Airship

An intermediate version of the rigid and non-rigid types, the envelope of the semi-rigid airship was fitted with a keel similar to that of a boat. The keel acted as a sort of metal spine which helped maintain the envelope's shape and supported the gondola and engines. Interest in the semi-rigid airship was short-lived, though it met with some success. In 1926, the Italian pilot Umberto Nobile navigated the airship Norge across the North Pole, accompanied by the Norwegian explorer Roald Amundsen.