Airship

Background

An airship is a large lighter-than-air gas balloon that can be navigated by using engine-driven propellers. There are three types of airships: rigid (has an internal metal frame to maintain the envelope's shape); semi-rigid (rigid keels run the length of the envelope to maintain its shape); and non-rigid (internal pressure of the lifting gas, usually helium, maintains the envelope's shape). This essay focuses on non-rigid airships (commonly called blimps) because they are the primary type of airship in general use today.

History

The history of airships begins, like the history of hot air balloons, in France. After the invention of the hot air balloon in 1783, a French officer named Meusnier envisioned an airship that utilized the design of the hot air balloon, but was able to be navigated. In 1784, he designed an airship that had an elongated envelope, propellers, and a rudder, not unlike today's blimp. Although he documented his idea with extensive drawings, Meusnier's airship was never built.

In 1852, another Frenchman, an engineer named Henri Giffard, built the first practical airship. Filled with hydrogen gas, it was driven by a 3 hp steam engine weighing 350 lb (160 kg), and it flew at 6 mi/hr (9 km/hr). Even though Giffard's airship did achieve liftoff, it could not be completely controlled.

The first successfully navigated airship, La France, was built in 1884 by two more Frenchman, Renard and Krebs. Propelled by a 9 hp electrically-driven airscrew, La France was under its pilots' complete control. It flew at 15 mi/hr (24 km/hr).

Military airships

In 1895, the first distinctly rigid airship was built by German David Schwarz. His design led to the successful development of the zeppelin, a rigid airship built by Count zeppelin. The zeppelin utilized two 15 hp engines and flew at a speed of 25 mi/hr (42 km/hr). Their development and the subsequent manufacture of 20 such vessels gave Germany an initial military advantage at the start of World War I.

It was Germany's successful use of the zeppelin for military reconnaissance missions that spurred the British Royal Navy to create its own airships. Rather than duplicating the design of the German rigid airship, the British manufactured several small non-rigid balloons. These airships were used to successfully detect German submarines and were classified as "British Class B" airships. It is quite possible this is where the term blimp originates—"Class B" plus limp or non-rigid.

Passenger-carrying airships

During the 1920s and 1930s, Britain, Germany, and the United States focused on developing large, rigid, passenger-carrying airships. Unlike Britain and Germany, the United States primarily used helium to give their airships lift. Found in small quantities in natural gas deposits in the United States, helium is quite expensive to make; however, it is not flammable like hydrogen. Because of the cost involved in its manufacture, the United States banned the exportation of helium to other countries, forcing Germany and Britain to rely on the more volatile hydrogen gas. Many of the large passenger-carrying airships using hydrogen instead of helium met with disaster, and because of such large losses of life, the heyday of the large passenger-carrying airship came to an abrupt end.

The first passenger-carrying non-rigid airship was invented in 1898 by Alberto Santos Dumount, a citizen of Brazil living in Paris. Under a sausage-shaped balloon with a ballonet or collapsible air bag inside, Dumount attached a propeller to his motorcycle's engine. He used both air and hydrogen, not helium, to lift the blimp.

The non-rigid airship of the 1940s and 1950s

After the rigid airship disasters of the 1920s and '30s, the United States as well as other countries refocused their attention on the non-rigid airship as a scientific/military tool. Aerial surveillance became the most common and successful use of the blimp. In the 1940s and '50s, blimps were used as early warning radar stations for merchant fleets along the eastern seaboard of the United States. They were also used and are still used in scientific monitoring and experiments.

Although as a company it no longer makes airships, Goodyear is a name sononymous with the manufacture of blimps. During the first half of the twentieth century, Goodyear manufactured over 300 blimps, more than any other airship manufacturer. Goodyear blimps were primarily used by the U.S. Army and Navy for aerial surveillance.

Modern resurgence of the non-rigid airship

Today, non-rigid airships are known more for their marketing power than for their surveillance capabilities. Blimps have been used commercially in the United States since about 1965. Advertising blimps measure about 150,000 cu ft (4,200 cu m). Since blimps can hover over one space and can be viewed over a large expanse with very little noise disturbance, they are excellent mediums for advertising at large outdoor events.

The use of the night billboard on blimps has been quite an advertising fad. The sign is a matte of multicolor incandescent lamps permanently fixed to the sides of the airship envelope, and it can be programmed to spell out different messages. Originally, the signs were developed by electromechanical relay. Now they are stored on magnetic tape, developed by composing equipment on the ground, which are fed into an airborne reader. The taped information is played back through a computer to the lamp driver circuits. The displayed messages can be seen over long distances. In the late 1980s, the use of blimps in advertising exploded. Its popularity does not seem to have let up.

Raw Materials

The envelope is usually made of a combination of man-made materials: Dacron, polyester, Mylar, and/or Tedlar bonded with Hytrel. The high-tech, weather-resistant plastic film is laminated to a rip-stop polyester fabric. The envelope's fabric also protects against ultraviolet light. Usually the envelope is smaller than the bladder to ensure that the envelope takes the load when the blimp is fully inflated. The bladder is made of a thin leak-resistant polyurethane plastic film.

Ballonets are usually made of a fabric lighter than the envelope's because they only retain gas tightness and do not have to withstand normal main envelope pressures. Air scoops channel air to the ballonets.

Blimps obtain much of their lift from lighter-than-air gases, most commonly helium, inside the envelope.

Most of the metal used on the blimp is riveted aircraft aluminum.

Earlier cars were fabric-covered tubing framework. Today's gondolas are made of metal monocoque design.

The nose cone is made of metal, wood, or plastic battens, laced to the envelope.

Design

The main body of the blimp is made up of an inner layer, the bladder, and an outer layer, the envelope. The bladder holds the helium. Because the bladder is not resistant to punctures, it is protected by the envelope.

Inside the envelope are catenery curtains, which support the weight of the car by distributing the loads imposed by the airship into the fabric of the main envelope. Catenery curtains all consist of cable systems attached to the car, which terminate in the fabric curtains.

The envelope's shape is maintained by regulating internal pressure of helium gas inside. Within the bladder are one or more air cells/balloons called ballonets. These are filled with air (as opposed to the rest of the bladder which is filled with helium) and are attached to the sides or bottom of the blimp. The ballonets expand and contract to compensate for changes in helium volume due to varying temperature and altitude. The pilot has direct control of the ballonets via air valves.

The nose cone serves two purposes. It provides the point of attachment for mast mooring and adds rigidity to the nose (which encounters the greatest dynamic pressure loads in flight). On the ground, the inflated blimp is secured to a stationary pole called the mooring mast. The rigid nose dish is attached to the mooring mast. The secured blimp can move freely around the mast with wind changes. There are nose lines attached to the nose dish used by the ground crew to maneuver blimp during takeoffs and landings.

Airship tail surfaces come in three configurations: the cruciform (+), the X, and the inverted Y. These tails are made up of a fixed main surface and a controllable smaller surface on the aft end. These surfaces weigh only 0.9 lb per sq ft (4.4 kg per sq m). Tail fins control flight direction. They are anchored at the rear of the ship and are supported by guide wires. The elevators and rudders also help to guide the blimp's movement and are mounted to the fin's edges with hinges.

The airship car, or gondola, is similar to conventional aircraft construction. The gondola contains a number of lead shot bags which are constantly adjusted based on the crew's analysis. The gondola is attached to the blimp by either an internal load curtain or externally, by being attached to envelope sides.

Inside the gondola, there a series of controls: the overhead control panel containing controls for communications, fuel, and electrical systems; throttles to regulate engine speed and propeller pitch controls to regulate angles at which propeller blades "bite" the air; fuel mixture and heat controls to regulate the degree to which fuel is mixed with air in engine; temperature controls to prevent icing; envelope pressure controls to regulate helium and ballonet air pressure; communication equipment; main instrument panel; rudder pedals to control right/left direction of blimp; elevator wheels to control up/down direction of blimp; navigational instruments; and color weather radar.

The Manufacturing
Process

Envelope

• 1 The envelope is made of patterns of fabric panels. Two or three plies of cloth are impregnated with an elastomer. One of these plies is placed in a bias direction with respect to others. The pieces of the envelope can be put together in a number of ways. They can be cemented and sewn together, or heat-welded (heat-sealed).
• 2 The outside of the envelope is coated with aluminized paint for protection against sunlight. The envelope will have the required shape when filled with gas.
• 3 The catenery curtains are attached on to the main envelope proper in a similar manner.
• 4 The bladder is formed from strips that are welded together.
• 5 The tail construction consists mostly of lightweight metal structural beams covered with doped fabric. They are held to the envelope by cables which distribute the load into fabric patches cemented or heat-welded to the envelope proper. They are not directly attached to the envelope in the manufacturing process, but put on when the blimp is inflated.

Gondola

• 6 The frame of the gondola is made of material similar to the tail construction, covered with doped fabric.

Inflation

The erection of the blimp takes only a short amount of time. (The following is only one method of inflation. There are variations on this method.)

• 7 The envelope is spread out on the floor of the airship hangar, with a net placed over it. This net is held down by sandbags. Gas is fed into the enveloped from tank cars each containing 200,000 cu ft (5,700 cu m) of 99.9% pure helium compressed to 2100 psi (14.5 megapascals). The net is allowed to slowly rise, with the envelope underneath it.
• 8 Fins, nose cone, battens, air valves, and helium valves are attached while the envelope is still near the ground. After these parts are attached, the envelope is allowed to rise high enough to permit rolling the gondola underneath it. After the gondola is attached, the net is removed and the airship is rigged for flight.

Shipping

• 9 When transported, the uninflated fabric envelopes can be folded, shipped, and stored in a space that takes up less than 1% of its inflated volume. This feature makes the non-rigid airship more practical than a rigid one.

Quality Control

A blimp requires a big crew, especially on the ground. Pilots must be certified in planes or helicopters and undergo special lighter-than-air pilot training. The FAA requires a separate license to command a blimp. As of 1995, there were only about 30 active blimp pilots in the world. Many blimps require 24-hour monitoring. The envelope and ballast are checked every hour to make sure the proper equilibrium is maintained.

The Future

Propulsive efficiency will be improved by using lightweight, two-stroke aviation diesel engines, gas turbines, or solar energy. New bow and stem thrusters will be developed to improve maneuverability. New lightweight plastics might change the hull design. More lightweight, high strength materials will probably be developed and inevitably improve the overall design and function of the airship. The Pentagon and the U.S. Navy have renewed interested in developing blimps for various defense, missile surveillance, radar-surveillance platforms, and reconnaissance purposes.

Where to Learn More

Books

Botting, Douglas, et al. The Giant Airships. Time-Life Books, 1980.

Ventry, Lord and Eugene M. Kolesnik. Airship Saga: The history of airships seen through the eyes of the men who designed, built and flew them. Blandford Press, 1982.

—AnnettePetrusso

DIRIGIBLES

DIRIGIBLES, or motor-driven lighter-than-air craft that can be flown against the wind and steered, were first constructed in America by Caesar Spiegler. His first dirigible made its maiden flight 3 July 1878, with the great American balloonist John Wise as its pilot. Thomas Scott Baldwin built the first dirigible for the government; it was 96 feet long and had a 20-horsepower engine built by Glenn H. Curtiss. Called the SC-1, it made its first flight at Fort Myer, Virginia, in August 1908.

When the United States entered World War I, the U.S. Navy ordered sixteen dirigibles of the nonrigid type. Developed from a British model the Royal Navy used for antisubmarine patrols, U.S. Navy personnel who had been positioned in England used the English nickname for the nonrigid airship—"blimp"—and the term subsequently came into common usage in the United States. By the end of the war the navy had twenty "B-type" blimps (77,000–84,000 cubic feet; single engine) and ten "C-type" blimps (182,000 cubic feet; twin engine). In 1919 the navy airship C-5 failed in its attempt to fly across the Atlantic, but nevertheless set a 1,177-mile nonstop distance record between Montauk, New York, and Saint John's, Newfoundland, where it was destroyed in an accident.

In 1917 an army-navy joint board delegated to the navy the development of the much larger and more complex rigid airship, and in July 1919 Congress authorized the procurement of two rigid airships, one to be built in the United States and the other to be purchased abroad. The army transferred the site of Camp Kendrick, a military facility near Lakehurst, New Jersey, to the navy, which erected a huge hangar, mooring mast, and other facilities there. The Lakehurst Naval Air Station came into commission in 1921, and for the next forty-one years it was the center of American lighter-than-air aeronautics.

As the navy began the development of rigid airships, the army also began to operate dirigibles, concentrating on the semirigid type and blimps. In 1921 the army purchased the Italian semirigid T-34 airship named Roma, 412 feet long, having a gas volume of 1.2 million cubic feet, and powered by six 400-horsepower Anasaldo engines. As it had been shipped to the United States disassembled, army engineers erected it at Langley Field, Virginia, where it made its first American flight on 21 November 1921. During a trial flight with new Liberty engines on 21 February 1922 the Roma went out of control and flew into a high voltage electrical transmission line. Being inflated with hydrogen, the Roma went up in flames and crashed, killing thirty-four of the forty-five men aboard. In 1922 the army airship C-2 made the first coast-to-coast flight achieved by a lighter-than-air craft. And on 15 December 1924, a Sperry Messenger airplane equipped with a skyhook hooked onto a trapeze hung from the blimp TC-3, demonstrated the possibility of the airship's becoming an aircraft carrier. In 1925 the army procured the semirigid RS-1, fabricated by the Goodyear-Zeppelin Corporation and erected by the army's center of lighter-than-air aeronautics at Scott Field, Illinois. The RS-1 made its first flight on 9 January 1926, and although its project engineers hoped to develop it into an airplane carrier, they never conducted appropriate experiments. Shortly after its last flight on 16 October 1928, during which it sustained serious damage, the army dismantled the RS-1.

In the meantime the navy had progressed in the development of rigid airships. To begin with, the navy purchased the British airship R-38, which became the ZR-2. On 24 August 1921, the ZR-2 suffered a catastrophic structural failure during its flight trials, broke up in the air, and crashed near Hull, England, killing forty-four of the forty-nine men on board. The navy's own first rigid dirigible, the ZR-1, was 677 feet long, had a gas volume of 2.235 million cubic feet, and was powered by six 300-horsepower Packard engines. It made its first flight on 4 September 1923, and became the first rigid airship in the world to be inflated with nonflammable helium gas, following the example of the navy blimp C-7, which became the first airship of any type to use helium rather than hydrogen on 1 December 1921. (The following year, despite the greater cost of helium and its inferior lift, the navy adopted a policy of using only helium in its dirigibles, rather than highly flammable hydrogen.) On 10 October 1923, the navy formally christened the ZR-1 the U.S.S. Shenandoah. The Shenandoah made fifty-seven flights totaling 740 hours, including two coast-to-coast flights in 1924, maneuvers with the Atlantic fleet, and moorings to a floating mooring mast on the stern of the tanker U.S.S. Patoka. On 3 September 1925, the Shenandoah broke up in a violent thunder storm and crashed near Ava, Ohio, killing fourteen of the forty-three men on board.

At the end of World War I the navy was to have received two rigid dirigibles, German zeppelins, as spoils of war, but their German crews destroyed them before they could be delivered. In compensation Germany was obliged to build a new zeppelin for the navy. Germany thus constructed the LZ-126, the navy's ZR-3, best known as the U.S.S. Los Angeles. The Los Angeles was 658 feet long, had a gas volume of 2.762 million cubic feet, and relied on five 530-horsepower Maybach engines for power. It made its first flight at the Zeppelin factory in Friedrichshafen, Germany, on 27 August 1924; it made its delivery flight to the United States from 12–15 October, a transatlantic passage of eighty-one hours with thirty persons on board, the sixth transatlantic flight made by any type of aircraft. (Charles A. Lindbergh's celebrated transatlantic crossing by airplane was the seventh.) During the next eight years the Los Angeles served as a training and experimental airship for the navy, making 331 flights totaling 4,398 hours, which included two flights to Bermuda and two to Panama. The navy decommissioned it on 30 June 1932, but retained it at Lakehurst for various structural tests until scrapping it in 1940.

In 1928 the Goodyear-Zeppelin Corporation started work on two rigid airships for the navy, the ZRS-4 and ZRS-5. They were sister ships, 785 feet long, having a gas volume of 6.850 million cubic feet, and powered by eight 560-horsepower Maybach engines. At that time they were the largest airships in the world, not exceeded in size until 1936, when Germany constructed the airship Hindenburg. These airships were unique in that each could carry five Curtiss F-9C fighter planes housed in a hangar within their hulls; the airplanes were equipped with sky-hooks, and the airships could launch and retrieve planes in flight by means of a trapeze lowered from a T-shaped door in their undersides.

The ZRS-4, christened Akron, made its first flight on 25 September 1931. It made seventy-three flights totaling 1,695 hours, including two coast-to-coast flights and one to Panama. On the night of 4 April 1933, a violent electrical storm over the Atlantic caught and destroyed the Akron, which crashed at sea; of the seventy-six men on board, only three survived. The ZRS-5, christened Macon, made its first flight on 21 April 1933. It made fifty-four flights totaling 1,798 hours, including three coast-to-coast flights, and participated in several war games with the U.S. fleet. While returning from maneuvers on 12 February 1935, it suffered a minor structural failure that became uncontrollable, and the Macon crashed in the Pacific. Miraculously, only two of the eighty-three persons were killed in the accident.

The loss of the Macon ended the navy's development of the rigid airship, but the blimp remained. On the eve of World War II the navy had only a half-dozen blimps, but during the war the navy expanded its blimp forces to more than 160 airships for antisubmarine patrols. By the end of the war the United States had constructed a network of blimp bases that reached from South Weymouth, Massachusetts, to Key West, Florida, extending across the Caribbean and down the coast of South America to Rio de Janiero. In 1944 the navy flew five airships to French Morocco, where, based at Port Lyautey, they flew a low-altitude antisubmarine barrier over the Strait of Gibraltar.

The basic training airship of the war years was the L-type blimp (146 feet long, 123,000 cubic feet gas volume, two 146-horsepower Warner engines). The backbone of the antisubmarine patrol forces was the K-type blimp (251 feet, 425,000 cubic feet gas volume, two 425-horsepower Pratt & Whitney engines). During the war the United States lost only one airship to enemy action, the K-74, on 18 July 1943, after its bombs failed to release in an attack on the German submarine U-134 in the Caribbean.

After the war the navy continued its blimp development, increasing the size, lift, endurance, and versatility of its airships. In 1954 the ZPG-1-type blimp appeared (324 feet, 875,000 cubic feet, two 800-horsepower engines). The ZPG-1 was unusual in the new configuration of its tail surfaces; formerly all airship tail surfaces had been affixed to the hull at right angles to the vertical, but the ZPG-1, and all navy airships thereafter, had their tail surfaces disposed in an X configuration, 45 degrees to the vertical, which contributed to increased maneuverability.

Dirigibles have never been fast aircraft; what has recommended their use is their great lift relative to the small engine power required, and their great endurance. An airplane can be airborne for only a few hours; an airship can cruise the air for days. In 1954, for example, an American ZPG-2 stayed in the air for 200 hours. And in 1957 a ZPG-2 made a leisurely nonstop circumnavigation of the North Atlantic, 8,216 nautical miles, from South Wey-mouth, Massachusetts, to Portugal, Morocco, and the Antilles, finally landing at Key West, Florida, after being in the air for 264 hours.

The ZPG-2 that flew this nonstop double crossing of the Atlantic was 342 feet long and had a gas volume of 975,000 cubic feet. Like all other navy blimps, it was an antisubmarine aircraft. In addition, the navy modified five other ZPG-2's into ZPG-2W's that could carry an extraordinarily large air-search radar for airborne early warning duty. In 1956 the navy procured four more ZPG-3W's to carry an even larger radar. With a gas volume of 1.5 million cubic feet, the ZPG-3W was the largest non-rigid airship ever built.

By 1960 high-speed, deep-cruising nuclear submarines were rendering the blimp's antisubmarine capabilities obsolete; in addition, experts had begun to fear an attack by missiles rather than by bombers, which degraded the airship's early-warning mission. In June 1961 the navy decommissioned its blimp squadrons, and on 21 August 1962, terminated all flight operations by airships.

Since the 1920s the Goodyear Tire & Rubber Company has maintained a small fleet of advertising blimps, beginning with the Pilgrim of 1925. The Goodyear fleet reached its maximum strength in the 1930s, when it operated six airships, the Defender, Resolute, Enterprise, Reliance, Rainbow, and Ranger, all of which had been turned over to the navy as training ships by 1942. Goodyear revived its fleet after the war, but fear of the competition of television advertising caused the company to cut back its investment in the enterprise. Goodyear had only one blimp remaining when a study revealed what the American public had long known: the blimp was a unique advertising vehicle, and "blimp" had become synonymous with "Goodyear." Since 1969 three Goodyear blimps have been cruising the skies of the United States, the Columbia, Mayflower, and America, while a fourth, the Europa, operates in Western Europe. Goodyear's was the only organized airship operation in the world in the 1970s. Since then a number of other companies have built smaller blimps, including MetLife insurance company, which operates the blimps Snoopy One and Snoopy Two (decorated with images of the dog Snoopy, from the Peanuts comic strip). These flying billboards have become common sights at American sporting events, where they often provide aerial shots to television networks in exchange for free advertising.

BIBLIOGRAPHY

Kirschner, Edwin J. The Zeppelin in the Atomic Age: The Past, Present, and Future of the Rigid Lighter-Than-Air Aircraft. Urbana: University of Illinois Press, 1957.

Robinson, Douglas H. Giants in the Sky: A History of the Rigid Airship. Seattle: University of Washington Press, 1973.

Smith, Richard K. The Airships Akron & Macon: Flying Aircraft Carriers of the United States Navy. Annapolis, Md.: U.S. Naval Institute, 1965.

Toland, John. Ships in the Sky: The Story of the Great Dirigibles. New York: Holt, 1957.

Richard K.Smith/c. w.

See alsoAir Defense ; Air Force, United States ; Army, United States ; Navy, United States .

DIRIGIBLES

Dirigibles and Blimps

Lighter-than-air craft include both dirigibles, with rigid hull structures, and blimps, with limp hull structures that fall flat when deflated. Blimps were used during both world wars, but they were too small to carry many bombs in wartime or many passengers in peacetime. The large dirigibles could perform either mission.

The Zeppelin

The French invented the airship in the late eighteenth century, but the craft remained strictly experimental for a century until Graf Ferdinand von Zeppelin caused the Germans to move permanently into the forefront of the field. Indeed the word zeppelin became a generic term for the dirigible. Americans did little in the early period of experimenting with lighter-than-air craft, but when they saw the power of German zeppelins on bombing raids over England in World War I and watched while the huge craft soaked up anti-aircraft fire and then floated away, they vowed to get into the program. Separate gas bags within the hulls of the zeppelins meant that a few holes would not disable a ship, although some, of course, were shot down.

The R38

In 1920 the U.S. Navy contracted with the British government to purchase their R38 dirigible and sent an aviation crew to be trained in operating the ship and to fly it back to America. Before the turnover was complete, however, the airship broke in half during a strenuous test run over Hull, England, on 23 August 1921. Like the German airships, the R38 was filled with hydrogen, which is highly flammable, and the breakage started fires, which increased the number of casualties. Forty-four men were killed, sixteen of them Americans. It was the worst aviation disaster in history up to that time. Since the transfer to the U.S. Navy was not complete, the British refunded half a million dollars to the United States.

Billy Mitchell

In 1919 Brig. Gen. William "Billy' Mitchell, the fiery and controversial advocate of military air power, tried to get the Germans to build a dirigible for the U.S. Army. Unauthorized by higher authorities and opposed by the Navy Department, the negotiations fell through. The army settled for a small, Italian, semirigid airship, the Roma, Bought in June 1920 and brought to America disassembled, the Roma crashed and burned in November 1921 on her maiden U.S. flight, causing the deaths of thirty-four men.

The Shenandoah.

In summer 1923 the first American-made dirigible went airborne. Christened the Shenandoah, she was also the world's first rigid airship to be filled with helium. Unlike hydrogen, helium is not flammable, but it is the second lightest element, whereas hydrogen is the lightest. Thus helium has less lifting ability than hydrogen. Another disadvantage with helium was its cost: some two hundred times as much as hydrogen. During the years between the two world wars the United States was the sole significant producer of helium, and it had only one plant, in Fort Worth, Texas. In late 1924, when the Shenandoah was joined at her home hanger in Lakehurst, New Jersey, by her German-made sister ship Los Angeles, there was not enough helium for both dirigibles, and the Shenandoah was out of commission until June 1925.

Disaster

The Shenandoah was used on reconnaissance missions for the naval fleet, but the navy considered the airship most useful in public relations. Most of the time it was on exhibit to large crowds in various cities. On 2 September 1925 the Shenandoah left Lakehurst for its fifty-seventh flight, a public-relations tour of big cities and state fairs in the Midwest. The Shenandoah had successfully been flown from coast to coast, but conditions on this flight were more severe. The weather in the American Midwest is the worst of any populated area on earth, with numerous tornadoes and violent thunder-storms. In 1925 there was no radar, and weather forecasting was still rudimentary. On 3 September the Shenandoah encountered a fierce line of thunderstorms near Ava, Ohio, as a cold front overriding a warm front set a tremendous vertical windshear.

Final Moments

The giant airship rose uncontrollably with violent rolling and pitching. Structural failures began to occur. The ship then dived out of control, dropping more than three thousand feet in less than three minutes. The crew discharged ballast, and the ship leveled out, only to be caught two minutes later in another updraft. This time the stricken vessel broke in half, spilling out some of the crew. The control gondola broke free and fell to earth, killing the captain, Lt. Comdr. Zachaiy Lansdowne, along with five of his men. Of a crew of forty-three there were twenty-nine survivors. They free-ballooned the forward part of the ship to a relatively soft landing. In an era not yet accustomed to aerial disasters, law enforcement officials were unable to cordon off the crash site, and looters made off with many pieces of wreckage.

Los Angeles.

At about the same time they were building the Shenandoah the U.S. Navy was attempting to buy a German-made dirigible. Faced with opposition from Britain and France, the Americans persisted in difficult negotiations with their recent enemy. Finally the Los Angeles—built by the world's leading airship company, Luftschiffbau Zeppelin, and filled with helium at the insistence of the Americans—flew from Friedrichshafen, Germany, to Lakehurst, New Jersey, in October 1924.

Eight Years of Service

The Los Angeles was in active service for eight years, a long time for a dirigible, making 331 flights. After it was retired from active duty in 1932, it was used in various experiments for another seven years until finally being broken up for scrap in 1939. The United States built two more dirigibles in the 1930s, the Akron and the Macon. Each was lost after only two years of service, the Akron in 1933 off New England and the Macon in 1935 off California. There was no long-range reconnaissance by dirigibles during World War II, only coastal scouting by a few blimps. Many U.S. Navy men, all volunteers, had given their lives to test a different kind of airship—one that ultimately was abandoned.

Sources:

Guy Hartcup, The Achievement of the Airship: A History of the Development of Rigid, Semi-Rigid and Non-Rigid Airships (Newton Abbot, U.K. & North Pomfret, Vt.: David & Charles, 1974);

Douglas H. Robinson and Charles L. Keller, "Up Ship!" A History of the U.S. Navy's Rigid Airships, 1919-1935 (Annapolis, Md.: Naval Institute Press, 1982).

airship 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. 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 fully rigid airship has been built since the 1930s.

In 1997 the Zeppelin NT, which uses modern technologies and design innovations to realize a more maneuverable and efficient semirigid airship, made its maiden flight and testing began in the hope of putting airships into commercial service once again. Several have been built; they are usually flown in a slightly heavier-than-air condition and use engine power to attain lift, and are typically used for tourist flights and advertising. 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.

Bibliography: 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).

airship (dirigible) Powered lighter-than-air craft able to control its direction of motion. A gas that is less dense than air, nowadays helium, provides lift. A rigid airship, or Zeppelin, maintains its form with a framework of girders covered by fabric or aluminium alloy. Non-rigid airships, or blimps, have no internal structure. They rely on the pressure of the contained gas to maintain the shape.

air·ship / ˈe(ə)rˌship/ • n. a power-driven aircraft that is kept buoyant by gas (typically helium, formerly hydrogen) that is lighter than air.

airship n. a craft that weighs less than the air it displaces and has its own means of propulsion and directional control surfaces. Also called dirigible.)

Dirigibles. See Blimps and Dirigibles.

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