Weightless in Space

The junior space cadet may scream out in the night as he dreams man's ancient dream of falling through space, but he usually wakes up, at worst, on the floor, with nothing more than a slight bump. The real space traveler can count on no such happy ending. Space scientists believe that he will have to learn to live with a feeling of helpless falling while he flies through the stage of zero gravity. His nightmare will also include arms and legs that do not respond normally, and a sickening mental confusion about which way is up.

Physicists and biologists have recently been piecing together bits of experimental data and theory in an effort to figure just what the human body does when it reaches the point in space beyond the reach of earth's comfortable (1 G) gravity pull.

In the magazine Jet Propulsion, Major David G. Simons, chief of the Air Force Medical Corps Space Biology Branch, gives the most authoritative estimate to date. His conclusion: G-free man will doubtless experience a nerve-racking dis location that results in space-sickness, but can probably learn to cope with it.

Outside Loop. Airmen learned years ago that the pull of positive Gs can cause blackout because it drives the blood from the head down into the body (TIME, Jan.

10). But the G-free. or negative gravity problem, is quite different. It is bound up with the delicate nerve-sensory system -- centered in the canals of the inner ear, and in little muscular pressure points located through the body -- that tells man whether he is level, falling, upside down or accelerating. This delicate balance sense is closely connected with the nervous sys tem. If disturbed, it can produce effects ranging from nausea (as any victim of seasickness knows) to incapacitating shock.

It is impossible to create G-free conditions within the pull of earth's gravity, but military pilots have found a way to get a partial sub-gravity effect, says Major Simons. By flying in a shallow outside loop, they are lifted lightly out of their seats and can get the effect of fractional gravity for periods of 15 to 20 seconds.

One pilot of an F-84 Thunderjet reported a sense of "befuddlement" on his first five flights, and a "tendency to overshoot in reaching out rapidly with his arm." On the remaining 25 flights he learned to anticipate his troubles. But famed Air Force Test Pilot Charles Yeager,at much higher altitudes, reported "serious disorientation in his 13th second of weightlessness." Yeager, writes Major Simons, "got the impression that he was spinning around slowly in no particularly defined direction. After 15 seconds he became lost in space and pulled out [of his flight pattern]. With his returning weight his badly needed orientation was restored too." Mouse Trap. Reviewing one of the basic pieces of no-gravity research, Major Simons analyzes the 1952 test flight of two mice in the test of an Aerobee rocket.

Before the flight, biologists removed the inner ear sensory system of one of the mice, left the other normal, and put each in a "compartment in a rotating smooth-walled drum with an irregularity that afforded a possible foothold for each." Cameras recorded the brief critical no-gravity point of the rocket flight: the desensitized mouse clung to his perch, "whereas the normal animal clawed at the air, suggesting disorientation." A subsequent experiment with monkeys "clearly established the fact that the weightless state itself produces no disturbance of circulation in terms of heart rate or arterial and venous blood pressures," says Major Simons. "This does not mean that the circulation might not be involved secondarily due to emotional and autonomic reactions to weightlessness.

Such reactions are essentially the same whether caused by weightlessness, a rough sea or an obnoxious mother-in-law." Inside Problem. Generally, the experiments indicate that a human who can see or touch something to orient himself will be able to fight down the warnings from a sensory system gone haywire in weightlessness (much as a pilot learns to fly his airplane by what his instruments tell him even though this contradicts what his balance system tells him). Scientists are not yet clear what may happen without any touch or sight reference--for example, to a man inside a free-floating space ship, says Major Simons, "indications are that severe disorientation can occur." Nevertheless, he concludes, accumulating evidence indicates that man can learn to get used to the sense of floating or falling, and master his reactions sufficiently "to avoid an attack of incapacitating space-sickness."

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