This mechanism had first been tested with a chimpanzee run on 9 April, when only one door opened, but it had undergone additional tests since then, and on the 20 August run it functioned as scheduled. Colonel Stapp was exposed to an estimated maximum of 5.4 pounds per square inch of wind pressure, with maximum velocity of 736 feet per second and peak deceleration of only 12 g's. He suffered no apparent ill effects save temporary and quite minor injury from flapping clothes and windblown grains of sand. It was, he said, the "easiest" of all the runs he had made so far. 14

During September 1954, the principal sled experiment was one that made use of a tumbling seat attached to the rocket sled in order to evaluate the effect of tumbling in combination with deceleration and windblast. The tumbling seat had been tried out before in static tests, and in one preliminary test on a moving sled, but the first full-scale experiment was held on 14 September. A chimpanzee was spun at the rate of 105 revolutions per minute at the same time as it was being exposed to sudden windblast (through the same opening windshield used on Colonel Stapp's previous run) and to braking deceleration that reached a peak of forty-five g's; yet the subject came through very nicely. 15 This type of experimentation supplemented research done elsewhere on the effects of pure tumbling, for instance on a spinning turntable, but with its fixed axis of rotation the tumbling seat did not wholly simulate free-fall tumbling as encountered during escape from aircraft. Moreover, known instances of tumbling in the thin air at high altitudes all suggest that rapid tumbling must be eliminated if at all possible. And it largely can be, by means of stabilizing devices. For all these reasons the Aeromedical Field Laboratory has not continued its tumbling seat experiments, but instead continued work on deceleration and windblast both separately and in combination with each other. 16