When it was launched, it seemed little more than a pipe dream.

Billionaire inventor Elon Musk unveiled a futuristic plan for a new type of transport that would shoot capsules of passengers along a tube at around the speed of sound.

Elon Musk, one of the brains behind the online payment system PayPal, and SpaceX claims his solar-powered 'Hyperloop' could herald a revolution in travel.

The Hyperloop Transportation Technologies design for Elon Musk's Hyperloop. It hopes to produce a technical feasibility study finished in mid-2015.

The team believes the system could link the majority of America's major cities together.

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THE HYPERLOOP: HOW IT WORKS Inside the tubes, hyperloop pods are mounted on thin skis made out of inconel,an alloy already used by Musk's SpaceX firm that can withstand high pressure and heat. Air is pumped into the skis via small holes to make an air cushion, and each pod has air inlets at the front. An electric turbo compressor compresses air from the nose and routes it to the skis and to the cabin. Magnets on the skis, plus an electromagnetic pulse give the pod its initial thrust; reboosting motors along the route would keep the pod moving at just below the speed of sound so the system does not produce sonic booms. Advertisement

Musk believes it would take just 30 minutes to travel the 381 miles from Los Angeles to San Francisco – half the time it takes in a plane – and likened the passenger experience to Disneyland's rocket ride Space Mountain.

Now, the plans are beginning to take shape.

A new firm, Hyperloop Transportation Technologies, is developing plans to makes the tubes a reality - and it has recruited experts from around the world.

The crowdsourced firm has around 100 engineers on the projects, and nearly all of them have day jobs at companies like Boeing, NASA, Yahoo!, Airbus, SpaceX, and Salesforce.

Dirk Ahlborn, the CEO of the new company, says it seemed the perfect way to develop the plans, with a site called JumpStartFund that aimed to crowdsource ideas.

He got in touch with SpaceX, Musk's firm, and the work began.

The team includes about 25 UCLA graduate architecture students at a facility in Playa Vista, although most members work remotely.

Ahlborn hopes to have a technical feasibility study finished in mid-2015, according to Wired.

So far, the team has made progress in three main areas: the capsules, the stations, and the route.

'They look at this like a blank sheet of paper on which they can realize their fantasies,' UCLA professor Craig Hodgetts said.

Musk's idea is based on the pneumatic tubes that fire capsules of paperwork between floors in offices. In this case, the capsules would carry people – even cars – in low-pressure tubes to minimise turbulence and maximise speed.

Musk believes it would take just 30 minutes to travel the 381 miles from Los Angeles to San Francisco – half the time it takes in a plane – and likened the passenger experience to Disneyland's rocket ride Space Mountain.

On top of pylons is a hovering capsule inside a low-pressurized tube, which can reach speeds of up to 760 mph.

'The only resistance would be the air in front of the capsule, which we moved to the back by using a compressor,' Hyperloop CEO Dirk Ahlborn said.

At its launch, Musk described the Hyperloop design as looking like a shotgun, with the tubes running side-by-side for most of the journey, then closing at either end to form a loop.

Trains of capsules would shoot through the almost air-free tube at up to 760mph,

accelerated by magnets which would also keep each pod on a steady course.

Each capsule would float on a cushion of air it creates as it speeds along – similar to an air hockey table.

So far, the team has made progress in three main areas: the capsules, the stations, and the route.

The proposed route of the firstHyperloop follows Interstate 5, which runs through the agriculture-richCentral Valley in California. It would take seven to ten years to build.

Capsules carrying six to eight people would depart every 30 seconds, with tickets costing around £13 each way.

In his proposal released online, Musk wrote: 'Short of figuring out real teleportation, which would of course be awesome (someone please do this), the only option for super-fast travel is to build a tube over or under the ground that contains a special environment.'

The proposed route of the first Hyperloop follows Interstate 5, which runs through the agriculture-rich Central Valley in California. It would take seven to ten years to build.

Musk put the price tag at around £4billion but pointed out that that is around one-tenth of the projected cost of a high-speed rail system that California has been planning to build.

The 100 person team is spread around the world

The tyeam has even built models in their bid to find out if Hyperloop could actually work

However, transport experts received the proposal with scepticism, citing barriers, such as the threat of earthquakes in the region.

Musk has said he is too focused on other projects, for example his rocket building company SpaceX, to consider building the Hyperloop, and instead is publishing a design that anyone can use or modify.

Musk said he started thinking about the idea when plans for a 130mph (210km/h) high-speed train connection between LA and San Francisco were revealed, but now he has detailed his own version on Tesla's site .

'Flight' of the future: The hyperloop will travel the distance between Los Angeles and San Francisco in only 30 minutes

Smooth ride: 'It would have less lateral acceleration which is what tends to make people feel motion sick than a subway ride, as the pod banks against the tube like an airplane,' creator Elon Musk said

'I originally started thinking about [Hyperloop] when I read about California's high-speed rail project which was somewhat disappointing,' he told a Google Hangout with Richard Branson last week.

'It's actually worse than taking the plane. I get a little sad when things are not getting better in the future.

'Another example would be like the Concorde being retired and the fact there is no supersonic passenger transport. I think that is sad. You want the future to be better than the past, or at least I do.'

The entrepreneur made his fortune with the internet payment system PayPal before switching his skills into developing the new Falcon rocket system for Nasa and the Tesla electric car.

Mr Musk claims Hyperloop would be a practical solution for city pairs separated by 1,000 miles (1,600km) or less. Beyond this distance, it would be better to take a plane, he explained.

Unique: Travellers would enter aluminium pods which are mounted above the ground on columns 50 to 100 yards apart

Modern: This image shows how people would travel in the pods

Pulled all nighter working on Hyperloop (as did others). Hopefully not too many mistakes. Will publish link at 1:30 PDT — Elon Musk (@elonmusk) August 12, 2013

But for the shorter distance, his new concept would beat the plane, he argues, because it would not waste time ascending and descending.

'You want a transport system that is roughly twice as fast as the next best alternative, that costs less, that is safer, that is not subject to weather and is more convenient,' Mr Musk said.

'If there were such a thing, I think most people would take it. In fact, it would increase the travel between the city pairs because of the increased convenience.'

Experts say Musk's track record could help the plan become a reality.

'Hyperloop is quite an old science fiction idea but Elon Musk is the sort of man who could make it work,' said physicist Martin Archer from Imperial College London.

Space-like: This conceptual design of the machine shows that it will have a futuristic look

Built to last: The inventor boasted that the tracks would be immune to weather and earthquakes, though it is not immediately clear how so

Creature comforts: The legroom is said to give would-be passengers a disruption-free ride

'He's the guy who made electric cars go fast with Tesla, which many people didn't think would be possible; and he's the head of SpaceX which is the only commercial rocket builder that has managed to hook up with the International Space Station.'

Musk says he will leave it to others to build the system initially.

'I have to focus on core Tesla business and SpaceX business, and that's more than enough,' he told investors of Tesla, his electric car firm.

'If nothing happens for a few years, with that I mean maybe it could make sense to make the halfway path with Tesla involvement,' Musk said.

'Hyperloop consists of a low pressure tube with capsules that are transported at both low and high speeds throughout the length of the tube,' Musk said in an exhaustive paper detailing the system posted online.

'The capsules are supported on a cushion of air.'

Each of the capsules is pressurized, and Musk says they have an emergency braking system as well as a reserve air supply in the event of an emergency.

Appealing to environmentalists: This graph shows the energy cost per passenger on different modes of transportation for the specific San Francisco-Los Angeles journey

There and back: The 'loop' portion highlights the fact that there would only be two stops

He admits the scheme came from a disdain for current systems.

'When the California 'high speed' rail was approved, I was quite disappointed, as I know many others were too.

'How could it be that the home of Silicon Valley and JPL – doing incredible things like indexing all the world's knowledge and putting rovers on Mars – would build a bullet train that is both one of the most expensive per mile and one of the slowest in the world?'

Musk claims the scheme can power itself through solar energy.

'By placing solar panels on top of the tube, the Hyperloop can generate far in excess of the energy needed to operate.