Hyperloop: The Fifth Mode of Transportation
By: Asme Iiest Shibpur Student Section
Tags: Future, Hyperloop, Technology, Transportation, Science

Hyperloop, the fifth mode of transportation as proposed by Elon Musk, is no more futuristic and has become reality with Virgin Hyperloop’s first successful passenger ride. This has reignited the interest and has opened up doors to new possibilities and opportunities. Even in India, the Mumbai-Pune Hyperloop system is very much on the agenda of the Virgin Hyperloop and is set to make operational before 2030. Moving with a speed of about 730mph, it will cover a distance of 140 km under 30 minutes.

But, attaining a speed of about 730mph seems to be a herculean task. Isn’t it? So, here’s how the hyperloop is being planned, to reach near Mach speed.

At its core, hyperloop is all about removing the two things that slow down regular vehicles: Air Resistance and Friction.

All open-air systems face the problem of aerodynamic drag. The drag forces quadruple as the velocity of the vehicle doubles, and, to overcome that drag force it needs eight times the power to increase its speed. Thus drag limits the top speed for ground-based open-air systems. To overcome this problem, the Hyperloop capsules are made to travel through a low-pressure tube (approximately 100 Pa) and thereby minimizing the influence of drag and resistive forces. The vacuum tube structure could be designed to be built overhead on pylons, at ground level, shallowly below ground, or deeply below ground, following existing terrain conditions and the requirements on the radius of curvature. To deal with friction, the pods are made to hover above its track. Musk originally suggested doing this with air bearings, little jets of air on the bottom of the pod. But today, most of the hyperloop engineers have decided to rely on magnetic levitation (maglev) or magnetic suspension.

Let’s find out more about it.

Levitation, Propulsion and Suspension

Magnetic Levitation is a method by which an object is suspended with no support other than magnetic fields. Hyperloop uses non-contact magnetic levitation, guidance, and propulsion systems and has no wheels, axles, and transmission systems. They move along magnetic fields that are established between the pod and its guideway. Thus, contrary to traditional high-speed railroad vehicles, there is no direct physical contact between hyperloop capsules and its guideway. These conditions of no mechanical contact and no friction provided by such technology makes it possible to reach higher speeds of travel. Along with Hyperloop, magnetic levitation is also used in super-fast maglev trains and has various engineering uses including magnetic bearings. It can also be used for display and novelty purposes, such as floating speakers, idols, etc.

Currently, there are two main suspension systems used in maglev levitation of hyperloop.

Electromagnetic Suspension (EMS), and

Electrodynamic Suspension (EDS)

Both suspension systems facilitate safe travelling at high speeds, low pollution because of electrically powered, low maintenance and high capacity to accommodate increasing traffic growth, but they are technically very different. Performance of EMS systems is based on attractive magnetic forces between iron core electromagnets and ferromagnetic guideway. Electromagnets, that have current flowing through them, are first placed on the underside of the pod, which creates a magnetic field that is attracted to the stationary ferromagnetic guideway. This attraction results in the pod to be levitated about 10mm to 20mm above the guideway.

Propulsion in the EMS system is carried out by the support magnets on the hyperloop capsules, which provide an alternating current, that works to create a series of attracting and repelling poles, resulting in forwarding movement of the hyperloop.

On the other hand, the EDS system relies on the principle of superconductivity and works with repulsive magnetic forces. Superconducting materials are cooled to extremely low temperatures and then they are placed on the side of hyperloop pods and interact with eight-shaped coils on the side of the guideway. When the coils experience the changing magnetic field of the superconductor’s motion (as the hyperloop moves), two currents are induced, that opposes the change in a magnetic field:

One below, that creates a reactive magnetic field, that opposes the superconducting magnet’s pole, and

One above, that creates a pole that attracts it.

Thus, the two forces work together to achieve an approximate levitation of 100mm above the guideway. A variant of EDS technology — as used in the Inductrack system — uses an array of permanent magnets (Halbach Arrays) on the underside of the train, instead of powered electromagnets or cooled superconducting magnets. This is also known as passive magnetic levitation technology.

Propulsion in the EDS system is achieved by a linear synchronous motor, consisting of additional coils in the guideway that provides a three-phase alternating current. The magnetic field created by the superconductor then interacts with this magnetic field to propel it forward.

To tackle the issues of increasing pressure and choked flow at high speed, Musk offers what is perhaps the most innovative component of the entire design: an air compressor mounted on the front of the pod. The compressor would draw air from the pressurized column at the front of the vehicle, and funnel it to the back to generate extra thrust, effectively propelling it forward like a rocket. The compressor is driven by an electric motor which gets its power from onboard rechargeable DC batteries. To achieve very high speeds, the adoption of a linear induction motor (LIM) is the most efficient way to produce frictionless thrust able to overcome the aerodynamic drag. Solar panels eventually cover the tube structure to recharge the DC batteries. Standard commercial pumps could easily overcome the air leak and maintain the low pressure needed in the tube. The LIM is clean, and its maintenance is easy as it has no moving parts or gears.

Conclusion

While Hyperloop technology promises to be a highly innovative transportation mode that could enable true high-speed ground transportation, the development of the technology is still in the early stages. The system is a large-scale engineering project, with development continuing on all elements of the vehicles and infrastructure, including propulsion systems, levitation systems, guidance and control, signalling, thermal, and so on.