Hybrid airship: Difference between revisions
→See also: description of kytoon in simpler terms |
→Design principles: format reference, expand reference, copyedit - remove long quote and add Burgess' own summary in reference (the reader can draw own conclusions about dated technology) |
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On the other hand heavier-than-air aircraft require the constant use of power to generate lift, and airplanes also require [[runway]]s, while helicopters need even more power to hover. |
On the other hand heavier-than-air aircraft require the constant use of power to generate lift, and airplanes also require [[runway]]s, while helicopters need even more power to hover. |
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The hybrid airship combines lift from a lighter-than-air gas such as helium with lift from aerodynamic forces. Such a craft is still heavier than air, which makes it similar in some ways to a regular aircraft. The dynamic lift may be provided by vertical thrusters such as helicopter-like rotors, or a lift-producing shape (like a wing) combined with horizontal thrust, or a combination of the two.<ref>[http://www.military-heat.com/91/p791-hybrid-airship-project/ P-791 hybrid airship project |
The hybrid airship combines lift from a lighter-than-air gas such as helium with lift from aerodynamic forces. Such a craft is still heavier than air, which makes it similar in some ways to a regular aircraft. The dynamic lift may be provided by vertical thrusters such as helicopter-like rotors, or a lift-producing shape (like a wing) combined with horizontal thrust, or a combination of the two.<ref>[http://www.military-heat.com/91/p791-hybrid-airship-project/ |title= P-791 hybrid airship project |last=Tolip |date=18 February 2008 |publisher=military-heat.com}}</ref> The aerodynamic approach is similar to that of a conventional [[lifting body]] aircraft, although airspeeds are much lower. |
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Hybrid airships are intended to fill the middle ground between the low operating cost and low speeds of traditional airships and higher speed, but more fuel-hungry heavier-than-air aircraft. In addition, by combining dynamic and buoyant lift, hybrids are expected to provide improved air-cargo payload capacity and hovering capability compared to a pure airship, while having longer endurance than a pure HTA type. Such a design is intended to approach the "best of both worlds" combination: the higher speed of aerodynamic craft and the lifting capacity of aerostatic aircraft. |
Hybrid airships are intended to fill the middle ground between the low operating cost and low speeds of traditional airships and higher speed, but more fuel-hungry heavier-than-air aircraft. In addition, by combining dynamic and buoyant lift, hybrids are expected to provide improved air-cargo payload capacity and hovering capability compared to a pure airship, while having longer endurance than a pure HTA type. Such a design is intended to approach the "best of both worlds" combination: the higher speed of aerodynamic craft and the lifting capacity of aerostatic aircraft. |
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===Engineering considerations=== |
===Engineering considerations=== |
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While some early airships, notably Santos-Dumont's No. 10, built in 1903, were fitted with wing planes with the intention of providing additional dynamic lift, |
While some early airships, notably Santos-Dumont's No. 10, built in 1903, were fitted with wing planes with the intention of providing additional dynamic lift, the added lift of planes is offset by increased weight and drag.<ref name="burgess">{{cite |last=Burgess |first=Charles P |title=Airship Design |date=1927|chapter=Chapter XI: Common Airship Fallacies|url=http://www.xlta.org/library/burgess.pdf |format=pdf |series=Ronald Aeronautic Library |publisher=Ronald Press |pages=289-290 |quote=it may be said that the increased weight of structure, engines and fuel would considerably exceed the lift derived from the planes; and there would still remain the apparently insurmountable problems of starting and landing the combination craft}}</ref> |
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According to Burgess - writing in 1927 - "For every 1,000 lb lift carried by the planes, approximately 60 lb resistance must be overcome by the thrust of the propellers. On the other hand, a {{convert|5000000|ft3|m3|abbr=on}} airship flying at {{convert|60|mph|kph|abbr=on}} experiences only about 20 lb resistance per 1,000 lb lift, and the relative resistance decreases with increasing size and diminishing speed. It is apparent, therefore, that the increase in lift obtained by the use of planes on an airship would require a disproportionate increase in engine power and fuel consumption."<ref name="burgess" /> |
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Conventional airships often make use of aerodynamic lift by using their [[elevator (aircraft)|elevator]]s to fly in a nose up attitude; however, this is done to counteract minor out-of-trim conditions. Current hybrid designs, such as the Hybrid Air vehicles [[HAV-3]], use a flattened or multi-lobe hulls to create substantial quantities of aerodynamic lift. Attainable dynamic-lift-to-drag ratios are significantly below those of efficient wings, because [[Lift-induced drag|induced drag]] increases with decreasing aspect ratio.<ref>Crichner and Nicolai; "Hybrids - The Airship Messiah?" Lockheed.</ref> As a result, the lift is produced at a lower efficiency than proposals using wings, and thus even more aerodynamically inefficient compared to fully buoyant airships. |
Conventional airships often make use of aerodynamic lift by using their [[elevator (aircraft)|elevator]]s to fly in a nose up attitude; however, this is done to counteract minor out-of-trim conditions. Current hybrid designs, such as the Hybrid Air vehicles [[HAV-3]], use a flattened or multi-lobe hulls to create substantial quantities of aerodynamic lift. Attainable dynamic-lift-to-drag ratios are significantly below those of efficient wings, because [[Lift-induced drag|induced drag]] increases with decreasing aspect ratio.<ref>Crichner and Nicolai; "Hybrids - The Airship Messiah?" Lockheed.</ref> As a result, the lift is produced at a lower efficiency than proposals using wings, and thus even more aerodynamically inefficient compared to fully buoyant airships. |
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Revision as of 11:25, 23 March 2014
A hybrid airship is an aircraft that combines characteristics of lighter-than-air (LTA), aerostat technology with heavier-than-air (HTA) technology, either fixed-wing or rotary-wing. Examples include helicopter/airship hybrids intended for heavy lift applications and dynamic lift airships intended for long-range cruising. No production vehicles have been built, but several manned and unmanned prototypes have flown and successfully demonstrated the concept.
The term "hybrid airship" has also been used to describe an airship combining elements of different types of airships.
Design principles
Characteristics
Conventional airships have low operating costs, but are limited in several ways, including low payload/volume ratios and low speeds. Additionally, ground handling of an airship can be difficult. Because it is floating, in even a light breeze it is susceptible to wind buffeting.
On the other hand heavier-than-air aircraft require the constant use of power to generate lift, and airplanes also require runways, while helicopters need even more power to hover.
The hybrid airship combines lift from a lighter-than-air gas such as helium with lift from aerodynamic forces. Such a craft is still heavier than air, which makes it similar in some ways to a regular aircraft. The dynamic lift may be provided by vertical thrusters such as helicopter-like rotors, or a lift-producing shape (like a wing) combined with horizontal thrust, or a combination of the two.[1] The aerodynamic approach is similar to that of a conventional lifting body aircraft, although airspeeds are much lower.
Hybrid airships are intended to fill the middle ground between the low operating cost and low speeds of traditional airships and higher speed, but more fuel-hungry heavier-than-air aircraft. In addition, by combining dynamic and buoyant lift, hybrids are expected to provide improved air-cargo payload capacity and hovering capability compared to a pure airship, while having longer endurance than a pure HTA type. Such a design is intended to approach the "best of both worlds" combination: the higher speed of aerodynamic craft and the lifting capacity of aerostatic aircraft.
Hybrid aircraft technology is claimed to have a wide range of flight-performance behaviors ranging from heavier than air to near buoyant characterizations. This perception of uncommon dynamic flight range when coupled with an air cushion landing system has reinvigorated the LTA community and those seeking ultra heavy and affordable airlift transportation options.[citation needed]
Engineering considerations
While some early airships, notably Santos-Dumont's No. 10, built in 1903, were fitted with wing planes with the intention of providing additional dynamic lift, the added lift of planes is offset by increased weight and drag.[2]
Conventional airships often make use of aerodynamic lift by using their elevators to fly in a nose up attitude; however, this is done to counteract minor out-of-trim conditions. Current hybrid designs, such as the Hybrid Air vehicles HAV-3, use a flattened or multi-lobe hulls to create substantial quantities of aerodynamic lift. Attainable dynamic-lift-to-drag ratios are significantly below those of efficient wings, because induced drag increases with decreasing aspect ratio.[3] As a result, the lift is produced at a lower efficiency than proposals using wings, and thus even more aerodynamically inefficient compared to fully buoyant airships.
Controversy
Proponents of hybrid airship technology claim significant advances that will make them useful for modern transportation applications.[4][5]
Hybrid airship efforts, like airship efforts in general, have been called into question from both economic and technology viability perspectives.[6][7][5] The hybrid approach had been described as the "worst of both worlds",[citation needed]
History
Historical antecedants
Solomon Andrews built two airships in the period during and shortly after the American Civil War. The first of these, Aereon, used three individual cigar shaped balloons rigged together in a flat plane; the second, Aereon #2, employed a single "lemon-shaped" balloon.[8] Andrews' Aereons were propelled by angling the balloons upward and dropping ballast, whereupon the balloons were used as a low aspect ratio wing to glide forward; the process was then reversed, the balloons being angled downward and large quantities of lifting gas being vented to glide forward on descent.[9]
In 1905 Alberto Santos-Dumont conducted various experiments with his first airplane, the Santos-Dumont 14-bis, prior to attempting to fly it for the first time. These included hanging it from a steel cable and towing it, and subsequently hanging it beneath the envelope of a previously built airship (Santos-Dumont_Number_14|Number_14) - akin to learning to swim with "water wings". The combined craft was unusable, and was broken up, being referred to as "a monstrous hybrid".[10] After these "rehearsals" were completed, Santos-Dumont made the first public demonstration of a heavier-than-air aircraft in the Europe.
In 1907 the British airship British Army Dirigible No 1 (named Nulli Secundus) first flew. It used aerodynamic surfaces for attitude control in flight, and for its first flight was also fitted with large wings amidships. The wings were intended to aid stability but were removed for all subsequent flights.[11][12]
Hybrid airship history
The Aereon 26 was an aircraft which made its first flight in 1971. It was a small-scale prototype of the hybrid Airship Aereon Dynairship and part of the "TIGER" project. But it was never built due to lack of market for a hybrid airship.[13]
The 1986 Piasecki PA-97 Helistat experimental design combined four helicopters with a blimp in an attempt to create a heavy-lift vehicle for forestry work. It broke up at the end of its first flight possibly due to inadequate structural strength
The SkyCat or "Sky Catamaran" vehicular technology is a hybrid aircraft amalgamation; a scale version at 12 meters called "SkyKitten", built by the Advanced Technologies Group Ltd, flew in 2000. The U.S. Defense Advanced Research Projects Agency (DARPA) initiated the Walrus Hybrid Ultra Large Aircraft program in 2005, a technology development initiative focused on ultra heavy air lift technology explorations. The program was terminated in 2007.
In 2006, the Lockheed Martin P-791 underwent manned flight tests. It was an unsuccessful candidate for the military Long Endurance Multi-intelligence Vehicle program
In 2008, Boeing announced that it was teaming up with SkyHook to develop a heavy duty lifting vehicle, the SkyHook JHL-40 Boeing subsequently shelved the project.[14]
Northrop Grumman was awarded a US$517 million contract to develop a hybrid airship and present it for military assessment in just 18 months as part of the Long Endurance Multi-intelligence Vehicle (LEMV) program. The design was based on Hybrid Air Vehicles' design. On 14 February 2013, the Army confirmed that it had cancelled the LEMV development effort, citing technical and performance challenges, as well as the limitations imposed by constrained resources.
No hybrid aircraft design has yet been developed past the initial experimental stages.
Current efforts
Hybrid Air Vehicles purchased the LEMV vehicle from the US Department of Defense for $301,000, and is currently re-erecting the vehicle - now known as "Airlander" - in one of the historic airship sheds at Cardington, with plans to further develop the vehicle and make a passenger flight in 2016. One investor, Bruce Dickinson, has announced plans to "drum up publicity" by flying twice around the world nonstop.[15]
An Australian-based company is working on a project to develop an air crane called the SkyLifter, a "vertical pick-up and delivery aircraft" being capable of lifting up to 150 tons.[16]
A Canadian start-up, Solar Ship Inc, is developing solar powered hybrid airships that can run on solar power alone. The idea is to create a viable platform that can travel anywhere in the world delivering cold medical supplies and other necessitates to locations in Africa and Northern Canada without needing any kind of fuel or infrastructure. The hope is that technology developments in solar cells and the large surface area provided by the hybrid airship are enough to make a practical solar powered aircraft. Some key features of the Solarship are that it can fly on aerodynamic lift alone without any lifting gas, and the solar cells along with the large volume of the envelope allow the hybrid airship to be reconfigured into a mobile shelter that can recharge batteries and other equipment.[17]
List of hybrid airships
- Aeroscraft
- Hybrid Air Vehicles HAV-3
- Lockheed Martin P-791
- Nimbus EosXi
- Piasecki PA-97
- Skycat
- SkyHook JHL-40
- Thermoplan
- Walrus HULA
See also
- Kytoon - a tethered kite/balloon hybrid
References
- ^ [http://www.military-heat.com/91/p791-hybrid-airship-project/ |title= P-791 hybrid airship project |last=Tolip |date=18 February 2008 |publisher=military-heat.com}}
- ^ Burgess, Charles P (1927), "Chapter XI: Common Airship Fallacies", Airship Design (pdf), Ronald Aeronautic Library, Ronald Press, pp. 289–290,
it may be said that the increased weight of structure, engines and fuel would considerably exceed the lift derived from the planes; and there would still remain the apparently insurmountable problems of starting and landing the combination craft
- ^ Crichner and Nicolai; "Hybrids - The Airship Messiah?" Lockheed.
- ^ Zolfagharifard, Ellie (28 February 2014 (updated 1 March 2014)), "The flying bum! 300ft-long 'airship' unveiled in Britain is the world's longest aircraft", mailonline, Associated Newspapers
{{citation}}: Check date values in:|date=(help) - ^ a b Hpanchal (30 June 2011), "High flying demand or bust?", Air Cargo World
- ^ Farnham, Alan (29 April 2002), All hangar, no blimp
- ^ Dick, Joseph (27 May 2011), "Helium Hokum: Why Airships Will Never Be Part of Our Transportation Infrastructure", Guest Blog, Scientific American
- ^ Solomon Andrews, The Art of Flying, 1865
- ^ Lee Payne, Lighter than Air, p. 39
- ^ Nancy Winters, Man Flies - The Story of Alberto Santos-Dumont, p. 100
- ^ Reese, P.; The Flying Cowboy: Samuel Cody Britain's First Airman, History Press, Reprint 2008, 978-0752436593 page 87.
- ^ Walker, P.; "Early Aviation at Farnborough Volume I: balloons, Kites and Airships", Macdonald (1971), page 198.
- ^ Aereon26
- ^ http://www.airship-association.org/cms/node/9
- ^ Grover, Sami (20 March 2014), "Lead singer for Iron Maiden to pilot hybrid airship around the world", Mother Nature Network
- ^ Daily Mail Reporter (7 October 2010), "The giant airships which can carry entire buildings hundreds of miles", mailonline, Associated Newspapers Ltd
- ^ Hamilton, Tyler (14 October 2011), "Hamilton: Toronto start-up designs solar-powered hybrid aircraft", thestar.com
External links
- Havill, C. Dewey (1974), NASA TM X-62,374 Some factors affecting the use of lighter than air systems (PDF), Ames Research Center, NASA