Elon Musk has started the building revolution for a new train system.

Dubbed Hyperloop, it will allow you to get from London to Edinburgh or LA to San Francisco in under 30 minutes. But what is it and how does it work? Good questions. Musk has likened it to a vacuum tube system in a building used to move documents from place to place. Confused? No worries. Here's everything you need to know about the futuristic train coming from the founder of Tesla and SpaceX.

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The Hyperloop is essentially a train that Musk calls "a cross between a Concorde, a railgun, and an air hockey table". It's based on the very high-speed transit (VHST) system proposed in 1972, which combines a magnetic levitation train and a low pressure transit tube. It evolves some of the original ideas of VHST, but it still uses tunnels and pods or capsules to move from place to place.

Musk has likened it to a vacuum tube system in a building used to move documents from place to place.

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One of the biggest problems with anything moving is friction, both against surfaces and the environment the pod is moving through.

Hyperloop proposes to move away from traditional wheels by using air bearings for pods instead. This will have the pod floating on air. It's similar to maglev, in which the electromagnetic levitation of the train means there is no friction like a traditional train that runs on tracks. This is how current maglev trains can achieve super speeds, like the 500km/h maglev train in Japan.

Another proposal, from Hyperloop Transportation Technologies, uses passive magnetic levitation, meaning the magnets are on the trains and work with aluminium track. Current active maglev needs powered tracks with copper coiling, which can be expensive.

The Hyperloop will take this to the next level by traveling through low pressure tubes.

The Hyperloop will be built in tunnels that have had some of the air sucked out to lower the pressure. So, like high-altitude flying, there's less resistance against the pod moving through the tunnel, meaning it can be much more energy efficient, which is desirable in any transit system.

The original VHST proposed using a vacuum, but there's an inherent difficulty in creating and maintaining a vacuum in a tunnel that will have things like stations, and any break in the vacuum could potentially render the entire system useless. For Hyperloop, the idea is to lower the air pressure, a job that could be done by regularly placed air pumps.

Low pressure, however, means you still have some air in the tunnels.

The air bearing and passive maglev ideas are designed not only to levitate the pod, but also see the pod moving through the air, rather than pushing the air infront of it and dragging it along behind. The air cushion will see the air pumped from the front of the pod to the rear via these suspension cushions. The tunnels envisioned are metal tubes, elevated as an overground system.

Musk has suggested that solar panels running on the top of the tunnels could generate enough electricity to power the system. It could run as an underground system, too.

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Hyperloop is being proposed as an alternative to short distance air travel, where the system will be much faster than existing rail networks and much cleaner that flight. Hyperloop isn't about going as fast as possible, because you'll have to deal with high G forces when it came to turns, which isn't ideal for passenger travel. Speeds of over 700mph are suggested for journeys.

But there are practical implications that have to be considered on a short stop-start journey, such as the acceleration and deceleration sensation that passengers would go through.

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Musk hasn't yet given a date when we can expect to see Hyperloop up and running, he's merely announced that it will be made.

A one-mile test track built by SpaceX adjacent to Hawthorne, its California headquarters, has been built, and the first successful trial has been carried out. Hyperloop One plans to send an 8.5-metre long pod down a set of tracks in Nevada. In May 2017, a pod levitated on a separate test track in Nevada for 5.3-seconds and reached 70mph.

The first trial using one of the 8.7-metre passenger pods has now been carried out too. The pod travelled along the 500-metre test track, and reached a speed of 192mph before safely coming to a complete stop. 

Planning documents currently propose a route between LA and San Francisco, a 354-mile journey, that would cost around $6 billion in construction. This is based on a passenger-only model, whereas one that can also transport vehicles would be $7.5 billion. This extra expenditure would be worth it since more people could use the system, offering potentially larger returns.

Shervin Pishevar, co-founder and chairman of Hyperloop Technologies, aims to shuttle passengers and cargo in high-speed pods that are smaller than most planes and trains and designed to depart as often as every 10 seconds. He recently told CNBC: "Hyperloop will be operational, somewhere in the world, by 2020."

Must tweeted in July 2017 that his Boring Company tunnel project has received “verbal [government] approval” to build a Hyperloop that would connect the cities of New York City, Philadelphia, Baltimore, and Washington, DC. He also tweeted more details about the project. The new Hyperloop would only take 29 minutes to travel between New York City and DC, Musk claimed. 

It would feature “up to a dozen or more” access points via elevator in each city. Keep in mind Musk released his Hyperloop concept as an open-source white paper in 2013. As a result, Hyperloop Transportation Technologies is looking into a setup that would link Slovakia, Austria and Hungary. This is the same company that plans to create the five-mile test loop in California by 2018.

Musk has continually talked about his agitation with surface-level transportation. His tunnel project, dubbed the Boring Company, which began as a joke, is Musk's attempt at digging more efficiently. He's working on tunnel-boring machines than can both dig and reinforce tunnels, simultaneously. He also recently announced the completion of the first section of tunnel under Los Angeles.

Back to the “verbal govt approval": apparently, Musk's Boring Company will dig up the tunnel used for the New York-to-DC route. We've contacted the US Department of Transportation for more information. But based on Musk's tweets, we know work on the New York-to-DC Hyperloop will happen alongside the LA tunnel that's already in progress.

According to Hyperloop Transportation Technologies CEO Dirk Ahlborn, the cost of a ticket should be around $30 mark to get a passenger from LA to San Francisco. That, he says, should allow the company to pay back its initial costs in eight years.

Whether this will actually be the price of a ticket remains to be seen.