MAGLEV REVISITED

Magnetic levitation or Maglev [AtE Mar 74, Jan 86, May 88] is applied to wheelless trains floating above a track at speeds of more than 300 mph. The upward force is provided by superconducting magnets which repel the train from the guiding rails (or use a hook-like structure which is attracted upwards toward them); the forward force is furnished by a running field preceding the train, much like a motor whose poles and armature are laid out flat rather than cylindrically.

The accident happened only a week before the Office of Tech-nology Assessment (a congressional institution, but nevertheless often very good) issued its report "New Ways: tiltrotor aircraft and magnetically levitated vehicles," aimed primarily at fast transpor-tation between cities and their airports and in crowded urban cor-ridors. The US has had maglev trains on experimental tracks for 10 years and they are now technically feasible; but their commercial realization is unlikely for some 10 more years due to difficulty in financing, the absence of safety regulations, and local community objections.

Unlike maglev, where Germany and Japan appear to be the leaders, the US has a lead of about 5-year in another technology that could compete with maglev, tiltrotor aircraft. Their engines can be swiveled so that the plane of propeller rotation is either ver-tical or horizontal. Turning the engines upwards, the plane can take off vertically like a helicopter, and turning them forward it be-comes a regular forward-thrust airplane.

Though the report naturally pushes federal financing and big government, it is well illustrated and its technical parts are quite readable and very informative.

[More: "Maglev burns out in Japan," Nature 10/17,"New Ways: tiltrotor aircraft and magnetically levitated vehicles," $3.75 from Govt. Printg. Off., Washington, DC 20402; stock no. 052-003-01256-1.]