Elon Musk is no stranger to extraordinary technological predictions, and his forecast for hyper-speed travel is no less dramatic than an Arthur C. Clarke novel. Yet, Hyperloop technology could well be a functioning part of society by 2030.
Musk first coined the term back in 2013, with the idea to create a new mode of transport for people and freight, and support the growing global economic requirements of faster, cheaper, safer and more efficient transportation1. The Hyperloop concept is a vacuum tube train design where capsules will accelerate gradually via electric propulsion through a low-pressure tube, float above the track using magnetic levitation, and then glide for long distances at speeds more than 1220kph due to ultra-low aerodynamic drag.
Tests of the concept are currently taking place in France and the USA, and there are currently numerous proposals for Hyperloop projects and routes in North America, Europe, the Middle East, India and South Korea. This potential is driving innovative engineering advances, and substantial investments are beginning to be committed.Breaking down 1000kph travel
SpaceX’s key components of the proposed design are:
A magnetic levitation system is proposed for the capsules to ensure low frictional losses. Each capsule will have an on-board compressor to reduce choked flow effects when passing through the tube at high speeds, and thus addressing issues relating to the Kantrowitz limit (the maximum speed that the pod can travel before flow around the pod chokes and air resistance sharply increases) . The initial Hyperloop design would include a capsule with a carrying capacity of 28 passengers. With departures every two minutes, which could be reduced to 30 seconds during peak times, an operating capacity of 840 passengers per hour is assumed. Based on the claimed speed of travel, the capsules would be separated by approximately 37 km on average. A larger system has also been proposed for transportation of three full size cars and passengers.
To achieve the proposed maximum speed of 1,220 kph, an advanced linear motor would propel the capsules at a maximum acceleration of 1g. Smaller linear motors are planned for urban areas, for which the topography would necessitate lower speed travel, and changes in gradients. Similar systems were proposed to be used for deceleration of the capsules as they approach their final destination, with an energy storage system to improve system efficiency.
- Tube design
The tubes were proposed to be constructed from steel, with two separate tubes mounted side by side on pylons for travel in both directions along a route. For the passenger-only system, the tubes would be 2.23 m in diameter, and having an estimated wall thickness of 20-23 mm.
With the promised speed of 1,220 kph, travel times could be significantly reduced for both passengers and freight. Due to faster transit times, stocks and inventories could also be reduced, lowering costs across several points of production chains. ￼Vicinity to city centre is, however, a prerequisite this efficiency due to necessary fast turnaround and embarking times.
As such, investment into researching and developing Hyperloop technology is ramping up.
At present, even the most advanced of the several projects currently underway appear to be at a very early prototype stage. The earliest expected service date for any of these projects is towards 20302. It’s speculated that projects in the Middle East3 or India4 could be the first to demonstrate a complete system capable of transporting freight and/or passengers, albeit at slower service speeds than that originally indicated by SpaceX5. A number of these routes appear to be much shorter than the original ‘ideal’ city pairing suggested in the SpaceX paper. Rather than shortening journey times to compete with high speed rail and air travel, the justification for these shorter routes appears to be centred around reduction of commuting times and easing congestion in more densely populated areas.
While hyperloop development projects are cropping up around the world, cost and risk are two hurdles that haven’t yet been overcome entirely.
There is great uncertainty attached to the full cost picture of the Hyperloop system and infrastructure. At the fact of it, household names investing in Hyperloop are forecasting attractive numbers: although heavily dependent on route and whether it be a passenger or cargo application, initial calculations carried out for SpaceX’s solution, Hyperloop Alpha, indicate that infrastructure cost will be in the range of 17 million USD per mile6. Meanwhile, Virgin estimates that their Hyperloop One system could be two-thirds that of high-speed rail7.
However, even though estimates indicate lower costs than comparable alternatives like high speed rail and aviation, the full picture of hidden costs like acquiring land rights is not clear. Sources claim that the cost could be as much as 16 times higher than that originally suggested in the SpaceX paper8. This cost comparison will contrast even starker for Hyperloop cross-continental Hyperloop routes, in addition to being logistically complicated.
Then there is the cost of safety. During this development process it is vital to build a realistic picture of the risks of Hyperloop. This will enable balanced decisions to be taken about the opportunities and measures that can be put in place at the early stages of projects to manage the risks to acceptable levels. Elimination of hazards and ensuring inherent safety principles are applied is key during the concept and design stages, as during operation there is limited scope for changing fundamental aspects of the system.
With regards to the tube through which the vehicles will travel, the main challenges for the design, and integrity during operation, are likely to be in balancing the technical and economic factors influencing route selection and whether to bury, install above ground, or even to take offshore. This is coupled with achieving the necessary global straightness requirements for the tube, and maintaining these during service, together with managing local imperfections of the tube and, if used, the rails. Underpinning these decisions will be selection of optimum materials for the tube and supports, with possibly conflicting requirements relating to vacuum containment, global alignment, static and dynamic behaviour, section manufacturability, sustainability, carbon footprint, construction, and in-service integrity management. Where subsea tube sections are being considered, there will be different design, construction and integrity management challenges to be addressed.
With these hurdles considered, a first fit-for-service hyperloop system isn’t expected to be produced until 2030.Contributors
Main author: Hans Anton Tvete
Editor: Tiffany Hildre