. 0018933 velocity to subsonic by passage through a shock front which formed near the throat of the diffuser. Following this, they were subjected to a force field of such a nature that the smaller particles were impelled toward peripheral areas of the collecting filter toa greater extent than the larger particles. The diffuser was designed to effect a resolution of particles having average settling rates greater or less than 3 in. /sec. in the normal atmosphere (Reference 57). A light skin was wrapped around the outside of the diffuser to fair up the external shape of the nose cone. The propulsion section contained primary and sustainer motors, both of which were solid-fuel units about 6 inches in diameter with burning times of 6 seconds, The sustainer motor was ignited shortly before the start of sampling and provided sufficient thrust to maintain the rocket speed at about Mach 2 during passage through the cloud. Items of auxiliary equipment included explosive squibs, electronic timing circuitry, a parachute system, a closure system for the sampling section, a radio beacon anda dye marker, Foamed plastic inserts were fitted into the nose sections to provide additional buoyancy. The explosive squibs were used to remove the conical nose tip, thereby opening the sampling orifice, and to jettison the propulsion unit. The elec- tronic timing circuitry initiated the opening of the orifice, disconnection of