Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Sustainable Energy

Train in a Tube

Decades before talk of a Hyperloop, a transportation researcher wondered whether “evacuated tube” ground transport would be worth the trouble.

  • June 21, 2016

"Even though trains have traveled over 200 mph under test conditions, it is still a very ticklish business to run regular passenger service at speeds greater than 150 mph.

Many of the problems of the railroad can be traced to the high concentrations of force which occur at the point of contact with the rail. The Tracked Air Cushion Vehicle avoids this by spreading the suspension force over a large area. Pressurized air is fed into a cushion region, from which it escapes through a small gap between the cushion lip and the guideway.

Henry Kohm and Richard Thornton of MIT have described a vehicle which utilizes magnetic repulsion to levitate at speeds of 300 mph or greater. The vehicle uses wheels at low speeds, and the guideway is shaped like a semi-circular trough so the vehicle can bank like a toboggan through turns.

This story is part of our July/August 2016 Issue
See the rest of the issue
Subscribe

The large magnetic field which is the essential feature of this concept is not without its difficulties. Some form of magnetic shielding is necessary to protect the passengers, and steel in the guideway causes problems because of the resulting attractive force at low speeds. Concrete also introduces difficulties since it enters a corrosive reaction with the aluminum levitation surface. The civil engineers designing the guideway must therefore work with special considerations regarding building materials, which is bound to increase the eventual cost.

The only advantage to magnetic repulsion is that it can operate in an evacuated tube. However, the difficulties of such an operation are formidable. Rather dramatic and unforeseen reductions in the cost of tunneling and maintaining an evacuated environment are required before investments in this concept of transportation can be justified.

The probability is quite high that the suspension systems mentioned here are technically feasible. Economic feasibility, however, is the more important question and the one which will eventually decide which scheme is preferable. Determination of this issue will be one of the more fascinating technological, sociological, and economic topics of the next decade.”

Excerpted from “Suspension Concepts for High-Speed Ground Transportation,” by Timothy M. Barrows of the U.S. Department of Transportation, from the July/August 1975 issue of Technology Review.

Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?

Go behind the scenes and check out our video
More from Sustainable Energy

Can we sustainably provide food, water, and energy to a growing population during a climate crisis?

Want more award-winning journalism? Subscribe and become an Insider.
  • Insider Plus {! insider.prices.plus !}* Best Value

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus the digital magazine, extensive archive, ad-free web experience, and discounts to partner offerings and MIT Technology Review events.

    See details+

    Print + Digital Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

    Technology Review PDF magazine archive, including articles, images, and covers dating back to 1899

    10% Discount to MIT Technology Review events and MIT Press

    Ad-free website experience

  • Insider Basic {! insider.prices.basic !}*

    {! insider.display.menuOptionsLabel !}

    Six issues of our award winning print magazine, unlimited online access plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Print Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

  • Insider Online Only {! insider.prices.online !}*

    {! insider.display.menuOptionsLabel !}

    Unlimited online access including articles and video, plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.