Rotastat: A combination of rotary wing (helicopter) and aerostat (balloon). Also known as a hybrid airship. A conventional helicopter uses most of its power just to lift its own airframe, fuel and pilot. Not much is left for payload. What if we bolt a bunch of helicopters to an airship? The helium could support the weight of not just the airship, but the helicopter parts as well. Then 100% of the rotor lift could go into hauling payload, and the whole craft could raise and lower itself without the need for fooling around with ballast or venting gas. In 1986, an aircraft called the Helistat was assembled from four used helicopters and a blimp. Because it was the eighties, there was no fancy computer control; each helicopter was operated by a separate pilot. The experiment ended badly when the framework holding everything together failed, tilting one of the helicopters into the blimp. One pilot was killed and the whole machine tore itself apart. It may have been a flawed design, but it was a good idea. I’d like to see what could be done with the concept today.
Tech Level: Lower than you might think. You don’t need sophisticated helicopters; any old propellers will do. The lifting power of helium (or hydrogen, for the fearless) can support a lot of weight if the airship is big enough. Power to weight ratio is less important than in other forms of powered flight. It might fit Steampunk or Solarpunk.
Appeared In: Well, not exactly, but Jules Verne wrote Robur the Conqueror and its sequel, Master of the World. Both books featured a multi-rotor flying machine that did not use any lifting gases.
For Your Plot: If you’d like to steal something large and heavy, like the Statue of Liberty, (225 tons) you’re going to want a Rotastat. A big one. Just don’t count on a speedy getaway.