tained on all six shots. PROGRAM i: BLAST AND SHOCK MEASUREMENTS fectly reflecting surface, as had sometimes been assumed. Shot 3 was detonated in the rain and show- Project l.la, 1.1b, and 1.1d “Blast Pressures and Shock Phenomena Measurements by Photography” ed the effects there in low pressures and rounded (WT-902), Naval Ordnance Laboratory; C. J. Aronson, Project Officer. The objectives of these projects were to (1) deter- wave forms. It was concluded that peak oressures generally correspond to about 1.6W instead of 2W free air when the hydrodynamic firebali yields, using 2W theory, are the reference yicids. mine the peak shock overpressures in air as a function of distance from ground zero, (2) to obtain informe- Project 1.2b “Ground Surface Air Pressure versus Distance from High Yield Devonations (WT-905), Ballistic Research Laboratories; J. J. Meszaros, tion on the furmation, growth, and magnitude of precursors and other visibly observable thermal effects which may occur, and (3) to measure the motion of the shock wave on the waters surf<ce to obtain the - pressure-distance relation. The smoke~rocket photography and direct-shock photcgraphy results were in general satistactory. Project Officer. The principal mission was to obtain pressure-time data in the region greater than 40 psi. A secondary objective wag to field-test a newly developed seilf- Some data were lost due to photographic difficulties and the presence of cloud cover at the time of deto- reccrding pitot gage. Pressure-time measurements were made on ali six shots. Two blast lines were activated for Shot 3, and pressure measurements were obtained on beth lines. Extensive dynamic- nation for several shots. The project participated on all shots, but no film was usable from Shot 3 because of the low yield of the device. Pressure-~distance data vertically above the shot were obtained cnly on Shot 2. The uncertainty of the measured data was pressure mé@asurements were made on Shot 6. Air-pressure measurements using the solf- contained flast-initlated gages were successful Overpressure data were obtained up to pressure such that it was not sossible to cefine the effect of a nonhomogeneous atmosphcre on blast. Non-ideal wave forms op- tained indicated that water does not constitute a per- Measured sur-~ levels of 250 psf. Dynamic-pressure measurements3 using newly developed self-recording q-gages were face data of both pressure and arrival time appear self-consistent, as well as comparing favorably with very successful. Measurements were oltaincd wver a dynamic pressure range of 0.43 to 138 psi. Shot 3 Jangle and Ivy data. It seems justified to conclude that cube-root scaling of blast data from events of this yield range is valid. No precursors as such were produced anomalous results: two blast lines oriented approximately 180 degrees apart obtained two distinct noted; however, anomalous wave furms were recorded pressure-distance relations. by the pressure-time gages. following immediately behind the shot on Shots 4 and during detonation, were as much as 20-percent lower 5 may explain the anomaly. The aerial photography was unsuccessful. The extreme range of the aircraft than the pressures at comparable distances on Uncie Island. The validity of the cube-root scaling law to scale and the obscuration of the field of view by clouds prevented the project from obtaining any readable film. distances for yields as great as 15.0 Mt appears to have been substantiated. Project l.lc “Base Surge Measurements by Photo~ would be obtained from a burst of 1.6 times the yneld in free air. C. J. Aronsor, Project Officer. The objective was to gather photographic data obtained during the operation which could be of value in the formulation of scaling laws to predict the basesurge effects from surface detonations. The experiment was almost entirely unsuccessful, since photography was rendered useless when it was decided to schedule detonation of the skots before sunrise. A minimum effort was maintained throughout the series, which indicated a possible base surge for~ mation on Shots 1 and 2; however, a detailed study could not be accomplished. face Bursts” (WT-904), Sandia Corporation; C. D. Broyles, Project Officer. This project was directed toward obtaining measurements on blast pressure versus time at ground level with Wiancko gages. Measurements were ob- It was concluded that over- pressures from a surface burst are the same as graphy” (WT-903), Naval Ordnance Laboratory; Project 1.2a “Ground Level Pressures from Sur- The pressures obtained on the Tare line. cver which raj or fog was evident <A dense water cloud Project 1.3 “Dynamic Pressure Measurements” (WT~306), Sandia Corporation; C. D. Broyles, Project Officer. The objectives were to spot check the theoretical relationship between dynamic pressure and overpressure in the 10-to-40 pal overpressure range, and to evaluate a group of gages measuring various blast parameters. The single measurement of dynamic pressure obtained on Shot 6 in an overpressure region of 21.5 psi agreed with that normally associated with the overpressure. The instrument was located such that the shock had travelled 800 feet over land immediately before reaching the gage. On Shots 4 and 5, meaasurements of dynamic pressures by the gage group were higher than values calculated from the measured overpressures; the records showed peculiar 106