Sunset vented a morose grunt, barely audible over the dull roar of the gasoline engines still running. One was missing; its mate on the envelope's other side was shut down for symmetry of thrust. At half power, the ship seemed to crawl, wobbling as breezes and eddies it normally resisted played with the huge sail area of the envelope. Otherwise the world seemed utterly silent aside from the whistle of air across every surface it encountered.