|
an aircraft that consists of a
cigar-shaped gas bag, or envelope, filled with a lighter-than-air
gas to provide lift, a propulsion system, a steering mechanism, and
a gondola accommodating passengers, crew, and cargo. All extensions,
like the fins and the gondola/control car, are attached to the
envelope; the propellers are attached to the gondola/control
car.
Soon after the hot-air balloon
was invented in 1783, attempts began to control the balloon's
flight. Although sails, paddles, and flapping wings were tried,
propellers proved to be the most suitable form of propulsion. The
French inventor Henri Giffard built a steam-power-driven airship as
early as 1852. However, it was not until the invention of the
gasoline engine in 1896 that airships became practical, and in 1898
the Brazilian Alberto Santos-Dumont
was the first to construct and fly (1898) a gasoline-powered
airship.
For more than a century the principal
lighter-than-air gas for both balloons and airships was hydrogen,
the lightest of the elements, despite its being highly dangerous
because of its extreme flammability. Helium (which although somewhat
inferior to hydrogen in lifting strength will not burn or explode)
began to be used in the United States in 1917, when a means of
extracting it cheaply in large quantities from the natural gas in
which it is found was developed. Helium was subsequently adopted as
the preferred gas worldwide.
There are three types of airships. In a
nonrigid airship, also known as a blimp, the shape of the gas bag is
maintained by the internal pressure of the enclosed gas. In a
semirigid airship, also known as a keel-airship, internal gas
pressure acts in conjunction with a longitudinal keel to maintain
the form of the gas bag. In a rigid airship, the form of the gas bag
is determined by a rigid framework, usually made of aluminum or a
special aluminum alloy called Duraluminium; the framework is formed
of longitudinal girders and cross-rings, also made of girders. The
whole structure is covered with fabric for aerodynamic purposes. The
rigid airship is often called a zeppelin in honor of its inventor,
Count Ferdinand von Zeppelin.
It is also often referred to as a dirigible, a shortening of
dirigible balloon, from the French ballon dirigeable, meaning
steerable lighter-than-air craft.
In 1910 the rigid Deutschland
became the world's first commercial airship. Between 1910 and the
beginning of World War I in 1914, German zeppelins flew 107,208
miles and carried 34,028 passengers and crew entirely without
injury. During World War I, the Germans used rigid airships on both
the Eastern and Western Fronts as bombers although airships never
became effective offensive weapons. Airships did excel as defensive
weapons, and the British used nonrigid airships to patrol their
coasts and rigid airships for convoy protection. The U.S. navy
operated nonrigid aircraft during the war, as did the French and
Italian armies and navies. The U.S. navy continued operating
nonrigid airships during and after World War II, the only service in
the world to do so. In addition to convoy protection, the airships
conducted search-and-rescue, photographic, and mine-clearing
missions.
Rigid airships rose to the peak of their
commercial success between World War I and World War II. The
best-known rigid airships were the Graf Zeppelin, which
traveled 20,000 mi (32,000 km) around the world in 1929; England's
R34, which crossed the Atlantic in 1919; and the
Hindenburg, which burst into flames while preparing to dock
at Lakehurst, N.J., in 1937, killing 36 people. No rigid airship was
built from the 1930s through the late 1990s.
In 1997 the Zeppelin NT, which uses
modern technologies and design innovations to realize a more
maneuverable and efficient airship, made its maiden flight and
testing began in the hope of putting rigid airships into commercial
service once again. The airship, renamed the Bodensee, began
tourist flights over Lake Constance in 2001. All of the other
airships flying today are of the nonrigid variety. No nonrigid
airships are used to carry passengers or cargo; they serve a number
of utilitarian functions such as military surveillance, flashing
advertising messages, and providing "bird's eye" television images
of sporting events.
See L. Gerken, Airships, History and
Technology (1990); H. G. Dick and D. H. Robinson, The Golden
Age of the Great Passenger Airships (1992); D. H. Robinson,
The Zeppelin in Combat: A History of the German Naval Airship
Division, 1912–1918 (1993); W. A. Althoff, Sky Ships: A
History of the Airship in the United States Navy (1998); G. H.
Khoury and J. G. Gillette, ed., Airship Technology
(1999). ____________________
The Columbia Encyclopedia, Sixth
Edition Copyright© 2004, Columbia University Press. Licensed from
Lernout & Hauspie Speech Products N.V. All rights
reserved.
-923- |
