Airship

Airship is a lighter-than-air aircraft with an engine that moves it through the air. Airships also normally have equipment for steering. The main body of a typical airship used today is a huge, cigar-shaped balloon filled with a lighter-than-air gas. The gas raises the craft and keeps it aloft.

An airship differs from a free-floating balloon, which is neither powered nor steered. Airships also differ from helicopters and airplanes, which are heavier than air. Helicopters and airplanes use their engines and blades or wings to lift them and keep them aloft.

Airships were introduced in the 1800’s as the first flying machines capable of prolonged flight and of being steered. This feature led to the craft being called dirigibles, which comes from the Latin word dirigere, meaning to direct. In World War I (1914-1918), airships were used as bombers, for protecting ships against submarine attack, and for other duties. Before and after the war, they were used to carry passengers. Airship passenger services reached their height in the 1930’s, but a series of disastrous crashes and the increasing popularity and long-range capability of the airplane brought airship passenger services to an end. Today, several countries have shown a renewed interest in airships for advertising, cargo operations, passenger support, recreational flying, and surveillance.

Types of airships

There are three main types of airships: (1) nonrigid airships, (2) rigid airships, and (3) semirigid airships.

Nonrigid airships

were the first airships and are the most popular type today. They have no major internal structures and no outer framework. Gas pressure causes the outer skin, called the envelope, to keep its shape. Modern envelopes are made of synthetic materials.

The smallest airships have been nonrigid craft. Some have measured less than 75 feet (23 meters) long. The largest nonrigid airships were the United States Navy’s ZPG-3W airships. These craft were flown from 1958 to 1962 and were used for airborne early-warning duties. Each ZPG-3W measured about 403 feet (123 meters) long. Today’s nonrigid airships average about 150 feet (46 meters) in length. They cruise at approximately 35 to 40 miles (56 to 65 kilometers) per hour at heights reaching about 10,000 feet (3,050 meters).

The U.S. Navy’s B-class nonrigid airships, built in 1917, gave rise to the term blimp for nonrigid craft. The term came from B-nonrigid, or B-limp.

Rigid airships,

the largest airships, have a greater carrying capacity than nonrigid craft. But few are flown today. The main body of a rigid airship is called the hull. Most early rigid craft had a hull consisting of a wooden or metal framework that supported the outer skin. Today, composite materials can be used. The most famous rigid airships were called zeppelins, after Count Ferdinand von Zeppelin, a German airship pioneer.

Zeppelins were cigar-shaped and ranged from about 400 feet (120 meters) to over 800 feet (240 meters) long. Advanced models could reach speeds of about 80 miles (130 kilometers) per hour. Inside the hulls were several compartments, called gas cells, that held the lifting gas. Many hulls contained corridors along which cargo, crew quarters, and the fuel tanks were located.

Semirigid airships

became fairly common in the early 1900’s. They often resembled nonrigid ships, except that a support ran along most of the length of the envelope and helped maintain its shape and distribute loads. Semirigid airships were often larger than nonrigid craft, but they faded in the 1920’s because of the increased capabilities of nonrigid and rigid models.

How airships fly

Lift

is the force that raises an airship off the ground and keeps it aloft. Airships generate lift because the gas they contain has a lower density than the air outside the craft. Airships hold enough of this lighter-than-air gas to overcome their own weight and rise from the ground.

Early airships contained hydrogen, the lightest of all gases. But hydrogen is highly flammable, which was an important factor in a number of airship disasters. As a result, helium replaced hydrogen for use in airships.

Thrust

is the force that moves an airship through the air. Most airships use engines and propellers to obtain thrust. On large rigid airships of the early 1900’s, the engines and propellers were in gondolas (cars) attached to the hull. Such craft had separate gondolas for the passengers and crew. On most nonrigid and semirigid airships, engines are mounted on a gondola that also holds the crew and passengers.

Control.

Most airships have tail structures that include fins, rudders, and elevators. Fins are large, fixed surfaces. Typically, four fins are set equally distant from one another around the ship’s stern (rear). The smaller, movable rudders and elevators are surfaces attached to the fins. A pilot moves the rudders to steer and the elevators to raise or lower the ship’s nose.

For improved control, many early airships carried weight called ballast, usually water. If rain or other weather conditions made the craft heavier in flight, the pilot could release ballast to lighten the craft and thus maintain altitude. Some modern airships carry ballast.

Ballonets

are air-filled bags or compartments inside the envelope of nonrigid and semirigid craft. Ballonets help maintain the shape of the envelope. If gas pressure in the envelope decreases, air is pumped into the ballonets so that the envelope will not sag. Ballonets can also be used to stiffen the envelope of a rigid airship.

Storage.

Early airships were kept in huge hangars or sheds, but moving the craft in and out of these shelters sometimes proved disastrous. Engineers partly solved the problem when they developed the mooring mast, a high, stable tower to which an airship could be anchored without touching the ground. The bow of the airship was secured to the tower. Mooring masts allowed airships a limited amount of movement to help them survive high winds. To enter rigid craft, the crew and passengers passed up a staircase within the mast.

Low mooring masts were developed to secure nonrigid airships close to the ground. The crew and passengers can board these craft directly into the gondola. Some modern airships do not require masts at all.

History

The first airships

evolved from balloons. Henri Giffard, a French engineer, built and piloted the first powered airship. As with many balloons, ropes covered the envelope and hung down to support an open gondola. But unlike the ball-shaped balloons, Giffard’s airship was cigar-shaped, and the gondola supported a 3-horsepower (2.2-kilowatt) steam engine. A saillike rudder was carried in the gondola.

On Sept. 24, 1852, Giffard flew his craft about 17 miles (27 kilometers) from Paris to Trappes, near Versailles, at an average speed of 5 miles (8 kilometers) per hour. The small rudder and engine enabled him to alter his course, but the craft was not properly steerable.

In 1884, Charles Renard and Arthur Krebs, two French inventors, completed La France. This airship had a battery-powered electric motor that produced about 9 horsepower (7 kilowatts). It also had an efficient rudder and elevator. Renard and Krebs flew La France around a 5-mile (8-kilometer) circular course near Paris at speeds over 14 miles (23 kilometers) per hour. In 1901, the Brazilian-born inventor Alberto Santos-Dumont completed a controlled journey around the Eiffel Tower in Paris. His adventures won him great popularity.

David Schwarz of Austria designed the first truly rigid airship. His craft flew on Nov. 3, 1897. But due to windy conditions, mechanical problems, and an inexperienced pilot, the craft crashed.

The zeppelins.

In 1900, Count Ferdinand von Zeppelin flew his first airship, the LZ-1. It was 420 feet (128 meters) long and could reach a top speed of about 17 miles (27 kilometers) per hour. It made only three flights because it was underpowered and lacked proper control. Zeppelin completed the LZ-2 in 1905, and he launched the LZ-3 in 1906. The German Army later made the LZ-3 the first military zeppelin.

In 1909, Zeppelin helped establish the world’s first commercial airline, known as DELAG. The Deutschland, DELAG’s first airship, was over 485 feet (148 meters) long and had three 120-horsepower (90-kilowatt) engines. From 1910 to 1913, over 34,000 passengers paid to fly by zeppelin airships on DELAG flights.

World War I.

During World War I, Germany used zeppelins and other airships to patrol the North Sea and scout enemy craft and positions. In addition, Germany was the only country to make large-scale use of rigid airships for strategic bombing. But the frequent raids over England caused little damage. The largest user of rigid airships during the war was the German Naval Airship Division. It received about 70 zeppelin and Schutte-Lanz craft. Due to accidents, bad weather, and enemy fire, 53 of these airships were lost. The capabilities of zeppelins, however, improved dramatically. For example, the L-59 once flew 4,200 miles (6,800 kilometers) nonstop. Its five engines could produce speeds of over 60 miles (95 kilometers) per hour.

The United Kingdom built and operated a large number of nonrigid airships during the war. British airships primarily protected ships from submarine attack. The United States used nonrigid airships for some overwater patrol duties and antisubmarine warfare. Other countries that used airships during the war included France and Italy.

Between world wars.

After World War I, airships became bigger, faster, and stronger. For example, in 1919, the United Kingdom’s rigid R-34 made the first transatlantic crossing by an airship. In 1926, the Italian-built semirigid Norge became the first airship to fly over the North Pole. The replacement of hydrogen with helium to prevent airship disasters began in the 1920’s, on U.S. craft.

In the 1920’s and 1930’s, the U.S. Navy experimented with giant rigid airships. The Akron, launched in 1931, and the Macon, launched in 1933, carried fighter airplanes. While in flight, these airships could launch and receive the planes. In April 1933, the Akron went down in a storm off the coast of New Jersey, killing 73 people. In February 1935, bad weather forced the Macon into the sea off the coast of California, killing two people and ending U.S. construction of rigid airships.

The most successful rigid airship ever built was the German LZ-127 Graf Zeppelin. Between 1928 and 1937, it flew more than 1 million miles (1.6 million kilometers) and carried over 13,000 passengers, many of them overseas. In August 1929, it made the first airship flight around the world. The Graf Zeppelin ranks among the fastest rigid airships ever flown.

The Hindenburg.

Construction and operation of rigid airships in Germany came to a swift end following the destruction of the Hindenburg. One of the largest airships ever built, the Hindenburg was about 804 feet (245 meters) long and 135 feet (41 meters) wide. It had a volume of 7,062,100 cubic feet (199,980 cubic meters) and cruised at 78 miles (126 kilometers) per hour. On May 6, 1937, while approaching its docking in Lakehurst, New Jersey, the Hindenburg exploded. Of the 97 people on board, 35 were killed. In addition, one member of the ground crew was killed. The ship’s envelope material and hydrogen gas had ignited, leading to an explosion. The Hindenburg disaster marked the end of the use of airships for regular passenger services. In addition, development of rigid airships ended.

World War II to the present.

The evolution of the airplane contributed greatly to the decreased use of the military nonrigid airship during World War II (1939-1945). The U.S. Navy made the only significant use of nonrigid airships during the war, flying mainly its K-class airships. Most of these craft patrolled U.S. coastal waters and escorted surface ships there.

In the late 1950’s, the Navy introduced its ZPG-3W nonrigid airships. One ZPG-3W craft crashed at sea in 1960, killing nearly everyone on board. This crash contributed to ending the use of nonrigid airships for military operations.

Today, there has been a significant revival of airships. Most airship companies produce nonrigid craft for commercial and recreational purposes. Manufacturers also design and build large rigid airships for passenger and heavy cargo operations, and small rigid airships for commercial use. Other companies have created hybrid craft that rely on modified wings or other devices to help produce lift in addition to that provided by gas.