terngl ballast tanks ruptured and all were seriously dished, resulting in some loss“@&buoyancy. The SSK-3 was submerged at periscope depth and operated by its crew at 18,000 ft from Wahoo surface zero. In Umbrella, the SSK-3 was unmanned and located bow-on at a range of 2900 ft. No permanent hull deformations occurred from either shot. The following preliminary conclusions may be made: 1..,A-range for moderate hull damage to a submarine-like Squaw under Umbrella conditions is 1600 f at a depth of 50 ff. 2. A conservatively safe range for the SSK-3 hull under Wahoo condi- 3. The SSK-S under Umbrella conditions at 2900 ft range and at a. tions is 7000 ft at a depth of 50 ft; later analysis will permit determination of the minimum safe range. depth of 50 feet was shown to be well beyond the minimum safe range for hull damage. Failure criteria for prefabricated, corrugated steel, flexible arch-shell structures confined within non-drag-sensitive earthwork configurations of coral sand simulating partially underground structures was studied. Three structures were tested in the 80- to 180-psi peak overpressure region from a 1.4 Mt surface shot to determine empirically the response of such structures. A fourth structure was tested in the 90-psi peak overpressure region from a 17-kt surface shot to determine the effects of short-duration blast loading on a similar structure and environment. The 25-ft span by 48-ft 10-gage arch-shell structure subjected to 90 psi peak overpressure partially collapsed on the side away from ground zero. The collapse apparently was initiated by bearing failure of the shell pilates at a bolted horizontal seam approximately 5 ft above floor level on the collapsed side of the structure. The following results were noted on the other three structures: 1. A 25-ft span structure and the 38-ft span by 40-ft l-gage archshell structure, subjected, respectively, to 78 and 100 psi peak overpressure from shot Koa suffered a complete collapse symmetrically about the crown. A third 25-ft span structure subjected to 180 psi peak overpressure collapsed compietely. The dynamic behavior of deep (thick) reinforced concrete slabs in the high overpressure regions of 175 to 600 psi was studied to provide the basis for establishing design criteria for massive reinforced concrete structures under blast loads. Thirty one-way and 15 two-way slabs mounted flush with the ground surface were tested. The clear span was 6 feet and the ratios of depth to span varied from 0.15 to 0.78. Because of excessive postshot radiation at the slab locations, data recovery has not been completed. However, preliminary results indicate that the resistance of the slabs to high blast pressures was considerably greater than expected. Program 5, Aircraft Structures The Air Force was concerned with determining the structural response of a B-52D aircraft subjected to side loads. This determination had as an ultimate objective the definition of the delivery capability of the aircraft for multiple delivery tactics. A range of angles with respect to ground zero from 35° head-on to 180° tail-to in azimuth, including three different elevation angles, were utilized in verifying the analysis and predictions. It was concluded that the data obtained were sufficient to verify the method of analysis used to predict structural side loads from which the nuclear weapon delivery $1