Karl Saivieki, age 13, of Rochester, New York, for his question:
In what sort of chambers do astronauts practice weightlessness?
The earth provides us with its own very definite set of conditionswe have learned to cope with its systems of ups and downs and directions. But every young spaceager knows that the earth's special conditions do not, necessarily, prevail in regions outside our planet's control.
An orbiting astronaut is freed from the everyday force of gravity that hugs us to the ground. And a new word was needed to name this strange condition. We feel one factor of gravity as a sense of weight, so the orbiting astronaut was said to be weightless. But weightlessness is not a good word because it does not mean what it seems to mean. However we must use it because nobody has gives us a better word to replace it.
Space agers know that weightlessness begins when acceleration stops and the spacecraft establishes its orbital trajectory. As astronaut and everything else inside the coasting' craft are weightless until retro rockets trigger the slowing down process of deceleration. The reasons for this belong in the answer to another question. Today's question deals with how we prepare a person to cope with the unfamiliar conditions of weightlessness.
On earth, we experience brief states of weightlessness when we swing on a swing or descend on a fast elevator. They last but a split second. A parachutist is weightless while in free fall, until his chute opens. No special training is needed to cope with these brief gravity free spells. But an orbiting astronaut may be weightless for days. He must learn to move and perform everyday duties without the everyday help of surface gravity.
We have seen pictures of astronauts coping with weightlessness, perhaps walking on walls or ceilings. Actually, these odd antics are not performed in a special chamber on earth. We have no such practice chamber where spacemen can learn to cope with weightless conditions in orbit. We do have a machine called an air bearing that rides or glides upon a column of air. This air bearing machine reduces the frictional forces between the surfaces of objects. These forces are caused by the earth's normal gravity. The air bearing serves a useful purpose in training an astronaut for a weightless walk in space with a cable attached to his orbiting spacecraft.
Our weightlessness simulation chambers actually are fast flying planes performing a special swooping maneuver called a Keplerian Trajectory. If this clever maneuver is correct, the pilot may have as long as 40 seconds to practice moving in a weightless condition. The TV movies of astronauts tumbling and walking upside down in a weightless condition were taken aboard a C131 Transport flying the Keplerian Trajectory. At present, we have no chambers for longer practice periods.
With a special swooping maneuver, a fast plane can produce more than half a minute of weightlessness. The pilot has time to aim and shoot a dart or to mark a certain spot on a printed pattern. Without the normal guidance and assistance of gravity, these simple eye hand operations are incredibly difficult to perform. At first, the future astronaut makes a mess of things. But his coordination in the weightless condition improves with the short practice periods inside a fast, swooping plane.