Hovertrain
Encyclopedia
A hovertrain is a type of high-speed train that replaces conventional steel wheels with hovercraft
lift pads, and the conventional railway bed with a paved road-like surface, known as the "track" or "guideway". The concept aims to eliminate rolling resistance
and allow very high performance, while also simplifying the infrastructure needed to lay new lines.
Hovertrains were seen as a relatively low-risk and low-cost way to develop high-speed inter-city train service, in an era when conventional rail seemed stuck to speeds around 140 mph or less. By the late 1960s, major development efforts were underway in France, the UK and the USA. While they were being developed, British Rail
was running an extensive study of the problems being seen at high speeds on conventional rails. This led to a series of new high-speed train designs in the 1970s, starting with their own APT
. Although the hovertrains still had reduced infrastructure costs compared to the APT and similar designs like the TGV
, in practice this was offset by the fact that they needed entirely new lines. Conventional wheeled trains could run at low speed on existing lines, greatly reducing capital expenditures in dense areas. Interest in hovertrains waned, and major development had ended by the mid-1970s.
Hovertrains were also developed for smaller systems, including personal rapid transit
systems that were a hot topic in the late 1960s and early 1970s. In this role their ability to float over small imperfections and debris on the "rails" was a practical advantage, although it competed with the maglev
concept that had the same advantages. The only hovertain to see commercial service was the Otis Hovair
system. Originally developed at General Motors
as an automated guideway transit
system, GM was forced to divest the design as part of an anti-trust ruling. The design eventually ended up at Otis Elevator who later replaced its linear motor
with a cable pull and sold the resulting design for people mover
installations all over the world.
Hovertrain is a generic term, and the vehicles are more commonly referred to by the projects that developed them in different countries – in the UK they are known as tracked hovercraft, in the US they are tracked air-cushion vehicles, and in France they are the aerotrains. News sources often conflate maglev
trains with hovertrains, as both are levitated above the running surface, "hovering" over them.
At high speeds, trains suffer from a form of instability known as "hunting oscillation
" that forces the flanges on the sides of the wheels to hit the sides of the rails, as if they were rounding a tight bend. At speeds of 140 mph or over, the frequency of these hits increased to the point where they became a major form of drag, dramatically increasing rolling resistance and potentially causing a derailment. That meant that for travel above some critical speed, a hovercraft could be more efficient than a wheeled vehicle of the same weight.
Better yet, such a vehicle would also retain all of the positive qualities of a hovercraft. Small imperfections in the surface would have no effect on the ride quality, so the complexity of the suspension system could be reduced. Additionally, since the load is spread out over the surface of the lifting pads, often the entire underside of the vehicle, the pressure on the running surface is greatly reduced – about 1/10000 th the pressure of a train wheel, about 1/20 th of the pressure of a tire on a road.
These two properties meant that the running surface could be considerably simpler than the surface needed to support the same vehicle on wheels; hovertrains could be supported on surfaces similar to existing light-duty roadways, instead of the much more complex and expensive railbeds needed for conventional trains. This could dramatically reduce infrastructure capital costs of building new lines and offer a path to widespread use of high-speed trains.
. The Levapad required extremely flat surfaces to work on, either metal plates, or as originally intended, the very smooth concrete of a factory floor. Kucher eventually became VP in charge of the Ford Scientific Laboratory, continuing development of the Levapad concept throughout.
It does not appear any effort was put into vehicle use until the 1950s, when several efforts used Levapad-like arrangements running on conventional rails as a way to avoid the hunting problems and provide high-speed service. A 1958 article in Modern Mechanix is one of the first popular introductions of the Levapad concept. The article focuses on cars, based on Ford's prototype "Glideair" vehicle, but quotes Kucher noting "We look upon Glideair as a new form of high-speed land transportation, probably in the field of rail surface travel, for fast trips of distances of up to about 1,000 miles". A 1960 Popular Mechanics
article notes a number of different groups proposing a hovertrain concept.
What was lacking from all of them was a suitable way to move the vehicles forward – since the whole idea of the hovertrain concept was to eliminate any physical contact with the running surface, especially wheels, some sort of contact-less thrust would have to be provided. There were various proposals using air ducted from the lift fans, propeller, or even jet engine
s, but none of these could approach the efficiency of an electric motor
powering a wheel.
was building the first practical linear induction motor
s (LIMs), which, prior to his efforts, had been limited to "toy" systems. A LIM can be built in several different ways, but in its simplest form it consists of an active portion on the vehicle corresponding to the windings on a conventional motor, and a simple metal plate acting as the stator. When the windings are energized, the magnetic field
they produce causes an opposite field to be induced
in the plate, after a short delay due to hysteresis
.
By carefully timing the energizing of the windings, the fields in the windings and "reaction rail" will be slightly offset due to the hysteresis. That offset results in a net thrust along the reaction rail, allowing the LIM to pull itself along the rail without any physical contact. The LIM concept sparked considerable interest in the transportation world, as it offered a way to make an electric motor with no moving parts, which could greatly reduce maintenance needs.
Laithwaite suggested that the LIM would be a perfect fit for high speed transport, and built a model consisting of a chair mounted on a four-wheeled chassis on rails with a LIM rail running down the middle. After successful demonstrations, he convinced British Rail
(BR) to invest in some experimental work using a LIM to power a train on rails using small lift pads similar to the Levipad system for suspension.
's group, organized in Hythe, Kent
as Hovercraft Development Ltd. As early as 1960 their engineers were experimenting with the hovertrain concept, and by 1963 had developed a test-bed system about the size of a tractor-trailer that ran for short distances on a concrete pad with a central vertical surface that provided directional control. The prototype was pushed along its short test track by hand.
The group at Hovercraft Development applied the LIM concept to their hovertrain almost immediately after the LIM became well known around 1961. By the time the prototype was running in 1963, they had been promoting the idea of using a LIM with their suspension as the basis for a full-sized development. A small model of their proposal shows a train that looks like the fuselage of a narrow-body airliner running on a monorail
track shaped like an upside-down "T". The horizontal portion provided the running surface, while the vertical provided directional tracking and the structure for mounting the reaction rail.
The team secured some additional funding for the construction of a scale-model system. This was built in the yard of the Hythe site, consisting of a large loop of track about three feet off the ground. By this point the basic layout had changed, with the guideway now in the form of a box girder, with the vertical pads on the sides of the guideway rather than a separate vertical surface on top of it. The vehicle itself was now flatter and wider. This version was running in 1965 and shown publicly the next year at Hovershow '66. A later modification would move the LIM rail from the top to the side of the guideway.
At this point the project entered hiatus for lack of funding. During this same period, British Rail was working on an extensive study project that was suggesting that the hunting problems seen on existing trains could be addressed through development of suitable suspension systems. BR lost interest in the hovertrain concept, and moved on to their Advanced Passenger Train
(APT) efforts shortly thereafter. In the meantime, the Hythe team had no funds for the full-scale test system they were proposing, and complained at Hovershow that the French would be taking the lead in hovertrain development.
In 1967, the government handed control of Hovercraft Development to the National Physical Laboratory. At almost exactly the same time, Laithwaite severed his ties with BR. The two teams joined forces, re-organizing as Tracked Hovercraft
to continue efforts to build a full-scale prototype. A combination of factors, including Laithwaite's persuasiveness and Bertin's successes in France, quickly gained the company government funding.
Construction of a test track started north of London in 1970. The location was chosen in a flat area that could allow up to 20 miles of track to be laid, although funds only covered the first 4 mile section. Rising costs further limited this to a short 1 mile section. The prototype vehicle, RVT 31, started speed tests in 1973, in February it managed to reach 104 mph in a 20 mph headwind.
In spite of this success, two weeks later the government cancelled further funding. A combination of the total lack of interest on BR's part, and infighting between the various high-speed efforts, prompted the formation of an independent review board that heavily favored APT. The test track was later removed and RTV 31 ended up in a museum.
Jean Bertin was an early advocate of the hovercraft, and had built a series of multi-skirt transport vehicles for the French army known as the "Terraplane" in the early 1960s. In 1963, he showed a model of a vehicle similar to the early Hovercraft Development concepts to SNCF
. Like BR, SNCF was actively exploring high-speed train service. The public demonstration of the Hovercraft Development system appears to have sparked their interest, and they started funding Bertin's efforts to develop what he called the "Aérotrain
".
Lacking the engineering know-how in the nascent LIM field, Bertin's early designs used propellers. Through 1964 the team built a 1/2 scale model of a small hovertrain, and a 3 km long track to test it on. On 29 December 1965 the prototype was first placed on its upside-down T-shaped track, and on 26 March 1966 it reached 202 km/h. Higher speeds could not be reached with a propeller on the short test track, so the engineers equipped the vehicle with small rockets and in December it reached 303 km/h. This success garnered funding for the addition of a Turbomeca Marboré
turbojet engine taken from a Fouga Magister
, which powered it to 345 km/h on 1 November 1967.
Several newer prototypes of ever-larger size followed, culminating in the I-80, a 44-seat vehicle powered by two turboshaft
engines driving a single shrouded propeller. An 18 km long test track outside of Chevilly was built to test it, where it arrived on 10 September 1969. Two days later it reached 200 km/h, and the day after that 250 km/h, it's design speed. For additional boost a jet engine was added, powering it to 400 km/h in October 1973, peaking at 430 km/h on 5 March 1974, a world record to this day. At the same time, Bertin started exploring the LIM for a lower-speed suburban vehicle, building a prototype known as the S44.
Like their UK counterparts, the seeds of the Aérotrain's demise were already being sown by their counterparts at the national railway. In 1966, other SNCF engineers had made the first proposals for higher speed conventional railways, a proposal that would take on a life of its own and evolve into the TGV
program. Like the Tracked Hovercraft and APT, the Aérotrain project soon found itself fighting with the TGV for future development. Unlike the UK work, however, the Aérotrain had stronger political backing, and did not suffer from the same lack of funding as its British counterpart.
Several development proposals were offered and hotly debated both within SNCF and the government. After many proposals, on 21 June 1974 SNCF signed a contract for an Aérotrain line between Le Défense and Cergy, on the northwestern side of Paris. On 17 July the contract was annulled. The September 1975 Paris-Lyon TGV line was the deathblow to the project, although small-scale work continued until 1977.
In December 1969, the DOT selected and purchased a large parcel of land outside Pueblo, Colorado
, and built the High Speed Ground Test Center (HSGTC) for the various programs. For the TACV program, DOT paid for the construction of the test track loops for the different prototypes. However, track construction proceeded slowly.
built the Linear Induction Motor Research Vehicle (LIMRV), a wheeled vehicle running on standard-gauge railroad track, fitted with a 3000 hp gas turbine
generator to supply the LIM with electricity.
The test track for the LIMRV at the HSGTC near Pueblo wasn't yet complete when Garrett delivered the vehicle: the reaction rail in the middle of the tracks was still being installed. Once the track was ready, linear induction motor, vehicle power systems, and rail dynamics testing progressed and by October 1972, a speed of 187.9 mph (302.4 km/h) was achieved. Speed was limited due to the length of track (6.4 miles) and vehicle acceleration rates. Two J-52 engines were added to the vehicle to propel the vehicle up to higher speeds. These engines were then throttled back so that the thrust of the J-52's equaled their drag. This allowed higher speed testing without building several miles of additional track. On August 14, 1974, the LIMRV achieved a world record speed of 255.7 mph (411.5 km/h) for vehicles on conventional rail.
and Grumman proposed designs, with the Grumman vehicle being given the go-ahead. Grumman's TACRV was presented in 1972. Although Grumman's efforts got the majority of the funding in the TACV project, ensuring the construction of 22 miles (35 km) of track, the reaction rails for the LIM propulsion were never installed. With jet engine propulsion only, no more than 90 mph (145 km/h) was achieved.
However, there was almost no money left over, so the Rohr vehicle received only 1.5 miles (2.4 km) of track, on which a maximum of only 145 mph (233 km/h) was possible. By the time the UTACV was ready for testing, most of the budget had already been used up, and no further funds were forthcoming. The need for an electricity supply system, low energy efficiency, and noise levels were seen as problems. The last tests of the Rohr vehicle ended in October 1975. Since then the Pueblo facility has been used for testing conventional trains to this day, now known as the Transportation Technology Center
.
As electronics improved, and electrical control systems with them, it became increasingly easy to build an "active track" using electromagnets. By the late 1960s there was renewed interest in the maglev concept, and several study projects were starting in Germany and Japan. Through the same period, Laithwaite had invented a new form of the LIM that provided both lift and forward thrust, and could be built over an passive track like the conventional LIMs. In either case, only magnets in the immediate vicinity of the train would have to be turned on, which appeared to offer much lower overall energy needs than the hovertrain.
By the early 1970s, a wide variety of new maglev proposals were being actively worked on around the world. The German government, in particular, was funding several different passive and active systems in order to explore which of the proposed solutions made the most sense. By the mid 1970s, several of these projects had progressed to about the same point as the hovertrains, yet appeared to have none of their disadvantages—high sound levels, blown dirt and higher energy use than initially expected.
Although the existing projects, mentioned above, continued on using their existing funding, the lack of further funding is best understood as due to both the rising interest in maglev by some teams and the introduction of high-speed conventional trains by others.
Hovercraft
A hovercraft is a craft capable of traveling over surfaces while supported by a cushion of slow moving, high-pressure air which is ejected against the surface below and contained within a "skirt." Although supported by air, a hovercraft is not considered an aircraft.Hovercraft are used throughout...
lift pads, and the conventional railway bed with a paved road-like surface, known as the "track" or "guideway". The concept aims to eliminate rolling resistance
Rolling resistance
Rolling resistance, sometimes called rolling friction or rolling drag, is the resistance that occurs when a round object such as a ball or tire rolls on a flat surface, in steady velocity straight line motion. It is caused mainly by the deformation of the object, the deformation of the surface, or...
and allow very high performance, while also simplifying the infrastructure needed to lay new lines.
Hovertrains were seen as a relatively low-risk and low-cost way to develop high-speed inter-city train service, in an era when conventional rail seemed stuck to speeds around 140 mph or less. By the late 1960s, major development efforts were underway in France, the UK and the USA. While they were being developed, British Rail
British Rail
British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...
was running an extensive study of the problems being seen at high speeds on conventional rails. This led to a series of new high-speed train designs in the 1970s, starting with their own APT
Advanced Passenger Train
The Advanced Passenger Train was an experimental tilting High Speed Train developed by British Rail during the 1970s and early 1980s....
. Although the hovertrains still had reduced infrastructure costs compared to the APT and similar designs like the TGV
TGV
The TGV is France's high-speed rail service, currently operated by SNCF Voyages, the long-distance rail branch of SNCF, the French national rail operator....
, in practice this was offset by the fact that they needed entirely new lines. Conventional wheeled trains could run at low speed on existing lines, greatly reducing capital expenditures in dense areas. Interest in hovertrains waned, and major development had ended by the mid-1970s.
Hovertrains were also developed for smaller systems, including personal rapid transit
Personal rapid transit
Personal rapid transit , also called podcar, is a public transportation mode featuring small automated vehicles operating on a network of specially built guide ways...
systems that were a hot topic in the late 1960s and early 1970s. In this role their ability to float over small imperfections and debris on the "rails" was a practical advantage, although it competed with the maglev
Maglev
Maglev is a form of rail transport using magnetic levitation.Maglev may also refer to:* Magnetic levitation, a method by which an object is suspended using magnetic fields* MagLev , a virtual machine for the Ruby programming language...
concept that had the same advantages. The only hovertain to see commercial service was the Otis Hovair
Otis Hovair
Otis Hovair Transit Systems is a type of Hovertrain that replaces conventional steel wheels with hovercraft lift pads, and the conventional railway bed with a paved road-like surface, known as the "track" or "guideway". The concept aims to eliminate rolling resistance and allow very high...
system. Originally developed at General Motors
General Motors
General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...
as an automated guideway transit
Automated guideway transit
Automated guideway transit is a fully automated, driverless, grade-separated transit system in which vehicles are automatically guided along a "guideway". The vehicles are often rubber tired, but other systems including steel wheels, air cushion and maglev systems have also been used in experiments...
system, GM was forced to divest the design as part of an anti-trust ruling. The design eventually ended up at Otis Elevator who later replaced its linear motor
Linear motor
A linear motor is an electric motor that has had its stator and rotor "unrolled" so that instead of producing a torque it produces a linear force along its length...
with a cable pull and sold the resulting design for people mover
People mover
A people mover or automated people mover is a fully automated, grade-separated mass transit system.The term is generally used only to describe systems serving relatively small areas such as airports, downtown districts or theme parks, but is sometimes applied to considerably more complex automated...
installations all over the world.
Hovertrain is a generic term, and the vehicles are more commonly referred to by the projects that developed them in different countries – in the UK they are known as tracked hovercraft, in the US they are tracked air-cushion vehicles, and in France they are the aerotrains. News sources often conflate maglev
Maglev
Maglev is a form of rail transport using magnetic levitation.Maglev may also refer to:* Magnetic levitation, a method by which an object is suspended using magnetic fields* MagLev , a virtual machine for the Ruby programming language...
trains with hovertrains, as both are levitated above the running surface, "hovering" over them.
Basic concept
It was noticed early on that the energy needed to lift a hovercraft was directly related to the smoothness of the surface it traveled on. This was not surprising; the air trapped under the hovercraft's skirt will remain there except where it leaks out around the bottom of the skirt where it contacts the ground – if this interface is smooth, the amount of leaked air will be low. What was surprising was that the amount of energy lost through this process could be lower than steel wheeled vehicles, at least at high speeds.At high speeds, trains suffer from a form of instability known as "hunting oscillation
Hunting oscillation
Hunting oscillation is an oscillation, usually unwanted, about an equilibrium. The expression came into use in the 19th century and describes how a systems 'hunts' for equilibrium...
" that forces the flanges on the sides of the wheels to hit the sides of the rails, as if they were rounding a tight bend. At speeds of 140 mph or over, the frequency of these hits increased to the point where they became a major form of drag, dramatically increasing rolling resistance and potentially causing a derailment. That meant that for travel above some critical speed, a hovercraft could be more efficient than a wheeled vehicle of the same weight.
Better yet, such a vehicle would also retain all of the positive qualities of a hovercraft. Small imperfections in the surface would have no effect on the ride quality, so the complexity of the suspension system could be reduced. Additionally, since the load is spread out over the surface of the lifting pads, often the entire underside of the vehicle, the pressure on the running surface is greatly reduced – about 1/10000 th the pressure of a train wheel, about 1/20 th of the pressure of a tire on a road.
These two properties meant that the running surface could be considerably simpler than the surface needed to support the same vehicle on wheels; hovertrains could be supported on surfaces similar to existing light-duty roadways, instead of the much more complex and expensive railbeds needed for conventional trains. This could dramatically reduce infrastructure capital costs of building new lines and offer a path to widespread use of high-speed trains.
Early efforts
One of the earliest hovertrain concepts predates hovercraft by decades; in the early 1930s Andrew Kucher, an engineer at Ford, came up with the idea of using compressed air to provide lift as a form of lubrication. This led to the Levapad concept, where compressed air was blown out of small metal disks, shaped much like a poppet valvePoppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
. The Levapad required extremely flat surfaces to work on, either metal plates, or as originally intended, the very smooth concrete of a factory floor. Kucher eventually became VP in charge of the Ford Scientific Laboratory, continuing development of the Levapad concept throughout.
It does not appear any effort was put into vehicle use until the 1950s, when several efforts used Levapad-like arrangements running on conventional rails as a way to avoid the hunting problems and provide high-speed service. A 1958 article in Modern Mechanix is one of the first popular introductions of the Levapad concept. The article focuses on cars, based on Ford's prototype "Glideair" vehicle, but quotes Kucher noting "We look upon Glideair as a new form of high-speed land transportation, probably in the field of rail surface travel, for fast trips of distances of up to about 1,000 miles". A 1960 Popular Mechanics
Popular Mechanics
Popular Mechanics is an American magazine first published January 11, 1902 by H. H. Windsor, and has been owned since 1958 by the Hearst Corporation...
article notes a number of different groups proposing a hovertrain concept.
What was lacking from all of them was a suitable way to move the vehicles forward – since the whole idea of the hovertrain concept was to eliminate any physical contact with the running surface, especially wheels, some sort of contact-less thrust would have to be provided. There were various proposals using air ducted from the lift fans, propeller, or even jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
s, but none of these could approach the efficiency of an electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
powering a wheel.
LIM
At about the same time, Eric LaithwaiteEric Laithwaite
Eric Roberts Laithwaite was a British electrical engineer, known as the "Father of Maglev" for his development of the linear induction motor and maglev rail system.- Biography :...
was building the first practical linear induction motor
Linear induction motor
A linear induction motor is an AC asynchronous linear motor that works by the same general principles as other induction motors but which has been designed to directly produce motion in a straight line....
s (LIMs), which, prior to his efforts, had been limited to "toy" systems. A LIM can be built in several different ways, but in its simplest form it consists of an active portion on the vehicle corresponding to the windings on a conventional motor, and a simple metal plate acting as the stator. When the windings are energized, the magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
they produce causes an opposite field to be induced
Magnetic induction
Magnetic induction may refer to one of the following:* Electromagnetic induction* Magnetic field B is sometimes called magnetic induction...
in the plate, after a short delay due to hysteresis
Hysteresis
Hysteresis is the dependence of a system not just on its current environment but also on its past. This dependence arises because the system can be in more than one internal state. To predict its future evolution, either its internal state or its history must be known. If a given input alternately...
.
By carefully timing the energizing of the windings, the fields in the windings and "reaction rail" will be slightly offset due to the hysteresis. That offset results in a net thrust along the reaction rail, allowing the LIM to pull itself along the rail without any physical contact. The LIM concept sparked considerable interest in the transportation world, as it offered a way to make an electric motor with no moving parts, which could greatly reduce maintenance needs.
Laithwaite suggested that the LIM would be a perfect fit for high speed transport, and built a model consisting of a chair mounted on a four-wheeled chassis on rails with a LIM rail running down the middle. After successful demonstrations, he convinced British Rail
British Rail
British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...
(BR) to invest in some experimental work using a LIM to power a train on rails using small lift pads similar to the Levipad system for suspension.
Tracked Hovercraft
The earliest examples of serious hovertrain proposals come, unsurprisingly, from Christopher CockerellChristopher Cockerell
Sir Christopher Sydney Cockerell CBE FRS was an English engineer, inventor of the hovercraft.-Life:Cockerell was born in Cambridge, where his father, Sir Sydney Cockerell, was curator of the Fitzwilliam Museum, having previously been the secretary of William Morris. Christopher Cockerell was...
's group, organized in Hythe, Kent
Hythe, Kent
Hythe , is a small coastal market town on the edge of Romney Marsh, in the District of Shepway on the south coast of Kent. The word Hythe or Hithe is an Old English word meaning Haven or Landing Place....
as Hovercraft Development Ltd. As early as 1960 their engineers were experimenting with the hovertrain concept, and by 1963 had developed a test-bed system about the size of a tractor-trailer that ran for short distances on a concrete pad with a central vertical surface that provided directional control. The prototype was pushed along its short test track by hand.
The group at Hovercraft Development applied the LIM concept to their hovertrain almost immediately after the LIM became well known around 1961. By the time the prototype was running in 1963, they had been promoting the idea of using a LIM with their suspension as the basis for a full-sized development. A small model of their proposal shows a train that looks like the fuselage of a narrow-body airliner running on a monorail
Monorail
A monorail is a rail-based transportation system based on a single rail, which acts as its sole support and its guideway. The term is also used variously to describe the beam of the system, or the vehicles traveling on such a beam or track...
track shaped like an upside-down "T". The horizontal portion provided the running surface, while the vertical provided directional tracking and the structure for mounting the reaction rail.
The team secured some additional funding for the construction of a scale-model system. This was built in the yard of the Hythe site, consisting of a large loop of track about three feet off the ground. By this point the basic layout had changed, with the guideway now in the form of a box girder, with the vertical pads on the sides of the guideway rather than a separate vertical surface on top of it. The vehicle itself was now flatter and wider. This version was running in 1965 and shown publicly the next year at Hovershow '66. A later modification would move the LIM rail from the top to the side of the guideway.
At this point the project entered hiatus for lack of funding. During this same period, British Rail was working on an extensive study project that was suggesting that the hunting problems seen on existing trains could be addressed through development of suitable suspension systems. BR lost interest in the hovertrain concept, and moved on to their Advanced Passenger Train
Advanced Passenger Train
The Advanced Passenger Train was an experimental tilting High Speed Train developed by British Rail during the 1970s and early 1980s....
(APT) efforts shortly thereafter. In the meantime, the Hythe team had no funds for the full-scale test system they were proposing, and complained at Hovershow that the French would be taking the lead in hovertrain development.
In 1967, the government handed control of Hovercraft Development to the National Physical Laboratory. At almost exactly the same time, Laithwaite severed his ties with BR. The two teams joined forces, re-organizing as Tracked Hovercraft
Tracked Hovercraft
Tracked Hovercraft was an experimental high speed train developed in the United Kingdom during the 1960s. It combined two British inventions, the hovercraft and linear induction motor, in an effort to produce a train system that would provide 250 mph inter-city service with lowered capital...
to continue efforts to build a full-scale prototype. A combination of factors, including Laithwaite's persuasiveness and Bertin's successes in France, quickly gained the company government funding.
Construction of a test track started north of London in 1970. The location was chosen in a flat area that could allow up to 20 miles of track to be laid, although funds only covered the first 4 mile section. Rising costs further limited this to a short 1 mile section. The prototype vehicle, RVT 31, started speed tests in 1973, in February it managed to reach 104 mph in a 20 mph headwind.
In spite of this success, two weeks later the government cancelled further funding. A combination of the total lack of interest on BR's part, and infighting between the various high-speed efforts, prompted the formation of an independent review board that heavily favored APT. The test track was later removed and RTV 31 ended up in a museum.
Aérotrain
SNCF
The SNCF , is France's national state-owned railway company. SNCF operates the country's national rail services, including the TGV, France's high-speed rail network...
. Like BR, SNCF was actively exploring high-speed train service. The public demonstration of the Hovercraft Development system appears to have sparked their interest, and they started funding Bertin's efforts to develop what he called the "Aérotrain
Aérotrain
The Aérotrain was a Hovertrain developed in France from 1965 to 1977. The lead engineer was Jean Bertin.The goal of the Aérotrain was similar to that of the magnetic levitation train: to suspend the train above the tracks so the only resistance is that of air resistance...
".
Lacking the engineering know-how in the nascent LIM field, Bertin's early designs used propellers. Through 1964 the team built a 1/2 scale model of a small hovertrain, and a 3 km long track to test it on. On 29 December 1965 the prototype was first placed on its upside-down T-shaped track, and on 26 March 1966 it reached 202 km/h. Higher speeds could not be reached with a propeller on the short test track, so the engineers equipped the vehicle with small rockets and in December it reached 303 km/h. This success garnered funding for the addition of a Turbomeca Marboré
Turbomeca Marboré
|-See also:-References:* Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9-External links:* *...
turbojet engine taken from a Fouga Magister
Fouga Magister
The Fouga Magister is a 1950s French two-seat jet trainer. The related CM.175 Zéphyr was a carrier-capable version for the French Navy....
, which powered it to 345 km/h on 1 November 1967.
Several newer prototypes of ever-larger size followed, culminating in the I-80, a 44-seat vehicle powered by two turboshaft
Turboshaft
A turboshaft engine is a form of gas turbine which is optimized to produce free turbine shaft power, rather than jet thrust...
engines driving a single shrouded propeller. An 18 km long test track outside of Chevilly was built to test it, where it arrived on 10 September 1969. Two days later it reached 200 km/h, and the day after that 250 km/h, it's design speed. For additional boost a jet engine was added, powering it to 400 km/h in October 1973, peaking at 430 km/h on 5 March 1974, a world record to this day. At the same time, Bertin started exploring the LIM for a lower-speed suburban vehicle, building a prototype known as the S44.
Like their UK counterparts, the seeds of the Aérotrain's demise were already being sown by their counterparts at the national railway. In 1966, other SNCF engineers had made the first proposals for higher speed conventional railways, a proposal that would take on a life of its own and evolve into the TGV
TGV
The TGV is France's high-speed rail service, currently operated by SNCF Voyages, the long-distance rail branch of SNCF, the French national rail operator....
program. Like the Tracked Hovercraft and APT, the Aérotrain project soon found itself fighting with the TGV for future development. Unlike the UK work, however, the Aérotrain had stronger political backing, and did not suffer from the same lack of funding as its British counterpart.
Several development proposals were offered and hotly debated both within SNCF and the government. After many proposals, on 21 June 1974 SNCF signed a contract for an Aérotrain line between Le Défense and Cergy, on the northwestern side of Paris. On 17 July the contract was annulled. The September 1975 Paris-Lyon TGV line was the deathblow to the project, although small-scale work continued until 1977.
TACV
As part of the High Speed Ground Transportation Act of 1965, the Federal Railway Administration (FRA) received funds to develop a series of high-speed trains. In addition to funding development of the successful UAC TurboTrain and more conventional projects, the FRA also took out licenses on Bertin's designs and started efforts to build several prototype vehicles under the Tracked Air Cushion Vehicle (TACV) program. TACV envisioned a linear induction motor (LIM) powered hovertrain with 300 mph (483 km/h) performance. Different elements of the technology were to be tested with different prototypes.In December 1969, the DOT selected and purchased a large parcel of land outside Pueblo, Colorado
Pueblo, Colorado
Pueblo is a Home Rule Municipality that is the county seat and the most populous city of Pueblo County, Colorado, United States. The population was 106,595 in 2010 census, making it the 246th most populous city in the United States....
, and built the High Speed Ground Test Center (HSGTC) for the various programs. For the TACV program, DOT paid for the construction of the test track loops for the different prototypes. However, track construction proceeded slowly.
LIMRV
Since the Bertin team had not yet used a LIM, the first part of the TACV program was dedicated to LIM development. Garrett AiResearchGarrett AiResearch
Garrett AiResearch was a manufacturer of turboprop engines and turbochargers, and a pioneer in numerous aerospace technologies. It was previously known as Aircraft Tool and Supply Company, Garrett Supply Company, AiResearch Manufacturing Company, or simply AiResearch...
built the Linear Induction Motor Research Vehicle (LIMRV), a wheeled vehicle running on standard-gauge railroad track, fitted with a 3000 hp gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
generator to supply the LIM with electricity.
The test track for the LIMRV at the HSGTC near Pueblo wasn't yet complete when Garrett delivered the vehicle: the reaction rail in the middle of the tracks was still being installed. Once the track was ready, linear induction motor, vehicle power systems, and rail dynamics testing progressed and by October 1972, a speed of 187.9 mph (302.4 km/h) was achieved. Speed was limited due to the length of track (6.4 miles) and vehicle acceleration rates. Two J-52 engines were added to the vehicle to propel the vehicle up to higher speeds. These engines were then throttled back so that the thrust of the J-52's equaled their drag. This allowed higher speed testing without building several miles of additional track. On August 14, 1974, the LIMRV achieved a world record speed of 255.7 mph (411.5 km/h) for vehicles on conventional rail.
TACRV
The second stage of the TACV project was a hovercraft testbed initially powered by turbofan engines, the Tracked Air Cushion Research Vehicle (TACRV). BoeingBoeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
and Grumman proposed designs, with the Grumman vehicle being given the go-ahead. Grumman's TACRV was presented in 1972. Although Grumman's efforts got the majority of the funding in the TACV project, ensuring the construction of 22 miles (35 km) of track, the reaction rails for the LIM propulsion were never installed. With jet engine propulsion only, no more than 90 mph (145 km/h) was achieved.
UTACV
The third stage of the TACV project was a complete LIM-powered hovertrain with passenger seating, the Urban Tracked Air Cushion Vehicle (UTACV). Rohr Industries won the contract with a design based on Bertin's Aérotrain, and delivered the prototype to HSGTC in Pueblo in 1974.However, there was almost no money left over, so the Rohr vehicle received only 1.5 miles (2.4 km) of track, on which a maximum of only 145 mph (233 km/h) was possible. By the time the UTACV was ready for testing, most of the budget had already been used up, and no further funds were forthcoming. The need for an electricity supply system, low energy efficiency, and noise levels were seen as problems. The last tests of the Rohr vehicle ended in October 1975. Since then the Pueblo facility has been used for testing conventional trains to this day, now known as the Transportation Technology Center
Transportation Technology Center
The Transportation Technology Center, or TTC, is a railroad testing and training facility located northeast of Pueblo, Colorado. It originated as the Department of Transportation's High Speed Ground Test Center as a site to test several hovertrain concepts...
.
Hovertrains give way to maglev
The idea of using magnets to levitate a train had been explored throughout the active period of the hovertrains. At first it was believed this would be impractical; if the system used electromagnets the control systems would be prohibitively expensive, and at the time there were no suitably powerful permanent magnets that would be able to lift a train.As electronics improved, and electrical control systems with them, it became increasingly easy to build an "active track" using electromagnets. By the late 1960s there was renewed interest in the maglev concept, and several study projects were starting in Germany and Japan. Through the same period, Laithwaite had invented a new form of the LIM that provided both lift and forward thrust, and could be built over an passive track like the conventional LIMs. In either case, only magnets in the immediate vicinity of the train would have to be turned on, which appeared to offer much lower overall energy needs than the hovertrain.
By the early 1970s, a wide variety of new maglev proposals were being actively worked on around the world. The German government, in particular, was funding several different passive and active systems in order to explore which of the proposed solutions made the most sense. By the mid 1970s, several of these projects had progressed to about the same point as the hovertrains, yet appeared to have none of their disadvantages—high sound levels, blown dirt and higher energy use than initially expected.
Although the existing projects, mentioned above, continued on using their existing funding, the lack of further funding is best understood as due to both the rising interest in maglev by some teams and the introduction of high-speed conventional trains by others.
Newer efforts
More recently, a Japanese project known as "Aero-Train" has been built to the extent of several prototypes and a test track. The basic concept is the same as the classic hovertrain, but replaces the active hovercraft system of pumps and lift pads with wings, using the efficient generation of lift from the wing-in-ground-effect.Hovertrains in fiction
- Star WarsStar WarsStar Wars is an American epic space opera film series created by George Lucas. The first film in the series was originally released on May 25, 1977, under the title Star Wars, by 20th Century Fox, and became a worldwide pop culture phenomenon, followed by two sequels, released at three-year...
, throughout the series, hovertrains are depicted - Back to the Future Part IIIBack to the Future Part IIIBack to the Future Part III is a 1990 American science fiction comedy Western film. It is the third installment of the Back to the Future trilogy. The film was directed by Robert Zemeckis and starred Michael J. Fox, Christopher Lloyd, Mary Steenburgen, Thomas F. Wilson and Lea Thompson. The film...
(1990 film), Dr. Emmett Brown and family ride in a steam-powered locomotive time machine hovertrain - "The Train JobThe Train Job"The Train Job" is the second episode of the American science-fiction western television series Firefly created by Joss Whedon, although it was the first to be shown...
" (2002 Firefly television series episode), the crew take on a heist aboard an Altrans hovertrain - The IslandThe Island (2005 film)The Island is a 2005 American science fiction/thriller film directed by Michael Bay and starring Ewan McGregor and Scarlett Johansson. It was released on July 22, 2005 in the United States, and was nominated for three awards including the Teen Choice Award....
(2005 film) features an AmtrakAmtrakThe National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...
hovertrain - Rogue Trooper (2006 video game), a level ("Hovertrain Journey") takes place on a hovertrain
- Secret Agent ClankSecret Agent ClankSecret Agent Clank is a platform game developed by High Impact Games for the PlayStation Portable and published by Sony. It was first released in North America on June 17, 2008. A PlayStation 2 version was ported by Sanzaru Games and was released on May 26, 2009 in North America and in Europe on...
(2008 video game in the Ratchet & Clank series), Ratchet fights Giant Klunk on a hovertrain
See also
- Airboat
- Air Car (hovercraft)Air Car (hovercraft)The Air Car is a do-it-yourself hovercraft that can be built "in a weekend". It has been extensively advertised in the back of Boys' Life magazine.There are 4 different Air Car models, the third design has been copied many times....
- AirboardAirboardThe Airboard is the first commercially marketed single-person hovercraft/hoverboard.Kevin Inkster invented the world's first commercial hoverboard scooter, called the Airboard after being inspired by the Back to the Future movies....
- Avrocar (aircraft)Avrocar (aircraft)The Avro Canada VZ-9 Avrocar was a VTOL aircraft developed by Avro Aircraft Ltd. as part of a secret U.S. military project carried out in the early years of the Cold War. The Avrocar intended to exploit the Coandă effect to provide lift and thrust from a single "turborotor" blowing exhaust out...
- Bora class guided missile hovercraftBora Class guided missile hovercraftThe Bora-class hoverborne guided missile corvette of the Russian Navy, also bears the NATO class name Dergach, is one of the few types of military surface effect ship built solely for marine combat purposes, rather than troop landing or transport...
- Coandă effectCoanda effectThe Coandă effect is the tendency of a fluid jet to be attracted to a nearby surface. The principle was named after Romanian aerodynamics pioneer Henri Coandă, who was the first to recognize the practical application of the phenomenon in aircraft development....
- Ekranoplan
- Fluid bearingFluid bearingFluid bearings are bearings which support the bearing's loads solely on a thin layer of liquid or gas.They can be broadly classified as fluid dynamic bearings or hydrostatic bearings. Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and...
- FlymoFlymoThe Flymo hover mower was invented by Karl Dahlman in 1964 after seeing Sir Christopher Cockerell's Hovercraft machine. "Flymo" is a brand name of the Swedish company Husqvarna AB, formerly a part of Electrolux...
- Ground effect
- HoverboardHoverboardA Hoverboard is a fictional hovering board used for personal transportation in the films Back to the Future Part II and Back to the Future Part III. Hoverboards resemble a skateboard without wheels. Through special effects the filmmakers depicted the boards hovering above the ground...
- HovercarHovercarA hovercar is a transport vehicle appearing in works of fiction. It is used for personal transportation in the same way a modern automobile is employed. You must steer it, like you would a normal vehicle...
- Hovercraft MuseumHovercraft MuseumThe Hovercraft Museum, located in Lee-on-the-Solent in Hampshire, England, is dedicated to hovercraft.The museum has a large collection of various designs of hovercraft - numbering over sixty at the last count...
- HydrofoilHydrofoilA hydrofoil is a foil which operates in water. They are similar in appearance and purpose to airfoils.Hydrofoils can be artificial, such as the rudder or keel on a boat, the diving planes on a submarine, a surfboard fin, or occur naturally, as with fish fins, the flippers of aquatic mammals, the...
- LCACAir-cushioned landing craftAn air cushioned landing craft, also called an LCAC is a modern variation on the amphibious landing boat. These craft are based on small- to mid-sized multi-purpose hovercraft, also known as "over the beach" craft...
- Pegasus (Hovercraft)Pegasus (Hovercraft)The Pegasus is a hovercraft vehicle made for educational purposes. The plans could have been purchased from an article in the January 1984 issue of Popular Mechanics....
- Research Test Vehicle 31
- Resonance method of ice destructionResonance method of ice destructionThe Resonance method of ice destruction can be used by any vehicle capable of traveling on ice cover with sufficient speed and imposing sufficient load. There have been cases of destruction of ice by flexural gravity waves produced by moving cars, trains on railway crossings, aircraft during...
- Surface effect shipSurface effect shipA Surface Effect Ship or Sidewall Hovercraft is a watercraft that has both an air cushion, like a hovercraft, and twin hulls, like a catamaran. When the air cushion is in use, a small portion of the twin hulls remain in the water...
- Tracked HovercraftTracked HovercraftTracked Hovercraft was an experimental high speed train developed in the United Kingdom during the 1960s. It combined two British inventions, the hovercraft and linear induction motor, in an effort to produce a train system that would provide 250 mph inter-city service with lowered capital...
- Zubr class LCACZubr class LCACThe Zubr class is a class of air-cushioned landing craft of soviet design. This class of military hovercraft is currently, as of 2008, the world’s largest hovercraft. There are currently nine ships in active service in the world. The Zubr is used by the Russian, Ukrainian, and Greek navies...
- Hovercraft "Dragonfly"Hovercraft "Dragonfly""Dragonfly" is a Russian-built hovercraft. It is intended for transportation of people and cargoes on a variety of surfaces: snow of any density irrespective of layer thickness, continuous or beaten ice, water of any depth, boggy districts, and ground of any density. Also, consecutive alternations...