The Hyperloop concept was first proposed by Elon Musk in 2013 as a futuristic transportation system that would use low-pressure tubes to transport passengers and cargo at supersonic speeds. Since then, it's gained a lot of attention from the media and the public but hasn't delivered the promised travel revolution.
The name is fancy but the idea itself is centuries old, originally sketched out in 1799 as the atmospheric railway. The first designs used metal pipes or tunnels with centralized steam power and carriages pushed along with air pressure. Mechanically simple and reliable, these pneumatic tubes eventually became ubiquitous during the 20th century for carrying everything from mail and medicine to food and even small animals.
They're still used today in large buildings like factories, banks, hospitals and warehouses for their simple design and versatility in moving all kinds of objects through long and complex routes.
While there were some early versions of pneumatic tubes used to carry people, they never reached the practicality of conventional railroads once steam engines became small and efficient enough for locomotives to pull cars with onboard power. Steel rails are also much cheaper than tunnels, rapidly deployed across terrain, and don't have to deal with ventilation and access issues.
Throughout the 1900s, sci-fi designs kept evolving the tube train concept into faster train travel with low-pressure evacuated tunnels to remove air resistance from moving trains. Propulsion also switched from large fans and jet power to magnetic levitation (MagLev) using powerful magnets and linear-induction electric motors to hover and move over the track without touching anything, eliminating friction from wheels and rails. This combination would allow trains to accelerate rapidly and maintain very high speeds with little effort.
MagLev has developed into real technology and is already in use around the world with some experimental routes hitting 600 kmh. Placing these routes in evacuated tubes is definitely possible, and can create a train system reaching supersonic speeds to become fastest mode of commercial travel available - but engineering practicality and economic feasibility quickly become major obstacles.
Tunnels (or above ground tubes) are extremely costly and take decades to plan and build. Maintaining a vacuum with an airtight seal over long distances is incredibly challenging, and very energy intensive. There are also many logistical issues, like how to keep up the speed while stopping at all the locations that people actually want to go to, and dealing with inevitable real-world scenarios like crashes, breakdowns, and attacks. The lack of an easy fail-safe from power loss or track and tunnel problems also means reliability is crucial and accidents can become catastrophic.
Unfortunately, building something so massive, high-tech, and resource intensive is still too prohibitively expensive for even the richest countries. The Hyperloop is an evolution of the original vactrain concept - but there's a reason this has remained a concept for so long because the trade-off in cost and complexity for faster travel doesn't make sense in a world with airliners and Wifi allowing for "fast-enough" speeds while being fully connected.
There are many things we can build if we had no economic limitations, but unfortunately the world just isn’t so simple and we’ll need to make some big advances in energy, engineering and societal priorities before we can build something like a vacuum train. It’s definitely real technology, but not realistic enough for our world today.
- The Hyperloop has various designs from using a partial vacuum with air-bearings and fans instead of maglev, and building above-ground tubes rather than tunnels. Overall, it’s similar complexity with different trade-offs.
- I recommend reading the Vactrain wikipedia entry to see the advancements and trials over the years.
- Originally answered on Quora at https://www.quora.com/How-feasible-is-the-idea-behind-Hyperloop/answer/Mani-Gandham