There are several kinds of vehicle that use the concept of high pressure air underneath wings and the actual bodies of flying craft. Most of them operate under a principle known as ground effect, and sometimes water effect and not really known as hovercraft. The primary variation between the two principles is that hovercraft can raise themselves whilst stationary, while many vehicles are designed to lift only when moving forward – they need motion. Examples of these kind of vehicles are sometimes called hydrofoils. One of the first historical records of the principles of craft that empoyed the word ‘hovering’ was by Emanuel Swedenborg a Swedish scientist, around seventeen sixteen.
Austrian Dagobert Müller put together history’s very first water effect craft in nineteen fifteen. It looked like a part of a big aero-foil, which produces an area of reduced air pressure over the structure in the same way that an airplane does - the vehicle was pushed forward by 4 airplane engines turning 2 propellers under water, and another one pushed air underneath the bow of the vehicle to raise the pressure of the air beneath it. Only if moving forward could the vehicle get air underneath the front of it, thereby creating some lift. The craft additionally needed some water underneath it to fly and it couldn’t move from water to land or any other surface. It was created as a rapid torpedo boat with a max speed of about 59 k per hour. After going through a trial period it was fitted out with a torpedo battery and heavy automatic weapons so it could operate around the Adriatic sea. It didn’t see fighting situations, because as the war moved on it was moth-balled because of no interest and little need was seen for it – it’s engines were sent back to the Air Services.
An aeronautics engineer called Toivo J. Kaario developed a design for a working version of a craft raised on a cushion of air and even put together a moving example – it was named the Surface Soarer. The craft included some present day features, like an engine forcing air into a supple envelope to generate the required lift. He didn’t get any funds to develop his practical ideas. A Russian designer, Levkov, conceived and fabricated a several similar vehicles in the nineteen thirties, and one of his designs reached speeds of 130 k per hour in trials. As it turned out, the beginning of the second world war stopped progress on his working ideas. Another engineer in the US, C. Fletcher, was the inventor of an air cushioned craft using a walled skirt material. As the work was considered classified by the American authorities, he couldn’t put a patent on it.
At the end of WW2 several groups started to develop hovercraft type vehicles, which included hydrofoil and wing effect. The Russion Central Hydrofoil Design Bureau went back to the early designs first created by Levkov, and came out with many such vehicles during the ensuing thirty years. That said, Alexeyev's project designs were firmly prototypes, and were never produced for practical purposes. A celebrated example was the Lun-class, a huge boat driven by eight jet motors and capable of firing missiles. Opposite to Levkov's principles, these craft didn’t use an engine to create lift, utilizing forward motion and stubby wings to generate the desired lift at traveling sufficiently fast. This was quite a one-of-a-kind evolution of this kind of vehicle but were really classified as real practical hovercraft.
In the fifties and sixties in Canada, John Frost began experiments in the field, finding that he could create a torus of high air pressure by forcing the air downwards over a surface with a convex shape. This project led him to develop the Avrocar with the for the US Forces, a craft of quite mediocre capabilities more like a present day helicopter. When tested, it couldn’t fly higher than several feet from the ground and was limited to velocities less than 45 k per hour. After some trials development was stopped in 1961.
The concept of the present day hover vehicles is usually linked to designer Sir Christopher Cockerell, who was the first to succeed in attaching a rubberized skirting strip to the side of the bottom of the vehicle. He discovered the principle idea of his successful designs while examining the ring of air flowing when air at high pressure was forced into the ring space between a couple of tin cans arranged concentrically – not that it matters, but one was cat food and the second coffee. The arrangement created an annulus of air flow flowing as he had thought, but he also found an extra benefit he wasn’t even looking for - the curtain of rapidly moving air acted as a kind of fence to the air on both sides. The phenomenon, the momentum curtain, might be utilized to capture air at high pressure in the region inside the ‘curtain’ creating lift proportional to that pressure, and not just the flow of air. As the theory goes, just a significantly reduced quantity of moving air would be required to produce lift and a lot less than a concept relying on the speed of airflow to generate lift, similar to the principles of helicopter action. As far as the power required, a hovercraft needs something like 25 to 50 per cent of the power need to fly a helicopter.
He constructed many models of this innovative hovercraft concept in the early fifties (a long time before it was possible to find a hovercraft for sale in the marketplace!), which featured an engine fitted to direct air from the front of the vehicle into a region underneath it, effectively creating both foreword motion and also lift. He showed the models hovering over several government office carpets before a wide variety of government authorities and officials, and his ideas were promptly classified as secret. However, after long efforts to get suitable funding, the military of all flavors were just not interested.
Author: Jim Bruce
Rating: 9 out of 10
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