Circuits That Heal Themselves

The electronic gadgets so vital to vehicles in far-out space suffer from some far-out troubles. Cosmic radiation sickens their semiconductors. Vibrations and swift temperature changes cause fractures in all-important wires. Lubricants evaporate into the vacuum of space. But scientists are already working on some far-out cures. The latest: a tin-magnesium-aluminum alloy that can be made into wires that grow gap-bridging "whiskers" when broken and soon heal their own wounds.

When a wire containing a core of the new alloy snaps, whiskers sprout from both ends of the break. In a few days, the whiskers can bridge a gap one millimeter wide (about one twenty-fifth of an inch) and carry one watt of electrical power--enough for most of the delicate circuitry in modern spacecraft. Collision with a sizable meteoroid might result in damage too extensive for whisker therapy, admits Minneapolis-Honeywell Physicist William Jarnagin, who led the team that developed the alloy. But that hardly matters, he adds somberly. "Everything would go then."

Scientists are not sure what makes tin whiskers grow. They are slender crystals that seem to squirt out of the metal like toothpaste out of a tube. They grow fastest at 125DEG F., which is close to the temperature inside a home hi-fi set, but they grow well enough at average room temperature (70DEG), which is common in enclosed parts of spacecraft. Now a spacecraft with a faltering voice or an electronic brain that has become psychotic need not be given up for lost. Allowed a few days to grow, the little tin whiskers will make it electronically healthy.

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