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hyperloop

A Hyperloop is a proposed high-speed transportation system for both passenger and freight transport.^[1] The term was coined by Elon Musk to describe the modern open-source project originally conceived in 1799.^[2] Hyperloop designs employ three essential components: tubes, pods, and terminals.^[1] The tube is a large sealed, low-pressure system (usually a long tunnel). The pod is a coach pressurized at atmospheric pressure that runs substantially free of air resistance or friction inside this tube,^[3] using aerodynamic or magnetic propulsion. The terminal handles pod arrivals and departures.^[1]

The hyperloop has its roots in a concept by George Medhurst in 1799 and subsequently developed under the names pneumatic railway, atmospheric railway or vactrain.^[4] Elon Musk renewed interest in hyperloop after mentioning it in a 2012 speaking event.^[5] Musk further promoted the concept by publishing a white paper in August 2013, which conceived of a hyperloop route running from the Los Angeles region to the San Francisco Bay Area, roughly following the Interstate 5 corridor.^[6] His initial concept incorporated reduced-pressure tubes in which pressurized capsules ride on air bearings driven by linear induction motors and axial compressors.^[7] Transportation analysts challenged the cost estimates included in the white paper, with some predicting that a realized hyperloop would be several billion dollars over budget.^[8][9][10]

The hyperloop concept has been “open-sourced” by Musk and SpaceX, and other companies or organizations have been encouraged to freely advance the technology, preferably in collaborations.^[11] Technical University of Munich Hyperloop set the hyperloop speed record of 463 km/h (288 mph) in July 2019^[12][13] at the pod design competition hosted by SpaceX in Hawthorne, California.^[14] Virgin Hyperloop conducted the first human trial in November 2020 at its test site in Las Vegas, reaching a top speed of 172 km/h (107 mph).^[15]

History[edit]

After being conceived in 1799, the vactrain was invented in 1904 by Robert H. Goddard, a freshman at Worcester Polytechnic Institute.^[16] Goddard subsequently refined the idea in a 1906 short story called “The High-Speed Bet” which was summarized and published in a Scientific American editorial in 1909 called “The Limit of Rapid Transit”. In 1950, five years after his death, his wife Esther was granted a US patent for the vactrain.

Musk first mentioned that he was thinking about a concept for a “fifth mode of transport”, calling it the Hyperloop, in July 2012 at a PandoDaily event in Santa Monica, California. This hypothetical high-speed mode of transportation would have the following characteristics: immunity to weather, collision free, twice the speed of a plane, low power consumption, and energy storage for 24-hour operations.^[17] The name Hyperloop was chosen because it would go in a loop. Musk envisions the more advanced versions will be able to go at hypersonic speed.^[18] In May 2013, Musk likened the Hyperloop to a “cross between a Concorde and a railgun and an air hockey table”.^[19]

From late 2012 until August 2013, a group of engineers from both Tesla and SpaceX worked on the conceptual modeling of Hyperloop.^[20] An early system conceptual model was published in the Tesla and SpaceX blogs^[6][21] which describes one potential design, function, pathway, and cost of a hyperloop system.^[6] According to the alpha design, pods would accelerate to cruising speeds gradually using linear electric motors and glide above their track on air bearings through tubes above ground on columns or below ground in tunnels to avoid the dangers of grade crossings. An ideal hyperloop system will be more energy-efficient,^[22][23] quiet, and autonomous than existing modes of mass transit. Musk has also invited feedback to “see if the people can find ways to improve it”. The Hyperloop Alpha was released as an open source design.^[24] The trademark “HYPERLOOP“, applicable to “high-speed transportation of goods in tubes” was issued to SpaceX on 4 April 2017.^[25][26]

In June 2015, SpaceX announced that it would build a 1-mile-long (1.6 km) test track to be located next to SpaceX’s Hawthorne facility. The track was completed and used to test pod designs supplied by third parties in the competition.^[27][28]

By November 2015, with several commercial companies and dozens of student teams pursuing the development of Hyperloop technologies, the Wall Street Journal asserted that “The Hyperloop Movement”, as some of its unaffiliated members refer to themselves, is officially bigger than the man who started it.”^[29]

The Massachusetts Institute of Technology (MIT) Hyperloop team developed the first Hyperloop pod prototype, which they unveiled at the MIT Museum on 13 May 2016. Their design uses electrodynamic suspension for levitating and eddy current braking.^[30]

On 29 January 2017, approximately one year after phase one of the Hyperloop pod competition,^[31] the MIT Hyperloop pod demonstrated the first ever low-pressure Hyperloop run in the world.^[32] Within this first competition the Delft University team from the Netherlands achieved the highest overall competition score, winning the prize for “best overall design”.^[33][34] The award for the “fastest pod” was won by the Technical University of Munich (TUM), Germany, team WARR Hyperloop.^[35] The MIT team placed third overall in the competition, judged by SpaceX engineers.^[36]

The second Hyperloop pod competition took place from 25–27 August 2017. The only judging criterion was top speed, provided it was followed by successful deceleration. The TUM WARR Hyperloop won the competition by reaching a top speed of 324 km/h (201 mph), breaking the previous record of 310 km/h (190 mph) for Hyperloop prototypes set by Hyperloop One on their own test track.^[37][38][39]

A third Hyperloop pod competition took place in July 2018. The defending champions, the TUM WARR Hyperloop team, beat their own record with a top speed of 457 km/h (284 mph) during their run.^[40]

The fourth competition in August 2019 saw the TUM team, now known as TUM Hyperloop (by NEXT Prototypes e.V.),^[41] again winning the competition and beating their own record with a top speed of 463 km/h (288 mph).^[34]

The first passenger test of Hyperloop technology was successfully conducted by Virgin Hyperloop with two employees of the company in November 2020, where the unit reached a maximum speed of 172 km/h (107 mph). ^[42]

Theory and operation[edit]

The vactrain concept resembles a high-speed rail system without substantial air resistance by employing magnetically levitating trains in evacuated (airless) or partly evacuated tubes. However, the difficulty of maintaining a vacuum over large distances has prevented this type of system from ever being built. The Hyperloop is similar to a vactrain system but operates at approximately one millibar (100 Pa) of pressure.^[43]

Initial design concept[edit]

The Hyperloop concept operates by sending specially designed “capsules” or “pods” through a steel tube maintained at a partial vacuum. In Musk’s original concept, each capsule would float on a 0.02–0.05 in (0.5–1.3 mm) layer of air provided under pressure to air-caster “skis”, similar to how pucks are levitated above an air hockey table, while still allowing higher speeds than wheels can sustain. With rolling resistance eliminated and air resistance greatly reduced, the capsules can glide for the bulk of the journey. In the alpha design concept, an electrically driven inlet fan and axial compressor would be placed at the nose of the capsule to “actively transfer high-pressure air from the front to the rear of the vessel”, resolving the problem of air pressure building in front of the vehicle, slowing it down. A fraction of the air was to be shunted to the skis for additional pressure, augmenting that gain passively from lift due to their shape.^[6]

In the alpha-level concept, passenger-only pods were to be 7 ft 4 in (2.23 m) in diameter and were projected to reach a top speed of 760 mph (1,220 km/h) to maintain aerodynamic efficiency.^{[6] (Section 4.4)} The design proposed passengers experience a maximum inertial acceleration of 0.5 g, about 2 or 3 times that of a commercial airliner on takeoff and landing.^{[citation needed]}

Proposed routes[edit]

A number of routes have been proposed for Hyperloop systems that meet the approximate distance conditions for which a Hyperloop is hypothesized to provide improved transport times (distances of under approximately 1,500 kilometres (930 miles)).^[44] Route proposals range from speculation described in company releases to business cases to signed agreements.

United States[edit]

The route suggested in the 2013 alpha-level design document was from the Greater Los Angeles Area to the San Francisco Bay Area. That conceptual system would begin around Sylmar, just south of the Tejon Pass, follow Interstate 5 to the north, and arrive near Hayward on the east side of San Francisco Bay. Several proposed branches were also shown in the design document, including Sacramento, Anaheim, San Diego, and Las Vegas.^[6]

No work has been done on the route proposed in Musk’s alpha-design; one cited reason is that it would terminate on the fringes of the two major metropolitan areas (Los Angeles and San Francisco), resulting in significant cost savings in construction, but requiring that passengers traveling to and from Downtown Los Angeles and San Francisco, and any other community beyond Sylmar and Hayward, to transfer to another transportation mode in order to reach their final destination. This would significantly lengthen the total travel time to those destinations.^[45]

A similar problem already affects present-day air travel, where on short routes (like LAX–SFO) the flight time is only a rather small part of door to door travel time. Critics have argued that this would significantly reduce the proposed cost and/or time savings of Hyperloop as compared to the California High-Speed Rail project that will serve downtown stations in both San Francisco and Los Angeles.^[46][47][48] Passengers traveling from financial center to financial center are estimated to save about two hours by taking the Hyperloop instead of driving the whole distance.^[49]

Others questioned the cost projections for the suggested California route. Some transportation engineers argued in 2013 that they found the alpha-level design cost estimates unrealistically low given the scale of construction and reliance on unproven technology. The technological and economic feasibility of the idea is unproven and a subject of significant debate.^{[8][9][10][45]}

In November 2017, Arrivo announced a concept for a maglev automobile transport system from Aurora, Colorado to Denver International Airport, the first leg of a system from downtown Denver.^[50] Its contract described potential completion of a first leg in 2021. In February 2018, Hyperloop Transportation Technologies announced a similar plan for a loop connecting Chicago and Cleveland and a loop connecting Washington and New York City.^[51]

In 2018 the Missouri Hyperloop Coalition was formed between Virgin Hyperloop One, the University of Missouri, and engineering firm Black & Veatch to study a proposed route connecting St. Louis, Columbia, and Kansas City.^[52][53]

On 19 December 2018, Elon Musk unveiled a 2-mile (3 km) tunnel below Los Angeles. In the presentation, a Tesla Model X drove in a tunnel on the predefined track (rather than in a low-pressure tube). According to Musk the costs for the system are US$10 million.^[54] Musk said: “The Loop is a stepping stone toward Hyperloop. The Loop is for transport within a city. Hyperloop is for transport between cities, and that would go much faster than 150 mph.”^[55]

The Northeast Ohio Areawide Coordinating Agency, or NOACA, partnered with Hyperloop Transportation Technologies^[when?] to conduct a $1.3 million feasibility study for developing a Hyperloop corridor route from Chicago to Cleveland and Pittsburgh for America’s first multistate hyperloop system in the Great Lakes Megaregion. Hundreds of thousands of dollars already have been committed to the project. NOACA’s Board of Directors has awarded a $550,029 contract to Transportation Economics & Management Systems, Inc. (TEMS) for the Great Lakes Hyperloop Feasibility Study to evaluate the feasibility of an ultra-high-speed Hyperloop passenger and freight transport system initially linking Cleveland and Chicago.^{[56][full citation needed]}

India[edit]

Hyperloop Transportation Technologies were considering in 2016 with the Indian Government for a proposed route between Chennai and Bengaluru, with a conceptual travel time for 345 km (214 mi) of 30 minutes.^[57] HTT also signed an agreement with Andhra Pradesh government to build India‘s first Hyperloop project connecting Amaravathi to Vijayawada in a 6-minute ride.^[58]

On 22 February 2018, Hyperloop One entered into a memorandum of understanding with the Government of Maharashtra to build a hyperloop transportation system between Mumbai and Pune that would cut the travel time from the current 180 minutes to 20 minutes.^[59][60]

Indore-based Dinclix GroundWorks’ DGWHyperloop advocates a Hyperloop corridor between Mumbai and Delhi, via Indore, Kota, and Jaipur.^[61]

Elsewhere in the world[edit]

Many of the active Hyperloop routes that have been considered are outside of the U.S. In 2016, Hyperloop One published the world’s first detailed business case for a 300-mile (500 km) route between Helsinki and Stockholm, which would tunnel under the Baltic Sea to connect the two capitals in under 30 minutes.^[62] Hyperloop One undertook a feasibility study with DP World to move containers from its Port of Jebel Ali in Dubai.^[63] In late 2016, Hyperloop One announced a feasibility study with Dubai’s Roads and Transport Authority for passenger and freight routes connecting Dubai with the greater United Arab Emirates. Hyperloop One was also considering passenger routes in Moscow during 2016,^[64] and a cargo Hyperloop to connect Hunchun in north-eastern China to the Port of Zarubino, near Vladivostok and the North Korean border on Russia’s Far East.^[65] In May 2016, Hyperloop One kicked off their Global Challenge with a call for comprehensive proposals of hyperloop networks around the world.^[66] In September 2017, Hyperloop One selected 10 routes from 35 of the strongest proposals: Toronto–Montreal, Cheyenne–Denver–Pueblo, Miami–Orlando, Dallas–Laredo–Houston, Chicago–Columbus–Pittsburgh, Mexico City–Guadalajara, Edinburgh–London, Glasgow–Liverpool, Bengaluru–Chennai, and Mumbai–Chennai.^[67][68]

Others have put forward European routes, including a route beginning at Amsterdam or Schiphol to Frankfurt.^[69][70][71] In 2016, a Warsaw University of Technology team began evaluating potential routes from Cracow to Gdańsk across Poland proposed by Hyper Poland.^[72]

TransPod explored the possibility of Hyperloop routes which would connect Toronto and Montreal,^[73][74] Toronto to Windsor,^[75] and Calgary to Edmonton.^[76] Toronto and Montreal, the largest cities in Canada, are currently connected by Ontario Highway 401, the busiest highway in North America.^[77] In March 2019, Transport Canada commissioned the study of the Hyperloop, so it can be “better informed on the technical, operational, economic, safety, and regulatory aspects of the Hyperloop and understand its construction requirements and commercial feasibility.”^[78]

Hyperloop Transportation Technologies (HTT) reportedly signed an agreement with the government of Slovakia in March 2016 to perform impact studies, with potential links between Bratislava, Vienna, and Budapest, but there have been no further developments.^[79] In January 2017, HTT signed an agreement to explore the route Bratislava—Brno—Prague in Central Europe.^[80]

In 2017, SINTEF, the largest independent research organization in Scandinavia, announced they were considering building a test lab for Hyperloop in Norway.^[81]

An agreement was signed in June 2017 to co-develop a Hyperloop line between Seoul and Busan in South Korea.^[82][83]

Mars[edit]

According to Musk, Hyperloop would be useful on Mars as no tubes would be needed because Mars’ atmosphere is about 1% the density of the Earth’s at sea level.^{[84][18][85][86]} For the Hyperloop concept to work on Earth, low-pressure tubes are required to reduce air resistance. However, if they were to be built on Mars, the lower air resistance would allow a Hyperloop to be created with no tube, only a track, and so would be just a magnetically levitating train.^[87]

Open-source design evolution[edit]

In September 2013, Ansys Corporation ran computational fluid dynamics simulations to model the aerodynamics of the capsule and shear stress forces that the capsule would be subjected to. The simulation showed that the capsule design would need to be significantly reshaped to avoid creating supersonic airflow, and that the gap between the tube wall and capsule would need to be larger. Ansys employee Sandeep Sovani said the simulation showed that Hyperloop has challenges but that he is convinced it is feasible.^[88][89]

In October 2013, the development team of the OpenMDAO software framework released an unfinished, conceptual open-source model of parts of the Hyperloop’s propulsion system. The team asserted that the model demonstrated the concept’s feasibility, although the tube would need to be 13 feet (4 m) in diameter,^[90] significantly larger than originally projected. However, the team’s model is not a true working model of the propulsion system, as it did not account for a wide range of technical factors required to physically construct a Hyperloop based on Musk’s concept, and in particular had no significant estimations of component weight.^[91]

In November 2013, MathWorks analyzed the proposal’s suggested route and concluded that the route was mainly feasible. The analysis focused on the acceleration experienced by passengers and the necessary deviations from public roads in order to keep the accelerations reasonable; it did highlight that maintaining a trajectory along I-580 east of San Francisco at the planned speeds was not possible without significant deviation into heavily populated areas.^[92]

In January 2015, a paper based on the NASA OpenMDAO open-source model reiterated the need for a larger diameter tube and a reduced cruise speed closer to Mach 0.85. It recommended removing on-board heat exchangers based on thermal models of the interactions between the compressor cycle, tube, and ambient environment. The compression cycle would only contribute 5% of the heat added to the tube, with 95% of the heat attributed to radiation and convection into the tube. The weight and volume penalty of on-board heat exchangers would not be worth the minor benefit, and regardless the steady-state temperature in the tube would only reach 30–40 °F (17–22 °C) above ambient temperature.^[93]

According to Musk, various aspects of the Hyperloop have technology applications to other Musk interests, including surface transportation on Mars and electric jet propulsion.^[94][95]

Researchers associated with MIT’s department of Aeronautics and Astronautics published research in June 2017 that verified the challenge of aerodynamic design near the Kantrowitz limit that had been theorized in the original SpaceX Alpha-design concept released in 2013.^[96]

In 2017, Dr. Richard Geddes and others formed the Hyperloop Advanced Research Partnership to act as a clearinghouse of Hyperloop public domain reports and data.^[97]

In February 2020, Hardt Hyperloop, Hyper Poland, TransPod and Zeleros formed a consortium to drive standardisation efforts, as part of a joint technical committee (JTC20) set up by European standards bodies CEN and CENELEC to develop common standards aimed at ensuring the safety and interoperability of infrastructure, rolling stock, signalling and other systems.^[98]