FLYING HIGH

Evening Post, Volume CXXI, Issue 20, 24 January 1936, Page 13

FLYING HIGH

OBSTACLES PRESENTED

The obstacles in the way of flying in the stratosphere were dealt with recently in London by Professor G T. R. Hill in the course of a paper befora the Royal Society of Arts, reports "The Times." He expressed the belief that they would be overcome during the lifetime of some of his audience, and that high-speed transport ir> the upper air would be possible.

Speaking of the greatest height which might be reached with the apparatus available at present to the aeroplane pilot, he drew attention to the flight by Captain Uwins in 1932 to a height of nearly 44,000 ft and of the flight by Commendatore Donati to an altitude of 47,360 ft. The latter was in a state of physical collapse on landing, and, even if his engine had been powerful enough to take him higher, it seemed clear that, with the system of oxygen supply to'the lungs at the local pressure obtaining at that altitude 'the hjiman limit had been reached.

If man wished to go higher he must go in a box which would protect him by preventing the oxygen pressure from falling unduly. This was what happened in balloons such as that used by Professor Piccard and those used in the United States and Hussia. The cabin need be only of the order of one-twentieth of an inch thick in duralumin to withstand the pressure so that no great excess of weight would occur. In the engine the main problem was that of supercharging. There would have to be a multi-stage supercharger, but this compressing of the air produced serious heating up if it was carried far. Even in the singlestage compressors used today the degrea of compression was only about two to one, but the corresponding temperatura rise was nearly lOOdeg C.

It would therefore be necessary to cool the compressed air. The question of cooling the engine in thin air would also have to be dealt with. Special fuel which would not freeze would probably have to be used. The lubricating oil would have to be carefully chosen because low pressure at high altitudes and high temperatures might combine to produce the conditions in a vacuum distillation plan* which might break down the oil.

He did' not look for an immediate transference of long-distance travel into the stratosphere, but rather to a gradual raising of the altitude. One barrier, which would impede future progress, arose out of the fact that the speed of sound in air was only about 700 miles an hour. Up to that speed a sort of bow wave of air pushed forward by the aeroplane gave a sort of warning to the air, which ultimately constituted the flow over the wings and body. If the aeroplane travelled at 700 miles an hour or more the bow wave could not travel ahead. Instead, a sort of shock wave was formed, the flow was altogether different so that energy was lost all along the shock wave and resistances rose rapidly. In relation to the speed at which the tips of airscrews moved through the air, this field of research had already been opened.