Christopher Cockerell and the History of the Hovercraft By Mary Bellis Updated August 17, 2016. A hovercraft is a vehicle supported on a cushion of air supplied by a powered fan mounted on the craft. The hovercraft was invented by Christopher Cockerell in 1956. The theory behind one of the most successful inventions of the 20th century, the Hovercraft, was originally tested in 1955 using an empty KiteKat cat food tin inside a coffee tin, an industrial air blower and a pair of kitchen scales. Sir Christopher Cockerell developed the first practical hovercraft designs, these led to the first hovercraft to be produced commercially, the SRN1. Cockerell's idea was to build a vehicle that would move over the water's surface, floating on a layer of air. This would reduce friction between the water and vehicle. To test his hypothesis, he put one a smaller can inside a larger can and used a hairdryer to blow air into them. The downward thrust produced was greater when one can was inside the other rather than air just being blown into one can.

Background Cockerell was born in 1910 in Cambridge, where his father, Sir Sydney Cockerell, was a museum curator. Christopher Cockerell went to the primary school of St. Faith's. He studied at Gresham's School in Holt, Norfolk. He matriculated to Peterhouse, Cambridge, to read mechanical engineering and was tutored by William Dobson Womersley. He later returned to Cambridge to study radio and electronics. Cockerell worked for the Radio Research Company until 1935 and then for the Marconi Wireless Telegraph Company from 1935 until 1951. During the war years, Cockerell worked with an elite team at Marconi to develop radar, a development which Churchill believed had a significant effect on the outcome of the Second World War, and Cockerell believed to be one of his greatest achievements. While at Marconi, Cockerell patented 36 of his ideas. Hel was knighted for his achievement in 1969. The Hovercraft It occurred to Cockerell that if the entire craft were lifted from the water, the craft would effectively have no drag.

This, he hoped, would give the craft the ability to attain a much higher maximum speed than could be achieved by the boats of the time. Cockerell's theory was that instead of just pumping air under the craft, as previous inventors had, if the air were to be instead channelled to form a narrow jet around the perimeter of the craft, the moving air would form a momentum curtain, a wall of moving air that would limit the amount of air that would leak out. This meant that the same cushion of high-pressure air could be maintained by a very much smaller engine; and for the first time, a craft could be lifted completely out of the water. He tested his theories using a vacuum cleaner and two tin cans. His hypothesis was found to have potential, but the idea took some years to develop, and he was forced to sell personal possessions to finance his research. BBC ON THIS DAY | 11 | 1959: Hovercraft marks new era in transport About This Site | Text Only 1959: Hovercraft marks new era in transport A revolutionary new form of transport which can operate on sea and land has been officially launched in the Solent, off England's south coast.

The Hovercraft, which has been described as a cross between an aircraft, a boat and a land vehicle, was invented by boat-builder Christopher Cockerell. Dubbed a "man-made flying saucer", the hovercraft is propelled on a cushion of air created by its own fan power. It therefore hovers just above the waves at sea and avoids any irregular surfaces on land. Christopher Cockerell, from Lowestoft, began working on a hovercraft model in the mid-1950s. He said he first came up with the idea when he was thinking how to make a boat go faster by reducing the amount of friction caused when it travels through the water. He first tested the 'hover' theory using a cat food tin inside a coffee tin, with an industrial air blower and a pair of kitchen scales. In 1955 he convinced the Ministry of Supply to back him but he was not able to commercially develop the product immediately as his idea had been placed on the government's secret list because of its potential benefits to the military. In 1959 Cockerell managed to get his idea removed from the secret list and formed the Hovercraft Development Company Ltd.

He obtained funding from the National Research Development Council of �150,000 to develop the project. A contract to build the first Hovercraft was awarded to Saunders Roe, the flying boat firm at Cowes, at the beginning of this year. The SRN-1, an experimental model, is 29 feet long and 24 feet wide and weighs 6,600lb. Following today's launch of the SRN-1 hovercraft in the Solent, Saunders Roe announced it is now planning a prototype up to ten times as big and weighing 40 tons. The hovercraft, which has controls very similar to those in a helicopter, can reach speeds of up to 25-knots and it is hoped that at some stage in the future it will be able to cross the English Channel in as little as 20 minutes. Hovercraft history.

The history of hovercraft and air cushion vehicles Early thoughts of air cushions The idea of using an air-cushion as a means or aid to acceleration and reduction in (hydrodynamic) drag was first explored by Sir John Thornycroft, a British engineer, who, in the 1870's built some experimental models on the basis of an air cushion system that would reduce the drag of water on boats and ships. In 1877 he successfully patented the idea and his theory was that if a ship's hull was given a concave bottom, which could be filled - and replenished - with air, it would create significant additional lift. And so the air cushion effect was born. Decades later scientists and inventors were still busy with his ideas but without any practical applications. With the coming of the airplane however, it was noticed that additional lift was obtained if the plane flew closer to land or water, creating a "funnel effect", a cushion of air. The air lift that this funnel effect created differed with the type of wing and its height above ground. The effect was strongest if this height was between one half and one third of the (average) front-to-rear breadth of the wing. Also known as "chord".

The next two decades saw little interest in air cushion development. World War 1 saw a huge increase in the development of the airplane as a military weapon and even though the ground effect was known, airplanes were designed for speed and manoeuverability in the air rather than close to the ground. But because of the many difficulties these models were developed as flying boats rather than air cushion vechicles or ground effect flyers, using the ground effect for take-off from the water. No real hovercraft came along until the 1950's. The Boeing B-1 Flying boat in 1919. (c) Airline History . Flying boats, however, are an integral part of aviation and transport history becoming popular and practical in an era when landing strips and airports were still sparse. They are still used today and many of the older models that proved their worth the world over are lovingly maintained by collectors and enthusiasts. We highly recommend Airline History for a complete pictorial overview of Flying Boat history.

Early uses of the air cushion effect 1920 - 1949 The German-built Dornier Do-X flying boat proved the reality of Thornycroft's theory in 1929, when, during an Atlantic crossing, it flew much closer to the ocean's surface than was usual in order to take advantage of the air cushion effect. The trip time was significantly reduced as a result and the aircraft's performance that much greater. The Do-X Flying Boat became quite a legend in its day, especially when it started flying around the world in 1926. Despite its enormous fuel consumption - around 400 gallons of gas per hour - it was one of the first large passenger planes capable of 150 seats. But its engines tended to overheat and, after its arrival in New York in 1931 it was refitted with American water-cooled engines. During World War 2 the Dornier factories made several Do-X flying boats for a variety of purposes, from transatlantic mail carriers to bombers.

(For more detailed information on Dornier's Do-X see also Dafkurse (D), Aviation Posters , EADS (D), Avions-Legendaires (F) articles.) Many flying boats were built during this era, and they formed the forefront and backbone of many aviation routes across the world, especially on the long haul destinations. The Russian Sikorksy proved exceptionally talented at manufacturing flying boats and many airlines ordered their planes from his factories. The military are always at the forefront in taking advantage of technological developments, and so it was with the air cushion effect. Another decade later, for example, during World War 2, scouting aircraft made good use of the air cushion effect to extend their reconnaissance flights. Dornier's Do-X Flying Boat The Do-X at rest in Rio de Janeiro's harbour with Sugarloaf Mountain as backdrop. (c) EADS . The first real hovercraft - 1950 to 1960 The successful use of the air cushion effect was not lost on engineers after World War 2 was over and in the early 1950's British, American and Swiss engineers started to rethink Sir John Thornycroft's problem.

The Englishman Christopher Cockerell, commonly seen as the father of the hovercraft, being retired from the army, settled into boat building where he soon got captivated by Thornycroft's problem of reducing the hydrodynamic drag on the hull of a boat by using some kind of air cushion. His theory was that, instead of using the plenum chamber - an empty box with an open bottom as Thornycroft had devised - air was instead pumped into a narrow tunnel circumnavigating the entire bottom, it would flow towards the center and form a more effective air cushion. This peripheral jet would cause the air to build up enough pressure to equal the weight of the craft and, as it would have nowhere to go, the pressure would force the craft up, clearing it off the ground altogether. Cockerell successfully tested his theory and filed his first patent in 1955. The year after he formed a company called Hovercraft Ltd. He further envisioned and partially worked out other problems of the hovercraft principle that still have to be fully exploited by modern hovercraft builders. One of these was to re-use the air for greater overall efficiency.

Thinking that his air cushion vehicles would be eminently suitable as amphibious craft he approached the British Ministry of Supply, the government's defence equipment procurement authority with his findings. Soon after, in 1956, the air cushion vehicle was classified as "secret" and a construction contract was placed with a British aircraft and seaplane manufacturer. The result was the SR.N1 in 1959. The first SR.N1 weighed four tons and could carry three men. Its maximum speed was 25 knots (1 knot = 1.15 miles or 1.85 kilometres per hour) on calm water. It had a 6-inch (15 cm) rubberized skirt to make it easier to contain the air cushion on uneven ground. Significant wear and tear of the skirt through friction with the water at high speeds made it necessary to use more durable material and a rubber and plastic mixture was developed by 1963. The length of the skirt had also been extended to about 4 feet (1.2 m). By this time the Americans, the French, Japanese and Swedes had begun to be interested in the air cushion vehicle and its possibilities and companies sprang up the world over.

As far as experimental vehicles were concerned the Soviets, in their race for technological supremacy, were as prolific as the Americans in building craft of all sizes, shapes and types. Nothing was too weird or technologically theoretical but it was built. Especially after World War 2, during the 1950's and 1960's did experimental constructions reach extraordinary proportions. Other parts were also improved on, the craft now used a gas turbine engine, and was capable of carrying a payload of about seven tons, achieving a maximum speed of 50 knots. In June 1959 the SR.N1 crossed the English Channel, exactly 50 years after Louis Bl�riot's first flight across. Christopher Cockerell's SR.N1 hovercraft - 1959. Most of these craft were never put into production, many didn't even work properly, and modern day collectors will pay large amounts to add these craft to their collections. But not only governments and their military where entranced with the hovercraft and the air cushion vehicle, commercial companies like Ford Motor Company even came up with a hovercar which it called the "Glideair" in 1959.

It was never made commercially available for a number of reasons however. Parallel invention While Cockerell was busy designing and building his hovercraft in the U.K., across the Atlantic ocean Colonel Melville Beardsley was developing an air cushion vehicle of his own in the 1950's. The skirt around the ACV platform which contains the compressed air and makes the ACV a stable vehicle is the invention of Colonel Beardsley, for example, for which patent Cockerell later paid $80,000. The modern Hovercraft would not exist without it. A gifted man of many inventions Colonel Beardsley continued to work on ACV's for the US Naval laboratory across the river from Annapolis, Maryland through the 70's, leading to the modern amphibious military craft of today. He passed away in November, 1998, at the age of 85. Hovercraft and Ram-wing Craft in the 1960's and beyond Ram-wing craft Ram-wing craft were craft based on the principle of a wing using the ground effect described above. They were first developed by American aerodynamicists in the early 1960's.

In the global technological race that was going on during the 1960's an amazing array of wing-in-ground effect vehicles were built the world over. The Russians in particular explored this principle in a myriad of craft, like the Ekranoplan (shown at the right) and its infamous Caspian Sea Monster. Although few of the craft built got beyond the experimental stage, they did show that a combination of airfoil and air-cushion technology provided enough stationary hovering capability. This lift was then transferred into forward speed. Even though it was now possible to surpass the theoretical hover speed limit of around 320 kilometers per hour (200 mph), it became clear that the air cushion would not stay in place above these speeds and another solution had to be found. The ram-wing craft did prove beyond doubt that the air cushion principle was a practical one and had advantages over wheels and other methods of transport in certain situations. Early hovercraft - sidewall craft The air cushion principle found an application in the form of a sidewall craft in 1963, reusing the plenum chamber principle of Thornycroft.

The resultant craft was not able to leave the water because it was more of a boat but by using the plenum chamber and its air cushion effect hydrodynamic drag was significantly reduced. An advantage of a sidewall air cushion vehicle over the more amphibious hovering craft is that water propellers can be used, effecting in greater steering control, especially at low speeds. Another positive effect was the greater stability of the craft as opposed to the circular skirt. Hovercraft today and in the future Early interest in hovercraft enjoyed a peak in the early 1960's as everyone jumped to take advantage of this amazing vehicle. However, by the end of the decade only the British had produced a range of feasible and practical craft. The problems inherent of the air cushion vehicle, such as Cockerell and others had foreseen, regarding steering control, noise, salt and skirt erosion, caused many countries to abandon their hovercraft development programs in favour of other, more established multi-function vehicles or to use different vehicles specialised in each terrain or function.

Since the 1970's however, and especially over the last decade, a renewed interest in the hovercraft as (passenger) transport (see Hovercraft in Use ), military transport and weapons carrier (see Military hovercraft ) and exploratory vehicle (see Hovercraft news and development ) has taken ground, solving many of these problems in their development (see Hovercraft Construction ). Technology in general made large steps forward during the past twentyfive years, enabling organisations and governments, as well as many enthusiasts (see Hovercraft Clubs ) to enjoy the hovercraft vehicle in its many forms including the very popular Remote Control model size hovercraft! (See Model Hovercraft .) As far as hovercraft and their spinoff technology is concerned the future looks ever brighter. Ram-wing craft links Hovercrafts Hovercrafts by • Technology , Transport The hovercraft was invented by Suffolk boat builder Christopher Cockerell in 1956. The theory behind one of the most successful inventions of the 20th century - named the Hovercraft - was originally tested in 1955 using an empty cat food tin inside a coffee tin, an industrial air blower and a pair of kitchen scales.

Cockerell's idea was to build a vehicle that would move over the water's surface, floating on a layer of air. This would reduce friction between the water and vehicle. To test his hypothesis, he put a smaller can inside a larger can and used a hairdryer to blow air into them. The downward thrust produced was greater when one can was inside the other rather than air just being blown into one can. He developed the first practical hovercraft designs, which led to the first hovercraft to be produced commercially - the SRN1. RELATED ARTICLES Hovercraft History - The history of hovercraft. Hovercraft History A hovercraft, or air-cushion vehicle (ACV), is a vehicle or craft that can be supported by a cushion of air ejected downwards. It can travel over any relatively smooth surface, such as gently sloping land, water, or ice, while having no almost no contact with it. The first recorded design for a vehicle which could be termed a Hovercraft was in 1716 by Emanuel Swedenborg, a Swedish designer, philosopher and theologian.

His man-powered air cushion platform resembled an upside-down boat with a cockpit in the center and manually operated oar-like scoops to push air under the vehicle on each downward stroke. No vehicle was ever built, no doubt because it was realised that human effort could not have generated enough lift. In the mid-1870s, the British engineer Sir John Isaac Thornycroft built a number of ground effect machine test models based on his idea of using air between the hull of a boat and the water to reduce drag. Although he filed a number of patents involving air-lubricated hulls in 1877, no practical applications were found. Over the years, various other people had tried various methods of using air to reduce the drag on ships. Col. Melville W. Beardsley (1913-1998), an American inventor and aeronautical engineer, along with Dr. W. Bertelsen worked on developing early ACV's in the USA. It was not until 1952 that the inventor Christopher Cockerell designed a vehicle based on his 'hovercraft principle'. This was the missing link everyone else had not seen and made a commercial craft possible.

He was knighted for his services to engineering in 1969 for his work on the Hovercraft. Sir Christopher even invented the word 'Hovercraft' to describe his invention. Cockerell used simple experiments involving a vacuum cleaner motor and two cylindrical cans. He proved the workable principle of a vehicle suspended on a cushion of air blown out under pressure, making the vehicle easily mobile over most surfaces. His significant advance was developing a peripheral jet system to retain the air cushion under the vehicle. The supporting air cushion would enable it to operate over soft mud, water, and marshes and swamps as well as on firm ground. The British aircraft manufacturer Saunders Roe which had aeronautical expertise developed the first practical man-carrying hovercraft, the SR-N1, which carried out several test programmes in 1959 to 1961 (the first public demonstration in 1959), including a cross-channel run. The SR-N1 was powered by one (piston) engine, driven by expelled air, and could carry little more than its own weight and two men,and did not have any skirt at first trials.

It was found that the craft's lift was improved by the addition of a 'skirt' of flexible fabric or rubber around the hovering surface, to contain the air. The skirt was an independent invention made by a Royal Navy officer who worked with Sir Christopher to develop the idea further. The first true passenger-carrying hovercraft was the Vickers VA-3, which in the summer of 1961 carried passengers regularly along the North Wales Coast from Wallasey to Rhyl. It was powered by two turboprop aero-engines and driven by propellers. During the 1960s Saunders Roe developed several larger designs which could carry passengers, including the SR-N2, which operated across the Solent in 1962 and later the SR-N6, which operated across the Solent from Southsea to Ryde on the Isle of Wight for many years. Operations commenced on 24th July 1965 using the SR-N6 which carried just 38 passengers. Two modern 98 seat AP1-88 hovercraft now ply this route, and over 20 million passengers have used the service as of 2004.

As well as Saunders Roe and Vickers (which combined in 1966 to form the British Hovercraft Corporation), other commercial craft were developed during the 1960s in the UK by Cushioncraft (part of the Britten-Norman Group) and Hovermarine (the latter being 'sidewall' type hovercraft, where the sides of the hull projected down into the water to trap the cushion of air). In the late 1960s and early 1970s, Jean Bertin developed a hovercraft train dubbed the Aérotrain in France. His I-80 prototype established the world speed record for overland air cushion vehicles with a mean speed of 417.6 km/h (260 mp/h) and a top speed of 430 km/h (267 mp/h). By 1970 the largest British hovercraft were in service, the Mountbatten class SR-N4 model, each powered by four Rolls-Royce Proteus engines, regularly carrying cars and passengers across the English Channel from Dover or Ramsgate to Calais.

This service ceased in 2000 after years of competition with traditional ferries, catamarans, and the opening of the Channel tunnel. In 1998, the US Postal Service began using the British built Hoverwork AP.1-88 to haul mail, freight, and passengers from Bethel, Alaska to and from eight small villages along the Kuskokwim River. Bethel is far removed from the Alaska road system, thus making the hovercraft an attractive alternative to the air based delivery methods used prior to introduction of the hovercraft service. Hovercraft service is suspended for several weeks each year while the river is beginning to freeze to minimize damage to the river ice surface. The hovercraft is perfectly able to operate during the freeze-up period, however, it could potentially break the ice creating hazards for the villagers using their snowmobiles for transportation along the river during the early winter. The commercial success of hovercraft suffered from rapid rises in fuel prices during the late 1960s and 1970s following conflict in the Middle East.

Alternative over-water vehicles such as wave-piercing catamarans (marketed as the Seacat in Britain) use less fuel and can perform most of the hovercraft's marine tasks. Although developed elsewhere in the world for both civil and military purposes, except for the Solent Ryde to Southsea crossing, hovercraft disappeared from the coastline of Britain until a range of Griffon Hovercraft were bought by the Royal National Lifeboat Institution. There are an increasing number of small homebuilt and kit-built hovercraft used for fun and racing purposes, mainly on inland lakes and rivers but also in marshy areas and in some estuaries. Hovercraft typically have two (or more) separate engines (some craft, such as the SR-N6, have one engine with a drive split through a gearbox). One engine drives the fan (aka the impeller) which is responsible for lifting the vehicle by forcing air under the craft. One or more additional engines are used to provide thrust in order to propel the craft in the desired direction. Some hovercraft utilise ducting to allow one engine to perform both tasks by directing some of the air to the skirt, the rest of the air passing out of the back to push the craft forward.

Hovercraft - the History and Development The word "hovercraft" was probably coined by a newspaper, or even by Christopher Cockerell himself, to try to capture the essence of the vehicle. The more accurate modern description "air-cushioned vehicle" is more similar to the German Luftkissenboot. As with any new idea it is fuelled by need, finance, and curiosity, and motivated often by the need to improve an existing product; the word development covers all this and more. In view of Vosper Thorneycroft's involvement in military hovercraft in the 1960's, it is probably ironic that they were making use of an idea patented by Mr.Thorneycroft, a boat builder in the 1870's who suggested that by pumping air under a boat of a certain design it would help to lift the hull, reducing draft and thereby the drag of the vessel would be reduced. There is a patent to this concept taken out in 1910. Later in the 1920's a Swede developed an improvement on the ice sledge by propelling it with an air propeller in such a way as to get ram airlift on his platform.

Further development was not continued. The hovercraft as we know it today has largely been credited to Christopher Cockerell, a lateral thinker of his day who, after developing crucial components for use on British radar during the war, retired to a boatyard in Norfolk, where in the interest of making a faster powerboat that would plane at lower speeds came up with a similar idea to that of Thorneycroft; what goes around comes around!!! He took the idea further by the skilful use of vectored air to make the whole vehicle hover, thereby removing the drag from any part of the hull which might have been in contact with the surface, be it land or water. It is worth mentioning at this point that I do not think Cockerell ever intended his craft to be anything more than an amphibious marine vehicle. Where insurance underwriters and others get the idea that a hovercraft is some sort of low flying aeroplane says much about their lack of understanding of the concept. At a similar time in the late 1950's a Doctor William Bertelsen in the USA was looking at alternative forms of transport in order to reach his patients when the roads were impassable.

He continued to develop various hovering vehicles and roadways for hovercraft over the next 50 years. He is probably best known for the use of fans mounted on gimbals, but as with all things it is not necessarily the product, but the marketing of it, that makes the difference to its success or failure. In the case of Cockerell with his military contacts he was able to head up a British military development group, which with some time, reluctant government funding finally produced SRN1 which successfully crossed the Channel from England to France on the eleventh of June 1959, fifty years to the day after Bleriot did the same crossing in his aeroplane. As with all things if there is the possibility of a military use money is found to further development from which civilian side-products are often developed. The Russians built a fleet of very large military craft for use in the upper Baltic, particularly useful over the ice and snow, while the Americans were later to see the military advantages of hovercraft under the Reagan administration: when they did they invested heavily in both amphibious landing craft and rigid sidewall designs as the basis of their hundred miles an hour navy.

But as with most things political, the military investment is usually in proportion to the perceived threat, and as the USSR was coming apart at the seams the investment was reduced. But the US Navy now has a fleet of vastly powerful air cushion landing craft, which, with their mother-ships, are now an integral part of the US Marine structure. Some very successful craft that evolved from the military development work were used on civilian ferry designs, culminating in the large cross-Channel craft. The small or light [a British government definition of under one tonne] hovercraft of today were originally built, some of them by people in the commercial industry, but mainly by people inspired by the concept. Some of the early craft can be seen at the Hovercraft Museum at Lee-on-Solent. As one would expect many of the designs were scaled down versions of the larger commercial types of the day. Largely by virtue of the commercial industry being based around Southampton Water, the largest grouping of like-minded people was in that area and so the Hover [later Hovercraft] Club of Great Britain and the Hovercraft Society were formed.

At the Browndown hovercraft event in 1976, which took place on the 10th anniversary of the first Browndown event, Christopher Cockerell told me of the reluctance of his team to the idea of fitting "a ring of Mackintosh" around the SRN1 after its cross-Channel trip. In retrospect the comment is quite interesting because the use of a flexible seal or skirt was possibly the single most important step forward in making the hovercraft a practical transport vehicle, and secondly highlights the difficulty of working with a team of aircraft engineers trying to produce a marine product for military use. As the British Isles are a relatively small area making interaction between individuals relatively easy, it is not surprising to me that craft produced by the home-builder or small company rapidly evolved and have continued to do so long after the larger military/ commercial designs appeared to consolidate their basic idea's. A lot of time was taken up in the early development of the larger commercial craft in the improvement and refinement of the skirt. Companies such as Hovercraft Development Ltd [HDL] were specifically involved in making skirts more efficient, which gave the craft improved handling. This work made use of and added to the skirt patents, which were held by the British government.

Some development on propulsion systems was also noticeable. Again, in my view, commercially the breakthrough came when the industry stopped trying to make hovering aircraft with aero-engines etc, and started to make air-cushioned boats, both amphibious and non-amphibious [rigid-sidewall]. The rigid-sidewall craft were made using Glass Reinforced Plastic [GRP] technology for use where a shallow draught boat was required, or where there was a lot of water debris, in harbours etc. As these craft were normally diesel-powered driving both lift fans and water props, it was a natural progression to build diesel-powered amphibious hovercraft - e.g. the AP 188. This rather simplifies the case for the commercial development, but against the same period of 20 to 30 years the light hovercraft had gone from craft that would barely move to ones that could race in tight formation over land and water courses in groups up to 25 at the same time at speeds in excess of 50 miles an hour. On the light leisure/commercial side, craft are being used as viable forms of transport on a day-to-day basis, as well as for just plain fun.

At the same time development on small craft often being built with limited resources has been innovative in squeezing the best results out of the often limited materials available. When they were then used competitively or in groups it was inevitable that the better concepts prevailed. How do hovercraft work? - Explain that Stuff Tweet by Chris Woodford . Last updated: March 21, 2016. Is it a boat or a plane? Maybe it's a flying saucer? Back in 1959, when the world's first hovercraft, SR.N1, floated out across the windy English Channel, people must have wondered exactly what they were seeing. Like a boat, a hovercraft moves across water , but like a plane , it also pushes through the air with the help of propellers . The "big idea" is that a hovercraft can glide just as easily over water, land, or, ice. That makes it a perfect vehicle for getting round some of the world's most inaccessible areas—places where ordinary boats can't beach and planes can't land. How exactly does this unique and rather remarkable craft actually work? Let's take a closer look! Photo: A US Navy hovercraft (LCAC) photographed in 2008.

Picture by Chad R. Erdmann courtesy of US Navy . Much of the deck is empty space, suitable for carrying huge amounts of drive-on, drive-off military cargo. What is a hovercraft? One part boat , one part airplane , and one part helicopter a hovercraft is a vehicle that traps a cushion of air underneath itself and then floats along on top of it. The air cushion holds it high above waves and land obstructions, making the craft superbly amphibious (equally capable of traveling on land or water or gliding smoothly from one to the other). That's why military hovercraft, designed for swift beach landings, are often called LCACs (Landing Craft Air Cushion). Photo: A coastguard hovercraft photographed in 1971. Photo courtesy of NASA Ames Research Center (NASA-ARC) Hovercraft come in all shapes and sizes, from one-person fun machines and small beach rescue craft to giant passenger ferries capable of carrying over 400 passengers and 50 cars. Where boats are slowed by hulls that drag deep in the water, hovercraft ride fully clear, which means they use less fuel and can reach blistering speeds of up to 145kph (90mph).

From ice and water to mud and sand, from floodplains and river deltas to mangrove swamps and frozen glaciers, the great advantage of a hovercraft is that it can glide with ease to places ordinary boats struggle to reach, and land people safely even where there are no harbors or landing stages. In practice, hovercraft have four broad applications: large commercial hovercraft are mostly used as high-speed people and car ferries; slightly smaller military LCACs are used as tried-and-tested beach landing craft; smaller niche craft are used for things like oil and gas prospecting, inshore search and rescue, and scientific surveys; and small, one-person recreational craft are often raced round courses like flying go-karts! How does a hovercraft work? At first sight, you might think a hovercraft works in much the same way as a helicopter : it throws air down underneath itself and then simply rides along on top. But where a helicopter balances its own weight (the force of gravity pulling it down) with a massive down-draft of air (pushing it back up again), a hovercraft works in a much more subtle way that allows it to use far less air, far more efficiently, so getting by with a much smaller engine and considerably less fuel.

The basic mechanism of a hovercraft is very simple: there's an engine ( diesel or gasoline ) that powers both a large central fan, pointing downward, and one or more other fans pointing backward. The central fan creates the lift that holds the craft above the waves; the other fans propel the craft backward, forward, or to the side. A rubber skirt (with or without fingers) traps a cushion of air under the craft. Side-wall hovercraft have only partial skirts: with solid sides and a skirt only at the front and back, they can be powered by quieter propellers or water-jet engines, making them quieter. Photo: A typical hovercraft has two or more fans. The main fan in the center blows air downward to push the craft upward, above the water. Two or more other fans at the back blow air backward to make the craft go forward. This is an example of action-and-reaction ( Newton's third law of motion ) at work! How much can a hovercraft carry? A fan of a given power will create a certain amount of pressure under the craft.

Now since: pressure = force / area it follows that a bigger hovercraft (one with a bigger overall area) can carry more weight than a smaller hovercraft with a fan the same size. Moreover, as Christopher Cockerell, the inventor of the hovercraft, quickly discovered, bigger hovercraft are more efficient than smaller ones: "In such vehicles, the lift or load carrying capacity is proportional to the plan area of the gas cushion or cushions. The energy required to contain the cushion or cushions is proportional to the peripheral dimension of the cushion or cushions. Thus for an increase in size of a vehicle, the lift increases proportionally to the area of the cushion or cushions whilst the energy requirements increase linearly with the periphery of the cushion or cushions. The efficiency of a vehicle therefore increases with the plan area of the cushion or cushions, and hence with the plan area of the vehicle."—Christopher Cockerell, US Patent 3,177,960 , 1965.

Types of hovercrafts Now it's certainly possible to build a simple hovercraft with a giant fan that blows air down into a container of some kind (you'll find plenty on YouTube—a couple of them are linked in the references at the bottom of this article); that design is called an open plenum ("plenum" being another word for the hollow region underneath the craft where the air gathers). However, most hovercraft work in one of two other ways. The original hovercraft design used a vertically mounted fan to blow air between its outer shell and a slightly smaller inner container, creating what's called a "momentum curtain": a ring of fast-moving, inward-pointing air that trapped a bigger cushion of air inside it. This type of design is called a peripheral jet and its big advantage over an open plenum is that the fan needs to move much less air (or, to put it another way, it can create more lift with less power). Unfortunately, it still only produces a relatively modest hover height unless the fan is extremely powerful. Later, engineers discovered it was more effective (and efficient) to trap a much bigger air cushion with a rubber skirt that could flex around waves and other obstructions, giving a greater hover height and a better seal.

Hovercraft with skirts could clear bigger waves and land obstacles with no loss of stability or the all-important air cushion underneath them, so the ride was generally quite smooth. Eventually, the flexible skirt evolved into a more intricate design, with hundreds of independently moving "fingers" attached to the bottom that could maintain the airflow even more effectively. A modern hovercraft combines elements of the peripheral jet and flexible skirt designs by directing many jets of air inward through the skirt. Artwork: Hovercraft work in three main ways. Top: In an open-plenum design, the air effectively just pumps straight down under the craft. This requires a massive airflow and a very powerful engine. Middle: In Christopher Cockerell's peripheral jet design, a ring of fast-moving air, created by outer (peripheral) jets makes a "momentum curtain" that traps high pressure air inside it. The fan needs to move much less air to create the same lifting force, so it's a more efficient design than the open plenum. Right: Adding a skirt makes the air cushion higher, so the craft can safely clear bigger ocean waves and land obstacles. Skirts are either simple, flexible bags or more complex arrangements of individually moving segments called fingers.

Other important parts What else do you need to make a hovercraft? A downward-pointing fan can only blow air underneath, so hovercraft typically have one or more propeller fans on top of the hull, pointing backward to propel them forward. Usually, there's a rudder positioned just behind each fan to swivel the air it produces and steer the hovercraft in the appropriate direction. An alternative method of steering is to divert some of the down-draft from the fan through air nozzles that point horizontally—and the very first hovercraft prototype, SR.N1, effectively worked this way. Although hovercraft usually have separate fans (to create the cushion) and propellers (to drive them along), the same engines typically drive both, using gearboxes and transmissions to turn the engine's power through ninety degrees. Bigger hovercraft like the US military LCACs typically use several very hefty engines, such as powerful gas turbines. Then there's the hull itself. Most large hovercraft are built from light, rustproof, and highly durable aluminum , though hobby craft are often molded from tough composite materials such as fiber glass.

Finally, you need a cockpit to keep your pilot safe and sound—and some cargo space (either enclosed, for passengers and cars, or a large "open well" deck for carrying military cargo). Left: Close-up of a hovercraft skirt making a tight seal with the water beneath. Photo by Cody D. Lund courtesy of US Navy . Middle: Vertical rudders behind the fans steer the hovercraft by directing air to the side. Photo by Brian P. Biller courtesy of US Navy . Right: The fans are driven from engines in the side by giant axles . Photo by Christopher A Newsome courtesy of US Navy . Click the US Navy links to see further details and download hi-res versions of these photos. Advantages and disadvantages Hovercraft can launch and land anywhere, travel over almost any kind of surface, race along at high speeds, and efficiently carry large numbers of passengers and equipment or hefty military cargos. They compare favorably with all kinds of rival vehicles. Since they produce an air cushion more efficiently than a helicopter, they're cheaper to operate, simpler, and easier to maintain (safer too).

Where boats waste energy dragging through water and waves, a hovercraft riding smoothly on top creates little in the way of either drag or wake, so it's generally more efficient (and less disruptive to the marine environment than a propeller -driven ship). But if hovercraft are so wonderful, why aren't they used everywhere? They're expensive initially and, though cheaper than helicopters, considerably more costly to maintain than ships and boats of similar cargo capacity (because they're essentially aircraft, not boats, and mechanically more complex). Although hovercraft successfully carried tens of millions of people between Britain and France for just over 30 years, they eventually stopped operating following the opening of the Channel Tunnel and the arrival of low-cost ferry ships and fast, wave-piercing catamarans. Hovercraft are also fairly tricky to pilot: more like helicopters, in this respect, than simple-to-operate boats. They're very noisy too, which can be a problem both for passengers and people living near the ports where they operate, and is certainly a drawback for "covert" military operations. Who invented the hovercraft?

The basic idea behind the hovercraft can be traced back at least to the early 18th century: in 1716, Swedish philosopher Emmanuel Swedenborg (1688–1772) conceived a kind of overturned rowing boat in which each stroke of the oars pumped air under the hull, floating it happily over the waves. Unfortunately, it soon became obvious to Swedenborg that generating an air cushion by human muscle power wasn't going to work, so the craft was never built. In the 1870s, British marine engineer Sir John Thornycroft (1843–1928) figured out that a boat that could make an air cushion and carry it underneath itself would be able to avoid the problem of dragging its hull through the water. But his experiments to generate the cushion simply by pumping air with bellows were unsuccessful: technology was not on his side. It wasn't until the early 1950s that the theory of the hovercraft moved into practice, thanks to the work of another British engineer, Dr (and later "Sir") Christopher Cockerell (1910–1999).

Famously, he carried out an experiment with a coffee can and an empty tin of cat food, putting one inside the other to create an ring of empty space between them. Firing air from a blower down into this space from above, he found he could generate what he called the momentum curtain—a downward ring of high-pressure air that would effectively trap a much bigger cushion of air under a hovercraft, producing more lifting force for the same engine power. He measured the lift his "craft" produced using a simple pair of kitchen scales. Initially, Cockerell thought his idea would be of huge benefit to the military and offered it to the British government, who promptly classified it. Unfortunately for Cockerell, the military weren't that interested, and the "top secret" classification also prevented any further commercial development. In the late 1950s, the frustrated inventor managed to get his idea declassified again and, in 1959, formed the Hovercraft Development Company. With £150,000 backing (equivalent to several million dollars or pounds today) from a British government agency called the National Research Development Corporation (NRDC), he commissioned a full-scale prototype, which took eight months to build.

Constructed at Cowes on the Isle of Wight, England by a marine company called Saunders Roe, the SR.N1 (Saunders-Roe Navigation 1) was roughly the size of a small truck, but almost square (8.8m by 7.3m or 29ft by 24ft). Its most distinctive feature was a large, vertically mounted, white fan (powered by a 450 horsepower engine) that produced both the air cushion (by the peripheral jet principle) and steering (using directional channels that diverted some of the fan's airflow). On July 25 that year, Cockerell and pilot Peter Lamb took the SR.N1 across the English Channel (from England to France) in just over two hours, marking the 50th anniversary of Louis Bleriot's pioneering cross-channel airplane flight (but taking about 1.5 hours longer). Artwork: This early sketch of a hovercraft by Christopher Cockerell shows all the essential components of a modern machine—except the skirt, which he added later.

Following Cockerell's original numbering: 1 is the hovercraft itself; 2 is an opening at the front through which air enters; 3 is a double, four-bladed propeller; 4 is the engine; 5 is the drive shaft by which the engine powers the propeller; 6 is a chamber through which air flows; 7 is a tunnel into which air flows beneath the machine; 10 is the cockpit; 11 is the cargo bay; 12 are the bay doors; and 14 is the steering rudder at the back. Artwork from US Patent #3,363,716: Vehicles for travelling over land and/or water by Christopher Cockerell, filed on 12 December 1956 and granted on 16 January 1968. Courtesy of US Patent and Trademark Office. Although Cockerell and his engineers continued to tinker with the design of the SR.N1 and made small improvements, the next big advance came with the development of the flexible skirt, invented by British aircraft engineer Cecil Latimer-Needham (1900–1975).

Thanks to this innovation, the SR.N1 prototype was soon superseded by much bigger and more practical craft. The first commercial passenger hovercraft service began in 1962, with a Vickers-Armstrong VA3 operating between Rhyl in North Wales and Merseyside, England carrying 24 passengers at up to 110kph (70mph). By 1968, technology had advanced to the point where Saunders Roe could build two giant, cross-channel, SR.N4 hovercraft ferries. These huge machines successfully ferried tens of millions of people from England to France until 2000, when the service was closed for good. Although Britain pioneered the hovercraft, the only passenger service now operating in the UK is a relatively modest ferry shuttling passengers from Portsmouth on the English mainland to the nearby Isle of Wight (fittingly, the island where hovercraft first buzzed into life). Even so, hovercraft continue to be widely used by military forces throughout the world, and in all kinds of niche applications where they outperform boats and helicopters. Hover Club of America : An organization for recreational hovercraft enthusiasts.

News articles Hovercraft still afloat 50 years on by Brian Milligan, BBC News, 10 June 2009. A news report celebrating 50 years of the hovercraft, with video footage of early hovercraft experiments. It's a Boat! It'a Plane! It's a... Hovercraft! by Steven Zeitchik. The New York Times, 23 April 2004. The growing amateur enthusiasm for hovercraft. Hovercraft genius dies BBC News, 3 June 1999. An obituary for hovercraft inventor Sir Christopher Cockerell. Books The Hovercraft: A History by Ashley Hollebone. The History Press, 2012. Ships and submarines by Chris Woodford. Facts on File, 2004. My own book about the history of ships, from ancient wooden craft to the very latest wave-piercing catamarans. Discover the Hovercraft by Kevin Jackson. Flexitech, 2004. This short, hands-on book about hovercraft technology includes experiments and activities you can try.

Videos Everyone By Hovercraft : Christopher Cockerell demonstrates some of his designs in this 1964 Pathe News clip. Styrofoam tray hovercraft : A simple-to-build hovercraft model you can make in perhaps an hour or less. Patents If you're looking for more technical explanations, patents are always a good place to start. Here are four of Christopher Cokerell's pioneering designs: US Patent #3,363,716: Vehicles for travelling over land and/or water by Christopher Cockerell, granted 16 January 1968. This appears to be the first US patent Cockerell filed (in 1956), though it wasn't published until 1968 (after the patents listed below). Sir Christopher Cockerell - Telegraph Obituaries Sir Christopher Cockerell Sir Christopher Cockerell, who has died aged 88, invented the hovercraft, the vehicle which can travel across land or water on a cushion of air. Cockerell was one of Britain's most original scientific minds and had a string of inventions to his credit.

Photo: REX Comments However, the problems he experienced in getting his ideas taken seriously, and the paucity of the financial rewards that came his way, meant that he also symbolised Britain's recent failure to exploit the commercial potential of its inventions. When, in the early 1950s, Cockerell began to consider the possibility of travel by hovercraft, he was living in a caravan by Oulton Broad in Norfolk. He had recently resigned from a job with the electronics company Marconi, and, as sailing was his hobby, had taken over a run-down boatyard where he went into business turning out cabin cruisers for holidaymakers. But he had a restless mind and found that he could not leave boat design as it was. He began to wonder how friction might be reduced between hull and water to make a boat go faster. He came up with the idea that a heavy craft could be supported on a cushion of air produced by a relatively small amount of thrust. Using a can of cat food inside a coffee tin and reversed air-flow from a vacuum cleaner, he proved that his theory was correct on the mud floor of his boatyard.

Cockerell was not the first man to think of the idea; for 50 years inventors had tried to build vehicles capable of riding on air, but they had always hit technical snags, partly because they had not been able to devise an effective means of holding the air cushion in place. It was Cockerell who had the idea of keeping it in place with a ring of higher pressure air around the periphery. By the middle of 1955, he had tested his idea as far as he could and began to look around for an investor to help him turn it into a commercial proposition. A year later he had managed only to amass a pile of correspondence marked "Unsuccessful''. Related Articles John Duckworth, physicist 04 Feb 2015 He decided that he needed a working model and, with the help of a neighbouring boat builder, built one that was 2 ft in diameter. This he kept tethered to a stake on the lawn, occasionally testing its waterborne capacity by flying it on the end of a string while he sat in his boat.

Next, realising it was his duty to inform the Government about any new development with a potential military value, he took the completed model to London and sent it hovering at the end of a leash across the basement floor of the Ministry of Supply; this sent one senior official leaping on to a chair for safety. The upshot was that Cockerell's invention was immediately classified "Secret''. Nothing further happened for another year, however, by which time Cockerell was so hard up that he was forced to raise money by pawning his mother-in-law's engagement ring. Then, in 1957, Cockerell learned that the Swiss were developing a similar idea with a view to commercial exploitation. Armed with this information, he persuaded the Ministry to allow him to approach the National Research and Development Corporation (NRDC), the Government-funded body charged with fostering promising inventions. Within a day, the NRDC had committed the princely sum of £1,000, with a gentlemen's agreement that they should have first refusal on any development rights.

In 1959, after the Ministry of Supply had agreed that the idea could be released for commercial as well as military development, the NRDC formed a subsidiary, Hovercraft Development Limited (HDL). Its remit was to control the project, organise development and bring in private investment. Cockerell became a director and technical consultant to HDL, which took over his patents and licensed five firms to build hovercraft. To Saunders Roe (later part of Westland) went the contract to build the first prototype. This one-man vehicle, the SR-N1, crossed the English Channel for the first time in June 1959. The success of the SR-N1 led to a proliferation of types and designs. The Armed Services began to see the potential of the new technology and formed a Hovercraft Trials Unit at Lee-on-the- Solent. In 1961, the 68-seat SR-N2 crossed the Channel in 20 minutes. In early 1962, it was discovered that a flexible skirt of rubber was a more efficient container of the air cushion than high-pressure down-ward jets of air.

In June 1962, Vickers opened the first commercial hovercraft service across the estuary of the river Dee. Commercial cross-Channel services began in 1966. There were high hopes that the hovercraft would become a shop window for British technology. Yet from the start the project was dogged by a shortage of private investors. What investment there was came from the Government via the NRDC, which between 1961 and 1964 committed £750,000 to the project. As a result, though Britain still retained a lead, rivals in other countries were catching up. In 1966, NRDC decided to amalgamate the companies involved in British hovercraft production into the British Hovercraft Corporation. Cockerell, who believed competition should be encouraged, opposed the decision on the grounds that it would "stultify the hovercraft industry in Britain''. But his protests were to no avail and the same year he resigned in protest from the board of HDL. Cockerell's resignation sparked a fierce debate about Britain's industrial strategy and its treatment of inventors.

Some years later, he revealed that he had had to fight for 12 years to be given £150,000 for his patents, and claimed never to have recovered his first six years' development costs. During the 1980s, after a court case, the American government agreed to pay £3.7m in royalties to the British Technology Group (the successor to NRDC) for the rights to develop hovercraft for military use. However, Cockerell's request for a share of the proceeds was brusquely dismissed. "Why should the US have had the advantage of my ideas?'' Cockerell demanded. "It seems as if I have been working for nothing.'' After Cockerell's resignation, the hovercraft continued to be plagued by high costs of development and design, and in operation was dogged by technical problems and accidents, including fires, loose propellers, engine failure, gale damage and even a fatal accident at Dover in 1985 which claimed the lives of four passengers. By 1994, only two British-built hovercraft remained in service on cross-Channel routes.

As a result, the hovercraft never fulfilled the hopes of its inventor that it would become widely used in commercial service. Cockerell was an intensely pat- riotic man. Despite the poor rewards for his work in Britain, he refused offers of jobs with American competitors. He remained angry at Britain's failure to capitalise on new ideas, a failure he blamed on an education system which "produces engineers who are quite unsuitable for positions of influence, and managers who can do no better than stagger through our highly technological age''. "What our political parties should be spelling out,'' he argued in 1996, "is not different ways of dividing up the national cake, but how to make it bigger so we can all benefit. Our approach to inventions is a serious detriment to the country. People think there aren't more inventions to invent, but there are.'' Christopher Sydney Cockerell was born on June 4 1910 in Cambridge where his father, Sir Sydney Cockerell, was Curator of the Fitzwilliam Museum. Though father and son later became close, their early relationship was difficult.

The Cockerell home was forever filled with distinguished men of letters, but young Christopher preferred to investigate the workings of his mother's sewing machine than to listen to Hardy, Conrad or Shaw holding forth in the drawing room. When T E Lawrence came to stay, Christopher was only interested in Lawrence's 1,000 cc Brough Superior motorcycle. The boy, said his father, was "no better than a garage hand''. "My father was brilliantly half-educated,'' observed his son, "and I was half-educated too; but we were educated in entirely different halves''. Christopher went to Gresham's School, Holt, in Norfolk, where he was a contemporary of WH Auden and the future spy Donald Maclean, but he failed to distinguish himself academically. It was only by dint of determined cramming that he managed to scrape a place at Peterhouse, Cambridge, to study engineering. In 1935 he started working on research and development of airborne and navigational equipment for Marconi. His father, by now reconciled to his son's chosen career, promised him £10 each time that he had an idea patented. "I soon had to stop,'' Sir Sydney later recalled.

"I was up to £100 in no time because Christopher was inventing things so quickly. He was not called up in the war because his work was so important''. Cockerell's first notable invention for Marconi was a two-needle aerial direction finder, nicknamed "the drunken men'', a device which during the Second World War brought safely home thousands of Allied airmen. Altogether, Cockerell devised 36 inventions for Marconi, worth millions of pounds, for each of which he was paid £10 by the firm. Cockerell continued to work as an inventor after his resignation from HDL. During the 1970s he designed the Cockerell Raft, a system of linked rafts powered by water, which were designed to use the energy of sea waves to pro- duce electricity. He founded a company, Wavepower Limited, to develop the idea, winning a £150,000 research grant from the Government. A keen gardener and fisherman, lately he had lived at Hythe, in Hampshire. Christopher Cockerell became a Fellow of the Royal Society in 1967.

He was appointed CBE in 1966 and knighted in 1969. He married, in 1937, Elinor Bel- sham; she died in 1996. They had two daughters.

Question: Which boat builder invented the hovercraft in 1956?
Answer: Christopher Cockerel