field phase ut the operation to include shot Quince, and this participation is covered in the portion of this report relating to that detonation. To make the necessary measurements, threshold activation and fission detectors were exposed at various distances from the Yellowwood and Walnut zero points. These detectors included ince land masses of sufficient size were not available for displaying tNe detectors at desired distances, a buoy line was used. The line extended from 917 to 4100 yd from Ground Zero for both shots. Due to the radiological! situation that existed after these detona- tions, recovery could not be effected until D+1 day. As a result, only limited neutron flux and dose data were obtained. Early results indicate that the neutron dose for shot Yellowwood was lower than predicted by a factor of 2.3 and the Walnut dose was low by a factor of 2.0. Fallout Sampling. The objectives were to determine the relative con- tribution of certain isotopes to both local and world-wide fallout and to use this information, if possible, to determine the fraction of total bomb debris deposited in the local area. The project was divided into two separate efforts: (1) the collection of early cloud samples by means of newly developed rocket samplers, and (2) the collection of residual cloud samples and fallout debris by aircraft. The rocket sampling was to have been accomplished with rockets de- veloped by UCRL Project 21.3. Gas and particulate sampling of the residual cloud was accomplished by B-57D aircraft under the technical supervision of LASL personnel. Fallout samples were collected at various times after the detonation, based on predictions furnished by the Fallout Prediction Unit. These collections were made at an altitude of 1000 ft by WB-50 aircraft. The fallout collection was supervised by personnel of the U.S. Naval Radiological Defense Laboratory. The project participated during shots Koa, Walnut, and Oak, as it was desired to obtain a comparison between the fallout from land surface and water surface detonations in the megaton range. Because of various technical problems, satisfactory rocket samples were not collected from shots Koa and Walnut, and this portion of the project was canceled prior to Oak. Successful B-57D and WB-50 samplings of the Koa fallout were made; however, early analysis of the samples indicated they had been contaminated by debris from shot Fir, fired the previous day at Bikini. For this reason, project participation was extended to include Oak. Successful sampling was accomplished during Walnut and Oak. Collected samples were returned to the continental laboratories for analysis, and the resultant data were not available at the time this report was written. Program 3, Structures and Equipment The objective of this program was to provide information on the effects of nuclear bursts on ship structures and equipment, and on various land structures, under certain conditions that had not been heretofore investigated. Five of the eight projects were concerned with the response of ship structures and equipment to underwater bursts, and three were concerned with the response of land structures to air blast. Prior to Operation Hardtack a series of tests was run employing HE charges against the destroyer DD-592 off Santa Cruz Island, Calif., in January 1958. A series of four large, specially shaped (tapered) HE charges 29 At Wi/HC ey