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003 / The Fifth Mode / Part 1

By Khaled Abou Alfa • Published April 2019

Athens, Greece, in the 80s and 90s was an interesting place on many levels. The country was going through a major transformation. European money, and ideas, were flowing in the country moving its outlook and future. This change was gradual, with many promises and discussions but few actions taken. The momentum shifted once Athens become the host city for the 2004 Olympic Games in September 1997. The next 7 years would bring on huge infrastructure changes as the time for procrastination ended and the era of action began.

Chief among these changes was the start of works carried out to expand the single rail line that the city enjoyed. While this line served a purpose, it was very limited in scope. It was a single train line that covered the needs of a limited part of the population. The extension of the Athens Metro was a significant improvement in the lives of the population. Where it would take an hour or more in a crammed uncomfortable bus to make a journey from the suburbs to the centre of Athens, it now took 12-15 minutes. For those of us who lived through this change, it was a revelation. With the aim of giving this same feeling to the entire world, 9 years later Elon Musk would relaunch an idea. A 200 year old idea that came by many names, the vactrain or atmospheric railway. Musk had a better name, he called it Hyperloop.


Imagine a world where travelling from your city to the next major city takes a matter of minutes, rather than hours. A method of transportation which meant to be 4 times as fast as a train, and 2 times as fast as an aeroplane. Now imagine this method of transport is available to you as soon as you arrive  —  no waiting for anyone else to get there. The weather or elements cannot disrupt this mode of transportation — no more delays because of leaves on the train track. Finally, existing renewable energy technology can provide all the power necessary for this mode of transport. That is the disruptive and transformative promise behind Hyperloop. 

The reality of bringing this idea to life involves solving many engineering challenges. If it was easy, it would have already be in operation for over 50 years or more. So what makes this time different, apart from the new name and having Musk’s large cache behind it? Is this idea viable or will it join the pantheon of vaporware?

Engineered Solutions

If I have seen further than others, it is by standing on the shoulders of giants.
— Isaac Newton

Open source software works on the premise of building on top of what came before you, allowing the next person to continue.  Musk would open source’ his team’s technical analysis behind Hyperloop for others to take and expand. Published in August 2013, his Alpha document admits that the idea isn’t unique. Rather the intention was to try and address the shortfalls of previous iterations. Musk is quick to points out, that those ideas haven’t borne any real world examples. 6 years on, his proposed solutions haven’t faired much better. While Hyperloop adopts the look and feel of rail, the similarities remain aesthetic. The true distinction is that Hyperloop is trying to replicate air travel inside a tube, on the ground. The two main areas of technology required for Hyperloop are the pods and the tube. Alpha proposed the following ways in which Hyperloop distinguishes itself against previous (similar) ideas:

  1. The pods themselves would use air bearing suspension, rather than magnetic levitation
  2. The tubes would be medium’ vacuum, rather than a complete vacuum. 
  3. The propulsion and levitation systems for the pods would remain in the pods and rely on the tube only for the vacuum.


In order for wide adoption of Hyperloop, it has to be commercially accessible. The main factor that drives the cost down, when compared against High Speed Rail (HSR), its closest competition, is size. Dependant on the final pod designs, Hyperloop will need two tubes, each around 3-5m internal diameter. By comparison, HSR requires a 29m wide corridor above ground. While this corridor reduced once it becomes a tunnel, HSR would still need 15-20 times more material removed than Hyperloop. By keeping the size small, the cost can reduced further using techniques such as micro-tunnelling. Micro-tunnelling is currently viable for diameters up to 3m. increasing the reach in more dense and urban areas.

Countries and cities around the world are considering (or being considered) Hyperloop as part of their future plans. The buzz generated around Hyperloop has made consideration of an unbuilt, untested system, the responsible choice to make. Many cities have commissioned feasibility reports to help determine the cost of ownership.


Total Cost, in US dollars (Billions)

The major cost of Hyperloop is without doubt the infrastructure - stations, tunnels, bridges, pumps, air-locks, power systems. Although the cost of these elements can be calculated with reasonable accuracy, the published estimates vary considerably between each other. While they all come at a much higher premium than what Alpha published, they do agree that, in theory, Hyperloop could be built at a fraction of the cost of HSR. What fraction exactly is unknown. The value of this unknown, built up of contingency and fairy dust, has driven many to pause publishing further cost estimates. 

Total Cost per mile, in US dollars (millions)

Tube Design

The requirements of the tube is at the very core of what makes Hyperloop interesting to countries all over the world. Hyperloop promises a method of transport that offers a lower barrier for entry spatially, technically and ultimately commercially. Hyperloop tubes are self contained, and so don’t interfere with their surroundings. Don’t create external sound and can be crossed safety (either underneath or above). Hyperloop enables many to dream of high speed travel within nations that currently don’t have any form of rail, much less high speed rail (HSR).

The tube itself would need to deliver a vacuum through which pods would travel in. Against minimal resistance, the pods, in theory, could achieve the speed of sound (around 1200km/hour). Alpha proposed the use of commercially available pumps, to de-pressurise to around 1/1000th of atmospheric pressure - roughly 1/1000th of the pressure felt standing on the ground at the sea.

The infrastructure doesn’t have to provide a perfect vacuum for the entire stretch of the route. The feasibility of being able to achieve this vacuum remains up for debate. The simple fact of the matter being that nothing even remotely on this scale has ever been built. To put this into perspective, the now abandoned Swissmetro system, was going to operate at 1/10th of atmospheric pressure. Achieving a lower pressure would add significant complexity and associated cost. Rather than a single pump, the Hyperloop system would need a series of secondary and even tertiary pumps. This 1/1000th of an atmosphere is upper limit thinking, which in turn will have an impact on the achievable speeds inside the tube itself.

Unaddressed Shortfalls

The construction of a tube system also present its own unique obstacles that need to be overcome. Installing elevated tubes that house a vacuum inside them compounds those obstacles even further. Dependant on the location of construction, issues such as thermal expansion, deflection, workmanship and seismic considerations need to be addressed. Of note is the work published by TransPod who have shared the most interesting study to date on the design and limitations of the infrastructure.

Security measures and scenarios also need consideration. How do you protect a tube 25mm thick, that stretches over many Km from a breach? While mass transportation accidents occur, they don’t disrupt the entire method of transport. What do the preventative and emergency measures look like?

Over the last 6 years there have been many claims on when the first production track between two real locations will begin construction. Now in 2019, we are approaching many of those original dates, yet no real works have begun in any country. The complex engineering challenges associated with Hyperloop have yet to be tackled, much less resolved. One of the reasons that could be holding back the progress in this area is to see which technology for the pods emerges victorious. This will inherently define the exact form that the tube will take. As the infrastructure is the most expensive part, measured in billions rather than millions, governments and clients will not make such a fundamental expense when the necessary technology inside has not settled down.

In part 2 we discuss Pod design and the state of the Hyperloop industry.