Airship
|
|
An airship is a buoyant ("lighter-than-air") aircraft that can be steered and propelled through the air. Unlike aerodynamic ("heavier-than-air") aircraft which stay aloft by moving an airfoil through the air in order to produce lift, airships stay aloft primarily by means of having a cavity (usually quite large) that is filled with a gas of lesser density than the surrounding atmosphere.
Airships are also known as dirigibles from the French dirigeable, meaning "steerable". The term airship is sometimes informally used to mean a machine capable of atmospheric flight. The term zeppelin is a genericized trademark that originally referred to airships manufactured by the Zeppelin company. In modern common usage, the terms zeppelin, dirigible and airship are used interchangebly for any type of rigid airship, with the terms blimp or airship alone used to describe non-rigid airships. In modern technical usage however, airship is the term used for all aircraft of this type with zeppelin referring only to aircraft of that manufacture and blimp referring only to non-rigid airships.
In the early days of airships, the primary lifting gas was hydrogen. And until the 1940s, most French, German, and British airships continued to use hydrogen because it offered greater lift and was cheaper. However, hydrogen is also flammable when mixed with air. The additional buoyancy from using hydrogen is actually only about 10% greater than that provided by helium. So the issue became one of safety versus cost. American airships have been filled with helium since the 1920s and modern passenger-carrying airships are, by law, now prohibited from being filled with hydrogen. Some small experimental ships still use hydrogen. Other small experimental airships are filled with hot air in a fashion similar to a hot air balloon. They are sometimes called "hotships".
In contrast to airships, balloons are buoyant aircraft that generally rely on wind currents for movement, though vertical movement can be controlled in both.
| Contents |
Types
Usn-airships.jpg
- Rigid airships (for example, Zeppelins) have rigid frames containing multiple, non-pressurized gas cells or balloons to provide lift. Rigid airships do not depend on internal pressure to maintain their shape.
- Non-rigid airships (blimps) use a pressure level in excess of the surrounding air pressure in order to retain their shape.
- Semi-rigid airships, like blimps, require internal pressure to maintain their shape, but have extended, usually articulated keel frames running along the bottom of the envelope to distribute suspension loads into the envelope and allow lower envelope pressures.
- Metal-clad airships have characteristics of both rigid and non-rigid airships, utilizing a very thin, airtight metal envelope, rather than the usual rubber-coated fabric envelope. Only two ships of this type, Schwarz's aluminium ship of 1897 and the ZMC-2, have been built to date.
- Hybrid airship is a general term for an aircraft that combines characteristics of heavier-than-air (airplane or helicopter) and lighter than air technology. Examples include helicopter/airship hybrids intended for heavy lift applications and dynamic lift airships intended for long-range cruising. No practical human-carrying hybrid airships have been built to date. However, many designs have been proposed and some prototypes built.
History
The development of airships was necessarily preceeded by the development of balloons. See balloon (aircraft) for details.
Beginnings
Airships were among the first aircraft to fly, with various designs flying throughout the 19th century. They were largely attempts to make relatively small balloons more steerable, and often contained features found on later airships. These early airships set many of the earliest aviation records.
In 1784 Jean-Pierre Blanchard fitted a hand-powered propeller to a balloon, the first recorded means of propulsion carried aloft. The first person to make an engine-powered flight was Henri Giffard who, in 1852, flew 27 km (17 miles) in a steam-powered airship. Charles F. Ritchel made a public demonstration flight in 1878 of his hand-powered one-man rigid airship and went on to build and sell five of his aircraft. Paul Haenlein flew an airship with an internal combustion engine on a tether in Vienna, the first use of such an engine to power an aircraft. In 1880, Karl Wölfert and Ernst Baumgarten attempted to fly a powered airship in free flight, but crashed. In the 1880's a Serb named Ogneslav Kostovic Stepanovic also designed and built an airship. However the craft was destroyed by fire before it flew.
In 1883, the first electric-powered flight was made by Gaston Tissandier who fitted a Siemens electric motor to an airship. The first fully controllable free-flight was made in a French Army airship, La France, by Charles Renard and Arthur Krebs in 1884. The electric-powered flight covered 8 km (5 miles) in 23 minutes. In 1888, Wölfert flew a Daimler-built petrol engine powered airship at Seelburg. In 1896, a rigid airship created by Croatian engineer David Schwarz made its first flight at Tempelhof field in Berlin. After Schwarz's death, his wife, Melanie Schwarz, was paid 15,000 Marks by Zeppelin for information about the airship. In 1901, Santos Dumont, in his airship "Number 6", a small blimp, won the Deutsch de la Meurthe prize of 100,000 francs for flying from the Parc Saint Cloud to the Eiffel Tower and back in under thirty minutes.
The Golden Age
The beginning of the "Golden Age of Airships" was marked with the launch of the LZ1 Luftschiff Zeppelin in July of 1900 which would lead to the most successful airships of all time, the Zeppelins. These ships were named after the pioneer Count Ferdinand von Zeppelin. Von Zeppelin began experimenting with rigid airship designs in the 1890's leading to some patents and the LZ1 (1900) and the LZ2 (1906). He had, by the time WW1 broke out, given them a standard and highly efficient layout: an essentially cylindrical metal-framed and fabric-covered hull, large tail fins for stability, and streamlined engine and crew pods hung beneath the hull.
The prospect of using airships as bomb carriers had been recognised in Europe well before the airships themselves were up to the task. H. G. Wells described the obliteration of entire fleets and cities by airship attack in The War in the Air (1908), and scores of less famous British writers declared in print that the airship had altered the face of world affairs forever. On 5 March 1912, Italian forces became the first to use dirigibles for a military purpose during reconnaissance west of Tripoli behind Turkish lines. It was World War I, however, that marked the airship's real debut as a weapon.
Germany believed it had found, in the zeppelin, the ideal weapon with which to bypass the British Navy and strike at Britain itself. Raids began by the end of 1914, reached a first peak in 1915, and then were discontinued until 1917. Zeppelins proved to be terrifying but inaccurate weapons. Navigation, target selection and bomb-aiming proved to be difficult under the best of conditions, and the darkness and clouds that frequently accompanied zeppelin missions reduced accuracy even further. The physical damage done by the zeppelins over the course of the war was trivial, and the deaths that they caused (though visible) amounted to a few hundred at most. The zeppelins also proved to be vulnerable to attack by aircraft and antiaircraft guns, especially those armed with tracer bullets. Several were shot down in flames by British defenders, and others crashed 'en route'.
Airplanes had essentially replaced airships as bombers by the end of the war, and Germany's remaining zeppelins were scrapped or handed over to the Allied powers as spoils of war. The British rigid airship program, meanwhile, had been largely a reaction to the potential threat of the German one, and was largely though not entirely based on imitations of the German ships. One such replica, one of a series of ships based on the wreckage of the L-33, was the British R-34. It landed in New York on July 6, 1919, completing the first crossing of the Atlantic by an airship and the first non-stop crossing by any aircraft. Impressed, British leaders began to contemplate a fleet of airships that would link Britain to its far-flung colonies. The success of another prize, the USS Los Angeles, encouraged the United States Navy to invest in airships of its own. Germany, meanwhile, was building the Graf Zeppelin, the first of what was intended to be a new class of passenger airships.
One example for these is the first American-built rigid dirigible ZR-1 "USS Shenandoah" ("daughter of the stars", with ZR standing for "Zeppelin Rigid"), which flew in 1923. The ship was christened on August 20 in Lakehurst, New Jersey and was the first to be inflated with the noble gas helium, which was still so rare at the time that the Shenandoah contained most of the world's reserves. So, when the Los Angeles was delivered, it was at first filled with the helium from ZR-1.
Downfall
Initially airships met with great success and compiled an impressive safety record. The Graf Zeppelin, for example, flew over 1 million miles (including the first circumnavigation of the globe by air) without a single passenger injury. The expansion of airship fleets and the growing (sometimes excessive) self-confidence of airship pilots gradually made the limits of the type clear, however, and initial successes gave way to a series of tragic rigid airship accidents. In fact, with the exception of the Graf Zeppelin, most of the world's most famous airships eventually crashed.
R-38-rescue.jpg
Although Los Angeles flew successfully for 8 years, the U.S. Navy eventually lost all three of its American built rigid airships to accidents. USS Shenandoah flew into a thunderstorm over Ohio in 1925 and broke into pieces. USS Akron was caught by a microburst and driven down into the surface of the sea off the shore of New Jersey in 1933. Both storm-related losses led to great loss of life. USS Macon broke up after suffering a structural failure in its upper fin off the shore of Point Sur in California in 1935. All but 2 of the 83 people aboard Macon survived the crash.
Britain suffered its own airship tragedy in 1930 when R 101, a ship far advanced for its time but rushed to completion and sent on a trip to India before she was ready, crashed in France with the loss of 48 out of 54 aboard. Because of the bad publicity surrounding the crash, the Air ministry grounded the competing R 100 in 1930 and sold it for scrap in 1931.
The most spectacular and widely remembered airship accident, however, is the burning of the Hindenburg on 6 May 1937, which caused public faith in airships to evaporate in favour of faster, more cost-efficient (albeit less energy-efficient) airplanes. What is generally not remembered is that of the 97 people on board, 62 got out alive. There were 36 dead: 13 passengers, 22 aircrew, and one American groundcrewman.
Most probably, the airplane became the transport of choice also because it is less sensitive to wind. Aside from the problem of manoeuvring and docking in high winds, the trip times for an upwind versus a downwind trip of an airship can differ greatly, and even crabbing at an angle to a crosswind eats up ground speed. Those differences make scheduling difficult.
Airships in the Second World War
American construction of airships for civilian purposes was halted in the 1930s by a series of fatal crashes. However, military development of airships was continued in the US.
While Germany determined that airships were obsolete for military purposes in the coming war and concentrated on the development of airplanes, the United States pursued a program of military airship construction even though it had not developed a clear military doctrine for airship use. At the Japanese attack on Pearl Harbor on 7 December 1941 that brought the United States into World War II, it had 10 non-rigid airships:
- 4 K-class : K-2, K-3, K-4 and K-5 designed as a patrol ships built from 1938.
- 3 L-class : L-1, L-2 and L-3 as small training ships, produced from 1938.
- 1 G-class built in 1936 for training.
- 2 TC-class that were older patrol ships designed for land forces, build in 1933. The US Navy acquired them from Army in 1938.
Only K and TC class airships could be used for combat purposes and they were quickly pressed into service against Japanese and German submarines which at that time were sinking US shipping in visual range of US coast. US Navy command, remembering the airship anti-submarine success from WWI, immediately requested new modern anti-submarine airships and on 2 January 1942 formed the ZP-12 patrol unit based in Lakehurst from the 4 K airship. The ZP-32 patrol unit was formed from 2 TC and 2 L airship a month later, based at US Navy (Moffet Field) in Sunnyvale in California. An airship training base was created there as well.
In the years 1942-1944, approximately 1400 airship pilots and 3000 support crew members were trained in the military airship crew training program and the airship military personnel grew from 430 to 12400. The US airships were produced by the Goodyear factory in Akron, Ohio. From 1942 till 1945, 154 airships were built for the US Navy (133 K-class, 10 L-class, 7 G-class, 4 M-class) and 5 L-class for civilian customers (serial number L-4 to L-8).
The primary airship tasks were patrol and escort of ships near the coastline. They also served as an organisation center for the convoys to direct ship movements and course, and were used during naval search and rescue operations. Rarer duties of the airships included aerophoto reconnaissance, naval mine-laying and mine-sweeping, parachute unit transport and deployment, cargo and personnel transportation. They were deemed quite successful in their duties with the highest combat readiness factor in the entire US air force (87%). They were extremely successful in their primary goal of anti-submarine warfare as the below numbers illustrate:
- 1942: 454 ships sunk near the US coast, 4-13 airships in service
- 1943: 65 ships sunk near the US coast, 17-53 airships in service
- 1944: 8 ships sunk near the US coast, 56-68 airships in service
- 1945: 3 ships sunk near the US coast, 53-48 airships in service
Not a single ship from a convoy escorted by airships was sunk. Airships engaged the submarines with depth charges, or rarely from other on-board weapons. They were very successful since they could match the slow speed of the submarine and bomb it until its destruction. Additionally, submerged submarines had no means of detecting an airship approaching.
Only one airship was ever destroyed by U-boat: on the night of 18/19 July 1943 a K-class airship (K-74) from ZP-21 division was patrolling the coastline near Florida. Using radar, the airship located a surfaced German submarine. Due to the failure of the depth charge release mechanism, the airship was unable to release the bombs during the bombing run and the German returned fire. The (K-74) received serious damage and was forced to make a water landing. The crew was rescued by patrol boats in the morning, but one crewman died from a shark attack. The U-Boat responsible was sunk a few hours later.
Some US airships saw action in the European war theater. The ZP-14 unit operating in the Mediterranean area from June 1944 completely denied the use of the Gibraltar Straits to Axis submarines. Airships from the ZP-12 unit took part in the sinking of the last U-Boat before German capitulation, sinking U-881 on 6 May 1945 together with destroyers Atherton and Mobery.
The Soviet Union used a single airship during the war. The W-12, built in 1939, entered service in 1942 for paratrooper training and equipment transport. It made 1432 runs with 300 metric tons of cargo until 1945. On 1 February 1945 the Soviets constructed a second airship, a Pobieda-class unit (used for mine-sweeping and wreckage clearing in the Black Sea) which later crashed on 21 January 1947. Another W-class - W-12bis Patriot was commissioned in 1947 and was mostly used for crew training, parades and propaganda.
Continued use
Although airships abandoned carrying passengers, they continued to be used for other purposes. In particular, the US Navy built hundreds of blimps for use in World War II. The most successful application of these airships was for convoy escort near the US coastline. During the war some 532 ships were sunk near the coast by submarines. In contrast, none of the 89,000 or so ships escorted by blimps was lost to enemy fire.
In recent years, the Zeppelin company has reentered the airship business. Their new model, designated the Zeppelin NT made its maiden flight on September 18, 1997. There are currently three NT aircraft flying. One has been sold to a Japanese company, and was planned to be flown to Japan in the summer of 2004. However, due to delays getting permission from the Russian government, the company decided to transport the airship to Japan by ship. An airship was flown over Athens during the 2004 Summer Olympics as part of security anti-terrorism measures.
Blimps continue to be used for advertising and as TV camera platforms at major sporting events.
Present-day research
Recently, several companies have begun exploring the possibilities of airships with their potentially huge lifting capacities, near-VTOL capabilities, and potentially lower freight costs, though none has demonstrated the economic viability yet.
In addition to the research on conventional blimp designs, several unconventional prototype designs continue to be investigated. One example is a design commissioned by the United States Military for a massive solar powered spy and communication blimp, 25 times larger than the Goodyear Blimp, which it is hoped will be able to carry tons of payload far above the range of antiaircraft weapons. The company developing the design, JP Aerospace, claims to have long-range plans to develop an "orbital airship" capable of lifting cargo into low earth orbit with a marginal transportation cost of $1 per short ton per mile of altitude.
Contracts are underway with Lockheed for high-altitude airships (HAAs). Airships are being investigated as a possible alternative to LEO (low Earth orbit) satellite communications. One proposed system involves sending unmanned airships high above cities at 70,000 feet (21 km). These aircraft would provide cellular voice and data service to a city with service similar to what LEOs provide. Due to the fact that these would be located in the stratosphere, one company currently working on this calls their proposed airships "Stratellites".
With the September 11 terrorist attacks, the U.S. military has been forced to reassess threats and evaluate strategies for aerial defence. Two major defense contractors are pitching the zeppelin as a potential piece in the homeland security jigsaw. Military planners envision unmanned airships as high-altitude radar platforms keeping watch for anything threatening U.S. airspace.
In February 2005, the US Department of Defense announced a research program named WALRUS (http://www.darpa.mil/tto/programs/walrus.html) to explore the development of very large airships. The primary goal of the research program is determine the feasibility of building an airship capable of carrying 500 short tons (450 metric tons) of payload a distance of 12,000 miles (20,000 km) and land on an unimproved location without the use of external ballast or ground equipment (e.g. masts.)
Fiction
Airships were a popular theme in scientific romance (prototypical science fiction) and adventure fiction published in the late 19th century and the earliest years of the 20th century. The theme of aeronautical exploration was most famously explored in this period by Jules Verne (The Clipper of the Clouds) and H. G. Wells (The War in the Air).
After the invention of the airplane, airships were largely forgotten by mainstream fiction, and today appear mainly in historical fiction and alternate history (particularly the steampunk genre and the work of Michael Moorcock, most notably The Warlord of the Air). In his "Anome" trilogy (The Anome aka The Faceless Man, The Brave Free Men, and The Asutra), Jack Vance depicts a system of airships tethered to unmanned monorail dolleys which keep them on fixed courses.
In Philip Pullman's trilogy His Dark Materials (The Golden Compass, The Subtle Knife, and The Amber Spyglass), which takes place in a parallel universe, airships are the only method of air travel. Airships' strengths and weaknesses are well portrayed in these novels: their great lifting capacity makes them valuable for transporting supplies and soldiers, but they are easily destroyed. Kenneth Oppel's novel Airborn, a young adult adventure set in an alternate history in which airship travel is common, won the 2004 Governor General's Award for children's literature.
David Brin's 1990 Hugo nominated near-future, post global-warming science fiction novel, "Earth" (set in 2038), portrays a future where there is regular use of airships for passenger transportation.
More than a few video games, such as Crimson Skies, Skies of Arcadia and the Final Fantasy series, utilize airships in their fictional worlds as a major mode of transportation. Also, in Command & Conquer Red Alert 2, the Soviets' most lethal conventional weapons are their extremely tough but slow Kirov Airships, which drop incredibly powerful bombs.
See also
|
Lists of Aircraft | Aircraft manufacturers | Aircraft engines | Aircraft engine manufacturers Airports | Airlines | Air forces | Aircraft weapons | Missiles | Timeline of aviation |
References
- Andrzej Morgała, Sterowce w II Wojnie Światowej, Lotnictwo 3/1992
External links
General
- Ferdinand von Zeppelin, US 621,195 (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=621,195.WKU.&OS=PN/621,195&RS=PN/621,195) Patent, "Navigable Ballon". March 14, 1899.
- Airship Home Page (http://spot.colorado.edu/~dziadeck/airship.html) - Provides a list of airship related websites. Also contains airship mailing list.
- Harold G. Dick Airship Collection (http://specialcollections.wichita.edu/collections/ms/99-01/99-1-bio.html) - biography of Harold G. Dick
- Postcards from Harold G. Dick Airship Collection (http://specialcollections.wichita.edu/exhibits/haldick/haldickpostcards.html)
- The Golden Age of the Great Passenger Airships: The Collection of Harold G. Dick (http://specialcollections.wichita.edu/exhibits/haldick/haldick.html)
- Airship and Blimp Resources (http://www.hotairship.com/) - This site focuses more on how to build your own airship with a particular focus on hot air airships (a.k.a "hotships")
- The Airship Association (http://www.airship-association.org/) - An association for people interested in all things to do with airships.
- The Association of Balloon and Airship Constructors (http://www89.pair.com/techinfo/ABAC/abac.htm) - Maintains an extensive technical library on airship technology old and new.
- Airship Association Net Links Page (http://www.airship-association.org/net.html) for a comprehensive list of companies throughout the world focusing on the development of airships.
- Airships Mailing List (http://lists.sculptors.com/mailman/listinfo/airships) - A forum for the discussion and design of lighter-than-air craft.
Manufacturers
- 21st Century Airships Inc. (http://www.21stcenturyairships.com) Manufactures unique spherical, finless airships using advanced materials and technologies. A 21st Century Airship craft currently holds the absolute FAI altitude record for airships of 6,234 m (20,450 ft).
- Advanced Technologies Group (http://www.atg-airships.com) a company developing a range of products such as UAV's - Unmanned Aerial Vehicles, heavier-than-air airships and HAPS' - High Altitude Platform Stations for telecommunication
- American Blimp Corporation (http://www.americanblimp.com) the only company in the world manufacturing airships on a scheduled production basis.
- GEFA-FLUG GmbH - The Air Company (http://www.gefa-flug.com) -- makers of hot air airships
- Zeppelin Luftschifftechnik GmbH (http://www.zeppelin-nt.com/index_e.htm) -- The Zeppelin Company and the Zeppelin NTda:Luftskib
de:Luftschiff es:Dirigible fa:هواایست fr:Aérostat fy:Loftskip it:dirigibile hu:Léghajó nl:Luchtschip ja:飛行船 pl:Sterowiec ru:Дирижабль fi:Ilmalaiva sv:Luftskepp zh:飞艇