Magnetic Cooling

Missiles and spaceships may some day carry magnets to keep their noses cool when they plunge into the atmosphere. Dr. Joseph L. Neuringer of Republic Aviation Corp. has already worked out a system of magnetohydrodynamic for hydromagnetic) insulation.

When a re-entry body hits the atmosphere at 13,000 m.p.h.. a shock wave forms a few inches ahead of it. Between the wave and the body is a fast-flowing layer of air heated to something like 12,000DEG F. At this temperature about 2% of the air's atoms are ionized, i.e., broken into electrons and positively charged ions. The mixture, which physicists call a plasma, is a conductor of electricity.

When any conductor, either a wire or an ionized gas. is pushed across a magnetic field, two things happen: 1) an electric current flows through the conductor and 2) the conductor meets resistance and therefore slows down. Physicist Neuringer's proposal is to create a strong magnetic field on the front surface of the re-entry body. When ionized air flows across it, the braking action of the magnetism will make it pile up in a deeper, slower moving layer that will not transfer as much heat to the solid surface.

Neuringer figures that a magnetic field of moderate strength (3,000 gauss) should reduce heat transfer by 28%. Greater reduction might be achieved by covering the nose of the re-entry body with a material that ionizes easily. Its ions, mixing with the air, would make it a strongly conducting plasma that would be slowed more effectively by magnetism.

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