LAST YEAR'S FAILURE

Evening Post, Volume CXX, Issue 12, 13 July 1935, Page 9

LAST YEAR'S FAILURE

BALLOON WRECKED AT GREAT HEIGHT

The last attempt of the United States Army and National Geographic Society to organise an ascent into the stratosphere also ended in misfortune. On July 28 of last year Major W. E. Kepner and Captains A. W. Stevens j and O. A. Anderson rose 60,000 feet; above the earth in a spherical metal gondola suspended under the largest balloon ever made up to that time and then had the harrowing experience of seeing the balloon tear itself apart and threaten to dash them to death on the earth twelve miles below. They had mounted over Rapid City, South Dakota, and there was nothing they could do but hope that the balloon would hold together until they could reach a level in which they might seek safety with their parachutes. It would have been suicide for them to leave their oxygen-filled chamber before then, for even if the thin atmosphere would have sustained them it is unlikely that they would have survived the fall from that great height. Ultimately what they feared did happen. ,The balloon came to pieces and the metal' gondola fell to the ground. But before that, when it was four miles above the ground, the three men had crawled out upon the top of the gondola and coolly waited their chance to jump. At 3000 feet Captain Anderson jumped, Captain Stevens had a little trouble with his parachute and was delayed for a moment or two during which time the balloon fell 1000 feet. Major Kepner followed, and by this time the gondola was only about 500 feet above the earth. The gondola, with the remnants of the balloon, dropped in a field near Loomis, Nebraska. It was much damaged but most of the scientific instruments within it had escaped harm. During the ascent the army balloonists conversed by wireless with General Westover, their chief, in Washington, and their conversation was broadcast to the public. GAS EXPANDS WITH HEIGHT. As the balloon rises, it passes through thinner and thinner air, and the gas within it expands correspondingly, so that at some height, depending upon the amount of gas originally used and the size of the envelope, gas will begin to escape. In designing a balloon which is intended to rise to a great height, a calculation is made to arrive at the amount of expansion due to the desired limit of height, and the envelope is made of such a size that it will be exactly filled at that Height. This means, of course, that at ground level the envelope will be only partially filled, • and the stratosphere balloons, which are designed to be practically spherical at their maximum height, are so slightly filled to begin with that in shape they roughly resemble a nicely tapered parsnip with a hemispherical top. One thing that follows from this design is that the rate of ascent is practically constant until the limit of height is reached, whereas a full balloon will start oft' with a great rush and rise less and less rapidly as it ascends. CAUSE OF ACCIDENT. It will be apparent that the fabric, being big enough to expand into a sphere, will be quite elaborately folded in its partially filled state, and it was this which caused the .1934 disaster. Folds of fabric clung together, possibly as the result of being electrified by the friction of one part on another, as they were called upon to spread, and they began to tear. The damage spread rapidly, gas escaped, and the balloon began to fall. The lower portions of the bag were carried up until the whole affair became a gigantic parachute full of hydrogen and air, which soon formed an explosive mixture. Then some unexplained cause —probably again electrical—led to a Intense interest was aroused by the "explosion" owing lo the fact that while hydrogen and air form a mixture which practically detonates, the noise of the explosion was not heard, or at all events was not recognised, although at the time at least one aeroplane was flying close to the balloon. The explanation is, however, quite simple. An explosion of gas is always propagated at a certain rate; that is, the whole of the gas does not "go off" at once; and the balloon was so large— well over 100 feet in diameter—that it took a considerable fraction of a second for the explosion wave to traverse the whole body. There was thus no "bang," and if anything could have been heard it would have been only a low roar. HELIUM INSTEAD OF HYDROGEN. The explosion danger was shown by this accident to be, a very real one in the use of such balloons, and the new one was designed with a special view to side-stepping it. In the first place the fabric used was made a good deal stronger, so as to minimise the risk of tearing. In the second, the balloon was filled not with hydrogen but with helium, which is absolutely non-inflammable. Helium is not so light as hydrogen, and consequently gives less lift, and that is why the new balloon was inuric larger— 3,750,000 cubic feet as against 3,000,000. ! The actual lifting power of the new | balloon was calculated to be equal to j that of its predecessor. i THE OBSERVER'S CAR. j The spherical "gondola" in which the observers do their work is a very carefully constructed affair, airtight so that a normal atmosphere can, thanks to | chemical conditioning, be maintained, for no man can live in the rarefied air many miles above the earth. If the ascent had succeeded it would have j been the ninth device of its kind to : be taken aloft, and also the largest, i measuring nine feet in diameter. The previous American attempt was made with a sphere eight feet in diameter. Better materials enabled the new one to be made bigger without increasing the weight. The interior of the sphere was loaded with instruments for making a variety of observations, and the affair was equipped also with some independent.

observers in the shape of small tubes attached to parachutes, which could be released. The idea was to let these go, and as they fell, air would pass through the tubes, inside which small filters were fitted. Each tube had also automatically operated flaps to close the ends at certain levels. The filters would thus trap samples of any spores or other material that happened to bu floating in the air.

Elaborate; radio equipment was included in lliq apparatus.