Science: Shields for Space

Despite all the heady talk about sending men into space in the not too distant future, many a practical problem remains far from solution. One of the most formidable : protecting space travelers from the deadly radiation that will swarm about them.

This week General Electric Engineer Norris F. Dow, reporting his findings in Aero/Space Engineering, considered the difficulties of providing radiation shielding for spacemen—and found them immense.

When an inhabited satellite orbits 2,200 miles above the earth, its crew will be riddled by the fast-moving protons of the inner Van Allen radiation belt. If unshielded, the spacemen will be inflicted with about 3,000 rem (the unit of radiation effect on human tissue) per week many times more than a lethal dose. Even if the satellite stays below the Van Allen radiation, its crew may still be in peril.

Flares (intense disturbances) on the sun often shoot high-energy protons all the way to earth. During the period July 10-18, 1959. for example, protons from a sun flare would have given spacemen a deadly dose of radiation during each day of orbiting.

Shielding can be used to protect the spacemen, but Dow estimated that 100 lbs. of lead per sq. ft. will be required to keep Van Allen or flare radiation at a safe level. That figures at no less than 11,000 Ibs.—more than the total weight of the heaviest satellite yet put into orbit, the U.S.S.R.'s Sputnik III—for shielding in a cramped, man-carrying capsule only six feet in diameter. Dow conceded that better shielding materials than lead may be found. But he saw little chance that the light and roomy satellite stations so dear to space enthusiasts can be made radiation-safe—at least not for a long while.