438 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1954 



be unconscious when he reached that level. In view of this circum- 

 stance it has been deemed safer to bail out for a free fall with a para- 

 chute that will automatically open at 10,000 to 12,000 feet. With 

 rockets and the much-talked-of space ship, which will fly through 

 ether in which there is no pressure and no oxygen, the paramount 

 importance of maintaining adequate pressure levels is obvious, and the 

 energy required to maintain pressure, let alone jet propulsion, is so 

 great that even the most optimistic are loath to predict that the prob- 

 lem of fuel supply could be solved, despite all the resources of human 

 ingenuity, within the life span of this generation. Perhaps one might 

 reach the moon, but how would energy be secured to insure return? 

 More difficult conundrums have been solved in the past, but, although 

 I happen to be an optimist with faith in the resourcefulness of some 

 future generation, I believe that the only possible solution lies in atomic 

 energy with all its weighty paraphernalia.^^ 



Acceleration in high-speed aircraft. — The successful use of oxygen 

 presupposes a steady blood circulation without undue gravitational 

 pressure on the heart; however, it became obvious to the French flight 

 surgeons in 1918 that rapid turns and dive pull-outs tended to diminish 

 the flow of flood to the brain. In the Snyder Trophy Races in 1929, 

 confusion and dimming of vision were encountered when the pilots 

 were rounding the pylon ; and in 1932 a man of great insight, Heinrich 

 von Diringshofen of the German Air Ministry Research Laboratories 

 at Tempelhof in Berlin, constructed a human centrifuge to simulate 

 problems of acceleration in flight. Before this, however, two equally 

 thoughtful Dutch investigators, Jongbloed and Noyons of Utrecht, 

 had studied the efi'ects of acceleration on the level of the systolic blood 

 pressure in animals. As a plane's speed is augmented or diminished, 

 the pilot is pushed backward or forward in his seat by a force directly 

 proportional to the rate of acceleration or deceleration. If the increase 

 of speed occurs at 32.2 feet per second, the pilot would be pushed 

 against the back of his seat by a force equal to that of gravity, but, 

 when pilots pull out of dive-bomb maneuvers, the direction of the 

 acceleration is from head to foot, and, as far as the circulation is 

 concerned, there is a tendency to pull blood from the head. 



Need for protection from high acceleration in aircraft has become 

 even more acute in the last few years owing to the development of the 



" And so it turns out that in man's quest for mastery of the air a great step 

 forward has been talsen in the successful development of pressurized cabins. 

 These developments, however, are in their early infancy from the engineering 

 standpoint, and their use in larger transport planes, in rockets and jet-propelled 

 craft, will succeed only if the limitations of the human frame, both in its structure 

 and in its functions, are kept constantly in mind. And let us not forget that it 

 was a flight surgeon and not an engineer who wrote the specifications for the 

 first pressurized plane. [ See Fulton, footnote 13.] 



