The Space Condition Forecasters

People who got a good look at the sun's glowing corona during its recent eclipse may have seen faint veils of light trailing off into space. Appearing as harmless as thistledown, they were visible evidence of the sun's far-reaching violence. Stormy weather on the sun sometimes tosses out clouds of deadly particles, mostly protons, that can kill in a few minutes any humans riding in thin-walled spacecraft. So among the scientists who studied the corona were members of a new, specialized profession: solar meteorology. Their job is to learn to forecast solar weather and try to pick times when astronauts can venture safely beyond the shelter of the earth's atmosphere.

The Bright Patches. Man's first steps into space were taken during a period of comparative solar calm, but this will not last much longer. Long before 1970, when the first U.S. expeditions may be ready to start for the moon, the sun's surface will be spitting dangerous particles, following its eleven-year storm cycle. The worst of them will come from "flares," which appear suddenly as hot bright patches on the sun's surface.

The cause of flares is unknown, but they are certainly connected in some way with the strong magnetic fields that surround sunspots, which will be more numerous toward the end of the decade.

While physicists are debating the cause of the flares, practical solar meteorologists are learning to identify solar weather conditions that may produce them. First, says Dr. James Van Allen, discoverer of the Van Allen radiation belt, a sunspot must be visible. A group of several sunspots is even more likely to produce a flare, but not all do. Often they fade away without a blowoff.

Time to Dive. And not all flares, says Van Allen, shoot particles to the earth. They must be near the western edge of the sun or just beyond it. The particles do not move in straight lines like the beam of a searchlight. Affected by the sun's magnetism they move in complicated curves and may hit a spacecraft from many directions. For this reason, says Van Allen, a spacecraft cannot be sheltered by simply putting an umbrellalike shield between it and the sun.

Short range warnings of dangerous flares are fairly simple through observation of radio waves, says Dr. Helen Dodson-Prince of the University of Michigan. She can predict several hours ahead when a dangerous blast of protons will hit the earth. This warning is early enough to abort a space shot, or to tell an exposed man on the moon to dive for cover, but it is not much use for scheduling long missions. The prudent Dr. Dodson-Prince wishes that the U.S. moon push could be postponed until the next period of solar quiet, which will start around 1972.

A Real Hooper. Dr. Van Allen is more hopeful. He thinks that careful design of spacecraft, putting fuel, food, batteries and other heavy objects toward the outside as protective shields, will do much to shield astronauts against solar protons without adding much weight. In any case, he says, the peril from flares is not too great. During a 450-day period from October 1959 to February 1961, when he measured protons in space, 21 flares affected the earth. Most of them were not dangerous. But toward the end of November 1960 came three violent solar "events," one of which reached peak intensity of 46,000 protons per square centimeter per second.

This, admits Van Allen, was "a real hooper"--which would have killed or incapacitated a space team en route to the moon. The other November events were bad too, but all except five of the 450 measured days would have been safe enough for astronauts. Their reproductive organs might have been damaged, but only temporarily. So Van Allen concludes that most times are fairly favorable to schedule space voyages that do not last too long. Until solar meteorology can forecast flares with assurance, the chance of hitting a real hooper must be faced, like other perils of space.

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