Ship with Air Cushion
Sudno na Vozdushnoy Podushke [SVP]
The world's first experimental hovercraft of the skeg type was built in the years 1934-1939 by the Soviet designer Vladimir Levkov. The aim of the work of Levkova was extremely fast boats for military use. He created over a dozen different types of vessels weighing from 1.5 to 15 tons. All of them were destroyed during the Second World War. Levkov also experimented with working models SVP cell-type, but the development work did not get very far.
The idea of ??lifting a ship out of the water into the air to reduce drag and increase speed has always been very attractive to shipbuilders. A hundred years before the appearance of the first steamships and two hundred years before the first flights on airplanes, there was already a project that can be called the prototype of modern air-cushion ships. In 1716, the Swedish scientist Emmanuel Swedenborg proposed using blades and muscular force to pump air under a canvas canopy on which people and goods could be moved. The idea remained on paper, since no muscular force could lift such an apparatus.
It became possible to translate something like this into reality only with the advent of internal combustion engines. In 1915, the Austro-Hungarian officer and inventor Müller von Tomamühl built an experimental torpedo boat with air pressure "Fersuchsgleitbot", which was able to accelerate to 40 knots (just over 70 km / h). But it was suggested not only on water to accelerate cars with the help of an air gap. In 1926, Konstantin Tsiolkovsky expressed the idea of ??a high-speed train without wheels, the movement of which would be based on the use of air pressure.
The Soviet Union was the first in the creation of operating "air ducts" of the skeg type. Work on them began in 1927 under the guidance of Professor V.I. Levkov. Hovercraft (hovercraft) were developed for military use. In the late 1930s, Levkov's boat "L-5" weighing 9 tons reached a speed of 73 knots (more than 135 km / h). It was built on a skeg-type design.
Levkov also worked on the chamber-type SVP, but this direction did not receive development. Christopher Cockerell, an Englishman, is considered the inventor of the nozzle method of forming an air cushion, which is used today in most of the SVPs. Legend has it that he discovered the principle of the air barrier by experimenting with two cans inserted into one another. In 1955, Cockerell patented a hovercraft design for the hovercraft. And in 1959, the first ship he built, the SR-N1, crossed the English Channel in 20 minutes.
All hovercraft operate on the same principle - under the bottom of the hull, excess air pressure is created, which raises the vessel above the surface. Overpressure is produced by special air blowers. This technique allows the hovercraft to move at a sufficiently high speed and go to the unequipped shore, which is important for fast unloading of the vessel. SVP can be applied at any time of the year.
SVPs of various designs can be divided into two large groups: skeg and amphibians. The advantage of the latter, as the name implies, is that they are able to move on different types of surfaces - on water, ice, flat ground, swampy terrain, sandy beaches. These include vessels built according to chamber and nozzle schemes.
In chamber hovercraft, air is pumped under the domed bottom and flows freely around its perimeter. In nozzle vessels, the air cushion is enclosed by an air curtain created by nozzles around the bottom. With the invention of the "skirt" - a soft air cushion fence - this type of hovercraft became the most widespread. The downside of amphibians is their relatively poor handling, due to the lack of contact with water. In strong winds, the speed of the vessel decreases, and it may simply be blown off course.
The name of the skeg SVP comes from the English word "skeg" - an onboard float or limiter. In skeg vessels, to reduce air consumption, the pillow is fenced on the sides with rigid skegs or balloons. These hovercraft, unlike amphibians, are used mainly on the water, since the skegs must be immersed in water. In this regard, skeg vessels are more stable than amphibians. SVP of this type in terms of general design, power plant and control is closer to traditional ships.
The designers of skeg boats today use various modifications of the scheme proposed in the 1930s by Vladimir Levkov. Since the 1960s, the USSR has been serially producing passenger skeg hovercraft. For example, "Zarnitsa" with a displacement of 14 tons, carrying 48 passengers at a speed of 36 km / h, or a sea "Chaika" with a displacement of 45 tons, capable of taking on board up to 80 people.
The "golden age" of the SVP fell on the 1960s-70s, when designers and shipbuilders pinned great hopes on the new type of ships. However, practical application has shown that hovercraft are quite expensive in construction, operation and maintenance. This type of transport did not receive widespread distribution, as the inventors of the hovercraft dreamed about. And yet there are areas where there is no alternative to hovercraft, and their disadvantages are more than compensated for by the advantages.
The Soviet Union, since 1965, produced more military ACVs than any other country. Amphibious hovercraft in the 1970-1980s were a true symbol of the Soviet fleet, modern and rapidly developing. The Soviet Union was also one of the first nations to use a hovercraft, the Bora, as a guided missile corvette, though this craft possessed rigid, non-inflatable sides. With the fall of the Soviet Union most Soviet military hovercraft fell into disuse and disrepair. Only recently has the modern Russian Navy begun building new classes of military hovercraft.
The Soviet Union was the world's largest developer of military hovercraft. Their designs ranged from the small Czilim class ACV, comparable to the SR.N6, to the monstrous Zubr class LCAC, the world's largest hovercraft. The increase in the size was profitable because with the growth of the air cushion area reduced the unit cost of power and improved seaworthiness of ships. Their largest ACV was the 60-knot, 380-ton Pomornick or Zubr-class ACV first launched in 1986. Nine of these Zubr-class ACVs were built and used by the military of Russia, Ukraine and Greece. At 187 ft in length, they are among the biggest ACVs in the world, but just two feet longer than the stretched SR-N4s.
An amazing total of over 30 inventors had the idea of using air to reduce the drag of over-land or over-water vehicles, prior to the significant ground-breaking work of Christopher Cockerell in the UK, which began in 1953 and was patented in 1955. Cockerell, who was later knighted for his work, emphasized the need for a thick cushion of air to reduce drag. It was this significant realization, of course, that quickly launched a new world-wide industry. Not all the early inventors patented their work, however, and they add, at least, another dozen to the list of thirty, giving an amazing total of over forty inventors doing work on hovercraft before Cockerell began his work in 1953. Before the Saunders-Roe SR-N1 crossed the English Channel without a skirt in 1959, there were a total of eight patents issued to different inventors claiming the virtue of flexible skirts.
The simplest method of forming an air cushion chamber has the air blown by fans at the bottom of the dome, flowing freely around its perimeter. The greater the flow of air, the higher the ship climbs, but it requires a high amount of energy, so this method is not economical. To reduce the air flow from the vessels for movement just above the water surface, on the sides of the pillow shield submerged rigid walls or narrow enclosures - the skeg type. In skeg vessels, the rigid enclosure is always partially immersed in water, and therefore the skeg ship can only move on the water surface, not on dry land.
More economical at high altitude, jets of air flowing out of the nozzles are bent so that the centrifugal forces acting on moving along curved trajectories of air particles, are balanced by increased pressure in the pillow, and airbag, as it were "locked" these jets. To increase the height of the lift and reduce power costs for the formation of an air cushion on its perimeter additionally installed flexible fencing.
The chamber scheme applied on an experimental passenger riverboat "Neva", built in 1962 in Leningrad. And Gorky shipbuilders built skeg type boat "Gorkovchanin" for the carriage of passengers on shallow rivers, the pilot boat "Rainbow" and experiental passenger ship "Sormovich" displacement of 32 tons with a nozzle pattern in a formation of pillows.
The GAZ 16 was created in 1962 under the leadership of designer AA Smolin. The idea was to design a car to overcome the impassable abyss by an air cushion. Teh car body gave a shape capable of holding the bottom pressure area without fencing. At the meeting with the off-road lifted 15 cm above the surface and crawled obstacle at a speed of 40 km / h. The result was an intermediate, an oversized vehicle, hardly someting to put on the road and irrationally consumed power lifting propellers on an air cushion. After a crash during the tests the was project closed, the remains of the car remained in the Gaz museum.
The Gus class was a military version of the Soviet Skate class 50 passenger hovercraft, and was designed to transport infantry and light equipment. Between 1969 and 1974 32 Gus class assault hovercraft were constructed. They were deployed to all Soviet naval fleets except the northern fleet, and were used extensively along the Amur River border with China. Three Gus class LCAC could be carried by the Ivan Rogov class assault transport. They were replaced by the larger Tsaplya class LCAC and more recently the smaller Czilim class ACV. All Guss class hovercraft were believed scrapped in the early 1990's.
The Aist class was built to roughly the same size as the British SR.N4 commercial channel ferry. The Russian name for this class is "maly desantny korabl na vozdushnoy podushke" meaning "small air cushion vehicle". The Aist class prototype was built in 1970 and the type entered production in Leningrad in 1975. It was produced there at a rate of about six every four years. By the early 1990s twenty to twenty four had been produced. They began to be withdrawn following the fall of the Soviet Union, and by 2004 only six remained, in two levels of configuration.
A modified main engine intake was installed on all Russian Navy Aists in service with the Baltic Sea fleet. These intakes are believed to include special filters to reduce the ingestion of salt water, sand and dust particles into Aist's engines and machinery, limiting the effects of salt water corrosion. The Aist suffered from high cushion pressure, and produce exceptionally heavy cushion spray, especially at low speeds.
The Lebed class is the Russian Navy equivalent to the U.S. Navy LCAC, thought the U.S. version entered service seven years later. The Lebed class entered service in 1975, and by the early 1990's twenty had been produced. The ship has a bow ramp with a gun on the starboard side and the bridge to port. The Lebed class can be carried by the "Ivan Rogov" class assault transport ships. The type began to be withdrawn following the fall of the Soviet Union, and by 2004 only three remained. 533 is in the Northern Fleet, while 639 and 640 took part in the Caspian Sea exercises of 2002.
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