Like birds and fishes, mankind has always been fascinated by the amphibious species. The ability to traverse on almost any terrain had caught the attention of many inventors, engineers and was regarded as a potent transportation tool by adventurous merchants and military generals alike. Centuries of fascination, engineering and ingenuity has resulted into the development of the modern day amphibious ACV (Air Cushion Vehicle), more commonly known as the hovercraft.
Historical and modern day development.
Throughout the industrial revolution, the concept of pressure was widely explored and studied upon and served as a basis for designs which used high air pressure to life objects from surface. Most of these designs however required the vehicle to in linear motion so that the required pressure could be generated. These vehicles were usually termed as ‘water’ effect vehicles and it was only in 1915 that the first successful vehicle was built. The vehicle, built by Austrian National Dagobert Muller, used 5 aero engines – four for underwater propellers and 1 for blowing air under the hull. The vehicle could successfully operate with a top speed of 32 knots and was benifited vastly due to the air pressure under the hull. However it couldn’t make a transition to land like a mo0dern hovercraft and also required constant motion to be lifted slightly.
In 1929, the concept of blowing air under something to keep it aloft was introduced by Andrew Kutcher from Ford. His contraption, the Levapad, was a metal disk with a hole in its center through which air was blown to keep the disk aloft. Over the years of experimentation he also realized that the concept can be used to replace wheel in trains. One of the major flaw of the Levapad was the lack of proper system to contain the high pressure so that the disk hovers higher with lesser air being blown. Another design was conceived by a Finnish engineer Tobio J. Kaario, who proposed using an engine to blow air and life the vehicle among others.
However none of these developments match that of Sir Christopher Cockerell. Mr. Cockerell was the first to design and develop various components used in he present day hovercraft, including annular rings and skirts. He also discovered the effect of ‘momentum curtain’ wherein he observed that fast moving air proved as a barrier for air surrounding it. This effect ultimately resulted in hovercrafts using less airflow to gain the same amount of lift. Infact, a modern day hovercraft would use 1/4th times lesser airflow than a helicopter to gain lift. One of the first prototypes, the SR N1 was also built by Cockerell’s group and demonstrated the power and applications of a modern the hovercraft. The SR N1 could travel over land and water with relative ease and could also perform the transition smoothly. Later developments allowed the SR N1 to climb over obstacles, move a=quickly and efficiently on both surfaces. As the concept and prototype gained popularity, many other companies started working on their own designs and commercialized the hovercraft as a ferry.
Working of a modern hovercraft.
A modern day hovercraft is powered by one or more engines, depending upon the size, to lift and drive it. The engines power large fans which suck air inside the skirts of the hovercraft, inflating them and crating an air cushion. The engines also power additional propellers which are used to move the now cushioned vehicles through the surface, whether land or water. Some designs however, omit the use of gearbox, and use some of the air sucked in the skirts while the rest and used to push the craft forward.
While an engineering marvel, hovercrafts were commercially viable to ferry people. It usually favored calm water surfaces, blew a lot of dust on ground and also consumed high amount of fuel. However the hovercraft still catches fascination of some people and there are a few commercial ferries available over the world.
Hovercrafts, instead found their niche is civilian search and rescue, support services and tactical military operations. Due to their ability to traverse on land and water quite easily many search and rescue teams have utilized them to rescue distressed civilians in coastal and other difficult terrains like mud, thin ice, swamps, etc. Its amphibious capability allows armies using them to tactically insert forces in an area without much hassle and little regard for the geographical terrain. This led to development and production of military hovercrafts across the globe with many models being in active service.