620 Miles Per Hour

New Zealand Listener, Volume 4, Issue 98, 9 May 1941, Page 5

620 Miles Per Hour

\ E are rapidly approaching a definite limit over which it will not be possible to go with the accepted type of aeroplane. An appreciation of the reason for this can be approached in the following way: Consider a machine something like a modern fighter, weighing about 2% tons. In the light of established aerodynamic data, 1,000 horsepower will give such a machine a speed of 350 miles an hour, By doubling the engine power the speed will rise to 440 miles per hour. Trebling the power brings the figure to 500 miles per hour. Increasing the power output ten times to 10,000 horsepower results in a speed of about 620 miles per hour. In the foregoing, the engines have all been assumed ‘to have tle same weight as the 1,000 horsepower one. With the best of the existing materials and all the available knowledge with regard to engines, it would seem most improbable that we can’ hope for engine weights much lower than about one-half of a pound weight for each horsepower developed. Hence a 10,000 horsepower engine is not likely to weigh much less than 21 tons, or the weight of the aeroplane we have been considering. So we have entered a vitious circle when the speed reaches about 620 miles per hour. Approaching another way, we again arrive at much the same result. The speed of sound in the sub-stratosphere, i.e., from 20,000 to 35,000 feet, is about 620 miles per hour, Known aerodynamic data shows that up to about 550 miles per hour the aeroplane virtually cleaves the air and experiences relatively little resistance, but as we approach the speed of sound an entirely different phenomenon begins to take place. Here the aeroplane has to be pushed against the air, which is unable to get out of the way except by brute force. Unless the developments in the control of atomic energy become practical, it can be said that we are rot likely to see aeroplane speeds in excess of 620 miles per hour, although we shall approach this figure fairly soon.-(Winter Course Talk, "The Future of the Aeroplane," by Professor T. D. J. Leech, 1YA, April 17.) ’