AIR SHOCK PRESSURE-TIME VS DISTANCE 1 INTRODUCTION Full-scale tests of atomic weapons at the AEC Pacific Proving Grounds on Eniwetok Atoll and the continental teat site at the Nevada Proving Grounds have yielded valuable information'~® on the pressure-time-distance pattern for shock waves from air and tower bursts of weapons of various yields. Overpressures measured at or near the ground on three test series, Operations Greenhouse, Buster-Jangle, and Tumbler-Snapper, have been used to con- struct a height-of-burst chart based entirely on experimental data. Data on experimentally measured overpressures from nuclear bursts, used in conjunction with those from analogous bursts of small-scale HE charges, corroborate the well-known w’ scaling law. Continued ef- forts in this direction are planned with the ultimate objective of gaining an understanding of blast-wave propagation that will take into account factors such as the effects of thermal radiation, mechanical disturbance of the surface soil, and variations in terrain. 2 OBJECTIVE AND SCOPE The two shots of Operation Ivy presented an unparalleled opportunity to measure blast pressures and study the propagation of shock waves under conditions such that thermal and mechanical effects were essentially minimized. Mike shot was the first experimental burst of a “superbomb.” Since it was only the second surface burst (the first was the Jangle Sugar shot) of a nuclear weapon, experimental data from this burst would have been expected to aid in fixing the zero intercepts of the experimental height-of-burst chart for nuclear weapons. The overpressures of interest occurred at comparatively great radial distances from ground zero, and the shock wave traveled a large percentage of its path over water to reach the majority of the measuring stations on the blast line, the locations of which were dictated by the geographical configuration of the island chain. Measurements on King shot were unique in that two blast lines were used, one entirely over water and the other predominantly over land. The only previous measurements of shock overpressures over water were those made on Bikini shot Able. The land line was intended to provide useful data for comparison not only with data from the blast line over water on King shot but with previously compiled blast data on shots at the Nevada Proving Grounds. It was hoped also that the results of these tests would provide Supplementary information on optimum heights of burst. Ordinarily, thermal effects from a surface burst over either land or water would be expected to be negligible because of the glancing angles of incidence. As a result of the size and thermal pulse duration of the fireball from 2 superbomb such as was used on Mike shot, how- ever, some thermal energy might be incident upon the surface in the area in which the precursor is usually observed, causing a slight thermal effect upon the shock wave. Thus it was believed that since the yield of Mike shot was considerably larger than that of ll