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Hyperloop is a proposed very high-speed ground transportation system for both passenger and freight that has the potential to be revolutionary, and which has attracted much attention in the last few years. The concept was introduced in its modern form relatively recently, yet substantial progress has been made in the past years, with research and development taking place globally, from several Hyperloop companies and academics. This study examined the status of Hyperloop development and identified issues and challenges by means of a systematic review that analyzed 161 documents from the Scopus database on Hyperloop since 2014. Following that, a taxonomy of topics from scientific research was built under different physical and operational clusters. The findings could be of help to transportation academics and professionals who are interested in the developments in the field, and form the basis for policy decisions for the future implementation of Hyperloop.
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applied
sciences
Review
Hyperloop Academic Research: A Systematic Review and a
Taxonomy of Issues
Konstantinos Gkoumas


Citation: Gkoumas, K. Hyperloop
Academic Research: A Systematic
Review and a Taxonomy of Issues.
Appl. Sci. 2021,11, 5951. https://
doi.org/10.3390/app11135951
Academic Editor: Nicola Bosso
Received: 24 May 2021
Accepted: 24 June 2021
Published: 26 June 2021
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4.0/).
Joint Research Centre (JRC), European Commission, 21027 Ispra, Italy; konstantinos.gkoumas@ec.europa.eu;
Tel.: +39-0332-78-6041
Abstract:
Hyperloop is a proposed very high-speed ground transportation system for both passenger
and freight that has the potential to be revolutionary, and which has attracted much attention in the
last few years. The concept was introduced in its modern form relatively recently, yet substantial
progress has been made in the past years, with research and development taking place globally,
from several Hyperloop companies and academics. This study examined the status of Hyperloop
development and identified issues and challenges by means of a systematic review that analyzed
157 documents from the Scopus database on Hyperloop since 2014. Following that, a taxonomy
of topics from scientific research was built under different physical and operational clusters. The
findings could be of help to transportation academics and professionals who are interested in the
developments in the field, and form the basis for policy decisions for the future implementation of
Hyperloop.
Keywords: Hyperloop; vactrain; scientific research; taxonomy; technologies
1. Introduction
Mobility and transportation are among the most essential and important services to
society. They encompass interconnected systems that are intended to cover the demand for
mobility of people and goods. Transportation systems are intrinsically complex, including
elements, both physical and organizational, that interact with and influence each other
directly and indirectly, frequently in a nonlinear manner, and with the occurrence of feed-
back loops. [
1
]. According to this perspective, the transportation system is essentially a
highly dynamic complex, large-scale, interconnected, open, socio-technical (CLIOS) sys-
tem [
2
]. Nevertheless, present-day transportation modes (i.e., rail, road, air and waterborne
transportation) are based on consolidated concepts, and improvements over the years have
been essentially evolutionary, focusing on delivering a safe, efficient, reliable and accessible
transportation system.
In the last decade, several transportation concepts and technologies have been identi-
fied as very promising. The impact of disruptive transportation technologies, i.e., those
technologies with the potential to create disruptive innovation at industry and society
level [
3
], has been an important area of research and development. In the transportation
sector, information and communication technologies (ICT) and the Internet of Things (IoT)
are bringing a revolution to the sector, with the advent of connected and automated road
mobility being a notable example [4].
Hyperloop is one of those very promising and possibly disruptive future transporta-
tion technologies. Its development has received extensive media coverage over the last
years following the Hyperloop Alpha white paper by Elon Musk published in 2013 [
5
].
Hyperloop consists of a system of tubes where vehicles (pods) travel at high speed (the
original concept claims a top speed of 1220 km/h) in a low-pressure environment. Other
than speed, Hyperloop’s main advantage is that the partial vacuum lowers the air resis-
tance (drag), thus, consuming less energy during acceleration and cruise [
6
]. An initial
Appl. Sci. 2021,11, 5951. https://doi.org/10.3390/app11135951 https://www.mdpi.com/journal/applsci
Appl. Sci. 2021,11, 5951 2 of 18
feasibility study published already in 2016 identifies research topics related to Hyperloop
technologies [7].
After the white paper and the initial hype, several companies in the US brought
together engineers and venture capital money to perform research and development and
make Hyperloop a reality [
8
]. Later on, the same companies expanded to Europe, and
other Europe-based companies engaged in similar activities [
9
], including the planning
and development of Hyperloop test sites.
Furthermore, recent developments regarding the need for standardizationin Europe
and the US highlight the interest in the regulation of Hyperloop. In Europe, the “Sus-
tainable and Smart Mobility Strategy” was presented in December 2020 by the European
Commission and the accompanying action plan of initiatives will guide its work for the next
four years. Among the objectives of this plan is to “assess the need for regulatory actions
to ensure safety and security of new technologies and concepts such as Hyperloop” [
10
].
Before that, a new Joint Technical Committee (TC), CEN/CLC/JTC 20, was launched by
the European Committee for Standardization (CEN) and the European Committee for
Electrotechnical Standardization (CENELEC) to address the need for the standardization
of Hyperloop systems [
11
]. A year before, in 2019, the U.S. Department of Transporta-
tion (DOT) created the Non-Traditional and Emerging Transportation Technology (NETT)
Council, an internal body with the objective of identifying and resolving gaps, either legal
or regulatory, that may obstruct the deployment of Hyperloop, among other new technolo-
gies [
12
]. In January 2021, the NETT Council presented the “Hyperloop Standards Desk
Review” with the scope of assessing the status of Hyperloop standardization activities,
developing a foundation for future Hyperloop standardization efforts, and consequently,
paving the way towards the development of a preliminary framework of Hyperloop system
components and associated regulations and voluntary technical standards [13].
The dynamics of the technology and the progress made toward future Hyperloop
deployment in Europe is highlighted by a recent mapping of activities in the industry
and European institutions [
14
]. Nevertheless, to test the safety, efficiency and reliability of
Hyperloop in the field, beyond research and development (R&D), a long enough, full-scale
prototype track is necessary.
Beyond the US and Europe, in China and Korea, as patent activity shows, there is
substantial R&D from CRRC Yangtze Co., the Korea Railroad Research Institute (KRRI)
and the Korea Institute of Construction Technology (KICT) [14,15].
Considering the above, this study examines the status of Hyperloop scientific devel-
opments, identifying issues and challenges. It is based on initial considerations developed
in [
14
]. Compared to that previous study, a systematic review was performed, and the
fields of research were explicitly identified. Consequently, a taxonomy of scientific research
issues was developed by analyzing all Hyperloop research in the literature, using the
methodology developed by the European Commission’s Transport Research and Innova-
tion Monitoring and Information System (TRIMIS) [
16
]. Accordingly, the literature was
organized in relevant clusters and for each cluster combination, the issues were identified
as lower-level items in the taxonomy.
The findings could be of help to transportation academics and professionals who are
interested in developments in the field, and form the basis for policy decisions for the
future implementation of Hyperloop.
The paper consists of the following parts: after the introduction, the next section
discusses the materials and methods used in this study, drawing from the Scopus database
and a physical system decomposed into several clusters. Section 3provides the results from
the analyses grouped under the different clusters. Section 4provides an initial taxonomy
based on the performed analysis and a brief discussion. Section 5provides the conclusions.
Appl. Sci. 2021,11, 5951 3 of 18
2. Materials and Methods
The methodology presented in this section focuses on capturing research findings,
aiming at the identification of trends, and consequently, building a taxonomy of issues.
The Scopus database, which has scrupulous indexing rules, was used as a source.
For the analysis, the following steps were taken:
A search using specific keywords (“Hyperloop” or “tube transport” or “vactrain”) was
carried out, in the abstract, title, or keywords. Results were limited to those published
after 2013 (when the modern concept of Hyperloop was introduced), and documents
from health sciences were excluded due to the lexical ambiguity of “Hyperloop
transport” term. The exact query used was: TITLE-ABS-KEY (“Hyperloop” OR “tube
transport*” or “vactrain”) AND PUBYEAR > 2013 and not SUBJAREA (MEDI OR
NURS OR VETE OR DENT OR HEAL). This search performed in June 2021 resulted
in 229 documents.
An additional manual filtering of the documents one-by-one, on the basis of their
title or abstract limited, resulted in 161 documents. The aim of this filtering was to
eliminate those documents that were not relevant to the field due to lexical ambiguity
and those that simply outlined Hyperloop-related aspects. This left 96 articles, 57
conference papers, three reviews, three notes, one letter and one book chapter.
Figure 1shows the distribution of the documents over the considered time period.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 19
2. Materials and Methods
The methodology presented in this section focuses on capturing research findings,
aiming at the identification of trends, and consequently, building a taxonomy of issues.
The Scopus database, which has scrupulous indexing rules, was used as a source.
For the analysis, the following steps were taken:
A search using specific keywords (“Hyperloop” or “tube transport” or “vactrain”)
was carried out, in the abstract, title, or keywords. Results were limited to those pub-
lished after 2013 (when the modern concept of Hyperloop was introduced), and doc-
uments from health sciences were excluded due to the lexical ambiguity of “Hyper-
loop transport” term. The exact query used was: TITLE-ABS-KEY ("Hyperloop" OR
"tube transport*" or "vactrain") AND PUBYEAR > 2013 and not SUBJAREA (MEDI
OR NURS OR VETE OR DENT OR HEAL). This search performed in June 2021 re-
sulted in 229 documents.
An additional manual filtering of the documents one-by-one, on the basis of their title
or abstract limited, resulted in 161 documents. The aim of this filtering was to elimi-
nate those documents that were not relevant to the field due to lexical ambiguity and
those that simply outlined Hyperloop-related aspects. This left 96 articles, 57 confer-
ence papers, three reviews, three notes, one letter and one book chapter. Figure 1
shows the distribution of the documents over the considered time period.
Figure 1 shows an overview of the results, which are destined to increase in 2021.
Figure 1. Evolution of Hyperloop academic research.
After this step, an analysis of all abstracts (and in case of doubt, of the full paper)
took place, and the research was quantitatively assessed, focusing on several clusters. In-
spired by the decomposition approach from [14], this was done by means of a system
approach, breaking the Hyperloop system into five physical parts (Figure 2). These parts
cover the entire hyperloop system, and outline interacting subsystems.
0
5
10
15
20
25
30
2014 2015 2016 2017 2018 2019 2020 2021
Number of documents
Year
Note Review Book Chapter Letter Article Conference Paper
Figure 1. Evolution of Hyperloop academic research.
Figure 1shows an overview of the results, which are destined to increase in 2021.
After this step, an analysis of all abstracts (and in case of doubt, of the full paper) took
place, and the research was quantitatively assessed, focusing on several clusters. Inspired
by the decomposition approach from [
14
], this was done by means of a system approach,
breaking the Hyperloop system into five physical parts (Figure 2). These parts cover the
entire hyperloop system, and outline interacting subsystems.
Appl. Sci. 2021,11, 5951 4 of 18
Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 19
Figure 2. Hyperloop system decomposition (adapted from [14]).
The five physical clusters are:
Hyperloop as a system: this includes research that encompasses the entire system
and that cannot be considered under other disaggregated levels. Examples may in-
clude efficiency and energy studies of the system in operation.
Substructure (including foundations and bridge work): focuses mostly on structural
engineering design for the supporting structure.
Tube: considers aspects related to the tube structure.
Tube pod interface: focuses on research on the interface between the tube and the
pod. Examples may include aerodynamic phenomena as a consequence of the pres-
sure variation.
Pod: focuses on aspects related to the pod (e.g., levitation, suspension, powertrain,
electronics)
In addition, five horizontal (operational) clusters (energy, operations, communica-
tions, aerodynamics, safety) were considered.
It should be noted that this decomposition (into five physical and five horizontal
clusters) while meaningful, is not the only one possible. In fact, in a design process it is
impossible to decompose a system uniquely [17]. Nevertheless, this provides a rather ge-
neric and complete higher-level decomposition, which can be further broken down into
lower hierarchies. For example, the “pod” cluster can be further decomposed into sub-
clusters, covering the powertrain, the levitation and suspension blocks, etc. Likewise, the
horizontal clusters can be further elaborated to cover additional operations. In this sense,
the decomposition is scalable and provides the starting point for adding more elaborated
layers of detail.
These clusters, although developed independently for this study, also encompass
and are aligned with the priority work areas identified by the CEN/CENELEC TC on Hy-
perloop standardization, which include pressures of operation, door sealing, vehicle-tube
interface, communication protocols and emergency evacuation [13].
Sections 3.1 to 3.5 present the results for the five physical clusters. In the analyses,
each paper is also linked to one of the five horizonal clusters. Finally, Sections 3.6 and 3.7
present an overview of research involving general discussions and Hyperloop network
developments. These last two, are not linked to the physical clusters since they focus on
discussion rather than on the development of specific technologies.
Figure 2. Hyperloop system decomposition (adapted from [14]).
The five physical clusters are:
Hyperloop as a system: this includes research that encompasses the entire system and
that cannot be considered under other disaggregated levels. Examples may include
efficiency and energy studies of the system in operation.
Substructure (including foundations and bridge work): focuses mostly on structural
engineering design for the supporting structure.
Tube: considers aspects related to the tube structure.
Tube pod interface: focuses on research on the interface between the tube and the pod.
Examples may include aerodynamic phenomena as a consequence of the pressure
variation.
Pod: focuses on aspects related to the pod (e.g., levitation, suspension, powertrain,
electronics)
In addition, five horizontal (operational) clusters (energy, operations, communications,
aerodynamics, safety) were considered.
It should be noted that this decomposition (into five physical and five horizontal
clusters) while meaningful, is not the only one possible. In fact, in a design process it
is impossible to decompose a system uniquely [
17
]. Nevertheless, this provides a rather
generic and complete higher-level decomposition, which can be further broken down into
lower hierarchies. For example, the “pod” cluster can be further decomposed into sub-
clusters, covering the powertrain, the levitation and suspension blocks, etc. Likewise, the
horizontal clusters can be further elaborated to cover additional operations. In this sense,
the decomposition is scalable and provides the starting point for adding more elaborated
layers of detail.
These clusters, although developed independently for this study, also encompass
and are aligned with the priority work areas identified by the CEN/CENELEC TC on
Hyperloop standardization, which include pressures of operation, door sealing, vehicle-
tube interface, communication protocols and emergency evacuation [13].
Sections 3.13.5 present the results for the five physical clusters. In the analyses, each
paper is also linked to one of the five horizonal clusters. Finally, Sections 3.6 and 3.7
present an overview of research involving general discussions and Hyperloop network
developments. These last two, are not linked to the physical clusters since they focus on
discussion rather than on the development of specific technologies.
Appl. Sci. 2021,11, 5951 5 of 18
3. Hyperloop Research Breakdown
3.1. Research on the Hyperloop System
This section focuses on scientific research documents dealing with the Hyperloop
system in general. Thirty-two papers were identified from the analysis.
An overview of the issues identified in the scientific literature under the five utility
clusters is provided in Table 1.
Table 1. Issues identified in research on the Hyperloop system.
Authors Year Issue E O C A S
Tavsanoglu et al. [18] 2021 Pod to ground wireless communication X
Fernández Gago and
Collado Perez-Seoane [19]2021 Geometric design and linear infrastructure planning X
Huang et al. [20] 2021 Optical wireless communication system X
Tbaileh et al. [21] 2021
Power requirements and impact on the electricity grid
X
Han et al. [22] 2020 Wireless network architecture X
Brown et al. [23] 2020 Short-range communication X
Eichelberger et al. [24] 2020 Scheduling X
Zhang et al. [25] 2020 Pod to ground wireless communication X
Qiu et al. [26] 2020 Pod to ground wireless communication X
Jani´c [27] 2020 Energy consumption and CO2emissions X
Lafoz et al. [28] 2020 Energy Storage Systems X
Zhang et al. [29] 2020 Pod to ground wireless communication X
Khan [30] 2020 Overall system development X
Narayan S. [31] 2020 Solar panel power X
Bempah et al. [32] 2019 Photovoltaic panel configurations for tube X
Huang et al. [33] 2019 Lateral drift under different low pressures X
Jin et al. [34] 2019 Dynamic characteristics under low-pressure X
Thakur et al. [35] 2019 Braking and deceleration X
Kim and Rho [36] 2019 Support facility and pods X
Dudnikov [37] 2019 Network operations X
Allen et al. [38] 2019 Pod to ground wireless communication X
Sutton [39] 2019 Process safety and generic safety cases X
Kauzinyte et al. [40] 2019 Simulation with aerodynamic constraints X
Deng et al. [41] 2018 System simulation X
Nikolaev et al. [42] 2018 Electric and software system X
Deng et al. [43] 2017 System simulation X
Janzen [44] 2017 Dynamic characteristics under low-pressure X
Kwon et al. [45] 2017 Photovoltaic panel configurations for tube X
Ali et al. [46] 2017 Handover algorithm X
Decker et al. [47] 2017 Conceptual feasibility study X
Zhou et al. [48] 2016 Energy consumption X
Brusyanin and Vikharev [
49
]
2014 Conceptual functional safety assessment X
Abbreviations: E: Energy; O: Operations; C: Communications; A: Aerodynamics; S: Safety.
3.2. Research on Hyperloop Substructure
This section focuses on scientific research documents dealing with the Hyperloop
substructure. Eight papers were identified from the analysis.
An overview of the issues identified regarding Hyperloop substructure, under the
five utility clusters, is provided in Table 2.
Appl. Sci. 2021,11, 5951 6 of 18
Table 2. Issues identified in research on Hyperloop substructure.
Authors Year Issue E O C A S
Museros et al. [50] 2021 Structural design X
Zhao et al. [51] 2021 Vibration instability X
Ahmadi et al. [52] 2020 Dynamic bridge deck-pier interaction X
Ahmadi et al. [53] 2020 Dynamic amplification factors X
Kemp et al. [54] 2020 Floating hyperloop tunnel conceptual design X
Connolly and Costa [55] 2020 High speed dynamic load amplification X
Alexander and Kashani [56] 2018 Bridge dynamics X
Pegin et al. [57] 2018 Superstructure dynamic coefficients X
Abbreviations: E: Energy; O: Operations; C: Communications; A: Aerodynamics; S: Safety.
3.3. Research on Hyperloop Tube Structure
This section focuses on scientific research documents dealing with the Hyperloop tube
structure. Seven papers were identified from the analysis.
An overview of the issues identified in regard to Hyperloop tube structure, under the
five utility clusters, is provided in Table 3. As can be seen, the principal topic of research is
the airtightness of concrete tubes.
Table 3. Issues identified in research on Hyperloop tube structure.
Authors Year Issue E O C A S
Devkota et al. [58] 2021 Concrete tube airtightness X
Baek [59] 2020 Identification of anomalies in the tube X
Devkota and Park [60] 2019 Concrete tube airtightness X
Dudnikov [61] 2018 Concrete tube airtightness X
Devkota et al. [62] 2018 Concrete tube airtightness X
Choi et al. [63] 2016 Concrete tube airtightness X
Park et al. [64] 2015 Concrete tube airtightness X
Abbreviations: E: Energy; O: Operations; C: Communications; A: Aerodynamics; S: Safety.
3.4. Research on Hyperloop Tube-Pod Interface
This section focuses on scientific research documents dealing with the Hyperloop
tube-interface. Forty-eight papers were identified from the analysis.
An overview of the issues identified regarding the Hyperloop tube-pod interface,
under the five utility clusters, is provided in Table 4.
Table 4. Issues identified in research on Hyperloop tube-pod interface.
Authors Year Issue E O C A S
Bose and Viswanathan [65] 2021 Piston effect mitigation using airfoils X
Lluesma-R. et al. [66] 2021 Use of compressor to mitigate aerodynamic drag X
Zhou et al. [67] 2021 Radial gap and flow field X
Hu et al. [68] 2021 Cross passage and flow field X
Lluesma-R. et al. [69] 2021 Drag coefficient effect on the aerodynamic
performance X
Vakulenko et al. [70] 2021 Effect of external air exchange system X
Uddin et al. [71] 2021 Drag-based aerodynamic braking X
Huang et al. [72] 2020 Transient pressure on the tube X
Galluzzi et al. [73] 2020 Stabilization of electrodynamic levitation systems X
Nick and Sato [74] 2020 Pod structure aerodynamic optimization X
Le et al. [75] 2020 Aerodynamic drag and pressure waves X
Wang et al. [76] 2020 Blockage ratio and aerodynamic drag X
Ma et al. [77] 2020 Air pressure and aerodynamic drag X
Chen et al. [78] 2020 Structural mechanics properties of tube-wall X
Jia et al. [79] 2020 Heat recycle duct and energy accumulation X
Appl. Sci. 2021,11, 5951 7 of 18
Table 4. Cont.
Authors Year Issue E O C A S
Yang et al. [80] 2020 Blockage ratio and aerodynamic drag X
Mao et al. [81] 2020 Vacuum level and heat transfer characteristics X
Sui et al. [82] 2020 Blockage ratio and aerodynamic drag X
Machaj et al. [83] 2020 Power consumption analysis X
Zhang et al. [84] 2019 Guidance performance through curves X
Strawa et al. [85] 2019 Pod in low-pressure environment X
Nowacki et al. [86] 2019 Energy demand X
Zhang et al. [87] 2019 Aerodynamic noise X
Niu et al. [88] 2019 Aerodynamic heating X
Oh et al. [89] 2019 Aerodynamics and blockage ration X
Arun et al. [90] 2019 Conceptual aerodynamic design X
Li et al. [91] 2019 Embarking and disembarking process X
Wang and Yang [92] 2019 Electrodynamic magnetic levitation system X
Chaidez et al. [93] 2019 Levitation methods power requirements X
Jia et al. [94] 2018 Aerodynamic characteristics and pressure recycle
ducts X
Opgenoord and Caplan [95] 2018 Aerodynamic design X
Zheng et al. [96] 2018 High temperature superconducting magnetic
suspension X
Wan et al. [97] 2018 Guidance performance through curves X
Sayeed et al. [98] 2018 Magnetic levitation system prototype X
Zhang et al. [99] 2018 Levitation force X
Kang et al. [100] 2017 Aerodynamic drag parametric study X
Zhou et al. [101] 2017 Energy consumption and blockage ratio X
Braun et al. [102] 2017 Aerodynamic design multi-objective optimization X
Heaton [103] 2017 Inertial forces from earthquake X
Opgenoord and Caplan [104] 2017 Aerodynamic design and boundary layer X
Wang et al. [105] 2017 Aerodynamic design X
Zhang et al. [106] 2016 Auxiliary pumping system X
Pekardan and Alexeenko
[107]2016 Thermal lift generation and drag reduction X
Braun et al. [108] 2016 Aerodynamic design and lift generation X
Zhou et al. [109] 2015 Aerodynamics and thermal-pressure coupling X
Zhou et al. [110] 2014 Entropy and aerodynamic heat generation X
Ma et al. [111] 2014 Kinetic energy loss X
Pandey and Mukherjea [112] 2014 Aerodynamic design X
Abbreviations: E: Energy; O: Operations; C: Communications; A: Aerodynamics; S: Safety.
3.5. Research on Hyperloop Pod
This section focuses on scientific research documents dealing with the Hyperloop pod.
Twenty-seven papers were identified from the analysis.
An overview of the issues identified regarding the Hyperloop pod, under the five
utility clusters, is provided in Table 5.
Table 5. Issues identified in research on Hyperloop pod.
Authors Year Issue E O C A S
Negash et al. [113] 2021 Semi-active suspension system X
García-Tabarés et al. [114] 2021 Acceleration system based on a linear motor X
Lim et al. [115] 2020 Electrodynamic suspension X
Jayakumar et al. [116] 2020 Pod space frame X
Lim et al. [117] 2020 High-temperature superconducting (HTS) magnet X
Seo et al. [118] 2020 Propulsion/levitation/guidance LIM X
Choi et al. [119] 2019 Sub-sonic linear synchronous motor X
Guo et al. [120] 2019 Null-flux coil electrodynamic suspension structure X
Zheng et al. [121] 2019 Levitation and Linear Propulsion System X
Seo et al. [122] 2019 Propulsion/levitation/guidance LIM X
Appl. Sci. 2021,11, 5951 8 of 18
Table 5. Cont.
Authors Year Issue E O C A S
Tudor and Paolone [123] 2019 Influence of batteries to the propulsion X
Bhuiya et al. [124] 2019 Three-phase inverter for powertrain X
Naik et al. [125] 2019 Cold Gas Propulsion System X
Guo et al. [126] 2019 Electrodynamic suspension X
Cho et al. [127] 2019 Propulsion/levitation/guidance LIM X
Indraneel et al. [128] 2019 Levitation X
Soni et al. [129] 2019 Magnetic brakes X
Tudor and Paolone [130] 2019 Propulsion system and energy requirements X
Ji et al. [131] 2018 Propulsion/levitation/guidance LIM X
Abdelrahman et al. [132] 2018 Magnetic levitation X
Pradhan and Katyayan [133] 2018 Vehicle dynamics X
Klim and Hashemi [134] 2017 Vehicle wheels design X
Zhou et al. [135] 2016 Propulsion/levitation/guidance LIM X
Ma et al. [136] 2015 Electromagnetic braking X
Chin et al. [137] 2015 Pod sizing X
Zhang [138] 2014 Life support systems X
Abbreviations: E: Energy; O: Operations; C: Communications; A: Aerodynamics; S: Safety; LIM: Linear Induction Motor.
3.6. Discussion Papers on Hyperloop
This section focuses on scientific research documents that focus on general discussions.
Thirty papers were identified from the analysis.
Table 6provides an overview of the topics discussed.
Table 6. General discussion papers.
Authors Year Issue
Noland [139] 2021 Systematic technology review
Hansen [140] 2020 Technology assessment
Gieras [141] 2020 Technical/technological aspects
Sutar et al. [142] 2020 Hyperloop concept
Gkoumas and Christou [14] 2020 Policy and technical context
Barbosa [143] 2020 Technology review
Kumar et al. [144] 2019 Technical/technological aspects
Jani´c [145] 2019 Technical/technological/policy aspects
Lipusch et al. [146] 2019 Financing
Deng et al. [147] 2019 Technical/technological aspects
Bersano and Fayemi [148] 2019 Innovation management and design theory
Leibowicz [149] 2018 Technical/technological/policy aspects
van Goeverden et al. [150] 2018 Performance compared to air and high-speed train
Melzer and Zech [151] 2018 Social media
Ahmad et al. [152] 2017 Preliminary patent analysis
Kerns [153] 2017 Hyperloop competitions
Violette [154] 2017 Hyperloop competitions
Dudnikov [155] 2017 Tube and pod technical parameters
(No author name available) [156] 2017 Hyperloop competitions
Halsmer et al. [157] 2017 Hyperloop competitions
González-G. and Nogués [158] 2017 Technical/technological aspects
González-G. and Nogués [159] 2017 Technical/technological aspects
Bradley [160] 2016 Development cases
Rubin [161] 2016 Development cases
Anyszewski [162] 2016 Competitions
Ross [163] 2016 Hyperloop concept
Palacin [164] 2016 Viewpoint
Thompson [165] 2015 Social aspects
Abaffy [166] 2015 Financing
Kosowatz [167] 2014 Viability
Appl. Sci. 2021,11, 5951 9 of 18
3.7. Research on Hyperloop Networks
This section focuses on scientific research documents that focus on the development
of Hyperloop networks. Ten papers were identified from the analysis.
Table 7provides an overview of the topics discussed.
Table 7. Network papers.
Authors Year Issue
Merchant and Chankov [168] 2020 Scenario analysis in Europe
Neef et al. [169] 2020 Scenario analysis on infrastructure networks
Bertolotti and Occa [170] 2020 Agent-based model of supply chain system
Rajendran and Harper [171] 2020 Define, Measure, Analyze, Design, and Verify (DMADV) approach
Cho [172] 2019 Implications at local level
Pfoser et al. [173] 2018 Hyperloop and synchromodality
Voltes-Dorta and Becker [174] 2018 Implications at local level
Markvica et al. [175] 2018 Hyperloop impact in Europe
Schodl et al. [176] 2018 Large scale regional impact
Werner et al. [177] 2016 Implications at local level (cargo)
The relationship between vertical and decomposition clusters in the documents is
shown in the chord diagram of Figure 3. The 30 documents on Hyperloop discussions and
the 10 documents on Hyperloop network developments are excluded from the diagram.
The left part of the figure reports the utility clusters and, on the right, the physical clusters.
Visualizations of this kind highlight the most popular research topics and the relationship
between them, and help to identify research insufficiencies.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 10 of 19
Figure 3. Hyperloop academic research clusters relation overview.
As can be seen, and with regard to the physical decomposition, the majority of re-
search focuses on the pod-tube interface and aerodynamics (29 documents) and the pod
and operations (21 documents). Communication technologies were researched in nine
documents at a system level. The 21 documents focusing explicitly on safety issues, cover
all horizontal areas.
4. Initial Taxonomy of Issues
The next step was to build a preliminary taxonomy of research topics. As explained
in Section 3, all papers were read and grouped under the different clusters. Each paper
was also flagged for the respective research issues. Table 8 aggregates the findings from
the 161 documents. For the utility clusters, an overview of the emerging issues is reported,
Figure 3. Hyperloop academic research clusters relation overview.
Appl. Sci. 2021,11, 5951 10 of 18
As can be seen, and with regard to the physical decomposition, the majority of
research focuses on the pod-tube interface and aerodynamics (29 documents) and the pod
and operations (21 documents). Communication technologies were researched in nine
documents at a system level. The 21 documents focusing explicitly on safety issues, cover
all horizontal areas.
4. Initial Taxonomy of Issues
The next step was to build a preliminary taxonomy of research topics. As explained in
Section 3, all papers were read and grouped under the different clusters. Each paper was
also flagged for the respective research issues. Table 8aggregates the findings from the 161
documents. For the utility clusters, an overview of the emerging issues is reported, while
for the physical and generic clusters, the research issues are reported in detail, aggregating
the identified issues from Section 3. It should be noted that the obtained taxonomy is not
unique, and further readings could identify additional elements.
Table 8.
A taxonomy of overarching research clusters and research issues on Hyperloop arising from the scientific literature
analysis.
Research Clusters Researched Issues
Utility cluster
overview
1 Energy
Energy consumption (may include aerodynamics, but focuses on heat dissipation)
2 Safety Safety process, evacuation, pod tightness, breaking
3 Communications Pod-to-pod and pod-to-ground communication
4 Aerodynamics Aerodynamic phenomena
5 Operations Hyperloop operations and research not covered in utility clusters 1–4
Physical
clusters
A System
Optical wireless communication, pod-to-ground communication, communication
signal propagation, system simulation, functional safety, process safety, safety
cases, energy storage systems, lateral drift, energy consumption, network
architecture, scheduling, short range communication, power requirements, impact
on the electricity grid, short-range communication, scheduling, electric and
software system, photovoltaic panels, handover algorithm, geometric design,
linear infrastructure planning
B Substructure Structural design, bridge dynamics, geotechnical, earthquake, resonant dynamic
effects, vibration instability, bridge deck-pier interaction, bridge dynamics,
dynamic amplification factors, dynamic load amplification, floating Hyperloop
tunnel
C Tube Airtightness, anomaly detection
D Tube-pod interface
Levitation friction, aerodynamic drag, blockage ratio, vacuum effects, piston effect
mitigation, heat generation, tube/pod combined design, energy loss, aerodynamic
noise, levitation force, kinetic energy, pressure recycle ducts, aerodynamic
breaking
E Pod
Motor, propulsion, semi-active suspension, electrodynamic suspension, levitation,
guidance, design, sizing, battery, tightness, Linear Induction Motor,
high-temperature superconducting (HTS) magnet, batteries, wheel design,
additive manufacturing, inverter for powertrain, Cold Gas Propulsion
Generic
clusters
i Discussion
Technical feasibility, financing, policy recommendations, new mobility paradigms,
knowledge management, technology overview, education, competitions, general
feasibility
ii Network
Network feasibility, financial efficiency, network simulations, network operations,
scenario analysis, synchromodality, supply chain, regional impact
A variety of researched topics emerges from Table 8.
The Hyperloop as a system cluster (A) includes a lot of research on different opera-
tional aspects, in particular communications. In fact, this aspect appears to be challenging
at very high speeds in tunnel structures. Some other aspects related to the geometric design
and the linear infrastructure development are also covered in this cluster in an analytical
manner.
The Hyperloop substructure cluster (B) includes a great deal of research from the
fields of structural and bridge engineering. The major difference is the dynamic loads
Appl. Sci. 2021,11, 5951 11 of 18
imposed by the Hyperloop pods, which influence the design of substructure and need to
be accounted for.
Some research deficiencies were identified. This is the case for research focusing on
the Hyperloop tube cluster (C), and consequently, on infrastructure. Considering that
infrastructure costs are high (especially for a new system) the lack of research in this area
(e.g., materials, tube thickness) is visible.
At the same time, Hyperloop tube-pod interface cluster (D) research focuses on a
variety of issues linked in particular to aerodynamic performance under low pressure.
Research focusing on the Hyperloop pod cluster (E) covers many aspects that are
linked to the powertrain, suspension, magnetic levitation and guidance. A number of
similarities with high-speed rail and (especially) magnetic levitation (Maglev) trains are
apparent, something that may lead to research spillovers from the two transport modes.
Finally, the rather high number of discussion papers and those related to Hyperloop
networks highlight the overall interest in Hyperloop as a transport mode.
5. Conclusions
Hyperloop is a proposed very high-speed ground transportation system that has
great potential for the decarbonization of transportation, and it has received a great deal
of attention from transportation academics. This study aimed to provide a baseline with
regard to the topics and challenges identified in the scientific research, for the effective
testing and deployment of Hyperloop. The presentation of the issues follows a structured
methodology, and provides insights for future research. In particular, the adopted cluster-
ing is scalable, and consequently, more detailed sub-clusters could be easily identified. The
performed extensive literature review, to the authors’ knowledge, is the most complete of
its kind.
As discussed in the previous section, based on the detailed findings and the taxonomy
of issues identified under the overarching clusters, there is vast interest from the research
community on this topic.
These findings could play an important role in providing input to ongoing Hyperloop
standardization processes by looking into the different approaches for solving specific
issues. The findings also complement proprietary technologies developed by Hyperloop
promoters, since in many cases, academic research on the same topics is independent.
Therefore, it can provide a fresh perspective since academic research follows different
paths of knowledge compared to industry. This is more evident in specific clusters (e.g.,
substructure and tube) where structural engineering approaches are implemented, relying
on the long-standing expertise of researchers in the specific field.
Another possible use that emerges is the opportunity to compare the taxonomy with
research issues in legacy systems, e.g., high speed rail. In this way, it is possible to quickly
check (a) similarities in the research in the two systems, and consequently, possible research
spillovers, and (b) research issues not yet explored. The results from such an exercise could
provide valuable input to standardization and certification bodies.
The findings could ignite policy initiatives focusing on future decisions regarding
the Hyperloop. For this process to succeed, the continuous identification and assessment
of issues will be necessary, including challenges beyond technology (e.g., social aspects,
project financing), which will help to make the demonstration and deployment of Hy-
perloop possible. Outside policymaking, this paper helps academics and professionals
who are interested in the development of Hyperloop technologies by providing digested
information on scientific developments in this area.
Future research could focus on expanding this taxonomy to cover other domains of
knowledge, in particular, intellectual property applications from Hyperloop promoters
and nationally funded research.
Funding: This research received no external funding.
Informed Consent Statement: Not applicable.
Appl. Sci. 2021,11, 5951 12 of 18
Data Availability Statement: Scopus data were used in the analyses.
Acknowledgments:
Michalis Christou is acknowledged for fruitful discussion on the topic. The
views expressed here are purely those of the author and may not, under any circumstances, be
regarded as an official position of the European Commission. This research is based on data available
from or elaborated by the Joint Research Centre (JRC) TRIMIS team (the European Commission’s
Transport Research and Innovation Monitoring and Information System-https://trimis.ec.europa.eu,
accessed on 20 June 2021). The Joint Research Centre is in charge of the development of TRIMIS, and
the work has been carried out under the supervision of the Directorate-General for Mobility and
Transport (DG MOVE) and the Directorate-General for Research and Innovation (DG RTD) that are
co-leading the Strategic Transport Research and Innovation Agenda (STRIA).
Conflicts of Interest: No conflict of interest. Outside policymaking.
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... A slightly rounded composition (see Table 8) was selected by the ETF. The production data for the iron-nickel-chromium alloy 17 in ecoinvent was used as a template. The raw materials were adjusted accordingly, and the remaining flows were adopted. ...
Thesis
Full-text available
As part of a master's thesis, the life cycle assessment of an overground high-speed vacuum transport system in Switzerland was carried out. The main focus is on the construction phase and energy consumption of the transport system where four different construction scenarios were compared. Ecoinvent 3.8 was mainly used for the background system and in addition, the premise database was used, which made it possible to generate prospective models. The Foreground system was modelled with EuroTube’s cooperation. As an allocation method, the cut-off system model was used to ensure compatibility with the additional prospective data. The assessment of different impact methods was carried out using today’s Swiss electricity mix and the three other prospective electricity mixes and their predicted compositions for the year 2040. The influence of the electricity mix was further examined in a sensitivity analysis, which means that the results can also be applied to other regions. In addition, the different results were then compared with a conventional train and aircraft (with and without e-kerosene) and a sensitivity analysis of the load was carried out to increase the comparability. It turned out that electrical energy consumption, for the specific case of Switzerland, does not have the biggest impact, but it can easily turn into the main contributor with a more greenhouse gas intensive electricity mix. In contrast, the tube, or more precisely the aluminium and concrete used for it, showed the greatest impact in all scenarios. It was possible to show that the VT system's ecological impact is comparable to that of a conventional train and that there is therefore a large potential for reducing the environmental impact compared to aircraft.
... In this framework, the Hyperloop concept has been conceived as a breakthrough solution for future mobility [3]. Based on Robert Goddard's vactrain [4], it features magnetically levitated capsules traveling inside a low-pressure tube under the propulsion of linear electric motors [5]. ...
Conference Paper
The search for fast and efficient transportation systems has raised the interest in magnetic levitation technologies over the last decades. In this context, the Hyperloop concept has been conceived as a solution for future mobility. However, the stability of the electrodynamic levitation system represents a key enabling technology for the Hyperloop implementation. In this context, the state of the art has addressed the full stabilization of downscaled vehicles, where levitation and guidance are provided by electrodynamic means. This is achieved passively by introducing a proper amount of damping into the system. Nevertheless, this system stability could be affected when using permanent-magnet propulsion motors. In this perspective, we propose the stabilization of a downscaled vehicle under the influence of its propulsion system. To this end, a permanent-magnet linear synchronous motor is designed. Its stiffness contribution is evaluated and introduced into the vehicle model. Then, its impact on the stability and performance of the system is discussed in detail.
... However, existing Hyperloop tube systems and testing facilities lack full-scale tracks, which creates a hurdle for the testing and development of the Hyperloop system [14]. Several studies have made progress on the Hyperloop system in terms of theoretical analysis and numerical simulation [15,16]. Aerodynamics of the Hyperloop vehicle has been gaining momentum alongside the physics of magnetic levitation, propulsion, and evacuated tubes [17]. ...
Article
The Hyperloop is a proposed transportation system in which a high-speed vehicle travels in a near-vacuum tube. High-speed motion of an object (near Mach 1) in a confined space generates choked flow, endangering operational safety. This study investigates the physics and behaviour of choked flow in the Hyperloop system, and the corresponding law and influencing factors are theoretically analysed. A CFD method is used to simulate the compressible flow in the system. The different flow states caused by a pod travelling in the Hyperloop tube are numerically obtained, and the results concurred with the theoretical prediction. The results show that the choking strength gradually increases as the vehicle accelerates, reaching its maximum at Mach 1 and then gradually decreasing. When the blockage ratio reaches 0.4, nearly one-third of air hardly passes through the throat at most owing to the choking. The inflow velocity, choked flow density, and total pressure loss caused by the shock wave jointly affect the mass-flow limitation. In addition, the normal shock wave is the main characteristic of choked flow. The flow transitions from choked to unchoked regimes owing to the supersonic pod and forms a bow shock wave. These findings, including the equations describing the choking mechanism, can benefit various design aspects of the Hyperloop system.
... They proposed the model of the tube, capsule, compressor, suspension, and propulsion [32]. The MIT Hyperloop Team and some academic institutes competed in the SpaceX Hyperloop competition from June 2015 to January 2017 [17,33]. They did a detailed explanation of the design of the pod, the construction of the pod, and the tests that were performed-including an analysis of the competition run. ...
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High-speed capsular vehicles are firstly suggested as an idea by Elon Musk of Tesla Company. Unlike conventional high-speed trains, capsular vehicles are individual vessels carrying passengers and freight with the expected maximum speed of near 1200 [km/h] in a near-vacuum tunnel. More individual vehicle speed, dispatch, and position control in the operational aspect are expected over connected trains. This numerical study and investigation evaluate and analyze inter-distance control and their characteristics for high-speed capsular vehicles and their operational aspects. Among many aspects of operation, the inter-distance of multiple vehicles is critical toward passenger/freight flow rate and infrastructural investment. In this paper, the system’s equation, equation of the motion, and various characteristics of the system are introduced, and in particular control design parameters for inter-distance control and actuation are numerically shown. As a conclusion, (1) Inter-distance between vehicles is a function of error rate and second car start time, the magnitude range is determined by second car start time, (2) Inter-distance fluctuation rate is a function of error rate and second car start time, however; it can be minimized by choosing the correct second car start time, and (3) If the second car start time is chosen an integer number of push-down cycle time at specific velocity error rate, the inter-distance fluctuation can be zero.
... Recently, magnetically levitated ultra-high-speed ground transportation, such as Hyperloop, has attracted significant attention worldwide [1][2][3][4][5][6]. Instead of a traditional wheel-rail system that has a speed limit, noncontact magnetic levitation technologies are being used in high-speed transportation systems. ...
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Hyperloop allows for improved transportation efficiency at higher speeds and a lower power consumption. Various magnetic levitation technologies in existing high-speed maglev trains are being considered to overcome speed limitations for the development of Hyperloop, which are driven inside vacuum tubes at 1,200 km/h; and superconducting (SC) electrodynamic suspension (EDS) can provide numerous advantages to Hyperloop. such as enabling stable levitation in high-speed driving without control, and increasing the levitation air gap. However, the analysis of the EDS system requires the electromagnetic transient analysis of complex three-dimensional (3D) features, and its computational load generally limits the use of numerical methods, such as the 3D finite element method (FEM) or dynamic circuit theory; This paper presents a novel model that can rapidly and accurately calculate the frequency-dependent equivalent inductance; and it can model the EDS system with the decoupled resistance-inductance (RL) equations of levitation coils. As a design example, the levitation coils of the SC-EDS were designed and analyzed for the Hyperloop, and the results were compared with those of the FEM results to validate the model. In addition, the model was experimentally validated by measuring currents induced by moving pods.
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This article was inspired by the hyperloop technology proposed by Elon Musk, 2013. The research paper focuses on the advantage and disadvantages of implementing hyperloop in Indian cities and how this will make an impact in supply chain and logistic sector, and also in healthcare management. We discussed the implementation of Hyperloop globally (mainly focused in India). Also, it mentioned that if Hyperloop is implemented between Chennai to Bangalore, then what will be the cost of implementation and how we can achieve a breakeven point and What has changed between the current transportation system and that one? (Mainly prize and time). In this paper we discussed whether hyperloop is the right alternative means of transportation or not. KEYWORDS: Hyperloop, Virgin Hyperloop, Break-even point, high speed transportation, Supply chain, CVP analysis,
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The features of the new transportation technology-Hyperloop is analyzed in this paper. Hyperloop technology is quickly gaining traction in the group of researchers and public as it is faster than trains and aircrafts and safer than road and water transportation. Hyperloop is an ultra-fast vaccum train, which moves on air or magnetic cushion within the tubes with small internal pressure thus reducing resistance to movement. General features as well as technologies, assurance and risk factors are anatomized in the present study. It also inspects the hyperloop routes under construction in India by the Virgin Hyperloop One and Hyperloop Transportation Technology.
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Technological advancements has conceived a lot of research work in the field of transportation to make them faster, safer and economical. Hyperloop concept would be the preeminent solution that will revolutionize the mode of transportation. In this contemporary work a pod was designed and analyzed for various design iterations. The pod consists of C-shaped feet which comprises of magnets embedded in them. These feet levitate on the track consisting of electromagnets. The pod is propelled forward using an induction motor. The relative cross-section area of the tube and pod was resolved using the kantrowitz limit and was initiated that for a Mach number 0.6 the size of the tube was relatively smaller as compared to higher Mach number thus easing the economical and maintenance factor involved. The pod was them analyzed for coefficient of drag. It was assessed in a circumstance which generally endures at 10 to 12 km above sea level. It was designed according to the required aerodynamic shape and was iterated to get the optimum result.
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