(D) Theory and Proposed Experiments for Study of Diffusive Collection D. Q, Matejka, J. R. Banister, D. J. Rigali Sandia Laboratory Introduction (D. Q. Matejka) Previous studies have shown that debris from upper-atmosphere nuclear explosions should primarily be confined below 600,000 feet altitude. Rather extensive programs in effect for several years have been obtain- ing samples up to about 100, 000 feet. The sampling program under discussion at this symposium would com- plement the current programs in determining the presence and time distribution of nuclear debris in the upper atmosphere. In order to obtain a sample as efficiently as possible, the descent of the sampling device should be controlled, A parachute with a low weight-to-drag-area ratio is one of the more efficient drogue devices, Parachute technology achieved through a large number of drop tests and rocket instrumentation recovery programs at Sandia shows that a parachute should serve as an efficient, yet economical, retardation device from about 200, 000 down to 100, 000 feet altitude. doubtedly have to be used to obtain samples. Above 200, 000 feet, some unique, new method will un- Based on these facts, it was decided first to develop a sampling device to collect samples in this lower regime. With the benefit of this experience, the design of a new highregime sampler would then be attempted. Experimental information is not available on the concentration of this debris in the upper atmosphere above 100,000 feet. Also, it is not known what minimum quantity of air must be sampled to obtain sufficient debris to enable an accurate analysis to be made. sampled on the first shots. Necessarily, therefore, a large volume of air must be Subsequent to this determination, the size of the sampler and possibly even its rotational speed can be decreased, If radiochemical analysis or one of the alternate methods are further re- solved to the point that less particulate matter is required for analysis, then further reductions in sampler size or volume of air sampled can be made. With the preceding requirements and limitations in mind, it should be possible to collect sufficient debris for radiochemical analysis in the following manner: To ensure a large swept volume of air, two 8-foot collector blades rotating at 10 rps appear reasonable. These rotating blades, driven by small, solid-propellant thrust units at each tip should sample particulate matter from 10,000 standard cubic feet of air during about 5 minutes of fall, while traversing the 200,000 to 100, 000-foot region, according to theoretical trajectories. be created and air flow will not be excluded from filters. The blades will be set at zero a, so no lift will These trajectories show that a large, light-weight parachute deployed at apogee, after a near-vertical rocket launch, should provide near ideal conditions for the deployment and initiation of rotation of the sampler mechanism, Figure 1 shows pictorially the sequence 13£