Introduction to Dirigible
Dirigibleor Airship, a balloon that is self-propelled and that can be steered. There are three types: (1) the rigid dirigible, which holds its shape by means of a rigid metal framework around the gas cells; (2) the semirigid dirigible, which has a rigid keel along the bottom inside a single fabric gas bag, known as the envelope, but no framework around the envelope; and (3) the nonrigid dirigible, which holds its shape only by the pressure of the gas inside the fabric envelope. This article is concerned with rigid and semirigid dirigibles. Nonrigid dirigibles are discussed in the article Blimp.
Dirigibles were used as military weapons in World War I and as passenger and cargo ships from 1910 to 1937. The dirigible's main advantages over airplanes of the same period were lifting power, long range, and the ability to hover. However, dirigibles did not approach the speed of airplanes. Except for blimps, no dirigibles were used during World War II. Airplanes have completely replaced dirigibles for carrying passengers and cargo.
The Parts of A Dirigible
The framework of a rigid dirigible consists of lengthwise metal girders held together by encircling metal rings. The girders, usually made of strong aluminum alloy material, are shaped to meet at the nose and tail of the framework. Fixed surfaces, known as fins, are attached to the tail section of the framework. To the vertical fins are hinged the rudders that steer the dirigible, and to the horizontal fins are attached the elevators that control the angle at which the airship rises or descends.
The framework has an outer cover of cloth stretched and weatherproofed by several applications of aircraft dope. Inside the framework are several gas cells. These cells hold the lighter-than-air hydrogen or helium gas that make the dirigible buoyant, or able to float in the air. (Further information on the principles that explain why a dirigible remains aloft is found in the article Balloon.) The passenger cabins of dirigibles are suspended beneath the frame or placed inside it. The internal-combustion engines that turn the propellers are rigidly attached to the frame. (As on a ship, the propellers face rearward and push the dirigible forward.) The top speed of a dirigible is about 80 miles per hour (130 km/h), but it can travel 5,000 miles (8,000 km) without landing.
History of Dirigibles
The first real dirigible, driven by a steam engine, was built by Henri Giffard of France in 1852. Other early experimenters were Paul Haenlein, who built an airship in Germany in 1872; and Charles Renard and A. C. Krebs, French army officers, whose La France was flown in 1884. The man who made the dirigible practical was Count Ferdinand von Zeppelin of Germany. He completed his first rigid airship in 1900. In 1910, his first passenger dirigible, the Deutschland, was flying between Düsseldorf and Friedrichshafen, a distance of 300 miles (480 km). At that time rigid dirigibles became known as Zeppelins.
During World War I, Germany had a fleet of Zeppelins that were used in bombing raids over England, but they proved easy targets for airplanes and antiaircraft artillery. After the war the Zeppelin Los Angeles was built in Germany for the United States. France and Great Britain took over Germany's remaining long-range Zeppelins as spoils of war and forbade Germany to construct more.
British Rigid DirigiblesIn 1919 the British dirigible R-34 flew from Great Britain to the United States in four days and made the return trip in three. Great Britain constructed two commercial dirigibles, the R-100 and R-101, both completed in 1929. The R-100 made a successful round trip from England to Canada, but the R-101 crashed over France, the result of a flaw in its design. The R-100 was then scrapped and the British stopped building rigid dirigibles.
United States DirigiblesThe U.S. Army acquired the Italian semirigid airship Roma in 1921 and then procured, from an American builder, the RS-1 semirigid airship in 1925. The Roma was a hydrogen-inflated airship and was destroyed by fire. After that, all American airships used helium, which does not burn.
The first American-built rigid dirigible was the U.S. Navy's 682–foot (208–m) Shenandoah, completed in 1923. It broke apart in mid-air in 1925, killing 14 and injuring 2 of the 43 persons aboard. The Los Angeles, a 656–foot (200–m) rigid dirigible with a capacity of 2,500,000 cubic feet (70,000 m 3 ), was built for the Navy in Germany and delivered to the United States in 1924. It continued in service until 1932.
The Akron , a 785–foot (239–m) rigid dirigible, was commissioned by the Navy in 1931. At the time it was the world's largest airship, having a capacity of 6,500,000 cubic feet (184,000 m 3 ). After a number of voyages, it was destroyed during a thunderstorm in 1933. Of the 77 persons aboard, 73 were killed. The Macon, sister airship to the Akron, was completed in 1933 and came down in the Pacific Ocean in 1935. Only two of its crew were lost.
German Rigid DirigiblesIn 1925, the Allies permitted Germany to resume construction of long-range rigid dirigibles for their own use. Under Dr. Hugo Eckener, the Zeppelin Construction Works completed the Graf Zeppelin, with a capacity of 3,700,000 cubic feet (105,000 m 3 ), in 1928. The airship made many transoceanic flights with a special service between Germany and Brazil. It flew around the world in 1929.
A new and larger Zeppelin, the Hindenburg, was completed in 1936. It had a capacity of 7,000,000 cubic feet (198,000 m 3 ), but, like other German airships, used highly flammable hydrogen gas. (Only the United States has an adequate supply of helium for airships.) After 141 successful transatlantic flights, the Hindenburg was destroyed by fire following an explosion as it arrived at Lakehurst, New Jersey, May 6, 1937. Of the 97 people aboard, 35 died.