Combining Hovercraft and Ground Effect Technology for Freight Transport
Both hovercraft and ground effect technology can be developed to carry weight of several of the largest cargo airplanes. Combining the technologies into a single vehicle allows for more efficient travel at higher speed over extended distances with the ability to come ashore on to land to load and unload the vehicle.
Introduction
Hovercraft technology and wing-in-ground effect technology developed independently of each other over a period of decades, with each technology suited to its own unique niche in the transportation market and for military applications. In the UK, hovercraft vehicles were assigned to comparatively short-distance transportation across water, with the ability to come ashore on to a beach to load and discharge both passengers and freight. By comparison, wing-in-ground effect technology included boat hulls that allowed each vehicle to remain on a water surface when at a terminal, when in service or when moored out-of-service at a terminal.
Both hovercraft and ground effect vehicles use aeronautical propellers for propulsion and aeronautical rudders to change direction. That commonality invites exploration of methods by which to combine the 2-technologies into a single vehicle that can both travel efficiently at high speed across water while also being able to transfer from water to land to load and unload freight at coastal terminals. Developers of both technologies have explored possible mega-scale development of each technology that would theoretically have been capable of a laden weight of several thousand tons and equivalent to several of the largest cargo planes.
Mega-Scale ‘Aircraft’
Boeing designed the theoretical ‘airplane’ dubbed “Pelican” with a wingspan of 500 feet, a wind chord of almost 100 feet, and intended to carry a payload of 1.5 million pounds with a maximum take-off weight of 5,000,000 pounds. It was intended to save fuel by traveling in ‘ground effect’ mode at 20 feet to 100 feet above ocean, climbing to 10,000 feet elevation when approaching land so as to touch down at a commercial airport. The fuselage of ‘Pelican’ was intended to exceed 400 feet in length, with each square foot of its wing carrying around 125 pounds of weight.
The Antonov AN-225 represents largest commercial cargo airplane built, with a take-off weight just over 1,300,000 pounds. Prior to the conflict in Ukraine, the AN 225 was used to carry unique types of freight. However, companies that specialize in carrying air freight showed little interest in the 6-engine AN-225, opting instead for the 4-engine Boeing 747 airplane and large 2-engine airplanes built by Boeing and by Airbus adapted to carry freight. Ongoing development in a turbine engine and aeronautical reduction gear technology offers the future prospect of mega-size turbofan and turboprop engines delivering over 250,000 lb of thrust each.
Combining Two Technologies
A mega-scale hovercraft with a momentum curtain measuring 50-feet by 500-feet and air pumped in at three PSI would produce a ‘lift’ of 5,400 tons. Expanding on the ground-effect tandem wing concept from Germany would result in two columns of multiple wings in a row, with successive air intakes at progressively higher elevation. This would yield a capacity of 5,000 tons for a hovercraft with ground effect wings.
In service, the vehicle would operate between land-based coastal locations and travel across water carry such priority freight inside containers. Upon departure, it would use onboard air turbo-compressors during acceleration as a hovercraft before making the transition to ground effect flight so as to travel efficiently at high speed. A total chord length of 500 feet across multiple rows of overlapping and closely spaced wings should allow for a maximum travel height of 25% of the wing chord or 100 to 125 feet above water, with peak economical cruising occurring at a flight elevation of 15 feet to 25 feet above water.
Basic Operation
A heavy vehicle that combines hovercraft capability with ground-effect wings would operate between land-based coastal terminals and travel efficiently at elevated speed above a water surface. Hovercraft air pumps would function at low vehicle speed during departure from and during approach to a terminal. At higher speed when ground-effect wings carry the vehicle, hovercraft air pumps would be shut off. To save fuel, acceleration would occur on a solid land surface to reach a sufficiently high speed for ground-effect wings to carry the vehicle as it transitions to travel above water.
Fuel consumption accounts for up to 80% of the operating cost of a cargo plane that travels at over 500-miles per hour. Ground effect flight at speeds of 150 to 200-miles per hour would consume far less fuel than high-elevation flight, including for a vehicle that incurs 4 to 5-times the laden weight of a large cargo plane. The market segment for a mega-size ground-effect freight plane would be to offer much faster delivery time within 3 to 4-days compared to ships that require 3 to 4-weeks, at a fraction of the transportation cost of air freight.
Research Focus
The development of combination hovercraft – tandem wing ground effect technology will depend on innovative problem-solving thinking from people who have research experience with both technologies. Tandem-Wing of Germany has built ground effect vehicles that travel above a water surface while combining a large forward wing with a large trailing wing installed behind it. Future research would need to focus on developing a series of wings installed one behind the other, with successive air intakes arranged at progressively higher elevation and designed in a way to assure ground effect dynamics along the entire chord length of the wing assembly.
People with research expertise in hovercraft technology would need to focus on the maximum possible width and length of fuselage that a cushion of air could carry as the vehicles makes the transition between liquid and solid surface. A large-scale hovercraft might need to use multiple momentum curtains under the fuselage, perhaps with multiple skirts to minimize loss of air at low vehicle speed while assuring vehicle levitation. Researchers will need to establish a transition speed where the vehicles transfer between hovercraft mode and ground effect wing operation to ensure energy-efficient operation while carrying freight over extended distances.
Rough Seas
Extreme wave conditions that occur in the shallow waters of the North Sea and northern region of the Bering Sea require that ground-effect craft travel at a sustained elevation of at least 100 feet above water. Experience from Australia involving a small ground-effect craft revealed that it could travel smoothly at speed at an elevation of 4 feet above waves of 13 feet. Airline pilots advised that gusting winds at airports caused stability issues with commercial aircraft during touch down, when the ground-effect dynamics had its greatest effect on aircraft stability. However, airplanes wings are very different to ground-effect wings.
Commercial aircraft wings are built with large wingspan greatly exceeding the comparatively short chord measurement. Ground effect wings can be built with front to rear chord measurement greatly exceeding wingspan, allowing vehicles built with long-chord wings to sustain smooth ‘flight’ when traveling at elevated speed above choppy water. Further research involving small scale vehicles could establish the wingspan, wing chord and travel speed of ground effect craft that maintain smooth ‘flight’ above severe sea swells as occur in the Bering Sea, as well as waves of up to 80-feet height that occur in both the Bering and North Seas.
International Market
The commercial airline industry operates cargo planes on long-haul international flights that cross oceans. A large-scale combination hovercraft – ground effect vehicle could operate several direct trans-ocean routes between major coastal cities located on opposite sides of the same ocean. While slower than airplanes, these vehicles would be much faster than container ships. There is likely a market for a fuel-efficient vehicle that carries 4 to 5 times the payload of freight of a cargo plane at lower transportation costs and competitive delivery schedules. Such a vehicle might even operate via the Arctic.
One trans-Arctic route could connect west coast American terminals located near Los Angeles and San Francisco or Asian terminals located near Tokyo, Busan or Shanghai to European terminals located near Edinburgh, Rotterdam or Hamburg, potentially traveling via the Russian side of the Arctic. There might also be potential to locate some Asian terminals to terminals located along the American east coast, via the Canadian side of Arctic. It might be possible for a large ground effect plane to travel directly across the North Pole between the Bering Sea and Norwegian Sea.
Domestic Service
There would likely be a market for the services of smaller-scale combination hovercraft–ground effect vehicles within countries such as Russia and Canada, where such vehicles could travel along wide rivers and across (frozen) lakes. During summer, ships can serve several coastal communities located around Hudson Bay, Canada where winter ice conditions prevent ship navigation. There is potential for hovercraft vehicles built with ground-effect wings to travel above the ice surface of Hudson Bay and stop on ice surface terminals at coastal communities to deliver essential supplies such as food.
During the northern winter, hovercraft built with ground-effect wings could provide winter time fast ferry service across North America’s ice-covered Great Lakes. There would likely be potential for service across Lake Michigan between Milwaukee and Muskegon, also across western Lake Ontario between Toronto and Niagara/St. Catharines region.
Hovercraft with ground-effect wings would be able to travel at speed above ice covered rivers in northern Canada such as the Mackenzie, ice covered rivers in northern Russia as well as across frozen level tundra land between large bodies of water turned to winter ice cover, in northern Canada and northern Russia.
Conclusions
The combination of earlier research by developers of hovercraft and ground effect vehicles, along with later developments, suggests the possibility of a combination hovercraft built with ground effect wings being able to incur a total laden weight of 5,000 tons.
A vehicle of such capacity could occupy a market niche carrying medium-priority freight at a faster delivery time along international routes than ships and lower transportation tariffs than air freight. There would be potential for smaller-size hovercraft built with ground effect wings to provide wintertime freight transportation service in Canada’s Arctic region after regulatory issues are resolved.
The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.
No comments:
Post a Comment