PSI - Issue 44

Andrea Santangelo et al. / Procedia Structural Integrity 44 (2023) 626–632 Andrea Santangelo/ Structural Integrity Procedia 00 (2022) 000–000

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2. Overview of hyperloop main components The hyperloop system, described in general terms, consists of a tubular infrastructure (also called “vacuum structures”), vehicle structures (or “pods”), the vehicle levitation/guidance system and a propulsion/braking system. Since the hyperloop concept was first conceived, around ten years ago, significant research, investment and testing has taken place to establish the feasibility of key principles and subsystems required to realize this technology. 2.1. Vacuum Structures The vacuum structures consist of partially evacuated tubes pumped down to 100 Pa (roughly 1/1000th of atmospheric pressure) and they are typically considered to be supported by columns. However, in dense urban areas with no suitable corridor, the below surface format (underground solution) would provide an alternative option. The above-ground design allows for easier access maintenance and security, a lower infrastructure footprint relative to most other transport infrastructure installed at-grade, and the potential for increased corridor capacity in congested areas. The travel speeds envisaged will limit the maximum curvature and gradient of the infrastructure alignment, which might limit the number of suitable routes in urban areas 2.2. Vehicles According to the first concept depicted in the Musk’s document “ hyperloop Alpha white paper ”, the vehicles were designed to carry 28 passengers or 10 metric tons of freight. New concepts propose larger numbers such as 60 passengers capsule and up to 120 metric tons of freight to be arranged in airline standard containers. Other concepts include clusters of pods, magnetically linked each other with individual reduced capacity. Such vehicles would resemble the fuselage of commercial small planes and they might use similar lightweight materials. 2.3. Levitation and guidance As previously mentioned, the very low friction environment of the hyperloop system may allow vehicles to simply coast for most of their journey, reducing the need to apply propulsion force and resulting in a significantly more energy efficient approach than conventional Maglev technology. Maglev technology is implemented in hyperloop systems in two distinct ways: ElectroDynamic Suspension or passive levitation (EDS) and ElectroMagnetic suspension or active levitation (EMS). In short, ‘active levitation’ is based on actively controlling the attractive force generated between a vehicle- side electromagnet or a combination of permanent- and electro-magnets and ferromagnetic guideway infrastructure to levitate the Hyperloop vehicles inside the tube. ‘Passive levitation’ uses vehicle-side permanent magnets or superconducting electromagnets and highly conductive guideway infrastructure that generates opposing magnetic fields through induction. These produce a stable levitation force that does not require active control as long as there is relative motion between the vehicle and the guideway. Finally, the vehicles will also require lateral stability/guidance. Just as with levitation, electromagnetic guidance can be achieved actively or passively - but instead of providing vertical lift, it offers horizontal stability. This may be integrated within the propulsion and levitation systems or provided by a separate system in some cases. With a passive levitation system, it is beneficial to integrate guidance and levitation while for an active levitation system, the guidance and levitation permanent magnets and/or electromagnets are usually separated (to provide better control flexibility) and placed perpendicular to each other. 2.4. Propulsion The Hyperloop concept has chosen Linear Induction Motor (LIM) technology as primary source of propulsion. LIMs are rotational electric induction motors that have been used in various capacities for over 3 decades, even as part of a concept maglev train project. They are extremely apt to provide propulsion to a hyperloop pod, due to their not relying on physical contact, due to the initial levitation effect they provide, and due to their controllability. In