Introduction
The Hyperloop is a transportation system (high speed) that accelerates high-speed pods through a low-pressure tube. The core idea behind this concept is to achieve the highest maximum speed of almost the speed of sound. Creating this system provides a fast and cost-effective traveling mode between cities with around 900 miles. Elon Musk conceptualized this convenient model in 2012. Elon Musk is a leasing tech entrepreneur owning and heading several companies (high profile) such as Tesla Motors and Space X.
Some of the hypothetical benefits of Hyperloop technology are energy generation for its operations, low power requirements, rapid speed, lack of crashes, and immunity to weather, to mention a few (Gray, 2013, p. 1). Both building and designing the Hyperloop face several economic and technical challenges. Across the United States, a team of around 100 engineers by 2016 completed a technical feasibility study. This study assessed if it was realistic to venture into the technology from an engineering point of view. Elon Musk estimated that implementing an Hyperloop version (full passenger-plus-cargo) would cost around USD 7.5 billion. Critics argue that the project’s final cost could cost around ten times more.
The Concept and Design of the Hyperloop
After the 2012 initial proposal by Elon Musk, engineers from both Tesla Motors and SpaceX worked together informally for almost a year (around nine months). They were working to create a reasonable Hyperloop cost assessment and engineering proposal. The proposal was released in 2013 August. Hyperloop operations are copied from a railgun and the Concorde supersonic jet. The railgun employs the principles of electrodynamics to accelerate projectile with supersonic speeds (Abdelrahman, Sayeed and Youssef, 2017, p. 7429). The hyperloop also employs the air hockey table principle, which creates minute air bearings that act as a cushion to enable objects to move with minute friction. The original proposal by Elon Musk suggested the LA (Los Angeles) to San Fransico route, which could be taking around 35 minutes. The route takes 1 hour with a plane and 5 hours when using a vehicle. Along the track will be mounted solar panels, which will provide the energy used in accelerating and maintaining the speed of the Hyperloop.
By 2016, two major competing companies came up with different proposals of bringing the reality of the concept of designing the Hyperloop. The first company was a classic tech startup, the Hyperloop Technologies, and it had venture funds of around $37Million, 72 employees, and industrial-chic office and venture. A worldwide consortium, Hyperloop Transportation Technologies was the second company with 450 entrepreneurs, engineers, and scientists working part-time to exchange the company’s equity. Each of these two companies explored different routes of proposing the track of the Hyperloop. The first proposal was investigating Los Angeles (LA)- Las Vegas route. The other proposal announced the plans of constructing a partial track on the LA-San Francisco route as proposed by the first proposal. The representatives of the two firms argued that there was a great possibility of implementing the Hyperloop in the Middle East or Asia because of the increased need for fast and efficient transport and reduced bureaucracy in the region than in the United States.
Space X company, owned by Elon Musk, announced an open competition for independent engineering teams and university students to develop the best design and build the most effective and efficient Hyperloop pod. More than 120 teams participated in the competition, which was targeted to select the best finalist. The finalist would test and build pods at the headquarters of space X in the 2016 summer. The idea of this aspect was to create the best final design, which would be selected to be used for commercial purposes. On 2016 January 30th, a team of MIT graduate students won the competition (first stage). They created an innovative pod that employed the design of utilizing magnetic levitation other than using air cushioning to reduce the friction of the pods.
Hyperloop is considered one of the major anticipations that will provide a carbon-neutral and faster way of connecting cities. Indeed, the vision of the Hyperloop systems visions to run effectively with renewable energies (exclusively). It is argued that the hyperloop system will have the capabilities of producing more energy than it will be consuming. The propositions of installing solar panels outside the Hyperloop tube will have chargeable batteries that will store the energy used during the night. The companies that will build the Hyperloop system will consider constructing elevated tracks on the major road medians (Musk, 2013, p. 2). The elevated tracks will also be constructed on existing railway lines to reduce the construction impacts, which can affect people living nearby, natural spaces, and ecosystems. The system can be built below or above the ground. The building above the ground will be done in those areas where land prices are cheap, and there are no obstacles. Tunneling will be a feasible option where the community is dense and more developed, such as the United Kingdom. Tunnels will be constructed in those areas where it will not be possible to clear the densely built-up areas.
Physics (Science) of the Hyperloop
The design of the Hyperloop must overcome several technical challenges with the core aim of achieving desirable speeds cost-effectively. The design must also ensure that all advantages are achieved without risking human health and life. As a result, several solutions provide the challenges presented in the “alpha” proposal in 2013 by Elon Musk. Linear induction series of motors would be employed in the Hyperloop pod to achieve the proposed Los Angeles-San Francisco 35 minutes trip to accelerate the pod to nearly the speed of sound (approximately 760 miles/hour).
The principle of the Linear Induction Motor Series
This principle is the same as that applied by the induction motors. In this case, variant magnetic fields (space-time) is produced by the primary parts in the air gap where the secondary part induces the EMF (electromotive part) conducting sheet. Eddy currents are generated by the electromotive force, which interacts with the flux in the air gap to generate Lorenz’s force (thrust). The two common types of linear induction motors include the short primary type (SP) and the Long Primary Type (LP) (Lee, Kim and Lee, 2006. P. 1921) The Short Primary Type uses the conducting sheets on the guideway and stator coils on board. On the other side, the Long Primary Type has conducting sheets on board while the stator coils are on the guideway. The core advantage of the short primary type is that it reduces construction costs because it is easier to lay the guideway with aluminum sheets. The main disadvantage with this type is that it has an end effect that causes leakage inductance and drags force, making the system have low energy efficiency.
Levitation
For the pods to accelerate with approximately 760 miles in an hour, there is supposed to be some way of alleviating friction forces between the tube and the pod. Indeed, magnetic levitation is one of the possible mechanisms. In this case, very large permanent magnets would be employed in suspending the pod between the top and the bottom of the tube (Ji et al. 2018, p.2). Indeed, this idea was dismissed by Elon Musk at the beginning of the proposal because of the cost of the idea. The other second method of alleviating the forces of friction between the tube and the pod was using the air bearings, which are employed an air hockey table. The air hockey table eliminates the rolling resistance by using the cushioning by air when supporting the pods.
Propelling the Pods through a Vacuum Hyperloop Tube
The other scientific challenge facing the Hyperloop is reducing the large friction caused by air when the hyperloop is moving through the tube. Indeed, this aspect is supposed to be reduced to attain the aspect of high-speed transportation. In this case, one of the possible ways of reducing the air resistance was propelling the pods through a vacuum tube. This idea of creating a vacuum has different shortcomings. One of them is that the concept would be very expensive. The pumps which can be used in creating the vacuum inside the tube are extremely costly. The other significant shortcoming is that any malfunction of the equipment utilizing this concept would cause devastating to the operations of the Hyperloop. Indeed, this problem can be addressed by proposing the Hyperloop tube to operate with 1/6 of the atmosphere of Mars (very low pressure) of about 100 Pascals. Notably, a pressure of 100 Pascals (1000 times less) than the sea-level atmospheric pressure. In this condition, air resistance is reduced drastically. Indeed, this reduced pressure means that after the initial acceleration, the pods can move in the tube without any thrust until they reach their destination after the journey ends.
Aerodynamics
Designing the pods with aerodynamics is vital even when the Hyperloop tubes operate at very low pressure. In addition, the material costs should be kept down, which implies that the area of the cross-section of both the Hyperloop pod and Hyperloop tube should be very close to each other. The walls of the pod should be very close to the walls of the tube. When the walls are close to each other, the pod operates like a syringe (Sui et al. 2021., p.121427). This aspect means that it pushes the entire air column in the front when it is moving instead of allowing air to move around it. Because the tube is very long (hundreds of miles), the effect would be playing a vital role in enabling the pod to throttle with the maximum speed inside the tube. In this case, the Kantrowitz limit is the maximum speed that can be achieved by a pod of a specific crossectional area to move inside a tube. Overcoming this issue would mean that an ideal pod should be created.
Attaining Kantrowitz limit
The building of an ideal pod to attain the Kantrowitz limit means to engineer an ideal pod by fixing the pod’s nose with an electric compressor fan. The fan will be playing a vital role in pumping the high-pressure air from the front part of the pod to behind. Indeed, pumping air below the pod will be functioning as an air cushion hence serving the purpose of an “air hockey table.” It is a concept that would create the air-cushion suspension effect. In addition, according to Elon Musk, the design Hyperloop will be designed such that the passengers experience a 0.5g inertial acceleration (maximum). This inertial acceleration is 2-3 times that experienced by passengers in a jet when taking off and also when landing. It will only be achieved when the Hyperloop functions effectively. Notably, the pod’s design which will be used in the Hyperloop, is not yet finished. As a result, the precise science (physics) of the tech which will be used in addressing aerodynamics, reducing friction, and acceleration of the pod concerns are still underway and hence being a subject of change.
Practicality
Elon Musk suggested that the practicality of transporting 7.4 million a year would mean that the system will operate 12 hours a day, where a capsule has to depart after every one minute. In addition, the Hyperloop transport system would require airport security protocol. This aspect implicates that the system will also face inevitable technical hitches that will lead to delays. As a result, these hitches can drastically reduce the number of people traveling with the system. In addition, the system will also have peak times when commuters are returning home from work and when they are reporting to work. Sometimes, the transport system will be quiet and busy during peak times. The chances of transporting the maximum number of people during the peak times. Comparing the cost of the High-Speed Rail link between the two cities and the cost of the Hyperloop system shows that the Hyperloop system will be more economical and fulfill the transport needs. Several Hyperloops can be constructed to meet the transport demand of the passengers between Los Angeles and San Francisco.
Bibliography
Abdelrahman, A.S., Sayeed, J. and Youssef, M.Z., 2017. Hyperloop transportation system: analysis, design, control, and implementation. IEEE Transactions On Industrial Electronics, 65(9), pp.7427-7436.
Gray, R. 2013. The Hyperloop: flawed fantasy or achievable challenge. The Telegraph Online, Technology News, pp. 3.
Ji, W.Y., Jeong, G., Park, C.B., Jo, I.H. and Lee, H.W., 2018. A study of non-symmetric double-sided linear induction motor for Hyperloop All-In-One System (propulsion, levitation, and guidance). IEEE Transactions on Magnetics, 54(11), pp.1-4.
Lee, H.W., Kim, K.C. and Lee, J., 2006. Review of maglev train technologies. IEEE transactions on magnetics, 42(7), pp.1917-1925.
Musk, E. 2013. Hyperloop Alpha. Hyperloop Alpha Proposal, Tesla Motors, pp. 3.
Sui, Y., Niu, J., Yu, Q., Yuan, Y., Cao, X. and Yang, X., 2021. Numerical analysis of the aerothermodynamic behavior of an Hyperloop in choked flow. Energy, 237, p.121427.