A sketch of billionaire Elon Musk's proposed Hyperloop transport system

SpaceX founder unveils 'fifth mode of transport'

Billionaire Elon Musk has unveiled plans for a transport system that is a “cross between a Concorde, rail gun and air-hockey table”.

Musk, who made his name as a PayPal founding member before going on to start rocket manufacturer SpaceX and electric car maker Tesla Motors, has revealed his vision for a futuristic "Hyperloop" – a solar-powered network of crash-proof capsules that would whisk people from San Francisco to Los Angeles in half an hour.

In a blog post Musk outlines a solar-powered system that would rely on a linear electric motor to propel capsules floating on a cushion of air through a long tube kept at very low-pressure stretching roughly 400 miles from LA to San Francisco – taking a mere half hour as opposed to an hour and 15 minutes by jet and about 5 and a half hours by car.

As many as 28 passengers could ride in pods that could leave as frequently as every 30 seconds, according to the 57-page design plan, and the project would cost an estimated $6bn (£3.9bn) to build over 7 to 10 years, considerably cheaper than the $68bn high-speed rail project covering the same route that was approved last year and faster than its 2 hours and 40 minutes journey time.

“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?” he wrote on his blog.

“If we are to make a massive investment in a new transportation system, then the return should by rights be equally massive.”

Earlier this summer at the D11 conference, when Musk first mentioned the idea of the Hyperloop, he described it as a "cross between a Concorde, a rail gun and an air hockey table."

The undertaking would be a large one with construction likely to take 7 to 10 years, and Musk has made the design plans open-source as he has said he is too busy running Tesla and SpaceX to build the Hyperloop himself.

But he believes that an enlarged version of the old pneumatic tubes used to send mail and packages within and between buildings in the past is the only realistic option for a “fifth mode of transport”.

He 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.”

One key issue for the system would be overcoming the so-called Kantrowitz limit, which is the maximum capsule width to tube width ratio before the capsule begins to behave like a syringe and tries to push the entire column of air in the system ahead of it.

Musk’s, approach is to mount an electric compressor fan on the nose of the pod that actively transfers high pressure air from the front to the rear of the capsule, which would both relieve the pressure and provide a cushion of air beneath the capsule following the same principle as an air hockey table.

To power the system Musk is proposing claims an on-board battery would have more than enough capacity to power the a fan for the length of the journey as long as the energy used to accelerate the pod to high subsonic velocity is drawn from the external linear electric motor with further motors to provide a boost roughly every 70 miles.

Energy for the system itself will be drawn from solar panels on the top of the tube, which Musk predicts will provide more than enough electricity for the entire system, even when taking into account storing enough electricity in batteries to operate at night.

He also proposes that energy could be stored in the form of compressed air that then runs an electric fan in reverse to generate energy.

With California prone to seismic activity the design also takes account of the danger of earthquakes, with the tube built on pylons so the tube is not rigidly fixed at any point and with two adjustable lateral dampers and one vertical damper inside each one.

And in the event of a disaster meaning the system is someway breached, the low pressure system will be set to a level where standard commercial pumps could easily overcome an air leak and the transport pods could handle variable air density.

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