ABSTRACT Air-“pressure measurements on Operation Ivy were unique in two respects: Detonation of the first ‘“superbomb” on Mike shot presented an opportunity to verify experimentally the applicability of the ws scaling law at larger yields than ever before; and on King shot it was possible to observe simultaneously the development of the shock waveform over land and over water. Measurements on Mike shot were successful, with the exception that no overpressure data were obtained at pressure levels greater than 20 psi. It is recommended that efforts to repeat these measurements be made at the earliest opportunity. Measurements on King shot were quite successful in that it was found that the waveform over water was nearly ideal, whereas that over land obviously was subject to some deterioration as a result of the thermal effect and precursor formation. Analysis of the results made possible several significant conclusions, the most important of which were 1. The scaling law is apparently valid for radiochemical (RC) yields as great as 10 Mt. 2. Overpressures from Mike shot are evidently in agreement with the assumption that the overpressures to be expected from a yield, W, burst at the surface of a perfect reflector, are the same as would be observed from yield of 2W, burst in free air. 3. Agreementof the resuits from both Mike and King shots with those predicted from the height-of-burst chart published in TM 23-200 justifies extension of this chart to yields of the order of 500 Kt. The correction applied in this chart for thermal effects also appears valid. Appendix A to this report describes semiquantitative measurements of shock symmetry, and from all indications the shock wave was symmetrical along the two radii chosen for these measurements. $e Oye ' av om pop), yy L[AYG@Loa _ EE Fe —_" a (fa he “, I\, .