Types of Airships
As airships evolved, several distinct types appeared:
RIGID airships have an inner framework supporting a gas-tight envelope or skin. The rigid framework, usually a light metal such as aluminum, holds the ship together and supports the form. All airships made by Luftschiffbau Zeppelin GmbH and two dirigibles made by the Goodyear-Zeppelin Company USA, the US Navy's Akron and Macon, were rigid airships. Generally, rigid airships must be longer than 360feet / 120meters or else the weight to volume ratio will make them too inefficient. In other words, a small rigid airship would have too much framework in proportion to the amount of lifting gas that it could hold making it too heavy to fly. The rigid style of dirigible was the preferred design in Germany and most of the important historical events occurred in these ships.
The Bodensee Airship.
Probably at Lakehurst, New Jersey.
Photo: US Army Air Service.
National Archives and Records Administration.
Still Picture Branch; College Park, Maryland.
SEMI-RIGID dirigibles have a rigid keel that supports a pressurized envelope. The design may call for the keel to be attached directly to the envelope or to be hung underneath it. The parts of the vessel such as the gondola and engines are attached to the rigid keel. The most famous semi-rigid airship was the Italian Norge, which flew over the North Pole in 1926.
The Norge dirigible in England.
Photo: Pacific and Atlantic Photos.
Detroit Publishing Company.
Library of Congress. Prints and Photographs. Washington D.C.
NON-RIGID airships, now commonly known as blimps, are the most common type in use today. The non-rigid airship has no frame and the envelope holds its shape due to the pressurized lifting gas, usually helium, inside. To compensate for changes in gas pressure, non-rigid airships are equipped with internal air compartments called ballonets that can be inflated or deflated.
The US Navy's D-2 Airship, ca. 1919.
Photo: US Army Signal Corps.
Office of the Chief Signal Officer.
National Archives and Records Administration.
Still Picture Branch; College Park, Maryland.