buoyancy fuel bladder includes a fuel cell, electrolyzer, and means for storing hydrogen, oxygen and water. The fuel cell uses the hydrogen and oxygen to create heat, water and current flow. An energy source transmits a beam to an energy receiving unit on the airship, and the energy from said beam is used to (1) power said airship, and (2) replenish the supply of hydrogen and oxygen.