and amplitudes was uncertain. The air-induced signal propagated with a velocity of the air-blast wave, radiation cxposure is of little significance at distance; beyond 16,900 fect for surface bursty of yieias up to 15 Mt, .4) the decay vate is affected by the capture decreasing with increasing ground range, while the ground~transmitted shock propagated with a velocity of about 8,700 ft/sec. The determination of velocities products of the thermonuclear devices fired, and (3, the .nitial-gamma- radiation spectr.m for Shot 3 ap- and displacements by means of integration of the acceleration traces was not aftempted—the precision of the data was too poor to support such an analysis. pears harder thanthat obtained from fission devices. Project 1.8 “Dynamic Pressure Investigation” (WT-911), Ballistic Research Laboratories; E. J. Bryant, Project Officer The objective was to evaluate dynamic pressure as a damage parameter. in addition, some information seegarding the damage effect of long positive-phase duration was to be obtained. A total of 27 jeeps were exposed on Shots 3 and 6, the ground ranges were Signal Corps Engineering Laborutorics: Peter Brown, Project 22 “Gamma Rate versus Time” (WT-913), Pro;ect Officer. The objective was to document the gamm -radiation rate from the detonation of high-v'eld thermun:.clear devices. Two types of measurements were .nade: (1) initial-gamma rate versus timne at various fixed distance; from ground zero and, .n particular, the effect on the initial-gamma rate due to the passage of the shock from ground zero through the detector selected to obtain dynamic pressures comparable in magnitude to those acting upon the jeeps experiencing light to severe damcge on Shot 10, Upshot~Knothole. station, and (2) gamma-radiation time-intensity datz, which gives information on fallout rate of arrival anJ gamma-field radiation-decay rate during the period up to 36 hours after the detonation Ali measurements were made using scintillation detector techniques. The instrument stations were self-contained and required no outside facilities other The yield of Shot 3 was too low to give any significant results. The limited results of Shot 6 were not conclusive enough to permit an evaluation of dynamic pressure as a damage parameter to be applied to the jeep as a drag-sensitive target. Further, the results did not allow a separation of the effect of dynamic than timing signals to turn the stations on at a pre- pressure on damage from the effect of the long positive-phase duration. Based on a comparison of Castle and Upahot-Knothole data, Project 1.: proposed cube-root scaling for vehicle damage. determined time prior to the detonation. The expanding fireball an the passage of the shock However, a composite AFSWP report, TAR 514 “Damage to MIltary Field Equipment from Nuclear Bursts” was subsequently prepared which included the Castle, UpshotKnothole, and all other nuclear-test data. This front from ground zero thraugh the detector station had a marked effect on the initial-gamma rale and hence on the integrated expesure. In general, the initfal-gamuna rate decreased relatively slowly after report concluded that wé scaling was the most ap- reaching its peak value immediateiy after the detonation, began to rise siow!y, and then rose rapidly to the same value as the peak received at time of dein- propriate method for predicting damage to military field equipment. rate decreased rapidly toward zero value. nation. After reaching the second peak value, the The initial decrease in rate was attributed to the natural decay of the fission products, the slow rise PROGRAM 2: NUCLEAR RADIATION STUDIES Project 2.1 “Gamma Radiation Dosimetry” (WT-912), Signal Corps Engineering Laboratory; Robert Dempsey, Major, USA, Project Officer. The objectives were to documentthe in‘tial and residual gamma radiation exposure from high-yield bursts in order to asaist in the evaluation of the resultant gamma radiation hazards, provide data for the correlation of results for other projects, and extend the use of gamma-radtation dosimetry techniques to higher gamma-exposure ranges. Radiation exposure from a series of nuclear detonations was measured by photographic films and chemical-dosimetry vials of various sensitivity ranges. The film and chemical detectors were placed in protective detector stations at positions from 1 to 15 miles from ground zero for Shots 1, 2, 3, 4, and 6. Calibrated exposure range of dosimeters used extended from 1 to 60,000 r. In general, it was concluded that (1) initial-gamma- 108 to the expanding of the freball and approach of the shock front, and the rapid rise to the passage of the shock front through the detector station. These effects were also evidenced in the integrated exposure prior and subsequent to the arrivai of the shock front. The average velocity of the shock front was found to vary with distance from ground zero, decreasing | rapidly with distance. The decay exponent from the residual contamination and fallout was found to vary with distance and direction from ground zero. In general, the decay exponent appeared to increase rather abruptly several hours after the detonation. This can be attributed to the presence of shurt-lived {sotcpes in the residua! contamination and fallout. In general, it was indicated that the magnitude of gamma radiation emitted from high-yield thermonuclear devices is considerably lower than the predictions in the Super Effects Handbook (Reference 11). At approximately 2,390-yard range, this handbook indicates the exposure from initi.’ gamma from a