Wing in ground effect vessels are not new, but they may be a better way to move goods.
Episode Summary:
Back in the ‘80s, the Soviet Navy operated a very unusual vehicle called an Ekranoplan. Combining some of the features of both a seagoing vessel and an airplane, it operated out of the water, in ground effect, and essentially defined an entirely new class of vehicle.
The Lun-class Ekranoplan was large, about the size of an Airbus A380, and weighed over 300 tons, but could travel in excess of 340 mph just skimming the surface of the water. Although the design promised long-range, heavy payload and high-speed, curiously little development of this concept occurred in the West. This appears to be changing, however, and the Virginia-based Flying Ship Company has designed an autonomous, electrically powered wing in ground effect drone for light cargo delivery.
Both commercial customers and DARPA have shown interest, and modern materials combined with advanced engineering design tools may make the wing in ground effect vehicle the cargo-carrying solution that combines high-speed with low cost.
Access all episodes of End of the Line on Engineering TV along with all of our other series.
Transcript of this week’s show:
To see any graphs, charts, graphics, images, and/or videos to which the transcript may be referring, watch the above video.
In transportation, bigger is usually better. Whether it’s ships, trains, motor vehicles or airplanes, larger and more powerful machines have always translated into lower seat mile or ton mile costs—something especially important when these different modes of transport all compete with one another.
But physics, as always, is the Supreme Court Justice for engineers, and increasing speed—the other factor that governs transportation—is heavily dependent on the medium through which the machine moves. Rubber-tired road vehicles face the dual difficulties of mechanical friction and aerodynamic drag, things which obey scaling laws that act as real limits to development. Ships have similar hydrodynamic drag and displacement factors, requiring truly enormous horsepower to move at speeds of 30 knots or faster. Airplanes are fast but limited internal volume and lift capability relative to the amount of fuel burned restricts their use for commodity cargoes.
But is there something that combines the best attributes of ships and airplanes? Well, there are a couple of technologies that have been explored over the years, notably air cushion vehicles and wing in ground effect aircraft.
Air cushion vehicles, or hovercraft, use ducted high-pressure air under the vehicle, constrained by rubber skirts. The effect is much like the air cushion that suspends the puck in the familiar tabletop air hockey game, except that the air is supplied by the vehicle itself. Once, very large hovercraft were used for daily high-speed shuttle service across the English Channel, and in the military very large hovercraft are still used for heavy lift, high-speed transportation that can transition from sea to land seamlessly.
But today, cargo-carrying hovercraft have not developed for civilian use. Wing in ground effect aircraft, however, may change this.
The concept is simple: contain and manage the region of higher-pressure air underneath a specially designed, very low-flying aircraft. This reduces the need for large span lifting surfaces and allows engineers to build very large structures that move at aircraft-like speeds, just above the surface of the water.
Without the need to generate enough aerodynamic lift to climb up out of the ground effect, structures can be simpler, bigger and carry heavier payloads.
The Soviet Union developed prototypes that they called Ekranoplans, and they were truly large and fast—but strangely, this spurred very little development in the West. However, technologies are changing and one firm, the aptly named Flying Ship Company, is developing autonomous wing in ground effect vessels that the company claims are 30 to 50 percent more energy efficient than aircraft of similar size, but travel 10 times faster than boats.
The first models will have modest payloads, just over a ton, but with a range of 500 nautical miles using electric powerplants. The company expects their second-generation machine to double both the range and payload capacity figures.
How big could these vehicles get? The Soviet Ekranoplan program produced a 380-ton vehicle the size of an Airbus superjumbo that could travel 340 mph, driven by eight turbofan engines, so truly large machines are possible.
The Flying Ship Company has interest from commercial cargo customers as well as DARPA, and the firm is currently hiring marine, aerospace and systems engineers, so their wing in ground effect autonomous vehicles are well past the proof-of-concept stage. It is technically feasible, and could deliver exactly what the cargo market loves: heavy lift, high-speed and low cost.