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| Airship |
Airship 1931]]
An airship is a buoyant aircraft that can be steered and propelled through the air. Unlike aerodynamic aircraft which stay aloft by moving an airfoil through the air in order to produce lift, airships stay aloft primarily by means of a cavity (usually quite large) 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 interchangeably 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. Until the 1950s, all airships, except for those in the United States continued to use hydrogen because it offered greater lift and was cheaper than helium. The United States (until then the sole producer) was also unwilling to export helium because of its rarity and the fact it was considered a strategic material. However, hydrogen is flammable when mixed with air, a quality that has caused disasterous effects. The buoyancy provided by hydrogen is actually only about 10% greater than that of 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.
Types
balloon
- 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. It should be noted that most airships, when fully loaded with cargo and fuel, are typically heavier than air, and thus must use their propulsion system and shape to generate aerodynamic lift, necessary to stay aloft; technically making them hybrid airships. However, the term "hybrid airship" refers to craft that obtain a significant portion of their lift from aerodynamic lift and often require substantial take-off rolls before becoming airborne.
History
The development of airships was necessarily preceded by the development of balloons. See balloon (aircraft) for details.
Airship Pioneers
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 1-1/2 horsepower 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 170 foot long , 66,000 cubic foot airship covered 8 km (5 miles) in 23 minutes with the aid of an 8-1/2 horsepower electric motor.
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. Many inventors were inspired by Santos-Dumont's small airships and a veritable airship craze began world-wide. Many airship pioneers, such as the American Thomas Scott Baldwin financed their activities through passenger flights and public demonstration flights. Others, such as Walter Wellman and Melvin Vaniman set their sights on loftier goals, attempting two polar flights in 1907 and 1909, and two trans-atlantic flights in 1910 and 1912.
The beginning of the "Golden Age of Airships" was also marked with the launch of the Luftschiff Zeppelin LZ1 in July of 1900 which would lead to the most successful airships of all time. These Zeppelins 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). At the beginning of WW1 the Zeppelin airships had a cylindrical aluminium alloy frame and a fabric-covered hull containing separate gas cells. Multi-plane tail fins were used for control and stability, and two engine/crew cars hung beneath the hull driving propellers attached to the sides of the frame by means of long drive shafts. Additionally there was a passenger compartment (later a bomb bay) located halfway between the two cars.
Airships in the First World War
WW1
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.
Count Zeppelin and others in the German military believed they had found the ideal weapon with which to counteract British Naval superiority and strike at Britain itself. More realistic airship advocates believed the Zeppelin was a valuable long range scout/attack craft for naval operations. Raids began by the end of 1914, reached a first peak in 1915, and then were discontinued after 1917. Zeppelins proved to be terrifying but inaccurate weapons. Navigation, target selection and bomb-aiming proved to be difficult under the best of conditions. The darkness, high altitudes and clouds that were frequently encountered by 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'. In retrospect, advocates of the naval scouting role of the airship proved to be correct, and the land bombing campaign proved to be disastrous in terms of morale, men and material. Many pioneers of the German airship service died bravely, but needlessly in these propaganda missions. They also drew unwanted attention to the construction sheds which were bombed by the British Royal Naval Air Service.
Meanwhile the Royal Navy had recognised the need for small airships to counteract the submarine threat in coastal waters, and beginning in February 1915, began to deploy the SS (Sea Scout) class of blimp. These had a small envelope of 60-70,000 cu feet and at first utilised standard single engined planes (BE2c, Maurice Farman, Armstrong FK) shorn of wing and tail surfaces as an economy measure. Eventually more advanced blimps with purpose built cars, such as the C (Coastal), C
- (Coastal Star), NS (North Sea), SSP (Sea Scout Pusher), SSZ (Sea Scout Zero), SSE (Sea Scout Experimental) and SST (Sea Scout Twin) classes were developed. The NS class, after initial teething problems proved to be the largest and finest airships in British service. They had a gas capacity of 360,000 cu feet, a crew of 10 and an endurance of 24 hours. Six 230 lb bombs were carried, as well as 3-5 machine guns. British blimps were used for scouting, mine clearance, and submarine attack duties. During the war, the British built over 225 non-rigid airships, of which several were sold to the Russia, France, the US and Italy. Britain, in turn, purchased one M-type semi-rigid from Italy whose delivery was delayed until 1918. Eight rigid airships had been completed by the armistice, although several more were in an advanced state of completion by the wars end. The large number of trained crews, low attrition rate and constant experimentation handling techniques meant that at the wars end Britain was the world leader in non-rigid airship technology.
Royal Navy
Airplanes had essentially replaced airships as bombers by the end of the war, and Germany's remaining zeppelins were scuttled by their crews, 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.
Royal Navy]]
Airships in the Inter-war period
Airships using the Zeppelin construction method are sometimes referred to as zeppelins even if they had no connection to the Zeppelin business. Several airships of this kind were built in the USA and Britain in the 1920s and 1930s, mostly imitating original Zeppelin design derived from crashed or captured German World War I airships.
The British R33 and R34, for example, were near identical copies of the German L-33, which crashed virtually intact in Yorkshire on September 24 1916. Despite being almost three years out of date by the time they were launched in 1919, these sister ships were two of the most successful in British service. On July 2 1919 R34 began the first double crossing of the Atlantic by an aircraft. It landed at Mineola, Long Island on July 6, 1919 after 108 hours in the air. The return crossing commenced on July 8 because of concerns about mooring the ship in the open, and took 75 hours. Impressed, British leaders began to contemplate a fleet of airships that would link Britain to its far-flung colonies, but unfortunately post-war economic conditions lead to most airships being scrapped and trained personnel dispersed, until the R-100 and R-101 commenced construction in 1929.
Another example was the first American-built rigid dirigible ZR-1 "USS Shenandoah" , which flew in 1923, while the Los Angeles was under construction. 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 borrowed from ZR-1.
The Zeppelin works were saved by the purchase of what became called the USS Los Angeles by the United States Navy, paid for with "war reparations" money, owed according to the Versailles Treaty. The success of the Los Angeles encouraged the United States Navy to invest in larger 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.
Interestingly, the Graf Zeppelin burned un-pressurised blau gas, similar to propane, as fuel. Since its density was similar to that of air, it avoided the weight change when fuel was used.
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.
propane
Although USS 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 thanks to the issue of life jackets and inflatable rafts in the interval since the Akron disaster.
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
The greatest number of airships in use during the Second World War were blimps used to form anti-aircraft defences. Thousands were put up tethered to the ground by steel cables to form obstacles to German aircraft flying on bombing missions over England.
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, built 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 convoy escort near the US 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:
During the war some 532 ships were sunk near the coast by submarines.
- 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 of the 89,000 or so in convoys escorted by blimps was sunk by enemy fire. Airships engaged 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 as above.
1945
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.
Several companies, such as Cameron Balloons in Bristol, UK, build hot-air airships. These combine the structures of both hot-air balloons and small airships. The envelope is the normal 'cigar' shape, complete with tail fins, but is not inflated by helium, but by hot air (as in a balloon), which provides the lifting force. A small gondola, carrying the pilot (and sometimes between 1 and 3 passengers), a small engine and the burners to provide the hot air is suspended below the envelope, below an opening through which the burners protrode.
The advantages with the hot-air airship are that is costs less to buy and maintain than a standard modern blimp and it can be quickly deflated at the end of a flight, meaning it is easily transported on a trailer or truck, without the need for expensive storage arrangements. Such craft usually are very slow moving, with a typical top speed of 15-20 mph. They are used mainly for advertising, but several have been used in rainforests for wildlife observation, because they could easily be transported into remote areas.
Present-day research
Recently, several companies have begun exploring the possibilities of airships with their potentially huge lifting capacities, near-VTOL (Vertical Take-Off and Landing) capabilities, and potentially lower freight costs, though none has demonstrated 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 the WALRUS HULA [http://www.darpa.mil/tto/programs/walrus.html] [http://www.defenseindustrydaily.com/2005/10/us-cbo-gives-ok-to-hula-airships-for-airlift/index.php] 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.
In Theodore Judson's post-apocalyptic Fitzpatrick's War, the neo-feudal Yukon Confederacy makes heavy use of airships as military and civilian transports.
Kim Stanley Robinson in his Mars Trilogy envisages rigid airships being used as a major form of transport for the emerging settlements of Mars.
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. [http://www.airborn.ca/ www.airborn.ca]. There is also a sequel, Skybreaker.
In Philip Reeve's Hungry City Chronicles , which takes place in the distant future, airships are the primary form of travel because of the mobile nature of cities in the books. In the series, it is mentioned that airship technology had advanced beyond the imaginations of the "Ancients". Airships include freighters, sky yachts, fighter airships and immense air destroyers.
In Jasper Fforde's Thursday Next series the airship is a significant and popular form of transport.
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.
China Miéville's Bas Lag novels (Perdido Street Station, The Scar, Iron Council) feature airships ("dirigibles") as a common mode of transport; they are used as taxis and military scouts. The Scar featured two large war airships controlled by the pirate city of Armada: The Arrogance (a captured New Crobuzon airship used as a crow's nest) and the Trident.
Philip Jose Farmer's Riverworld novels feature a giant rigid and several non-rigid airships which are used to reach the north pole of the Riverworld
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. (In some cases (most notably in the Final Fantasy series), the "airship" is actually a ship with wings, propellers, etc..) 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
- List of airship accidents
- List of Zeppelins
- Evolutionary Air and Space Global Laser Engagement
- Stratellite
References
- Rich Archbold and Ken Marshall,Hindenberg, an Illustrated History, 1994 ISBN 0446517844
- William F. Althoff , USS Los Angeles: The Navy's Venerable Airship and Aviation Technology , 2003, ISBN 1574886207
- Peter Brooks , Zeppelin: Rigid Airships 1893-1940 , 2004, ISBN 0851778453
- Charles P. Burgess, Airship Design, (1927) 2004 ISBN 1410211738
- Wilbur Cross, Disaster at the Pole, 2002 ISBN 1-58574-496-4
- Arthur Frederick et al., Airship saga: The history of airships seen through the eyes of the men who designed, built, and flew them , 1982, ISBN 0713710012
- Manfred Griehl and Joachim Dressel, Zeppelin! The German Airship Story, 1990 ISBN 1-85409-045-3
- Gabriel Alexander Khoury (Editor), Airship Technology (Cambridge Aerospace Series) , 2004, ISBN 0521607531
- Alexander McKee, Ice crash, 1980, ISBN 0312403828
- Andrzej Morgała, Sterowce w II Wojnie Światowej (Airships in the Second World War), Lotnictwo, 1992
- Ces Mowthorpe, Battlebags: British Airships of the First World War, 1995 ISBN 0905-778-138
- US War Department , Airship Aerodynamics: Technical Manual, (1941) 2003 , ISBN 1410206149
External links
General
- [http://spot.colorado.edu/~dziadeck/airship.html Airship Home Page] - Provides a list of airship related websites. Also contains airship mailing list.
- [http://www.hotairship.com/ Airship and Blimp Resources] - This site focuses more on how to build your own airship with a particular focus on hot air airships (a.k.a "hotships")
- [http://lists.sculptors.com/mailman/listinfo/airships Airships Mailing List] - A forum for the discussion and design of lighter-than-air craft.
Associations
- [http://www.airship-association.org/ The Airship Association] - British based association for people interested in all things to do with airships.
- [http://www.blimpinfo.com/ Lighter than Air Society] - US based association for people interested in all things to do with airships.
- [http://www89.pair.com/techinfo/ABAC/abac.htm The Association of Balloon and Airship Constructors] - Maintains an extensive technical library on airship technology old and new.
Historical
- [http://www.nlhs.com/ Navy Lakehurst Historical Society] - airship history with a focus on activities at the historically most active airship base in the US.
- [http://www.aht.ndirect.co.uk/ Airships Online] - website of the Airships Heritage Trust. It contains an extensive history relating British Airships from 1900 to the present day.
- [http://www.history.navy.mil/branches/lta-m.html US Navy Airship History]
- Ferdinand von Zeppelin, US [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/621,195 621,195] Patent, "Navigable Ballon". March 14, 1899.
- [http://specialcollections.wichita.edu/collections/ms/99-01/99-1-bio.html Harold G. Dick Airship Collection] - biography of Harold G. Dick
- [http://specialcollections.wichita.edu/exhibits/haldick/haldickpostcards.html Postcards from Harold G. Dick Airship Collection]
- [http://specialcollections.wichita.edu/exhibits/haldick/haldick.html The Golden Age of the Great Passenger Airships: The Collection of Harold G. Dick]
- [http://www.centennialofflight.gov/essay/Lighter_than_air/Beginning_of_the_Dirigible/LTA6.htm US Centennial of Flight Commission]
Manufacturers and commercial operators
- [http://www.airship-association.org/net.html Airship Association Net Links Page] for a comprehensive list of companies throughout the world focusing on the development of airships.
- [http://www.americanblimp.com American Blimp Corporation] In association with The Lightships Group, this company builds and operates the world's largest fleet of airships.
- [http://www.gefa-flug.com GEFA-FLUG GmbH - The Air Company] -- makers of hot air airships
- [http://www.zeppelin-nt.com/index_e.htm Zeppelin Luftschifftechnik GmbH] -- The Zeppelin Company and the Zeppelin NT.
- [http://www.goodyearblimp.com/ The Goodyear Blimps] -- The most famous modern airships. These aircraft are owned and operated by the Lockheed Martin Corporation.
- [http://www.airshipman.com/ Airship Management Services] -- Operators of several type-certified airships including the Fuji Blimp. These aircraft were originally built by the Westinghouse Corporation with the designation Skyship 600. They also own and operate a sightseeing airship in Switzerland under the name [http://www.skycruiser.co.uk/ Skycruiser Switzerland]
- [http://www.cameronballoons.co.uk/airships.htm Cameron Airships] -- Hot air airships manufactured by Cameron Balloon - the world's largest manufacturer of hot air balloons.
- [http://www.lindstrand.co.uk/Airship.html Lindstrand Airships] - Hot air airships manufactured by hot air balloon company Lindsrand - a subsidiary of Cameron Balloon.
- [http://aas.augurballoons.com/ Augur Aerostatic Systems] -- Russian company making both gas and hot air airships
Experiments, prototypes and one-offs
- [http://www.21stcenturyairships.com 21st Century Airships Inc.] Developers of spherical, finless airships. From June 12, 2003 until December 13, 2004, a 21st Century Airship craft held the absolute FAI altitude record for airships of 6,234 m (20,450 ft).
- [http://www.aerosml.com/main.htm Aeros Corporation] - In addition to producing several small airships, this company is one of the winners of Phase I funding from DARPA for Project WALRUS.
- [http://www.usairships.com/ USA Airships]
- [http://www.myairship.com/database/whitedwarf.html White Dwarf] - A small, human-powered airship
- [http://www.endlessflyers.com/nice-calvi.htm Zeppy] - Human powered airship -- website in French.
Designs under development
- [http://www.lockheedmartin.com/wms/findPage.do?dsp=fec&ci=14477&rsbci=12972&fti=0&ti=0&sc=400 Lockheed-Martin HAA Project]
- [http://www.sanswire.com/ Sanswire Stratellite]
- [http://www.dynalifter.com/ Dynalifter]
- [http://www.atg-airships.com Advanced Technologies Group] Until August of 2005, when it went into receivership, this company was developing a range of products such as UAV's - Unmanned Aerial Vehicles, heavier-than-air airships and HAPS' - High Altitude Platform Stations for telecommunication.
Proposed designs
- [http://www.airship.org/ Vertical Airships]
- [http://rigid.tripod.com/english.html Airship Holland]
- [http://www.nagyairship.com/ Nagy High Speed Airship]
- [http://www.millenniumairship.com/ Millennium Airship]
- [http://www.quantumaerostatics.com/ Quantum Aerostatics]
- [http://www.hacinc.us/ Hybrid Aircraft Corporation]
- [http://www.ahausa.com/ Advanced Hybrid Aircraft]
Category:Airships
Category:Aeronautics
ja:飛行船
BuoyancyIn physics, buoyancy is an upward force on an object immersed in a fluid (i.e. a liquid or a gas), enabling it to float or at least to appear to become lighter. If the buoyancy exceeds the weight, then the object floats; if the weight exceeds the buoyancy, the object sinks. If the buoyancy equals the weight, the body has neutral buoyancy and may remain at its level. If its compressibility is less than that of the surrounding fluid, it is in stable equilibrium and will, indeed, remain at rest, but if its compressibility is greater, its equilibrium is unstable, and it will rise and expand on the slightest upward perturbation, but fall and compress on the slightest downward perturbation. It was the ancient Greek, Archimedes of Syracuse, who first discovered the law of buoyancy, sometimes called Archimedes' principle:
:The buoyant force is equal to the weight of the displaced fluid.
Typically, the weight of the displaced fluid is directly proportional to the volume of their displaced fluid (Specifically if the surrounding fluid is of uniform density.) Thus, among objects with equal masses, the one with greater volume has greater buoyancy.
Suppose a rock's weight is measured at 10 Newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water whose weight is 3 Newtons. The force it then exerts on the string from which it hangs will be 10 Newtons minus the 3 Newtons of buoyant force: 10 - 3 = 7 Newtons.
Buoyancy is the underlying principle of many vehicles such as boats, ships, balloons, and airships.
Density
If the weight of an object is less than the weight of the fluid that the object would displace if it was fully submerged, then the object is less dense than the fluid and it floats at a level so it displaces the same weight of fluid as the weight of the object.
An object made of a material of higher density than the fluid, e.g. a metal object in water, can still float if it has a suitable shape (e.g. a hollow which is open upwards or downwards) that keeps a large enough volume of air below the surface level of the fluid. In that case, for the average density mentioned above, the air is included also, which may reduce this density to less than that of the fluid.
Acceleration and energy
Although Archimedes' principle gives the force on a buoyant object, this does not determine the related acceleration of the object in the usual way over Newton's first law. This is for two reasons: Not only has the mass of the object to be accelerated but also the mass of the displaced fluid. One can compare the situation to a scale, where the weight on one side is given by the object, and the weight on the other side by the displaced fluid element. Depending on which of the two is heavier, one side of the scale will drop and the other rise, but since both sides are rigidly connected, both masses have to be accelerated together at the same rate (albeit in opposite directions). The second reason is that viscosity dissipates energy, so that, even taking into account the kinetic and potential energies of the object and the fluid (but ignoring heat energy), energy is lost to viscosity, a form of friction.
It is obvious that without taking the displaced fluid element into account, energy would not be conserved during the buoyant motion of an object as it would gain both potential and kinetic energy when rising in the fluid.
See also
- Buoyancy compensator
- Diving weighting system
- Flotation
- Hull (ship)
- Hydrometer
- Lighter than air
- Naval architecture
- Pontoon
- Quicksand
Category:Fluid mechanics
Category:Diving
Category:Introductory physics
Category:Ship construction
ja:%E6%B5%AE%E5%8A%9B
ms:Keapungan
AircraftAn aircraft is any machine capable of atmospheric flight.
flight. This is a wide-bodied long-haul aircraft]]
Categories and classification
Aircraft fall into two broad categories:
Heavier than air
- Heavier than air aerodynes, including autogyros, helicopters and variants, and conventional fixed-wing aircraft: aeroplanes in Commonwealth English (excluding Canada), airplanes in North American English. Fixed-wing aircraft generally use an internal-combustion engine in the form of a piston engine (with a propeller) or a turbine engine (jet or turboprop), to provide thrust that moves the craft forward through the air. The movement of air over the airfoil produces lift that causes the aircraft to fly. Exceptions are gliders which have no engines and gain their thrust, initially, from winches or tugs and then from gravity and thermal currents. For a glider to maintain its forward speed it must descend in relation to the air (but not necessarily in relation to the ground). Helicopters and autogyros use a spinning rotor (a rotary wing) to provide lift; helicopters also use the rotor to provide thrust. The abbreviation VTOL is applied to aircraft other than helicopters that can take off or land vertically. STOL stands for Short Take Off and Landing. Mainly used internationally.
Lighter than air
STOL
- Lighter than air aerostats: hot air balloons and airships. Aerostats use buoyancy to float in the air in much the same manner as ships float on the water. In particular, these aircraft use a relatively low density gas such as helium, hydrogen or heated air, to displace the air around the craft. The distinction between a balloon and an airship is that an airship has some means of controlling both its forward motion and steering itself, while balloons are carried along with the wind.
Types of aircraft
:See also: List of aircraft
There are several ways to classify aircraft. Below, we describe classifications by design, propulsion and usage.
By design
A first division by design among aircraft is between lighter-than-air, aerostat, and heavier-than-air aircraft, aerodyne.
Examples of lighter-than-air aircraft include non-steerable balloons, such as hot air balloons and gas balloons, and airships (sometimes called dirigible balloons) such as blimps (that have non-rigid construction) and rigid airships that have a rigid frame. The most successful type of rigid airship was the Zeppelin, although there were some accidents such as the Hindenburg Zeppelin which was destroyed in a fire at Lakehurst, NJ, in 1937.
In heavier-than-air aircraft, there are two ways to produce lift: aerodynamic lift and engine lift. In the case of aerodynamic lift, the aircraft is kept in the air by wings or rotors (see aerodynamics). With engine lift, the aircraft defeats gravity by use of vertical thrust greater than its weight.
Examples of engine lift aircraft are rockets, and VTOL aircraft such as the Hawker-Siddeley Harrier.
Among aerodynamically lifted aircraft, most fall in the category of fixed-wing aircraft, where horizontal airfoils produce lift, by profiting from airflow patterns determined by Bernoulli's equation and, to some extent, the Coanda effect.
The forerunner of these type of aircraft is the kite. Kites depend upon the tension between the cord which anchors it to the ground and the force of the wind currents. Much aerodynamic work was done with kites until test aircraft, wind tunnels and now computer modelling programs became available.
In a "conventional" configuration, the lift surfaces are placed in front of a control surface or tailplane. The other configuration is the canard where small horizontal control surfaces are placed forward of the wings, near the nose of the aircraft. Canards are becoming more common as supersonic aerodynamics grows more mature and because the forward surface contributes lift during straight-and-level flight.
The number of lift surfaces varied in the pre-1950 period, as biplanes (two wings) and triplanes (three wings) were numerous in the early days of aviation. Subsequently most aircraft are monoplanes. This is principally an improvement in structures and not aerodynamics.
Other possibilities include the delta-wing, where lift and horizontal control surfaces are often combined, and the flying wing, where there is no separate vertical control surface (e.g. the B-2 Spirit).
A variable geometry ('swing-wing') has also been employed in a few examples of combat aircraft (the F-111, Panavia Tornado, F-14 Tomcat and B-1 Lancer, among others).
The lifting body configuration is where the body itself produce lift. So far the only significant practical application of the lifting body is in the Space Shuttle, but many aircraft generate lift from nothing other than wings alone.
A second category of aerodynamically lifted aircraft are the rotary-wing aircraft. Here, the lift is provided by rotating aerofoils or rotors. The best-known examples are the helicopter, the autogyro and the tiltrotor aircraft (such as the V-22 Osprey). Some craft have reaction-powered rotors with gas jets at the tips but most have one or more lift rotors powered from engine-driven shafts.
A further category might encompass the wing-in-ground-effect types, for example the Russian ekranoplan also nicknamed the "Caspian Sea Monster" and hovercraft; most of the latter employing a skirt and achieving limited ground or water clearance to reduce friction and achieve speeds above those achieved by boats of similar weight.
A recent innovation is a completely new class of aircraft, the fan wing. This uses a fixed wing with a forced airflow produced by cylindrical fans mounted above. It is (2005) in development in the United Kingdom.
And finally the flapping-wing ornithopter is a category of its own. These designs may have potential but are not yet practical.
By propulsion
ornithopter adapted as a floatplane]]
Some types of aircraft, such as the balloon or glider, do not have any propulsion. Balloons drift with the wind, though normally the pilot can control the altitude either by heating the air or by releasing ballast, giving some directional control (since the wind direction changes with altitude). For gliders, takeoff takes place from a high location, or the aircraft is pulled into the air by a ground-based winch or vehicle, or towed aloft by a powered "tug" aircraft. Airships combine a balloon's buoyancy with some kind of propulsion, usually propeller driven.
Until World War II, the internal combustion piston engine was virtually the only type of propulsion used for powered aircraft. (See also: Aircraft engine.) The piston engine is still used in the majority of aircraft produced, since it is efficient at the lower altitudes used by small aircraft, but the radial engine (with the cylinders arranged in a circle around the crankshaft) has largely given way to the horizontally-opposed engine (with the cylinders lined up on two sides of the crankshaft). Water cooled V engines, as used in automobiles, were common in high speed aircraft, until they were replaced by jet and turbine power. Piston engines typically operate using avgas or regular gasoline, though some new ones are being designed to operate on diesel or jet fuel. Piston engines normally become less efficient above 7,000-8,000 ft (2100-2400 m) above sea level because there is less oxygen available for combustion; to solve that problem, some piston engines have mechanically powered compressors (blowers) or turbine-powered turbochargers or turbonormalizers that compress the air before feeding it into the engine; these piston engines can often operate efficiently at 20,000 ft (6100 m) above sea level or higher, altitudes that require the use of supplemental oxygen or cabin pressurisation.
During the forties and especially following the 1973 energy crisis, development work was done on propellers with swept tips or even scimitar-shaped blades for use in high-speed commercial and military transports.
Pressurised aircraft, however, are more likely to use the turbine engine, since it is naturally efficient at higher altitudes and can operate above 40,000 ft. Helicopters also typically use turbine engines. In addition to turbine engines like the turboprop and turbojet, other types of high-altitude, high-performance engines have included the ramjet and the pulse jet. Rocket aircrafts have occasionally been experimented with. They are restricted to rather specialised niches, such as spaceflight, where no oxygen is available for combustion (rockets carry their own oxygen).
By usage
The major distinction in aircraft usage is between military aviation, which includes all uses of aircraft for military purposes (such as combat, patrolling, search and rescue, reconnaissance, transport, and training), and civil aviation, which includes all uses of aircraft for non-military purposes.
Combat aircraft like fighters or bombers represent only a minority of the category. Many civil aircraft have been produced in separate models for military use, such as the civil Douglas DC-3 airliner, which became the military C-47/C-53/R4D transport in the U.S. military and the Dakota in Britain and the Commonwealth. Even the little fabric-covered two-seater Piper J3 Cub had a military version, the L-4 liaison, observation and trainer aircraft. In the past, gliders and balloons have also been used as military aircraft; for example, balloons were used for observation during the American Civil War and World War I, and cargo gliders were used during World War II to land intruding German troops in many European countries in the 1940/42 period, while Allied troops used them in Europe after D-Day .
Combat aircraft themselves, though used a handful of times for reconnaissance and surveillance during the Italo-Turkish War, did not come into widespread use until the Balkan War when first air-dropped bomb was invented and widely used by Bulgarian air force against Turkey. During World War I many types of aircraft were adapted for attacking the ground or enemy vehicles/ships/guns/aircraft, and the first aircraft designed as bombers were born. In order to prevent the enemy from bombing, fighter aircraft were developed to intercept and shoot down enemy aircraft. Tankers were developed after World War II to refuel other aircraft in mid-air, thus increasing their operational range. By the time of the Vietnam War, helicopters had come into widespread military use, especially for transporting and supporting ground troops.
Civil aviation
helicopter]]
Civil aviation includes both scheduled airline flights and general aviation, a catch-all covering other kinds of private and commercial use. The vast majority of flights flown around the world each day belong to the general aviation category, ranging from recreational balloon flying to civilian flight training to business trips to firefighting to medevac flights to cargo transportation on freight aircraft.
Within general aviation, the major distinction is between private flights (where the pilot is not paid for time or expenses) and commercial flights (where the pilot is paid by a customer or employer). Private pilots use aircraft primarily for personal travel, business travel, or recreation. Usually these private pilots own their own aircraft and take out loans from banks or specialized lenders to purchase them. Commercial general aviation pilots use aircraft for a wide range of tasks, such as flight training, pipeline surveying, passenger and freight transport, policing, crop dusting, and medical transport (medevac). Piston-powered propeller aircraft (single-engine or twin-engine) are especially common for both private and commercial general aviation, but even private pilots occasionally own and operate helicopters like the Bell JetRanger or turboprops like the Beechcraft King Air. Business jets are typically flown by commercial pilots, although there is a new generation of small jets arriving soon for private pilots.
Related topics
- List of aircraft by category
- List of aircraft by date and usage category
- List of civil aircraft
- List of helicopter models
- List of military aircraft
- List of World War II jet aircraft
- List of aircraft engines
- List of aircraft engine manufacturers (alphabetical)
- Aerial refuelling
- Aeronautics
- Aircraft carrier
- Aircraft spotting
- Airline call signs
- Airliner
- Air safety
- Aviation
- Contrail
- First flying machine
- Flight controls
- Flight instruments
- Gliding
- Lifting body
- List of early flying machines
- Model aircraft
- Mobile phones on aircraft
- Spacecraft propulsion
- Spacecraft
- Steam aircraft
- Successful aircraft types
- Undercarriage
- Wright brothers
- List of aviation, aerospace and aeronautical terms
External links
History
- [http://www.nasm.si.edu/ Smithsonian Air and Space Museum] - Excellent online collection with a particular focus on history of aircraft and spacecraft
- [http://invention.psychology.msstate.edu/Tale_of_Airplane/taleplane.html Virtual Museum]
- [http://www.centennialofflight.gov/essay/Prehistory/PH-OV.htm Prehistory of Powered Flight]
- [http://www.hq.nasa.gov/office/pao/History/SP-468/contents.htm The Evolution of Modern Aircraft (NASA)]
- [http://www.check-six.com Check-Six] - Information on historic aircraft crashes including the X-15 and Flying Wing
- [http://www.anythingplanes.net Aircraft community ]
Information
- [http://www.aircraft-info.net Aircraft-Info.net]
- [http://www.airliners.net/info/ Airliners.net]
- [http://www.HomebuiltAircraft.com HomebuiltAircraft.com]- Information Portal about Homebuilt Aircraft
- [http://www.DefenceTalk.com Airforces ]
- [http://www.challoner.com/aviation/index.html Series of Photo Essays on British Aviation]
- [http://www.usenet-replayer.com/webrings/aviation.html Pictures of Aircraft] published on Usenet
- [http://www.sulman4paf.tk PAF Procedures and Information, Wallpapers, Picture Gallery, Updated News]
Patents
- US[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=821393.WKU.&OS=PN/821393&RS=PN/821393 821393] -- Flying machine -- O. & W. Wright
Category:Aircraft
Category:Aviation
zh-min-nan:Hui-hêng-ki
ko:항공기
ms:Pesawat udara
ja:航空機
simple:Aircraft
Density: For other senses of "density", see density (disambiguation).
Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The average density of an object equals its total mass divided by its total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water).
The SI unit of density is the kilogram per cubic metre (kg/m3)
:
where
:ρ is the object's density (measured in kilograms per cubic metre)
:m is the object's total mass (measured in kilograms)
:V is the object's total volume (measured in cubic metres)
Under specified conditions of temperature and pressure, density of a fluid is defined as described above. However, the density of a solid material can be different, depending on exactly how it is defined. Take sand for example. If you gently fill a container with sand, and divide the mass of sand by the container volume you get a value termed loose bulk density. If you took this same container and tapped on it repeatedly, allowing the sand to settle and pack together, and then calculate the results, you get a value termed tapped or packed bulk density. Tapped bulk density is always greater than or equal to loose bulk density. In both types of bulk density, some of the volume is taken up by the spaces between the grains of sand.
Also, in terms of candy making, density is affected by the melting and cooling processes. Loose granular sugar, like sand, contains a lot of air and is not tightly packed, but when it has melted and starts to boil, the sugar loses its granularity and entrained air and becomes a fluid. When you mold it to make a smaller, compacted shape, the syrup tightens up and loses more air. As it cools, it contracts and gains moisture, making the already heavy candy even more dense.
Other units
Density in terms of the SI base units is expressed in terms of kilograms per cubic metre (kg/m³). Other units fully within the SI include grams per cubic centimetre (g/cm³) and megagrams per cubic metre (Mg/m³). Since both the litre and the tonne or metric ton are also acceptable for use with the SI, a wide variety of units such as kilograms per litre (kg/L) are also used.
Imperial units or U.S. customary units, the units of density include pounds per cubic foot (lb/ft³), pounds per cubic yard (lb/yd³), pounds per cubic inch (lb/in³), ounces per cubic inch (oz/in³), pounds per gallon (for U.S. or imperial gallons) (lb/gal), pounds per U.S. bushel (lb/bu), in some engineering calculations slugs per cubic foot, and other less common units.
The maximum density of pure water at a pressure of one standard atmosphere is 999.972 kg/m³; this occurs at a temperature of about 3.98 °C (277.13 K).
From 1901 to 1964, a litre was defined as exactly the volume of 1 kg of water at maximum density, and the maximum density of pure water was 1.000 000 kg/L (now 0.999 972 kg/L). However, while that definition of the litre was in effect, just as it is now, the maximum density of pure water was 0.999 972 kg/dm3. During that period students had to learn the esoteric fact that a cubic centimetre and a millilitre were slightly different volumes, with 1 mL = 1.000 028 cm3. (often stated as 1.000 027 cm3 in earlier literature).
Measurement of density
A common device for measuring fluid density is a pycnometer. A device for measuring absolute density of a solid is a gas pycnometer.
Density of substances
Perhaps the highest density known is reached in neutron star matter (see neutronium). The singularity at the centre of a black hole, according to general relativity, does not have any volume, so its density is undefined.
The most dense naturally occurring substance on Earth is iridium, at about 22650 kg/m3.
A table of densities of various substances:
Note the low density of aluminium compared to most other metals. For this reason, aircraft are made of aluminium. Also note that air has a nonzero, albeit small, density. Aerogel is the world's lightest solid.
See also
- ISO 31: volumic mass
- Dord
- Standard temperature and pressure
- Relative density (specific gravity)
- Charge density
- Energy density
- Population density
Category:Continuum mechanics
Category:Introductory physics
Category:Fundamental physics concepts
Category:Physical quantity
Category:Physical chemistry
ms:Ketumpatan
ja:密度
th:ความหนาแน่น
Genericized trademarkA genericized trademark (Commonwealth English genericised trade mark), sometimes known as a generic trade mark, generic descriptor or proprietary eponym, is a trademark or brand name which has become synonymous with the general or formal term for a particular type of product or service, to the extent that it often replaces this term in colloquial usage.
Trademarks, unlike copyrights and patents, must be actively used in order to maintain strong legal rights. By comparison, a copyright or patent holder does not necessarily need to use their creation in order to maintain their rights. A trademark owner must therefore be careful not to lose control of how its trademark is used. If a trademark is successful in gaining mind share and enters common use in the marketplace, it may become generic.
Once this point is reached it may no longer be possible to legally enforce any rights which attach to the use or registration of the trademark. One term for the diminishing or loss of these rights is genericide. Genericide typically occurs over a period of time where the trademark owner does not maintain or enforce its proprietary rights (eg. by using the mark, or by pursuing infringement action).
For example, if a trademark owner does not police the use of its trademark in relation to a new product, by preventing third parties using the trademark to describe their similar products, and the general public starts using the trademark as the generic name for the product, the trademark may become a genericized trademark. Thomas Edison's mimeograph is a classic example.
Legal concepts
The legal determination of whether a mark has become generic will usually arise in the context of an attempt to invalidate or otherwise cancel a registered trademark, which may be done by applying to the relevant government trademarks office (or trademarks registry) or court. In this context a genericized trademark is a trademark which no longer serves to uniquely identify the commercial source or origin of a product or service.
As the determination of whether a trademark is a "genericized trademark" in any other context tends to be a subjective assessment, there is some uncertainty as to what the term actually encompasses. Nevertheless, there is a similar degree of "genericity" between a trademark registration which is deemed unenforceable (because the trademark no longer exclusively identifies the trademark owner as the commercial source of its products or services), and a former trademark which is widely considered generic by the public.
It is important to note that regardless of whether trademarks are perceived as being "genericized trademarks", or whether well known trademarks are used in a generic manner, a trademark does not become generic simply as a result of popular usage, particularly if there has been no legal determination on the status of a trademark, and the trademark owner maintains and enforces their rights.
While trademark owners want to maximize the popularity of their trademarks, there is no business reason for deliberately wanting a valid trademark to become a "genericized trademark". If the goal was to simply popularize a term, the trademark owner could have simply not trademarked the term in the first place. Unless business conditions change such that the owner no longer needs to maintain the trademark, lost of a trademark through "genericide" is not desirable.
Terminology
The terms "genericide" and "genericized trademark" are not terms of art; legally, "genericide" is a "malapropism". Alternative terms have been suggested by various commentators, such as the judge in Plasticolor Molded Products v. Ford Motor Company, who suggested "genericization" or "trademarkicide" [http://print.google.com/print?id=e67o2-S_riMC&lpg=73&dq=genericide&prev=http://print.google.com/print%3Fie%3DUTF-8%26q%3Dgenericide%26btnG%3DSearch&pg=74&sig=TfNmUH7tJvkVUz-VCyjqJcIOw4Q], Cecil Adams who suggested "brand eponym" in The Straight Dope [http://www.straightdope.com/mailbag/meponym.html], and others who have suggested "proprietary eponym". These latter terms and the term "genericized trademark" have not yet been used in legal literature whereas "genericide" has.
Avoiding genericide
Trademark owners should not use their trademark as verbs or noun, implying the word is generic. Likewise, using the trademark as a plural or possessive (i.e. a noun) will imply the trademark is generic (unless the mark itself is possessive or plural, e.g., "Friendly's" restaurants). If the trademark is associated with a new invention, the trademark owner should use a descriptive term for the product that can be distinguished from the trademark for the product.
Where a trademark is used generically a trademark owner may need to take special proactive measures in order to retain exclusive rights to the trademark. Xerox provides one successful example of a company which was able to prevent the genericide of its core trademark through an extensive marketing campaign advising consumers to "photocopy" instead of "Xeroxing" documents (the brand did become generic in Russian, though -- see below). Another common practice amongst trademark owners is to follow their trademark with the word "brand" to help define the word as a trademark. Johnson & Johnson changed the lyrics of their BAND-AID television commercial jingle from, "I am stuck on BAND-AIDs, 'cause BAND-AID's stuck on me" to "I am stuck on BAND-AID brand, 'cause BAND-AID's stuck on me."
As generic use of a trademark typically corresponds to how well-known a trademark has become, some trademark owners believe that it is useful to achieve a level of genericity, or may otherwise overlook a certain level of generic use. However, generic trademark use of any kind presents an inherent risk to maintaining strong (ie. enforceable) trademark rights.
European Union
Since 2003 the European Union has actively sought to restrict the use of geographical indications by third parties outside the EU. Although a GI for specialty food or drink may be generic, a GI is not a trademark because it does not serve to exclusively identify a specific commercial enterprise, and therefore cannot constitute a genericized trademark.
The extension of protection for geographical indications is somewhat controversial because a GI may have been registered as a trademark elsewhere. For example, if Parma Ham was part of a trademark registered in Canada by a Canadian manufacturer, ham manufacturers actually located in Parma, Italy might be unable to use this name in Canada.
Other affected products include Champagne, Bordeaux and many other wine names, Roquefort, Parmesan and Feta cheese, and Scotch whisky. In the 1990s the Parma consortium successfully sued the Asda supermarket chain to prevent it using the description Parma ham on prosciutto produced in Parma but sliced outside the region. See also Protected Designation of Origin.
List of genericized trademarks
The following list comprises those marks which were originally created and used as trademarks, but which have subsequently become entirely synonymous with the common name of the relevant product or service. Marks which appear in this list have become so generic that their former status as proprietary trademarks is often unknown to the general public. Such marks may therefore be considered "fully generic", whereas marks which are at risk of becoming generic are listed in the next section.
If any of the original registrations for the trademarks appearing in this list have not yet expired or been cancelled, it is unlikely that the owners of the registrations would be able to successfully enforce their registered trade mark rights against third parties.
- Allen wrench (or Allen key)- hexagonal screwdriver (A rarity among generic words, 'Allen wrench' is no longer trademarked, but is still capitalized because it is named after a company)
- aspirin - ASA (acetylsalicylic acid; remains as a registered trademark in many places around the world in the name of Bayer, but not in the United States)
- bikini - two-piece swimsuit for women
- brassiere - women's undergarment used for breast support
- BX - flexible, metal-armored electrical cable
- cellophane - transparent paper
- celluloid - film material
- cola - soft drink; genericized part of Coca-Cola (see definition 2 at [http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=cola]) Arguably, the word "cola" had a weak claim to the originality required for trademark status in the first place, since it is a logical name for a beverage derived from the cola nut. In some parts of the United States, "coke" is a generic word for any soft drink.
- comptometer - adding machine
- crock pot - Crock-Pot is sold by [http://www.ochef.com/764.htm Rival Industries], but "crock pot" and "crockpot" are common synonyms used by cooks to describe slow cookers.
- doona - Australian brand of duvets
- dry ice - frozen carbon dioxide
- escalator - moving staircase
- gramophone - record player
- granola - oat and fruit mixture
- heroin - diacetylmorphine; originally registered by Bayer as a pain reliever
- hula hoop - toy hoop; originally made of various materials, generic name trademarked by Wham-O when it was redesigned in plastic in the late 1950's
- jake brake - truck braking device
- jungle gym - play structure (from 'Junglegym')
- kiwi fruit - formerly known as "Chinese gooseberries"; new name not trademarked, but Zespri trademark later introduced for New Zealand kiwis
- LP - long playing record
- lanolin - purified, wax-like substance from sheep's wool
- laundromat - Originally a term developed by Westinghouse for washing machines, but usually considered a generic term for a coin operated laundry
- linoleum - floor covering
- merry widow - strapless corset
- milk of magnesia - saline-type laxative; Phillip's
- mimeograph - reproduction machine
- pilates exercise system - trademark formally cancelled by court in 2000
- plasterboard - formed gypsum building material
- pianola - player piano
- pogo stick - bouncing stick (trademark was one word, 'Pogo')
- spandex - polyurethane fiber[http://dictionary.cambridge.org/define.asp?key=76142&dict=CALD]; an anagram of "expands" [http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=spandex]; DuPont later introduced new trademark, Lycra
- tabloid - originally a type of medication
- tarmac (or tarmacadam) - road surfacing; the word tarmac is sometimes used to refer to airport runways, but properly it is the hardstanding or parking area that is the tarmac
- touch-tone - dual tone multi-frequency telephone signaling. AT&T states "formerly a trademark of AT&T"[http://www.att.com/gov/contracts/maas/services/centrex_variable.html]
- trampoline - sports equipment
- webster's dictionary - the publishers with the strongest link to the original are Merriam-Webster, but they have a trademark only on "Merriam-Webster", and other dictionaries are legally published as "Webster's Dictionary" [http://www.m-w.com/info/faq.htm#webster] [http://www.m-w.com/info/webster.htm]
- yo-yo - toy
- zeppelin - dirigible airship
- zip code - postal code (US)
- zipper - zip fastener
Trademarks at risk of becoming generic
Trademarks may become vulnerable to genericide where they are not used as trademarks, where they fall into disuse entirely, or where their corresponding registrations are not enforced effectively or at all. Although such trademarks may tend to become generic due to increasing generic usage, they are not necessarily fully generic.
The determination of whether a trademark is fully generic rather than being merely at risk of genericide tends to be a subjective assessment, and dependent on market sector and many other factors. However, if there is no broad consensus on whether a trademark has become fully generic, then this tends to indicate that the mark has not become generic in the marketplace.
The following list comprises those marks which were originally created and used as trademarks, and which may continue in use as trademarks, and be actively enforced by their trademark owners, but which are generally acknowledged as becoming genericized trademarks due to increasing generic usage. However, until such time as the term is officially abandoned, it remains properly capitalized.
Whether a mark appears in this list is therefore a subjective assessment, as some marks may already have become generic, whereas others may not be accepted as being generic. However, all marks in the list are used generically to some extent.
(It is assumed all of the marks in this list are still valid trademarks and when used in most documents require the use of capital letters and either the TM or (R) mark as appropriate.)
A
- Airfix (UK) - plastic model
- Aqua-Lung - Scuba equipment
- Artex - textured interior wall and ceiling plaster
- AstroTurf - artificial grass produced by AstroTurf, LLC
- Atkins - low-carbohydrate diet
- AutoCue - broadcasting script prompting system
B
- Baggies - food bags
- Bake-off - any kind of contest where a product is created from scratch; although registered as a trademark by Pillsbury, the term is commonly used in computer science programming competitions
- BAND-AID - adhesive bandage; trademarked by Johnson&Johnson. Already the most common term for an adhesive bandage in Australian English (up to a point where 'adhesive bandage' might not even be understood. British English commonly uses 'plaster'.)
- Beer Nuts - sweet and salty glazed nuts, historically peanuts
- Biro (UK) - ball-point pen
- Bondo - any kind of plastic resin auto-body filler material
- Boogie Board - original type of bodyboard
- Breathalyzer - breath alcohol analyzer made by Draeger Safety, Inc.
- Brillo Pad - soap filled, steel wool scouring pad
- Bubble Wrap - air-filled plastic packing material from [http://www.sealedair.com/products/protective/bubble/bubblead.html Sealed Air]
- BVDs - men's underwear
C
- CamelBak - mobile hydration reservoir, canteen
- Chap Stick - lip balm manufactured by AHRobins
- Chyron - television character generators or the graphics those generators create
- Claymation - clay based, stop motion animation; Will Vinton Studios
- Coke (short for Coca-cola) - cola, or carbonated cola-nut-derived soft drink, see soft drink naming conventions, syn. pepsi
- Cool Whip - artificial whipped dessert topping from Kraft Foods
- Crescent Wrench - adjustable, open-end wrench; Crescent Tool and Horseshoe Company
- Cuisinart - food processor and attachments
D
- Dacron - polyester fiber
- Deep Freeze - chest freezer
- Depends - adult disposable diapers made by Kimberly Clark
- Dictaphone - dictation recorder from the eponymous company
- Digibox - a digital television set-top box, origially a Sky satellite set-top box.
- Ditto Machine - one of the original spirit duplicators
- Dixie Cups - disposable bathroom cups, also packaged ice cream cups, which according to [http://www.toiletpaperworld.com/tpw/encyclopedia/navigation/manufacturers.htm Toilet Paper World] is a trademark of the Fort James Corp.
- Dremel - rotary tool; Robert Bosch Tool Corporation
- Drizabone - waterproof overcoat (Australian usage)
- Dry Erase - whiteboard that is written on with colored markers; Sanford Expo
- Duck Tape - strong adhesive tape, originally used on ammunition cases in WWII, then afterwards began being used on ducts at home, hence the confusion with Duck tape vs. duct tape
- Dumpster - large trash can
E
- Erector Set - US metal construction toy, name now owned by Meccano
- Eskimo Pie - chocolate covered ice cream bar
- Esky - cooler box (Australian usage), the brand name Esky was derived from Eskimo
- Ethernet - IEEE 802.3 LAN protocol
F
- FedEx - as a verb meaning to send something by courier, ie I need to FedEx this parcel
- Fiberglas(s) - glass wool or glass fiber reinforced plastic
- Fig Newton - soft, cake-like cookie filled with fig jam; Nabisco
- Freon - fluorocarbon-based refrigerants, propellants, etc.
- Frialator - A deep fryer
- Frigidaire - "fridge", refrigerator
- Friend - spring loaded camming device
- Frisbee - flying disc ('Frisbee' has already completely replaced 'flying disc' in Australian English.)
- Fruit of the Loom - underwear
G
- Gatorade - originally named after the Florida Gators, became trademark when sold to Stokely-Van Camp (currently part of PepsiCo)
- GoKart - mini racing cars
- Green Stamp - trading stamps used in a catalog rewards program; S&H
- Gene chip, a DNA microarray, a trademark of Affymetrix
- Google - debatable since the action the verb implies is rarely applied to other search engines
H
- Hacky Sack - footbag
- Hi-lighter (Hi-Liter) - Highlighting marker pen
- Hoover - vacuum cleaner (in Britain and Commonwealth countries)
- Hula Hoop - dancing ring
I
- iPod - mp3 player
J
- Jacuzzi - whirlpool bath
- Jaws of Life - rescue tool
- JCB - hydraulic digger
- Jeep - very small, angular four-wheel drive truck now manufactured by Daimler Chrysler
- Jell-O - gelatin dessert, or jelly in Britain and Commonwealth countries
- Jet Ski - motorized watercraft
- Jetway - Moveable bridges used at airports
- Jockey Shorts - short, tight-fitting underpants
- JumboTron - large stadium display screens built by Sony
K
- Kevlar - Aramid fiber from DuPont
- Kitty Litter - clumping, clay litter used in cat litterboxes
- Kleenex - packaged, folded facial tissue paper
- Kool-Aid - artificially "fruit" flavored and colored powder that makes a soft drink
- Kraft Dinner or just KD (CAN) - the Canadian name for Kraft Macaroni and Cheese, a prepackeged pasta and cheese sauce produced by Kraft
- Krazy Glue - cyanoacrylate adhesive
L
- Laundromat - self-service laundry
- LearJet - executive aircraft manufactured by Bombardier Industries
- Lego - a toy with interlocking blocks, from the Lego Group's LEGO® Bricks
- Levi's - brand of denim jeans
- LifeSavers - hard candy; Wrigley (US & Australia)
- Liquid Paper - paper correction fluid
- Lycra - a brand of spandex
M
- Mace - aerosol spray tear gas
- Magic Marker - felt-tip marker
- Masonite - fiberboard
- Microchip - integrated circuit
- Milk-Bone - dog treats
- Mills & Boon - Romance Novels (Australian usage)
- Moxie - early 20th century soft drink, now used generically to mean energy, courage, or know-how [http://www.bartleby.com/61/56/M0455600.html]
- Murphy bed - a bed that folds up against the wall
- Muzak - background music
- Mylar - biaxially-oriented polyethylene terephthalate (BOPET) polyester film
- Munchkin - doughnut hole pastry (of Dunkin' Donuts) in the U.S.
N
- Nilla Wafers - vanilla wafer cookies
- Nikko pen - broad, permanent, felt pen (Australian usage)
- Nintendo - home console video games (now less common than PlayStation)
O
- Oreo - cream-filled, chocolate wafer cookie; Nabisco
- Ouija - the name Ouija, used for Ouija boards used in seances, is trademarked
P
- Pablum - baby cereal
- Palm Pilot or simply Palm - handheld computer, generically personal digital assistant
- Parcheesi (replacing the generic word "Pachisi")
- Pepsi - cola, or carbonated cola-nut-derived soft drink, see soft drink naming conventions, syn. coke
- Pergo - laminate flooring material made to look like wood flooring, but made up of either synthetic materials or of synthetic materials combined with natural ingredients and covered with a decorative applique
- Perspex (UK) - Clear plas | | |
