A Zeppelin is a type of rigid airship named after the German inventor Ferdinand von Zeppelin () who pioneered rigid airship development at the beginning of the 20th century. Zeppelin's notions were first formulated in 1874Eckener 1938, pp. 155–157. and developed in detail in 1893.Dooley 2004, p. A.187. They were patented in Germany in 1895 and in the United States in 1899. After the outstanding success of the Zeppelin design, the word zeppelin came to be commonly used to refer to all forms of rigid airships. Zeppelins were first flown commercially in 1910 by Deutsche Luftschiffahrts-AG (DELAG), the world's first airline in revenue service. By mid-1914, DELAG had carried over 10,000 fare-paying passengers on over 1,500 flights. During World War I, the German military made extensive use of Zeppelins as bombers and as scouts. Numerous bombing raids on Britain resulted in over 500 deaths.Cole and Cheeseman 1984, p. 449.
The defeat of Germany in 1918 temporarily slowed the airship business. Although DELAG established a scheduled daily service between Berlin, Munich, and Friedrichshafen in 1919, the airships built for that service eventually had to be surrendered under the terms of the Treaty of Versailles, which also prohibited Germany from building large airships. An exception was made to allow the construction of one airship for the United States Navy, the order for which saved the company from extinction.
In 1926, the restrictions on airship construction were lifted and, with the aid of donations from the public, work began on the construction of LZ 127 Graf Zeppelin. That revived the company's fortunes and, during the 1930s, the airships Graf Zeppelin, and the even larger LZ 129 Hindenburg operated regular transatlantic flights from Germany to North America and Brazil. The spire of the Empire State Building was originally designed to serve as a mooring mast for Zeppelins and other airships, although it was found that high winds made that impossible and the plan was abandoned. The Hindenburg disaster in 1937, along with political and economic developments in Germany in the lead-up to World War II, hastened the demise of airships.
Principal characteristics
The principal feature of the Zeppelin's design was a fabric-covered, rigid metal framework of transverse rings and longitudinal girders enclosing many individual gasbags or cells, which were filled with flammable hydrogen (H₂) – the only practical lifting gas available to German engineers at the time. This structure allowed the craft to be much larger than non-rigid airships, which relied on the inflation of a single pressure envelope to maintain their shape. Most Zeppelins used duralumin for the framework – a combination of aluminium, copper, and two or three other metals, the exact composition of which was kept secret for years. In early models, the gasbags were made of rubberized cotton, but most later craft used goldbeater's skin derived from cattle gut.
The first Zeppelins had long cylindrical hulls with tapered ends and complex multi-plane fins. During World War I, following the lead of the rival firm Schütte-Lanz Luftschiffbau, almost all later airships changed to the more familiar streamlined shape with cruciform tail fins.
Zeppelins were propelled by several internal combustion engines, mounted in gondolas or engine cars attached outside the structural framework. Some of these could provide reverse thrust for manoeuvring while mooring.
Early models had a fairly small externally-mounted gondola for passengers and crew beneath the frame. This space was never heated, because fire outside of the kitchen was considered too risky, and during trips across the North Atlantic or Siberia, passengers were forced to bundle in blankets and furs to keep warm and were often miserably cold.
By the time of the Hindenburg, several important changes had made traveling much more comfortable: the passenger space had been relocated to the interior of the framework, passenger rooms were insulated from the exterior by the dining area, and forced warm air could be circulated from the water that cooled the forward engines. The new design did prevent passengers from enjoying the views from the windows of their berths, which had been a major attraction on the Graf Zeppelin. On both the older and newer vessels, the external viewing windows were often open during flight. The flight altitude was so low that no pressurization of the cabins was necessary. The Hindenburg did maintain a pressurized air-locked smoking room: no flame was allowed, but a single electric lighter was provided, which could not be removed from the room.
Access to Zeppelins was achieved in several ways. The Graf Zeppelins gondola was accessed while the vessel was on the ground, via gangways. The Hindenburg also had passenger gangways leading from the ground directly into its hull, which could be withdrawn entirely, ground access to the gondola, and an exterior access hatch via its electrical room; the latter was intended for crew use only.
On some long-distance zeppelins, engines were powered by a special Blau gas produced by the Zeppelin facility in Friedrichshafen. The combustible Blau gas was formulated to make its weight near that of air, so that its storage and consumption had little effect on the Zeppelin's buoyancy. Blau gas was used on the first Zeppelin voyage to the United States, starting in 1929.
History
Early designs
Count Ferdinand von Zeppelin's interest in airship development began in 1874, when he was inspired by a lecture given by Heinrich von Stephan on the subject of "World Postal Services and Air Travel" to outline the basic principle of his later craft in a diary entry dated 25 March 1874.Dooley 2004, p. A.183. It describes a large rigidly framed outer envelope containing several separate gasbags.Robinson 1973 p.13 He had previously encountered Union Army balloons in 1863 when he visited the United States as a military observer during the American Civil War.
Count Zeppelin began to seriously pursue his project after his early retirement from the army in 1890 at the age of 52. Convinced of the potential importance of aviation, he started working on various designs in 1891 and had completed detailed designs by 1893. An official committee reviewed his plans in 1894, and he received a patent, granted on 31 August 1895, with Theodor Kober producing the technical drawings.Dooley 2004, p. A.190.
Zeppelin's patent described a ("Steerable aircraft with several carrier bodies arranged one behind another"), an airship consisting of flexibly articulated rigid sections. The front section, containing the crew and engines, was long with a gas capacity of . The middle section was long with an intended useful load of and the rear section long with an intended load of .Robinson 1973 pp.15-6
Count Zeppelin's attempts to secure government funding for his project proved unsuccessful, but a lecture given to the Union of German Engineers gained their support. Zeppelin also sought support from the industrialist Carl Berg, then engaged in construction work on the second airship design of David Schwarz. Berg was under contract not to supply aluminium to any other airship manufacturer, and subsequently made a payment to Schwarz's widow as compensation for breaking this agreement.Dooley 2004, p. A.193. Schwarz's design differed fundamentally from Zeppelin's, crucially lacking the use of separate gasbags inside a rigid envelope.Dooley 2004, p. A.191.
In 1898, Count Zeppelin founded the Gesellschaft zur Förderung der Luftschiffahrt"Die Ausführung des Zeppelin'schen Luftschiffes" (in German). Die Welt (Vienna), Issue 22, 3 June 1898, p. 6. Retrieved: 11 March 2012. ("Society for the Promotion of Airship Flight"), personally contributing more than half of its 800,000-mark share capital — a sum broadly equivalent to €6.65 million in early 2010s terms, based on historical gold value and purchasing power estimates. Responsibility for the detailed design was given to Kober, whose place was later taken by Ludwig Dürr, and construction of the first airship began in 1899 in a floating assembly-hall or hangar in the Bay of Manzell near Friedrichshafen on Lake Constance (the Bodensee). The intention behind the floating hall was to facilitate the difficult task of bringing the airship out of the hall, as it could easily be aligned with the wind. The LZ 1 (LZ for Luftschiff Zeppelin, or "Zeppelin Airship") was long with a hydrogen capacity of , was driven by two Daimler engines each driving a pair of propellers mounted either side of the envelope via bevel gears and a driveshaft, and was controlled in pitch by moving a weight between its two nacelles.Robinson 1971, p. 13
The first flight took place over Lake Constance on 2 July 1900.Dooley 2004, pp. A.197–A.198. Damaged during landing, it was repaired and modified and proved its potential in two subsequent flights made on 17 and 24 October 1900, bettering the 6 m/s () velocity attained by the French airship La France. Despite this performance, the shareholders declined to invest more money, and so the company was liquidated, with Count von Zeppelin purchasing the ship and equipment. The Count wished to continue experimenting, but he eventually dismantled the ship in 1901.de Syon 2001, p. 25.
Donations, the profits of a special lottery, some public funding, a mortgage of Count von Zeppelin's wife's estate, and a 100,000 mark contribution by Count von Zeppelin himself allowed the construction of LZ 2, which made only a single flight on 17 January 1906.de Syon 2001, p. 26. After both engines failed, it made a forced landing in the Allgäu mountains, where a storm subsequently damaged the anchored ship beyond repair.
Incorporating all the usable parts of LZ 2, its successor LZ 3 became the first truly successful Zeppelin. This renewed the interest of the German military, but a condition of purchase of an airship was a 24-hour endurance trial.de Syon 2001, p. 35. This was beyond the capabilities of LZ 3, leading Zeppelin to construct his fourth design, the LZ 4, first flown on 20 June 1908. On 1 July, it was flown over Switzerland to Zürich and then back to Lake Constance, covering and reaching an altitude of . An attempt to complete the 24-hour trial flight ended when LZ 4 had to make a landing at Echterdingen near Stuttgart because of mechanical problems. During the stop, a storm tore the airship away from its moorings on the afternoon of 5 August 1908. It crashed into a tree, caught fire, and quickly burned out. No one was seriously injured.
This accident would have finished Zeppelin's experiments, but his flights had generated huge public interest and a sense of national pride regarding his work, and spontaneous donations from the public began pouring in, eventually totalling over six million marks.de Syon 2001, p. 38. This enabled the Count to found the Luftschiffbau Zeppelin GmbH (Airship Construction Zeppelin Ltd.) and the Zeppelin Foundation.
Before World War I
Before World War I (1914–1918), the Zeppelin company manufactured 21 more airships. The Imperial German Army bought LZ 3 and LZ 5 (a sister-ship to LZ 4, which was completed in May 1909) and designated them Z I and Z II respectively.Robinson 1971, p. 14 Z II was wrecked in a gale in April 1910, while Z I flew until 1913, when it was decommissioned and replaced by LZ 15, designated ersatz Z I. First flown on 16 January 1913, it was wrecked on 19 March.
In April 1913, its newly built sister-ship LZ 15 (Z IV) accidentally intruded into French airspace owing to a navigational error caused by high winds and poor visibility. The commander judged it proper to land the airship to demonstrate that the incursion was accidental, and brought the ship down on the military parade-ground at Lunéville. The airship remained on the ground until the following day, permitting a detailed examination by French airship experts.