Exotic Hulls Part 6 - Ekranoplans

To complete our ongoing series on exotic hulls, it is now time to turn our attention to a type of vessel that not only straddles the boundary between the ship and the airplane, but arguably crosses it to be even more airplane than ship. Variously known as the Ground Effect Vehicle, Wing-in-Ground Effect or Ekranoplan,¹ these look mostly like aircraft, but take advantage of a quirk of aerodynamics known as "ground effect" to greatly reduce drag, so long as they are operating near the surface.

It's probably worth starting by explaining what ground effect is and how it works. Basically, in the process of producing lift, an airplane's wing also produces a vortex that makes drag.² But if the wing is close to the ground (or water), then the surface will disrupt the vortex, slashing drag dramatically, in a manner determined by the ratio of wingspan to height above the ground. For instance, a wing that is 10% of the wingspan above the ground will only experience about 20% of the induced drag it would at altitude, rising to around 50% at 20% wingspan. This makes taking off in an airplane easier, and landing a bit harder, and in theory could be used to significantly improve the performance of an airplane.

The biggest problem, of course, is how low you have to fly. Take the last plane you flew on, which statistically was either a Boeing 737 or an Airbus A320.³ These are both fairly large planes, and each has a wingspan of about 120', which implies that to take full advantage of ground effect, they'd need their wings to be about 12' off the ground. Coincidentally, this is just about how far off the ground the wingtips of both airplanes are when they're sitting on the ground. Obviously, a purpose-built ekranoplan would be designed with engines above the wing, but even then, a vehicle which is designed to operate at high speed and is thwarted by a single-story building isn't really practical for operations over land, unless you happen to have somewhere very flat and devoid of all natural and man-made obstacles, like an ice field or Florida after a really big hurricane.

The Caspian Sea

As a result of all this, in practice the ekranoplan is limited to operations over water, and almost all are designed to use that same water as a runway, most being fairly typical flying boat hulls which use planing to get up to flying speed. But even water is not always smooth, which can pose a serious problem for the operation of an ekranoplan in many areas. In the North Atlantic⁴ average wave height will exceeding cruising height for even a big ekranoplan at least 20% of the time, to say nothing of cases where the biggest outlier wave might be enough to bring one down. Even if all of that is dealt with, flying an ekranoplan over moderate waves will result in frequent changes in aerodynamic properties, making for an exceedingly rough ride. To date, pretty much all Ekranoplan testing has been done in the Caspian Sea, the world's largest lake⁵ and a place where the typical wave height doesn't get much above 1.2 m.

Ekranoplan designer Rotislav Alexeyev

Legally and practically, ekranoplans are divided into three types. First, vehicles that are completely incapable of operating out of ground effect. These are steered like ships, with nautical qualifications being all that is required of the helmsman, as there isn't even an elevator to use. Second, vehicles capable of operating outside of pure ground effect, if only for short periods, with the maximum altitude being the 500' that is generally considered minimum safe altitude for airplanes. Third, some ekranoplans are capable of true flight at higher altitude, being distinguished from flying boats primarily in being designed to operate while in ground effect as well as at altitude.

A sketch of the Caspian Sea Monster

The development of the ekranoplan as more than a theoretical curiosity is largely due to the efforts of one man, Rotislav Alexeyev, the leader of the Soviet Central Hydrofoil Design Bureau. Alexeyev had the expertise in both naval architecture and aeronautics to manage the ekranoplan project, and even served as a pilot during the test program, as well as the political acumen to get backing for it from both Nikita Khrushchev and Defense minister Dmitry Ustinov. After a number of test vehicles in the early 60s, authorization was given in 1963 for a large-scale prototype, known as KM, although it is better known by the moniker given to it by Western intelligence services, the Caspian Sea Monster. This was a result of the massive size of the vehicle, 92 m long and weighing 544 tons, the largest and heaviest airplane built to that point.⁶ In cruising flight, at a height of between 4 and 14 m, it was propelled by a pair of engines mounted in the tail, but takeoff required eight extra engines mounted in a row above the nose, with their exhausts directed downward to form an air cushion under the wing, easing the task of getting off the water. It's not clear what purpose an operational version of the KM would have served, and the prototype was destroyed by a crash in 1980.

An Orlyonok in the Russian Navy Museum

A few years later, an operational ekranoplan was ordered, the Orlyonok. This was intended as a high-speed transport for the Soviet Navy, capable of carrying Soviet Naval Infantry and unloading them over a beach with their vehicles, the entire nose swinging 92° to load and unload things up to the size of a BTR. The cruise engine was a single turbofan in the tail, while two turbofans in the nose were used to get it airborne, with their exhaust being directed under the wing to help form an air cushion for takeoff, a process aided by the massive flaps, which helped seal the area under the wings and trap the engine exhaust more efficiently. Takeoff was also aided by the deployment of retractable hydroskis, which also had wheels to allow the Orkyonok to be moved around ashore. Three of this type were completed, and while they appeared to be reasonably successful, although the cruising altitude of 2 m (6') would have been rather scary. A few flights were made out of ground effect, reaching past 100 m, but the aircraft was unstable and required an exceptional pilot to control at such altitudes. In theory, it could carry 30 tons of cargo 1000 km or more, but in practice, they were unable to find a good home in the bureaucratic mess of the Soviet armed forces, because nobody was sure if they were ships or airplanes. Ultimately, after a major crash in 1992, the surviving ekranoplans were retired, and plans for derivatives intended for tasks ranging from civilian ferry duty to ASW to prospecting in arctic waters. A particularly insane plan was to combine the Orlyonok with the An-225 for search and rescue, with the massive Antonov carrying the ekranoplan to the scene of a disaster, then releasing it in the air to descend and provide aid to up to 70 survivors.

A model of the Lun class

But Orlyonok wasn't the only attempt by the Soviets to make an operational ekranoplan. A second, larger type of the same broad configuration was ordered, the Loon,⁷ designed as a missile platform. It carried six P-270 Moskit ramjet-powered anti-ship missiles, mounted in pairs on the back of the ekranoplan. Concerns about ingesting rocket exhaust during a missile launch meant that all eight engines (two cruise, six boost) were clustered behind the cockpit, while the top of the fin was occupied by radar and ESM gear. In practice, this wasn't particularly useful because the Loon's low altitude limited the radar horizon and made it dependent on other platforms for targeting information. But operating at low altitude also made it harder to see, potentially allowing it to play the role of a very fast missile corvette. The fall of the Soviet Union meant that the Russian government didn't really see things that way, and the one completed Loon was laid up, while a second unit, 80% complete, was suspended and for several years there were discussions of converting it into a SAR platform before this idea was scrapped.

The remains of VVS-14

Only one major ekranoplan was actually built to a design that didn't come from the Central Hydrofoil Design Bureau. Robert Bartini, an immigrant from Austria-Hungary, had been one of the Soviet Union's more innovative aircraft designers, and he became interested in the ekranoplan concept, although his version was definitely intended to be able to operate out of ground effect as well as in it. His chance to put at least some of his theories into practice came in the 1960s, when the Soviet government commissioned a VTOL ASW ekranoplan as part of their strategy to counter the American Polaris program. Details of the plan are hazy, but as best I can tell, the plan was to use the ekranoplan as something more like a very fast and reasonably stealthy surface ship,⁸ landing on the water and deploying a dunking sonar as its main sensor.⁹ The design Bartini came up with, known as VVS-14, had a very long central wing/fuselage section with a more conventional-looking wing outboard, and used two engines for cruise and 12 more to give it vertical takeoff ability, taking advantage of the ability of the center wing section to trap the exhaust of the takeoff engines and form an air cushion. This would give it the ability to operate from either land or water, in the latter case using inflatable floats. Astonishingly, nobody seems to have pointed out that everything involved with this was insane, and a prototype was actually built, first flying in 1972. But the lift engines were never delivered, and while attempts were made to rework the VVS-14 into a more conventional ekranoplan with an extra pair of takeoff engines, and while this was successful in creating a flying craft, nobody was able to figure out what to do with it, so it was left to rot in a museum.

X-114, one of the Lippish prototypes

In the decades since the demise of the Soviet ekranoplan program, there have been numerous attempts to revive the concept. Besides the desperate attempts of Russian design bureaus to attract outside money during the dismal years of the 1990s and 2000s, various efforts have taken place in other countries. Boeing proposed a massive ekranoplan transport under the name Pelican in the early 2000s, which would have been about twice the size of the company's 747 and weighed six times as much, operating from land-based airfields to avoid the drag that comes with operating from the water. More recently, DARPA spent the past few years working on a designed dubbed "Liberty Lifter", abandoning in in mid-2025. In Germany, designer Alexander Lippish, best known for the Me 163, decided to turn his talent for extremely sensible aircraft to ekranoplans, developing a radically different reverse-delta configuration in the 1970s. Several small prototypes flew, and it proved to be stable in both pitch and height, which has made it popular with designers of small ekranoplan ever since. And there have been plenty of small companies, far too many to be worth mentioning here, that have attempted to commercialize the concept since then. Despite this, it's not entirely clear if there's even a single one in commercial service right now, although several companies, most notably REGENT are working to change this. I strongly suspect that the problems of rough water will doom them as it has all previous attempts. Frankly, the market here reminds me of that for airships. While the concept is seductive and there's always someone ready with a cool presentation about how this is the future of transportation, the fact that Earth has weather means that conventional versions will soldier on, and the ekranoplan, unlike other exotic hulls, will always remain a curiosity.