492 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1940 



absorbing process is both intricate and costly. If some improved 

 reinforced plastic could be used instead, the path of the manufacturer, 

 once he had learned the art, would be much simplified. 



Speeds have grown because of the smoother shapes used in con- 

 struction and through the greater engine powers provided. Can 

 speeds continue to rise indefinitely? We may have gone almost as 

 far as we can in using ship-shaped forms, though we still know very 

 little about the possibility of insuring an increase in the extent of the 

 laminar flow of the air over the surface of wings or body. If this 

 could be done the resistance would drop considerably. As far as 

 prospective increases in engine power are concerned there is little 

 publicly revealed in these days, but one hears of testing plants being 

 adapted to deal with engines of no less than 3,000 horsepower apiece. 

 But even with these increases a definite speed limit is being ap- 

 proached — not one imposed by the laws of any State but by the laws 

 of Nature. As I pointed out 2 years ago in a presidential address 

 to the Royal Aeronautical Society, there is good reason to believe that 

 although speeds of 500 miles per hour may be attained, it is unlikely 

 that 600 will be much if at all exceeded, for the latter figure is some 

 SO percent of the speed of sound, and when the latter is approached 

 the drag rises to a level far ahead of any prospective engine im- 

 provements. Although nothing in the physiology of man forbids 

 even higher speeds, as witness the high orbital speed of the earth on 

 which we all live with some measure of tempered comfort, there is 

 soon imposed a physiological limit if high speed is combined with 

 rapid maneuver. If the latter is required, then the speed must be 

 controlled to suit the conditions. Only the future can reveal how the 

 balance between the two will be struck. 



No simple summary can be given of what has been done as regards 

 engine development, for great as has been the change from the 15 

 pounds per horsepower of the original Wright engine to the 1 pound, 

 and less, of today, one remembers that in this one respect the engines 

 of the last Sclineider Trophy Race were as meritorious; where the 

 latter were much below modern standards was in their lack of relia- 

 bility when working at this power ratio. Today's engines run with- 

 out attention for hundreds of hours, a very different matter from 

 endurance for a short race. 



Even if engines of 3,000 horsepower may be said to be in sight, they 

 are still some way from achievement. Progress depends not only on 

 the skill of the engine designer and the metallurgist, but on the 

 ingenuity of the industrial chemist in producing his remarkable fuels, 

 wonderful alike for their uniformity of quality and for their ability 

 to resist detonation even when employed in engines of very high 

 compression ratio. 



