Science: Trial by G

The modern military airplane carries a frightening passenger. The name is G.* During steady, level flights, G keeps still as a mouse, but when the plane makes a turn or pulls out of a dive, G takes charge. Every part of the pilot’s body grows unnaturally heavy. His cheeks sag; his jaw drops open; the blood rushes out of his brain; his guts crowd into his belly. Too many Gs can black a man out, cripple him or even kill him. Air battles of the future, fought above the speed of sound, will be won by pilots equipped to outwit G.

Swooping Gondola. Last week the Naval Air Development Center at Johnsville, Pa. unveiled a monstrous apparatus for studying the effect of G-forces on fragile human flesh. In a trim, museumlike building, a soft, cantilever arm whirls in a horizontal circle, carrying on its end a lens-shaped aluminum “gondola” where the helpless “airman” sits. The gondola can be tilted at any angle, directing the G-force in any direction through the passenger’s body. Driven by a 4,000-h.p. motor, the arm can generate 15 Gs (much more than a man can stand) in less than two seconds. At full speed, the gondola moves at 174 m.p.h. Generating 40 Gs, it whooshes like a captive hurricane.

Round & round with the passenger rides a crew of sharp-eyed instruments. They feel his pulse, measure his breathing, record through electrical contacts the action of his overloaded heart and his bloodstarved brain. A television camera stares him in the face, reproducing his sagging grimaces. Sometimes an X ray strikes through his body, watching the motion of bones and internal organs in the grip of G.

Some passengers who ride with G are naval airmen, but the G-doctors often submit themselves to experiment. The doctors insist that riding with G is not very dangerous; the instruments watch the victim’s condition, and the arm can be stopped quickly if he gets in bad shape.

Frozen in Death. Human subjects, of course, are not exposed to the deadliest struggle with G. Rats are the commonest victims for these experiments. They are spun in a smaller centrifuge until everything movable inside their bodies has gone well away from normal position. The rat is then dead, but unfortunately for researchers, his organs do not stay in their distorted position when the G-force is relaxed. The organs creep back toward their proper places, depriving the G-doctors of valuable information.

But the doctors have learned to spin the rats on a special centrifuge. When G is high enough (19 Gs or so), the distorted rat is doused with liquid nitrogen, which quickly freezes him. Then the doctors can open him up and find where his organs were when G was pulling at them.

Glowing Brains. Physically, rats are not much like humans. Monkeys are better. Sitting strapped to miniature pilots’ seats they look like small, worried old men. Sometimes when they ride with G, they have round windows cut in their skulls and covered with transparent plastic. A strong ultraviolet light is played on their brains and a fluorescent chemical is injected into their bloodstreams. Then during the ride the doctors can tell when the treated blood has reached the brains: the blood vessels glow brilliantly.

For animals near human size, the G-doctors first tried goats, but goats cannot stand as many Gs as humans. Now chimpanzees are being considered. A chimp is built much like a human, and it weighs little less than a small fighter pilot.

Out of all this unpleasantness, for both animals and humans, the G-doctors are sure that much valuable information will come. It is much better, they say, to learn about G in a captive gondola than in a runaway jet screaming through the sky.

* From “gravity.” One G is the normal force of gravity. “G-forces” are the similar forces caused by acceleration or by rapid turns at high speed.