The Rohr Aerotrain Tracked Air-Cushion Vehicle (TACV)

Rohr Industries, Inc.'s Aerotrain prototype built in Chula Vista, California (ca. 1973). John Driscoll was a mechanical engineer for the project. NOTE: The raised track in the background was used to demonstrate Rohr's ROMAG vehicles to businesses. It was showcased at Transpo '72.

This is the story of:


(or The Little HSGT That Could)

So how did all this rapid-transit stuff get started in the first place?

Blame it all on the Baby-Boomers!

Twenty years after the end of World War II, the aerospace age was in high gear. The U.S. was seeing more and more durable and comfortable cars on its roads that were capable of traveling faster. Its planes were being improved with more speed and comfort as well. The baby boom created families that were on the go. Everyone was getting a car of their own. And it was foreseen that the current technology of transportation would no longer meet the growing needs of a growing population.

A fifteen year transportation projection for the year 1980 for major U.S. cities had predicted gridlock situations if nothing was done to improve things. Various countries (some newly rebuilt) were beginning to experience signs of traffic congestion in their major cities already. The transit authorities in these countries were even more concerned with what to do about the growing number of cars that were showing up at airports. Their thinking at that time was that the 60 - 500 mph transportation gap which existed between cars and planes could be filled to help ease the flow of travel between cities and reduce traffic on highways and at airports.

Rocket cars for everyone!

Japan had recently built a relatively inexpensive high-speed 320 mph rail train and was already looking into developing a magnetically suspended train to achieve an even faster speed. And France was looking into the construction of 6,000 kilometers of high-speed rail lines. The British were developing a hovertrain to possibly replace their rail system. Canada thought, because of all their snow, that high-speed hovercraft vehicles (ACV) could be a great solution for its travel needs. Another option it was looking into was short-takeoff-and-landing vehicles (STOL).

So of course the U.S felt it could tackle the same problems for its own cities. The Urban Mass Transportation Administration (UMTA) did a survey of the existing forms of land transportation in order to provide some perspective for the discussion on advancing those forms. Decisions were needed on whether to use more advanced technologies to improve high-density traffic areas, or to simply revise existing travel systems to more fundamental concepts, or both.

Personal rapid-transit and mass-transit concepts were compared to see if either conventional or advanced technologies could be implemented to reduce costs and improve performance.

While other factors looked at were whether such new approaches to urban transportation were technically feasible, economically practicable, and socially acceptable.

In most countries at this time, existing rails were not in the best condition. Trains could not reach high speeds without sacrificing safety and comfort, while planes were enjoying both speed and comfort. And it was hoped that trains could one day travel as fast as planes. To accomplish this, new tracks would have to be installed either by tearing out old tracks or by running new tracks alongside older tracks.

Walt Disney, who had already been utilizing ALWEG monorails and WEDWAY peoplemovers for Disneyland, was planning ahead with designs of his experimental prototype community of tomorrow (EPCOT) that he was hoping American enterprises would be interested in helping him build in Florida.

His idea being that future cities built from scratch were easier to design future travel technologies for, rather than trying to introduce future travel into already existing and congested cities.

So the UMTA contracted the TRW Systems Group to do a survey of any current research being done on experimental high-speed vehicles. Data was found for various station-to-station, door-to-door, and continuous-capacity systems.

  • Station-to-station operation: Tracked air-cushion, rolling support, and underground tube vehicle systems.

  • Door-to-door operation: Multi-modal, auto-train, and automated highway systems.

  • Continuous-capacity operation: Endless belt system (travelators).

So in 1965, they looked at rapid rail transportation. They looked at air-bearing systems that traveled in sealed air tubes called tube system vehicles (TSV). They looked at linear propulsion methods. The scale they covered was from the small local commuter transport systems such as the Urbmobile, to the very large super highways for freight trucks only and for specially designed computer controlled cars.

But in the end, TWR's recommendation was to go with high-speed tracked air-cushion vehicles (TACV) since magnarails couldn't be made yet because of problems with producing permanent magnetized ferrite materials cheaply.

France was already within a year of building a TACV which included its own track. And studies could be made on its passenger comfort, safety, affordability, and how to solve the track's switch design problem. It really did seem like tracked air-cushion vehicles were the way to go for future rapid-transit use for the 1980's.

But what kind of track are we talking about here?

A monorail track that is either elevated, or at ground level, or in a tunnel. It was assumed that an air-cushion vehicle traveling on such a track would have a much smoother ride and the passengers wouldn't notice any bumps or dips in the track. And if a monorail could supply electrical power to the vehicle (especially if traveling through underground tunnels), that meant less pollution concerns for the UMTA.

While Jean Bertin was testing his various patented TACV's, which he called Aerotrains, on his monorail tracks in France, the UMTA worried about the noise from the vehicle rockets.

In 1968, Bertin got rid of the rockets and developed a linear induction motor version of his Aerotrain which could reach a speed of 110 mph. In theory, the linear induction motor would be whisper quiet.

Rohr Industries, Inc. was also impressed by Bertin's Aerotrain and licensed the linear induction motor and hovercraft technology from him to build Aerotrains in the U.S.

Rohr began promoting its Aerotrain, hoping to find buyers.

Also in 1968, the UMTA began asking for bids from various aerospace companies around the world to build high-speed vehicles for the U.S. All sorts of companies had an aerospace division in the late 1960's. Especially in the U.S., which was working on sending astronauts to the moon of all places. So of course Rohr knew it had the right vehicle for the UMTA contract and thus put in its bid for it.

In 1969, Westinghouse Electric Corp. was doing studies investigating the power needs for 300 mph tracked air-cushion vehicles, 250 mph linear induction motor-driven rail vehicles, 250 mph wheel-driven vehicles, and 200 mph wheel-driven rail vehicles. Areas of study were on power systems, power distribution, power collection, and power conditioning.

Eventually in 1971, the UTMA selected three aerospace companies as candidates for a new high-speed ground transportation (HSGT) system to solve the future's traffic problem:

  • Garrett Corp.

  • Grumman Aerospace Corp.

  • Rohr Industries, Inc.

The thing that got the UTMA's attention the most was Rohr's full-scale mock-up of its Aerotrain in 1970.

In 1972, Garrett had a model of their vehicle on display.

And Grumman's was still in the design stage.

Meanwhile, the UMTA needed a test-track facility for its three candidates to show off their stuff.

The DOT in Pueblo, Colorado became that site.

Now here comes the Los Angeles part of our story.

In the middle of all this, Los Angeles was looking for a solution to connect Los Angeles International Airport with San Fernando Valley by 1972. So now there was, according to the UMTA, a (perceived) critical need for a high-speed ground transportation (HSGT) system. Also planned for was a connection from LAX to San Diego. Rohr Industries knew this and was hoping to be the winner of the three candidates with the UMTA so its Aerotrain would be that now much needed vehicle.

Rohr even had plans already for the proposed 16.3 mile elevated guideway along the San Diego Freeway to the San Fernando Valley.

And since new high-speed trains were not an option for unsatisfactory track conditions in the US, other means of transportation were discussed as well, such as using high-speed hovercraft and STOL vehicles. Hovercraft didn't require a track to be built for them to travel on. It was thought that tracks would ruin any unique landscapes and the view of open space areas. But hovercrafts wouldn't work well in population centers and were not as fast as TACV's. Some suggested that since hovercraft worked better in water and allowed for new geographical freedoms, that building transportation routes and ports out in water even with hoverport cities would cost less than building conventional new cities. And STOL vehicles were seen as a cheaper alternative to the TACV if people could put up with their noise level. The military, upon hearing what the UMTA was up to, took great interest in hovercraft development for their own use.

Meanwhile, the UMTA thought that the benefits that would come from the research and development of an HSGT vehicle would help establish a potential viable system for future situations where serious gas shortages might occur. And with that idea, the UMTA focused on building the necessary test-tracks for Rohr, Grumman, and Garrett to test their vehicles on.

In 1972, Rohr began building their Aerotrain prototype.

Its construction was completed and ready for commercial use.

The Aerotrain was just one piece of Rohr's transportation puzzle. It would compliment Rohr's other transportation systems: BART, Flxible, and Monocab.

NOTE: In the future, only the BART system would survive. The Monocab (later ROMAG) suspended vehicles stranded its passengers along the rather tight elevated curves of its track. And the Flxible bus suffered from its hydraulic system catching on fire and trapped passengers inside because the rear emergency exit door was also hydraulic controlled. Just some of the reasons why Rohr is no longer around.

Now about the Aerotrain...

Rohr Industries, Inc. thought aerospace was the future for its company.

Even the need for mini-Aerotrains was seen as a reality.

Meanwhile, in Pueblo...

The DOT received money to build the three test tracks needed for the prototype vehicles.

The Garret linear-induction-motor research vehicle (LIMRV) needed a standard-gauge steel railroad track design for its initial tests.

The picture above shows the Garrett LIMRV being tested before a reaction rail was installed on its track. Its turbines were tested in the meantime for propulsion.

Here is a later test of Garrett's linear-induction-motor propulsion. The completed reaction rail for the LIM can be seen on the track between its steel wheels.

It was capable of speeds up to 250 mph (actually clocked going 234 mph during a test in the spring of 1974) using its own onboard free-spool 3,000 hp gas turbine and 3,000 kVA alternator as a power source.

The Garrett ended up cracking its nose. Something about running out of track and having no brakes. So the DOT demanded that additional braking systems be required for the test vehicles. Rohr had to then over-design their brake system and install emergency explosive air-release plates along the Aerotrain's skirt so it could skid on its concrete guideway for extra stopping.

Around this time, the British cancelled their hovertrain development and felt that their test track for it could be easily converted for testing magnetically-suspended vehicles on. This was brought on by research being done with magnetic levitation using superconducting magnets. Even the US took interest in cryogenic engineering research and development.

A majority of the DOT's test track spending money was used on Grumman's project. That was because contractors bid very high and there didn't seem to be any cheaper solution to getting it built. Twenty-two miles of test track for Grumman's TACRV was built. But the cost of building it did not include the additional reaction rail. So the Grumman prototype was only able to test its air propulsion and not its LIM at all.

And since there was no more money for test tracks, building an underground one was certainly out of the question.

Here is the Grumman being tested going in the opposite direction alongside Garrett's completed test track. The plan was to eventually get the track ready for the TACRV's linear induction motor in the later part of 1973. In theory, the TACRV's linear induction motor would provide speeds of up to 300 mph. But in the meantime, the TACRV's air-cushions performed various aeropropulsion tests.

Grumman's goal was to build this kind of track along highway medians to allow their TACRV trains of three to four cars to travel from New York to Los Angeles in eighteen hours. But without any reaction rail, the Grumman's top speeds only amounted to around 90 mph.

Around this time, the military was trying to figure out how to install a nuclear plant inside a hovercraft for power without the skirt being crushed from the extra weight.

Meanwhile, back in Chula Vista...

The Rohr vehicle was given a new coat of white paint over a silver test color that revealed too many dings. And as it was being readied for the trip from its Chula Vista, California plant (ca. 1974) to Pueblo, Colorado for the competition, rumors spread about the DOT taking over the FRA.

The builders were in a rush to get the track together. Fortunately (or unfortunately), they were only allowed to build one and a half miles of test track because someone else wanted twenty-two miles for their prototype and used up nearly all the available funding. So early birds got the longer track at this shindig.

The Aerotrain arrived just in time to get a few test runs in before the DOT took over everything. The FRA had no more money anyway.

And that meant... another paint job.

Top speeds on Pueblo's 1.5 mile reaction rail test track reached about 145 mph. The Rohr engineers wished they were given at least four miles of monorail track to get some real speed out of their vehicle.

Here is a front-view shot of it while parked at the end of the monorail in its garage. You can see the Aerotrain logo decal on its front which all Aerotrains sported. The side railing to the left in this photo provided the 2,000 KW of juice needed to power the air vehicle. Its dual 40" lift compressor fans generated sixty pounds of air thrust per second at 2.5 PSI to lift the Aerotrain off the ground. The black portion underneath was the skirt that held in the air which the Aerotrain floated on.

Note that there is no windshield. A camera was used instead to display the front view on the pilot's monitor. There was also an aft-view camera placed behind a small hole in the back of the vehicle.

Mice were a big problem out in the wilderness of Pueblo. So nose plugs were used to keep them from crawling into the vehicle via the suspension air inlets and chewing up stuff whenever the Aerotrain wasn't being raced about in the Pueblo desert.

Here's a side view of the Aerotrain. On it you can see the front pilot's door (closed) and the two passenger doors (opened). Farther down at the end is the service hatch (closed) which could be used to access an (optional) baggage compartment.

The Aerotrain was a single unit. But later plans would include a means of coupling two units together to carry 120 passengers.

The symbol located just after the pilot's door represented the DOT that Rohr and its competitors were hoping to impress and win a contract with.

Here is a closer view of the pilot's door. Behind it was the pilot's room. Note the monitor used to show what was coming up in the road ahead.

Here is a closer view of the control console.

The passenger doors popped out and moved to the side. Very comfortable chairs, normally not found on monorails, awaited travelers inside. Just inside the passenger door was the testing equipment used for measuring the Aerotrain's speed, vibration, decibel levels, power levels and usage, etc.

Once again, a view of the seating. The Aerotrain's passenger cabin had a very "2001" look to it. Some of you may remember the scene in the movie where Dr. Floyd's pen is floating in zero-g. That was a very cool passenger room he was in, as well.

Here is the back of the Aerotrain. Note the huge propeller and/or giant rocket engines missing from it. Rohr Industries, Inc.'s design was after a more sleek and stylish look. Their vehicle was for real public use, after all.

The high-voltage railing provided the power needed by the Aerotrain. During an earlier test, the Aerotrain brought down power at the test facility track. More powerful transformers had to be installed along the track to get the Aerotrain the power it required.

Under the back end of the Aerotrain were the break pads. The linear induction motor (LIM) that propelled the vehicle could slow it down from 150 mph to 20 mph. The graphite brakes then clamped onto the reaction rail to smoothly stop the vehicle at the platform. One problem though was that someone had the bright idea of mixing tiny copper beads with the graphite which caused melted copper to stick to the aluminum reaction rail which caused problems of its own.

As a side note, Insul 8 worked on the aluminum conductor used for the vehicle.

So what brought an end to the Aerotrain?

During the construction of the Aerotrain in Chula Vista, California, John Driscoll and a couple other mechanical engineers at Rohr joked about its design. Any good engineer will make improvements to a design to make it more efficient and cost less to manufacture and operate.

Afterall, the United States did not (and still does not) have the luxury of using fission plants to provide power for any kind of futuristic Aerotrain. It also did not have the money needed for any kind of Aerotrain infrastructure. Which meant no power plants to make the needed electricity to power the Aerotrain, no oil for the power plants to burn, and no monorail tracks. Thus, no Aerotrains. Just the price of building a raised monorail track to go from city to city was (and still is) enough to bankrupt a country. (As of 2011, the U.S. is already a bankrupt country, so funding any such project is sheer insanity.) No one wanted to pay for a monorail. No one wanted a monorail eyesore going through their town or neighborhood. And since the monorail vibrated so loud before the even louder Aerotrain zoomed by, no one wanted any of it near their homes or offices.

So in reality, what was a better solution for future urban transit using already existing (and paid for) infrastructures?

To solve this problem, John Driscoll came up with a unique idea of using wheels for the Aerotrain to roll on instead of having it hover on air. Then another engineer suggested that maybe the wheels could be made of steel and be designed to roll on steel rails. Soon the idea of a steel on steel, free-rolling vehicle came into play. The engineers thought it was a brilliant plan. Their Aerotrain would then be able to coast on certain areas of the track using no power at all. On other parts of the track though, the vehicle would need to be powered someway. An engineer suggested the use of steam. Maybe for use in a piston configuration. The Rohr Engineers knew they had caught onto something.

A new design was soon born: Steel wheels, steel rails, and a steam powered engine.

Seriously though, it did bother the engineers that a steam locomotive was more energy efficient than the Aerotrain. And when this was mentioned to the higher-ups in the Rohr office that the Aerotrain would cost more money to run than it would make in return, the engineers were simply told that they could find employment elsewhere if they didn't share the company's view.

The Rohr project later almost pulled its own plug when a visiting French engineer, who was curious about the Aerotrain's progress, fried its linear induction motor while trying to start the vehicle. Something was performed out of sequence which led to the reaction rail not having enough time to cool before burned-out metal was shot out the back of the Aerotrain by the very strong magnetic pull of its linear induction motor and frying a few components. The French engineer quickly exited the facility and was never seen or heard from again. That was the only time the French were ever involved with Rohr's Aerotrain. Rohr was able to find a contractor in the area that specialized in linear induction motor repair that replaced all the burned-out wiring. The section of the reaction rail that was melted away was patched up. And soon the Aerotrain was operational again.

But eventually the U.S. Department of Transportation saw the writing on the wall. Which led to Rohr cancelling its Aerotrain project. So in October of 1975, Rohr's test vehicle was "put in mothballs" in its Pueblo garage to keep it preserved for future use in case it was ever called on again.

All of the vehicle's open gaps and access panels were sealed shut to keep dirt from entering them while in storage.

And just to be safe, the Aerotrain was jacked up to insure mice couldn't chew on anything. While taking these photos, John Driscoll noticed that the steel skids under the Aerotrain were a certain blue color. As if they had gotten hot repeatedly. The skids were what the vehicle rested on when there was no air supporting it.

He also noticed a flat spot on one of the Aerotrain's wheels. Yes it had retractable powered wheels in the front to backup the vehicle while it hovered. They were also used to nudge the vehicle forward to assist the linear induction motor at a stand still.

Soon after, the Rohr engineers were approached by the UTDC out of Ontario, Canada to design for them a rapid transit system. The engineers spent over two years (being on and off of the project during that time) designing what would become this ICTS train for use in Canada. It too used a linear induction motor. But it did not hover on an air cushion like the Aerotrain. It used steel wheels on steel rails.

Unfortunately, Rohr's manager allowed the UTDC to pick his engineers brains for the ICTS designs without ever getting a contract signed. So once Rohr's final design specs were approved by the UTDC, the UTDC said, "Thanks. We'll call you." When Rohr asked when they should start building the ICTS for them, the UTDC said, "Since we now have all the plans we need, we can build the ICTS ourselves. Goodbye." And having no contract meant getting no payment.

The UTDC's working ICTS prototype first appeared in the December 1980 issue of Popular Science. Rohr Industries, Inc. is never mentioned in the article.

By the way, this is how a Rohr Aerotrain would have looked for commercial use. Very 1970s color.

This is how the Aerotrain would have probably appeared inside a station. The lighting from both the tinted Sun and station interior would have given the Aerotrain this kind of look as it came to a stop to pick up new arrivals.

Some vandals managed to find the French Aerotrain.

Yikes! So what happened to Rohr's Aerotrain?!

That's a very good question.

Rohr built only one Aerotrain. Never to return to Chula Vista. The test track contractor for CDOT's Pueblo facility, TTCI, had no use for the vehicle of course. So the U.S. Government simply gave the Aerotrain Prototype to the city of Pueblo with one condition. That it would be shown for display in a good light, like at a museum.

Satellite photos do show...

Today, the Rohr Aerotrain is currently parked outside on a small piece of track at the Pueblo Weisbrod Aircraft Museum. After years of outside desert weather, the faded DOT Test-Track colors still show. The "A" decal on the nose has been peeled off by someone.

The Aerotrain is in one piece still. The two 350 hp lift motors, the lift fans, the hydraulic propulsion system, the LIM propulsion unit, the A/C units, and the brake system are still intact.

The only problem is that someone brought the vehicle outside to rot for over thirty years.

The rear breaks, which show signs of heavy use, provide another clue as to what kind of punishment the Aerotrain had taken during its hay day. The 1.5 miles of test track had made Rohr's aim of reaching 150 mph very difficult because the Aerotrain needed more track for its deceleration.

So in order to stop the vehicle sooner before running out of track, the test pilot had to use everything the vehicle had to stop the thing in time. The LIM was used for braking. The rear brakes were applied as well. The wheels were lowered and used for braking. And as a last ditch effort, the cushioned air would be vented out to bring the vehicle crashing down on its skids to provide even more friction for braking. But 145 mph was the best the test pilot could ever hope to reach on such a short test track.

UPDATED Aug-8-2009:

The Rohr Aerotrain was in motion once again after 35+ years! Its new resting place is now at the end of West D Street in Downtown Pueblo. Grumman's TACRV was also transported and has been parked next to it.

Watch the video below.

Shawn Driscoll wrote a short blurb that can be read here in an official write-up on the matter. The Pueblo Railway Museum now refers to this once futuristic vehicle as simply "The Rohr".

But if such futuristic high-speed rapid-transit vehicles were in operation, what would our world have looked like?

Well, for one thing, it would not have looked like this, this, or even this. The Aerotrain was kept at a distance from most people. Some common Aerotrain hazards were:

  • Extreme sound levels -- As with all hovercraft, the Rohr Aerotrain was a very loud machine. It could not sneak up on looky-loos because it was heard from quite aways. About an inch and half of insulation had to be put inside the air ducts to help reduce the vibration noise. Otherwise, one had to wear ear protection while waiting at a station gate to board a vehicle. The Aerotrain didn't touch the ground after all. So quite a bit of noise would be expected from such a hovercraft.

  • Electrical hazards -- The vehicle was not something that one could just walk up to while the engine was running anyway. It had a static charge built up that had it be grounded at each stop along its route.

  • Sand storms -- There was a lot of air blowing dirt and trash and anything else it could clear from the station track as it hovered along side a platform.

  • Not very approachable -- As with all hazards, there was a required fence to keep waiting passengers far away from the Aerotrain platform while it was in operation so they wouldn't be hit by flying debris or have one of their children sucked into an air duct. Passengers only entered and excited the vehicle while it was turned off and statically discharged.

Then there were the other holdups with such experimental TACV and PRT vehicles:

  • Technical problems and money.

  • TACV development was in its very early stages and would not arrive for another decade or more.

  • Problems with integrating such vehicles into present urban transit systems and city buildings themselves.

In the meantime, according to the UMTA (we're talking back in 1972 now), some relief would be on the way:

  • The 1970s would bring improvements in state-of-the art buses travelling 80-90 mph in exclusive busway lanes.

  • And also bring new rail cars with improved suspension and air conditioning.

  • And some totally new rail car designs and other exciting transportation goodies.

And it was suggested back then that while we all waited for this new technology, we should try using two older modes of getting around. Walking, which gives us an average speed of 2.5 mph and is also good for us. And the other is bicycling, which is even better exercise and is the most efficient means of transportation (based on distance covered for energy input). Thank you, UMTA.

But one can always dream still...