Atoms Aloft

Last week the atom-powered dream plane was one step closer to reality; the Air Force announced that it had contracted with Consolidated Vultee for an airframe to carry a nuclear-reaction engine. The engine itself is already under development by General Electric Co.

Only rough guessing is possible about this buttoned-up subject, and no guess is likely to hit on an accurate description of the atomic plane. Nuclear reactors have been evolving rapidly. Several widely differing types have been described, and more are under secret development. Some, using plutonium or uranium 235 instead of natural uranium, may turn out to be small but still very powerful.

Nuclear Jet. Controlling and applying the reactor's awesome power is more difficult than releasing it. A reactor is basically a source of heat, and can be run at any temperature that its structural materials can stand. The most obvious way to turn this heat into propulsive energy is to pierce the reactor with tubes and blow air through them by means of a compressor. The air keeps the reactor from overheating. In doing this service, it gets hot itself. It expands enormously and roars out of the other end of the reactor, spinning a turbine that turns the compressor. This is little more than an ordinary turbojet engine with its combustion chambers replaced by a nuclear reactor. After passing through the turbine, the blast of hot air rushes out the tailpipe, while the reaction to the blast drives the airplane forward.

Some informed guessers think that the reactor could not transfer enough heat to streams of air blowing through it. One way around this would be to use a molten metal in the reactor instead of air. This "working fluid" would carry energy to one or more jet engines, heating their air blast by a sort of high temperature radiator. The molten metal would not be as fiercely radioactive as the reactor itself, so it should be easier to handle.

Fuel Unlimited. Any competent power engineer can think up other variations. Probably the final design, weight, bulk and power of the nuclear engine will be determined by such factors as the temperature that its metals can endure or the heat that can flow through them. One factor that the designers will not have to worry about is fuel economy. The fuel (uranium or plutonium) that starts the engine running will last almost undiminished throughout any flight that the airplane is likely to make.

The engine is only one problem of the atomic airplane. Another is protecting the crew from the blast of radiation given off by the reactors. This may not be as difficult as it seems. Better shielding materials than the conventional lead and concrete, have reportedly been discovered, and the nuclear engineers may have learned how to reduce the quantity and penetrating power of the radiation.

Shields for Humans. In any case, an airborne reactor will probably not have to be shielded on all sides. Only the crew's compartment and perhaps certain instruments need to be protected. This might be done partly by mere distance, e.g., by placing the reactors in the tail or far out on the wings. Another obvious trick would be to make the airplane's structural parts or equipment (e.g., the retracted wheels) serve as partial shields. Final protection would be a bulkhead of shielding, to provide a safe "radiation shadow" for the crew's space.

Such a plane, shooting most of its deadly radiation unhindered into the air, will be dangerous on an airfield. When its reactor is running, all men in the vicinity will have to take cover, and the radioactive blasts roaring out of its tailpipes may poison the area permanently. To reduce these hazards, the atom-plane may have to take off with rockets, starting its nuclear engines only when safely up and away. In spite of such precautions it will not be a pleasant airport-mate. Once its reactors have run for a while, they will be radioactive even when shut down. If atom-planes ever become common, the fields from which they fly will be thickly sown with radiation alarms and patrolled by safety personnel armed with radiation detectors.

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