National Geographic : 1950 Oct
Seeing the Earth from 80 Miles Up tion come the heaviest bombardments of cos mic rays from outer space that strike the rocket during its flight. This is one clue to their origin, perhaps in the sun or the more distant stars. These rays are electrically charged particles constantly raining down upon the earth with tremendous energy. They are more powerful even than the rays generated in the atomic bomb and flash through the human body from 10 to 20 times a second, though without any known effect. Geiger counters in the rockets register the numbers of rays coming in from various direc tions at each second of the flight. For ex ample, they may show more rays entering through the nose than through the sides at one second past eight; but unless we know which way the nose was pointing at that moment, we cannot tell from what direction this heavy bombardment was coming. After climbing to about 25 miles, the V-2 begins to wobble, spin, and tumble, so that its nose keeps pointing in different directions. But by measuring angles in the pictures taken on the flight, each of which is timed, it is possible to tell how the rocket was oriented at any given instant. If the picture taken at one second past eight shows that the rocket was moving tail downward, we know the nose was pointing upward. If more cosmic rays were coming into the nose than from other directions at that moment, then we know this heavy bombardment was arriving from di rectly overhead. Rockets at White Sands are launched almost vertically upward, to insure that they will reach the greatest possible altitude. An auto matic pilot is set before firing to keep them on course, but they cannot be controlled after they get into the air. Fuel can be cut off by radio, however, if it appears the rocket is veering so that it may fall in inhabited country. V-2 Record Height Is 116 Miles Highest altitude reached so far by a V-2 is 116 miles. One Wac Corporal rocket, de veloped in this country, attained a height of 250 miles with the aid of a V-2. It was carried up to about 20 miles on the V-2, then fired from there, and the extra push of the larger rocket added to the Wac Corporal's own power carried it to this record altitude. No cameras were sent up on this flight, since all available weight was devoted to fuel and instruments and there would have been small chance of recovering anything after a fall from so great a height. Some of our high-altitude photographs of the earth were made from the Aerobee rocket.* Less complicated and cheaper to build than the V-2, it has reached heights of 78 miles and will be used to carry on upper-air research after the supply of V-2's has been exhausted. Both the V-2 and Aerobee have gained in formation about the high upper atmosphere that was impossible to obtain in any other way. The flights have measured the original cosmic-ray particles that come in from outer space before they plunge down into the earth's atmosphere. Except for a few balloon flights, it was possible previously to study only the less-powerful secondary rays created when the original rays strike and disrupt atoms of air. Ultraviolet rays from the sun have been measured which never penetrate to the earth's surface, since they are absorbed by a layer of ozone that blankets the globe between 20 and 30 miles up. Vacuum at 80 Miles Up At about 80 miles high, the rockets reveal, the atmospheric pressure is as little as one ten millionth of that at the earth's surface, which means that the air at that height is so rarefied that it is actually a high vacuum. Striking changes in heat and cold were measured as the rockets climbed. Over White Sands the temperature drops steadily to about -63° F. from the surface up to 10 miles, and fluctuates slightly for another 10 miles. From 20 to 30 miles the temperature is about 65° F.; it falls once more to -150° F. at about 50 miles, and at 75 miles climbs again to 212° F., the sea-level boiling point of water. All this information is sent back to the ground by automatic telemetering systems. Temperature, for example, is measured by a thermocouple, made of two different metals welded together. The two metals react to temperature changes and, in so doing, gener ate a small electric current the strength of which is proportional to the temperature. This varying current is converted into a radio signal which varies in strength in the same way, recording on the ground the changes in heat and cold aloft. Corn seeds and fruit flies have been sent up more than 85 miles on some rockets in an effort to discover whether the powerful bombardment of cosmic rays at such altitudes would cause mutations or hereditary changes in future generations of the plants and * The Aerobee was developed for the Navy by the Douglas Aircraft Company and the Aerojet Engineer ing Corporation, under the technical supervision of the Applied Physics Laboratory.