The Heat-Resisters

The friction-heated cockpit of a high-speed airplane has to be cooled elaborately to keep the pilot alive. If the pilot is taken out, and the craft becomes an unmanned missile, its interior must still be cooled to keep its electronic brain from dying of heat prostration. So, decided General Electric Co., heatproof electronic components should prove useful in the missile business. This week, after years of work, it showed whole electronic assemblies working efficiently, though red-hot in a glowing electric furnace.

Ordinary electronic equipment is prostrated by the temperature of boiling water (212DEG F.). As the temperature rises, rubber and plastic insulation melts, chars or burns. Glass softens and loses its insulating power. Metals oxidize or melt. Even without such drastic damage, heat causes changes of properties that keep the apparatus from doing its job.

Titanium for Heat. G.E.'s heatproofers attacked their problem bit by bit. Since copper and aluminum fail at high temperatures, they turned to titanium and corrosion-resistant alloys. They learned how to coat wires with ceramic insulation. They made condensers out of fused aluminum oxide. In vacuum tubes they used titanium and ceramics instead of copper and glass.

In some ways the heatproof tubes work better than ordinary tubes. When operating red-hot, they need no electrically heated filament; their cathodes are hot enough to give off plenty of electrons. The hot titanium inside them acts as a "getter," sweeping up any stray gases that might impair the vacuum.

G.E.'s collection now includes a phonograph amplifier that works well and loudly in a furnace at 1,500DEG F., where an ordinary assembly of the same type turns into a puddle of molten glass and metal.

Radiation Resistance. While working on the heat-resistant components, G.E. scientists found that materials unaffected by heat can often stand atomic radiation, too. So they finally came up with a set of gadgets that ignores neutrons and gamma rays. Two of their assemblies, enclosed in a heated capsule at 842DEG F., spent 1,000 hours in the heart of the Oak Ridge nuclear reactor. They worked all the time, affected neither by the heat nor by the storm of radiation.

Heat-resistant electronics will be most useful at first in guided missiles, where heat is generated both internally and by air friction. In many cases, they will eliminate heavy and complicated cooling apparatus. When nuclear airplanes come into the picture, the new electronics will brave heat and radiation close to the power reactors. Only the crew will have to be cooled and shielded.

Another use will be in "Big Brother" reconnaissance satellites now in the planning stage. If they get electricity for working their television transmitters from small nuclear reactors, as has been proposed, they will need radiation-resistant tubes. Every gram of weight counts on a satellite. Big Brother will have no grams to spare for heavy shielding.

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