LINEAR THINKING

The new Superman--The Escape ride under construction at Magic Mountain should be inaugurated by world land-speed demon Craig Breedlove, who’s still at the speed thing after 30 years. According to David Wharton’s feature (“Creating a Monster,” May 19), the ride accelerates passengers on a horizontal track and then sends them up a tower that looks as tall as City Hall for six seconds of weightlessness.

The article was confused about the propulsion technology. If, as it suggests, the ride is propelled by linear induction motors, then it is the first train in California to employ the technology under development in Japan, Germany and elsewhere to propel high-speed trains.

These motors work on the same principle as normal rotary motors, but their geometry is rearranged. In a normal motor, the armature or rotor is spun by the switching magnetic fields induced in the stator coils that surround it. In a linear induction motor, the stator coils are laid out in the track and the armature is built into the vehicle being propelled. Instead of causing the armature to spin, the stator fields cause it to move in a linear direction along the track.

Full-scale linear induction-powered trains are being tested now and one day may carry us back and forth from L.A. to San Francisco at 200 to 300 mph.

BOB SARNOFF

Transportation engineer,

Caltrans, Los Angeles