Photograph of the Front of the Control Car in a Dirigible
Original caption: Front of control car. Rudder wheel - rudder control chains and wires going up. Engine telegraphs.
The main types of airship are non-rigid, semi-rigid, and rigid. Non-rigid airships, often called "blimps", rely on internal pressure to maintain the shape of the airship. Semi-rigid airships maintain the envelope shape by internal pressure but have a supporting structure. Rigid airships have an outer structural framework which maintains the shape and carries all structural loads, while the lifting gas is contained in internal gas bags or cells. Rigid airships were first flown by Count Zeppelin and the vast majority of rigid airships built were manufactured by the firm he founded. As a result, all rigid airships are sometimes called zeppelins. In early dirigibles, the lifting gas used was hydrogen, due to its high lifting capacity and ready availability. Helium gas has almost the same lifting capacity and is not flammable, unlike hydrogen, but is rare and relatively expensive. Airships were most commonly used before the 1940s, but their use decreased over time as their capabilities were surpassed by those of aeroplanes.
The Joint Committee to Investigate Dirigible Disasters was created to investigate the cause of the USS Akron disaster and the wrecks of other Army and Navy dirigibles and to determine responsibility. These photographs were submitted to the Joint Committee during its investigation.