Combination of hovercraft and ground effect technology for freight transport

Both hovercraft and ground effect technology can be developed to support the weight of several of the largest cargo aircraft. Combining the technologies in a single vehicle allows for more efficient travel at higher speeds over longer distances with the ability to go ashore to load and unload the vehicle.

introduction

Hovercraft technology and ground effect technology developed independently over decades, with each technology suited to its own niche in the transportation market and military applications. In the UK, hovercraft vehicles were used for relatively short-distance transport over water, with the ability to disembark on a beach to load and unload passengers and cargo. In comparison, ground effect technology involved boat hulls that allowed any vehicle to remain on a water surface when at a terminal, in use, or when moored at a terminal out of service.

Both hovercraft and ground effect vehicles use aeronautical propellers for propulsion and aeronautical rudders to change direction. This commonality invites research into methods of combining the two technologies in a single vehicle that can both travel efficiently at high speed over water and transition from water to land to load and unload cargo at coastal terminals. The developers of both technologies have explored the potential development of each technology at scale, which could theoretically handle a payload of several thousand tons and the equivalent of several of the largest cargo aircraft.

“Airplanes” on a mega scale

Boeing designed the theoretical “airplane,” named “Pelican,” with a 500-foot wingspan, a wind chord of nearly 100 feet, and a 1.5 million pound payload at a maximum takeoff weight of 5,000,000 pounds. It was designed to conserve fuel by flying in “ground effect” mode at 20 to 100 feet above the ocean, and climb to 10,000 feet on approach to land at a commercial airport. “Pelican's” fuselage was to be over 400 feet long, with each square foot of its wings supporting about 125 pounds of weight.

The Antonov AN-225 is the largest commercial cargo aircraft ever built, with a takeoff weight of just over 600,000 kg. Before the conflict in Ukraine, the AN 225 was used to transport special cargo. However, companies specializing in air cargo showed little interest in the six-engine AN-225, opting instead for the four-engine Boeing 747 and large twin-engine Boeing and Airbus aircraft converted for cargo transport. Ongoing development of turbine engines and aeronautical reduction gears offers the prospect of huge turbofan and turboprop engines, each with over 113,000 kg of thrust.

Combination of two technologies

A mega-scale hovercraft with a 50-by-500-foot impulse curtain and 3 PSI air injection would produce 5,400 tons of lift. An extension of the ground-effect tandem wing concept from Germany would give two columns of multiple wings in a row, with successive air intakes at progressively higher altitudes. This would give a 5,000-ton capacity for a hovercraft with ground-effect wings.

In operation, the vehicle would operate between coastal land and surface locations, transporting such priority cargoes in containers. Upon takeoff, it would use its onboard air turbo-compressors during hovercraft acceleration before transitioning to ground effect flight to efficiently fly at high speeds. A total chord length of 500 feet across multiple rows of overlapping and closely spaced wings should allow a maximum cruise altitude of 25% of the wing chord, or 100 to 125 feet above water, with the most economical cruise achieved at a cruise altitude of 15 to 25 feet above water.

Basic operation

A heavy vehicle combining hovercraft capabilities with ground effect wings would travel between land-based coastal terminals, traveling efficiently at increased speed over a water surface. Hovercraft air pumps would operate at low vehicle speeds during departure from and during approach to a terminal. At higher speeds, when ground effect wings carry the vehicle, hovercraft air pumps would be shut off. To conserve fuel, acceleration would occur on a solid land surface to achieve a high enough speed that ground effect wings could carry the vehicle during transition to travel over water.

Fuel consumption accounts for up to 80% of the operating costs of a cargo aircraft flying at over 500 miles per hour. Ground effect flights at speeds of 150 to 200 miles per hour would use far less fuel than high altitude flights, even for a vehicle that is 4 to 5 times the total weight of a large cargo aircraft. The market segment for a giant ground effect cargo aircraft would offer a much faster delivery time of 3 to 4 days than ships, which take 3 to 4 weeks, at a fraction of the transportation cost of air freight.

Research focus

The development of a combined hovercraft and tandem wing ground effect technology will depend on innovative problem-solving thinking from people with research experience in both technologies. Tandem-Wing of Germany has built ground effect vehicles that travel over a water surface, combining a large front wing with a large rear wing mounted behind it. Future research would need to focus on developing a series of wings mounted one behind the other, with air intakes placed at progressively higher altitudes and designed to provide ground effect dynamics over the entire wing chord length.

Individuals with research expertise in hovercraft technology would need to focus on the maximum possible width and length of the hull that an air cushion can support as the vehicle makes the transition between liquid and solid surfaces. A large-scale hovercraft might need to use multiple impulse curtains beneath the hull, possibly with multiple skirts, to minimize air loss at low vehicle speeds while ensuring the vehicle hovers. Researchers will need to establish a transition speed at which the vehicles transition between hovercraft mode and ground effect wing operation to ensure energy efficient operation when transporting cargo over longer distances.

Stormy sea

Extreme wave conditions found in the shallow waters of the North Sea and northern Bering Sea require ground effect vehicles to fly at a constant height of at least 100 feet above the water. Experience from Australia with a small ground effect vehicle has shown that it can easily fly at high speed at a height of 4 feet above 13-foot waves. Airline pilots have pointed out that gusty winds at airports cause stability problems in commercial aircraft during landing, when ground effect dynamics have the greatest impact on aircraft stability. However, aircraft wings are very different from ground effect wings.

The wings of commercial aircraft are built with a long span that far exceeds the comparatively short wing chord. Ground effect wings can be built with a front-to-back span that far exceeds the wingspan, allowing craft with long wing chords to maintain smooth “flight” at increased speed over choppy water. Further research with small craft could determine the wingspan, chord, and cruise speed of ground effect aircraft that can maintain smooth “flight” over heavy seas such as those in the Bering Sea, as well as over waves up to 80 feet high, which occur in both the Bering Sea and the North Sea.

World market

The commercial aviation industry uses cargo aircraft on long-haul international flights that cross oceans. A large combination hovercraft and ground effect vehicle could serve several direct transoceanic routes between major coastal cities located on opposite sides of the same ocean. These vehicles would be slower than airplanes but much faster than container ships. There is likely a market for a fuel-efficient vehicle that can carry four to five times as much cargo as a cargo aircraft, with lower transportation costs and competitive delivery schedules. Such a vehicle could even operate over the Arctic.

A trans-Arctic route could connect American terminals on the west coast near Los Angeles and San Francisco, or Asian terminals near Tokyo, Busan or Shanghai with European terminals near Edinburgh, Rotterdam or Hamburg, and possibly go over the Russian side of the Arctic. There is also the possibility of connecting some Asian terminals to terminals on the American east coast via the Canadian side of the Arctic. It would be possible for a large ground effect aircraft to fly directly over the North Pole between the Bering Sea and the Norwegian Sea.

Household service

There would likely be a market for the services of smaller combinations of hovercraft and ground effect vehicles in countries such as Russia and Canada, where such vehicles could navigate wide rivers and (frozen) lakes. In summer, vessels can serve several coastal communities around Hudson Bay in Canada, where winter ice conditions prevent shipping. There is the possibility of hovercraft with ground effect wings traveling across the ice surface of Hudson Bay and stopping at ice surface terminals in coastal communities to deliver essential goods such as food.

During the northern winter, hovercraft with ground-effect wings could provide high-speed winter ferry service across the ice-covered Great Lakes of North America. There would also likely be opportunities for service across Lake Michigan between Milwaukee and Muskegon, and across western Lake Ontario between Toronto and the Niagara/St. Catharines region.

Hovercraft with ground-effect wings could travel at high speeds over frozen rivers in northern Canada, such as the Mackenzie, or over frozen rivers in northern Russia. They could also cross frozen tundra land between large bodies of water in northern Canada and northern Russia that have become a sheet of ice in winter.

Conclusions

The combination of earlier research by hovercraft and ground effect vehicle developers and later developments suggests that a combined hovercraft with ground effect wings could potentially carry a total weight of 5,000 tonnes.

A vehicle of this capacity could fill a market niche by transporting medium-priority cargo on international routes faster than ships and at lower transportation rates than air freight. There is potential to build smaller hovercraft with ground-effect wings to provide cargo transportation services in Canada's Arctic region during the winter after regulatory issues are resolved.