An Introduction to High Speed Rail
Estimated Reading Time: 7 minutes
TL;DR
Today we provide a quick overview of high speed rail systems. As we learned in our subscriber post for the week, high speed rail has grown explosively in the PRC (People’s Republic of China) over the last decade and has achieved significant adoption in Europe, but not yet in the US. Today, we provide a quick introduction to some of the science of high speed rail operation and discuss some newly proposed technologies such as hyperloops.
Wheeled High Speed Rail
Commercial high speed rail systems today can be broadly divided into two categories: wheeled and magnetic levitation. Wheeled high speed rail systems use traditional tracks combined with powerful electric motors and streamlined carriages to achieve high speed transit. There are varying definitions of when a train is high speed, but one definition suggests that rains that achieve speeds of at least 124 mph on legacy tracks and 155 mph on custom tracks should be considered high speed (source). Most high speed rail systems, such as the under construction California High Speed Rail use wheeled high speed trains.
An Introduction to Maglev
Maglev (short for magnetic levitation) uses high powered magnets to levitate trains. These magnetic levitation systems offer the powerful advantage of reduced friction but brings along a number of complex technical challenges. As the diagrams below show, the two major types of maglev systems are electromagnetic suspension and electrodynamic suspension systems which use different configurations of magnets. Maglev brings some additional safety challenges, since some maglev systems only levitate trains that are in motion at sufficient speeds, so trains need robust power failure handling mechanics. Despite these challenges, maglev trains have started to find increased adoption worldwide in the last few years.
Maglev systems have powerful advantages such as reduced wear-and-tear and increased robustness to weather conditions, but have the powerful drawback of requiring custom tracks that are not usable by non-maglev trains (source). The current world speed record for a maglev train is 374 mph on a test track (source).
How About Hyperloop?
The Hyperloop is a concept proposed by Elon Musk which uses low pressure air tubes to allow for very high speed trains (see diagram below). Musk envisions these trains being able to eventually travel at hypersonic speeds, inspiring the use of “hyper” in the name (source). The hyperloop builds on earlier proposals for vactrains, which proposed running maglev trains within low pressure air tubes. A number of proof of concept systems have been built with the first small scale passenger test completed in November 2020 (source).
The hyperloop concept has gathered broad interest given Musk’s past technological achievements with SpaceX and Tesla and the powerful notion that rail systems could eventually travel at extremely high speeds. At the same time, hyperloop systems are far from broad commercial usage and will require major technological development. For one, safety considerations for the hyperloop will likely be formidable, requiring automatic repressurization of tracks in emergencies. Another challenge is enabling safe exit for passengers in case of power failures. Hyperloop tracks will also face new maintenance and safety challenges since large networks of low pressure tubes have not been built or maintained safely in the past.
Discussion
As we learned in Tuesday’s subscriber post, the PRC (People’s Republic of China) has built over 23,500 miles of high speed rail as of December 2020, more than two-thirds of global high speed rail (source). In contrast, US high speed rail efforts have moved fitfully at best with the California High Speed Rail under construction for years and still far from commercial readiness (source). What explains the difference? One possibility is that authoritarian powers like the PRC face far fewer legal challenges to finding land for large infrastructure projects since court systems do not allow residents to raise major protests. In contrast, the California High Speed Rail has faced a host of legal challenges (source). Another challenge is that the US has lower population density by far than China or even the EU, raising concerns that ridership for the California High Speed Rail may be too low for sustainability (source).
Another major challenge for the California effort has been budget. In 2008, the project was initially projected to have a total price tag of $40 billion, while even the first of multiple phases is currently projected to cost over $77 billion (source). The world bank estimated that the California high speed rail will likely cost over $56 million / kilometer while PRC high speed rail projects typically cost $17-21 million / kilometer and European projects cost $25-39 million / kilometer. What explains the dramatic difference in costs? One issue is land acquisition is considerably trickier in the US than in China, but EU countries also have lower costs while also being democratic. One possibility is economies of scale. Both US companies and government lack experience implementing high speed rail systems, likely leading to inefficiencies that more seasoned transit agencies in the PRC and EU have removed. PRC rail operators have also come up with design innovations such as standardizing construction elements that the US should learn from and copy (source).
President Biden’s proposed $2 trillion infrastructure package includes $80 billion for modernizing and expanding the US’s high speed rail infrastructure (source). Amtrak has released a speculative map (see below) of a country wide rail network that has garnered broad public interest. At the same time, critics note that air travel in the US is much cheaper than in countries that have large high speed rail networks and worry that high speed rail could be a massive boondoggle (source).
While it’s not yet clear what the right tradeoff between improved airports and expanded high speed rail should be, high speed rail networks could offer a powerful boost to American transit, especially for densely populated zones. In a more geopolitically competitive sense, allowing the PRC to develop world class expertise in an important technological area is likely not healthy for the US in the long run either.
Highlights for the Week
https://spectrum.ieee.org/tech-talk/computing/hardware/heres-how-googles-tpu-v4-ai-chip-stacked-up-in-training-tests: Google has released TPUv4, with 4096 processor TPU pods achieving an exaflop in total compute capability!
https://www.anandtech.com/show/16690/nvidia-to-extend-ethereum-throttle-to-geforce-rtx-3080-3070-3060-ti-lhr-cards: Ethereum’s soaring price has led to GPU shortages, prompting Nvidia to attempt to throttle GPU mining on its cards.
https://blog.google/technology/ai/unveiling-our-new-quantum-ai-campus/: Google has launched a new Quantum AI campus in Santa Barbara with the goal of building a practical quantum computer with 1,000,000 physical qubits and robust quantum error correction.
https://www.nytimes.com/2021/05/17/technology/apple-china-censorship-data.html: Apple has made serious compromises to its values in order to continue operating in China. Making profits in the PRC seems to require companies to compromise their ethical standards.
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About
Deep Into the Forest is a newsletter by Deep Forest Sciences, Inc. We’re a deep tech R&D company specializing in the use of AI for deep tech development. We do technical consulting and joint development partnerships with deep tech firms. Get in touch with us at partnerships@deepforestsci.com! We’re always welcome to new ideas!
Credits
Author: Bharath Ramsundar, Ph.D.
Editor: Sandya Subramanian