Popular in Victorian and Steampunk fantasies, airships and zeppelins evoke a certain elegance that most modern travelers don't associate with the airplane. Some companies are capitalizing on that idea, and a need to move cargo by air in an era of ever-increasing fuel costs, to re-re-introduce commercial zeppelins. Popular Mechanics notes four notable airship designs, all with specific design purposes. One craft in particular, the Aeroscraft ML866, is being funded by the US government's DARPA group. It looks to combine the best elements of the helicopter and the zeppelin. "The Aeroscraft ML866's potentially revolutionary Control of Static Heaviness system compresses and decompresses helium in the 210-ft.-long envelope, changing this proposed sky yacht's buoyancy during takeoff and landings, Aeros says. It hopes to end the program with a test flight demonstrating the system. "