They are based on a non-rigid design, in which the pressure of the helium inside the envelope is used to maintain the airship's shape.

ECONOMIST: Pushing the envelope

So far, the company has built a one-eighth-size prototype to test its design, which consists of a carbon-fibre keel, an envelope made from modern composite materials, half-a-dozen engines, a passenger compartment, and a specially lightened crane.

ECONOMIST: Pushing the envelope

Larger modern airships rely on a semi-rigid design, in which engines and passenger compartments are suspended from a metal keel that runs along the bottom of the envelope and prevents it from distorting under the load.

ECONOMIST: Pushing the envelope

The advantage of this arrangement is that it can be scaled up more easily than a semi-rigid design, since the envelope is not load-bearing.

ECONOMIST: Pushing the envelope