As you might expect from something that emerges from SpaceX founder Musk's imagination, Hyperloop looks and feels very sci-fi. It is certainly many strides forward from what we have now, and in essence this is Musk's inspiration.
Musk's 2013 white paper envisages a vacuum tube with almost all the air removed, as pods are pushed along by a series of electromagnets, kind of like pneumatic tubes. The system could transport freight, as well as passengers. Those in the know and at the coalface of development say this could mean speeds of up to 760mph - the equivalent of travelling from San Francisco to Los Angeles in just 30 minutes.
Musk, busy as he is with SpaceX, decided that Hyperloop would be open-source, allowing developers and tech and transport experts from across the globe to plot a route from proposals on a piece of paper to physical test tracks and designs. Progress in the three years since the idea was proposed has been swift.
In February of this year, students at the Massachusetts Institute of Technology (MIT) won a competition to design an experimental capsule for the Hyperloop, while Hyperloop One - formerly Hyperloop Technologies and one of the companies to materialise since Musk's decision - has started construction on a test track in Nevada.
Meanwhile, Hyperloop Transportation Technologies (HTT), another independent developer, has plans for a prototype track in Quay Valley, California. However, it is HTT's bold plan for a Hyperloop system in Slovakia that has turned heads, as hitherto much of the focus has been on the US and the San Francisco to Los Angeles link.
A European Hyperloop: why Slovakia?
In March, HTT signed an agreement with the Slovakian Government to explore the feasibility of building a local Hyperloop system in Bratislava, with the potential of an expansion to Vienna and Budapest. Vazil Hudak, Slovakia's minister of economy, said at the time: "Hyperloop in Europe would cut distances substantially and network cities in unprecedented ways. A transportation system of this kind would redefine the concept of commuting and boost cross-border cooperation in Europe."
The first stage of this huge undertaking would run in just Bratislava. Costing an estimated $200-300m, this could be completed by 2020, says Dirk Ahlborn, HTT CEO. The links to Vienna and Budapest could then follow, creating a trio of what you might call 'super' connected countries, accessible in approximately ten minutes.
But, why Europe? And why Slovakia, specifically?
"They actually approached us," explains Ahlborn. "There was a young Slovakian woman studying in the US and she wanted to become part of HTT. She reached out over Facebook to my business partner but as they weren't connected, her message went into a different inbox and he didn't see the message."
After returning to Slovakia, she began working in government, and prominent members of the cabinet, including Hudak, were soon won over. A series of meetings between HTT and government officials then led to the agreement in March.
Since then, much of Ahlborn's time has been spent analysing potential routes and fleshing out the details of what is a hugely ambitious project. At this stage, being only weeks since the agreement was signed, a great deal remains up in the air.
"There's obviously lots I cannot talk about, but things are moving forward," Ahlborn admits. "We have been meeting with different companies, universities and research institutes. We have lots of interest in Slovakia around fostering innovation around transportation."
The obstacles: a long way to go
Interest there may be, but it is foolhardy to suggest that, in a project of this size, HTT will not encounter some form of opposition. First, there's the complex melting pot of public opinion. Large infrastructure projects inevitably fire up local sensitivities.
On numerous occasions Ahlborn highlights the necessity of getting the public on board: "We don't want this to be behind closed doors, we want to do it in a very transparent way," he says. "I believe the most important factors are the adoption from passengers and public support."
A platform incorporating universities, research institutes, the public and others, is being established to work through the intricacies. No doubt that Ahlborn and HTT are keen to avoid any impression that the Hyperloop is not putting the needs of its future customers first. One advantage for HTT is that the government approached them, showing their hand early on. "In Slovakia," Ahlborn continues, "the people in government want to change the country and make it leap forward, rather than taking small steps." Government support will also be necessary when it comes to acquiring land.
This leap is very much speculative at the moment. As ever, money is a talking point. The $200-300m figure listed earlier and the cost of the whole project - which of course depends on the route - could be financed through a public-private partnership. Private investment will be crucial for any successful Hyperloop, no matter where it is based.
"We have plenty of investors who can help finance this," says a confident Ahlborn. "There's always new technology that might make it more efficient or cheaper to build." He warns, however, that with so many "moving parts", it's difficult to give an accurate prediction.
This statement can also be applied to the ambitious 2020 date for the Bratislava section. From a technical point of view, it can be done, says Ahlborn. The technology exists - "we know we can build the pylons needed, we can build tubes and create a low-pressure environment inside the tubes. We also know we can levitate it," he explains.
From HTT's end, 2020 is possible. But this is also about people and politics. The next step for HTT is a user analysis and looking at the most appropriate route. "How much would it impact the people living there? How much would it cost? What's the business behind it? How does it pay for itself?" asks Ahlborn.
Also, is it safe? Musk's white paper states it is "intrinsically safer than aeroplanes, trains, or automobiles", but if there's a serious incident and there's depressurisation, oxygen masks would be deployed. The white paper added: "In the unlikely event of a large scale capsule depressurisation, other capsules (pods) in the tube would automatically begin emergency braking whilst the Hyperloop tube would undergo rapid re-pressurisation along its entire length." Pods would also include a reserve air supply.
Passive magnetic levitation: 'cheaper and safer'
One question that has been answered is the form of magnetic levitation that HTT will use. In May, Ahlborn and his colleagues announced it had licensed a technology called passive magnetic levitation, which HTT says is more efficient and safer than the one used by Maglev trains in Japan.
"The levitation that we are using is passive, which means the levitation occurs through the movement of the pod," explains Ahlborn.
Bibop Gresta, chief operating officer at HTT, described this in more detail: "A passive levitation system will eliminate the need for power stations along the Hyperloop track, which makes this system the most suitable for the application and will keep construction costs low." Gresta adds that as the levitation occurs through the movement, even a power failure would not stop Hyperloop pods from levitating. Only after reaching minimal speeds would they touch the ground.
Ahlborn confirms that HTT plans to use this form of levitation in Slovakia, as well as at its proposed five mile track prototype in Quay Valley. And, what of this track? Construction is expected to start later this year but "some of this is not in our hands, unfortunately", he adds.
While it would be wrong to suggest a great rivalry exists between HTT and Hyperloop One - both share a sense that Hyperloop is the answer to the world's transportation woes - each, of course, wants to be seen as the standard-bearer.
Hyperloop One has recently secured $80m in finance, creating partnerships with a host of new investors, including SNCF, the French national rail company. In May, the company also held an open-air test of its prototype propulsion system in Nevada, reaching speeds of around 105mph on a 400ft track.
"The time is right to bring new thinking to old problems and harness new technologies and services to make a quantum leap in transportation," said Rob Lloyd, CEO of Hyperloop One, in a statement, while co-founder Shervin Pishevar called it the right time for "the brightest minds" to come together and "eliminate the distances and borders that separate economies and cultures".
This message of connectedness is often put forward as the answer to those who question the need for the Hyperloop. "I think it's exciting how we can use technology to connect people," says Ahlborn. "It will do to the world what rail did in the 19th century; it will change the way we live."
The entrepreneur confirms that HTT is in discussions with roughly 20 cities around the world and is confident that after the first Hyperloop is built, many more will follow. It is "greener, safer, faster," he argues. Slovakia takes centre stage for now, but for how long?