It is essential to know the amount of air available for sampling in the region from 100, 000 to 200, 000 feet. The density of air decreases exponentially with altitude as shown below: Altitude Density (ft) (b/cu ft) 0 (at sea level) 0.0765 50, 000 0. 0116 100, 000 0, 0010 150, 000 0.0001 200, 000 0, 00002 The weight of air existing in a column of one square foot area limited by various altitudes can also be calculated as follows: Altitude (H) Weight of Air (M/A) (ft) (1b/sq ft) 200, 000 - 150, 000 2.8 150, 000 - 100, 000 20.6 100,000 - 73,300 55.9 150,000 - 73,300 100,000 - 68,500 76.5 76.5 60,000 - 51,4060 76.5 This shows that a perfect ducted sampler with a one~-square-foot throat would only sample 2.8 pounds of air while falling from 200, 000 to 150,000 feet. The total amount of air sampled from infinity to 200, 000 feet would only be 0.47 pounds.+ Feasibility Study To select the most promising sampling method the study was divided into two parts -- air sampling methods and particle collecting methods. cu ft are actually processed by the device. Air sampling is concerned with the technique of insuring that 1000 std The particle-collecting technique must insure that at least 50 per cent of the particies in the air sample are collected, Air-Sampling Methods Two air-sampling methods were thoroughly analyzed -- a parachute sampler and a rotorchute sampler. Parachute Sampler. A rocket has two major disadvantages as a vehicle for atmosphere sampling: pling time, and small payload. short sam- To overcome these disadvantages, a parachute system was considered in which the parachute would act as a scoop to collect the air and also to increase sampling time by limiting the rate of descent, A duct and sampling device would be located at the vent hole in the center of the parachute. Increased stability could be obtained by placing a second parachute above the first, with the first functioning merely as a scoop or air-collector. 102