Abstract
The present article outlines the core technologies needed to realize the Hyperloop transportation system (HTS). Currently, the HTS vacuum tube train concept is viewed as the fastest way to cross the earth’s surface. However, the concept has not yet been demonstrated for subsonic or near-sonic speeds in large-scale implementations. Among the challenging technical areas are the tube’s depressurization, the capsule’s air resistance, and choked flows occurring around the capsule. There is also a need for effective levitation and propulsion solutions compatible with the velocities being proposed. Moreover, several conflicting objectives have been identified in the HTS design. It is highlighted that the tubes should be wide enough to lower the capsule’s drag forces but that a large-sized tube comes at the expense of higher operational energy costs and infrastructure investments. Another struggle is aiming at a low-cost passive track design and, and at the same time, a lightweight vehicle. One technical path is to turn the whole guideway into an electric propulsor, arriving at a ‘lightweight capsule solution’ (LCS). Alternatively, the vehicle could be transformed into a ‘modified airplane’ that stores massive amounts of onboard energy, yielding an energy-autonomous ‘low infrastructure solution’ (LIS). In a case study, it is shown that even LIS technology is compatible with short-haul flights (1500 km) but that it requires an energy reservoir of about 30% of the capsule’s overall mass. Results and discussions presented in this paper are supported by analytical predictions with parameters or input data either supported by referred simulations or experiments. In general, the paper aims to open up the discussion, provide a sufficient understanding of the Hyperloop field’s multidisciplinary aspects, and establish a foundation for further investigations. In the end, new research tasks have been defined, which have the potential to go beyond the state of current knowledge.
Highlights
The idea of near-sonic ground travel has been an idea for over a century
Air bearings were proposed for levitation, and track-integrated coils were considered for propulsion
The Hyperloop transportation system (HTS) concept is currently viewed as a promising alternative to short-haul flights, where it can promise less travel time and lower fuel consumption per passenger revenue kilometer (RPK)
Summary
The idea of near-sonic ground travel has been an idea for over a century. Already decades ago, the design of a partially evacuated tube was patented to reduce air drag resistance [1]–[3]. The Hyperloop transportation system (HTS) describes passenger capsules moving inside a tube of a low-drag low-pressure environment (i.e., as low as one-thousand of the atmospheric pressure). They are being propelled and guided by a track. The HTS concept is currently viewed as a promising alternative to short-haul flights, where it can promise less travel time and lower fuel consumption per passenger revenue kilometer (RPK) This is illustrated, where an energy consumption metric (i.e., drag-to-lift ratio) is used to compare different transportation alternatives. This paper presents the technology fundamentals of the Hyperloop concept, as well as the proposed technical solutions for propulsion and levitation. Performance investigations of complete technical solutions are analyzed and discussed in Section V before the paper’s outline is discussed and concluded in Sections VI and VII, respectively
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