Airship

Airship, lighter-than-air craft equipped with a bag containing a gas to lift the ship, a means of propulsion, means for adjusting buoyancy, and one or more gondolas for the crew, passengers, and power units. The bag invariably contains helium, although hydrogen was formerly used. The bag is elongated or streamlined to enable easy passage through the air. The means of propulsion usually comprises one or more engines and propellers. A means for releasing ballast, usually sand or water, may be used to increase buoyancy; and a means for releasing gas may be used to reduce buoyancy. An alternative is to inflate or deflate air bags called ballonets set inside the main gas bag; this alters the overall density of the airship. To steer the airship, the pilot uses one or more vertically hinged rudders; to control climb or descent, the pilot employs one or more horizontally hinged lifts.

Airships, or dirigibles, were developed from the free balloon. Three classes of airships are recognized: the non-rigid airship, commonly called a blimp, in which the form of the bag is maintained by the pressure of the gas; the semi-rigid airship, in which, to maintain the form, gas pressure acts in conjunction with a longitudinal keel; and the rigid airship, in which the form is determined by a rigid structure. All three classes are dirigibles (Latin, dirigere, “to direct, to steer”).

The first successful airship was that of the French engineer and inventor Henri Giffard, who in 1852 constructed a cigar-shaped, non-rigid gas bag 44 m (143 ft) long, driven by a screw propeller driven by a 2.2-kw (3-hp) steam engine. He flew over Paris at a speed of about 10 km/h (6 mph). Giffard's airship could be steered only in calm or nearly calm weather. The first airship to demonstrate its ability to return to its starting place in a light wind was La France, developed in 1884 by the French inventors Charles Renard and Arthur Krebs. It was propelled by an electrically driven propeller. The Brazilian aeronaut Alberto Santos-Dumont developed a series of 14 airships in France. In his No. 6, in 1901, he circled the Eiffel Tower.

The American inventor Thomas S. Baldwin built a dirigible flown by Roy Knabenshue in 1904. Walter Wellman failed in an effort to cross the Atlantic Ocean in an airship in 1910. Although many successful flights were made before 1910, the best engine available for use in the early airship was too heavy in proportion to its power.

Count Ferdinand von Zeppelin, the German inventor, completed his first airship in 1900; this ship had a rigid frame and served as the prototype of many subsequent models. The first Zeppelin airship consisted of a row of 17 gas cells individually covered in rubberized cloth; the whole was confined in a cylindrical framework covered with smooth-surfaced cotton cloth. It was about 128 m (420 ft) long and 12 m (38 ft) in diameter; the hydrogen-gas capacity totalled 11.3 million litres (399,000 cu ft). The ship was steered by rudders fore and aft and was driven by two 11-kw (15-hp) Daimler internal-combustion engines, each turning two propellers. Passengers, crew, and engine were carried in two aluminium gondolas suspended forward and aft. At its first trial, on July 2, 1900, the airship carried five people; it attained an altitude of 396 m (1,300 ft) and flew a distance of 6 km (3.75 mi) in 17 minutes.

The first commercial means of regular passenger air travel was supplied by the Zeppelin airships Deutschland in 1910 and Sachsen in 1913. At the beginning of World War I, 10 zeppelins were in service in Germany, and others were built for the military services. By 1918 the total number of zeppelins that had been constructed was 67, of which 16 survived the war. Those not captured were surrendered to the Allies by the terms of the Treaty of Versailles in 1919. At the outbreak of the war, France had a fleet of semi-rigid airships, developed by officers of the French army. The war, however, disclosed the vulnerability of airships to aeroplane attack, and caused the abandonment of the dirigible for offensive military purposes. non-rigid airships became useful for aerial observation, coastal patrol, convoying, and locating enemy submarines and mines, because of their ability to hover over a given location and to remain in the air for longer periods than the aeroplane.

Britain had experimented before World War I with large airships and had employed many smaller ones during it. Towards the end of the war it began intensive development of rigid airships, stimulated by the prospect that non-flammable helium gas would soon be available in quantities sufficient to inflate large ships. The R34, with a length of 196 m (643 ft) and a gas capacity of 56.1 million litres (1.98 million cu ft), was commissioned in 1919. It made the first transatlantic flight by an airship, flying by way of Newfoundland, Canada, from East Fortune, Scotland, to Mineola, New York, and returning to Pulham, in Norfolk. The total flying time for the round trip was 183 h and 15 min and the aggregate distance travelled about 11,200 km (7,000 mi). In 1921 the R38, some 25 per cent larger than the R34, was completed; both were wrecked that same year. However, other craft, including the successful R33, continued to fly for some years after this.

In 1921 the United States government purchased a large semi-rigid airship named the Roma. It had a length of 125 m (410 ft) and a gas capacity of 34 million litres (1.2 million cu ft), and was powered by six 12-cylinder 298-kw (400-hp) motors. The ship was lost in 1922; in 1923 the US Navy commissioned the Shenandoah, originally known as the ZR1, the first zeppelin-type airship of entirely American construction and the first of the type filled with helium gas. It had a length of 206 m (677 ft) and a gas capacity of 59.9 million litres (2.115 million cu ft). In the two years following, it made several extended and successful flights, but in September 1925 it was completely wrecked in a windstorm, with the loss of 14 crew members. The 29 survivors undoubtedly owed their lives to the use of non-flammable helium for inflation.

In 1924 the navy received delivery of the ZR3, later christened the Los Angeles, made by the Zeppelin works in Germany in partial payment of war reparations. This airship was 198 m (650 ft) long and had a gas capacity of 70 million litres (2.475 million cu ft). The control gondola also carried accommodation for 30 passengers, with sleeping facilities similar to those of a Pullman car. The Los Angeles made about 250 flights, including trips to Puerto Rico and Panama. It was decommissioned in 1932.

In 1926 the Italian airship Norge, a semi-rigid craft of about 18.4 million litres (650,000 cu ft) capacity, flew from Spitsbergen, Norway, over the North Pole to Teller, Alaska, where the ship was dismantled. Another polar flight was tried two years later in a similar ship, the Italia, but after passing over the pole it was wrecked on the return flight, with the loss of eight lives.

The German Zeppelin plant in 1928 produced the Graf Zeppelin, which had a length of 235 m (772 ft) and a gas capacity of 105 million litres (3,710,000 cu ft). It flew a total of more than 1,600,000 km (1 million mi) in nine years of service, crossing the Atlantic Ocean to North or South America 139 times and making a complete trip around the world with stops only at Tokyo, Los Angeles, and Lakehurst, New Jersey.

About the same time, the British resumed construction of rigid airships, launching the R100 and the R101 in 1929. With lengths of 215 m (707 ft) and 221 m (724 ft), respectively, these dirigibles had a gas capacity of 140 million litres (5 million cu ft) each. The R101, which included several novel features, was powered by five 485-kw (650-hp) diesel engines and had dining, sleeping, and recreational facilities for 100 people built into the hull. In October 1930, on a flight to India, it crashed during a violent rainstorm into a hill near Beauvais, France, and was completely destroyed by fire; 46 of the passengers and crew lost their lives. The R100, which in the preceding August had made a round trip to Montreal, was scrapped after the destruction of the R101, and the British government abandoned construction of all dirigibles.

Meanwhile, in 1928, the US Navy purchased two dirigibles, each with a length of 239 m (785 ft), a gas capacity of 184 million litres (6,500,000 cu ft) of helium, and eight 418-kw (560-hp) engines. A novel feature of the design was provision for a hangar compartment in the ship capable of accommodating five scout aeroplanes, which could be released or taken aboard in flight. The first of these airships, the Akron, was completed in 1931 and was wrecked in a storm off the New Jersey coast in 1933; the wreckage was discovered by a marine research team in 1986. The second ship, the Macon, was completed in 1933 and wrecked in 1935. Since the Macon, the United States has built no rigid airships.

The famous German-built Hindenburg had a length of 245 m (804 ft) and a gas capacity of 190 million litres (6,710,000 cu ft). After making ten transatlantic crossings in regular commercial service in 1936, it was destroyed by fire in 1937 when it was landing at Lakehurst, New Jersey; 36 of its 92 passengers and crew were killed.

Since the destruction of the Hindenburg, airship activity has been confined to the non-rigid type of craft. In 1938 all military blimps in the United States were placed under navy jurisdiction, with the Naval Air Station at Lakehurst as the centre of operations. During World War II, blimps were employed for patrol, scouting, convoy, and antisubmarine work. A private American firm developed several small, non-rigid airships that have been used to provide aerial television views of sports events, to take people on rides, and for advertising purposes.

After World War II the US Navy continued to develop the airship for such purposes as antisubmarine warfare, intermediate search missions, and early-warning missions. The largest naval airship type, the ZPG-2, was 99 m (324 ft) long and had a capacity of 24.8 million litres (875,000 cu ft) of helium. An airship of this type stayed aloft without refuelling for more than 200 hours. The US Navy discontinued the use of airships in 1961; however, during the later 1980s there was a renewal of military interest in airships, and several countries began to study the feasibility of using airships for airborne early warning and electronic warfare as well as antisubmarine warfare. Some countries were also showing an equal interest in airships for civil aviation and advertising purposes.