Atom-Driven Planes

One of science's most exciting--and most secret--projects is adapting atomic energy to aircraft. Since atomic fuel (plutonium or uranium 235) would have over two million times as much energy as gasoline, a "nuclear-powered" plane could fly on & on, round & round the earth. It could fly at its top speed all the time, and land with the same weight (and about the same amount of reserve fuel) that it took off with.

Dr. Andrew Kalitinsky of Fairchild Engine & Airplane Corp. (which is working under the Atomic Energy Commission) recently explained the problem at a Manhattan meeting of the Society of Automotive Engineers. In outline, the job looks simple. A "nuclear reactor" (essentially a controlled, slow-exploding atom bomb) gives off most of its energy as heat. One way to do the trick is to put a reactor in place of the combustion chambers of a turbojet engine (see chart). A compressor forces air into the forward end of the engine. Heated and expanded by the nuclear reactor, the air shoots toward the rear end. On the way it spins a turbine, which runs the compressor through a shaft. The force of the jet escaping from the tailpipe pushes the airplane forward.

Hot Engine. All this is not as simple as it sounds. A small, controlled reactor has been built (TIME, Sept. 8), but putting one into a jet engine involves tremendous difficulties. The reactor must run very hot, but not burn itself out. It must transfer enormous amounts of heat to the "working fluid" (air) without slowing the blast too much.

Probably the toughest problem of all is how to keep from killing the crew by radiation. As Dr. Kalitinsky puts it: "The radiation intensities encountered in nuclear reactors must be reduced by factors of many billion before they are safe for the human organism."

Light Shield. Airplanes cannot carry massive concrete shields like those around the piles at Oak Ridge and Hanford. A lighter shield is needed. The most deadly radiations are neutrons and gamma rays.

Neutrons can be reflected by layers of materials (such as graphite) that bounce them back without absorbing them. A good reflector turns back as much as 90% of the neutrons hitting it.

Gamma rays have to be absorbed by dense materials like lead. "A material which is good for stopping gamma rays," says Dr. Kalitinsky, "may not be the best when gamma rays and neutrons are considered together, and a material which is good for the innermost part of the shield may not be the best for the outer layers. There is, therefore, considerable room for weight reduction by ingenious design."

Dr. Kalitinsky sounded hopeful, as if he had items of progress which he wished he could crow about. But he warned his listeners not to "expect to see an atomic-powered rocket taking off for the moon this year or next."

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