of a Surface Detonated Nuclear Explosion” (WT-922,, Bureau of Ordnance, Department of the Navy, Jar-s teriilly increased, and the reliability of crater- prediction methods formulated therefrom was im~ proved. Based on the crater data from this project, Murphy, LCDR, USN, Project Officer. as well as a considerable amount of high-explosive and other nuclear crater data, the handbook “Cruatering From Atomic Weapons,’’ AFSWP-514, dated 29 June 1956, was Subsequently preparcd. The specific objective was to determine the effets of a surface detonated nuclear device on u pianteu sea minefield. Operational considerations limited participatiun of the project to Shot +4. The sea minefield in this test was laid in seven rows disposed at ranges from 2,000 to 13,900 fect Project 3.3 ‘Blast Effecta on the Tree Stand” (WT-921), U. S. Forest Service; W. L. Fons, Proj- from site zero. ect Officer. level Mk 6-0 mines in Row 4, the mines 50! a given The objectives were to: Except for Row 6 and twu surface- row were laid on the bottom and were linked together (1) determine blast dam- by 230 feet of doubled 1'4-inch cable exteading '2- age to trees in terms of stand breakaye, branch breakage, and defoliation, where effects are influenced tween mines. Each string so formed was anchored by their location in a natural tree stand; (2) determine by a 2,000-pound cast-iron block attached to wie string the effects of natural forest coverage on attcnuation by 1,000 feet of doubled cable. Heavy woorcien bhucys ‘were used to mark the locations of the anchor blocks. of the shock wave, in terms of peak overpressure and peak dynamic pressure; and (3) obtain individual tree-breakage data in the region of long positive- In Row 6 the mines were moored individually at depths of 30, 50, and 125 feet. Postshot recovery was done by reeling in the phase duration, in order to substantiate the basis for breakage anu blow-down prediction. strings of each row. In some instances this proc: lure resulted in case damage to the mines. The availability of the natural tree stands in rela- tion to detonation sites and expecte] yields limited this project to observations of natural tree stands on Uncie, Victor, and William Islands >f Bikini Atcll. Participation wag originally planned cntly for Shot 3, but data was also obtained from Shot 1 becauseof its unexpectedly high yield. The moorce mines in Row 6 and the string of Row 1 were lost ini never reccvered. In addition, mines closest to site zero that were recovered about 24 hours after snot time were radioactive, with an exposure rate of i0 r/hr. Although only a limited number of mines were ex- posed, it was concluded that a surface-detcnated nu- The principal tree types available for observation were: (1) Pisenia, a tree resembling the American beech tree; (2) Coconut Paim; (3) Tournefurtia, a clear weapon was not an efficient method for run Jicid clearance. , broadleaf species of large shrub-type which were chiefly under cover in Pisonia and Palm groves; and Project 3.5 “Blast Effect on Miscellaneous Siruc- (4) Scaevola, a large, low, green bush-type species. tures”(WT-901), Armed Forces Special Weapons Project; Wayne J. Christensen, LCDR, CEC, US>, Instrumentation consisted of snubber tree gages Project Officer. (a simple device for measuring maximum tree deflec- tion), a limited numberof self-recorcing, static, overpressure-versus-time and dynamic-pressureversus-time gages installed by Project 1.2b, and extensive preshot and postshot photography. Static- The objective was to documcnt damage inflicted by Shot 1 on structures that had been crected fer utilitarian purposes in connection with the test operations. This project was not in the original program, Dut the unexpected structural damage which resulted from Shot 1—with its yield of 15 Mt approximately ‘hree breakage tests cf representative trees were also made prior to the shot. The distances involved were from 62,000 to 76,000 feet from ground zero for the inadvertent participation on Shot 1 and from 3,000 to 31,800 feet for Shot 3. Ground-level pressure measurements 2,000 feet into a tree stand substantiated the Upshot-Knothole conclusion of no attenuation in peak overpressure. Since for the first time natural tree stands were subjected to a nuclear blast, the breakage prediction on Amer- ican and European broadleaf tree stands can now be made with a fair degree of confilence. Observed damage from two devices of different yields compare times that predicted—-warranted documentation of all the data possible about structural blas: damage from high-yield detonations. It became evident from this survey that the effective letha] range to a light wood-frame building wag amazingly great for a high-yield nuclear binst. This type of structure was damaged severely beyond a range of 14.5 miles. Even reinforced-concrete shelter-type structures as far as 4-mile range which were exposed directly to the blast were vulnerable. The islands of Oboe and Tare were thesite of a camp for approximately 1,000 persons, the shipping center for all inter- and intra-atoll shipping, the favorably with TM 23-200 (Reference 7) isodamage curves prepared for broadleaf stands. Damage in broadleaf stands is principally limb breakage and de-~ foliation, with occasional breakage of the main stem base for all construction operations in the atoll, the site for one of the later detonations of the test series, and the site of an air strip with minimum aircraft or uprooting. servicing facilities. Project 3.4 “Sea Minefield Neutralization by Means 112 It had been intended to continue to base operations on this island up to the last shot,