This episode of Real Engineering is brought to you by Brilliant, a problem solving website that teaches you to think like an engineer. At the height of the Cold War, with nuclear anxiety at a fever pitch, the United States launched their first spy satellites, the Corona. Tasked with photographing deep inside the Soviet Union. US Intelligence was focused on searching for signs of nuclear weapon development and testing, but found a lot more than they bargained for. These early satellites were launched with rolls of film with no-way of transmitting the data contained within them to earth through electronic means, and thus the films had to recovered and developed here on earth.
Once the film was filled the satellite would eject a re-entry vehicle, containing the precious undeveloped photos, back to earth where they were caught by a passing plane as they drifted down. On one such mission a strange object began to emerge from the Caspian Sea as the film developed. A gigantic aircraft, nearly 100 metres long with short stubby wings, much too short to fly like a conventional aircraft. US Intelligence had never seen anything like it. As they received more pictures, it was clear that the craft was moving at the same speed as a traditional aircraft, while outsizing even the largest of modern day American military planes like the Lockheed C-5M.
It was even emblazoned with the flag of the Soviet Navy, not the Soviet Air Force. This discovery set alarm bells off within US intelligence. Had the Soviets developed a breakthrough in propulsion which would give them the upper hand in naval combat? Confused on what they were seeing the US dubbed the machine the “Caspian Sea Monster”, but the Soviets weren’t developing a gigantic hydrofoil or seaplane. This giant aircraft secretly being developed was actually an ‘ekranoplan’, a gigantic vessel capable of skimming across the ocean’s surface at high speeds. In 1962, the Central Hydrofoil Design Bureau assigned chief designer
Rostislav Alexeyev to begin working on a prototype plane. Alexeyv had cut his teeth developing hydrofoil planes, like the Raketa. These craft could easily be defined as a boat. They used a hydrofoil, essentially a wing designed to act in water, to lift the boats hull out of the water as it gained speed, allowing it to reduce drag and increase top speeds, but the Soviets wanted to take it a step further. The Ekranoplan would make use of something called “ground effect” to fly at a very low altitude above the ocean’s surface. Ground effect occurs when a fixed winged aircraft flies at an altitude less than the length of it’s wingspan. As the large masses of air come into contact with the aircraft, the profile of the wing deflects the air downwards, compressing the air between the wing and the ground. This trapped air causes an area of higher than normal pressure underneath the wing resulting in a boost to lift.
This happens with all aircraft during take off and landing, and is something all pilots have to learn to deal with. For example, some planes can get off the ground when overloaded, but won’t be able to climb past the altitude where ground effect is in play. Ekranoplans are designed in such a way to maximise this effect, and never leave the ground effect zone. Just as our plane can get off the ground when overloaded, the Ekranoplan can be heavier without the need for extra power. An aircraft with this ability would be a powerful tool in open-sea combat. It would fly under enemy radar for much longer , due to radar shadow under the earth’s curvature. It would be capable of transporting tonnes of equipment and personnel quickly, while avoiding enemy mines and torpedoes, or it could be fitted with weapons of its own to quickly attack enemy ships before escaping. Imagine if a vehicle like this was available for the D-Day landings, the largest amphibious assault in history. The allies would have been able to transport tonnes of equipment and troops across the channel in a 15 minute trip. The appeal of the technology was enormous, and the first prototype named the ‘KM’ was built and secretly transported to the Caspian Sea to begin testing. This enormous vehicle instantly became the largest aircraft ever built with a wingspan of 37.6 metres and a length of 92 metres.
It weighed a massive 240 tonnes but it could take-off with almost double that. Powered by eight Dobrynin VD-7 turbojets mounted at the front and two on the tail which provided a total of 1,275 kilonewtons of thrust, about 30% more than a Boeing 747.. The first test flight of the KM took place on the 16th October 1966 with Chief Designer Alexeyv on board. At the time, it was forbidden for Soviet aircraft designers to be on board test vehicles like this, in case they were involved in an accident. But Test Pilot Vladimir Loginov lobbied for Alexeyev to be on board to allow him to experience and refine his designs. The first tests were successful, showing that the KM could fly with optimum fuel efficiency at 430km/h and with a maximum operational speed of 500km/h. During some high speed tests, it’s claimed that it achieved a speed of 650 km/h.  The KM was a valuable proof of concept and laid the groundwork for all future Ekranoplans. Alexeyv took the les sons learned and began to develop a new transport version design specifically for the transport of military equipment and troops, called the Orlyonok. This was a much smaller variant, 58 metres long with a 31.5 metre wingspan, and a maximum takeoff weight of 140 metric tonnes. It’s engine layout was fascinating, with a massive NK-12 turboprop engines mounted on the tail as far away from the salt water as possible. These massive 6 metre diameter counter rotating turbo-propellers developed 11 thousand kiloWatts of power, making it the most powerful turboprop engine to ever enter service.  It also featured two nose mounted turbofan engines with air intakes on top of the nose to minimise water intake. The exhaust of these engines were pointed under the wings to enhance the ground-effect phenomenon by bolstering the air cushion with the high pressure output of the jet engine. These engines were only needed on take-off before the plane could gain the speed needed to develop enough lift through the wing in ground effect. Once this was achieved they were shut down to decrease fuel consumption. The Orlinok featured a nose mounted cargo-door and wheels to allow the plane to drive onto land and unload. This was a fully functional Ekranoplan and actually entered and remained in service until 1993, although only 4 were ever built.  Details from here vary, and I found it difficult to find any authoritative source of information on what happened to Alexeyev after the development of the Orlinok was complete. Some say he crashed in the KM, others in the Orlinok, and others say he crashed in a Volga 2, a small passenger transport Ekranoplan, but they all seem to point towards Alexeyev being fired as chief designer as a result and dying a short time later. Whether that was from injuries from the crash or natural causes I have no idea. With Alexeyev out of the picture and the Soviet Union on the brink of collapse, development of Ekranoplans in the Soviet Union slowly began to fissile out. They managed to develop a slightly smaller version of the KM, designed to launch anti-ship missiles while out at sea. In 1987, the first version of this vehicle was built and named ‘Lun’. This vehicle weighed 286 tonnes, had a length of 74m and wingspan of 44m. The tail mounted engines were removed completely. It was instead powered by eight NK-87 turbofans mounted at the front of the craft, each producing 127 kilonewtons of thrust. The Lun entered the Soviet Navy in 1987.However, with the collapse of the Soviet Union in 1991, only one model was ever completed and it remains in its dry dock on the shores of Caspian Sea to this day. The idea of a wing in ground effect plane has its merits, but it simply never found its niche in any military. The Germans made a much smaller ekranoplan in the 70’s called the X-114, but it never made it into service. The Chinese also experimented with an ekranoplan called the XTW-4 which was built in 1999 and went through multiple tests a year later. The vehicle was once spotted in a Chinese shipping port on Google Maps but has since vanished. While in 2002, Boeing presented their plans to build the largest ekranoplan ever, dubbed the Pelican. They claimed the craft would be longer than a football field and capable of hauling 17 M1 Abram tanks across an ocean. But the US congress rejected the plans in 2005. There just wasn’t a need for such a plane.  Wing in ground effect planes may yet find their niche, but for now safety and reliability concerns are it’s primary road block. Flying at such a low altitude provides very little time for corrective maneuvers, and poor weather with high waves or wind prevents any ekranoplan from operating. Some have sought to develop smaller passenger versions, like the A-050 which the Russian embassy of South Africa, your definitive Russian news source, claimed it would be ready for service in the next 3 years.  Vehicles like this could find a valuable niche in archipelago regions, like South East Asia, where increasing wealth and populations combined with relatively short distances between islands could provide a market for these temperamental craft. However traditional planes will always remain a much more efficient and reliable form of transport over long distances, as flying in the lower density air of the upper atmosphere drastically decreases drag. So these passenger versions would have to operate extremely short haul distances where airliners waste time during climbing and ascent. This technology is perfectly viable for the right application, and we may yet see someone solve the problem and build a successful business from it. 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