Download скачати - Essays, term papers, dissertation, diplomas

Airships Essay, Research Paper
Airships
INDEX
PROLOGUE 2
TYPES OF AIRSHIP 2
RIGID AIRSHIP 2
NONRIGID AIRSHIP 3
HISTORY OF RIGID AIRSPS 3
HISTORY OF NONRIGID AIRSHIPS 4
AIRSHIPS TODAY 5
HINDENBURG 6
HINDENBURG DISASTER 7
PROLOGUE
An airship is a type of lighter-than-air aircraft with propulsion and steering
systems, it is used to carry passengers and cargo. It obtains its buoyancy
from the presence of a lighter-than-air gas such as hydrogen or helium. The
first airship was developed by the French, called a ballon dirigible, it could
be steered and could also be flown against the wind.
TYPES OF AIRSHIP
Two basic types of airship have been developed: the rigid airship, the shape of
which is fixed by its internal structure; and the nonrigid blimp, which depends
on the pressure created by a series of air diaphragms inside its gas space to
maintain the shape of its fabric hull. Inventors sought to combine the best
features of these models in a semirigid type, but it met with only limited
success. Today only the nonrigid airship is used.
Rigid Airship
The rigid airship’s structure resembled a cage that enclosed a series of
balloons called gas cells. These cells were tailored to fit the cylindrical
space and were secured in place by a netting that transmitted the lifting force
of their gas to the structure. Each gas cell had two or more valves, which
operated automatically to relieve pressure when the gas expanded with altitude,
the valves could also be operated manually so that the pilot could release gas
whenever desired.
Also on board was a ballast system that used water as ballast. On the ground
this ballast served to make the airship heavier than air. When part of it was
released, the airship ascended to a cruising altitude where the engines supplied
propulsion, and further ballast could be released to gain more altitude. As fuel
was consumed, the airship became lighter and tended to climb. This was
countered in hydrogen-inflated airships by simply releasing gas into the
atmosphere.
The method was uneconomical, however, with helium-inflated airships, and they
were therefore equipped with ballast generators, apparatuses that condensed
moisture out of the engines’ exhaust gases to compensate for fuel that was
consumed. But this ballast-generating equipment was expensive, complex, heavy,
and difficult to maintain and was thus one of the most serious disadvantages of
airships filled with the safer but more expensive helium.
Nonrigid Airship
In contrast to the rigid airship, the nonrigid blimp has no internal structure
to maintain the shape of its hull envelope, which is made of two or three plies
of cotton, nylon, or dacron impregnated with rubber for gas tightness. Inside
the gas space of the hull are two or more air diaphragms called ballonets that
are kept under slight pressure, either by blowers or by air that is forced
through scoops as a result of the forward motion (ram effect). The ballonets in
turn exert pressure upon the gas, which fills the envelope, and this pressure in
turn serves to stiffen the shape of the envelope and create a smooth flying
surface. On takeoff the ballonets are almost fully inflated, but as the airship
gains altitude and the gas expands, air is bled from the ballonets while a
constant pressure is maintained throughout the envelope. When the gas contracts
upon descent, air is pumped back into the ballonets.
HISTORY OF RIGID AIRSHIPS
The German company Luftschiffbau Zeppelin had the most success in building rigid
airships. The first Zeppelin was flown on July 2, 1900; it was 419 ft long, 38
ft in diameter, contained 338,410 cu ft of hydrogen gas in 16 cells, and was
powered by two 16-hp engines. Its range and payload were negligible. The last
Zeppelin was the Graf Zeppelin II, which was first flown on Sept. 14, 1938; it
was 803 ft long, 135 ft at maximum diameter, contained 7,062,100 cu ft of
hydrogen, and was powered by four 1,050-hp Daimler Benz diesel engines. It
could carry loads of 30 tons over transoceanic distances. It was scrapped in
May 1940.
A total of 119 Zeppelins were built, most of them during World War I, when 103
airships were delivered to the military. The most famous Zeppelin was the
original GRAF ZEPPELIN, which during 1928-37 made flights to the United States,
the Arctic, the Middle East, and South America; it also made one flight around
the world. Another famous Zeppelin was the airliner hindenburg, which was
destroyed by fire at Lakehurst, N.J., on May 6, 1937.
The British made intermittent efforts to develop the rigid airship; they built
eight during World War I and six shortly thereafter. The most noteworthy was
the R-34, which in July 1919 made the first transatlantic round-trip flight. An
effort to develop two airships of 5,000,000 cu ft for intercontinental air
service came to grief in October 1930 when the R-101 crashed and burned in
France. The R-100, which had made a successful flight to Canada earlier in the
year, was subsequently scrapped. In the United States, the development of rigid
airships was undertaken by the navy, and only five were operated. The navybuilt ZR-1 SHENANDOAH made its first flight on Sept. 4, 1923, and was torn to
pieces by a thunderstorm over southern Ohio on Sept. 3, 1925. The ZR-2 was
procured in England but crashed on Aug. 24, 1921, before it could be delivered
to the United States. The ZR-3 Los Angeles, built in Germany by Luftschiffbau
Zeppelin, made its transatlantic delivery flight during Oct. 11-15, 1924; it
was flown successfully until decommissioned in 1931 and was scrapped in early
1940. The ZRS4 and ZRS5 AKRON AND MACON were built by the Goodyear-Zeppelin Co.
of Akron, Ohio. These 6,500,000-cu ft sister ships were 785 ft long and 133 ft
at maximum diameter, and were powered by eight 560-hp Maybach engines. Their
design was unique in that it provided for an internal space for five airplanes
that could be launched and retrieved while the airships were in flight. The
Akron first flew on Sept. 23, 1931 and was lost in a storm over the Atlantic on
Apr. 4, 1933; the Macon first flew on Apr. 21, 1933, and crashed in the Pacific
on Feb. 12, 1935.
HISTORY OF NONRIGID AIRSHIPS
The first successful nonrigid airships were built by the French. In 1852 Henri
Giffard built an airship of 113,000 cu ft powered by a steam engine. The
brothers Albert and Gaston Tissandier constructed a 37,500-cu ft airship
propelled by a battery-powered electric motor in 1883, and the following year
Charles Renard and Arthur C. Krebs built the 66,000-cu ft La France, which also
used electric power. At the turn of the century the Brazilian aeronaut Alberto
Dumont built and flew a series of small airships in France, all of which used
gasoline engines. Blimps were effectively used by the British and French in
World War I in maritime reconnaissance against German submarines. The term
blimp, a British slang expression of unknown origin, came into use about this
time.
In World War II, the United States was the only power to use airships. The navy
used them for minesweeping and antisubmarine patrols. Its more than 150 blimps
were operated from bases on the east and west coasts, the Gulf of Mexico, the
Caribbean, and as far south as Brazil. The workhorse of these forces was the Ktype blimp, 253 ft long, 60 ft in diameter, containing 456,000 cu ft of gas, and
powered by two 425-hp engines that gave a top speed of 50 mph. Blimps are not
fast, but whereas an airplane can remain airborne for only a few hours, a K-ship
could stay aloft for 60 hours. In 1944, six K-ships flew across the Atlantic to
Morocco, where they established a low-altitude antisubmarine barrier across the
Strait of Gibraltar; later they operated from bases at Cuers, France, and Pisa,
Italy.
AIRSHIPS TODAY
The most long-lasting use of airships has been by the Goodyear Tire and Rubber
Company. The Pony was built in 1919 and the Pilgrim in 1923. After 1928 the
fleet was expanded with the Puritan, Volunteer, Mayflower, Vigilant, Defender,
Reliance, Resolute, Enterprise, Ranger, and Columbia. During the 1930s these
airships were used for advertising, and they barnstormed all over the United
States. During World War II, the fleet was used for reconnaissance by the U. S.
Navy. Three Goodyear blimps still operate, the newest, the Spirit of Akron,
which was launched in 1989, was for a short time the world’s largest operating
airship 205.5 ft, with a volume of 248,000 cu ft.
Goodyear no longer builds blimps, but other companies continue to produce and
operate the craft. Among new types are the smaller blimps, some remotecontrolled, that are tethered inside stadiums and used to provide television
audiences with bird’s-eye views of sports events.
In 1991, Westinghouse Airships launched the 220-ft long Sentinel 1000, the first
in a projected series of blimps to be used by the U. S. Defense Department for a
range of surveillance, communications, and patrol duties. The envelope of the
Sentinel 1000 is made of a mix of synthetic fibers that is impervious to weather
and almost invisible to radar.
Data collected in flight tests will aid in the development of the much-larger
Sentinal 5000. Twice the length of the Sentinal 1000, its envelope will be
seven times larger, with a 2.5 million-cu ft helium-gas capacity. It will carry
an 25,000-lb payload, including a 3-story, pressurized gondola, a crew of 15,
and extensive radar arrays and optical flight control systems. The craft will
be refuelable while it is under way, with refueling lines carried to it by the
ship-based helicopters. It will be launched in 1997.
HINDENBURG
The Hindenburg, originally designated the L. Z. 129, was a rigid airship built
by the firm of Luftschiffbau Zeppelin in Friedrichshafen, Germany. Completed
and tested in 1936, it was the world’s first transatlantic commercial airliner.
The airship was 804 ft long, had a maximum diameter of 135 ft, and was kept
aloft by 7,000,000 cu ft of hydrogen in 16 cells. Four 1,050-hp Daimler-Benz
diesel engines provided a top speed of 82 mph. In May 1936 the Hindenburg
inaugurated the first scheduled air service across the North Atlantic, between
Frankfurt am Main, Germany, and Lakehurst, N.J. It accommodated more than 70
passengers and had a dining room, a library and lounge with a grand piano, a
cocktail lounge, and promenades with large windows. The flight to the United
States took 60 hours, and the return trip to Europe, 50 hours. In 1936 the
Hindenburg carried more than 1,300 passengers and several thousand pounds of
mail and cargo on transatlantic flights.
While maneuvering to land at Lakehurst on May 6, 1937, the airship’s hydrogen
was ignited and the Hindenburg was destroyed by the resulting fire. Thirty-five
of the passengers and crew died, along with one member of the ground crew.
Claims and speculation that the Hindenburg was a victim of sabotage have never
been supported by evidence. The destruction of the Hindenburg marked the end of
the use of airships in world air commerce.
http://ua-referat.com