Essay on Airships

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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...